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Antennas and Radio-Frequency Electromagnetics: Some Interesting Problems and Projects from Four Decades of Study


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Antennas and Radio-Frequency Electromagnetics: Some Interesting Problems and Projects from Four Decades of Study

Date and Time

12 March 2014 - 18:30-20:00


ST. ASAPH, United Kingdom - icon_popup  (See map)


Organised by the Wales North local network.

About this event

The Wales North IET telecommunications lecture will take place on Wednesday 12th March 2014 at Glyndwr Optic at St Asaph. The lecture will start at 18:30 with complimentary refreshments available from 18:00. Our guest speaker will be Professor Peter Excell who is Professor of Communications and Dean of the Arts, Science and Technology Faculty at Glyndwr University.

The speaker first became interested in radio-frequency electromagnetics through studies of an unusual hazard problem: the (very small) risk of ignition of flammable mixtures by sparks on structures acting as receiving antennas. This involved using engineering judgement to decide what sort of antenna could be formed by typical industrial structures and then using electromagnetic analysis to predict their behaviour. This started by using classical analytical approaches, but computational modelling methods began to become available in the late 1970s, which enabled far more complex and detailed studies to be undertaken. Another strand of this work involved computation of the electromagnetic field distribution around a pointed electrode in an experimental spark gap, eking out the power of what was then regarded as a leading edge supercomputer to magnify the fine detail at the tip of the point.

Expanding from this work into general aspects of electromagnetic compatibility (i.e. undesired electromagnetic effects), the next study undertaken was ways of testing aircraft for their immunity to strong radio frequency fields. The concept of the plane wave spectrum was exploited to understand the interaction and from this the idea of using a parabolic reflector close to the aircraft to form a "compact range" was devised. This has subsequently become a standard procedure for testing of military aircraft.

To test models of this concept, an anechoic chamber was created at the speaker's University and this will be described. A novel concept to replace the parabolic reflector by an array of simpler antennas was then devised and sophisticated optimisation programs had to be used to deduce the amplitudes of the signals to be applied to each element in the array. Later, an early application of genetic algorithms was used to refine the physical design of the array. The elements used in the array were "log periodic antennas" and it was noted that they caused dispersion ("smearing") of signals with a wide bandwidth: a completely original design of antenna was devised to overcome this problem. This was simulated with a novel software package and then tested in hardware and shown to achieve the desired objectives: this design has now been patented around the world and ideas for its exploitation are being developed.

Later projects have mainly tended to focus on the design of antennas for mobile phones, including very compact designs to reduce the amount of energy sent in the direction of the user's head, designs to reduce the disturbing effect of the user's head and hand and designs for communication with satellites. To support this work, a more challenging problem has been the modelling of the human head and hand and this has stretched the limits of the computer power of the day: it also required the development of a novel method to combine two very heterogeneous formulations that are suited to either the human head or the man-made mobile phone: the principles of this will be explained.

Finally, a related project undertaken in collaboration with the University of Maryland will be described. This was an experiment to test for the possibility of demodulation of radio waves (e.g. from mobile phones) in biological tissue: a convincing null result was obtained.


18:00 Complimentary refreshments
18:30 Lecture starts



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