研究目的

Investigating the design and performance of a compact high-performance orthomode transducer (OMT) for the Atacama Large Millimeter Array (ALMA) Band 1 (31–45 GHz).

研究成果

The proposed design is suitable for scaling to sub-millimeter wavelengths. All four OMT prototypes show very good and almost identical performance. The return losses at the inputs and outputs of the four OMT prototypes are better than ?25 dB. Average insertion losses, at room temperature, are lower than 0.2 dB. Both polarizations and isolation levels between the two rectangular waveguide outputs are higher than 50 dB in the 30.5–45.5 GHz (37% bandwidth). Those excellent results meet the stringent requirements of ALMA Band 1. Furthermore, a very good reproducibility can be obtained during the manufacturing and assembling phases of the OMTs, demonstrating that mass production is feasible.

研究不足

The discrepancies observed across the band between the measured isolations are due to the difficulty - at the time of the measurements - of placing the absorbing material in the same way at the CWG inputs of the OMTs.