A Non-Uniform Metasurface-Based Wideband CP Antenna With Additional Filtering Response

A low-profile circular-polarized (CP) metasurface antenna (MSA) with wide axial ratio (AR) bandwidth and additional filtering response is presented. The proposed MSA consists of an array of $4\times 4$ non-uniform corner-truncated patch units, and is excited by a filtering balun through two parallel coupling slots. An additional AR minimum can be produced by the non-uniform units resulting an improved AR bandwidth. The filtering balun with extra resonant stubs can produce three radiation nulls to form a bandpass filtering response. Simulated results indicate that the proposed filtering CP MSA has a fractional bandwidth of 17.7% for $\vert \boldsymbol{S}_{11}\vert < -10\text{dB}$ and AR < 3 dB, which can cover the 5G N79 band (4.4 - 5 GHz). Good bandpass filtering response with a flat in-band gain variation from 7.9 to 8.9 dBic and high out-of-band rejection levels of 31 and 27 dB in the lower and upper stopbands, respectively, are also observed.