GENİŞ AÇILI HUZME TARAMASI YAPABİLEN TM21 KİPİNDE ÇALIŞAN MİKROŞERİT ANTEN TABANLI DOĞRUSAL DİZİ ANTEN TASARIMI VE DENEYSEL DOĞRULAMASI
A LINEAR ARRAY ANTENNA DESIGN WITH WIDE-ANGLE BEAM SCANNING CAPABILITY BASED ON A TM21 MODE MICROSTRIP ANTEN AND EXPERIMENTAL VALIDATION
- Tez No: 992318
- Danışmanlar: DOÇ. DR. KAMİL KARAÇUHA, DR. GALİP ORKUN ARICAN
- Tez Türü: Yüksek Lisans
- Konular: Elektrik ve Elektronik Mühendisliği, Electrical and Electronics Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2026
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Lisansüstü Eğitim Enstitüsü
- Ana Bilim Dalı: Elektronik ve Haberleşme Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Elektronik Mühendisliği Bilim Dalı
- Sayfa Sayısı: Belirtilmemiş.
Özet
Günümüz uydu haberleşme sistemleri, radar uygulamaları ve hareketli platformlar gibi birçok alanda kullanılan anten sistemlerinden beklenen geniş kapsama alanı, yüksek yönlendirilebilirlik ve geniş tarama açıları boyunca kararlı ışıma performansı beklenmektedir. Özellikle alçak dünya yörüngesinde (Low Earth Orbit, LEO) görev yapan uydu platformlarında, uyduların hızlı yörünge hareketleri nedeniyle geniş tarama aralıklarında düşük kazanç kaybı ile çalışabilen antenlere ihtiyaç duyulmaktadır. Ancak geleneksel faz dizili antenlerde tarama açısı arttıkça kazanç kaybı, yan lob seviyelerinin yükselmesi ve huzme bozulmaları kaçınılmaz olarak ortaya çıkmaktadır. Bu durum, uydu üzerindeki anten sistemlerinin toplam performansını ve görev etkinliğini sınırlayan temel etkenlerden biridir. Bu tez çalışmasında, geniş tarama açıları boyunca düşük kazanç kaybı sağlayabilen, düşük profilli ve üretimi görece kolay bir faz dizili anten yapısının geliştirilmesi hedeflenmiştir. Bu amaçla, mikroşerit yama anten elemanı TM21 kipinde çalıştırılmış; yama ve anteni çevreleyen dielektrik duvarlar üzerinde konumlandırılan parazitik iletken elemanlar birlikte kullanılmıştır. Bu yapı sayesinde, TM$_{21}$ kipinin doğası gereği merkezde zayıf kalan ışıma bölgesi, parazitik elemanların katkısıyla doldurulmuştur. Böylece dikine ışıma doğrultusunda daha düzgün ve geniş bir ışıma örüntüsü elde edilmiştir. Ortaya çıkan bu geniş ve sürekliliği yüksek ışıma karakteristiği, anten elemanının yarı güçteki huzme genişliğinin belirgin biçimde artırılmasını sağlamış ve böylece dizi antenin geniş açılarda etkin biçimde tarama yapabilmesine olanak tanımıştır. Bu yaklaşım, literatürde yaygın olarak kullanılan TM11 kipine dayalı veya yalnızca yapısal boyutlandırma yoluyla huzme genişletmeyi hedefleyen yöntemlerden ayrışan, özgün bir tasarım stratejisi sunmaktadır. Çalışma kapsamında ilk olarak, geniş huzmeli bir mikroşerit anten birim elemanı tasarlanmış ve elektromanyetik benzetimleri gerçekleştirilmiştir. Tasarım sürecinde kısa devre pimleri, iletken duvarlar ve parazitik eleman yerleşimleri farklı senaryolar altında incelenmiş; ışıma örüntüsü, giriş empedansı ve bant içi performans kriterleri dikkate alınarak nihai birim eleman yapısı elde edilmiştir. Önerilen birim elemanın çalışma frekansında yaklaşık 240° yarı güçteki huzme genişliği sunduğu ölçüm sonuçlarıyla gösterilmiştir. Ardından, geliştirilen birim eleman kullanılarak 11.8–12.5 GHz arasında çalışan 1×16 elemanlı doğrusal bir faz dizili anten tasarlanmıştır. Dizi yapısı için elektromanyetik analizler yapılmış, çok portlu S-parametre davranışı ve farklı tarama açıları altındaki aktif empedans değişimleri incelenmiştir. Benzetim sonuçlarına dayanarak üretilen prototip dizi anten üzerinde geri yansıma katsayısı, portlar arası yalıtım ve ışıma örüntüsü ölçümleri gerçekleştirilmiştir. Ölçüm sonuçları, benzetim verileriyle karşılaştırılarak tasarımın doğruluğu deneysel olarak doğrulanmıştır. Elde edilen sonuçlar, önerilen faz dizili anten yapısının yaklaşık ±75◦ tarama aralığında düşük kazanç kaybı ve düşük yan lob seviyesi ile çalışabildiğini ve huzme karakteristiğinin tarama boyunca kararlı kaldığını göstermektedir. Bu yönüyle çalışma, geniş tarama yeteneğine sahip faz dizili anten tasarımlarına alternatif bir yaklaşım sunmakta; özellikle LEO uydu haberleşme sistemleri, modern radar sistemleri ve hareketli haberleşme platformları için uygulanabilir bir çözüm ortaya koymaktadır.
Özet (Çeviri)
