LEE- Telekomünikasyon Mühendisliği-Yüksek Lisans

Bu koleksiyon için kalıcı URI

http://hdl.handle.net/11527/19469

Gözat

Konu "5G" ile LEE- Telekomünikasyon Mühendisliği-Yüksek Lisans'a göz atma
  • Öge
    5G uygulamaları için dairesel polarizasyonlu ve metayüzeyli mikroşerit MIMO anten tasarımı
    (Lisansüstü Eğitim Enstitüsü, 2023) Koçer, Mustafa ; Günel, Murat Tayfun ; 782952 ; Telekomünikasyon Mühendisliği Bilim Dalı
    Bu tez çalışmasında, 6 GHz altı 5G frekans spektrumuna yönelik n78 bandı olarak adlandırılan 3.3-3.8 GHz frekans aralığında 4x4 çok girişli çok çıkışlı bir anten tasarımı hedeflenmiştir. Öncelikle çok girişli, çok çıkışlı anten tasarımında kullanılacak olan mikroşerit anten tasarımı gerçekleştirilmiştir. Mikroşerit antenin dairesel polarizasyonda çalışması için kare yama tercih edilmiştir. Tercih edilen kare yamanın köşelerinde sol el dairesel polarizasyona yönelik kesik daire ve kesik üçgen kullanılmıştır. Yapılan tasarımlara göre köşelerinden kesik daire kullanılarak yapılan mikroşerit anten tasarımı kesik üçgen kullanılarak yapılan tasarıma göre daha iyi sonuç vermiştir. Sol el dairesel polarizasyona yönelik köşelerinde kesik daire oluşturularak tasarlanan mikroşerit antenin performansını artırmak için üzerine hava boşluğu olmadan 4x4 metayüzey yerleştirilmiştir. Böylece metayüzeyin oluşturduğu yüzey dalgalarının kesim frekanslarında mikroşerit anten rezonansa girmiştir. Mikroşerit antenin istenilen yansıma katsayısı ve eksenel oranı aşağı frekansta (3.4 GHz) iken metayüzeyin yüzey dalgaları yukarı frekanslardadır (3.9-4 GHz). Bu sayede anten geniş bantta çalışmaktadır. Kullanılan metayüzey sayesinde FR-4 alttaş malzemesi ile tasarlanan bu antenin verimliliği, kazancı artmıştır ve geniş bantta dairesel polarizasyonda çalışması sağlanmıştır. Ayrıca mikroşerit yama antenin ortasında çapraz yarık oluşturularak metayüzeyli mikroşerit anten daha düşük yansıma katsayısına sahip olmuştur. Metayüzeyli mikroşerit antenin tasarımında kullanılan alttaş malzemesinin kalınlıkları ve kullanılan alttaş malzemesinin performansa etkileri incelenmiştir. Ayrıca tasarımda kullanılan 4x4 metayüzeyin köşelerinden kesik daire şekli oluşturularak antenin dairesel polarizasyon bant genişliği artırılmış ve daha geniş bantta yüksek kazanç elde edilmesi sağlanmıştır. TLC-32 alttaş malzemesi kullanılarak tasarlanan metayüzeyli mikroşerit anten ile 6 GHz altı 5G uygulamalarına yönelik 3.3-3.8 GHz' te dört kapılı (iki kapı sağ el dairesel, iki kapı sol el dairesel polarizasyon) olacak şekilde MIMO anten tasarımı gerçekleştirilmiştir. Tasarlanan MIMO antenin 1. ve 3. kapıları sol el dairesel polarizasyona yönelik iken 2. ve 4. kapıları sağ el dairesel polarizasyona yöneliktir ve her kapı kendi aralarında 90° döndürülerek tasarlanmıştır. MIMO antenin izolasyonunu artırmak için MIMO antenin ortasında alttaşa entegreli dalga kılavuzu yapısı kullanılmıştır. Buna ek olarak mikroşerit anten katmanına ve metayüzey katmanına parazitik elemanlar eklenmiştir. Böylece tasarımı gerçekleştirilen MIMO anten yüksek izolasyonlu ve kapılarının hepsi yüksek kazançlı olacak şekilde dairesel polarizasyonda çalışmaktadır.
  • Öge
    A compact two stage GaN power amplifier design for sub-6GHz 5G base stations
    (Graduate School, 2023) Türk, Burak Berk ; Savcı, Hüseyin Şerif ; Şimşek, Serkan ; 809122 ; Telecommunication Engineering Programme
    Both commercial and military systems use wireless communication networks. The range of applications is wide, including radar, mobile communications, Wi-Fi, SATCOM and many more. They all have different requirements and different solutions to meet their needs. The development of mobile communications began with 1G in the 1970s, and new generations have found their place in the radio communications market. In 2019, 5G New Radio has started to be expanded worldwide with higher data rate, wider frequency bands, lower latency features. Moreover, there are more frequency bands are available for 5G New Radio. These are called sub-6GHz and mmWave. As the name suggests, the sub-6 GHz frequency bands are below the 6 GHz frequency bands, including the bands of the previous generation. On the other hand, mmWave frequency bands are above 24 GHz. With the goal of low latency, engineers are developing new solutions for the next generation of base stations. One solution is to deploy smaller base stations more frequently than traditional macro base stations. These small cell base stations are called Micro, Pico, Femtocells. As the size of base stations has decreased, the transmitters and receivers of the cells require new technological developments. As the transmitters contain power amplifiers, they are known to dissipate significant amounts of DC power and require appropriate thermal protection. Also, with the increasing demand for small cells, the size of the transmitters must also be considered, along with the nuisance of heat. One of the most important component of the transmitters is power amplifiers. They are the last element of the transmitter before the antenna and amplify the RF power using DC power. In this work, the power amplifier is studied. The size of the power amplifiers play important role for the 5G New Radio small base