Konformal yama antenin radar kesit alanının azaltılması
Radar cross section reduction for conformal patch antenna
- Tez No: 954029
- Danışmanlar: PROF. DR. FUNDA AKLEMAN YAPAR
- Tez Türü: Yüksek Lisans
- Konular: Savunma ve Savunma Teknolojileri, Defense and Defense Technologies
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2025
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Lisansüstü Eğitim Enstitüsü
- Ana Bilim Dalı: Elektronik ve Haberleşme Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Telekomünikasyon Mühendisliği Bilim Dalı
- Sayfa Sayısı: 84
Özet
Bu çalışma, silindirik bir nesne üzerinde kullanılan konformal yama anteninin radar kesitini azaltmak için manto pelerin tasarımını sunmaktadır. Elektronik savaş teknolojisinin oldukça ilerlediği bu dönemde görünmezlik uygulamaları vazgeçilmez unsurlardan biri olmaktadır. Radar kesit alanı (RKA) azaltımı, İkinci Dünya Savaşından itibaren askeri alanda görünmezliği ve düşman radarından korunmayı sağlamak için çok önemli bir konu haline gelmiştir. Bu konuyla ilgili güncel çalışmalar her geçen gün artmaktadır. Nesnelerin sahip olduğu saçılmayla birlikte nesnelerin üzerindeki antenler, radar kesit alanlarına büyük ölçüde katkıda bulunur. Bu nedenle nesnelerin üzerindeki antenlerin RKA azaltımı da oldukça etkili bir yöntemdir. Bu çalışmada kullanılan konformal yama anten, esnekliği sayesinde nesnelere kolayca entegre edilebilir bir yapıdadır. Askeri alanda kullanılan uçak, füze, gemi gibi nesnelerin eğimli yüzeylerine kolaylıkla yerleştirilebilir. Bu nesneler üzerindeki antenler radar kesit alanına oldukça katkıda bulunduğu için antenin radar kesit alanını azaltmak, toplamdaki radar görünmezliği için oldukça etkili olacaktır. Burada ele alınan yöntemle beraber RKA azaltımını sağlamak için gerekli yüzey empedansı Lorenz Mie saçılma teorisine göre hesaplandı. Savaş teçhizatının ve savaş uçaklarının görünürlüğünün azaltılması askeri alanda önemli bir konu haline geldiği için görünürlüğün engellenmesi amacıyla literatürde elektromanyetik gizleme olarak bilinen, nesnelerin etrafındaki elektromanyetik saçılımın azaltılması prensibine dayanan konuya olan ilgi artmıştır. Bu nedenle bu ekipmanların görünürlüğünü engellemek amacıyla anten yamasının şekillendirilmesi, pasif engelleme veya aktif engelleme, anten düzleminde yarıklar gibi kesme yöntemleri, radar soğurucu malzeme (Radar Absorbing Materials, RAM) kullanımı, frekans seçici yüzey (Frequency Selective Surface, FSS) kullanımı ve manto pelerini kullanımı görülmektedir. Bu çalışmada konformal yama antenin radar kesit alanını azaltmak için manto pelerin tekniği kullanılmıştır. Bu teknik pasif engelleme tekniğinin altında kabul edilir. Gelen dalgaların farklı yönlere saçılmasıyla radar kesit alanınında azaltma meydana getirilir. Manto pelerini tekniğinin, daha geniş bir bant genişliği sağlayan ve uygulanması ve üretilmesi kolay olan düşük profil ve ultra ince meta yüzey gibi birçok avantajı vardır. Bu çalışmada silindirik bir yapı üzerinde yama antenin silindirik nesnesinin şeklini alarak konformal bir yama anten yapısı oluşturulmuştur. Bu konformal yama anteninin oluşturduğu elektromanyetik saçılımı bir manto pelerini kullanarak, radar kesit alanında bir azalma elde edilmiştir. Aynı zamanda antenin ışıma özellikleri kullanılan teknikle birlikte değişmemiştir. Manto pelerinli ve manto pelerinsiz anten için RKA hesaplamaları yapılmıştır. Elde edilen sonuçlar doğrultusunda 9,3 GHz ile 11,6 GHz frekansları arasında antenin radar kesit alanında azalma elde edilmiştir. Literatürdeki çalışmalara ek olarak farklı bir manto pelerin geometrisi kullanılmış ve 10,3 GHz frekansında 14 dB mutlak radar kesit azaltımı elde edilmiştir. Manto pelerinli ve manto pelerinsiz antenlerin yayılma özellikleri karşılaştırıldığında manto pelerin yapısının antenin empedans bant genişliği, kazancı ve modeli üzerinde ihmal edilebilir bir etkiye sahip olduğu gösterilmiştir.
