Wideband Circularly Polarized Filtering Antenna based on Metasurface

In this paper, a circularly polarized antenna with filtering characteristic is proposed based on metasurface structure. The planar metasurface consists of 4*4 nonuniform metallic patch cells, which are fed by two separated microstrip-coupled slots from the bottom. Next, a shorting via and two pairs of stubs are employed to introduce two radiation nulls at the two edges of the passband to provide good filtering performance. Finally, the metasurface is rotated to introduce perturbation for realization of the circular polarization. To demonstrate the idea, a CP filtering antenna operating at 5.5 GHz is designed and simulated. The simulated results show that the 10-dB impedance bandwidth is 22.8% and the 3-dB AR bandwidth is 22.2%. Over the bandwidth, the average gain is 8.5 dBic with less than 1dB variation, showing a flat filtering response and demonstrating the validation of the proposed circularly polarized filtering antenna.