Analysis of leaky modes in Fabry-Perot cavity antennas based on thin and thick partially reflecting sheets

A comprehensive analysis of Fabry-Perot cavity antennas (FPCAs) employing thick- and thin-partially reflecting sheets (PRSs) is presented. The transition between thin- and thick-PRS configurations and its impact on the leaky-mode distributions are investigated through a transverse equivalent network (TEN) method and a field-matching-technique (FMT) approach. Both techniques allow for gaining physical insights on the enhancement of the gain-bandwidth figure of merit in thick-PRS-based FPCAs. Important conditions to improve the bandwidth performance are found and explained in terms of the superstrate electrical thickness. The results of this analysis provide fundamental design rules for optimizing radiation in FPCAs.