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ÖgeAnalysis of signal processing algorithms for detection of human vital signs using uwb radar(Graduate School, 2024-05-07)Detection of human vital signs using ultrawideband radar systems has been a popular research topic amongst researchers since the 2000s. The detection and monitoring of human vital signs in free space or through obstacles such as walls or debris using radar systems are defined as bio-radiolocation. Detecting human vital signs through a robust clutter such as concrete walls using radar technology is possible. This technology is known as Sense Through Wall Radar (STWR) or Through Wall Radar (TWR). The applications of human vital signs monitoring utilizing radar are wide and grouped in two major fields: civil and military applications. Breathing and heart rates are the principal vital signs of the human body. Breathing and heartbeat frequencies are varied between 0.2-0.6Hz and 0.8 -2.5Hz, respectively. While breathing, the human chest area expands and contacts periodically. Human breathing/heartbeat movements draw a sinusoidal mathematical model, and this model is a signature of human vitality and the presence of human beings. These tiny movements up to centimeters in radar distance are observable thanks to ultrawideband technology. Ultrawideband(UWB) radars are utilized between 3.4 GHZ and 10.6 GHZ, with a band ratio of 1.29-7. This standardization is made by the Federal Communications Commission (FCC). UWB radars have improved target range accuracy and high range resolution, enabling target classification, are robust to interferences such as rain and mist, and have reduced radar dead zones. In addition to the properties mentioned earlier of UWB radars, they are non-ionizing, non-intrusive, and contactless. The non-contact and non-ionized property of UWB radar systems makes them great candidates for monitoring human vital signs in biomedical fields. Sleep monitoring (Sudden Infant Death Syndrome, Obstructive Sleep Apnea Syndrome), analysis of the physical performance of the athletes, veterinarian monitoring, and animal study are examples of these systems' civil and biomedical applications. The contactless measurement technique also enables monitoring of border zones and enemy territories, such as buildings, which is attractive for defense applications. Detecting human victims under debris after natural disasters such as earthquakes using UWB radar systems is helpful for search and rescue teams in the field. In light of the increasing aging population worldwide, UWB radar systems can monitor the activities of older adults, such as walking, falling, breathing, etc. These systems are widely known as Ambient Assisted Living(AAL). Thus, UWB radar systems are not only used for detection and monitoring human vital signs but also for classifying human gestures and movements. The operational specifications of UWB radar systems determine their performance. Thus, engineers seek solutions focusing on time, energy, bandwidth, and space. Higher bandwidths have better range resolution. The longer ranges are obtained with maximized energy. The positioning of antenna systems requires area. Regarding such tiny movements of human breath and heartbeat, ranging accuracy and space budget are crucial. The penetration through heavy clutters with longer ranges requires maximized energy. Moreover, the UWB radar performance is vulnerable to external noises and propagation effects due to earth curvature, atmosphere, and interference. Thus, analyzing the selection of UWB radar operational parameters for detected human vital signs is one of the research topics in the field. The UWB radar accuracy is measured via reference sensors to validate radar operation. Contact-based and non-contact systems are used. Electrocardiography, photoplethysmorgy, and chest belt sensors require contact with human tissues. Lidar and cameras are contactless techniques like UWB radars to analyze human vital signs. However, they suffer from environmental lightning. Electromagnetic tools are also used to model human vital signs. However, they are computationally heavy and complex. Thus, the presence of a simple, realistic, and cost-free vital sign reference system is a gap in the literature. Detecting