X–Ku bant güç bölücü tasarımı

X–Ku band power divider design

Tez No: 550364
Yazar: MEHMET BAL
Danışmanlar: PROF. DR. SELÇUK PAKER
Tez Türü: Yüksek Lisans
Konular: Elektrik ve Elektronik Mühendisliği, Electrical and Electronics Engineering
Anahtar Kelimeler: Belirtilmemiş.
Yıl: 2019
Dil: Türkçe
Üniversite: İstanbul Teknik Üniversitesi
Enstitü: Fen Bilimleri Enstitüsü
Ana Bilim Dalı: Elektronik ve Haberleşme Mühendisliği Ana Bilim Dalı
Bilim Dalı: Elektronik Mühendisliği Bilim Dalı
Sayfa Sayısı: Belirtilmemiş.

Özet

Teknolojinin gelişmesi ve dizi antenlerin günümüz teknolojisinde yerini almasıyla birlikte doğan ihtiyaçlardan birisi de dizi antenlere iletilecek gücün bölünmesi veya birleştirilmesidir. Bu ihtiyacı karşılayabilecek temelde iki farklı yapı ortaya çıkmaktadır. Bunlardan en sık kullanılanı mikroşerit yapılar, diğeri ise dalga kılavuzlarıdır. Bu tez kapsamında kılavuz ve mikroşerit yapılar incelenmekte ve bu yapıların karşılaştırılması yapılmaktadır. Mikroşerit yapılar gerek boyut gerekse maliyet açısından daha uygun olması nedeniyle ön plana çıkmaktadır. Özellikle ağırlığın ve boyutun sıkıntı yaratacağı platformlarda tercih sebebi olmaktadır. Mikroşerit yapılar üzerindeki çalışmalarla birlikte daha düşük maliyetlerle kompakt mobil cihazlar/sistemler üretilebilmektedir. Mikroşerit yapılarda en sık karşılaşılan iki tür güç bölücüsünden biri T jonksiyonlu güç bölücüsü ve diğeri ise Wilkinson güç bölücüsüdür. Her iki yapının da kendine özgü avantaj ve dezavantajları vadır. Güç bölücüsü karakteristiğine göre bazı parametreler değişiklik gösterebilir. Güç bölücüleri genellikle dizi antenlerde kullanılmaktadır. Radyo frekans teknolojisinin kullanıldığı tıp, haberleşme, endüstri ve askeri alanlarda mikroşerit yapılar kullanılabilir. Mikroşerit yapılar kompakt ve düşük maliyet sunduğu için maliyet ve minimalist tasarımlar açısından tercih sebebidir. Dalga kılavuz çözümü; güç bölücüler için stabil, üretim tolerası yüksek ve mikroşerit yapılara göre az kayıplı olması sebebiyle hala tercih edilmektedir. Dalga kılavuz çözümü en az kaybı sunmasına rağmen, kullanıldığı sistemler üzerinde entegrasyon boyutları nedeniyle sorun yaratmaktadır. Yine de sağladığı az kayıp nedeniyle, güç kaybına toleransı olmayan sistemlerde kullanılmaya devam etmektedir. Tez kapsamında mikroşerit T jonksiyonlu ve Wilkinson güç bölücüsünün ağırlık, boyut ve performans açısından avantaj veya dezavantajlarını ortaya koyacak şekilde benzetim ve üretim sonuçları değelendirilmiştir. Güç bölücüleri öncelikle HFSS programında simüle edilmiş ve elde edilen sonuçların iyileştirilmesi için optimize edilmiştir. Ortaya çıkan en iyi sonuçlara göre üretim yapılmıştır. Son olarak üretim ve simülasyon sonuçlarının karşılaştırılması yapılmıştır. Tezin ilk bölümünde mikroşerit yapılar ve güç bölücüler hakkında tearik bilgi verilmiştir. En önemli tasarım parametrelerinden biri olan güç bölücünün araya grime kaybını azaltmak için literatürde yer alan empedans uyumlayıcılar gösterilmiştir. Özellikle araya grime kaybını azaltırken aynı zamanda geniş frekansta çalışabilen bir güç bölücü tasarlamak için kullanılabilecek en iyi çözüm ortaya çıkarılmıştır. İkinci bölümde ise HFSS programında hazırlanan en basit T jonksiyonlu ve Wilkinson güç bölücü tasarımı yapılarak tasarıma başlanmıştır. Literatürde kullanılan empedans uyumlama yöntemleriyle gereksinimlere uygun olacak şekilde iyileştirmeler yapılmıştır. Son olarak parametrik optimizasyon yapılarak en iyi sonuçla prototip aşamasına geçilmiştir. Üretilen prototip cihazlar SMA konnektörlerle sonlandırılarak Keysight marka 10 MHz - 50 GHz aralığında ölçüm yapabilen bir network analizörde ölçüm yapılmıştır. Kıyaslama yapabilmek için ölçüm ve simülasyon sonuçları üst üste çizdirilerek konnektör ve lehimden kaynaklı kayıplar gözlemlenmiştir. Son bölümde, tasarım aşamasında görülmeyen fakat pratikte karşılaşılan problemlere, problemlerin çözümlerine yönelik önerilere ve tasarımların değerlendirilmesine yer verilmiştir.

