A fully planar substrate integrated probe-based wideband orthomode transducer

This paper introduces a planar orthomode transducer (OMT) using substrate integrated waveguides (SIWs) and substrate integrated coaxial lines (SICLs) that is entirely contained within two substrate layers. SICLs form a quadruplet of probes inside the metal waveguide with fully symmetrical geometry. Such a structure is smaller and lighter than a waveguide OMT, its construction is simpler than of a coaxial OMT, however, isolation and loss properties are less degraded compared to the use of planar unshielded technologies such as microstrip. A new wideband inline SICL to SIW transition has been developed to allow grade separation of SIWs belonging to opposite polarizations through different substrate layers. The designed substrate integrated probe-based OMT on RO4003C^™ substrate covers the frequency band from 8.1 GHz to 12.5 GHz with return loss higher than 19 dB, insertion loss less than 1.2 dB, inter-port isolation higher than 62 dB and cross-polarization discrimination higher than 65 dB.