Millimetre wave quasi-optical signal processing systems
Abstract
The development of spatial signal processing techniques at millimetre wavelengths represents an area of science and technology that is new. At optical wavelengths, spatial
signal processing techniques are well developed and are being applied to a variety of
situations. In particular they are being used in pattern recognition systems with a
great deal of success. At millimetre wavelengths, the kind of technology used for signal
transport and processing is typically either waveguide based or quasi-optically based,
or some hybrid of the two. It is the use of quasi-optical methods that opens up the
possibility of applying some of the spatial signal processing techiques that up to the
present time have almost exclusively been used at optical wavelengths.
A generic device that opens up this dimension of spatial signal processing to millimetre wave quasi-optical systems is at the heart of the work described within this
thesis. The device could be suitably called a millimetre wave quasi-optical spatial light
modulator (8LM), and is identical in operation to the spatial light modulators used in
many optical signal processing systems. Within this thesis both a theoretical and an
experimental analysis of a specific millimetre wave quasi-optical spatial light modulator
is undertaken. This thesis thus represents an attempt to open up this new area of research and development, and to establish for it, a helpful theoretical and experimental
foundation. It is an area that involves a heterogeneous mix of various technologies, and
it is an area that is full of potential.
The development of the experimental method for measuring the beam patterns
produced by millimetre wave quasi-optical spatial light modulators involved the separate development of two other components. Firstly, a sensitive, low-cost millimetre
wave pyroelectric detector has been developed and characterised. And secondly, a high
performance quasi-optical Faraday rotator (a polarisation rotator) has been developed
and characterised. The polarisation state of a quasi-optical beam is the parameter
most often exploited for signal processing applications in millimetre wave quasi-optical
systems, and thus a high performance polarisation rotator has readily found many
opportunities for use.
Type
Thesis, PhD Doctor of Philosophy
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