Özet (Çeviri)
The radar cross section (RCS) represents a fundamental parameter that quantifies how detectable an object is by radar systems. In modern military applications, where stealth technology and electromagnetic invisibility are crucial, the reduction of RCS has become a critical area of research. Historically, efforts have focused primarily on minimizing the RCS of large platforms such as aircraft, naval vessels, and missiles. However, more recent studies have highlighted that individual components attached to these platforms, especially antennas, play a significant role in increasing the overall radar signature. Antennas, despite being essential for communication, navigation, and sensing, often contribute undesirable scattering due to their conductive elements and exposure on the object's surface. This challenge is exacerbated when antennas are mounted on curved surfaces, where traditional stealth techniques are less effective, thereby necessitating advanced methods to reduce their radar visibility without impairing their electromagnetic performance. Conformal antennas, which conform to the shape of the host platform, offer several benefits including aerodynamic compatibility, structural integration, and minimal physical profile, making them well suited for military and aerospace systems. Nonetheless, the geometric conformity of such antennas does not inherently mitigate their radar signature. The placement of antennas on curved, conductive surfaces often leads to complex scattering interactions that can elevate the RCS under certain radar illumination angles. This complexity underscores the need for stealth techniques that specifically address the unique scattering mechanisms introduced by conformal antennas. This study explores the application of a passive electromagnetic cloaking method, known as mantle cloaking, to reduce the radar cross section of a conformal patch antenna mounted on a cylindrical surface. Unlike active cloaking systems or bulky radar absorbing materials, the mantle cloak presents a lightweight, ultra-thin metasurface-based solution that can be seamlessly integrated into existing antenna structures. The principle underlying mantle cloaking involves enveloping the antenna with a metasurface engineered to provide a tailored surface impedance. This impedance effectively suppresses the dominant scattering modes by inducing destructive interference between the incident electromagnetic waves and the surface currents generated on the cloak. The theoretical framework is grounded in Lorenz-Mie scattering theory, which analytically characterizes the scattering behavior of electromagnetic waves from cylindrical and spherical objects, enabling precise determination of the surface impedance required for effective scattering cancellation. The antenna model consists of a microstrip patch designed to operate within the X-band frequency range, centered at 10.3 GHz, conformally mounted on a perfect electrically conducting cylindrical substrate. This configuration simulates realistic applications such as aircraft fuselages or missile bodies, where conformal antennas are frequently employed. Using full-wave electromagnetic simulation tools, such as CST Microwave Studio, the study first characterizes the baseline scattering and radiation properties of the antenna without any cloaking. The results reveal significant RCS peaks in both monostatic and bistatic radar observation angles, confirming the antenna's contribution to the radar signature of the system. To address this, a cylindrical mantle cloak comprising subwavelength periodic unit cells is designed and positioned circumferentially around the antenna. The unit cells' geometry and material parameters are optimized to synthesize the required surface impedance derived from Lorenz-Mie theory. This optimization targets the suppression of the scattering modes most responsible for backscatter at the operating frequency. Through parametric studies involving variations in unit cell dimensions, substrate permittivity, and metasurface thickness, the cloak design achieves a compact profile with thickness less than one hundredth of the wavelength, suitable for practical fabrication using standard printed circuit board (PCB) manufacturing techniques. Simulation results demonstrate a robust and broadband RCS reduction performance. The mantle cloak achieves a peak absolute RCS reduction of 14 dB at 10.3 GHz and maintains substantial suppression between 9.3 GHz and 11.6 GHz. These findings represent a notable improvement compared to uncloaked antenna configurations and demonstrate the bandwidth advantages of the mantle cloak design. Importantly, the cloak's ultra-thin structure ensures that the antenna's electromagnetic properties remain intact. Detailed comparison between the cloaked and uncloaked antenna shows negligible impact on impedance bandwidth, gain, and radiation pattern, highlighting the effectiveness of the mantle cloak in providing stealth while preserving antenna functionality. This compatibility is a crucial advantage over other stealth approaches such as radar absorbing materials (RAM) or frequency selective surfaces (FSS). RAMs often require thick, heavy layers which may degrade antenna performance and increase system weight, whereas FSS typically exhibit narrow bandwidths and are less adaptable to curved conformal geometries. Active cancellation techniques, while theoretically promising, introduce power consumption, added complexity, and potential reliability issues. In contrast, the passive and conformal nature of the mantle cloak ensures low profile, lightweight construction with minimal impact on existing system designs, making it highly appealing for practical military applications. Another significant contribution of this work lies in the customization of the cloak's metasurface geometry. Departing from traditional uniform designs, the unit