On slot antennas input impedance and efficiency

Abstract

The formulas presented in the paper allow fast and reasonably accurate estimation of printed slot antennas efficiency and driving point impedance. They can be used at the initial stage of the antenna design to choose optimal values for the substrate parameters and slot length. The internal feature of printed slot antennas that is to radiate the most of the input power into a media with a higher dielectric constant, results in their low efficiency, since the dielectric constant of the substrate is usually much higher then that of the atmosphere. The same feature, however, makes the printed slot antennas a very attractive feeder for the DRA, since the dielectric permittivity of the DRA can be chosen much higher then that of the substrate. The generalization of the presented formulas for some practical antenna structures of interest, such as slot antenna driving a hemispherical dielectric resonator or slot antenna on a finite width dielectric substrate is straightforward. Some preliminarily results on these structures are to be reported during the presentation. The accuracy of the method can be increased since the current distribution M (y) = (L/2 − |y|) × cos[k × (L/2 − |y|)] also allows the closed form expression for the antenna impedance. This function together with (1) can be used for very efficient implementation of the MoM for the printed antenna impedance and efficiency calculations.