Antenna systems employed in satellite communication platforms, radar systems, and various mobile, airborne, and spaceborne applications are increasingly required to provide wide angular coverage, high directivity, and stable radiation characteristics over large beam scanning ranges. In particular, satellite communication systems operating in Low Earth Orbit (LEO) impose stringent performance requirements on antenna systems due to the rapid relative motion between the satellite and the Earth. As a result of this high orbital velocity, antennas mounted on LEO platforms must maintain reliable radiation performance while scanning over wide elevation angles, ensuring minimal scan loss, controlled sidelobe levels, and a stable main beam shape throughout the scanning range. Conventional phased array antennas are typically designed using microstrip patch elements operating in their fundamental resonant modes, such as the TM11 mode. While these configurations offer advantages in terms of simplicity, low profile, and ease of fabrication, they inherently suffer from limited half-power beamwidth at the element level. As the beam is steered away from the broadside direction, the array performance degrades due to increased gain loss, elevated sidelobe levels, and distortion of the main beam. These limitations are primarily attributed to the narrow radiation characteristics of the individual antenna elements and the strong dependence of the array radiation pattern on the element pattern. Consequently, achieving wide-angle beam scanning with acceptable performance remains a significant challenge for conventional phased array antenna designs. This thesis addresses these limitations by proposing a low-profile microstrip-based phased array antenna architecture capable of wide-angle beam scanning with reduced scan loss. The central idea of the proposed approach is to improve the radiation characteristics of the antenna element itself rather than relying on complex feeding networks, bulky three-dimensional structures, or additional impedance-matching layers such as superstrates or metasurfaces. To this end, a design methodology based on higher-order mode operation of a microstrip patch antenna element is introduced. In the proposed design, the antenna element operates in the TM21 resonant mode instead of the commonly used TM11 mode. The TM21 mode inherently provides wider angular radiation coverage; however, it exhibits a weak radiation region in the broadside direction due to its field distribution characteristics. To overcome this drawback, the proposed antenna structure incorporates slot features etched on the patch and parasitic conductive elements positioned on dielectric walls surrounding the antenna. The dielectric walls serve both as mechanical supports and as platforms that enable precise placement of the parasitic elements. Through controlled electromagnetic coupling between the patch, the slot structures, and the parasitic elements, the radiation deficiency in the broadside direction is effectively compensated. As a result, the radiation pattern of the antenna element becomes smoother and more uniformly distributed across a wide angular range. The broadside radiation is reinforced, and a continuous radiation characteristic is achieved over both low and high elevation angles. This behavior leads to a substantial increase in the half-power beamwidth of the antenna element, enabling more effective utilization of the array factor during beam steering. Unlike many approaches reported in the literature that rely on single-mode operation, purely geometrical beam widening techniques, or additional layers placed above the antenna aperture, the proposed strategy offers an alternative and original solution by combining higher-order mode excitation with parasitic element-assisted radiation shaping. Within the scope of this study, the design process begins with the development of a wide-beam microstrip antenna unit element. Full-wave electromagnetic simulations are conducted to analyze the radiation characteristics, input impedance behavior, and modal field distributions of the antenna. Key design parameters, including the placement of shorting pins, the geometry of the conductive walls, and the configuration of the parasitic elements, are systematically investigated through parametric