Compact and High Performance Stepped Truncated-circular Waveguide Branching Ortho-mode Transducer (stcwb-omt)

This paper reports design and development of an innovative compact Stepped Truncated-Circular Waveguide Branching Ortho-Mode Transducer (STCWB-OMT) operating at 4.5–4.8 GHz for horizontal and vertical polarizations. STCWB-OMT is derived by introducing branch waveguide via coupling slot on a stepped truncatedcircular waveguide. This configuration possesses inbuilt rectangularto-circular transition; therefore it does not require any additional square-to-circular transition to combine it with horn antenna. The challenge in the design incorporated is to obtain a mechanically compact design with low mass while compliant with the specified electrical performances; since this device is developed for space-borne application. Achieved return losses at both direct and coupled ports are > 17 dB, insertion losses < 0.08 dB for both polarizations, isolation is < −60 dB and cross-polarization discrimination > 40 dB with the OMT length = 1.98λ at center frequency and weight = 250 gm The agreement between measured and computed results provides a validation of the proposed OMT configuration.