Bandwidth Of Frequency Selective Surfaces Research Articles

Design of SIW cavity models to control the bandwidth of frequency selective surface

This study describes substrate integrated waveguide (SIW) cavity models to control the bandwidth of frequency selective surfaces (FSSs). Two different SIW cavities were presented: one model to reduce (cavity-I) and another model to improve (cavity-II) bandwidth of FSS, respectively. The periodic structures were made of SIW cavies and an FSS slot on either side of the dielectric substrate at the centre of the cavity. To prove the concept, a well-known cross-slot FSS element has been studied in two different cases and compared their performance. The conformal behaviour of the unit cells has been estimated by considering the practical requirements. The addressed SIW cavities will improve the electromagnetic (EM) performance of conventional FSS without altering its basic shape. The high Q-factor of SIW cavity greatly improves the performance of FSS. A full-wave simulation is used to analyse the response of FSS. The cavity-I shows 12.61% lesser bandwidth and cavity-II shows 25.0% higher bandwidth compared to its conventional shape in planar form and 9.1, 26.17% in the conformal form at a bent radius of 50 mm. Besides, performance parameters were studied to evaluate the structural dependency on EM performance. Finally, two designed cavity models are fabricated and proved their performance experimentally.

Ultrathin Broadband Absorber Using Frequency-Selective Surface and Frequency-Dispersive Magnetic Materials

The bandwidth of frequency-selective surface (FSS)-based absorber decreases when high permittivity material is used to reduce the thickness of the absorber. A solution of this thickness-bandwidth dilemma was presented by using resistive FSS layer and frequency-dispersive magnetic material (FDMM) in substrate. The FDMM was designed for a certain profile of complex permeability, and the FDMM substrate has both high permeability and permittivity for thickness reduction and near frequency-nondispersive input susceptance for bandwidth expanding at low frequencies. A 2.3 mm thick FSS-based FDMM absorber was designed and fabricated, which achieved a broad absorption band of 4–15 GHz (3.75:1) with −10 dB reflectivity. In terms of the same bandwidth ratio, the thickness of FSS-based FDMM absorber is only $0.031\lambda _{L}$ against the thickness of $0.114\lambda _{L}$ of conventional FSS-based absorber.

유한크기 FSS의 곡률효과에 따른 주파수 특성 해석

In this paper, we have analyzed the curvature effects of the finite FSS(frequency selective surface) using the 3-D method of moment using the BiCGSTab algorithm as an iterative method. To validate the analysis method in this paper, we compared the RCS(radar cross section) of PEC(perfect electric conductor) sphere with theoretical results and it shows well agreements. The tripole slot FSSs which have many application in military were selected for the investigation of curvature effect and RCS as a frequency characteristics were observed with the variation of the curvature rate. Simulation results shows that curvature effect can significant effect the passband frequency and bandwidth of FSS. We suggest that the curvature effect must be considered at the stage of design FSS application like FSS radome.

체스판 형태를 갖는 주파수 선택구조 설계

본 논문에서는 체스판 형태를 갖는 주파수 선택구조를 설계하였다. 주파수 선택구조의 주파수 응답 특성을 변화시키는 변수로서 단위셀을 구성하는 개구면 및 패치의 크기, 간격, 두께의 변화에 따른 주파수 응답 특성 변화를 관찰하였다. 변수의 변화에 따라서 대역 저지 및 대역 통과 특성을 얻을 수 있었으며, 공진 주파수 및 대역폭을 제어할 수 있는 설계 변수를 얻을 수 있었다. 설계 결과를 바탕으로 X-band 공진특성을 갖는 패치 타입의 주파수 선택구조를 두께 1mm의 FR4 기판으로 제작 및 측정하여 설계 결과를 검증하였다. 본 논문에서 제안하는 체스판 형태를 갖는 주파수 선택구조를 사용하게 되면, 원하는 주파수 대역에 따라 주파수를 선택적으로 제어할 수 있는 레이돔과 같은 전자기구조 설계에 유용하게 사용될 것으로 예상된다. The frequency selective surfaces(FSSs) with chessboard patterns are proposed and designed for the first time in this paper. We proposed the design parameters like slot and patch size, gap between slots or patches, and dielectric thickness of FSS chessboard unit cell proposed in this paper. Also, we found that the variation of design parameters can be used to control the frequency transmission characteristics like the resonant frequency or bandwidth of FSS. To validate the proposed FSS, we fabricated the proposed FSS with the use of 1.0mm FR4 for the bandpass operation at X-band and measured the transmission characteristics. From the results, the proposed FSS with chessboard type can be widely applied to application of the frequency controllable radome design because we can use the design parameters selectively.

FAST ANALYSIS AND DESIGN OF FREQUENCY SELECTIVE SURFACE USING THE GMRESR-FFT METHOD

In this paper, frequency selective surfaces (FSSs) are analyzed and designed. The analytical procedure is based on method of moments (MoM). The generalized minimal residual recursive method combined with fast Fourier transform (GMRESR-FFT) is utilized to accelerate the solution of the matrix equation. Our numerical results show that the GMRESR-FFT method can converge at least 3 times faster than the generalized minimal residual fast Fourier transform method (GMRES-FFT). In this paper, the cross dipoles are first used to design the FSS filter with a passband at 300 GHz and a stopband at 450 GHz, and then the Jerusalem cross slots are utilized to avoid grating lobes and improve the bandwidth of FSS. Numerical results demonstrate the validity and efficiency of the presented method.

A Sensitivity Analysis of Frequency Selective Surfaces at Millimeter Wave Band

This work presents a sensitivity analysis for the resonant frequency and bandwidth of frequency selective surfaces (FSS) as a function of the structural parameters. The frequency selective surface structure considered here is composed by crossed dipole conductive patches deposited on an anisotropic dielectric layer. Firstly, the moment method is used in combination with the immittance technique in the spectral domain to determine the frequency response of the analyzed structure. Secondly, numerical techniques are used to obtain the resonant frequency and bandwidth sensitivities as a function of the considered FSS structural parameters.