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.
Benefits: Orthomode transducers (OMTs) are essential basic components needed to support the advanced measurements being planned by NASA researchers. They are widely used by NASA and radio astronomers for the detection and analysis of polarized radio waves from celestial sources. The OMT separates orthogonal polarization modes of incoming electromagnetic waves, enabling the study of the polarization properties of radio signals with high precision. OMTs allow the measurement of 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 instrumentation for the study of the Cosmic Microwave Background (CMB) radiation. CMB polarization can provide insights into the early universe, including information about inflation and the large-scale structure of the cosmos. High-precision OMTs are essential for minimizing cross-polarization and ensuring accurate measurements. OMTs are an essential component found in scientific instruments used in the Galactic Emission Mapping (GEM) project to map the polarized emission from our galaxy. The GEM maps help to distinguish between different sources of radio emission, such as synchrotron radiation and thermal emission, and are crucial for decontaminating CMB data. Other applications for OMTs include NASA’s EOS instruments targeting mm-wave and terahertz frequencies such as radar systems for measuring precipitation in clouds, upper atmospheric monitoring, topography measurement, surface water monitoring, soil moisture, and global snow coverage. OMTs may find use in airborne science systems such as NASA Cloud Radar System (CRS) high altitude aircraft and APR-3 precipitation radar. OMTs find application in atmospheric pressure radar/radiometers and other instruments developed under the NASA Earth Science Technology Office (ESTO) Instrument Incubator Program (IIP). Orthomode transducers (OMTs) are fundamental components that find application in a wide array of microwave, millimeter-wave (MMW), and terahertz systems. They are waveguide components that combine/separate two orthogonally polarized signals. They are used in MMW telecommunications systems. One example is Very Small Aperture Terminal (VSAT) systems. In VSAT, 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 is used to increase the aggregate data throughput between two dishes on a point to point microwave path and for fault-tolerance redundancy. Certain types of outdoor microwave radios have integrated orthomode transducers and operate in both polarities from a single radio unit, performing cross-polarization interference cancellation within the radio unit itself. Alternatively, the orthomode transducer may be built into the antenna, and allow connection of separate radios, or separate ports of the same radio, to the antenna. OMTs are used to improve the detection of aircraft and weather phenomena in radar systems by isolating polarizations. The proposed OMT development will extend the commercial availability of OMTs to the lower terahertz frequencies. The new OMTs will offer significantly enhanced performance at MMW frequencies. They will enhance the performance of existing systems and enable designers to extend their deployment to higher MMW and terahertz frequencies.