A High Roll-Off, Wide Rejection FSS-Based Bandpass Filter for L-S Bands

This study proposes a comprehensive investigation on the design of a high roll-off., wide rejection bandpass filter based on a multi-layered configuration of frequency selective surfaces (FSSs) with miniaturized elements. The filter is meant to operate in L-S bands., and it is conceived by extensively recurring to the transmission line theory. Specifically., the filter aim is to totally reject the L band., while guaranteeing a large passing band between 2 and 4 GHz. The filter's functionality relies on the combined action of two distinct FSSs. The first is represented by a standard grid., acting as a high-pass element., fundamental to reject the lower frequencies. Conversely., the other FSS is configured as a Hilbert unit-cell shape., acting as an extremely selective bandpass element. By performing full-wave simulations., this design demonstrated a bandpass response spanning from 2.2 to 3.7 GHz for TE polarization with maximum insertion loss of - 1.7 dB., for incidence angles up to 30°. Moreover., the filter exhibits a high roll-off with a transmission coefficient transition from -10 dB up to -1 dB in a span of 130 MHz.