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An Exploration of Radiation Physics

April 6, 2017 @ 6:00 pm - 8:00 pm

All external electromagnetic fields arise from the process of radiation. There would be no radiated, propagated or scattered fields were it not for this phenomenon. In spite of this self-evident truth, our understanding of how and why radiation occurs seems relatively superficial from a practical viewpoint. It’s true that physical reasoning and mathematical analysis via the Lienard-Wiechert potentials show that radiation occurs due to charge acceleration. It’s also true that it is possible to determine the near and far fields of rather complex objects subject to arbitrary excitation, making it possible to perform analysis and design of EM systems. However, if the task is to determine the spatial distribution of radiation from the surface of a given object from such solutions, the answer becomes less obvious.

 

One way to think about this problem might be to ask, were our eyes sensitive to X-band frequencies and capable of resolving source distributions a few wavelengths in extent, what would be the image of such simple objects as dipoles, circular loops, conical spirals, log-periodic structures, continuous conducting surfaces, etc. when excited as antennas or scatterers? Various kinds of measurements, analyses and computations have been made over the years that bear on this question. This lecture will summarize some relevant observations concerning radiation physics in both the time and frequency domains for a variety of observables, noting that there is no unanimity of opinion about some of these issues. Included in the discussion will be various energy measures related to radiation, the implications of Poynting-vector fields along and near wire objects, and the inferences that can be made from far radiation fields. Associated with the latter, a technique developed by the author called FARS (Far-field Analysis of Radiation Sources) will be summarized and demonstrated in both the frequency and time domains for a variety of simple geometries. Also to be discussed is the so-called E-field kink model, an approach that illustrates graphically the physical behavior encapsulated in the Lienard-Wiechert potentials as illustrated below. Brief computer movies based on the kink model will be included for several different kinds of charge motion to demonstrate the radiation process.

Speaker(s): Dr. Edmund Miller,

Location:
Room: EV12.163
Bldg: EV Building 12th Floor
Concordia University
1515 St. Catherine W.
Montreal, Quebec
H3G 2W1

Details

Date:
April 6, 2017
Time:
6:00 pm - 8:00 pm
Website:
http://events.vtools.ieee.org/m/44614

Organizer

[email protected]

Venue

Room: EV12.163, Bldg: EV Building 12th Floor