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This paper presents a discussion on a low-profile, frequency-reconfigurable penta-band antenna. This antenna consists of two asymmetric L-shaped rectangular patches electrically connected by a single PIN diode. The proposed antenna operates at five frequency bands depending upon the switching states of the PIN diode. It operates at 2.4 GHz (WLAN) and 5.3 GHz (5G) during forward bias of the diode, 3.3 GHz (5G) and 5.9 GHz (WLAN) during reverse bias of the diode and 4 GHz during zero bias condition providing a wide bandwidth (3.6–4.8 GHz) at this state. The antenna has voltage standing wave ratio (VSWR) ranges from 1 to 2, gain value ranges from 2.6 to 5.0 dBi, and a maximum radiation efficiency of 85%. This antenna can be integrated with modern devices such as smart phones, laptops, and other handheld devices due to its simplistic geometry. A prototype of the model is fabricated, and the results are validated.

Significant improvements in terms of bandwidth of reflectarray antennas have been achieved by introduction of innovative paper substrate dielectric materials. Three differently custom composed organic dielectric substrates have been characterized for dielectric properties using a broadband technique based on open ended coax cable method. The substrates show low dielectric permittivities of 1.81, 1.63 and 1.84 along with a loss tangent of 0.053, 0.047 and 0.057. Validation of using the proposed substrates for reflectarray antenna was done by modelling and fabricating reflectarray unit elements on the three substrates. Scattering parameter analysis of unit reflectarray elements show encouraging results with a broadband frequency response of 340 MHz at a phase gradient of 0.14º/MHz. Thus the proposed substrate could serve exceptionally to address the narrow bandwidth problem in reflectarray antennas.

A simple CAD model based on cavity model analysis is proposed to compute accurately the resonant frequency, input impedance, and gain of radome loaded rectangular patch antenna. The computed values using present model for wide range of radome parameters are compared with different theoretical and experimental values available in open literature. To validate the present model, we have performed several sets of experiments. The present model shows very close agreements with the experiments compared to the other models. We have also used electromagnetic software (HFSS) to generate simulated data. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:2460–2468, 2013

Wide-band matching of a tunable 1D periodic microwave structure, designed for fabrication in GaAs technology, is investigated. The two-layer unit cell of the periodic structure consists of a microstrip line loaded by multiple rectangular patches, which can be selectively short-circuited. The wide variation of the position of the bandgap, obtained by electrically controlled switches, induces a large variation of the effective dielectric constant in the considered wide frequency range. This effect is further reflected as a significant variation of the characteristic impedance, and hence a potentially high mismatch loss. A method for wide-band minimization of the mismatch (with respect to a 50Ω reference impedance), without compromising the performance of the device, is presented.

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2009, Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2009, Bu çalışmada, mikroşerit beslemeli dikdörtgensel yama anten tasarımına odaklanılmıştır. Konvansiyonel mikroşerit yama antenin boyutları, iletim hattı metodu formülasyonları ile, dielektrik profilin türü, yüksekliği ve operasyon frekansı belirtimleri üzerine hesaplanmıştır. Yamanın ve dielektrik profilin boyutları değiştirilmeden, yama üzerinde oluşturulan yarıklar optimize edilerek rezonans frekansı, farklı operasyon bandlarına kaydırılmış, ek rezonans frekansları oluşturularak, yapıya dual-band operasyon kabiliyeti kazandırılmıştır. Antenlerin dizayn, optimizasyon ve similasyonu için HFSS paket programından faydalanılmıştır. Yarıkların mikroşerit yama antenler üzerindeki etkisini gözlemleme amacıyla, mevcut yapılar modifiye edilmiş; dört farklı yarıklı yama anten tasarlanarak, rezonans frekansı, band genişliği, yönlendiriciliği, ışıma verimliliği, kazancı ve hüzme genişliği değerleri incelenmiştir. Tasarım esnasında, mikroşerit hat ile yama arasında yüksek verimde güç transferini sağlayabilmek için besleme yarıkları vasıtasıyla giriş rezonans empedans değeri mikroşerit hattın karakteristik empedansına dönüştürülerek, empedans uygunlaştırması yapılmıştır. Empedans uygunlaştırmasının analizi için, yamanın giriş empedansı, iletim hattı duran dalga oranı ve geri dönüş kaybı değerlerinin frekans bandındaki değişimi incelenmiştir. Sonuç olarak, konvansiyonel yamanın boyutları değiştirilmeden, yama üzerinde oluşturulan yarıkların şekil, boyut ve konumu optimize edilerek farklı parametrik özelliklere sahip anten dizaynları yapılmış, parametrik performansları tartışılmıştır., In this project, rectangular patch antennas fed by microstrip line, have been focused. Dimensions of the convantional rectangular microstrip patch have been calculated by using transmission line method formulations on the specifications of substrate type (dielectric constant) , substrate height and operation frequency. Resonance frequencies have been shifted to another operation bands by optimizing the slots were constructed on the patch but not changing the dimensions of the patch and the substare and dual band operation ability have been provided by creating addition resonance frequnecies whereby the explained technique. Ansoft HFSS packet software have been used for design, optimization and simulation of the antennas. Four different antennas have been designed by being modified the available patch, to investigate the effects of slotted constructions on microstrip patch antennas and resonance frequency, bandwidth, directivity, radiation efficiency, gain and beam width values have been investigated and discussed. In the course of the design, empedance matching have been performed by inset feed notches, converting resonant input empedance value to characteristic empedance value of the microstrip linet o be able to transfer the power between microstrip line and patch antenna efficiently. Empedance matching success have been analysed by input empadance, voltage standing wave ratio and return loss variations on the patch and microstrip line. Consequently, Antenna designs which has different parametric specifications, have been performed, by being optimized shape, dimension and position of the slots which had been constructed on the patch and its results have been discussed., Yüksek Lisans, M.Sc.