LEE- Elektronik Mühendisliği Lisansüstü Programı

Bu topluluk için Kalıcı Uri

http://hdl.handle.net/11527/19263

Gözat

Design and implementation of a novel physically unclonable function with a new cellular automata model

(Fen Bilimleri Enstitüsü, 2020) Göncü, Emre ; Yalçın, Müştak Erhan ; 657021 ; Elektronik ve Haberleşme Mühendisliği Ana Bilim Dalı

The number of devices in network increases continuously by the Internet of things (IoT) paradigm. It is expected that there will be over 25 billion devices connected to the internet, by 2025. Furthermore, IoT applications can be encountered in almost every part of our lives such as at homes, in vehicles, in human bodies. Obviously, most of those devices store sensitive data. In addition, because of the rapid increase of e-business practices, the devices realizing secure transactions of huge sensitive data are essential. Therefore, security and trustworthy of that kind of devices become more and more important. Secure transactions are realized with strong cryptographic systems. True Random Number Generators (TRNG) are essential for these systems in order to source the inputs such as keys, initialization vectors and challenges. Statistical quality of the TRNG is one of the metrics determining the security level of the system. Therefore, designing and implementing a TRNG of high quality is vital for a strong cryptographic system. Nowadays, threats of counterfeit integrated circuits (IC) arise around the world. Therefore, Intellectual Property (IP) protection of the hardware designs is one of the major challenges of IC designers. They want their hardware to run on a limited number of ICs because of commercial reasons. Physical Unclonable Functions (PUF) are another security primitives extracting the unique identity of devices from the physical characteristics. In fact, this identity is a trust anchor in higher-level security architectures. Therefore, they can answer the security challenges mentioned above. Cellular Automata (CA) are discrete dynamical systems used in many different fields like modelling, pseudo-random generation, image processing, \textit{etc.}. Since standard CA are deterministic systems, it is not possible to obtain random bit sequence at the output. However, a new CA model proposed in the thesis makes it possible by adding some physical noises to the model. Introduced model is also realized on FPGA. It is empirically proved in thesis that the output of the system is random. Employing the randomness of the new CA model, a TRNG and a PUF design are proposed in order to address the solutions for given problems above. The proposed TRNG, without any post-processing block, passes all the statistical tests provided by NIST. Furthermore, it has a higher speed regarding the other TRNG implementation on FPGAs given in the literature. PUF design is also promising by the terms of security and reliability regarding the other PUF implementations on FPGA in the literature. Finally, at the end of the thesis, a novel Application Specific Integrated Circuit (ASIC) implementation of Advanced Encryption Standard (AES) block cipher is introduced. The AES hardware is asynchronous in order to have reduced power consumption and throughput improvements regarding the other AES hardware realizations given in the literature. Furthermore, the IC is fabricated using TSMC-65 nm standard cells.
Spintronic devices for wireless communication,memory, and analog applications

( 2020) Atasoyu, Mesut ; Özoğuz, İsmail Serdar ; 629126 ; Elektrik ve Elektronik Mühendisliği ; Electrical and Electronics Engineering

Son on yılda spintronik elemanlar, bellek, analog devre tasarımında, ve kablosuz iletişim alanlarındaki güncel uygulamalarda önemli sınırlamaları olan CMOS teknolojisinin yerini alabilecek aday bir teknoloji olarak karşımıza çıkmıştır. Spintronik elemanın manyetik durumun geleneksel elemanlara göre çok daha az enerji ile değiştirilebilir olmasının hız verdiği araştırmalarla, bu elemanın yukarıdaki uygulamalarda nasıl kullanılabileceğini gösteren yeni yöntemler geliştirilmiştir. Ferromagnetin spin-tork anahtarlaması, bellek, analog ve kablosuz iletişim uygulamaları için çok yararlı bir özellik olarak kabul edilmektedir. Bununla birlikte, hala spin-tork cihazlarının bu uygulamalar için daha etkin nasıl kullanılabileceğini gösteren yeni araştırmalara ihtiyaç bulunmaktadır. Literatürde spintronik elemanların bellek, ayarlanabilir direnç, ve osilatör uygulamalarında, manyetik tünel jonksiyonun spin tork anahtarlama modeli için çeşitli modeller ve devre tasarım teknikleri önerilmiştir. Bu tezde, bellek, analog ve kablosuz iletişim alanlarına yönelik olarak spintronik cihazların matematiksel modellemesi ve olası uygulamaları incelenmiştir. Temel olarak bu uygulamalarda, ofset iptali, BER performansının iyileştirilmesi ve faz gürültüsünün azaltılması için yeni devre teknikleri önerilmiştir. Bu tezde sunulan çalışmalar özet olarak: Bölüm 1 Bu tezin motivasyonu ve araştırma katkıları bu kısımda derlenmiştir. Bölüm 2 Spintronik aygıtların iyi anlaşılması için, manyetik teoremler açıklanmıştır. Spintronik aygıtların kapsamlı bir şekilde anlaşılması, manyetik malzemelerin fiziksel prensipleri hakkında kapsamlı bir bilgiye dayanır. Bu bölümde, elektromanyetik teoremlerin önemli sonuçlarının bir özetini ve bu tür aygıtların anahtarlama sistemleri için ilgili manyetik teorilerin bir özeti sunulmuştur. Sonuç olarak, bu manyetik bilgi temeli üzerine spintronik aygıtların modellenmesi incelenmiştir. Bölüm 3: analog devre uygulaması Yeni nesil devre elemanı olarak memristörler bir analog uygulamada ilk önce değişken kazan kuvvetlendirici yapısında kullanılmıştır. Ancak memristörleri düşük gerilim seviyelerinde çalıştırmak zordur. Spintronik devre elemanları düşük gerilim seviyelerinde çalıştırılabilir ve ilk uygulama olarak bir işlemsel geçişiletkenliği kuvvetlendirici (OTA) yapısında yerleşme zamanı kompanzasyonu için ayarlanabilir direnç olarak kullanılmıştır. Çünkü spintronik aygıtların çoklu hücresel fabrikasyonu düşük maliyetli olduğu ve CMOS teknolojisine entegrasyonu tasarım alanı verimliliği sağladığı için, analog uygulamalarda tercih edilmektedir. Bu bölümde spintronik aygıtlar pratik programlanabilir direnç olarak bir analog uygulama yapısında gerçeklenmiştir. Bu aygıtların programlanabilir direnç uygulaması, spin tork anahtarlama mekanizması yardımıyla gerçekleştirilir. Ayrıca, bir spintronik aygıtın direnci uygulanan darbe gerilim kaynağının darbe genişliğine ve uygulanan kutuplama akımın yönüne bağlıdır. Bu amaçlanan ayarlanabilir direnç yapısı karşılaştırıcı yapısında ön kuvvetlendiri ofsetinin azaltılması için uygulanmıştır. Çok hücreli spintronik aygıtlarin üretimi ucuz olduğundan, bu ofset azaltma yöntemi düşük maliyetli bir tasarımdır. Bu amaçlanan programlanabilir direnç yapısında, spintronik aygıtların direnç değeri sapmalarını azaltmak için bu aygıtlar birbirlerine seri olarak bağlanmıştır. Bölüm 4: bellek uygulaması Modern yüksek hızlı sayısal sistemlerde yonga önbelleği olarak statik rastgele erişim belleği (SRAM) kullanılır. Bununla birlikte, CMOS teknoloji nodu küçüldükçe, SRAM'ın statik enerji tüketimi artar. Yeni teknoloji bellek elemanları, SRAM'ın yerini almak için geliştirilmektedir. Bunlar arasında rastgele manyetik bellek elemanları (STT-MRAM) özellikle caziptir. STT-MRAM' in avantajları arasında: CMOS tasarım uyumluluğu, hızlı okuma ve yazma işlevselliği, ve dayanıklılığı yüksektir. Bir STT-MRAM'in ana bellek işlemleri yazma ve okumadır. Bu işlemler arasında bellek hücresi akımı açısından bir ödünleşim vardır. Yazma işlemleri için daha düşük hücre akımları tercih edilir, ancak okuma işlemleri için daha yüksek hücre akımları tercih edilir. Aygıt geliştirme seviyesindeki araştırmalar, manyetik tünel jonksionu (MTJ) anahtarlama akımını yazma operasyonlarında azaltmayı ve devre seviyesindeki araştırmalar bit hata oranı (BER) performansını bu bellek elemanının okuma operasyonlarında arttırmayı amaçlamaktadır. Bu tezde bellek uygulamasında, STT-MRAM yapısında okuma işlemlerini iyileştirmek için çeşitli devre tasarım teknikleri sunulmuştur. Akım algılama kuvvetlendiricisine ve gerilim algılama kuvvetlendiricisine dayanan yaygın olarak kullanılan iki algılama şeması karşılaştırılmıştır. Düşük dirençli alanlarda yüksek tünelleme direnci (TMR) sağlayan MTJ ile yapılandırılmış STT-MRAM için tasarlanmış sezme şemalarının temel sınırlamaları araştırılmıştır. Sonuç olarak, tek bir referans MTJ hücresi ile önerilen algılama şeması, yüksek hızlı ve düşük güçlü STT-MRAM okuma işlemleri için iyi bir çözüm sunmaktadır. Önerilen algılama şeması, veri ve referans hücrelerinin direnç varyasyonlarına ve latch deki parazitik kapasitanslara daha az duyarlıdır. Önerilen tasarım, literatürdeki benzerlerine kıyasla hızlı okuma, BER performansı, ve güç tüketimini açısından daha iyi bir çözüm sunmaktadır. Bölüm 5: kablosuz haberleşme uygulaması Nano aygıt araştırmaları, frekans sentezleyicilerinin indükleyici olmadan tasarımı açısından büyük önem taşımaktadır. Araştırmacılar, yeni nesil frekans sentezleyici için yeni grafen tabanlı cihazlar ve spintronik cihaz teknolojileri üzerinde aygıt araştırmalarına ağırlık vermektedirler. Spintronik osilatör teknolojisindeki son gelişmeler, küçük çip boyutu (100 nm veya daha küçük çaplı), kompaktlığı, CMOS işlem uyumluluğu, yüksek çalışma frekansları, gelecekteki kablosuz iletişim ve ayrıca milimetre kablosuz iletişiminde yani 65 GHz'in üzerinde frekanslarda çalışabiliyor olması nedeniyle bu osilatör teknolojisi önem arzetmektedir. Çoklu RF vericileri özellikle VCO'lar yapılarındaki LC tabanlı osilatörler nedeniyle çok fazla alan kaplamaktadırlar. Bu nedenle spintronik osilatörlerin çoklu RF vericisinde uygulaması, LC tabanlı bir VCO'dan kompakt alan tasarım açısından daha caziptir. Bununla birlikte, STO'ların bazı ana dezavantajları vardır. Bunlar, düşük çıkış gücü, düşük frekans çözünürlüğü ve doğrusal olmayan genlik-faz kuplajıdır. Bu aygıt araştırmalarında, bu dezavantajların çözümüne odaklanılmıştır. Kablosuz uygulamada, spintronik osilatör tabanlı frekans sentezleyici yapısı tasarlanmıştır. Bu tezde geliştirilen devre teknikleri spintronik osilatörün spektral çözünürlüğünü geliştirmeye odaklanmıştır. Sonuç olarak, spintronik osilatörün spektral çözünürlüğü iyileştirilmiştir. Entegre devre yaklaşımındaki spintronik osilatörün faz gürültü seviyeleri, bu araştırma alanındaki gelecekteki çalışmalar için simülasyon sonuçlarıyla belirlenmiştir.
Derin obje sezicilerle tümleştirilmiş bayesçi filtreleme ile videoda obje izleme

(Lisansüstü Eğitim Enstitüsü, 2021) Gürkan Gölcük, Filiz ; Günsel Kalyoncu, Bilge ; 691735 ; Elektronik ve Haberleşme Mühendisliği

