Abstract. In a dielectric medium between parallel flat conductors it is usual to consider high-frequency wave propagation in terms of TEM theory, and this is certainly applicable with good accuracy when the separation between the surfaces exceeds about one-thousandth of an inch. For smaller separations the surface-wave content of the field becomes a significant factor, even for smooth, bare metal boundaries. Ultimately the transverse field decay across the width of the slot becomes dominant and causes a rapid increase in both the attenuation and phase-change coefficients. The situation may be interpreted physically as a direct consequence of the need to maintain, within a very small space, the electric field in the direction of propagation of the wave. This behaviour is examined, and illustrated by considering specific examples.

Print publication: Issue 8 (21 May 1973)
Received 18 January 1973