Wideband differential‐fed metasurface antenna array using characteristic mode analysis

Abstract

AbstractA wideband differential‐fed (DF) metasurface (MTS) antenna array is proposed in this letter. As the element of the proposed array, a nonuniform MTS is designed step by step using characteristic mode analysis. In the first step, a 2 × 2 rectangular patch‐based MTS is investigated. We observe that its two fundamental modes exhibit even/odd symmetric current distributions, which can be regarded as a pair of c/π modes. Unlike c mode, π mode features nonbroadside radiation, which can be reshaped by modifying MTS to an asymmetric configuration in the second step. In the last step, a direct DF method is adopted to excite c/π modes and suppress other unwanted modes for wideband performance. The optimal DF positions are quantitatively predicted by calculating the impendence bandwidth of MTS fed by virtual probes. Moreover, to further increase the gain and improve the symmetry of radiation patterns, two proposed elements are integrated into a linear array. Finally, the proposed antenna array is fabricated and measured. The measured impedance bandwidth is 22.2% (6–7.5 GHz) with broadside radiation, stable gains varying from 8.5 to 11.3 dBi, and a front‐to‐back ratio better than 19 dB.