Güvenlik, hareket ve aktivite tanıma, robotik uygulamaları ve daha birçok uygulamada gerek duyulan obje izleme, belirlenen bir veya daha fazla hedef objenin konumunun video boyunca kestirilmesi olarak tanımlanır. Uzun yıllardır bu alanda yapılan çalışmalar, izleme başarımını arttırmanın yanı sıra, örtüşme, deformasyon, ölçek ve görünüm değişimi gibi izlemeyi zorlaştırıcı etkilere karşı gürbüz algoritmalar geliştirmeyi amaçlamaktadır. Tez çalışması kapsamında, üretici ve ayırıcı yöntemlerin entegre edilmesine olanak sağlayan obje-sezme-ile-obje-izleme (tracking-by- detection - TBD) yaklaşımı altında, IDPF-RP, L1DPF-M ve TDIOT olarak adlandırılan, üç farklı obje izleyici önerilmiştir. Önerilen tüm izleyicilerde, tek obje izleme problemi üzerinde yoğunlaşılmakta ve objenin son konumu, Bayesci filtreleme tabanlı bir obje izleyici bir derin obje sezici ile tümleştirilerek kestirilmektedir. Derin obje sezici olarak yüksek lokalizayon doğruluğuna sahip Mask R-CNN sezici kullanılırken, Bayesçi filtrelemede hedef obje modellemede başarılı olduğu gösterilen renk-tabanlı parçacık filtreleme ve seyrek parçacık filtreleme kullanılmaktadır. İzleyicilerin bir diğer ortak noktası, kullanılan derin obje sezicinin izleme amacıyla yeniden eğitilmesini, ya da izleyicinin uçtan-uca yeniden eğitimini gerektirmemeleridir. Böylelikle etiketlenmiş izleme verisi olmaması durumunda çalışabilen, çevrim dışı eğitim yükünü en aza indiren, çok farklı derin obje sezicilerin farklı omurga mimarileri ile tümleştirilebilmesine olanak sağlayan obje izleyicilerin gerçeklenmesi hedeflenmiştir. IDPF-RP (Interleaving deep learning and particle filtering by region proposal suppression), VRCPF obje izleyici ile senkronize çalışan Mask R-CNN obje sezici kararlarını tümleştiren yeni bir karar tümleştirme mekanizması sunmakta, bu sayede objenin son konumu, izleyici ve sezici arasındaki karar birliğini enbüyükleyecek şekilde belirlenmektedir. IDPF-RP lokalizasyon hizalama katmanı (LH), Mask R-CNN sezicinin ölçek değişimlerine uyumluluk ve lokalizasyon doğruluğu avantajı ile VRCPF izleyicinin hedefe lokalize olma özelliğinden yararlanan bir tümleştirme gerçekler. Bu sayede izleme performansını doğrudan etkileyen aday obje BB'lerinin, içeriğe bağlı olarak değişen sayıda ve yüksek lokalizasyon doğruluğu ile örneklenmesi sağlanabilmekte, böylelikle izleme sürekliliği arttırılmaktadır. IDPF-RP, derin obje seziciden alınan geri besleme ile, hedef obje modelini güncelleyerek ölçek, ışıklılık ve görünüm değişimleri gibi obje izlemeyi zorlaştıran problemlere karşı gürbüzlüğü arttırmaktadır. Tez kapsamında önerilen bir diğer obje izleyici, L1DPF-M, Mask R-CNN derin obje sezici ve seyrek parçacık filtresini TBD yaklaşımı altında entegre eden yeni bir model sunmaktadır. Hedef obje modellemede kullanılan seyrek gösterim, derin obje sezicinin kılavuzluğunda güncellenerek, örtüşme, bakış-açısı değişimi gibi etmenlerden kaynaklanan obje görünüm değişikliklerine karşı gürbüzlük arttırılmaktadır. L1DPF-M, önerilen yeni PF gözlem modeli sayesinde, sezici ve izleyici arasında fikir birliğini ön plana çıkararak hedef objenin son konumunun daha doğru kestirilmesine olanak tanımaktadır. Bunun yanı sıra, L1DPF-M kapsamında önerilen yeni durum vektörü ile, obje hareketinin öteleme, dönme, ölçekleme ve kırpma olarak farklı komponentlerle modellenebilmesi bu sayede obje sınırlarının deforme BB'ler ile izlenebilmesi ve lokalizasyon doğruluğunun arttırılması sağlanmıştır. L1DPF-M, Mask R-CNN çıkışında elde edilen ve objeye piksel bazında erişim sağlayan bölütleme maskelerini kullanarak, izlemenin afin dönüşümlere gürbüzlüğünü arttırmaktadır. Tez kapsamında geliştirilen üçüncü obje izleyici, TDIOT, videodaki zamansal bilginin 3B CNN, LSTM ve benzeri mimariler kullanılmaksızın, işlem yükü çok arttırılmadan modele katılmasını amaçlamaktadır. IDPF-RP ve L1DPF-M den farklı olarak mimarisinde yalnızca PF izleyicinin parçacık örnekleme modülünü içerir ve hedefin son konumunun kestiriminde derin obje seziciye öncelik verir. Literatürdeki birçok derin izleyiciden farklı olarak, sezici eğitiminde kullanılan mimarinin izleme amacıyla transfer öğrenme ile yeniden eğitilmesini, ya da uçtan-uca yeniden eğitimini gerektirmez. Önerilen çıkarım mimarisinde Mask R-CNN aday bölge öneri katmanına eklenen parçacık örnekleyici, objenin geçmiş çerçevelerdeki konum bilgisini kullanarak, objeye uyumlu ölçek ve boyutlarda aday obje bölgelerinin önerilmesine olanak vermektedir. Öte yandan tepe katmanına eklenen "Benzerlik Eşleme" ve "Yerel Arama ve Eşleme" katmanları ile siyam benzerlik kriterine dayalı veri ilişkilendirme gerçeklenir. TDIOT obje izleyicinin obje giriş çıkışlarının da olduğu uzun süreli izleme isterlerini karşılaması amacıyla, yerel ikili örüntü tabanlı bir hedef-obje-doğrulama katmanı izleme mimarisine eklenmiş, uzun süreli izleme başarımının arttırıldığı gösterilmiştir. TDIOT doğrulama katmanının, insan, araba ve benzeri belirli objeler için eğitilmiş yeniden yakalama ağları ile değiştirilmesiyle, daha yüksek işlemsel karmaşıklığa karşın, obje doğrulama başarımının arttırılması olanaklıdır. Önerilen yöntemlerin başarımı literatürde sıklıkla kullanılan VOT ve VOT-LT veri tabanlarına ait videolar üzerinde raporlanmaktadır. Her üç yöntem için güncel izleyiciler ile karşılaştırmalı olarak sunulan izleme performansları, önerilen izleyicilerin lokalizasyon doğruluğunu önemli ölçüde arttırdığını göstermektedir. VOT2016 veri setine ait videolarda yapılan performans raporlamaları, IDPF-RP ve L1DPF-M ile güncel izleyicilere kıyasla sırasıyla \%7 ve \%6 daha yüksek başarım oranına (IoU-th=0.5) ulaşıldığını göstermektedir. Ayrıca, TDIOT ile lokalizasyon doğruluğunun (accuracy), VOT2016'nın en yüksek başarımlı izleyicisine göre \%3 oranında arttırıldığı, TDIOT-LT ile uzun süreli videolarda, literatür ile karşılaştırılabilir izleme performansına ulaşıldığı raporlanmaktadır. Bunun yanı sıra, izleme performansı her bir zorluk kategorisi için ayrı olarak analiz edilmiş ve önerilen izleyicilerin birçok zorluk durumunda izleme performansını arttırdığı gösterilmiştir. VOT2018 veri setine ait videolarda yapılan testler, IDPF-RP izleyicinin, ölçek değişimi içeren videolarda başarım oranını \%4, L1DPF-M izleyicinin, ışıklılık değişimi içeren videolarda başarım oranını \%5 oranında arttırdığını göstermektedir (IoU-th=0.5). Öte yandan, TDIOT obje izleyici, özellikle ışıklılık ve ölçek değişimine karşı gürbüzlüğü arttırarak, izleme doğruluğunu sırasıyla \%4 ve \%2 oranında iyileştirmektedir. TDIOT-LT ise bakış açısı değişiminin olduğu uzun süreli videolarda en yüksek izleme başarımına ulaşmaktadır.
Görüntü işlemede yama sıralama tabanlı yaklaşımlar

(Lisansüstü Eğitim Enstitüsü, 2021) Çolak, Özden ; Ekşioğlu, Ender Mete ; 692961 ; Elektronik ve Haberleşme Mühendisliği