Özet (Çeviri)

Considering today's technology trend, devices/systems are designed in a small and portable structure due to the fact that users always want to carry their possibilities with them. Therefore, all sub-systems and devices have the same compact structure. The power dividers in this thesis will be designed in a compact structure to be usable in today's technologies. Through the development of technology and the introduction of array antennas in today's technology, one of the needs is to divide or combine the power to be transmitted to the array antennas. There are basically two different structures that can provide this requirement. The most commonly used are microstrip structures and the otherone is waveguide. Power dividers are used in many areas where RF communication is used. With the help of the power dividers, it is possible to design the power of the RF signal to different ports in equal or different proportions to design according to the requirements. In particular, with the introduction of the array antennas, the distribution of the power of the RF signal emitted from a single source to feed the array antennas increased the importance of the power dividers. A power divider can basically be designed on two different structures. One of these structures is microstrip structures and the other is waveguides. The most suitable solution can be obtained with different architectures built on the appropriate structure according to the requirements. Within the scope of this thesis, power divider design with different topologies on microstrip structures and comparison of these power dividers with traditional power dividers will be included. The power dividers to be designed are intended to operate at X band and Ku band frequencies. Microstrip structures are more suitable for both size and cost. Especially in platforms where weight and size will cause distress are preferred Compact mobile devices/systems can be produced at lower costs with the work on microstrip structures. Two of the most common types of power divider in microstrip structures are the T junction power divider and the other is the Wilkinson power divider. Both structures have their own advantages and disadvantages. Some parameters may vary depending on the power divider characteristic. Power dividers are generally used in array antennas. Microstrip structures can be used in medicine, communication, industry and military areas where radio frequency communication technology is used. Microstrip structures are preferred for cost and minimalist designs because they provide compact and low cost. T Junction and Wilkinson microstrip structures in the conic structure is designed to expand the frequency band. In Wilkinson power splitters, it is tried to solve the isolation problem by using N-section resistive element. Within the scope of the thesis, similar methods are considered and optimum solution is targeted in the working frequency range. Waveguides RF signals are structures that provide the point-to-point transmission with minimal loss. It is possible to design the power dividers/couplers in the form of a waveguide. Because of the large structural dimensions of the waveguides, they are not preferred in compact systems. But due to the structure of the production infrastructure is not high cost. Waveguides are preferred in systems with low power loss tolerance due to the fact that they offer much less loss compared to microstrip structures. When the waveguides theory is considered, it starts to transmit wave after a certain cut frequency. In addition, different modes occur at different frequency values in the waveguide. It is undesirable for many modes to occur at the same time and therefore the waveguides are not used at the frequencies where other modes are being transmitted. Therefore, the operating frequency of the waveguides is narrow banded. In this thesis, the band width X and Ku band (6-15 GHz) are the frequencies. The waveguide solution is still preferred for power dividers because of its stable, production tolerant and low loss compared to microstrip structures. Although the guide offers the least loss of the solution, its integration on the systems it uses creates problems because of its size. However, due to the small loss it provides, it continues to be used in systems that do not tolerate loss of power. Within the scope of the thesis, the simulation and production results of the microstrip T junction and Wilkinson power divider have been evaluated in order to demonstrate the advantages or disadvantages in terms of weight, size and performance. Power dividers are primarily simulated in the HFSS program and optimized to improve the results obtained. Production will be done according to the best results In the first part of the thesis, theoretical information about microstrip structures and microstrip power dividers in literature are given. Theoretical information shows how the design parameters of an ideal power divider should be. In this way, the scattering matrix of the ideal power divider is obtained. The most important design parameters of the power dividers/combiners are loss and isolation. In order to overcome the problem of loss and isolation, the methods in the literature have been handled within the scope of the thesis. Impedance matching method which is one of the most important method to improve loss of power dividers in the literature has been simulated in HFSS simulation environment. Due to the impedance matching, the power level reflected from the input port is reduced, thus reducing the loss on the power divider. However, a simple impedance transformers does not