Design of Frequency Selective Surface via Equivalent Circuits for Broadband Radome Application

In this paper, a hybrid multilayer frequency selective surfaces (FSS) radome capable of maintaining a stable passband over a wide frequency range is proposed. The radome is composed of two FSS arrays embedded within the dielectric layers of a C-sandwich structure, enabling it to operate over a wide passband and maintain a stable frequency response with respect to different incident angles and polarizations. The design procedure employs curve fitting based on the equivalent circuit method (ECM), which is used to determine the initial structural dimensions of the FSS. For verification, a prototype was fabricated. The measured frequency response agreed well with the numerical results of the ECM and full-wave simulations, exhibiting flat-top characteristics at 4–12 GHz and remaining stable at an incident angle of 50° for TE and TM polarizations.