Hugh Griffiths was born in Bournemouth, UK, in 1956. He was educated at Hardye's School, Dorchester, and Keble College, Oxford University, where he received the MA degree in Physics. He also received the PhD (1986) and DSc(Eng) (2000) degrees from the University of London.

In 2006 he was appointed Principal of the Defence College of Management and Technology, Shrivenham (part of Cranfield University). From 1982 to 2006 he was with University College London, serving as Head of the Department of Electronic and Electrical Engineering from 2001 to 2006. His research interests include radar sensor systems and signal processing (particularly synthetic aperture radar and bistatic and multistatic radar and sonar) as well as antennas and antenna measurement techniques. He has published over 300 papers and technical articles on these subjects.
He received the IERE Lord Brabazon Premium in 1984, the IEE Mountbatten and Maxwell Premiums in 1996, and the IEEE Nathanson Award in 1996. He serves on the IEEE AESS Board of Governors and as Chairman of the IEEE AESS Radar Systems Panel, and as Editor-in-Chief of IEE Proceedings on Radar, Sonar and Navigation. Also, he was Chairman of the IEE International Radar Conference RADAR 2002 in Edinburgh, UK. He is also a member of the Defence Scientific Advisory Council for the UK Ministry of Defence, and of the Supervisory Board for the UK Ministry of Defence's Defence Technology Centre in ElectroMagnetic Remote Sensing.

He is a Fellow of the IEE, Fellow of the IEEE, and in 1997 he was elected to Fellowship of the Royal Academy of Engineering.

Contact Information:

Thales/Royal Academy of Engineering Chair of RF Sensors
University College London
Gower Street
London
WC1E 6BT
United Kingdom
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Lectures:

Bistatic & Multistatic Radar

Bistatic and multistatic radar systems have been studied and built since the earliest days of radar. As an early example, the Germans used the British Chain Home radars as illuminators for their Klein Heidelberg bistatic system. Bistatic radars have some obvious advantages. The receiving systems are passive, and hence undetectable. The receiving systems are also potentially simple and cheap. Bistatic radar may also have a counter-stealth capability, since target shaping to reduce target monostatic RCS will in general not reduce the bistatic RCS.
Furthermore, bistatic radar systems can utilize VHF and UHF broadcast and communications signals as 'illuminators of opportunity', at which frequencies target stealth treatment is likely to be less effective.

Bistatic systems have some disadvantages. The geometry is more complicated than that of monostatic systems. It is necessary to provide some form of synchronization between transmitter and receiver, in respect of transmitter azimuth angle, instant of pulse transmission, and (for coherent processing) transmit signal phase. Receivers which use transmitters which scan in azimuth will probably have to utilize 'pulse chasing' processing.

Over the years a number of bistatic and multistatic radar systems have been built and evaluated. However, rather few have progressed beyond the 'technology demonstrator' phase. Willis, in his book Bistatic Radar, has remarked that interest in bistatic radar tends to vary on a period of approximately fifteen years, and that currently we are at a peak of that cycle. The purpose of this lecture is therefore to present a subjective review of the properties and current developments in the subject, with particular emphasis on 'passive coherent location' and to consider whether or not the present interest is just another peak in the cycle. It draws on material in the book Advances in Bistatic Radar, edited by Willis and Griffiths, and recently published by SciTech.

Synthetic Aperture Radar

The techniques of aperture synthesis have their origins in radioastronomy, and Ryle and Hewish were awarded the Nobel Prize for Physics for their work in this field. At much the same time (the early1950s) it had also been realized that the cross-range resolution of a sideways-looking airborne radar (SLAR) could be improved by filtering (a technique known as Doppler beam-sharpening). These ideas were pursued and developed at the University of Illinois, and at the Willow Run Laboratory of the University of Michigan (the forerunner of the Environmental Research Institute of Michigan - ERIM). Since then numerous laboratories and organisations have built and operated SAR systems. Of course, before the advent of fast digital computers, the processing of the raw data to form the images had to be done by analogue processing - usually optically. Nowadays digital processing is almost universally used, and real-time processing is relatively straightforward.

The first spaceborne SAR system was carried by NASA's SEASAT satellite in 1978. This only lasted for 3 months, when a massive power supply fault cut short its life. Nevertheless, this provided a wealth of data (much of which still remains to be properly analysed), and demonstrated the value of spaceborne SAR for a wide variety of applications in environmental monitoring. Subsequently NASA, the European Space Agency, Japan, Canada and several other Agencies have built and flown satellite SAR systems of increasing sophistication, now often with multiple frequency bands and polarimetric capability. In parallel, data interpretation techniques have progressed - indeed, it has been suggested that the extraction of quantitative information from SAR imagery represents the greatest current problem.

Aircraft-borne SAR is used both for remote sensing, and for high-resolution military surveillance. Resolution of the order of centimetres can be achieved with spotlight-mode operation, and target detection and recognition algorithms are being developed, as well as MTI to separate moving targets from stationary clutter. At such high resolution, characterisation and correction of motion errors becomes more and more important.

Interferometric SAR is currently a very active area of SAR research and development. The technique was first demonstrated with airborne SAR back in the 1970s, but subsequently it has been widely used with spaceborne SAR for high-resolution topographic mapping. With aircraft-borne systems there is the potential to recognise targets from their 3-D signatures.
Differential interferometry has demonstrated remarkable results in detecting changes in topography caused, for example, by earthquakes and volcanoes.

Finally, synthetic aperture techniques have also been applied in the field of sonar, to give high-resolution maps of the seabed, for applications such as the detection of wrecks, in the oil industry, and for the detection of mines. The principles are very similar, but the velocity of sound in water is very much slower (~1500m/s), which introduces certain problems, and the propagation of sound through water is strongly influenced by variations in temperature and salinity.

This lecture gives a subjective and selective overview of some current topics and results in modern synthetic aperture radar.