Görüntülerde gürültünün en temel bozucu etki olması, gürültü gidermeyi görüntü işleme problemlerinin en önemlilerinden ve üzerinde en çok çalışılanlarından birisi haline getirmektedir. Bu tez çalışmasında öncelikle, literatüre yakın zamanda girmiş olan yama sıralama işlemi ve seyrekleştirici üç boyutlu dönüşümlerin ilk defa sunulan öncül bir birleşimi geliştirilmiştir. Sunulan yeni yaklaşımı kullanan yeni bir görüntü gürültüsü giderme algoritması geliştirilmiştir. Ayrıca tez çalışmaları kapsamında yama sıralama işleminin ve bilinen üstün başarımlı çevrimiçi sözlük öğrenme algoritmalarından olan RLS-DLA algoritmasının özgün bir birleşimi ile yeni bir yaklaşım geliştirilmiştir. Bu yeni yaklaşımı esas alan yeni bir gürültü giderme algoritması geliştirilmiştir. Böylelikle yama sıralama yaklaşımının kullanımının görüntü işleme uygulamaları arasında bu alanda da başarım performansına katkı sağladığı gösterilmiştir. Günümüz teknolojisinde dijital kameralar ve görüntüleme özelliğine sahip cep telefonları görüntü elde etmede kullanılan teknolojik cihazların başında gelir. Bu cihazlardaki dijital kameralar ile görüntü oluşturulurken hem görüntünün alındığı ortamdaki ışıktan kaynaklı hem de ilgili teknolojik cihazların elektronik donanımlarından kaynaklı gürültüler bozucu etki olarak görüntülere eklenirler. Bu gürültüleri birkaç ana başlık altında inceleyebilmek mümkündür. Dijital kameralar ile görüntüsü oluşturulacak objeden yansıyan ışık demetleri toplanıp elektriksel işarete dönüştürülürken çeşitli gürültüler meydana gelir. Bunlardan bir tanesi kameranın elektronik devresinde kullanım süresine bağlı olarak artan ısıl gürültüdür ve bu gürültünün şiddeti ihmal edilebilir derecede düşüktür. Görüntü oluşturma sürecinde ortaya çıkan bir diğer gürültü ise saçma gürültüsüdür. Bu gürültü, görüntüsü elde edilmek istenen nesneden yansıyan ışık demetlerinin kamera sensörlerine eşit şekilde saçılmamasından dolayı oluşur ve etkisi ihmal edilemeyecek kadar yüksektir. Bu sebepten dolayı kameralar ile elde edilen görüntüler mutlaka gürültülü olacaktır. Saçma gürültüsü Poisson dağılımına sahip olsa da kamera sensörüne çok fazla sayıda foton gelmesi durumunda bu dağılım Gauss dağılımının olasılık yoğunluk fonksiyonuna yakınsar ve böylece görüntülerdeki gürültünün Gauss dağılımlı olduğu varsayılır. Ayrıca kamera sensörlerinin her birinde yığınlanan foton sayısı birbirinden bağımsız olacağından dolayı görüntülerdeki gürültü uzaysal olarak ilintisiz olur. Sonuç olarak elde edilen görüntülerdeki gürültü sıfır ortalamalı, birbirinden bağımsız ve özdeş dağılmış Gauss olarak bir başka deyişle beyaz Gauss gürültüsü (white Gaussian noise-WGN) olarak kabul edilir. Son yıllarda seyreklik tabanlı işaret işleme oldukça aktif bir araştırma konusu olmuştur. Kötü koşullu ters problemlerin çözümünün doğrudan bulunamadığı pek çok uygulamada, çözüme olanak veren bir düzenleyici olarak seyreklik öncül bilgisi başarıyla kullanılmaktadır. Seyreklik düzenlemeli işaret gösterilimi probleminin çözümünde etkin yeni algoritmaların geliştirilmesi sayesinde, seyreklik odaklı işaret işleme ve sıkıştırılmış algılama yaygınlaşmakta ve kullanım alanları genişlemektedir. Seyrek işaret gösterilimini kullanan uygulamalar arasında görüntü işleme problemleri önemli yer tutmaktadır. Görüntülerde gürültü giderme seyrek işaret işlemedeki gelişmelerden önemli ölçüde faydalanmaktadır. Görüntü işleme literatüründe tüm görüntüyü tek seferde işleyen birçok çalışma sunulmuştur. Global görüntü işleme yaklaşımlarının baskın doğası gereği tüm görüntüyü bir seferde işlerken görüntüdeki yerel detaylar kaybolur. Bundan dolayı da işlenmiş görüntülerde bazı sahte periyodik desenler oluşabilir. Bu probleme engel olmak için görüntüyü kayan pencereler şeklinde ele alan yerel filtreler kullanılır. Bu sayede görüntünün tümü aynı anda işlenmektense yalnızca pencere boyutu kadarlık kısmı aynı anda işlenir ve sonuç olarak görüntüdeki yerel detaylar korunmuş olur. Bu yaklaşımda görüntünün her bir pencere boyutu kadarlık kısmı birbirinden ayrı olarak ele alınır ve çoğu zaman kayma miktarı örtüşmeli yamalar oluşturacak şekilde seçildiğinden bir pikselin birden fazla sayıda kestirimi oluşabilir. Dolayısıyla bir piksele uygulanan en son güncellemeden sonra daha eski kestirimlerdeki bilgiler kaybedilmiş olur. Yerel filtreler kullanılırken bir piksele ait son kestirim oluşturulurken o piksele ait her bir kestirimin ortalaması alınarak bu sorun giderilmiş olur. Doğal görüntülerdeki birçok piksel birbirine benzer olduğundan dolayı bu piksellerden oluşan küçük boyutlu yamaların da birbirine benzer olduğu varsayılır. Bu öz-benzerlik özelliğinin kullanımı ile görüntü işleme uygulamalarının temiz görüntünün dokusunu kestirme performansı önemli ölçüde artmıştır. Bundan dolayı bu performans artışından yararlanmak için birçok yama tabanlı gürültü giderme algoritmaları geliştirilmiştir. Bu performans artışının temelinde görüntünün farklı yamaları arasındaki ilişkiden doğan bilgileri kullanmak yatar. Yaroslavsky filtre, ikili filtre gibi piksel komşuluklarını kullanan klasik yerel filtrelerde bir referans yamanın merkezindeki pikselin yeni değeri kestirilirken bu pikseli çevreleyen pikselleri merkez alan yamalar kullanılır. Yerel metodların aksine yerel olmayan metodlarda ele alınan referans yamanın çevresinde olmasa dahi görüntünün belli bir komşuluğundaki diğer yamalarda kullanılır. Görüntülerde yerel olmayan fakat birbirine benzer olan yamaları bir arada işleyebilme yetisi performansta oldukça yüksek artış sağlar. Son yıllarda yama tabanlı metodların oldukça yeni sayılabilecek bir örneği olan yama sıralama yaklaşımı farklı görüntü işleme uygulamalarında kullanılmıştır. Bu yaklaşım bir görüntüdeki yamaların belli bir örtüşme miktarına göre çıkarılıp bir benzerlik kriterine göre art ardına sıralanmasına dayanır. Kullanılacak olan benzerlik kriteri olarak birçok farklı metrik vardır. Yine de en çok tercih edilen benzerlik kriteri Öklid uzaklığıdır. Birçok çalışmada referans bir yamaya benzer olan diğer yamaları arama işlemi belli bir alanda olacak şekilde kısıtlanmıştır. Yama sıralama yaklaşımında bir benzerlik kriterine göre benzer bulunan yamalar art ardına dizilerek bir 3B yama dizisi oluşturulur. Ardından elde edilen bu 3B yama dizisine basit bir 1B filtresi uygulanır. Literatüre son yıllarda girmiş olan ve performans olarak son teknoloji sayılan gürültü giderme algoritması BM3D (Block Matching-3D Transformation) sunulmuştur. Bu yöntemde seyrekleştirici 3B dönüşümlerin benzerliklerine göre gruplanmış yama gruplarına uygulanması önerilmiştir. Görüntüden çıkarılan her bir yama için bu referans yamaya benzeyen yamalardan oluşan bir grup oluşturulur. Bu yaklaşımdaki üstün seyrekleştirme gücü birbirine benzer olan 2B yamaların bir grupta biraraya getirilerek 3B yama dizisi oluşturulmasından gelir. Buradaki üçüncü boyut yamalar arasındaki benzerlik bilgisini taşır. Algoritma bu 3B yama dizisinin 3B dönüşümü, elde edilen dönüşüm katsayılarının dönüşüm bölgesinde eşiklenmesi ve ters dönüşüm işlemleri ile devam eder. Bu işlemler sonunda elde edilen ara kestirimi bir Wiener filtreleme adımında kullanarak gürültüsü giderilmiş görüntünün son kestirimi elde edilir. Burada Wiener filtreleme adımının kullanımı ile performansta önemli ölçüde gelişme sağlanmıştır. Fakat her bir yamanın benzerlerinin bulunup gruplandığı benzerlik araması adımı oldukça yüksek hesapsal karmaşıklığa sahiptir. Bu tez çalışmasında ilk olarak, yama sıralama ile seyrekleştirici dönüşümlerin birleştirilmesi ile yerel olmayan görüntü işleme için yeni bir yaklaşım geliştirilmiştir. Literatürdeki öncül çalışmalarda, sıralama sonrası yamalar üzerinde sıradan süzgeçleme işlemleri yapılarak gürültü giderilmesi önerilmiştir. Bu yeni yaklaşımda ise gürültü gidermede literatürde önerilen sıradan süzgeçleme yerine, 3B seyrekleştirici dönüşümlerin kullanılması önerilmiştir. Bu yaklaşımda, yama sıralamanın getirdiği yerel olmayan işlem yapma yetisi, 3B dönüşümlerin üstün seyrekleştirme gücüyle birleştirilmiştir. Yapılan çalışmalarda bu birleştirici yaklaşımın görüntü gürültüsü giderme uygulamasında öncül algoritmalara göre daha iyi sonuçlar verdiği görülmüştür. Ayrıca bu tez çalışmaları kapsamında yama sıralama işlemi bir çevrimiçi sözlük öğrenme yaklaşımına adapte edilerek yeni bir gürültü giderme algoritması daha geliştirilmiştir. Literatürde sunulan çoğu çalışmada çevrimiçi sözlük öğrenme algoritmaları gürültü giderme problemine genellikle daha yüksek performans sergilediğinden dolayı yamalar üzerinden uygulanmıştır. Bu çalışmalarda yamalar ele alınırken görüntü içerisindeki doğal sıraları esas alınmıştır. Bu tez çalışmasında önerilen yeni yaklaşımda ise, yamaların görüntüdeki konumlarından gelen doğal sırasından ziyade bir kısıta göre sıralanmasından elde edilen yeni bir sıralama esas alınarak özgün bir çevrimiçi sözlük öğrenme gerçekleştirilmiştir. Önerilen bu algoritmadaki bir diğer yenilik ise sözlük öğrenme işlemi ile yamaların gürültü giderme işleminin eşzamanlı olarak gerçekleştirilmesidir. Böylelikle, öğrenilen sözlüğün yerel yamalara daha iyi adapte olması sağlanmış ve bu yaklaşımın görüntü gürültüsü gidermede daha iyi sonuçlar elde ettiği gösterilmiştir.
Approximate artificial neural network hardware aware synthesis tool

(Lisansüstü Eğitim Enstitüsü, 2021) Nojehdeh, Mohammadreza Esmali ; Altun, Mustafa ; 692582 ; Elektronik ve Haberleşme Mühendisliği

In the previous decade, artificial neural networks (ANNS) have attracted considerable attention from researchers in many areas and have become a favorite method; from business to aerospace applications. We live in the information age where this information feeds artificial intelligence (AI). According to Forbes' estimate, over the last two years alone 90 percent of the data in the world was generated. At first glance, processing more information may seem like a dissipation of more power in central processing units(CPUs) and graphic processing units (GPUs) or spending more time to obtain the results, but for the portable systems due to limitations in battery capacity, power, and hardware area limitations, different concerns emerge. For example, less consumption of energy is vital to extend the battery supporting time for mobile devices. The problem starts to be bold when software engineers regardless of the hardware sources (especially for portable devices) develop different ANNs architecture, where they intend to achieve a network with the best performances. Similarly, hardware engineers' AI knowledge is limited and any change within hardware design in lack of this knowledge may yield a catastrophic defect in the expected performance. As a result, this uninformed state yields a gap between the hardware and software sides of ANNs. The emerged gap provides a pitch to hardware and software researchers to play their best performance, where more information about the rival side makes their performance more eye-catching. By obtaining this gap, the co-design method or hardware-aware training methods become prevalent recently. The object of this dissertation is also to develop a methodology to realize the ANNs with minimum hardware cost by regarding the software performance. Limitation in hardware cost, consumed energy, and dissipated power for devices leads designers to find new architectures and approaches. Approximate computing is one of them, where this method is an useful technique for error essence systems. By leveraging the approximate level, a trade-off between the output accuracy and hardware cost is attainable. For example, assume a 1-bit exact adder costs 18 transistors, and by removing 3 transistors, a new approximate adder by 15 transistors is achievable, but the new approximate adder generates inexact results when the input is $(0,0)$, and suppose that the results for the rest set of the inputs$((0,1),(1,0),(1,1))$ are correct. Therefore, the approximate adder saves 3 transistors at the cost of 1 inexact result. Generally, approximate computing is apple of designers' eye in applications with error tolerance capability, consequently, error tolerance inherence of ANNs nominates approximate computing as a potential method to reduce the hardware complexity of ANNs. Since multipliers and adders are fundamental building blocks of ANNs, in this thesis, by introducing novel approximate multipliers and adders we replace them with exact adders and multipliers. As mentioned earlier, approximate computing is a trade-off between accuracy and hardware cost, to adjust this trade-off, we synthesized the proposed approximate blocks based on the desired error metric. Also, we proposed an equation to calculate the mean absolute error of the introduced approximate multiplier and adders. Based on our best knowledge, the proposed approximate blocks are the only ones which are synthesized based on the mean error value. In next step, we introduced a new error metric called the approximate level to evaluate the performance of the proposed approximate blocks in ANNs. On the other hand, ANNs are made up of a lot of multipliers and adders, where the search space for the best combination of these blocks grows with the increase of bit-width or neuron numbers. To tackle this problem and by exploiting the proposed error metric, we introduce a new search algorithm to find the appropriate combination of the approximate and exact versions of the arithmetic blocks by taking into account the expected accuracy of ANNs. Also, in this thesis we realized ANNs under different synthesis techniques to obtain the pros and cons of each approach. Since the parallel architecture requires a large area we considered the time-multiplexed architecture as the main architecture method, where computing resources are re-used in the multiply-accumulate (MAC) blocks. As an application, the MNIST and Pen-digit database are considered. To examine the efficiency of the proposed method, various architectures and structures of ANNs are realized. Our experimental results show that exploiting the proposed approximate multipliers yields smaller area and power consumption compared to those designed using previously proposed prominent approximate multipliers. Also, according to these results, concurrent use of approximate multipliers and adders provides remarkable results in terms of hardware cost, where we obtain $60\%$ and $40\%$ reduction in energy consumption and occupied area of the ANN design with the same or better hardware accuracy compared to the exact adders and multipliers. To demonstrate the proposed method's scalability, we propose an efficient method to realize a convolution layer of convolution neural networks (CNNs). Inspired by the fully-connected neural network architecture, we introduce an efficient computation approach to implement convolution operations.
Embedded vision system designed on a heterogeneous computing platform and applied to semen analysis

