Geniş bantlı yama anten tasarımı
Wideband microstrip patch antenna
Yazar: ULAŞ KESKİN
Danışman: DOÇ. DR. MESUT KARTAL
İstanbul Teknik Üniversitesi / Bilişim Enstitüsü / İletişim Sistemleri Ana Bilim Dalı / Uydu Haberleşmesi ve Uzaktan Algılama Bilim Dalı
Derece: Yüksek Lisans, 2017
Konu: Bilim ve Teknoloji = Science and Technology

Özet:
Mikroşerit yama anten birçok avantaja sahip ve yaygın olarak kullanılan bir mikrodalga antendir. Kullanım alanları da gün geçtikçe artmaktadır. Bununla birlikte klasik mikroşerit anten, düşük empedans bant genişligi, düsük anten kazancı ve tolerans problemlerine sahiptir. Bu çalısmanın amacı, mikroşerit antenlerde dar bant, komleks geometrilerle elde edilen geniş bant, düşük anten kazancı gibi elektriksel özelliklerin iyileştirilmesi için basit geometri ile kayda değer kazanç ile geniş bant yama anten geometrisinin geliştirilmesidir.
Mikroşerit yama anten analiz ve tasarımı için değişik modeller incelenmiştir. Farklı şekilde mikroşerit anten yapıları araştırılıp, üç farklı şekilde tasarım sunulmuştur. Geliştirilen bu yeni tasarımda özellikle basit geometri ile anten empedans bant genişliği konusunda iyileştirilme yapılmıştır. Parametrik analizlerle ve analitik incelemelerle, yarık parametreleri ve besleme noktalarının konfigürasyonları ayarlanarak geniş bantlı anten elde edilmiştir. Tasarlanan antenlerde ayarlı yapıların uzunluğu, genişliği, yarık ölçütleri ve besleme noktalarının uygun seçilmesi genişbant mekanizmaların eldesinde önem kazandığı çalışmada gösterilmiştir. 
Bu tasarımda FR4 eproxy malzeme,dielektrik sabiti (εr)= 4,4, anten genişliği 50mm ,uzunluğu 55mm taban malzemesi kalınlığı (h)= 1,6 mm alınmıştır ve tanjant kaybı (q)=0,02 kullanılmıştır.
Bu çalışmada ana hedef beslemenin yerinin uygun  şekilde değiştirilerek tasarlanan tek yarık açılmış antene göre %100 fazla band genişliği sağlanmasıdır. Geleneksel dikdörtgensel yama antene göre de yaklaşık 4 kat daha fazla band genişliği sağlamaktadır.Geleneksel antenimiz %66, dikdörtgen slot açılmış antenimiz %100 ve öneri olarak sunduğumuz anten %133 oransal bant genişliği sağlayarak Ultra bant genişliği özelliğini bu açıdan sağlamaktadır. Antenimiz düşük frekanslarda x-z düzleminde, frekans arttıkça farklı doğrultularda ışıma yapmaktadır. Farklı frekanslarda, farklı düzlemlerde, farklı açılarda ışımalar verilmiştir. Böylelikle anteni çevirmeden düşük frekansta z yönünde, yüksek frekansta farklı açıda max. Işıma yaparak aynı anda farklı uygulamalar için kullanılacak bir anten olmuştur.
Bundan sonraki aşamalarda eğer gerekirse boyutlarının biraz daha küçültülmesi ve ışıma deseninde iyileştirme sağlanması şeklinde amaçlanmaktadır. Ayrıca besleme noktasına anahtarlama düzeneği kurularak, yönlü ışıma farklı açılarda değiştirilerek kontrol edilecek şekilde tasarım yapılması düşünülebilir.
2,4/5,2/5,8-GHz WLAN , 2,5/3,5/5,5-GHz WiMAX ,Uydu Bandlarının (S,C,X ) yönlü uygulamarında, biomedical uygulamalarda kullanılabilir faydalı bir tasarım olacaktır. Tasarımda gerçekleştirmeler sonlu elemanlar yöntemini kullanan Ansoft High Frequency Structure Simulator HFSS'de yapılmıştır.

Abstract:
The most common type of microstrip antenna is the patch antenna. They are usually employed at UHF and higher frequencies because the size of the antenna is directly tied to the wavelength at the resonant frequency. Also patch antenna provides a maximum directive gain of around 20 dB.
The microstrip antenna (MSA) is one of the most widely used microwave antennas possessing several advantages. However, it presents a low impedance bandwidth, low gain and tolerance problems. Due to the increasing usage of wireless communication applications, the performance improvement studies of such systems has found a growing investigation area in recent years.
The study handle on satellite communication frequencies that are S,C and X bands. Satellite technology is developing fast, and the applications for satellite technology are increasing all the time. Not only can satellites be used for radio communications, but they are also used for astronomy, weather forecasting, broadcasting, mapping and many more applications. Also it can be used WiMAX (Worldwide Interoperability for Microwave Access) that  is a family of wireless communication standards based on the IEEE 802.16 set of standards and can be used bidirectional MOBESE application. 
