In recent years, Millimetre-Wave (MMW) frequencies (30-300 GHz) have been exploited for a variety of attractive applications such as astronomical observation, medical imaging, aircraft aided-control landing, security and concealed weapons detection. All this was also possible thanks to the advances in high frequency circuits where Monolithic Microwave Integrated Circuits (MMICs) represent a key factor. Systems working at MMW often use metal waveguides as interconnect elements and transitions are em- ployed to transfer the signals from these elements to the Radio Frequency (RF) circuits. The objective of this thesis is to design, fabricate and characterise electromagnetic transitions between rectangular waveguide (WR) and planar transmission lines at G-band frequencies (140-220 GHz). The first part of this work presents an overview of the electromagnetic properties of the atmosphere at MMW frequencies and their use for passive MMW imaging applications. Fundamental design concepts and prototypes of real-time imagers are also represented, based on the pioneering work carried out at QinetiQ Ltd. An extensive review of the scientific literature on waveguide transitions presents previous designs and architectures. The work proceeds through design, simulation, fabrication and measurements of G-band transitions highlighting advantages and disadvantages of different structures. The novel design of Elevated E-plane probes, used as waveguide to microstrip transitions in this work, extends the fabrication technique of MMIC air-bridges to build suspended metal structures and provides an additional optimising parameter to improve the reflection performance of the transition by decomposing the substrate influence on the metal probe. The innovative Elevated E-plane probe is fabricated on Semi-Insulated Gallium Arsenide (SI-GaAs) and it is MMIC-integrated, reducing system complexity and optimizing fabrication and assembly costs. The core of the thesis details the fabrication processes and procedures and a separate section describes the manufacture of G-band rectangular waveguide blocks that host the transitions. The overall fabrication is carried out using in-house facilities at the University of Glasgow without the aid of external facilities. Measured results are presented and discussed, validating design and simulations. This work has led to a successful design and fabrication of GaAs-integrated rectangular waveg- uide to microstrip line transition at G-band.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:550693 |
| Date | January 2012 |
| Creators | Donadio, Oberdan |
| Publisher | University of Glasgow |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://theses.gla.ac.uk/3354/ |
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