On the fields in a conical horn having an arbitrary wall impedance

The electromagnetic fields propagating up a cone having an arbitrary wall impedance are found using an asymptotic solution. Three special cases are then considered: the smooth-metal wall, the corrugated wall, and the metal wall with a lossy-dielectric lining. The last case, in the form of an absorber-lining is then shown to behave like a corrugated horn since it too provides a highly tapered -plane and -plane aperture distribution. Furthermore, it does this over a much larger bandwidth, over 3:1, with negligible gain drop.