station cells. Also, due to the size of power amplifiers being small, the power density and thermal conductivity managements are examined. GaN transistors gained popularity over GaAs and Si semiconductor technologies since their thermal conductivity is better and their power density is higher. They are also capable of amplifying higher power levels and have broader bandwidths. For these reasons a compact GaN HEMT power amplifier module is designed to meet the requirements of 5G small cell base stations. For thermal reasons, the efficiency of the power amplifier is crucial. The traditional power amplifiers are divided into classes that is determined by their bias points. These are Class A, Class B, Class C and Class AB. Class A is theoretically the least efficient and Class C is the most efficient. Also, the linearity is important factor in telecommunications because of complex modulation systems. Class A is the most linear and Class C is the least linear of all classes. As a result of this compromise, our power amplifier module operates in Class AB, which balances efficiency and linearity. In this work, a compact two-stage power amplifier module is designed with high gain, high linearity and high efficiency. 2 bare die GaN HEMT transistors are used with 0201 packaged lumped components for matching circuits on a laminate PCB. The PA module measures 10x6 mm. Given these dimensions, the alternative design option is MMIC technology, but the cost of a GaN-based wafer is significantly higher than our solution. A large signal model of the transistor is used and simulated with the EM co-simulation. The simulations are resulted as the output power level of 5W with 0.1 dB gain compression at the center frequency 3.5 GHz. The stability of the PA module is secured with series resistors. The designed power amplifier module is manufactured and implemented with the die transistors and components by using die bonder and wire bonder machines. Small signal and large signal measurement setups are prepared and the device is tested. Due to the mesh settings the designed power amplifiers matching circuits are shifted. 18.5 dB gain is measured with 30% PAE at the output power level of 2W. The simulations are repeated with accurate EM simulations and the results are matched.
  • Öge
    A doherty power amplifier for 5G applications
    (Graduate School, 2023) Konanç, Hasan ; Savcı, Hüseyin Şerif ; Akıncı, Mehmet Nuri ; 900834 ; Telecommunication Engineering Programme
    The ever-increasing need for high data rates and low latency steered modern communication systems toward massive MiMo architectures. In this architecture, each antenna element requires its amplifier unit. Smaller cell sizes and more user service have forced a significant increase in antenna elements, so the Power Amplifier units. Each amplifier is a substantial contributor to the power consumption budget. Therefore, efficiency is a primary concern in Power Amplifiers of cellular infrastructure systems. This study focuses on an architectural solution for Power Amplifier efficiency by demonstrating a Doherty PA (DPA) design in a widely used 5G sub-6GHz band of n78. This thesis focuses on the efficient RF output power generation of 5G base stations from an architectural perspective. A Doherty Power Amplifier is designed using for n78 5G band that is prioritized for the upcoming deployment. The design is optimized for an operation between the 3.6 - 3.8 GHz frequency band. The output power of 43 dBm (20 W) was obtained by using two of the 10W GaN HEMT transistors and a drain efficiency of 73% was obtained. The Doherty region starts at 38 dBm output power which allows an efficient operation with 6 dB power back off. A drain efficiency of up to 53% was obtained in the Doherty region and a gain of 10 dB is obtained over the entire band. The requirement of unconditional stability at all frequencies under small and large signal conditions demands a thorough analysis at different phases of design. For multi – stage stability analysis, the Ohtomo approach was also utilized in this study, for its convenience of being based on S – parameters and not requiring access to the transistor's internal components. Nyquist method is used in Ohtomo approach. Nyquist method was applied for frequencies between 10 MHz and 10 GHz. As a result, the proposed DPA is stable because there is no loop gain surrounding the 1+ j∗0 point. The prototype of the proposed DPA was fabricated and real-time small and large signal tests were performed. During the tests, it was found that the prototype DPA did not work only in the desired frequency range of 3.6 - 3.8 GHz during the design period, and after the tuning process, Doherty drain efficiency characteristics were obtained in the frequency range of 3.2 - 4 GHz (n77 5G band). Accordingly, The output power of 41.6 dBm (approximately 15 W) was obtained by using two of the 10W GaN HEMT transistors and a drain efficiency of 67% was obtained. The Doherty region starts at 32 - 38.2 dBm output power, allowing an efficient operation with 0.5 - 7.8 dB power back off. A drain efficiency of up to 67 % was obtained in the Doherty region, and a gain of 3.5 - 7.9 dB was obtained over the entire band.