Two-Probe Waveguide Orthomode Transducer With Twofold Rotational Symmetry

A novel (patent pending) waveguide orthomode transducer (OMT) design is presented. The use of a common waveguide cross section with twofold rotational symmetry is proposed to mitigate the typical drawbacks of a two-probe OMT geometry. In particular, the cross-polarized electric field component may be reduced by introducing a twofold rotationally symmetric cross-sectional design with slant axes in the reference frame defined by the directions of the two coupling probes. Interestingly, it is also demonstrated that this solution may be used directly in the probing area to either reduce the cross-polarized field component or to reduce the probe-to-probe coupling. The aspect ratio of the required asymmetric section is close to 1, and the design has limited impact on other signals when used as an orthomode junction (OMJ) in multifrequency feed systems. Two designs, one with dual-linear operation and one with dual-circular operation, are optimized in K-band (17.7-20.2 GHz). Good agreement is found between simulated and measured data, validating the concept. This solution is of interest for the design of future multifrequency feed systems onboard broadband communication satellites.