Compact dual-band rectangular TE10 mode to circular TM01 mode converter for telemetry/telecommand applications in satellite communication: design, equivalent circuit modeling, mode level measurement technique and 3d printed manufacturing

In this study, the design of a dual-band mode converter, which provides transition from rectangular waveguide TE10 mode to circular waveguide TM01 mode and operates simultaneously in telemetry/telecommand (TT&C) frequencies, is presented along with its equivalent circuit and a mode level measurement technique. This dual-band converter is designed to uniformly excite TT&C slot antennas used in satellite communication with symmetric circular TM01 mode. The structure can work as a transceiver due to having one common rectangular waveguide feed. As a Ku-band application, a converter giving high purity TM01 mode at circular waveguide at 11.75 GHz/TX and 13.75 GHz/RX center frequencies is designed and manufactured with 3D printing technology. Approximate equivalent circuit models of the designed structure are extracted by using lumped elements from simulated S-parameter results. In addition, a measurement technique to detect the normalized power levels of different propagation modes in dual-band mode converter is applied on the manufactured structures to obtain transmission levels of circular TM01 mode and suppression levels of circular TE11 mode. It is revealed from the measurement results that while the designed structure gives more than 17.5 dB return loss and suppression of TE11 mode, and less than 0.6 dB insertion loss of TM01 mode within 500 MHz bandwidth at TX band, it gives more than 23 dB return loss and suppression of TE11 mode, and less than 0.3 dB insertion loss of TM01 mode within 900 MHz bandwidth at RX band.