human vital signs using UWB radars under the debris is an intricate problem for the researchers. The radar specifications, such as antenna geometry, radar type, bandwidth, and system power, are significant. Plus, after data collection in debris, the variational signal processing methods are utilized to enhance weak target returns. The first step is to suppress the clutter and debris in this case. The surrounding environment also affects the UWB radar data and makes additional contributions. Thus, the clutter type is modeled as time-varying and independent from time. Mean Removal, Frame Differencing, Loop-back Filtering, Linear Trend Subtraction, Principal Component Analysis(PCA), and Singular Value Decomposition (SVD) are the well-studied clutter reduction techniques in the literature. Time-frequency visualization of radar breath signals is handled via the most fundamental technique, the Fast Fourier Transform, or advanced techniques such as Hilbert Huang Transform and Short Time Fourier Transform. Hilbert Huang Transform and Short Time Fourier Transform are worthwhile while analyzing more complete scenarios such as additional movements. The feature analysis of these movements is significant for machine learning researchers who classify the movement types. In this study, we studied signal processing algorithms on radar human vital signs. The earthquake in Hatay and Kahramanmaraş in 2023, past pandemics, and a growing number of older adult populations motivated the thesis. Data collection regarding the gaps in literature was the central part of the study. We collected seven data types focused on cluttered zones, body movements, human/radar orientation, and simulation data. While collecting the data, we noticed a lack of publicly available data and the rapid process needed in medical and rescue radars. Thus, we shared our data on Mendeley Data and published its paper. We also shared fundamental signal processing algorithm analysis in this dataset to detect human breath signals under the table. In the remaining part of the studies, we focused on signal processing algorithms and analysis results. We analyzed the dataset using clutter reduction techniques and time-spectral analysis techniques. We presented detailed data performance analysis outcomes. Our studies on the effects of body movements on radar breath data were published in two international conferences. We developed a novel UWB radar breath simulator based on the electromagnetic properties of human tissues. Finally, we presented a brief conclusion.
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ÖgeKatkılı NiFe2O4 polimer tabanlı mikrodalga yutucuların frekans seçici malzeme tasarımı(Bilişim Enstitüsü, 2019-02-07)Haberleşme endüstrisindeki olağanüstü büyüme mikrodalga yutucu malzemelere olan ilginin artmasına neden olmuştur. Son zamanlarda modern haberleşme sistemleri yüksek frekanslara doğru kaydığı için yüksek frekanslarda kullanılmaya uygun yutucu malzemelere olan ilgi ve gereksinimde doğal olarak artış göstermektedir. Kablosuz iletişimin hızlı ilerlemesi neticesinde mikrodalga yutucu malzemelere olan ilgi radar sistemleri ve askeri uygulamalar gibi özel alanlar dışındaki uygulamalarda da oldukça dikkat çekici hale gelmiştir.Kullanımı giderek yaygınlaşan elektronik aygıtlardan yayılan sinyallerin oluşturduğu elektromanyetik kirliliğin insan sağlığı ve çevre üzerine pek çok olumsuz sonuçlar ortaya çıkardığı da günümüzde bilinmektedir. Bu sorunları aşmak ve elektromanyetik etkileri en aza indirmek, radar, uzay teknolojisi, telekomünikasyon, yerel alan ağları, askeri ve iletişim teknolojilerinde güvenliği sağlamak amaçlı olan yutucu malzemeler ve ekranlama etkinliğine sahip malzemeler üzerinde yapılan çalışmalarda ayrıca devam etmektedir. Yutucu malzemeye gelen sinyalin geldiği yöne yansımaması ve aynı zamanda iletim sağlamaması gereklidir. Bunun için sinyalin malzeme içinde veya üzerinde emilim yapması gerekmektedir. Normalde yansıma katsayısı minumum seviyeye ulaştığında en düşük yansıma kaybı elde edilir, yani gelen elektromanyetik dalgaların hiçbiri geri yansımamaktadır. Prensip olarak, bir elektromanyetik yutucu kaplamanın rolü, düşük yansıma sağlaması ve gelen elektromanyetik dalgalar için yüksek bir yutulma sağlamasıdır. Elektromanyetik