(Lisansüstü Eğitim Enstitüsü, 2021) Şavkay, Osman Levent ; Yalçın, Müştak Erhan ; 709922 ; Elektronik ve Haberleşme Mühendisliği

Image and video inspections in the medical field require intelligent systems in addition to microscopes for more accurate and detailed analyses. In this study, a reliable, reconfigurable, and compact intelligent analyzer system is proposed using a hybrid platform comprising a field programmable gate array (FPGA) and central processing unit (CPU) as the embedded video processing system. Computer assisted semen analysis (CASA) is then developed as an application on the proposed system. The developed system architecture can also be utilized in biological imaging and video applications, which require accurate and detailed analysis. Relevant semen analysis algorithms were constructed specially for the proposed architecture; however, the algorithms may also be used with similar existing embedded system platforms and newly developed hardware. As the speeds and performances of CPUs have approached their technological limits, a newer trend has evolved toward parallel computing; more recently, the use of heterogeneous computing platforms have also increased as they have attracted the interest of scientists and system developers owing to their operating performances. They surpass conventional general-purpose CPU-based architectures in terms of capacity, speed, and performance characteristics. The proposed system utilizes a heterogeneous computing platform combining the CPU and FPGA, thereby providing enhanced performance compared to conventional systems. Using a high-definition camera, actual sperm movements could be traced with high fidelity. The FPGA provides very high execution speeds necessary for recursive and expensive image preprocessing tasks. The CPU connects the camera to the devised system and is also responsible for performing calculations. The processing algorithms are executed mainly on the CPU, and the embedded system provides compact structure; moreover, the physical footprint of the system is smaller, which is advantageous in laboratory environments. Consequently, the proposed architecture is considered to be a step ahead of third-generation CASA systems, which is the primary novelty of this work. The proposed semen analysis system is implemented on a real-time operating system (RTOS) that also manages the embedded system with reconfigurable hardware for preprocessing and CPU for processing the executable parts of the algorithm. For sperm detection and tracking, the multiple moving object tracking system (MMOTS) algorithm is developed, which is the second novelty of this work. In terms of object detection, the background subtraction method is used for segmentation in MMOTS. The MMOTS approach is suitable for the selected architecture and imposes less computing load to achieve fast responses, which are crucial for real-time processing. Cellular neural network templates are used and experimented in the preprocessing part of the proposed system, where image-processing steps such as convolution, segmentation, and point representation are applied. This thesis begins with a brief introduction to sperm biology, semen analysis, sperm morphology and motility, and evolution of CASA systems. While the proposed work addresses motility analysis, the developed software also allows segmentation of static images to specify the head, nucleus, mitochondrial part, head shape, and size of the sperm as medical parameters. The algorithms, which are designed by considering computations on heterogeneous computing platforms, was next implemented on recent and state-of-the-art reconfigurable hardware. These hardware are commercially available and contain up-to-date components with reasonable prices. The complete system was realized on an NI CompactRIO 9030 hardware integrated with a microscope and available for medical tests as a prototype. The experimental work on human sperm samples were conducted at the Ege University Faculty of Medicine, İzmir, Turkey and Gelişim Tıp Laboratory, İstanbul, Turkey. The existing CASA system in Gelişim Tıp Laboratory was examined, and some experiments were carried out; the videos of these samples were obtained and examined in our preliminary and simulation studies. With respect to Ege University, the results of the proposed system are compared with those from manual inspections. In the manual assessments, the classifications were performed using the Makler camara (counting chamber), and the results of the proposed system were found to be 100% similar to those from manual assessments. The motility parameters, such as average progressive velocity VAP and curvilinear velocity VCL, can only be estimated roughly from manual assessments, but the results from the proposed system were deemed to be acceptable by the biologists in the laboratory. Experimental investigations were also performed on animal sperm samples at İstanbul University's Faculty of Veterinary Medicine, and the results of the proposed system were found to be approximately 80% compliant with those of the existing system in the laboratory. These variations are attributed to parameter settings; the parameters were roughly set to enable inspection of the effects of parameter values on the results, besides test result comparisons. The proposed system is flexible and hardware-based, so that different biological imaging applications could be deployed on it in the future. Eventually, the goal of this study is to achieve an intelligent biological analysis system.
Design and implementation of high power GaN amplifiers with nonlinear optimization techniques

(Lisansüstü Eğitim Enstitüsü, 2021) Kouhalvandi, Lida ; Özoğuz, İsmail Serdar ; 671561 ; Elektronik ve Haberleşme Mühendisliği

In this thesis new and novel optimization methodologies will be prepared to design nonlinear circuits operating at high frequencies. These novel methods can be used to optimize circuits with realistic models and process design kits (PDKs). Thus, nonlinear and complex power amplifiers with wide-band and high-efficient specifications can be designed by applying the proposed optimization algorithms. The developed script runs on a computer and manages the nonlinear simulator and numerical analyzer to optimize the challenging nonlinear circuit design problems regarding the design rules and conditions set by the designer and requirements. The proposed optimization algorithms are implemented in an automated environment with the combinations of electronic design automation (EDA) tool such as ADS and numeric analyzer as MATLAB. This process decreases the dependency to any designer's experience and without any human interruption all the optimization process is performed automatically. Power amplifiers (PAs) consisting of Gallium Nitride (GaN) high electron mobility transistors (HEMTs) will be designed with the proposed optimization algorithms. The PAs' efficiency, gain response, linearity, and bandwidth will be optimized to achieve high performance results regarding the reported studies. The PAs operate at saturation mode and nonlinear region; hence, high dimensions of variables are achieved. EDA tools such as ADS, AWR, etc. include nonlinear optimizations and are successful tools in optimizing circuits; however, additional powerful optimizations are required to deal with large amount of data. Also, the commercial EDA tools face with the problems when the unreliable nonlinear models are used during the optimization process.Therefore, a need for the new simulation environment that is the combination of the EDA tool and numerical analyzer becomes essential. Regarding to the difficulties in commercial EDA tools, it becomes necessary to propose an optimization strategy suitable for nonlinear circuits to be reliable for simulating nonlinear models and also able to challenge many trade-offs of high power amplifiers (HPAs) such as efficiency, linearity and gain flatness. The scope of the proposed methods are based on scrip development for two processes: i) a scrip to control nonlinear simulator (ADS) and numerical analyzer (MATLAB), ii) algorithms to optimize the circuit parameters. These algorithms result in high performance PAs in terms of efficiency, output power, gain, and linearity. The used transistor model is GaN technology due to the several advantages for radio frequency (RF) circuits such as high power density, high thermal conductivity, large breakdown voltage, and good reliability. This technology is suitable for future applications of radar and fifth generation (5G) systems. The importance of this work is divided in to four sections: 1) Providing an automated environment that is a reliable simultaneous co-operation of EDA tool (ADS) and mathematical analyzer (MATLAB); 2) Proposing novel optimization strategy based on intelligent algorithms for RF nonlinear circuits results in best high performance; 3) Substituting the proposed novel optimization technique to the automated environment; and 4) Optimizing the whole PA designs automatically and comparing the results of fabricated PAs with the simulation outcomes.
Mobil batarya enerji depolama sistemleri kullanılarak dağıtım sistemi işletiminin iyileştirilmesi ve sistem üzerindeki etkilerinin analizi

(Lisansüstü Eğitim Enstitüsü, 2021) Karahan, Oğuzhan ; Bağrıyanık, Mustafa ; 705347 ; Elektrik Mühendisliği Ana Bilim Dalı

Gün geçtikçe nüfus artışı ile birlikte teknolojinin de ilerlemesi, elektrik enerjisine olan ihtiyacı artırmıştır. Güncellenen dünyada, elektrik enerjisinin optimum kullanımı için çok çeşitli planlamalar yapılmaktadır. Önceki yıllara ait veriler kullanılarak ileriye dönük kısa veya uzun vadeli enerji tahminleri yapılmaktadır. Elektrik enerjisinin üretiminden tüketimine kadar her kademesinin optimum bir şekilde çalışmasını sağlayan birçok Enerji Yönetim Sistemi (EYS) vardır. Elektrik enerjisinin üretiminde birçok farklı kaynak kullanılmaktadır. Günden güne artan elektrik enerji ihtiyacı, sınırı olmayan enerji üretim kaynaklarının kullanımını arttırmaktadır. Güneş ve rüzgar gibi kaynaklardan elektrik enerjisinin üretildiği Yenilenebilir Enerji Sistemi (YES) birimleri yaygınlaşmaktadır. Elektrik enerjisi yüksek gerilim kademelerinde iletilerek son tüketiciye dağıtım sistemleri aracılığıyla ulaştırılmaktadır. Elektrik dağıtım sistemleri, birçok şebeke yapısıyla işletilebilmektedir. Sistemdeki tüketicinin sayısına ve profiline uygun olarak farklı şebeke yapıları kullanılmaktadır. Elektrik enerjisi üretildiği an tüketilmesi gereken bir enerji türüdür. Ancak, planlamalara uymayan sonradan eklenen yükler ve arıza durumlarında sisteme yardımcı bir güç kaynağı destek vermelidir. Bu noktada, Enerji Depolama Sistemi (EDS) birimleri önemli rol oynamaktadır. Enerjinin depolanma teknolojisine göre birçok çeşidi bulunan EDS'lerden bu çalışmada, Batarya Enerji Depolama Sistemi (BEDS) incelenmiştir. Elektrikli araçların artması ile birlikte batarya teknolojisine ilgi artmıştır. Yenilenen batarya teknolojisi, farklı kapasitelerde enerji depolanması fırsatı sunmaktadır. Kullanılan batarya türüne ve hareket etme özelliğine göre farklı türleri bulunan BEDS'ler, EYS'ler için önemli bir araç haline gelmiştir. Hareket etme özelliğine göre sabit ve mobil olmak üzere iki çeşidi bulunan BEDS'lerin birçok avantajı bulunmaktadır. Çoğu uygulama alanı ortak olsa da hareketli olma özelliğinden dolayı Mobil Batarya Enerji Depolama Sistemi (MBEDS)'nin kullanım alanı daha fazladır. Elektrik enerjisi üretim-dağıtım ağındaki çoğu birim için çeşitli faydaları bulunmaktadır. Gelişimi devam eden güncel teknoloji olan MBEDS'ler için literatürde birçok çalışma vardır. YES birimlerinin kesintili enerji üretimi nedeniyle bulundukları güç şebekesine MBEDS'ler ile entegre edilmektedir. Hareketli olma özellikleri sayesinde güç şebekesinde herhangi bir kısa devre arızası anında şebekeye ada işletimi sağlayabilmektedirler. Dağıtım sistemlerine entegre edildiklerinde gerilim düşümü ve güç kaybı gibi sistem parametrelerine etki etmektedirler. Günün herhangi bir anında meydana gelen puant yükü azaltmak için MBEDS'ler kullanılabilmektedir. Böylece tampon görevi üstlenerek güç şebekesi rahatlatılmaktadır. Elektrikli araçların şarj istasyonları olma görevi de edinebilmektedirler.
High sensitive torque control of permanent magnet synchronous motor for national military applications

(Graduate School, 2021-07-26) Köse, Mehmet Eralp ; Kocabaş, Derya Ahmet ; 504181249 ; Electronics and Communication Engineering ; Elektronik ve Haberleşme Mühendisliği

