A Study On Multi-Band Orthomode Transducer

Multi-band orthomode transducer (OMT) is studied in this thesis. The OMT operates at K/Ka/EHF-band, it can be used for transmitting and receiving at three bands, so it can decrease the cost of ground station when used in satellite communication system. The main work includes the following four parts:1. The operating principle of the OMT is explained, and a structure is chosen after analyzing the advantages and disadvantages of several kinds of structures. A OMT and a duplexer constitute the multi-band OMT. The OMT achieves a high isolation between ports by orthogonal decoupling. The duplexer is used for separating the signals of Ka-band and EHF-band.2. A symmetrical OMT is designed and measured. Firstly, the horizontal polarization channel and vertical polarization channel are designed separately, then an optimal simulation is adopt for the entire structure by HFSS. The measure result indicates that, in K/Ka-band, the return loss of the ports is better than about 15dB, the isolation between horizontal polarization port and vertical polarization port is better than 33dB, the insert loss is less than 0.5dB.3. A waveguide duplexer is designed and measured. It is made up of Ka-band low pass filter, EHF-band high pass filter and H-T junction. The measure result indicates that, in Ka/EHF-band, the return loss of the ports is better than 16.5dB, the isolation between the ports is better than 37dB, the insert loss is less than 0.85dB.4. A measurement is completed for the multi-band OMT. Compared with the OMT, its performance declined.