Radial Line Transducer

Abstract

The purpose of this paper is to give a new excitation method of a radial-electromagnetic wave by a metallic cylinder with elliptical cross section. It was ascertained [1] that the radial wave propagates in a medium of permeability of quantity µ/sub perp/. The quantity µ/sub perp/ is given by µ/sub perp/ = ( µ/sup 2/ - kappa)/µ, where µ and kappa are the diagonal and nondiagonal components of the tensor permeability of a gyrotropic medium, respectively. The radial wave has interesting properties that this mode has not cutoff below the critical frequency omega = gamma( BH)/sup 1 / 2/, where omega is the angular frequency, gamma = 1.76 x 10/sup 7/ ((oe s)/sup -1/ in CGS unit), B = µ/sub 0/(H + M/sub s/), the magnetic flux density, H the magnetic field, and M, the saturation magnetization. Ganguly and Webb [2] presented an initial theory and some experiments for a magnetostatic surface wave single bar transducer. These investigations have concluded that the lowest operating frequency of Ganguly-type delay line is gamma(BH)/sup 1 / 2/. Below this cutoff, no surface modes can exist. In view of the above, investigation of a radial wave type delay line should produce developments in low frequency microwave (0.5 to 1.5 GHz) applications.