Design of a Low-Scattering Dual-Band Metasurface Array Antenna Using Characteristic Mode Theory

This work proposes a Characteristic Mode Theory (CMT)-guided method for the co-design of radiation and scattering performance of a low-scattering dual-band metasurface array antenna. Conventional design approaches generally treat radiation design and RCS reduction as two separate targets. In contrast, the proposed method leverages the differences in the spatial distributions of radiation and scattering characteristic modes. Dual-band radiation modes are constructed and excited within the central region of the metasurface, while the edge and corner regions are locally reconfigured to suppress dominant scattering modes without significantly perturbing the radiation-mode current distributions. In this way, dual-band radiation and broadband RCS reduction are simultaneously realized within a single metasurface aperture. A systematic radiation-scattering co-design workflow driven by characteristic-mode parameters is established. Modal significance (MS), radiation-mode current distributions, and modal radiation patterns are used to regulate the target radiation modes and determine the feeding configuration. Modal weighting coefficients (MWCs) under plane-wave illumination are used to identify the dominant scattering modes, while the corresponding scattering-mode current distributions are used to determine the structural modification regions and corresponding modification strategies. The antenna developed using the proposed method integrates dual-band radiation and broadband RCS reduction within a single low-profile configuration. Measured results demonstrate that the antenna covers two operating bands of 3.08-3.10 GHz and 3.12-3.18 GHz, with peak gains of 16.0 dBi and 16.4 dBi, respectively. Within the 6.5-10.5 GHz band, more than 10 dB monostatic RCS reduction is achieved under both x- and y-polarized plane-wave illumination.