Also it can be be used for WLANs that are based on IEEE 802.11 standards and are marketed under the Wi-Fi brand name. It covers Bluetooth devices and microwave ovens,HomeRF,HiperLAN etc.Also it can be use in biotelemetry system as component of radio antenna. 
The aim of this study is to develop a new wideband microstrip patch antenna design for improving the electrical characteristics such as narrow band with simple geometric shapes. In calculation phase the length (L) and width (W) of patch, the length extension ΔL and the effective permittivity (εeff) is related to the permittivity is calculated. In simulation all antennas we have used FR4 substrate having a value of εr=4.4, loss tangent of 0.02 along with size parameters of 50mm (Width) × 55mm (Length) × 1.6mm (Height) that have simple structure of microstrip antenna. These antenna are connected to a 50 Ω SMA connector for signal transmission.  
In the research stage of this thesis, different microstrip antenna designs for analysis and design of microstrip antennas were investigated. 
There are various methods to increase the bandwidth of microstrip patch antennas. For example by decreasing the Q-factor of the patch and by increasing the substrate height and lowering the dielectric constant the bandwidth of microstrip patch antennas can be increased. Another way could be use of multiple resonators located in one plane. It can also use multilayer configurations with multiple resonators stacked vertically. And lastly very effective way of increasing bandwidth of microstrip antenna is use of impedance matching networks, these are in literature made so far.
It is worth mentioning that the ground plane of the proposed antenna is also a part of the radiating configuration on the ground plane affects the characteristics of the antenna. The gap formed between the rectangular radiation plane and the ground plane  significantly affects the impedance performance and was optimised by simulation.and has been optimized to 21.5mm in proposed antenna.
Three different types of  design were introduced. Especially in this new design antenna impedance bandwidth is improved with simple geometric shapes that relocating the feedline of the microstrip antenna.  Design process has realized in three steps and first of all conventional rectangular patch antenna design which supports some part of the desired communication technologies is done. Second, bandwidth enhancement has been achieved by introducing a rectangular slot in the patch. Third wideband has been achieved by relocating the feedline of the microstrip antenna. In this goemetry relocating achieved extreme bandwith enhancements with %100 to rectangular slot in the patch and nearly four times bandwidth increase to conventional microstrip antenna. The antenna satisfies the requirement of UWB systems with  fractional bandwidths of 0.66 percent,1 percent and 1,33 percent respectively.
Main purposes for the design process are to enhance to bandwith of the antenna. In the first chapter of the thesis, it mentioned chronologically history of electromagnetic wave's discovery. In the second chapter it mentioned antenna characterization, power flow on the antenna. In the third chapter it mentioned wireless and satellite communication standards. In the fourth chapter it mentioned microstrip antenna features, characteristics and feeding methods. In the fifth and result chapter, the results are discussed by comparing with the design purposes. The performance capabilities of the antenna are summarized. Also a table is prepared for without any chnages of the antenna status, it can be used for S band applications in the z direction and bidirectional applications with like phi = 110 for wimax (5.5GHz) applications. 
The aim of this study is to design a simple Ultra-Wide Band (UWB) microstrip antenna. Bandwidth enhancement is achieved by properly etching a rectangular slot on the radiating patch of the antenna. Subsequently, feedline location is optimized in order to apply parasitic technique which results bandwidth enhancement.
Proposed antenna could change from an omnidirectional to a directive antenna. It can be observed that the antenna patterns in the xz-plane are almost omnidirectional at low frequencies and as frecuency increases pattern bidirectional radiation occurs at high frequencies. This directive has advantage use several application use at the same time.
Radiation patterns are displayed for ISM, WLAN, WIMAX and (S, C, X) satellite communication bands. Radiation angles for these communication bands are also investigated. Achieved results are shared in fifth and result chapter. Trying this approach on antennas with different feedline point with switch mechanism could control the directivity of the antenna.
The dielectric loading of a microstrip antenna affects both its radiation pattern, impedance bandwidth and gain. If it chosen low dielectric constant substrate, it could get high gain efficiency than expected at high frequencies.
Also with switch mechanism of feedline can be controlled of direction   and maximized utility for this kind of antenna. One of the advantage of the microstrip antenna is using multiple feed points, or a single feedpoint with asymmetric patch structures. In this study specially focused on single feedpoint affect.  
The proposed antenna is useful for bidirectional 2.4/5.2/5.8-GHz WLAN bands, 2.5/3.5/5.5-GHz WiMAX bands wireless communication and 2,07/2,18/2,5GHz S band, 5,15GHz C Band,7,5GHz X Band satellite communication. Also it can be used in biotelemetry system for analyzing several physiological parameters from free ranging patients within a transmission range of 100 metres. The proposed antenna can be practical for UWB applications.  All the designed antennas are simulated using Ansoft High Frequency Structure Simulator (HFSS).