Design and Analysis of Ultra-Thin Narrow Band Pass Spatial Filter with Engineered Structure

This article presents the design and analysis of a narrowband Frequency Selective Surface (FSS) model operating at lower sub- GHz frequencies. A systematic synthesis approach using an equivalent circuit model is examined and utilized. The FSS consists of a two-layer structure built on a 20 mil thick substrate, designed for a centre frequency of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$f_{0}=1.4$</tex> GHz. Square patches are incorporated on either side of the FSS structure, with a cross-shaped patch on other side of the top FSS substrate. The configuration is optimized to achieve a narrowband pass response, enhancing the filtering performance. The coefficients for transmission and reflection of the two-layer FSS are evaluated under various incident angles, demonstrating its potential for radome applications. The equivalent lumpedelement circuit model similarly replicates the FSS behaviour, simplifying both analysis and implementation. Full-wave simulation results reveal a stable frequency response with minimal angular sensitivity across different incidence angles. This FSS design offers improved band selectivity and reduced insertion loss, making it a suitable option for advanced radome applications.