A compact circularly polarized (CP) substrate integrated waveguide (SIW) cavity‐backed antenna with controlled axial ratio

Summary A new circular cavity‐backed slot antenna, which produces unidirectional radiation patterns, has been developed for wireless communication systems. The antenna utilizes substrate‐integrated waveguide (SIW) technology to create a low‐profile cavity. The metal cladding on top of the cavity has an engraved circular ring slot for radiation, and a microstrip transition feeding mechanism is used to excite the perturbed circular slot antenna element located away from the centre of the cavity. Two rectangular cuts, including slots and a shorted via probe, improve radiation performance and bandwidth matching by nearly −40 dB over the working frequency range. An optimized spacing of 0.6 mm is established between the patch centre and the input microstrip transition feed, which produces a circularly polarized (CP) wave. The antenna uses CP SIW technology to operate within a wide impedance bandwidth of 12.18% (10.02–11.31 GHz) below −10 dB and an ARBW of 320 MHz (10.40–10.72 GHz). Both experimental and simulated results agree on s‐parameters, and the antenna's gain, axial ratio, and radiation patterns are consistent. With 7.45 dB CP gain and planar integration, the antenna radiates unidirectional, making it suitable for lightweight wireless broadband applications.