Design of Wideband OMT Choke Flanges for Low PIM Satellite Communication Applications

In this article, two wideband choke flanges (Flange 1 and Flange 2) are designed to reduce the passive intermodulation (PIM) level of the orthmode transducer (OMT). Since flange connections are important sources of PIM, circular Flange 1 introduces a choke groove and achieves a power suppression level of 41.95 dB. To meet the requirement of miniaturization and lightweight, Flange 2 with rectangular structure and rectangular choke groove is proposed for reducing height waveguide. Compared with conventional circular choke flange for reduced height waveguide, it has a smaller cross area and better power suppression level (39.92 dB). To evaluate the PIM performance of the proposed OMT with two flanges, temperature circulation test is executed. It is proved that the third-order PIM level is about −135 dBm from measurement results. Therefore, the proposed flanges can be utilized in large-scale multibeam array for low PIM satellite communication applications.