Abstract
AbstractA compact wideband orthomode transducer (OMT) with an octave bandwidth is proposed for a 0.56‐1.12 GHz receiver system in the five hundred meter aperture spherical radio telescope. The OMT operates in a cryostat at a temperature of 70 K and therefore it is critical to minimize its dimension while insuring good electrical properties. The complete OMT comprises 2 bowtie dipoles orthogonally arranged in a circular waveguide. Because of the innovative structure, competing modes, TM01 TE21, and TE01, have been effectively suppressed, and the bandwidth of the dominate mode TE11 has achieved to 2.08:1. The final optimized OMT has a length of 300 mm, shorter than a half of the popular quardruple‐ridged waveguide OMT. Measurements at room temperature agree well with simulation results, with a reflection coefficient below −10 dB for both polarizations and cross‐coupling levels of −30.5 dB over the whole required frequency range.
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