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Submillimeter-Wave Waveguide Frontends by Silicon-on-Insulator Micromachining

Time: Fri 2020-06-12 16.00

Location: zoom link for defense (English)

Subject area: Electrical Engineering

Doctoral student: Adrian Gomez-Torrent , Mikro- och nanosystemteknik

Opponent: Dr. Goutam Chattopadhyay, NASA Jet Propulsion Lab (JPL)

Supervisor: Professor Joachim Oberhammer, Mikro- och nanosystemteknik; Umer Shah, Mikro- och nanosystemteknik

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This thesis presents novel radiofrequency (RF) frontend components in the submillimeter-wave (sub-mmW) range implemented by silicon micromachining, or deep reactive ion etching (DRIE). DRIE is rapidly becoming a driving technology for the fabrication of waveguide components and systems when approaching the terahertz (THz) frequency range. The conventional method to manufacture microwave waveguide components, CNC-milling, shows important limitations when used at sub-mmW frequencies or above, due to the reduced size of the waveguides. At the same time, the classic electromagnetic designs, oriented to CNC-milling, are often not suitable for their fabrication using alternative technologies. The work in this thesis aims to develop fabrication-oriented electromagnetic structures, making use of the full flexibility of silicon on insulator (SOI) micromachining, and enabling the implementation of complex RF frontends at a low fabrication complexity.

The first part of the thesis reports on a turnstile orthomode transducer (OMT) in the WM-864 band (220 – 330 GHz). OMTs are key components in the feed-chain for radio astronomy, communications, or radiometry applications. However, their complex geometry has often limited their use when approaching the THz range, where polarization diversity is commonly avoided, or optical systems are preferred.

The second part reports on a high-gain and broadband waveguide corporatefed array antenna in the WM-570 band (330 – 500 GHz). High gain and broadband antennas are required for the future generation of THz wireless communications. Reflector and lens antennas can meet these specifications, but their fabrication for the THz range requires precision machining, resultingin a high cost, low yield, and small scale production. The use of silicon micromachined antenna arrays overcomes these issues while providing a more compact frontend.

In the third part of the thesis, a parallel plate waveguide (PPW) leaky wave antenna (LWA) fed by a quasi-optical beamforming network (BFN) in the WM-864 band is presented. The antenna frontend generates a pencil shaped beam scanning in elevation. The compact design, large bandwidth, and beam steering capabilities make this antenna a suitable frontend for THz radar applications.

The final part of this thesis reports on a novel waveguide single pole double throw (SPDT) switch in the WM-570 band. The switch is demonstrated in a two-port network configuration with two switching states (ON/LOAD), used for receiver calibration, or for avoiding backward waves in transmitter switching. A more complex 1×4 switching matrix is also designed for the implementation of an active radar antenna operating at 340 GHz.