provide the requirements as it operates in the narrow band. In order to power divider can operate in wideband, the impedance transformers is designed as three section and simulated. The frequency band is expanded with a three section impedance transformers and verified to reduce loss at wide bandwidth. Finally; a tapered impedance transformers, commonly used in broadband designs, is simulated in HFSS simulation environment. It has been observed that the tapered structure increases the frequency band but causes some loss compared to other methods. As a result of comparison; For a 6-15 GHz bandwidth, the power divider which has a 3-section impedance transformer, appears to provide the best results. In the second part of the thesis, array antenna feeding circuit design and design steps are given. Firstly, the requirements for the feeding circuit design have been determined. It is aimed to design a 4 way power divider capable of operating in the frequency range of 6-15 GHz , having equal output ports and having a maximum insertion loss of 2 dB. If the isolation level of -10 dB can also be achieved, it is considered to use same circuit in the receiving line. Firstly, a basic 2 way T-junction power divider was designed and simulated in the HFSS simulation environment. The impedance mismatch between the input and output ports of a simple T-junction power divider and consequently the insertion loss of the power divider is not sufficient. In order to reduce the insertion loss in the frequency range of 6-15 GHz and to have the same impedance of the input and output ports, a 2 way T-junction power divider with a quarter wavelength impedence transformer as tapered structure is designed. Through the contribution of the impedance transformer used, the insertion loss in broadband is reduced and the amount of power transferred to the output ports is increased. The design has been improved by adding a notch to the junction point to further reduce the loss. The added notch provided an improvement of approximately 3 dB. For the 4 way power divider specified in the requirements, the 2 way power divider is multiplexed symmetrically by cascading. Thus, a compact 4 way power divider is designed. It has been observed that the result changes according to the size of the notch at the junction point and size of the power divider, and it is decided to optimize to find the best result. But the results did not change linearly depending on the size of the notch and the power divider. So“Sequential Nonlinear Programming”method is used for optimization. Through the optimization, it is aimed to improve power transmission. Hereby, a 4-way T-junction power divider with sufficient margin for production is designed. The designed 4 way T-junction power divider was produced with the LPKF device. Rogers 4003 material with a thickness of 0.813 mm was used in simulations and production. High frequency SMA connectors are soldered to the ports of the produced 4 way T junction power divider. Keysight brand 2 ports Network Analyzer, which operates in 10 MHz -50 GHz frequency range, was used to see the production results. Each ports. The ports that were empty were terminated with appropriate loads during the measurement. Produced power divider by drawing the production results over the simulation results has been confirmed to have similar characteristics to the designed power divider. The measurement results of the produced power divider are plotted on the simulation results and the produced power divider is confirmed to have a similar characteristic with the designed power divider. When the production results and the simulation results were compared, no significant difference was observed except for a low loss due to connectors and solder. Although the 4-way T-junction power divider provides many requirements, it cannot be used as a power combiner because of the poor isolation level. Due to the nature of the T-junction power dividers, the isolation levels are insufficient. If a power divider is also to be used as a combiner, the isolation level must be improved. Wilkinson power divider was designed to provide sufficient isolation level. Unlike the T-Junction power divider design, the wilkinson power divider has resistance on itself. The Wilkinson power divider is designed both tapered impedence transformers and 3-section impedence transformers structure. 3-section impedence transformers structure was preferred because the insertion loss of the 3-section wilkinson power divider was less as observed in the second section. The isolation level is improved by adding resistance between each compartment on the impedance converter. The 4-way wilkinson power divider is optimized by the method used in the T-junction power divider to have sufficient tolerances for production. The measurements of the 4-way wilkinson power divider produced were made under the same conditions as the T-junction power divider and the production results were plotted on the simulation results. In the last part of the thesis, simulation and production results are compared and the difference between simulation and production results is evaluated. In addition, the performance of the power divider, which varies according to the connectors observed during the measurements, was evaluated. As a result, a T-junction power divider with sufficient performance except the isolation level is designed. In order to improve the isolation level, wilkinson power divider structure is used and a solution that provides all requirements has been made. Thus, a 4-way power divider/combiner was obtained.

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