dalga yutucu malzemelerin değeri ne kadar ince bir tabaka ile ne kadar geniş bir frekans aralığında yutma işlemini yaptığı ile alakalıdır. Malzemeye gelen elektrik ve manyetik bileşenleri olan birbirlerine dik şekilde hareket eden elektromanyetik dalganın elektrik bileşeni malzemenin dielektrik özellikleri tarafından yutulurken diğer bileşen olan manyetik bileşen ise manyetik özellik tarafından yutulur böylece bu iki bileşen kaybolunca malzeme ideal yutucu malzeme olur. Mikrodalga malzeme içine girdikten sonra malzeme kalınlığı boyunca zayıflatılmalı ve ısıya dönüştürülmelidir, bu durumda malzemeye gelen dalgalar yutularak geri yansımayacaktır. Manyetik ve dielektrik özellikleri nedeniyle NiFe2O4 genel formülü ile verilen spinel ferrritler sahip oldukları ilginç özellikleri nedeniyle son yıllarda yoğun bir şekilde bilgi depolama sistemleri içindeki uygulamalar, manyetik sıvılar, manyetik toplu çekirdek, yüksek frekans aralığında çalışan mikrodalga veya radar yutucu malzemeler (RAM), yüksek frekanslı cihazlar için araştırılmıştır, NiFe2O4 yapısındaki spinel ferritler manyetik kayıplarının ve dirençlerinin yüksek olmasından dolayı elektromanyetik dalga yutucu olarak kullanılabilmektedir, ayrıca spinel ferritler manyetik kayıt ortamı, manyetik akışkanlar, katalizörler, manyetik rezonans görüntüleme (MRI), mikrodalga yutucular, sensörler ve pigmentler gibi uygulama alanlarında da öne çıkan malzemelerdir. Ferritlerin özellikleri, kimyasal bileşimine, mikroyapısına, sinterleme parametreleri ile katkılanan iyonun konumuna ve katkı oranına bağlı olarak değişik özellik göstermektedir. Yapılan çalışmada NiFe2O4 ferrit bileşiminde Ni yerine Mo, Tb, Ta ve Hf, Fe yerine V, Cu farklı oranlarda yer alan katı eriyiği şeklinde ilave edilerek tek fazlı katkılı NiFe2O4 ferritleri oksitlerin karışımı yöntemiyle üretilmiştir. Başlangıç oksitlerinin miktarları Ni1-xMoxFe2O4, Ni1-xTbxFe2O4, Ni1-xTaxFe2O4 , Ni1-xHfxFe2O4 , NiFe2-xVxO4, NiFe2-xCux stokiyometrik kompozisyonlar baz alınarak hesaplanmıştır. Her bir katkının ana yapı (NiFe2O4) içerisinde yapıyı bozmadan katkılanabileceği miktar olarak tarif edilen çözünürlük limiti X-ışınları toz difraktometresi kullanılarak saptanmıştır. SEM sonuçları XRD sonuçlarını teyit etmektedir. 1200-1500 °C aralığında sinterlenen katkılı tek fazlı NiFe2O4 ferrit malzemelerin manyetik özellikleri belirlenmiştir. Oluşturulan katı eriyiklerde katkı tür ve oranlarının ferrit seramiğinin manyetik ve ekranlama etkinliğine (shielding effect) olan etkileri ayrıca belirlenmiştir. Özellikler açısından belirlenen optimum parametrelere göre katkılı NiFe2O4 ferritleri polianilin tabanlı olarak kompozit olarak üretilip özellikleri karakterize edilmiştir. Polianilin-NiFe2O4:V, Polianilin-NiFe2O4:Tb, Polianilin-NiFe2O4:Cu, Polianilin-NiFe2O4:Hf, Polianilin-NiFe2O4:Ta, Polianilin-NiFe2O4:Mo farklı katkı oranlarında sıcak presleme ile üretilmiştir. Anilin / Ni ferrit ağırlık oranı 1/1, 3/1 olarak değiştirilerek mikrodalga ekranlama etkinliğine sahip kompozitler epoksi reçine kullanılarak üretilmiştir, üretilen kompozitler XRD, SEM ve VSM ( titreşen örnek magnetometresi ), FTIR,Vector Network Analyzer (VNA (Two-Port,R & S FSH-K42)) kullanılarak karakterize edilmiştir. Polianilin-NiFe2O4: V, Polianilin-NiFe2O4:Tb, Polianilin-NiFe2O4:Cu, Polianilin-NiFe2O4:Hf, Polianilin-NiFe2O4:Ta, Polianilin-NiFe2O4:Mo kompozitlerinin mikrodalga ekranlama etkinliği performansları 0-8 GHz aralığında ölçülmüş ve mikrodalga ekranlama etkinliğine sahip malzemeler olarak kullanım potansiyelleri incelenmiştir.
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ÖgeDirectional wide band printed monopole antenna for use in microwave breast cancer imaging(Institute of Informatics, 2012-06-07)Breast cancer is the most common cancer in women. Detection of small breast lesions by mammography screening facilitates the cancer treatment by noninvasive techniques. Recently, new therapies than traditional surgery have been explored to satisfy these demands. The physical basis for breast cancer detection with microwave imaging is the difference in dielectric properties of normal and malignant breast tissues. Microwave imaging involves illuminating the breast with an ultra-wideband pulse from a number of antenna locations, then synthetically