X-band circular ring-slot antenna embedded in single-layered SIW for circular polarisation

A circularly-polarised antenna which has a novel feeding structure like a substrate integrated waveguide, a cavity-backed resonator and a conventional ring-slot antenna is proposed for right-handed circular polarisation (RHCP) in a single-layered fabrication. The CP generation and broadband impedance matching characteristics are accomplished by using a simple shorting via between the top patch and bottom ground plane and inserting inductive via arrays at the input port, respectively. A broadband impedance bandwidth of 18.74% and a RHCP axial ratio of 2.3% have been obtained under the condition of less than VSWR 2:1 and axial ratio -3 dB, respectively.