Wideband and Low-Cross-Polarization Planar Annual Ring Slot Antenna

This letter presents the design of a wideband and low cross-polarization single-layer annual ring slot antenna. By adopting differential feeding, the cross-polarization level could effectively be lowered while ensuring a low antenna profile. The structure of the substrate integrated waveguide back cavity improved the antenna gain, and the extra two short-circuit stubs added a new resonance point, extending the bandwidth. Furthermore, a modified circular ring slot was adopted to further improve cross-polarization performance. The measured −10 dB impedance bandwidth of the antenna was 51% (9–15.17 GHz), the gain in passband was about 9 dBi, and the cross-polarization level was below −35 dB. Compared to other similar antennas, the proposed antenna features an apparent improvement in terms of gain, cross-polarization level, and bandwidth.