A differential fed open-ended waveguide antenna based on stepped ridge transition

This paper presents a differential fed square openended waveguide (OEW) antenna based on stepped ridge transition for planar near-field (PNF) measurement application, covering 8 GHz to 12 GHz. By using a multi-stepped quad-ridged transition, the in-band reflection coefficient characteristic of the coaxial-waveguide can be optimized, and finally can be controlled below -22dB for both polarizations. At the same time, the differential feeding technology is adopted, which can suppress some high-order modes. The simulated results show that the proposed square OEW antenna possesses low reflection, high isolation, high polarization discrimination and stable radiation pattern characteristics in the working band. Therefore, it has great potential to be used as a probe antenna for PNF measurement systems.