Compact Hybrid Choke Rings for Dual-Band Circularly Polarized GPS Antenna

This letter presents the compact hybrid choke rings for the dual-band circularly polarized global positioning system (GPS) antenna, in order to suppress the surface wave propagation and reduce the back lobe levels. The designed dual-band circularly polarized antenna is center-fed and composed of two radiation patches. The novel compact hybrid choke rings are introduced to reduce the radiation back lobes and improve the front to back ratio effectively. The measured results show that the return loss of the antenna is greater than 10 dB and the bandwidth covers GPS L2 from 1.168 to 1.238 GHz and GPS L1 from 1.543 to 1.599 GHz. In the working bands, the front to back ratio of the proposed antenna is greater than 30 dB.