Tolerance analysis of octave bandwidth millimeter-wave planar orthomode transducer

Johannes Hubmayr; Jason E. Austermann; James A. Beall; Jake A. Connors; Shannon M. Duff; Jeffrey J. McMahon

doi:10.1117/12.2630174

31 August 2022 Tolerance analysis of octave bandwidth millimeter-wave planar orthomode transducer

Johannes Hubmayr, Jason E. Austermann, James A. Beall, Jake A. Connors, Shannon M. Duff, Jeffrey J. McMahon

Proceedings Volume 12190, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XI; 121901K (2022) https://doi.org/10.1117/12.2630174
Event: SPIE Astronomical Telescopes + Instrumentation, 2022, Montréal, Québec, Canada

Conference Poster

Abstract

Planar Orthomode Transducers (OMTs) are commonly used for polarization measurements at millimeter wave-lengths. We present an optical coupling study of an octave bandwidth planar OMT in circular waveguide based on 3D electromagnetic simulations. We quantify results through metrics such as co- and cross- polar coupling, reflection, and waveguide leakage as a function of the OMT construction geometry. We evaluate the tolerance of these metrics to the waveguide backshort distance, probe impedance, waveguide gap size, and waveguide-to-probe misalignment. Two probe geometries are studied: the ‘classic’ shape used in several previous experiments, and a new ‘wineglass’ geometry. The bandwidth ratio of both optimized OMTs is 2.0:1, defined where co-polar coupling exceeds 80%. The average co-polar coupling, cross-polar coupling, reflection, and waveguide leakage of the classic probe is approximately 93%, < -50 dB, 5% and 2%, respectively and depends slightly on the exact frequency range. The wineglass probe co-polar coupling is ∼ 2% larger. Radial waveguide misalignment at the level of 4% of the waveguide radius can result in up to a 10% reduction in co-polar coupling and -20 dB cross-polar coupling in one polarization. These results may be used to guide the detector module designs of future Cosmic Microwave Background experiments and beyond.

Citation Download Citation

Johannes Hubmayr, Jason E. Austermann, James A. Beall, Jake A. Connors, Shannon M. Duff, and Jeffrey J. McMahon "Tolerance analysis of octave bandwidth millimeter-wave planar orthomode transducer", Proc. SPIE 12190, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy XI, 121901K (31 August 2022); https://doi.org/10.1117/12.2630174

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