focusing reflections from the breast. The detection of malignant tumors is achieved by the coherent addition of returns from these strongly scattering objects.Radar-based microwave imaging techniques have been proposed for early stage breast cancer detection. Radar-based microwave breast imaging approaches involve illuminating the breast with an ultra-wideband pulse of microwaves and detecting reflections. The reflections are then processed to create images that indicate the presence and location of tumors in the breast. A key component of these systems is the antenna that is used to radiate and receive the ultra-wideband pulses. So the antenna design requirements for use in near field near surface measurement applications, such as radar-based microwave breast cancer imaging are as follows: radiation of ultra-wideband signal to transmit short pulses, size of the antenna on the order of a few centimeters to selectively illuminate and permit scanning, an optimum half power near-field beam width( HPBW) to avoid smearing of the scatterers that occurs if the field of view of each antenna is too broad, and finally a good impedance matching across the entire band, This ensures that most of the energy is transmitted. In order to decrease the HPBW of an antenna we have to increase the directivity of the antenna in a desired direction. Nevertheless, most of the wide band and UWB antennas like planar monopoles, which are in use, have almost Omni-Directional radiation pattern.Directivity can be achieved if the antenna is large in a desired direction, such as Horn or Vivaldi antennas. Printed disc monopole antennas with an L-shaped or parabolic-shaped ground plane are introduced as another type of directional antennas. In these antennas it has been shown how partial ground optimization influences the antenna?s performance, in maximizing the directivity and gain of the antenna. These kinds of directional antennas are similar to the UWB type Omni-Directional monopole antennas, where it is shown the effect of ground plane on obtaining the desired directional characteristics of the antenna.This Thesis presents a new design of directional wide band monopole antenna with parabolic-shaped ground plane. Ground plane of the antenna consists of a symmetrical parabolic curve, which its axis extended along the direction of the substrate?s diagonal. In order to accomplish high gain and directivity, axis of parabola in the ground plane is extended throughout the direction of square substrate?s diagonal that maximizes the capability of symmetrical ground plane as a reflector. The directivity of the antenna is further improved by inserting parabolic-shaped slots at the corners of ground plane. The second edge of the ground plane which is created by inserting the slots, behaves as an additional reflector which cause to increase in the gain and directivity.Then, the presented planar antenna is composed of a disc-monopole fed by a 50? microstrip line printed on a FR4 substrate. Simulation and measurements show that the proposed antenna has stable directional radiation pattern and higher gain compared to the previous directional monopole antennas. Impedance bandwidth of the antenna covers the frequency range of 4-9 GHz. Measured HPBW is among the degrees 54-22 in the same range of frequencies. In comparison with conventional antennas with a similar structure, gain of the antenna is improved between 1.1 and 3.1 dBi among 4-9 GHz. HPBW of the antenna is also between 5 and 15 degrees through the bandwidth .Results confirm the good characteristics for use in radar and microwave Breast cancer imaging applications where high resolution is required. For example, at 8.5 GHz, measured HPBW of the antenna is decreased from 38 degrees to 23 degrees (mentioned in the result section), which confirms a 40 % decrease in HPBW of the antenna (simulated HPBW is 26 = 33 % improvement). That is very important in order to increase the resolution of a radar system.As an additional attempt, another novel compact directional monopole antenna in microstrip technology is also presented. Dimensions of this antenna are considerably miniaturized in comparison with conventional directional antennas. The main effort is to convert an Omni-directional radiation pattern of