Electric motors are systems that convert electrical energy into mechanical energy, and they have a very important place in the industry. DC motors are often preferred for applications that do not require driving precision due to their ease of use and low cost. On the other hand, alternating current motors have many superior features over direct current motors. Alternating current motors have higher efficiency, lower maintenance costs, and high torque to volume ratio. They are more reliable and durable motors. One of the most important advantages of alternating current motors is that they offer superior motor control opportunities. With these motors, speed and torque control can be done with appropriate control methods. With the appropriate control method, torque control can be done at very low speeds. Because of these features, alternating current motors are preferred in control applications that require precision. With the developing magnet technology, permanent magnet electric motors come to the fore with their high efficiency. Power electronics and control applications are used together for the control of alternating current motors, and there are different methods and circuit structures in the literature for this. Control methods are basically divided into two as scalar and vector control. In scalar control, the "voltage/frequency" ratio is kept constant so that the flux remains constant, and the speed and torque are adjusted with the change in frequency. In this method, only the magnitudes of flux and current are controlled, rotor position information is not received as feedback and is not included in the control loop. In vector control, in addition to the magnitude of the flux and the current, the angle between them is also controlled, and rotor position information is required as feedback while speed and torque controls are being made. Direct torque control and field-oriented control are sub-branches of vector control. In field-oriented control, which is the focus of this study, the rotor position is needed. This information can be obtained with sensors, or it can be detected by sensorless estimation methods, and position information is used in control. In this way, while precise speed and torque controls are carried out, a more stable control is provided in a steady-state condition. In this thesis, high precision torque control of permanent magnet synchronous motors for use in military systems has been studied. The main goal is to design motor drivers that are imported and provide torque control in military stabilization systems and to reduce foreign dependency by using domestic and national motor drivers in these systems. Since high precision torque control is aimed even at low speeds in military applications, field-oriented control was used. Due to the high military expectations, sensor control was preferred, and an absolute encoder was preferred as a position sensor. This method can be applied in many areas with different power and torque requirements. Stabilization systems were chosen as the application. Based on filed-oriented control, a national control algorithm has been applied, and an infrastructure adaptable to the power and torque requirements of the application to be used has been established. In this context, TMS320F28069M type numbered processor from Texas Instruments (TI) company, and the trial card was used as controller. Inverter design is implemented with modular circuits of TI company, and MOSFET switches are used. Algorithm development studies were carried out in MATLAB/Simulink environment. An absolute encoder is used to increase sensitivity. With this encoder, absolute position information can be accessed and position information is not lost even if there is a power cut. The position information obtained from here is transferred to the field-oriented torque control loop. By carrying out the load test, the moment ripple in the steady-state and its performance at the rated load have been determined. Different communication methods have been used to determine the interaction of the performance of the system. Since it was seen that the method called "external mode" which works over Simulink, became insufficient and did not work efficiently as the algorithm became more complex, CAN communication was started, and it was ensured that the instantaneous torque value could be controlled with the P and I coefficients that can be changed instantly via the PI controller. Input and output feedbacks were instantly observed via Simulink, algorithms were written in Simulink, and all hardware was communicated with Simulink via CAN communication. The effect of switching frequency on torque ripple was investigated with appropriate P, I coefficients, and as a result of the optimization, this ripple was reduced below the values expected by the standards. In the second part of the study, compliance checks were made in terms of military standards, and temperature and electromagnetic compatibility tests were completed. Since a device with a chassis was not aimed directly, mechanical compatibility tests were not needed. Temperature tests were carried out between -40°C and +55°C in accordance with the standards, and the distortions observed in the clock frequency of the processor at values close to the limit temperatures in the first tests were overcome by the use of an external oscillator. Although an increase in torque fluctuation was observed in this test, the maximum value remained below 3%. In electromagnetic compatibility tests, MIL-STD 461 CE101 and CE102 tests were carried out, and the noise emitted by the device in various frequency ranges was measured. Although the noise remained above the acceptable level in the first CE102 test, the circuit passed the tests successfully with the appropriate filter design. In addition, with the study, infrastructure was created for the selection of materials for further studies. As a result, within the scope of this thesis, low torque vibration, high precision field-oriented torque control of a permanent magnet synchronous motor in accordance with military temperature and EMC standards have been realized. With the output of the thesis, domestic equivalents of hardware and software products supplied from abroad and used in national applications have been obtained, contributing to the country's economy and reducing foreign dependency in this area.
Microwave dielectric property characterization with open-ended coaxial probe and sensing depth analysis of the probes for biological tissues

(Lisansüstü Eğitim Enstitüsü, 2022) Aydınalp, Cemanur ; Abdolsaheb, Tuba Yılmaz ; 725335 ; Elektronik ve Haberleşme Mühendisliği

Inherent dielectric property discrepancy at microwave frequencies between the healthy and malignant tissues enabled many different microwave diagnostic technologies among these microwave breast cancer imaging, microwave hyperthermia, and microwave ablation are popular research topics. To develop and test such technologies the dielectric properties of the biological tissues must be quantified. This is mostly done with the open-ended coaxial probes in the laboratory environment due to advantages of the technique including but not limited to minimal sample preparation requirements, commercial availability and broadband measurement capabilities. Despite being commercially available, the technique suffers from high error rates and remains overlooked as a potential diagnostic technology. The error sources can be categorized as the sample and equipment related complications. The sample related error sources can be mitigated via the selection of an appropriate probe for dielectric property characterization. Particularly, biological tissues are known to be heterogeneous contributing to the high measurement error due to sample. Hence, it is important to analyze the sensing depth of the probes under different conditions including using samples with varying dielectric properties and probes with different aperture diameters. Next, the equipment related errors mostly due to the mathematical approach which can potentially be diminished via the introduction of new retrieval methodologies. Towards this end, in an attempt to enable diagnostics applications of the open-ended coaxial probe technique, this thesis focuses on the improvement of the two shortcomings by sensing depth characterization and introducing a deep learning based model for dielectric property retrieval. In the first part of the thesis, sensing depth analysis of the 2.2 mm diameter open-ended coaxial probe was performed using two different double-layered configurations to mimic the tissue heterogeneity. The double-layered configurations are used to mimic the heterogeneous skin tissue in order to establish the potential use of the open-ended coaxial probe method for skin cancer diagnosis. To this end, the sensing depth analysis was performed via simulations and measurements. The double-layered sample configurations are composed using skin-mimicking phantom and olive oil or triton X-100 liquids. In addition, the experiments were carried out by following a newly proposed measurement protocol, which can be easily applied to any tissue type. The results show that the sensing depth was independent of the frequency of operation (0.5-6 GHz) and was affected by the following conditions: by the material located immediately at the probe tip, and by the dielectric property contrast between the two layers. Thus, in order to accurately obtain dielectric property measurement results using the open-ended coaxial probe method, there is a need to establish a pre-measurement protocol to minimize the error due to the skin tissue diversity. The second part of thesis reports the sensing depth analysis of the open-ended coaxial probe for ex vivo experiments on real heterogeneous tissue. The knowledge on the sensing depth of the probe can help eliminate the errors due to tissue heterogeneity. Accurate classification of tissues with similar dielectric properties can be obtained by minimizing the measurement errors. Therefore, this method can be applied in practical applications, such as microwave biopsy. In this work, double-layered sample configuration consisting of an ex vivo rat's breast or wet skin as first layer and pure liquids olive oil or triton X-100 as second layer was utilized to perform the sensing depth analysis of the probe from 0.5 to 6 GHz frequency range. A straight forward, adoptable experimental protocol was established and employed in this study. The analysis was performed by determining five different the percent change in measured dielectric property values. The results indicate a discrepancy of 52%-84% of the measured dielectric property when a membrane layer (between 0.4-0.8 mm thickness) was present on the wet skin tissue and breast tissue. The aim of the third part of this thesis is to analyze and to specify the sensing depth of the open-ended coaxial probe in order to employ the appropriate probe aperture dimension for any given measurement set-up. The proposed method has the potential to reduce the errors due to tissue heterogeneity for skin cancer diagnosis. This work presents the sensing depth comparison of three different probes with different aperture sizes. Simulations of the probes with 0.5, 0.9 and 2.2 mm-diameters terminated with a double-layered skin tissue and olive oil sample configuration were performed. It should be noted that probes with different aperture diameters were investigated in the literature but no information was reported on probes with small aperture sizes. An experimental validation of the simulated scenario was performed with the 2.2 mm-diameter probe and the fully developed double-layered configuration. The acquired simulations and experimental results indicate a proportional relation between the sensing depth and the aperture of the probe. From this relation, it can be concluded that probes with smaller aperture size can possibly help to obtain more precise results from the heterogeneous tissues which can lead to the accurate characterization of thin skin tissue layers. In order to obtained more accurate results especially for tissues with multi-layered structures or membrane-like layers, it is recommended to a establish measurement protocols to prepare the surface of the tissue. In the fourth and last part of the thesis, a novel approach for the determination of material dielectric properties from the reflection coefficient response of the open-ended coaxial probe is proposed. This technique retrieves the Debye parameters of the material under test using a deep learning model which is trained with numerically generated data. The ability to train the deep learning model with synthetic data provide the advantage of rapid generation of a large variety of materials as a dataset. Additionally, the presented method can be easily adapted to any type of probe with desired dimensions and materials. An experimental verification of the trained deep learning model was performed by testing the network with measured reflection coefficients obtained from five different standard liquids, four mixtures, and a gel-like material. A comparison of the acquired results from the deep learning model with literature values is also performed. Finally, a large-scale statistical verification of the retrieved dielectric property from the proposed technique is presented.
Hard and soft tissue characterization with microwave dielectric spectroscopy

(Graduate School, 2022) Keskin, Seda ; Akgül, Tayfun ; 741159 ; Department of Electronics and Communication

The dielectric property discrepancy between hard and soft tissues at microwave frequencies can potentially be utilized for the separation of those tissues from each other. Microwave dielectric properties of biological tissues are traditionally measured with the open-ended coaxial probe technique. However, the technique suffers from high error rates thanks to tissue heterogeneity, user errors, mathematical approach, and calibration degradation. It is known that datasets with different values will be classified with high accuracy when a machine learning algorithm is applied. Therefore, choosing a classification parameter that might be least plagued by inherent errors is critical for increasing the accuracy of tissue categorization. Empirically, dielectric properties at microwave frequencies abide by the power law. Supported this fact, one unexplored parameter is the power parameter which might be derived from the dielectric properties. This work presents investigations on the potential use of the power parameter to separate different tissues, spesifıcally hard and soft tissues, supported by the datasets within the literature. Additionally, to research the effectiveness of the power parameter, classification was performed with machine learning algorithms using the power parameters obtaıned from dielectric property measurements of healthy and malignant liver tissues. Through the appliance of the technique 82% accuracy was obtained. Towards this goal, it's predicted that the power parameter might be used as a feature containing different information additionally to dielectric properties in tissue classification. Alternatively, in some cases dielectric properties do not provide enough information, one example is that the separation of hard and soft tissues, under such conditions the power parameter might be employed for classification purposes. This approach might be used as an alternative method for rapid diagnostic to high-cost imaging or mutation screening tests. The frequency-dependent dielectric properties of the biological tissues are crucial to developing diagnostic technologies.
Design of an OPAMP-RC lowpass filter in 22 NM FDSOI technology

(Graduate School, 2022) Keleş, Ömer Taha ; Yazgı, Metin ; 734685 ; Electronics Engineering Programme

