Design of high-performance quad-ridged OMT with a 3:1 bandwidth

<p indent="0mm">Orthomode transducer (OMT) is a key component in radio astronomy telescope antenna feed systems. Conventional OMTs are found coupling energy to higher orders at high frequency band when operating bandwidth over 2:1, which is exacerbated by manufacturing errors. The higher order modes degrade OMT performances and affect horn radiation pattern, which is unsuitable for wide band applications. In this paper, the effects of main parameters on higher modes performances and wideband matching method are studied. A 3:1 bandwidth quad-ridged OMT from <sc>3.3–10.0 GHz</sc> is designed. We built a prototype of this design and checked its performances. The reflection coefficients of two orthogonal polarizations are better than <sc>−16 dB,</sc> the insertion loss is less than <sc>0.4 dB</sc> and the isolation is better than <sc>35 dB.</sc> Measured and simulated results match very well, which validates our design.