a compact monopole antenna to the desired directional radiation pattern, by using a novel ground plane, and a parasitic element. The ground plane and parasitic element are accurately designed in a way that make the surface currents of radiating elements to move toward the desired direction, which increase the radiation density in the preferred direction and also decrease the radiation intensity in the opposite sides. Simulations confirm a good directional characteristic of the antenna at the frequencies between 5 and 9 GHz. Gain of the antenna is increased over 5 dBi at the desired frequencies. Reflection coefficient bandwidth of the antenna covers the frequencies among 5-9 GHz. Miniaturized size and an acceptable directional characteristic of the antenna make it possible to use it in the microwave imaging systems and radar applications.
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ÖgeAntenna and measurement system for microwave imaging of breast tumors(Institute of Informatics, 2015)With the increasing demand for better medical imaging technologies, different medical screening procedures become a research topic for scientific community. One of the important challenges in today's medical imaging is surely the early detection of breast cancer. The breast cancer is one of the very dangerous health threat for women. This disastrous illness is observed approximately one in eight women by the age of ninety years old. The likelihood of successful treatment increases with early detection of breast cancer increases. Up to now, X-ray tomography is the golden standard for characterizing and detecting the breast cancer. In contrast to this fact, X-ray mammography has significant disadvantages. These disadvantages trigger a search for different imaging modalities, which can be integrated with currently available imaging technologies. Microwave imaging is one of those newly emerging solutions. The use microwaves in the early detection of breast cancer is motivated by several reasons. First of all, it is shown that the electrical properties of the malignant and normal tissues are substantially different, which can be easily revealed by microwave imaging. Moreover, microwaves can easily penetrate into breast tissue at a few GHz ranges. Considering that the dimensions of the breast is comparable with the wavelength at those frequencies, the malignancies can be detected from the scattered field by means of nonlinear inverse scattering algorithms. Nowadays, there are many different studies to design microwave imaging systems for the early detection of the breast cancer. An inevitable part of these systems is the nonlinear imaging methods. With the recent developments in computer technology and the newly introduced efficient algorithms, these methods are now employed in any microwave imaging system. However, the quality of reconstructed images produced by these methods is closely connected with the scattered field data that is acquired by the microwave antennas. Hence, one of the most important parts of the microwave imaging systems is the transceiving antennas. It is shown that, regardless of the method in the hand, the resolution of the produced images increases with the increasing signal-to-noise ratio (SNR) and with the increasing sampling density of the field. To increase SNR, the designed antenna must have higher gain levels together with a lower back-to front ratio level; whereas the sampling density of the field increases when the dimensions of the antenna gets smaller. Furthermore, the microwave imaging methods require certain preprocessing steps, which accept only a single polarization of the incident field as input. Thus, the designed antennas must be highly linearly polarized. Finally, the microwave imaging of the malignancies is a highly ill-posed inverse problem. Thus, the frequency diversity in the scattered field data must be as high as possible. Consequently, today's microwave breast cancer imaging systems require high gain, linearly polarized, wide-band and compact antennas as their scattered field sensors. In this context, the first contribution of this thesis is the design of a cavity-backed Vivaldi antenna (CBVA) for microwave breast measurements. The design criteria for the antenna is shaped by