Abstract

Radiation and reception from antennas near or on buildings or ships is usually partially blocked by local obstacles, often of geometrical shape.  Analysis of scattering by these obstacles cannot assume plane wave incidence because they are local and cannot assume omnidirectional sources if the antenna is directive.  Consequently effective placement of antennas to reduce the effect of this blocking traditionally has been determined experimentally.

Here an efficient numerical solution is described. It uses a superposition of elementary beam scattering solutions. This beam array spacing is selected and amplitudes chosen such that in the absence of the scatterer it produces the radiation pattern of the antenna in the the near and far field. This can be done to any required accuracy if enough sources are used, but for efficiency we select an  arrangement to minimize the required number of beams. Each beam scattering solution can be exact if the geometry of the scatterer is simple, for example a moderately small conducting cylinder or a conducting half plane or wedge, or it can be an accurate high frequency solution involving combinations of these structures using the uniform geometrical theory of diffraction for large conducting rectangular cylinders (four 90 degree conducting wedges). This allows us to model two-dimensional propagation of antenna beams around simple structures with conducting surfaces of almost any size to almost required accuracy.

Extensions to imperfectly conducting building surfaces are now being investigated.  Here more approximations are necessary, but these solutions have the interesting additional feature of surface waves which can propagate along the building surfaces and can provide the main source of radio reception in the shadow of buildings close to their surface.
 

About the Speaker:

Edward Jull received a B.Sc. degree in engineering physics from Queen's University in 1956, a Ph.D. in electrical engineering in 1960 and a D.Sc.(Eng.) in 1979, both from the University of London. He was employed as a summer student in antenna research in the Radio and Electrical Engineering Division of the National Research Council Laboratories, Ottawa in 1955 and returned there as junior, assistant and associate research officer in 1956-57 and 1961-72, in the microwave and later the antenna engineering sections. During this period he was also a sessional lecturer at Queen's and Carleton Universities. He was a guest researcher in the laboratory of electromagnetic theory of the Technical University of Denmark, Lyngby in the microwave department of the Royal Institute of Technology, Stockholm in 1963-65. Since 1972 he has been with the department of electrical engineering of the University of British Columbia as associate and full professor.

His main research contributions have been to near field/ far field antenna problems and to high frequency
diffraction solutions and their application to aperture antennas.  He is the author of a book on these subjects. He is a Life Fellow of the IEEE and was president of the International Union of Radio Science (URSI) from 1990-1993.
 
No-Host Dinner

You can meet the featured speaker at a no-host dinner before the talk.  Meet us at 6:00 PM at Earl's, 4361
Kingsway (one block west of Willingdon) in Burnaby.  All are welcome, although advance notice to Dave
Michelson <dmichelson@ieee.org> would be appreciated so that we can ask for a table of appropriate size.