THz Ultra-wideband Passive Devices: Design, Simulation and Characterization
Licentiate thesis, 2021
As THz receivers mixers are implemented with thin-film technology, waveguide to substrate transitions have a fundamental role in the performance and bandwidth of such systems. The critical requirements for these transitions are a proper impedance matching and the minimization of insertion loss. In this thesis, a waveguide to slotline superconducting transition based on substrateless finlines is proposed. The transition was designed for prospective broadband SIS mixer design in the frequency range 211-375 GHz. The experimental verification at cryogenic temperatures shows a remarkable fractional bandwidth of 55%.
Although this transition represents a substantial improvement over existing designs, it is important to note that it transforms a waveguide propagation mode into slotline mode. For the majority of modern SIS mixers, microstrip line topology is the most suitable. Hence, the ongoing development is focused on broadband slotline to microstrip transitions. In this work, a slotline to microstrip transition based on Marchand Balun is designed, simulated and fabricated. The electromagnetic simulations showed promising results, and the cryogenic characterization at 4K is ongoing.
For most modern polarization-sensitive THz receivers, 90° waveguide twists are essential interconnection parts. Since compactness and low insertion loss are critical requirements, single step-twists have emerged as an attractive solution. In this work, a novel compact wideband 90-degree twist for the 140-220 GHz band is presented. Furthermore, the proposed twist has a performance tolerant to small geometry variation, and hence it is especially suited for fabrication by direct milling. The experimental verification shows 44% fractional bandwidth with return loss better than 20 dB over most of the band.
Broadband Waveguide to Substrate Transition
Compact waveguide twist
Cristian Daniel López
Chalmers, Space, Earth and Environment, Onsala Space Observatory, GARD Technology
Waveguide-to-substrate transition based on unilateral substrateless finline structure: Design, fabrication, and characterization
IEEE Transactions on Terahertz Science and Technology,; Vol. 10(2020)p. 668-676
Design and Implementation of a Compact 90 degrees Waveguide Twist With Machining Tolerant Layout
IEEE Microwave and Wireless Components Letters,; Vol. 30(2020)p. 741-744
Areas of Advance
Information and Communication Technology
Nanoscience and Nanotechnology (SO 2010-2017, EI 2018-)
Onsala Space Observatory
Astronomy, Astrophysics and Cosmology
Chalmers University of Technology
Opponent: Dr. Vessen Vassilev, Department of Microtechnology and Nanoscience, Microwave Electronics Laboratory