Turkish Journal of Electrical Engineering and Computer Sciences




In this study, the design of a dual-band mode converter, which provides transition from rectangular waveguide T E10 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 T E11 mode. It is revealed from the measurement results that while the designed structure gives more than 17.5 dB return loss and suppression of T E11 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 T E11 mode, and less than 0.3 dB insertion loss of T M01 mode within 900 MHz bandwidth at RX band.


Dual-band, circular waveguide, mode converter, equivalent circuit model, mode level measurement technique, additive manufacturing

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