A Conformal Miniaturized Bandpass Frequency-Selective Surface With Stable Frequency Response for Radome Applications

Abstract

This article demonstrates a conformal miniaturized bandpass frequency-selective surface (FSS) with excellent frequency response stability. First, the simulation design for the finite FSS array is proposed. Next, the central connection patch, the ring patch, and the aperture elements, mapped from the first-order equivalent circuit model (ECM), are chosen to obtain transmission properties under conformal conditions. The influence law of elements on the performance stability and elements suitable for narrowband or wideband under conformal conditions are summarized. Based on these, a miniaturized wideband FSS for X-band with stable transmission performance is designed. The angular stability of the planar FSS can reach 75°. In the case of the conformal FSS with the bending angle of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$5\pi $ </tex-math></inline-formula> /6, the resonance frequency deviation is 2.32% under <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${y}$ </tex-math></inline-formula> -polarized and almost zero under <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${x}$ </tex-math></inline-formula> -polarized. The transmission coefficients of the FSS prototype are also measured for both planar and curved surfaces. When the FSS is conformal on the cylindrical surface with a radius of 159 mm, the resonance frequency deviation can be almost negligible, and the transmission performance remains stable up to 70°. The measurement results are in good agreement with the simulation results, verifying the effectiveness of the proposed FSS structure and the simulation design.