Wideband orthomode transducer for the Square Kilometre Array band4 single pixel feed

摘要

Abstract The design of a compact wideband orthomode transducer (OMT) for band4 single pixel feed of the Square Kilometre Array (SKA) dish is presented. The geometry of the proposed OMT is based on circular quad‐ridged waveguide to obtain wideband characteristics, which consists of a coaxial to quad‐ridged waveguide transition and a circular to quad‐ridged waveguide tapered transition. By adopting circular quad‐ridged waveguide and high‐order cosine taper for the ridges, the length of OMT is compact and the levels of higher‐order modes generated at the circular waveguide aperture are lower. To verify the OMT performance, a prototype is manufactured and tested using a vector network analyzer. The measured results agree very well with the calculated ones across the frequency range 2.8‐5.18 GHz. The tested reflection coefficients are less than –19 dB, the insertion losses are less than 0.25 dB for both polarization channels, and the isolation between two output ports is better than 37.7 dB. It is confirmed that the designed OMT can be satisfied with the requirement of the SKA band4 feed system.