Microfabricated Waveguide Terminations for Wideband and Low-power THz Applications
Journal article, 2024

This paper presents the design, simulation, microfabrication, and characterization of broadband waveguide terminations intended as drop-in components in waveguide blocks. Two types of terminations were developed, fabricated and characterized. The first type employs a quartz-based E-probe to couple to a waveguide, integrating an on-substrate titanium nitride (Ti-N) alloy resistive absorber with broadband tuning circuitry. This design achieves a return loss of better than 20 dB over the 260-375 GHz frequency range. The second type features a finline to slotline transition, constructed from a 30 μm thick Si membrane covered with high resistivity Ti-N alloy. This load demonstrates a return loss of better than 20 dB across the 210-380 GHz band. In order to ensure the required performance of the loads at cryogenic temperatures, the sheet resistance of the employed Ti-N resistive film was characterized from room temperature to 4K employing a closed-cycle cryostat and a 4-probe measurement system. For comparative purposes, the room temperature performance of terminations employing a traditional EccosorbTM material was measured and compared with the proposed waveguide terminations. Furthermore, the sideband rejection ratio SBRR of a 2SB SIS mixer was evaluated at cryogenic temperatures using the proposed finline-based terminations for LO directional couplers and 90° RF hybrids in comparison with the EccosorbTM made terminations. The measurements showed that the performance of the proposed terminations outperforms those achieved with Eccosorb™ absorbers at room temperature and is comparable at cryogenic temperatures.

noise temperature

finline

waveguides

Microfabrication

E-probe

load

2SB SIS mixer

Eccosorb TM

Terahertz

Author

Cristian Daniel López

Chalmers, Space, Earth and Environment, Onsala Space Observatory

Karl Birkir Flosason

Student at Chalmers

Denis Meledin

Chalmers, Space, Earth and Environment, Onsala Space Observatory

Leif Helldner

Chalmers, Space, Earth and Environment, Onsala Space Observatory

Sven-Erik Ferm

Chalmers, Space, Earth and Environment, Onsala Space Observatory

Victor Belitsky

Chalmers, Space, Earth and Environment, Onsala Space Observatory

Vincent Desmaris

Chalmers, Space, Earth and Environment, Onsala Space Observatory

IEEE Transactions on Terahertz Science and Technology

2156-342X (ISSN) 21563446 (eISSN)

Vol. In Press

Subject Categories (SSIF 2025)

Other Electrical Engineering, Electronic Engineering, Information Engineering

DOI

10.1109/TTHZ.2024.3510658

More information

Latest update

3/28/2025