A rectangular horn of four corrugated plates

We describe a rectangular horn with radiation characteristics similar to those commonly obtained with corrugated horns of circular aperture. The horn described here consists of four identical plates, whose grooves can be obtained (straightforwardly and accurately) by numerical machining. Measurements from 8.7 to 12.2 GHz show that the horn aperture illumination is given to a good approximation by the distribution cos (
\alpha x
) cos (
\gamma y
) in agreement with a previous asymptotic theory. An advantage of this horn over a circular horn is that different beamwidths are obtainable in the two principal planes.