Receiver front-end circuits and components for millimetre and submillimetre wavelengths

Abstract

This dissertation focuses on the development of millimetre- and submillimetre-wave receiver front-end circuits and components. Seven scientific articles, written by the author, present this development work. A short introduction to the technology related to the designs of the thesis precedes the articles. The articles comprise several novel structures and techniques intended to further improve the performance of receivers or to provide new ways for receiver circuit implementation, summarised as follows.

1) Novel rectangular waveguide-to-CPW waveguide transition using a probe structure. The measured insertion and return loss of an X-band (8.2-12.4 GHz) back-to-back structure are less than 0.5 dB and more than 17 dB, respectively, over the entire frequency band (fractional bandwidth of > 40 %). The transition is used in a submm-wave mixer.

2) Novel rectangular waveguide-to-CPW transition using a fin-line taper. The measured insertion and return loss of an X-band (8.2-12.4 GHz) back-to-back structure are less than 0.4 dB and more than 16 dB, respectively, over the entire frequency band.

3) Novel tunable waveguide backshort based on a fixed waveguide short and movable dielectric slab. The measured return loss for a W-band backshort is less than 0.21 dB (VSWR > 82) over the entire frequency band of 75-110 GHz.

4) New coaxial bias T. The insertion loss is less than 0.5 dB at 3-16 GHz (fractional bandwidth of 137 %) and 0.1 dB at 5.2-14.1 GHz. In the latter range, the return loss is more than 30 dB. The RF isolation is greater than 30 dB at 1-17 GHz.

5) First millimetre-wave subharmonic waveguide mixer using European quasi-vertical Schottky diodes. The mixer utilises a single diode chip with quartz filters in a four-tuner waveguide housing. A single-sideband noise temperature of 3500 K and conversion loss of 9.2 dB (antenna loss included) have been measured at 215 GHz with an LO power of 3.5 mW.

6) Balanced-type fifth-harmonic submillimetre-wave mixer. It uses two planar Schottky diodes, quartz filters, and a tuner-less in-line waveguide housing with an integrated diagonal horn antenna and new LO transition structure. The designed RF range is 500-700 GHz enabling the use of an LO source at 100-140 GHz. A conversion loss of about 27 dB has been measured at 650 GHz with an LO power of 10 mW. The mixer has been in use in phase locking of a submm-wave signal source.

7) Characterisation procedure of planar Schottky diodes with extensive dc, capacitance, and wide-band (up to 220 GHz) S-parameter measurements and parameter extraction. Parameters of a simple diode equivalent circuit and results of extensive measurements are available for designers and diode manufacturers for further use.