Single-Layer Asymmetric PRS Based on Compact Microstrip Resonant Cells for Broadband Antenna Gain Enhancement

In this paper, a novel single-layer asymmetric partially reflective surface (PRS) based on compact microstrip resonant cells (CMRCs) is proposed for gain enhancement of a Fabry-Pérot cavity (FPC) antenna over a wide bandwidth. It overcomes the conventional PRS’s narrow gain bandwidth limitation caused by the frequency dependence of their reflection phase. The proposed PRS consists of two different CMRC patterns etched on the top and bottom of a single dielectric layer. This configuration produces a positive gradient in the reflection phase response and double resonances that merge in the reflection magnitude response, resulting in a broadband characteristic. Due to its inherent asymmetric property, the bi-characteristic-impedance transmission line (BCITL), which can effectively represent asymmetric reciprocal transmission lines (ARTLs), is used to accurately model and analyze the CMRC-based PRS. The results show good agreement with those of the full-wave simulation. A prototype of the optimized FPC antenna was fabricated and tested. The measurement results, within the operating frequency band of 5.15 GHz to 6.0 GHz, show an improvement in gain of 5 dB compared to the reference antenna, with a peak gain of 10.18 dBi and a 3-dB gain bandwidth of 15.72%.