A compact high-performance orthomode transducer for the Atacama large millimeter array (ALMA) band 1 (31–45 GHz)

This paper describes a compact high-performance orthomode transducer (OMT) with a circular waveguide input and two rectangular waveguide outputs based on the superimposition of three aluminum blocks. Several prototypes operating in the band 1 (31–45 GHz) of the atacama large millimeter array have been fabricated and measured. The design is based on the use of a turnstile junction that is machined in a single block, requiring neither alignment nor a high degree of mechanical tolerances. Thus, a high repeatability of the design is possible for mass production. Across the 31–45 GHz band, the isolation is better than 50 dB and the return losses at the input and outputs of the OMT are better than −25 dB.