Design and Measurement of a Bandwidth Enhanced Quad-Ridged OMT

Abstract

Orthomode transducers form an integral part of any receiver system, especially for high sensitivity, wideband applications such as reflector feed antennas for radio astronomy. This paper presents an improvement on the quadruple-ridged OMT that has formed the basis for many high performance reflector feeds systems. The improvement relies on the freedom offered by SLM 3D-printing to design quadruple-ridged waveguides with a wider single mode bandwidth than conventional square/circular ridged waveguides. A prototype quad-ridged OMT is designed and manufactured to operate over 3.5 - 12.3 GHz, the ngVLA Band 2. The manufacturing and measurement of the prototype is discussed in detail with recommendations for future designs. The basic design of the proposed OMT can be customised to attain good performance over more than a decade bandwidth, or used as a basis for high performance narrowband applications.