An Efficient Design Method for Multilayer Frequency-Selective Structures Based on Transmission Line Filter Model

This communication presents an efficient approach for designing high-performance multilayer frequency-selective structures (MFSS). First, based on the approximate equivalent transmission line (TL) model of symmetric MFSS, the general characteristics of its transmission matrix and power loss ratio (PLR) are derived. By matching this PLR expression with that of standard filter responses, the required circuit parameters in the TL model are solved to achieve standard filtering characteristics. Furthermore, a cascaded matching method (CMM) is proposed to identify array elements with the desired equivalent LC parameters, thereby enabling the design of MFSS with standard filter responses. The proposed approach eliminates the need for impedance inverters, phase shifters, and tedious calculations between equivalent circuit transformations of dielectric layers and metallic array layers. However, the CMM method avoids reliance on empirical formulas or prior knowledge when searching for array elements with specified equivalent LC parameters.