Design, fabrication and characterization of wideband waveguide terminations

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dc.contributor.authorFlosason, Karl Birkir
dc.contributor.departmentChalmers tekniska högskola / Institutionen för rymd-, geo- och miljövetenskapsv
dc.contributor.departmentChalmers University of Technology / Department of Space, Earth and Environmenten
dc.contributor.examinerBelitsky, Victor
dc.contributor.supervisorDesmaris, Vincent
dc.date.accessioned2024-11-14T07:26:01Z
dc.date.available2024-11-14T07:26:01Z
dc.date.issued2023
dc.date.submitted
dc.description.abstractThis thesis reports on two novel designs for high performance, wideband waveguide terminations for terahertz frequencies, demonstrated here in the range 210-370 GHz corresponding to ALMA bands 6-7. With advancing technology in the design and fabrication of high sensitivity radioastronomy receivers, each component and aspect of the system needs to be pushed to the limits when it comes to performance and bandwidth. The highest sensitivity and state-of-the-art receivers today for radioastronomy use 2SB mixer topologies, which require terminations to terminate the fourth port of a waveguide RF hybrid coupler. Reflections from that termination will both increase the level of noise generally but also risk introducing spectral line images or ghosts from the heterodyne downmixing process, which may cause confusion of spectral lines when the tools are used for spectroscopy. Minimizing the reflections from that waveguide termination is a step in improving over-all performance, and taking full advantage of increased performance of the 2SB topology. The goal of the project was to design, fabricate and measure two distinct and novel termination designs, fabricated with well established methods, and materials with known and reliable behaviours in cryogenic operation, and achieve the best possible performance over the widest possible bandwidth. One design based on an E-probe on quartz substrate, showing in simulations S11 < -26 dB over 270-370 GHz, and another design based on a tapered finline structure showing in simulations S11 < -37.5 dB over 220-390 GHz. Both designs use TiN resistive thin-film to dissipate the RF energy in ohmic losses. To validate and verify the design and fabrication process, the performance was then measured using a VNA and the required frequency extensions. Measuring reflection accurately at such low levels and at these frequencies is challenging, and the measurements are likely to underestimate the real performance. Uncertainties in the measurements are described and their scale evaluated both by measurements and simulation.
dc.identifier.coursecodeseex30
dc.identifier.urihttp://hdl.handle.net/20.500.12380/308983
dc.language.isoeng
dc.setspec.uppsokLifeEarthScience
dc.subjectTerahertz, waveguide termination, wideband, rf load, waveguide load, VNA, microwave metrology, reflection coefficient
dc.titleDesign, fabrication and characterization of wideband waveguide terminations
dc.type.degreeExamensarbete för masterexamensv
dc.type.degreeMaster's Thesisen
dc.type.uppsokH
local.programmeWireless, photonics and space engineering (MPWPS), MSc
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