A Low-Profile C-Band Broadband Metasurface Antenna Array Based on Characteristic Mode Analysis

This study proposes the design of a low-profile C-band broadband metasurface (MTS) antenna array based on characteristic mode analysis. The antenna’s unit structure is composed of 12 large inclined square patches and a surrounding ring of smaller patches that together form the MTS radiating element. Its feeding structure is composed of the lowest microstrip line, and the energy is coupled through coupling slots and a dielectric layer before being radiated to the MTS. The dimensions of the proposed antenna element are 1.1λ<sub>0</sub> × 1.1λ<sub>0</sub> × 0.079λ<sub>0</sub>, with λ<sub>0</sub> being the free-space wavelength corresponding to a frequency of 6 GHz. The unit achieved an impedance bandwidth of 60% at -10 dB return loss and a peak gain of 9.95 dBi within the operating bandwidth. Building on this, a 1 × 2 array was designed and structurally tested, yielding an impedance bandwidth of 61% at -10 dB return loss and a peak gain of 12.6 dBi. Furthermore, antenna samples were fabricated, with the measurement results confirming the accuracy of the design.