Gain enhancement of conical horn by introducing bodies of revolution inside the horn

It is shown that enhancement of directivity of a conical horn can be obtained by inserting a metallic device inside the aperture. The results are comparable to those of lens-corrected horns. However, in the case of the introduction of a disc, rapid fluctuations of the directivity versus the distance L/sub d/ of the disc from the apex are observed. This indicates narrow-band behavior of the antenna. The other parameters, the radius and the thickness of the disc, are not critical. Enhancement over a larger L/sub d/ range can be achieved using a conical body which reduces the reflection wave effect. Aperture efficiencies of about 90% could be obtained by adding a metallic disc, which plays the role of a director. Nevertheless. the main drawback to date is that the aperture efficiency improvement is achieved in a narrow bandwidth.