ACOUSTIC WAVES AND THEIR EFFECTS ON ANTENNA IMPEDANCE

Abstract

Expressions have been derived for the terminal admittance of a biconical dipole encased in a dielectric sphere which is immersed in a warm plasma. A linearized hydrodynamic description is used for the plasma. For thin-angle cones an exact expression is derived. For thick-angle cones the terminal admittance is related to the aperture fields at the spherical boundary of the cones by means of a variational expression. The admittance was found to be strongly dependent on the ratio of the velocity of light in free space to the acoustic velocity in the plasma. Compressibility effects seem to be quite significant if the acoustical "phase length" of the antenna is between approximately 0.5 and 10.