摘要： A circularly polarized (CP) substrate integrated waveguide (SIW) cavity-backed antenna based on dual concentric, orthogonal slot split ring resonators is proposed and experimentally studied. The circularly polarized wave is generated by two split ring-slots etched in the upper metal layer of the SIW cavity resonator. These two slots are excited by a coaxial probe located in the gap of the external slot split ring to radiate the right-handed circularly polarized (RHCP) wave. By rotating the dual split slot ring resonators and the probe by 45 degrees relative to the backed cavity, a better match characteristic and a slightly higher radiation gain are obtained. Because of the concentricity of radiant split ring slots, the beamwidth of the circular polarization is obviously increased. From the experimental results, the impedance bandwidth was 10.8% for the re?ection coe?cient less than ?10 dB, the axial ratio (AR) bandwidth was 1.54% for the AR less than 3 dB, and the RHCP gain was 4.44 dBic. Moreover, the 3-dB axial ratio beamwidth at the centre frequency of 10.40 GHz has been extended to 142? in the angular range from ?78? to +64?.