Development of Ka-Band Wideband Circular Polarizer

Ka-band broadband receiver of Tianma telescope is an important observation platform for the study of star formation and deep space exploration. This paper discusses the development process of Ka-band wideband circular polarizer of the receiver core device. The device consists of 90° phase shifter and ortho-mode transducer (OMT), whose operating frequency band is 26.5-40GHz, and relative bandwidth reaches 41%. This paper firstly introduces the application background and working principle of circular polarizer, and then carries on the concrete model design and electromagnetic simulation with electromagnetic simulation software, then carries on the structural design and processing test. The results of final test indicate that phase error by the phase shifter is 90±4°, axial ratio is 0.6dB, cross polarization of OMT is -26dB, isolation of OMT is -35dB, return loss of each port is less than -18dB. These results are consistent with the design simulation.