the requirements of the free-space measurement scenario where the receiving and the transmitting antennas are rotated by a mechanical scanner. Later, various breast phantom measurements is conducted with the CBVA to reveal its feasibility for microwave tomography. As the second contribution, a novel Corrugated Vivaldi antenna (CVA) is proposed. The main idea is opening corrugations on the edge of the antenna to decrease the induced currents, which can degrade the performance. Doing so a design with better properties such as higher gain, smaller beam width, lower back-to-front ratio is obtained. The characteristics of the obtained CVA is measured in a detailed manner. Furthermore, the imaging performance of the introduced design is compared with a generic Vivaldi antenna (VA) of the same size. For this purpose, several experimental configurations are prepared in an anechoic environment and scattering parameter (S-parameter) measurements are obtained for those setups by means of the both antennas. Acquired S-parameters are then employed in a recently proposed qualitative imaging method, the S-parameter based Linear Sampling Method (S-LSM), which is a more suitable form of Linear Sampling Method (LSM) for real world applications. Experimental results show that the proposed design performs better than VA in such real world microwave imaging problems.
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ÖgeCBS tabanlı denizel mekânsal planlama sistemi ile denizüstü rüzgâr santrallerinin değerlendirilmesi: Kuzey Ege örneği(Lisansüstü Eğitim Enstitüsü, 2021)İçinde bulunduğumuz yüzyıl daha önce benzerine rastlanmamış bir enerji ihtiyacını beraberinde getirmiştir. Bunun temel sebebi, hiç kuşkusuz ki sanayileşme ve endüstriyel faaliyetlerin öngörülemeyen gelişimidir. Teknolojinin hızı, süreci beslemiş, dolayısıyla kullanılan enerji kaynaklarının azalması ve tükenmesi konusu günümüzün en önemli sorunlarından biri haline gelmiştir. Gereksinim duyulan enerjinin tükenebilir değil, yenilenebilir ve sürdürülebilir olması ile enerji kaynaklarının üretilebilmesi konusu birçok disiplinin enerji konusundaki çalışmalarında önemli bir araştırma alanı olmuştur. Özellikle, temiz ve tükenmeyen enerji olan rüzgâr enerjisi pek çok çalışmanın ve uygulamanın konusudur. Rüzgâr enerjisinden yararlanma konusundaki gelişmeler ve buna bağlı olarak çalışmaların ve yatırımların dünyada ve Türkiye'de paralel olduğu görünmektedir. Türkiye'nin üç tarafının denizlerle çevrili olması, denizüstü rüzgâr santrallerinden yararlanabilme avantajını ön plana çıkartmaktadır. Türkiye denizlerinin jeopolitik önemi ve özellikle uluslararası anlamda kritik öneme sahip Ege Denizi'nin, deniz üstü rüzgâr santralleri konusundaki potansiyelinden yararlanmak için çok yönlü mekânsal analizlerin gerçekleştirilmesi önemli ve gerekli görülmektedir. Bu çalışmayla Türkiye'de, enerjide dışa bağımlılığı azaltmak ve yenilenebilir enerjiden daha fazla yararlanmak amacıyla ortalama rüzgâr potansiyeli yüksek, ancak, kısıt alanlarının da çok fazla olduğu Kuzey Ege Denizi'nde, rüzgâr enerji türbinlerinin konumlandırılacağı bölgelerin belirlenmesi amaçlanmıştır. Bu bağlamda, çalışmanın birincil hedefi: Türkiye'nin Kuzey Ege deniz sahasında, potansiyel rüzgâr türbin sahalarının yer tespitinin yapılması ve uygunluk alanlarının belirlenerek, bölge için Coğrafi Bilgi Sistemleri (CBS) tabanlı bir Denizel Mekânsal Planlama Sistemi oluşturmaktır. Bu kapsamda, alternatif bölgelerin belirlenerek sıralandığı, CBS ve çok ölçütlü karar verme tekniklerinin kullanıldığı bir karar modeli uygulanmıştır. Çalışmanın ikincil hedefi ise, Kuzey Ege Denizi açık deniz türbinleri kurulumu için ideal alanların enerji verimliliğini ortaya koymak için enerji ve ekserji analizleri gerçekleştirmektir. Kuzey Ege Denizi gibi stratejik öneme sahip, uluslararası denizcilik seyir hat yoğunluğu oldukça fazla olan, çevresel hassasiyeti yüksek bir deniz alanında; denizel mekânsal planlamanın gerekliliğine göre oluşturulmuş CBS veri tabanlı bütünleşik bir uygulama ile (ÇÖKA yöntemleri ile uygun yerleri belirleme, uygun yerlerin sıralanması ve son adımda çalışma bölgelerinin enerji ve ekserji verimlilik analizi) doğruluğu ve uygunluğu yüksek açık deniz rüzgar türbinleri potansiyel alanları bu tez çalışmasının konusudur.