antenna-theory.com

[Riaan]

Dear all,

Some years ago I published a paper in which I pointed out that the concept of placing a conductor in the null field of an aperture antenna problem is invalid. This paper has, however, been ignored completely by all and sundry. I have posted it at the link below for comment. Please let me know what you think.

http://www.riaanbooysen.com/professional

[Riaan]

I recently decided to submit a follow-on article on the use of the equivalence principle in aperture problems. I had come to the conclusion that the conventional technique, in which a conductor is placed in the null region and the problem-specific Green's function has to be solved for, is not incorrect as I originally believed. Instead, this realization allowed me to derive a much simpler proof of my proposition that in contrast to what the textbooks claim, one can use the free space radiation integrals to solve aperture problems of arbitrary geometry.

The paper is still under review, but I show a nice example from it here, first topic. Practically impossible to calculate the Green's function of the second geometry, easy to solve with free space radiation integrals. Let me know what you think!

[Riaan]

Dear fellow members,

When I last posted about this topic on this forum (I was truly shocked to see that it was almost 6 years ago), I had in the back of my mind that should I one day succeed in having the follow-on article published, I should list it again for comment. About six months or so ago I decided to have a go at it again and I subsequently managed to figure out a couple of my own misconceptions, as well as a significantly improved motivation for this new theory of mine. It was recently published in the ACES journal (you can download it from my website here or directly from ACES here), and the reviews have been quite positive,

"The approach proposed by the author is original and interesting", "Good finding and contribution", "The readability of the manuscript is excellent and the theoretical developments are clearly reported", "I think that this study is excellent and examples are enough and clear."

Most significantly, though, was the comment I received from Professor Warren Stutzman, of the Stutzman & Thiele Antenna Theory and Design textbook fame, who commented that although he had not read through it in great depth, it “looks pretty good.” Not unexpectedly he made the keen observation that the theory “rests on image theory being valid for arbitrary surfaces. The limitations on this would be hard to predict.”

The point I make and demonstrate in the second article is that when an electric surface current density is backed infinitely close by an electric conductor, the boundary condition of a zero tangential electric field component at the surface of the conductor can only be met if an oppositely directed electric surface current density is induced on the surface of the conductor. This is true irrespective of the shape of the conductor or equivalent surface on which the surface current density is defined.

The images below show, as an example, (a) a reflector illuminated by line source and (b) an equivalent circular aperture with only a magnetic current density as source. The radiation patterns calculated by these two vastly different approaches are almost indistinguishable.



(a) (b)



Radiation patterns

One of the five reviewers stated that the theory I presented does not contribute much to the state of the art, possibly implying that it is already being used in calculations somewhere? I am not aware of any publications or EM software packages that employ magnetic sources in this manner. I would be most grateful if you could list any such references, not only for my own benefit, but also for those who are still under the impression that the free space radiation integrals cannot be used in conjunction with a short-circuited aperture as stated in practically all antenna textbooks.