Analog filters are widely used in signal processing applications like noise reduction, blocker rejection, signal detection, anti-aliasing, demodulation, audio processing etc. They are utilized to allow certain signals to pass while blocking others. Passed or blocked signals are not time dependent since analog filters are time invariant circuits. These filters pass or block signals depending on the signal's frequency, meaning that signals in specified frequency ranges are blocked or passed. While time domain responses of the filters are still a critical design consideration, filters are mainly designed considering the desired frequency domain responses. Main types of filters can be categorized as lowpass, highpass, bandpass and bandstop according to their selective frequency range. There are various types of lowpass filter responses which have different passband or stopband characteristics. Brick wall response, whose pass and stop bands are separated at the corner frequency, has a discontinuous frequency response. This type of a mathematical function is not realizable in real world. On the other hand, realizable filter responses are continuous functions with finite roll-off slopes between stopband and passband. The slope at the transition band depends on the order of the filter function and the type of the filter function. Additionally in real filter functions there may be permitted fluctuations which may appear in stopband, passband or both. In Butterworth response, the passband has flat frequency characteristics so it is called maximally flat magnitude response. Likewise, Chebyshev type I filter response has equal ripples in the passband so it is called equal ripple magnitude response. Chebyshev type II filter response, or equal ripple stopband magnitude response, has equal ripples in the stopband and Cauer filters have ripples in both stopband and passband. The question of how to realize filter functions with real circuit elements arises numerous solutions. Such filter functions can be realized using circuit elements like resistors, capacitors, inductors and some specialized circuit elements such as operational amplifiers and switched capacitors. Filter characteristics and design limitations vary greatly depending on the circuit elements and topologies used. In order to realize lowpass filter functions, various different circuit topologies are proposed over the last couple of decades. Filters are classified depending on the circuit elements employed. LC ladder filters consist of inductors, capacitors and resistors which are all passive elements. Besides resistors and capacitors, Opamp-RC filters utilize active circuit elements called operational amplifiers. Moreover, OTA-C filters are implemented using operational transconductance amplifiers and capacitors. Furthermore, capacitors, operational amplifiers and switched capacitor circuits are used to build switched capacitor filters. All the different circuit topologies have their advantages and disadvantages. It is the designer's job to determine which topology is a better choice considering the design specifications and limitations. Over the years, shrinking of transistor sizes resulted in reduced analog performance and lower voltage headroom.
Classification of chest X-rays by divergence-based convolutional neural network

(Graduate School, 2022) Kılıç, Muhammed Nur Talha ; Ölmez, Tamer ; 731698 ; Electronics Engineering Programme

The importance of imaging methods in the field of health is increasing day by day with the opportunities provided by technology. Imaging without physical intervention is both more convenient and less costly for the patient and one of the ways to diagnose faster. Diagnosis of diseases and taking action, especially in the early stages of epidemic diseases, are among the most effective methods in the fight against these diseases. Correct treatments are applied against diseases that can be differentiated from each other, thus the patient's recovery is ensured. Chest radiographs are also one of the most frequently used methods in the field of imaging, and the damage caused by various viruses or bacteria to the lung can be understood and diagnosed with X-ray images. At the same time, it ensures that health systems continue with minimum damage by providing the necessary data for health workers to take precautions in case of an infectious side of the disease. Covid-19, which entered our lives towards the end of 2019 and caused the death of millions of people in more than 2 years, directly damages the lungs and causes the lungs to not perform their functions. Problems that occur in the lungs by reducing oxygen saturation cause many issues, especially respiratory problems in patients. Some of the problems seen in patients with suspected Covid-19 occur in the lungs and these changes caused by the disease can be detected by X-rays. However, it is not known to what extent the effects of viruses such as Covid-19, which have been in existence for years but have the capacity to infect people in the near future, and it is not possible to deliver treatment techniques to all parts of the world in a short time. In other words, it is a very long and laborious process to be able to effectively diagnose diseases that we can call new diseases that come into our lives by health workers around the world. For this reason, engineering applications in the field of medical imaging are promising in many respects. For example, AI-assisted engineering applications, which have become very common recently, bring many advantages. These achievements can be listed as follows: •Detailed analysis opportunity •Instant access to developments in the world •Ability to be easily updated •Possibility to get results with high accuracy and fast •To alleviate the burden of healthcare workers •Cost-reducing contributions with fewer employees •Reaching areas with low or limited access to the health system •Reducing the contagious risk of the disease by reducing direct or indirect contact with patients •Creating systems whose accuracy and reliability are increasing day by day with continuously trained models. •Opportunity to create models trained with more examples than specialist doctors can see throughout their career Although the developments mentioned are undeniably positive, the physical hardware needs that come with artificial intelligence supported applications should not be ignored.
Analysis and design of cryogenic bulk-driven analog integrated circuits

(Graduate School, 2022) Ormancı, Mehmet Aytuğ ; Yelten, Mustafa Berke ; Kaçar, Fırat ; 737869 ; Electronics Engineering Programme

Today, exponentially increasing studies such as quantum electronics, asteroid and planet observations, and even space mining have increased the need for electronic circuits that can operate under extreme conditions without error. Circuits that can operate without consuming much power, especially in space conditions, allow for more or uninterrupted observations and measurements. The operating conditions for circuits operating in space are extreme. It is essential that the designs made for these circuits, which must operate in both high radiation and very cold conditions, produce accurate results because space is still a very costly environment in terms of research and observation costs. In this case, it is important to correct the errors in the designs at the simulation stage. The concept of a cryogenic environment defines the temperature values of 120 K (−153 ℃) and below, although the exact limits are not clear. This is because this temperature includes the boiling points of the main atmospheric gases. The design at cryogenic temperatures is indispensable for space exploration and quantum computers. Liquid nitrogen environment (LNT) is the most common method used to model cryogenic environments on the earth's surface and in laboratories and to develop circuits operating in space conditions. Nitrogen, which has a boiling point of approximately 77 K, contains most of the critical situations that electronic circuits encounter in space conditions. The operating range for integrated circuits traditionally based on common design models such as BSIM is between −55 ℃ and +125 ℃. However, when the design results made with these models are examined, it is observed that the error rate increases even moving away from the room temperature. This makes it inevitable to use new models for cryogenic conditions. The cryogenic modeling process used in this thesis is based on the logic of recalculating and replacing temperature-sensitive parameters and sub-parameters in the BSIM by using a MATLAB environment with a new algorithm. In this way, the margin of error in the experimental measurements is considerably reduced and this environment is accurately simulated in computer-aided programs. In experiments with many transistors in the cryogenic environment, it has been observed that the threshold voltage increases, but the current flowing capacity of the transistors increases as the mobility of the carriers rises. In addition, in the theoretical and practical studies, the linear reduction of thermal noise, which is seen as the main source of the noise in transistors, with temperature is promising results for the designers. With the developing electronic technology, the use of portable devices and biomedical sensors has become quite common. This brings the need for more efficient use of batteries, which cannot develop at the same rate. For this reason, the electronics industry turns to devices that work with less than 1 V power supply and consume very little power. One of the circuit design methods with a very low power supply is bulk-driven (BD) structures. Thus, when the gate terminals are biased with a DC voltage that creates a channel between the source and the drain, the current passing through the channel can be manipulated by the input signal applied from the bulk. In terms of the circuit designs, this method means removing the threshold voltage from the signal path. The most important advantages of the bulk-driven transistors can be shown as having much more linear transconductance and much less power consumption. In addition, without using n-channel and p-channel transistors together, the input common-mode range (ICMR) and output swing can be rail-to-rail. However, driving the transistor from the bulk also brings some disadvantages. The most important issue is the bulk transconductance is quite low compared to the gate-driven counterpart. Although it is theoretically possible to increase, it can activate the parasitic Bipolar Junction Transistors (BJT) in the structure and damage the chip. Also, low transconductance increases the noise factor of transistors. Another detriment is the high capacitive effects on the body. These effects greatly reduce the transition frequency of transistors. Another low power circuit design method is to operate the transistors in the subthreshold region. Transistors enter the subthreshold saturation region between 3 and 4 times their thermal voltage and can operate with low power supplies. Operational transconductance amplifiers (OTA), which are one of the indispensable building blocks of analog designs, are frequently used in analog signal processing, thanks to the high-level linear transconductance and stable high frequency performance. In this study, a three-stage OTA is designed in which all transistors operate in the subthreshold saturation region. It consists of an input stage based on non-tailed differential amplifiers, a second stage with a common-source amplifier, and a class AB output stage. The input stage provides high ICMR and 36 dB DC gain. The bias current of this structure was calculated as 8 nA using thermal noise and dynamic range in the voltage follower configuration.
Deep learning based fruit and vegetable recognition for android pos devices

(Graduate School, 2022-01-17) Ekici, Ege ; Güneş, Ece Olcay ; 504181209 ; Electronics Engineering

With the recent improvements in technology, time and expense-saving products have gained an important trend in marketplaces. Recent increases in shopping trends created a need for faster payment technologies. Even though the barcode system is currently one of the most popular technologies being used, this system is not fault-tolerant and likely to be inefficient for unpackaged products by being human dependent. As an example, fruits and vegetables are two of the most popular unpackaged product categories that are being priced based on the amount bought and cashiers usually enter a product code manually in case of purchase. Along with that, some businesses have installed self-checkout tables where customers can handle their own payments to decrease shopping time in rush hours and save on employee expenses. But self-checkout tables depend on customer trust when it comes to unpackaged products since any customer can select a product of a different price from the list. At the same time, self-checkout tables are very costly for most businesses. As a solution to the aforementioned problems, a system is proposed in this project that aims to benefit in security, expense, and time. The system aims to be advantageous by not creating an additional hardware expense by using the Point of Sale (POS) devices that most businesses already have. Focusing on fruits and vegetables, a recognition system is added using the device camera to prevent human-dependent security problems of the existing systems. Various techniques are experimented with to achieve a real-time system. In this project, a dataset consisting of 14 types of packaged and unpackaged fruits and vegetables is used. Related works usually implemented object classification and object recognition algorithms for similar problems but since objects can exist in different locations and amounts on a frame, an object recognition algorithm is decided to be more suitable for this project. Along with object detection algorithms being more complex than object classification algorithms, having POS devices with limited resources created a risk of the device being insufficient against the high computational needs of the system. For this reason, decreasing the model size and making the model closer to real time by decreasing the computation time became one of the purposes of this project. Therefore, among the object detector methods, it is decided to select a one-shot detector model. "You Only Look Once (YOLO)" is one of the state-of-the-art one-shot algorithms and is a well-known algorithm that has several versions developed over years. In this project, two of the latest versions; YOLOv4 and YOLOv5 are used and compared under several performance metrics and the best results are obtained with YOLOv5 with a mAP score of 98%. Later, several quantization methods are examined and compared for the purpose of creating a model of smaller model size and better performance. Among the quantization methods, best results are achieved with Full Integer Quantization, and model size is decreased by 75%. The proposed detection model is deployed on an android-based 400TR POS device developed by Token Financial Technologies with MT8167A (1.5 GHz) CPU. On the final system, inference time is observed as 1.332 seconds.
4 channel configurable constant-current/voltage mode biphasic implantable neurostimulator ASIC with channel centric active charge balancer

(Graduate School, 2022-03-02) Cakalı, Anıl ; Karalar, Tufan Coşkun ; 504161229 ; Electronics Engineering