studies. Based on these analyses, an optimized antenna element structure satisfying both wide-beam radiation and impedance-matching requirements is obtained. Simulation and measurement results demonstrate that the proposed antenna element achieves an approximate half-power beamwidth of 240° in the Ku band while maintaining acceptable impedance matching across the operating frequency range. The wide and stable radiation characteristics of the element form a solid foundation for the subsequent array design. Based on the optimized antenna element, a linear phased array antenna consisting of 1×16 elements is designed to operate in the 11.8–12.5 GHz frequency band. Detailed electromagnetic analyses are carried out to evaluate the multiport S-parameter characteristics, mutual coupling effects, and active input impedance variations under different beam scanning conditions. The interaction between antenna elements is carefully examined to ensure that the wide-beam characteristics of the individual elements are preserved at the array level. Following the simulation-based design phase, a prototype of the proposed linear phased array antenna is fabricated using standard printed circuit board manufacturing techniques. The antenna structure, including the microstrip patches, dielectric walls, parasitic elements, and feeding network, is realized in a compact and low profile form. Experimental characterization is performed through reflection coefficient measurements, inter-element isolation analysis, and radiation pattern measurements conducted in an anechoic chamber environment. The measured results show good agreement with the simulation data, validating the accuracy of the proposed design methodology. The phased array antenna demonstrates stable beam steering performance with low scan loss over an approximate scanning range of ±75◦. Moreover, the sidelobe levels remain within acceptable limits throughout the scanning range, indicating robust radiation behavior under wide-angle beam steering conditions. Beyond the primary radiation and impedance performance metrics, the proposed antenna architecture also offers several practical and system-level advantages that further enhance its applicability to real-world phased array systems. One important aspect is the compatibility of the proposed antenna structure with standard multilayer printed circuit board (PCB) technologies. The use of dielectric walls and parasitic conductive elements does not require complex three-dimensional machining or exotic fabrication processes. Instead, the antenna geometry can be readily implemented using conventional PCB manufacturing techniques, making the proposed design particularly attractive for high-frequency phased array applications where cost, repeatability, and manufacturability are critical considerations. From a system integration perspective, the proposed antenna element is well suited for phased array implementations employing dense element spacing and compact layouts. The wide-beam radiation characteristic of the element relaxes the constraints on scan angle limitations that typically arise from element pattern roll-off. As a result, the array can achieve wide-angle scanning without excessive reliance on amplitude tapering or sophisticated sidelobe control techniques, which often complicate the feeding network and increase system losses. This feature is especially advantageous in spaceborne and airborne platforms, where power efficiency and hardware simplicity are of paramount importance. Another key contribution of this work lies in the detailed investigation of active impedance behavior under beam scanning conditions. In phased array systems, the input impedance of each antenna element varies with scan angle due to mutual coupling and phase progression across the array. If not properly accounted for, these variations can significantly degrade matching performance and lead to increased reflection losses at large scan angles. In this study, active S-parameter analysis is employed to accurately characterize the scan-dependent impedance behavior of the proposed array. Both simulation-based and measurement-based S-parameter data are utilized to compute the active reflection coefficients under various steering scenarios. The