Theory of dielectric-filled edge-slot antennas

A theory has been developed for dielectric-filled edge-slot (DFES) antennas which belong to a class of circumferential slot antennas that are suitable for conformal mounting on conducting bodies of revolution. The specific antenna considered consists of a disk of dielectric substrate mounted between the two halves of a conducting cylinder and is excited at its center by a coaxial stub. It can be tuned for a desired operating frequency with the help of a number of axially oriented passive metallic posts located inside the dielectric region. For analysis, the antenna is modeled as a symmetrically excited -type radial waveguide loaded with the metallic posts and terminated by an equivalent admittance appropriate for the radiating aperture. Circuit parameters for the metallic posts in the radial waveguide are obtained by detailed field analysis using mode matchng techniques. These are then used, along with the equivalent transmission line circuit for the antenna, to obtain the input reflection coefficient as a function of frequency for various DFES antennas. The results of computations based on the theory developed are compared with available measured values.