A millimeter-wave broadband metasurface-based antenna with a low profile is proposed. In order to guide the mode excitation, the characteristic mode analysis (CMA) is used for the design and optimization of the proposed antenna. Four sets of coplanar patches with different dimensions on a thin printed circuit board are used to generate four adjacent broadside modes, which are directly fed by a coaxial probe. Then, to expand low-frequency bandwidth, a new resonant mode is introduced by etching slots on the parasite patch. Meanwhile, the extra mode introduced does not significantly change the radiation performance of the original modes. Moreover, dual slots are etched on the mid patch fed by the coaxial probe, which moves the orthogonal modes of the chosen modes out of the operating band to reduce cross-polarization levels. The proposed antenna realized 25.02 % (30-38.58 GHz) impedance bandwidth with dimensions of 1.423×1.423×0.029λ0 3 (λ0 is the wavelength at 34 GHz in free space), and the realized gain in the band is 8.35-11.3 dB.
Keywords: broadband antenna; characteristic mode analysis (CMA); metasurface-based antenna; millimeter-wave antenna.