Electrical stimulation is a technique that let inhibition or exhibition neuron activities with charge injection to a target tissue. Neural stimulators are used as a treatment method for diseases and the restoration of dysfunctional organs. Sacral Nerve Stimulation that is used for the treatment of bladder and urinary functions, Deep Brain Stimulation (DBS) that is used for the treatment of diseases such as Parkinson's disease, epilepsy, tremor, depression, and obsessive-compulsive disorder, Spinal Cord Stimulation that is used for the treatment of chronic pain syndrome, Retinal Stimulation that is used for recovering visual functions and Cochlear Stimulation that is used to recovering of hearing functions are some of the application fields of electrical/neural stimulation. Considering application fields, most neurostimulator/neuromodulation devices are implanted in the human body. These devices are battery-powered devices that have long battery life, because of that an Application Specific Integrated Circuit (ASIC) is needed for implantable applications considering application specifications like target nerve, power consumption and output properties. Neurostimulators interface with target neurons by using electrodes. Charge accumulation on an electrode-tissue interface may cause Ph variation of electrolyte, toxic surface creation between electrode-tissue interface and variation of electrode-tissue impedance. Most importantly, it may cause permanent nerve damage. Using biphasic stimulation and active charge balancer structure together is the preferred method to achieve ideally zero net charges on the target tissue. Constant-current stimulation, constant-voltage stimulation or constant-charge stimulation methods are presented in the literature. Constant-current stimulation is the safest stimulation method. Ideally, zero net charge on tissue may be achieved by controlling anodic and cathodic current amplitudes and durations in a biphasic manner. For constant-voltage stimulation, the amplitude of current that flows through the electrode-tissue interface is determined by the impedance of the electrode-tissue interface. Due to that reason, it is not easy to control transferred charge to tissue. Constant-charge stimulation is a useful method to achieve charge balancing by using switch-capacitor structures. The disadvantage of constant-charge stimulation is that it needs larger capacitors that cause some difficulties with on-chip implementation. In literature, neurostimulator ASICs are designed for only constant-current mode stimulation or only constant-voltage mode stimulation. Similarly, most charge balancer circuits are designed for just constant-current mode stimulation or constant-voltage mode stimulation. In this work, a novel active charge balancing scheme that works with both constant-current mode and constant-voltage mode for monopolar/bipolar/tripolar/quadripolar electrode polarities is proposed. Furthermore, a novel channel circuit and novel channel centric active charge balancer circuit topologies that support both constant-current and constant-voltage stimulation mode in the same structure are developed. Constant-voltage mode stimulation is considered the standard technique of DBS applications for a long time. On the other hand, constant-current mode stimulation is emerging as an alternative solution for DBS applications. Supporting both constant-current mode and constant-voltage mode with active charge balancing makes this work appropriate for DBS applications. The purpose of this work is to increase the flexibility and safety of neurostimulators because this work allows switching stimulation mode after surgery and supplies active charge balancing for both stimulation modes for safety. Neurostimulator ASIC is constructed by 4 channels. Each channel consists of N-Block, P-Block and Channel Centric Active Charge Balancer. Each channel is configurable to supply ground, 10 V, 0-1 mA configurable sink current or 0-1 mA configurable source current in constant-current stimulation mode. Each channel is configurable to supply ground, 10 V, 1-5 V configurable low voltage or 5-9 V configurable high voltage in constant-voltage stimulation mode. N-Block circuit is designed to supply ground, 0-1 mA configurable sink current or 1-5 V configurable low voltage. P-Block circuit is designed to supply 10 V (as VDD), 0-1 mA configurable source current or 5-9 V configurable high voltage. Stimulation period, anodic phase time and interphase delay time are configurable parameters. Cathodic phase duration is not configurable because it is controlled by using outputs of Channel Centric Active Charge Balancer asynchronously. N-Block and P-Block circuits are similar to each other and complementary structures. The supply voltage of the stimulator circuit was chosen as 10 V to prevent headroom problems. Considering high voltage supply requirements, the Taiwan Semiconductor Manufacturing Company (TSMC) 0.18 um Bipolar-CMOS-DMOS (BCD) technology process was chosen. Relatively high biasing currents and enable/disable circuits were used for analog blocks to achieve higher performance with lower power consumption. The actual channel current is estimated by using differences of internal currents. Internal currents are mirrored to channel centric active charge balancer circuit to estimate channel current and use it for charge balancing. Timing setting resolution was chosen as 1 us. All analog blocks that are used in N-Block and P-Block were designed in Cadence Virtuoso considering timing, voltage and process constraints. DC, AC, transient and stability simulations were run to verify analog subblocks with Cadence Spectre. Transient simulations were run to verify constant-current stimulation mode and constant-voltage stimulation mode behaviors of N-Block and P-Block. Maximum current error results for constant-current stimulation, maximum voltage error results for constant-voltage stimulation and channel current estimation error results for both stimulation modes are given as simulation results. Channel centric active charge balancer was designed with Cadence environment. Transient simulations were run considering stimulation duration and current amplitude boundaries to verify functionality and determine performance with Cadence Spectre. Charge errors are presented as simulation results. Register Transfer Level (RTL) design of the stimulator controller was designed with Verilog Hardware Description Language (HDL). Synchronous state machines are used to implement the stimulator controller. Asynchronous digital circuits are used to handle outputs of active charge balancer circuits. The stimulator controller was synthesized by using Cadence Genus tool. Place and route process was performed by using Innovus tool. Digital blocks were integrated with analog blocks in Cadence Environment and Analog-Mixed Signal (AMS) simulations were run to verify the behavior of the neurostimulator ASIC for constant-current and constant-voltage stimulation modes with random test vectors. As a conclusion, 4 channel configurable constant-current/voltage mode biphasic implantable neurostimulator ASIC with channel centric active charge balancer was verified by using AMS simulations for both constant-current and constant-voltage stimulation modes. AMS simulation results show that the ASIC works functional and the proposed channel centric active charge balancing scheme is verified for both stimulation modes.
Bandgap reference and low dropout voltage regulator desıgn for capsule endoscopy system

(Graduate School, 2022-06-01) İnam, Benan Beril ; Yelten, Mustafa Berke ; 504191204 ; Electronics Engineering

For the last 40 years, there have been many advancements in biomedical systems as there is a huge demand for them. A capsule endoscopy device is one of the biomedical systems which is used for the imaging of the gastrointestinal system. Endoscopic procedures require two operations because when the procedure starts from the esophagus it can only reach until duodenum, however imaging of the small bowel can be only accessed from the anal cavity. This operation is highly uncomfortable for the patient since the diagnosis of the entire gastrointestinal system requires two endoscopic procedures. To make this operation more comfortable for the patient, capsule endoscopy is developed. The capsule endoscopy system includes a laser source and a laser driver to process the information coming from the source and a transmitter system to transmit the processed data. The transmitter involves an analog to digital converter, transimpedance amplifier, power amplifier, and a phase generator. A single battery is used to supply voltage for all of these mentioned circuits. The battery input voltage of the system decays with time and to increase the lifetime of the capsule it is essential to design a power management unit. This power management unit involves a regulator to create supply voltage for chip blocks and a reference generator to obtain process-voltage-temperature independent reference. For the regulator, a low dropout regulator is chosen as they do not have ripple at the output voltage as in switching regulators which makes them less noisy. Noise is an important parameter because the input signal is low and any input voltage may affect the operation of the circuits. Traditional LDOs require a large off-chip capacitor at the output to create a right half plane zero and stabilize the circuit. However, the capsule is strictly limited in the area hence a cap-less LDO is designed. To enhance the transient performance after removing the output capacitor, a dynamic bias circuitry is added to the design. Output voltage only changes 6 % with process-temperature-voltage corners. Load and line transient results show that even though the input voltage or output load changes with time, the circuit can still regulate the output voltage. To obtain reference voltages for the blocks, a bandgap reference voltage generator is designed. In this design, two different design structures are used to achieve temperature independence. Both MOS and bipolar transistors are employed for this purpose. Design with MOS transistors advantages from operating in the subthreshold region hence supporting lower supply voltages however it has a larger variation at the output due to threshold voltage change over corners. Bipolar transistors benefit from less PVT variation however their performance degrades with lower supply voltages and high temperatures. To use two different characteristics of both designs, a system that switches to better performing structure is built. A comparator is designed to detect temperature and supply voltage. In this system, reference with bipolar transistors operates when the input voltage is higher than 2.8 V and at lower temperatures, and reference with MOS transistors starts to work when the input voltage is lower than 2.8 V and at higher temperatures. To further reduce the variation of the design with MOS trimming structure is implemented to the output resistor and variation decreased from 15% to 5%. The temperature coefficient of the reference generator is calculated as 75C. A power management unit that involves a bandgap reference generator and a low dropout regulator is introduced and designed. Important performance parameters are extracted from the requirements of the capsule endoscopy transmitter. Hence, the layout area is designed to be small and output voltage variation is minimized over PVT corners. The layout of the system is designed and post-layout simulation results are reported in the study.
Design of a microprocessor-based embedded fault diagnostic system and an FPGA-based improvement proposal

(Graduate School, 2022-06-06) Bekar, Onur ; Güneş, Ece Olcay ; 504181292 ; Electronics Engineering

In the past, the use of proprietary hardware, software and protocols in systems and the lack of continuous interaction between the systems /subsystems were a natural obstacle to prevent critical errors from occurring for systems. Therefore, troubleshooting, which has been important in engineering from the past to the present, was not as challenging as in current applications, and the detection of errors was not seen as important part of as it is at present in systems' lifecycle. However, today's applications are complex systems consisting of embedded systems, units, modules etc. that continuously interact with each other, with interfaced, chip to chip, wired and/or wireless communication between. In addition, the widespread use of new technologies, protocols, commercial off-the-shelf (CoTS) products and operating systems has made a remarkable effect to increasing the error's frequency. The increasing complexity of engineering applications has brought challenges associated with the exposure to multifarious failures or errors, affecting the systems' reliability, safety, availability and performability. In this sense, new concepts such as error detection, debugging, error recovery, correction, maintenance and repair over have become indispensable elements of engineering applications. In particular, the detection of errors has become even more important in order to correct the errors, ensure maximum efficiency, and provide optimized and sustainable systems. In this context, the systems, named as Fault Diagnostic Systems; designed specifically for the purpose of detecting and recording the error conditions on the software, hardware or equipment etc. have become widespread in different fields such as, defence industry, industrial control and automation systems, aerospace industry, railway transportation sector, smart factories, electric and hybrid vehicles, power plants, network and information technologies, automotive, medical/healthcare systems and have become an important part of the system design phase. In this thesis, a microprocessor-based embedded fault diagnostic system, which will operate in conformity with or integrated into main units such as control, automation, power units to be used in numerous fields is designed. This diagnostic system is fundamentally a logger system that continuously records sensor data to be sent from the main system and creates the "Error Messages" formed from the waveforms measured by the sensors. The related system is responsible for and able to record the measurements real-timely, operate in different modes according to the present scenarios, detect the data for a certain second before the error occurs in case of a situation that is considered as an "Error" by the main system, and store the error messages permanently in protected memory structures. In the the first chapter of the study, a comprehensive literature review on fault diagnostic systems and embedded systems is made. In relevant parts of the chapter, the related issues are researched in details such as their history, purposes, structures, operating logics, architectures, hardware and software components etc. In the second chapter, a microprocessor-based diagnostic system is designed by starting from the requirements and conceptual system design. Then, it is advanced to Detailed System Design Phase which the system architecture and operating scenario for the system are built and needed specifications such as sampling frequency, data sizes, required memory etc. are calculated. Afterwards, the hardware and software development processes are started respectively by taking the system level designs as reference. In hardware design studies, components used in the Diagnostic PCB such as memory units are selected according to the results of analysis on memory types. In the final part of the hardware design phase, a printed circuit board named Diagnostic PCB is designed in Altium PCB Design Software & Tools by using the recommended information in datasheets, PCB design rules and lessons learnt from past experiences. Then, the PCB is manufactured and verifications tests are performed. Thus, the hardware is verified and software development processes in C programming language are started. In software development process, software architecture is built and the architectural design is made based on the scenario determined in the system design section. The Diagnostic software is designed and verified one by one. In the third chapter, accuracy and performance tests are conducted for the Diagnostic System in the microprocessor-based inverter control unit (ICU) setup, and the results are given. Within the scope of the tests, a dummy traffic is generated and the external systems that Diagnostic System will work with or operate into are simulated. By doing so, real operation scenarios run, and essential optimizations for software are made. Then, the accuracy and performance of the system are retested again and again by simulating the real environment, and the system is verified and validated. The last development within the scope of the thesis is an FPGA-based improvement which is named Multitasking Diagnostic System proposed in the fourth chapter. The related system is developed starting from zero by using VHDL in the VIVADO Design Suite environment as high-level. However, it should be emphasized that no hardware design or tests on physical setup have been made, as in the system developed based on microprocessor. The new system model providing uninterrupted operation is created by considering the advantages of using FPGA for embedded applications such as parallel processing, speed, flexibility, extendibility. In the fifth chapter, accuracy and performance tests are performed also for the Multitasking Diagnostic System through behavioural simulation on the VIVADO Design Suite environment. For all tests, a dummy sensor traffic is generated and a similar scenario is built by taking the scenario followed in the microprocessor-based design processes as reference. Scenarios are run repeatedly by simulating the real environment, and essential optimizations for firmware are made also for. And consequently, the system is also verified and validated. In the last chapter, the microprocessor-based and FPGA-based system designs with their results are summarized, especially the worth-emphasizing parts are given by restating the dissertation main motivation which is the need of an Embedded Diagnostic System. The systems are examined, and a detailed comparison containing their advantages and disadvantages according to the requirements and circumstances is given. Lastly, the contributions to the literature, and the future considerations related to the dissertation is introduced. In conclude, both of the microprocessor-based and FPGA-based systems are successfully designed, verified and validated.
Derin öğrenme ağları kullanılarak doğal ortamda hastalıklı domateslerin belirlenmesi

