Compact Coaxial Probe-Fed CP Substrate Integrated Waveguide Cavity-Backed Antenna Utilizing Slot Split Ring

A circularly polarized (CP) substrate integrated waveguide (SIW) cavity-backed slot antenna is proposed. A slot split ring (SSR) etched on the top metal surface of an SIW resonator is employed to generate the right-handed circularly polarized (RHCP) wave. The proposed antenna is excited directly by a coaxial probe with a proper distance from the symmetric axis of the SSR resonator. A prototype of the proposed CP antenna at the center frequency of 10 GHz is manufactured. As a result, the proposed antenna exhibits the advantages of both conventional planar antennas and metallic cavity backed antennas, including simple structure, compact size of 15.8x15.8mm(2), light weight, easy fabrication, high gain and wide axial ratio bandwidth. It is proved by experiment that an impedance bandwidth of 10.2% for the reflection coefficient less than-10 dB, an axial ratio (AR) bandwidth of 1.72% for AR less than 3 dB, and a RHCP gain 5.5 dBi have been obtained.