Multiple CSRRs Loaded Millimeter-Wave Circularly Polarized SIW Antenna with Improved Stopband

A millimeter-wave bandstop circularly polarized taper slot antenna fed by a substrate integrated waveguide (SIW) is designed in this paper. Multiple complementary spilt-ring resonators (CSRRs) are loaded on the transition structure between SIW and radiating aperture areas of a circularly polarized antenna. By this way, improved stopband is achieved without enlarging antenna size and deteriorating the in-band radiation performance. Simulation results show that the impedance bandwidth of the designed antenna is $40 \%$ covering from 27.2 to 40.8 GHz, and the axial ratio from 25.3 to 40.8 GHz is kept less than 3 dB. Furthermore, the designed antenna has improved stopband range from 43.5 to 49.5 GHz.