Abstract :
The principle of the Fresnel zone plate has been well known for over 100 years and applied over the electromagnetic spectrum from millimetre wavelengths to X-rays. Its microwave possibilities, however, appear to have received little attention before 1962, when Van Buskirk and Hendrix proposed its use for satellite communications and as an inexpensive means of making large radio telescopes. All the work referenced is based on circular zone patterns, but it was pointed out to the author by K. Milne that the technique could equally be employed when the circles were projected into any plane arbitrarily inclined to the line-of-sight to the source, thus giving a set of ellipses. This is particularly useful for satellite reception since it provides an antenna which can be mounted vertically on a wall or window, on a sloping or flat roof, or on the ground
