Design of a Low-Profile Broadband Metasurface Antenna Fed by an L-Shaped Probe Based on Characteristic Mode Analysis

In this study, characteristic mode analysis (CMA) is employed to design a low-profile broadband metasurface antenna fed by an L-shaped probe. Adjusting partial patch sizes and segmenting the patches on the metasurface increase the antenna bandwidth and suppress sidelobe levels. As a result, despite a profile of only 0.07 λ0 (where λ0 is the free-space wavelength at the center operating frequency), the proposed antenna exhibits an impedance bandwidth of 40.8% (4.94–7.47 GHz), with a gain ranging from 7.6 dBi to 9.6 dBi, and a front-to-back ratio exceeding 18 dB. Furthermore, its cross-polarization levels in the E-plane and H-plane in the main radiation direction are below -29 dB and -18 dB, respectively. Overall, the proposed antenna features a wide bandwidth, low profile, high front-to-back ratio, and stable gain, making it suitable for 5G and 6G Wi-Fi communication.