Prof Stephen J Foti, Life Senior Member IEEE
IEEE Antennas & Propagation Society Member
The presentation will begin with a discussion of basic electromagnetic wave propagation in homogeneous media. Wave-front predictions using Huygens’ Principle will be reviewed. This will be followed by some examples of diffraction due to wave scattering by simple objects using Huygens’ Principle. Refraction of waves due to dielectric discontinuities including the occurrence of total internal reflection predictable by Snell’s Law when a wave travels from a dense to a less dense medium will be shown to cause the existence of a lateral wave at the interface when the angle of incidence is greater than or equal to the Critical Angle.
An apparent cylindrical wave-front paradox will then be considered. This occurs when an infinite line source of current exists at the interface between two dielectric media and the shape of the wave-front is to be determined. It will be explained that using simple ray tracing based upon the relative wave velocities in the media yields a discontinuous wave-front at the interface which violates the boundary conditions of Maxwell's equations. It will further be explained that forcing the wave-front to be continuous at the interface implies that the wave in the more dense medium must travel faster that the speed of light in the medium; hence, Special Relativity then appears to be violated. As with most paradoxes, the cause is an incorrect assumption. An overview of the mathematical solution to the problem will then provide a physical explanation of the phenomena and the unravelling of the paradox.
Time permitting, practical examples of antennas and systems using electromagnetic waves to achieve specific goals including: electronic countermeasures in defence, radiometric imaging for skin cancer detection and medical microwave imaging using diffraction tomography will be highlighted. Lastly, the general inverse scattering problem will be presented as a challenge for future research.
This presentation will be dedicated to the memory of the late Leopold B Felsen, Emeritus Professor of Electrophysics, Polytechnic Institute of Brooklyn, New York, USA.
Speaker's biography: Stephen J Foti received his BSc degree in Electrical Engineering and MSc degree in Electrophysics in 1969 and 1972 respectively, both from The Polytechnic Institute of Brooklyn, New York, USA. For the past eleven years he has been a university lecturer. He is currently Visiting Professor of Practise at Newcastle University, an Associate Lecturer at Northumbria University, Newcastle upon Tyne, England, and is also a consultant in RF, microwaves, antennas and microwave imaging techniques.
Prior to 2003, over a period of 34 years in industry, Professor Foti held engineering and management positions at ITT, Defence Communications Division; Cardion Electronics; LNR Communications; American Electronic Labs and Flam and Russell in the USA. In the United Kingdom, he was Technical Executive, Antenna Systems, at ERA Technology; Head of Engineering at CSA Wireless Systems; was a founder and Director & General Manager at Inotek and Technical Director of Thales Antennas (formally Racal Antennas). He was appointed to the COST 223 Committee: (European Co-operation in the Field of Scientific and Technical Research): Antennas in 90’s - Active Array Antennas for Future Satellite and Terrestrial Communications in the capacity of Expert representing the UK, 1989/1990.
Professor Foti is the author of a chapter in Medical Applications of Microwave Imaging, IEEE Press, New York, USA, 1986 and has over 40 technical publications and patents. Currently, Professor Foti's research interests include: Satcom-on-the-Move antennas, microwave imaging techniques for medical imaging and the detection of concealed weapons applications and SMART antennas in mobile telecommunications networks.
The slides from the talk are also available in PDF format (16MB).