The influence of air-gap tolerances on the admittance of a dielectric-coated slot antenna

The admittance of a TEM mode-excited parallel-plate aperture having an infinite flange and illuminating a displaced dielectric boundary is determined by the variational method. The results are applied to provide insight into the following two problems of interest: 1) the effect of an air gap on the admittance of dielectric-coated aperture antennas, and 2) the admittance of an aperture antenna coated with an underdense plasma slab. Numerical computations for the air-gap problem are verified experimentally.