(Lisansüstü Eğitim Enstitüsü, 2022-06-28) Kapucuoğlu, Köksal ; Kırcı, Mürvet ; 504181277 ; Elektronik Mühendisliği

Birleşmiş Milletler ile Gıda ve Tarım Örgütünün yayımlandığı raporlara göre, 2050 yılında dünya nüfusunun 7 milyardan 10 milyara çıkması beklenmektedir. Bu kurumların yayımladığı diğer bir raporda, 2050 yılında beklenen nüfusu beslemek için önümüzdeki yıllarda dünya genelindeki gıda üretiminin %70 oranında artması beklenmektedir. Kentleşmeden dolayı tarımdaki iş gücünün azalmasından ve geçmişten günümüze kadar gelen geleneksel yöntemlerle gıda üretimin bu kadar arttırılması mümkün olmayacağından tarımda teknolojiden faydalanmak gerekmektedir. Bu anlamda tarım, teknolojik gelişmelerden pozitif anlamda etkilenen en önemli sektördür. Tarımda teknolojik anlamda son dönüşümünü temsil eden tarım 4.0 ile birlikte akıllı tarım ve dijital tarım konuları popüler hale gelmiştir. Akıllı tarımla birlikte gelen otomasyon sistemlerinin en çok uygulandığı alanlardan biri de hasat otomasyonudur. Yetiştirme ve hasat dönemi arasındaki süreyi en verimli şekilde geçirmek, üretilen ürünün kalitesine ve hasat miktarına direkt etki etmektedir. Bu sebeple, yetiştirme ve hasat dönemi arasındaki sürede, hasta bitkilerin tespit edilmesi ve ilaçlanmasının en doğru şekilde yapılması gerekmektedir. Nüfusla birlikte gerekli olan gıda ihtiyacının sürekli arttığı bu ekosistemde, dünyada üretim-tüketim miktarı ve geniş kullanım alanları baz alındığında, domates, en önemli sebzelerin başında gelmektedir. Domates yetiştiriciliği sırasında, yüksek doğruluğa sahip bir hasat otomasyon sisteminden yararlanmak bir gereksinim haline gelmiştir. Geleneksek yöntemlerle domates yetiştiriciliğinde; verilecek gübre miktarı, ilaçlama zamanı ve hasta olan domateslerin tespiti, insana bağımlılığı açısından hataya ve verimsiz bir süreç yönetimine açıktır. Bu yüzden son yıllarda hasat otomasyon sistemlerinde, insan bağımlılığını en aza indiren ve karmaşık sistemlerde bile yüksek doğrulukta ve hızda sınıflandırma yapan derin öğrenme teknolojisinden yararlanılmaktadır. Bu alanda yapılan çalışmaların çoğunda, hazır ortamlarda çekilen domates görüntülerinden oluşan veri kümeleri kullanılmıştır. Bu yüzden yapılan çalışmalar sonucunda sunulan derin öğrenme ağlarından çoğu, saha ortamında çalışmaya uygun değildir. Bahsedilen bu sorunlara karşı bu çalışmada, doğal saha koşullarında da yüksek hızda ve doğrulukla sınıflandırma yapabilen bir sistem önerilmiştir. Son yıllarda yaygın bir şekilde kullanılan derin öğrenme ağları incelenerek performans metrikleri belirlenmiştir. Daha sonra farklı davranıştaki veri kümeleri ile eğitilerek, eğitilen modellerin performansları incelenmiştir. Bu çalışmada; AlexNet, SqueezeNet, MobileNet v1, MobileNet v2, ResNet-50, GoogleNet, Inception v3 ve Inception ResNet v2 ile birlikte toplam 8 farklı derin öğrenme ağı incelenmiştir. Veri kümesi olarak; sınıflandırma çalışmalarında yaygın bir şekilde kullanılan Plantvillage ve Tiny-imagenet veri kümesi ile birlikte bu çalışmada kullanılmak için oluşturulmuş olan Çanakkale domates tarlası veri kümesi kullanılmıştır. Plantvillage veri kümesinde, 9 hastalıklı domates yaprağı sınıfı ve 1 sağlıklı domates yaprağı sınıfı olmak üzere toplam 10 sınıf vardır. Tiny-imagenet veri kümesinde 200 farklı nesne sınıfı bulunmaktadır. Bu çalışmada kullanılması için, Çanakkale-Erenköy'de bir domates tarlasında doğal saha şartlarında çekilen domates görüntülerinden oluşan Çanakkale domates tarlası veri kümesi oluşturulmuştur. Çanakkale domates tarlası veri kümesi oluşturulurken, dahil edilen doğal etkenlere göre bu veri kümesi iki şekilde temsil edilmiştir; temel Çanakkale domates tarlası veri kümesi ve karmaşık Çanakkale domates tarlası veri kümesi. Temel Çanakkale domates tarlası veri kümesindeki her bir görüntü, çekim tekniklerinden ve doğal şartlardan kaynaklanan ışık farklılıkları, görüntü yakınlığı, blur çekim, görüntü çerçevesinde yaprakların olması gibi etkenler içermektedir. Karmaşık Çanakkale domates tarlası veri kümesindeki her bir görüntü ise, temel veri kümesindeki etkenlerin dışında dal, başka bir domates, yaprak gibi ekstra etkenler içermektedir. Bu çalışmada yapılan denemeler sonucunda, Tiny-imagenet veri kümesi ile derin öğrenme ağlarının eğitiminde en iyi sonuca, %42.62 doğrulama doğruluğu ile Inception v3 ağı ile ulaşılmıştır. Plantvillage veri kümesi ile derin öğrenme ağlarının eğitiminde en iyi sonuca, %99.1 ile MobileNet v1 ağı ile ulaşılmıştır. Temel Çanakkale domates tarlası veri kümesi ile derin öğrenme ağlarının eğitiminde en iyi sonuca, %99.78 doğrulama doğruluğu ile Inception ResNet v2 ağı ile ulaşılmıştır. Karmaşık Çanakkale domates tarlası veri kümesi ile derin öğrenme ağlarının eğitiminde en iyi sonuca, %92.92 ile GoogleNet ağı ile ulaşılmıştır. Ayrıca yapılan denemeler sonucunda derin öğrenme ağlarının performans metrikleri incelenmiştir. Bu incelemeye göre; AlexNet, ResNet-50, Inception v3 ve Inception ResNet v2 gibi derin öğrenme ağlarının eğitim maliyeti olarak yüksek eğitim süresine ve model boyutuna sahip olduğunu tespit edilmiştir. Özellikle veri boyutu büyüdükçe, eğitim süresinin de bire bir oranda arttığı belirlenmiştir. Yüksek eğitim maliyetine sahip derin öğrenme ağları arasından en iyi sonuç veren Inception v3 ağının eğitimi; Tiny-imagenet veri kümesi üzerinde 7.5 saat, Plantvillage veri kümesi üzerinde yaklaşık 4 saat, temel Çanakkale veri kümesi üzerinde 5 dakika ve karmaşık Çanakkale veri kümesinde ise 20 dakika sürmüştür. Eğitilen Inception v3 modelinin ortalama model boyutu ise yaklaşık 260 MB'dır. Diğer taraftan SqueezeNet, MobileNet v1, MobileNet v2 ve GoogleNet gibi derin öğrenme ağlarının ise eğitim maliyeti olarak düşük eğitim süresine ve model boyutuna sahip olduğunu tespit edilmiştir. Benzer şekilde veri boyutu büyüdükçe, eğitim süresinin de bire bir oranda arttığı belirlenmiştir. Düşük eğitim maliyetine sahip derin öğrenme ağları arasından en iyi sonuç veren MobileNet v1 ağının eğitimi; Tiny-imagenet veri kümesi üzerinde 75 dakika, Plantvillage veri kümesi üzerinde yaklaşık 2.5 saat, temel Çanakkale veri kümesi üzerinde yaklaşık 3 dakika ve karmaşık Çanakkale veri kümesinde ise yaklaşık 12 dakika sürmüştür. Eğitilen MobileNet v1modelinin ortalama model boyutu ise yaklaşık 27 MB'tır.
3D-printed actuator-based beam-steering approach for improved physical layer security in visible light communication

(Graduate School, 2022-09-05) Erdem, Mehmet Can ; Ferhanoğlu, Onur ; 504201223 ; Electronics Engineering

In this thesis, the design, manufacturing and implementation of a 3D-printed lens scanner-based beam-steering are presented for use in visible light communication (VLC) applications. The scanner, measuring 5 x 5 cm, is designed for low-cost 3D printing with fused deposition modeling using polylactic acid (PLA). The scanning is facilitated through electromagnetic actuation of the lens frame, carrying a conventional 25 mm lens in two nearly orthogonal directions. The serpentine spring that connects the lens frame to the external frame is tailored to offer similar spring constants in the directions of actuation, and minimal (< 1.5 mm) sag due to the mass of the lens. The manufactured actuator was integrated on a miniaturized VLC test-bed (70 cm x 40 cm x 40 cm). Using the test-bed, the applied voltage vs. beam displacement behavior of the actuator was characterized in the lateral plane, and beam-steering on a moving target was demonstrated with face-recognition feedback. The proposed scheme was targeted to offer an improved security measure in VLC through tracking the legitimate receiver (i.e. via face recognition) and using the feedback to steer the focused light onto the targeted device. The joint use of focusing and steering features allows for the legitimate receiver to roam within the room while enjoying the improved secrecy due to focused light. The secrecy capacity for the demonstrated approach was also calculated, which compares favorably to a number of jamming, spatial modulation and beam-forming counterparts. The presented actuator can be used with larger room dimensions, yet up-scaling to larger illumination units will require the use of a lens having a smaller focus to achieve a larger total steering angle. This thesis is composed of five different chapters. The concepts of visible light communication and light fidelity (Li-Fi) are introduced with a thorough literature review in the first chapter, while the techniques used in the thesis are also defined and presented. In the second chapter, the design of the actuator is described through definite computer-aided design (CAD) models and finite element analysis (FEA) simulations, while the experimental setup is also presented. Meanwhile, the demonstrations and the measurement results from the beam-steering operation of the actuator are presented in the third chapter. Then, the discussion section, based on the secrecy improvement through the use of the actuator and the up-scaling of the actuator to real-world dimensions, is presented in the fourth chapter. Finally, the fifth chapter presents the conclusions and further future work based on the actuator. Also, the details regarding the experiments conducted in Chapter 3, some of the designs of the actuator that were changed in order to obtain the final prototype and some discussion based on the mechanical stress on the actuator caused by the weight of the lens are presented in the Appendix section.

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Çıkarma tarihi ile LEE- Elektronik Mühendisliği Lisansüstü Programı'a göz atma

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