A Dual-Band Wideband U-Slot Resonant Metasurface Antenna Array for Millimeter-Wave Applications Using Characteristic Mode Analysis

This communication presents a dual-band millimeter-wave (mmW) antenna array with a U-slot resonant metasurface antenna (U-RMA) design. Using characteristic mode analysis (CMA), we analyzed a U-RMA, incorporating the feeding slot and feed line to identify dominant resonant modes, mode interactions, and the impact of capacitive coupling from auxiliary patches. The integration of metallic strips and vias along the x-direction effectively suppresses surface waves, resulting in a 2 dB gain improvement in the higher frequency band for the element. The CMA then extended to the current distribution of a $1\times 8$ array, excluding the feeding structure. Experimental results show reflection coefficient bandwidths of 26.6% (22.8–29.8 GHz) and 20.9% (33.4–41.2 GHz) for the n258, n257, and n260 bands, with stable radiation patterns and cross-polarization levels below −22 dB at 25, 29, 36, and 39 GHz. The measured peak realized gain is 15.2 dBi. Beam-scanning simulations demonstrate the array’s capability to steer the main beam with low scan loss and acceptable sidelobe levels, highlighting its potential for advanced wireless communication applications.