Abstract: A novel Ku-band all-metal high-isolation waveguide linearly-polarized diplexer is designed in this paper. The diplexer consists of an ortho-mode transducer (OMT) and two different frequency filters. The OMT adopts the form of asymmetric non-diaphragm and has excellent linear polarization characteristics. The structure enables full bandwidth communication while keeping the structure compact. In order to suppress the out-of-band signal and improve the port isolation, the uplink channel adopts an evanescent-mode band-pass filter, and the downlink channel adopts a stepped-impedance low-pass filter. The test results show that the linear polarized diplexer can cover the entire bandwidth of Ku-band satellite communication (uplink: 13. 75-14. 5 GHz, downlink: 10. 7-12. 75 GHz), the reflection coefficient is less than -15 dB in the working frequency range, and the port isolation is better than 85 dB.