Investigation on substrate integrated frequency selective surfaces
Luo Guo Qing
ABSTRACT
Frequency Selective Surfaces (FSS) has been extensively investigated by many researchers over hundreds of years. FSS with different periodic elements and structures have been presented dramatically. However, most of them are constructed by layered periodic aperture or patch arrays, and resonances generated by these simple structures are low Q which results in low selectivities. Recently, with development of computer technology, many novel FSS with complicate configurations have been investigated. In this dissertation, substrate integrated waveguide (SIW) technology is firstly introduced into FSS design combined with conventional periodic aperture FSS. A series of novel high performance FSS are presented. The main contributions of this dissertation are listed as follow.
1. Two analysis methods of mode match method and spectral domain algorithm, which are popularly used to analyze periodic structures, have been discussed in detail. However, for their inherently limitations, only simple layered FSS can be analyzed by using these methods. In order to deal with true 3D periodic structures, finite difference frequency domain method (FDFD) combined with domain decomposition method (DDM) is firstly adopted to analyze 3D periodic structure. Numerical results are verified by experiments.
2. High performance FSS called SIWC-FSS is firstly presented, which is constructed by conventional aperture FSS combined with SIW technology. SIW cavity is constructed by setting metallic vias arrays around each periodic aperture element. Cavity resonance is introduced in SIWC-FSS with aperture resonance reserved. Then high selective performance is generated by these two resonances. With metallic vias introduced in SIWC-FSS, surface waves and grating lobes propagation in FSS interior can be suppressed effectively. SIWC-FSS with different aperture shapes have been discussed. Simulated and measured results show that square loop slot and gird slot are the most suitable slots for SIWC-FSS design.
3. High performance SIWC-FSS have been realized by multi-SIWC-FSS cascading method. Firstly high selective cascading SIWC-FSS with conventional quarter-wavelength spacers has been analyzed by FDFD-DDM and equivalent circuit method. Secondly compact high performance cascading SIWC-FSS with one transmission zero, quasi-elliptic and chebyshev responses have been realized based on theories of cascading cavities filter and dual-mode cavity filter. In order to get high performance SIWC-FSS quickly, high selectivity FSS with two sharp transition bands is realized by different size SIW cavities cascading or shunting.
4. The design method of SIWC-FSS is firstly introduced in multi-band FSS design. Concentric square loop slots combined with SIW is used to design dual-band and tri-band FSS. Inner square loop slot with convoluted shape is adopted to realize multi-band FSS with narrow band spacing. In order to get narrow band spacing with high selectivity reserved, a novel design method of neighboring periodic cells with perturbation is presented. Simulated and measured results show that a high selectivity SIWC-FSS with narrow band spacing can be successfully obtained by using this novel method.
5. Based on the fact that FSS used in application is always incorporated with antenna, integrated design of SIWC-FSS and horn antenna is firstly investigated. By using properly designed SIWC-FSS cover at horn aperture, a single module with multi-function called Filtenna (filtering antenna) is successfully obtained. In this module good filtering performance is introduced with perfect radiation performance of horn antenna reserved. It has advantages of anti-interference ability and reduced Radar Cross Section (RCS). A novel realization of H plane sectoral horn antenna using SIW technology is firstly discussed. Seamless integration of filter and antenna realized by SIW technology also has been studied.
Key words: Frequency Selective Surfaces (FSS), substrate integrated waveguide (SIW), finite difference frequency domain method (FDFD), domain decomposition method (DDM), one transmission zero, quasi-elliptic, chebyshev, two sharp transition bands, cascading, shunting, integrated module, H plane sectoral horn
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