cells were tailored to the specific current distributions on the patch antenna, allowing enhanced suppression of higher-order scattering modes. This adaptation is particularly valuable for conformal structures where modal interactions are more complex, and it suggests the potential to extend mantle cloaking techniques to a broader class of curved or composite surfaces beyond simple cylinders and spheres. The fabrication feasibility of the cloak was carefully considered. The design relies exclusively on commercially available PCB substrates and copper metallization processes, avoiding the need for exotic materials or complex manufacturing steps. This ensures scalability and cost-effectiveness, enabling retrofitting existing antenna platforms without extensive redesign. The cloak's mechanical flexibility and ultrathin profile further facilitate integration with the curved surfaces typical in aerospace applications. Looking forward, this study provides a solid foundation for experimental validation, recommending the measurement of RCS and antenna performance in anechoic chambers to verify simulation results. Moreover, future research directions include extending mantle cloak designs to dual-polarized and multi-band antennas, as well as integrating tunable elements such as varactor diodes or phase-change materials. Such advancements could enable adaptive or frequency-agile cloaking capabilities, enhancing stealth effectiveness under dynamic operational conditions. In conclusion, this research demonstrates a practical and effective approach to reducing the radar cross section of conformal patch antennas through the application of a passive mantle cloak. The proposed design achieves up to 14 dB RCS reduction at 10.3 GHz, with broadband performance spanning 9.3 to 11.6 GHz, while maintaining antenna radiation properties including gain, impedance bandwidth, and radiation pattern. The lightweight, ultrathin metasurface cloak is compatible with standard PCB fabrication techniques and suitable for integration into modern military platforms. As stealth requirements intensify in contemporary defense systems, mantle cloaking offers a scalable, efficient, and elegant solution to one of the key challenges in antenna design and radar signature management. In addition to the demonstrated reduction in radar cross section, the practical implications of implementing mantle cloaking on conformal antennas are far-reaching. The integration of such cloaks can significantly enhance the survivability and mission success rate of military assets by lowering their electromagnetic signature against increasingly sophisticated radar detection systems. The passive nature of mantle cloaks eliminates the need for external power sources or control circuits, thus simplifying system complexity and improving reliability in harsh operational environments. Furthermore, due to its conformal and ultra-thin characteristics, the cloak does not impose aerodynamic penalties, which is a critical consideration for high-speed platforms such as fighter aircraft and missiles. The metasurface design flexibility inherent to mantle cloaks also opens the door to multifunctional antenna systems. Beyond RCS reduction, metasurfaces can be engineered to manipulate antenna beam patterns, suppress unwanted sidelobes, or enhance polarization purity. This multifunctionality could enable future antennas to simultaneously meet stealth and communication performance requirements without trade-offs. Additionally, the modular nature of metasurface-based cloaks facilitates customization for different mission profiles or threat environments by altering unit cell geometries or incorporating tunable elements. Experimental validation remains an essential next step to confirm simulation results and understand real-world limitations such as fabrication tolerances, material losses, and environmental factors including temperature and humidity. Collaboration with defense manufacturers and testing in anechoic chambers would provide valuable insights into the practical performance of mantle cloaks integrated with conformal antennas. Moreover, field trials incorporating these cloaks on operational platforms would provide comprehensive data on radar detectability reduction and system robustness. Emerging research trends also suggest potential enhancements through the incorporation of active or hybrid metasurfaces. By embedding varactor diodes, microelectromechanical systems (MEMS), or phase-change materials within the cloak structure, it may be possible to dynamically tune the surface impedance in response to changing radar threats or operational frequencies. Such adaptability would represent a significant advancement over static cloaks, enabling real-time stealth optimization and improved spectral agility. Finally, the principles demonstrated here extend beyond military applications. Civilian sectors such as telecommunications and automotive radar systems could benefit from reduced electromagnetic interference and improved antenna integration afforded by mantle cloaks. For instance, low-observable antennas could enhance privacy and security in communication networks, while reducing electromagnetic pollution in dense urban environments. Therefore, the mantle cloaking technique holds promise as a versatile solution across a broad spectrum of electromagnetic applications. In summary, the research presented in this study establishes mantle cloaking as a viable and effective means to achieve radar cross section reduction for conformal patch antennas, with significant implications for stealth technology, antenna engineering and electromagnetic compatibility. The combination of theoretical rigor, simulation validation, and practical design considerations positions mantle cloaking as a leading candidate for next-generation stealth antenna solutions.
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