Compact W-Band Septum Orthomode Transducer Based on Gap Waveguide

A new method to design an orthomode transducer (OMT) is reported, which is achieved by combining a septum polarizer with an E-plane magic-T. The two orthogonal polarization modes are generated by a septum polarizer with even and odd modes exciting conditions. To reduce the influence of processing errors at the millimeter-wave (mm-wave) band, electromagnetic bandgap (EBG) technology is introduced. To verify the design, two prototypes with and without EBG are fabricated and measured. The isolation performance of OMT is obviously enhanced by a loading EBG structure. The experimental result of 20% bandwidth from 90 to 110 GHz for port isolation less than −31.0 dB, polarization isolation less than −26.9 dB, and reflection coefficients less than −10 dB is achieved in the prototype with EBG.