Abstract: The equivalent-circuit model (ECM)has been used to analyze the transmission performance of the frequency-selective surfaces(FSS).If the FSS is electrically free-standing or printed on an electrically thin dielectric substrate,the ECM approach is very efficient and accurate,However,in many actual applications, especially in aero space applications,the FSS is usually inserted in or etched on a thick dielectric sheet.To account for the influence of the di-electric material on the FSS’s frequency response,the simple ECM and a transmission line the-ory are used fo predict the fransmission and reflection characteristics of the FSS, which is com-prised of gridded-square arrays sandwiched in a dielectric sheet illuminated by a plane wave at arbitrary incident angle. It is found from the numerical results that the sandwiched FSS has good frequency-selective performance and insensitive incident angle response.This sandwiched FSScan be used as the refleclor of a small radar cross section(RCS)antenna system.

Key words: frequency-control, equivalent circuits, antenna design, electromagnetic scatter-cross sections