Groundplane mounted log-periodic antenna

Abstract

A log-periodic antenna comprises two arrays of dimensionally tapered radiating elements disposed in the E-plane and each fed by a balanced line consisting of the inner conductors of two coaxial cables. In one embodiment the elements of each array are dipoles and in an other embodiment are formed of continuous conductive strips in zig-zag patterns on non-conductive support members. Each array preferably has two sets of elements disposed in planes, respectively, which converge toward the smaller end of the array with vertically aligned radiating elements of each set projecting in opposite directions from the array axis. Periodic gain dropout anomalies across the antenna operating band are at least substantially reduced by use of shielded feed lines. In another embodiment which has particular advantage at HF frequencies, a single array is operated over a ground plane which provides a mirror image thereof. In yet another embodiment which has advantage in direction finding, the sets of elements of each array are located on associated opposite sides of a right rectangular pyramid. A pair of these pyramidal arrays, with some of the element sets being coplanar, are employed for direction finding.