Novel Orthomode Transducer Scalable to Terahertz Frequencies

We present the design of a novel orthomode transducer, OMT, suitable for scaling up to Terahertz frequencies. The current design aims for the frequency band 270-380 GHz. The OMT combines waveguide components made with conventional milling with substrate-based parts fabricated using microfabrication techniques. This allows critical dimensions of the OMT conventionally to be mechanically machined parts being replaced by photolithographically defined and microfabricated structures. The paper provides details on the OMT layout, simulations, fabrication and tests. The two fabricated and tested prototype OMTs show similar performance providing better than 30 dB cross-pol suppression. The OMTs also demonstrated broadband performance with an operational band of 260-385 GHz corresponding to a 38,8% fractional bandwidth. With the microfabricated polarization splitting junction and relatively simple waveguide circuitry, the OMT has very good potential to be scaled up to higher frequencies, probably up to 1.5 THz.