Terahertz Orthomode Transducers

The proposed research effort seeks to develop terahertz orthomode transducers (OMTs) suitable for use in sensitive NASA instruments. Prototypes will be developed in the WR-2.8 band 260-400 GHz. Phase I funding will be used primarily for salaries and to cover some of the prototype fabrication costs. OMTs combine/separate two orthogonally polarized signals. They find use in microwave and millimeter-wave (MMW) telecommunications systems. One example is Very Small Aperture Terminal (VSAT) systems where the transmission and reception paths are at 90° with respect to each other. This orthogonal orientation provides very high isolation between the two signals. The OMT protects the receiver or low noise block downconverter from the high output power of the block upconverter. OMTs are also found in terrestrial microwave radio links. A pair of parabolic reflectors operate in a point-to-point microwave radio path using four radios (two at each end). OMTs are mounted at the parabolic feed, separating the signal from the feed into two separate radios, one operating in the horizontal polarity, and the other in the vertical polarity. This arrangement increases the aggregate data throughput. OMTs are widely used by NASA and radio astronomers for the detection and analysis of polarized radio waves from celestial sources. By separating the orthogonal polarization components, OMTs allow astronomers to measure the Stokes parameters, which describe the polarization state of the electromagnetic waves. This information is vital for understanding the magnetic fields in various astronomical objects and the interstellar medium. OMTs are used in experiments studying the Cosmic Microwave Background radiation. CMB polarization can provide insights into the early universe, including information about inflation and the large-scale structure of the cosmos. Another example is the Galactic Emission Mapping (GEM) project where OMTs are used to map the polarized emission from our galaxy.