results demonstrate that the proposed array maintains stable impedance matching over a wide frequency range, even at high scan angles approaching ±75◦. The active reflection coefficients remain below the commonly accepted −10 dB threshold across the operational band, confirming that the array is capable of wide-angle beam steering without severe impedance degradation. This behavior is a direct consequence of the wide-beam element design and the careful consideration of element-to-element interactions during the array optimization process. In addition to impedance performance, radiation pattern stability under beam scanning is thoroughly evaluated using both simulated and measured data. Near-field radiation measurements are conducted for individual antenna elements, and the corresponding far-field patterns are reconstructed through post-processing techniques. By combining the measured element patterns with appropriate phase excitations, the overall array radiation patterns are synthesized for different scan angles. This measurement-based array pattern synthesis approach provides valuable insight into the real-world scanning behavior of the array, accounting for fabrication tolerances, measurement uncertainties, and practical coupling effects that are not always fully captured in simulations. The synthesized radiation patterns confirm that the main beam can be steered smoothly over a wide angular range while preserving its shape and directionality. Although some asymmetry is observed in certain azimuthal planes due to the orientation of parasitic elements, this effect is not expected to pose a limitation in two-dimensional or planar array configurations where symmetry can be restored through appropriate element placement. Moreover, the sidelobe behavior remains well controlled throughout the scanning range, indicating that the proposed antenna structure does not introduce undesirable radiation artifacts under wide-angle steering. Overall, the results presented in this thesis demonstrate that wide-angle beam scanning can be effectively achieved through element-level radiation enhancement rather than relying solely on array-level complexity. By leveraging higher-order mode excitation and parasitic element-assisted radiation shaping, the proposed design achieves a favorable balance between performance, complexity, and practicality. The experimental validation further confirms that the proposed approach is not only theoretically sound but also robust against real-world fabrication and measurement uncertainties. In summary, the proposed microstrip-based phased array antenna offers a compact, low-profile, and manufacturable solution for wide-angle beam scanning applications. The combination of wide-beam antenna elements, stable active impedance behavior, and experimentally verified scanning performance makes the proposed design a strong candidate for next-generation LEO satellite communication systems, advanced radar platforms, and other mobile communication applications requiring reliable wide-angle radiation performance.
Benzer Tezler
- Atherosklerotik kalp hastalıklarında risk faktörleri
Risk factors in the coronary artery disease
MURAT SUHER
- Nükleer rezonasta moleküler yapıların incelenmesi (yapısal faz geçiş kuramları üzerine bir inceleme)
Başlık çevirisi yok
ABDURRAHMAN ANDİÇ
Yüksek Lisans
Türkçe
1986
Fizik ve Fizik MühendisliğiUludağ ÜniversitesiFizik Ana Bilim Dalı
PROF. DR. AYTAÇ YALÇINER
- Sivas yöresinde akraba evliliği yapan ve yapmayan çiftlerde dermatoglifik benzerlikler
Similarities of dermataoglyphies among individval of married relatives and married couples not related to each other in Sivas region
Y. SELMA SÜNGÜ
Yüksek Lisans
Türkçe
1984
Tıbbi BiyolojiCumhuriyet ÜniversitesiTıbbi Biyoloji ve Genetik Ana Bilim Dalı
YRD. DOÇ. DR. İLHAN SEZGİN
- Eksternal etmoidektomiler
Başlık çevirisi yok
ERCÜMENT AKMAN
Tıpta Uzmanlık
Türkçe
1987
Kulak Burun ve BoğazGazi ÜniversitesiKulak Burun Boğaz Ana Bilim Dalı
PROF.DR. NECMETTİN AKYILDIZ
- Samsun ve çevresinde tarla sarmaşığı (conuolvulus arvensis L.)'na karşı biyolojik savaşa esas olacak fauna tespiti
Investigations on the insect fauna of the field binweed (Conuolvulus arvensis L.) related to its biological control in Samsun Province
YASEMİN UFUK GERMAN