Circular log-periodic direction-finder array

An antenna array having a central feed region and comprising a plurality of antenna subarrays having longitudinal axes thereof extending outward in different directions from the central feed region, each antenna subarray comprising:

• A. a ground-plane conductor having a substantially log-periodic arrangement of slots therein arrayed along the axis of that subarray and thereby defining low-frequency and high-frequency ends of the subarray, the high-frequency end being disposed near the central feed region, the low-frequency end being remote from the central feed region;
• B. a traveling-wave element extending along the subarray on one side of the ground-plane conductor between its high-frequency and low-frequency ends for cooperation with the ground-plane conductor to support therewith propagation of electromagnetic waves in a forward direction along the subarray, the end of the traveling-wave element at the high-frequency end of the subarray being adapted for coupling to a transmitter or receiver;
• and
• C. cavity-defining conductor means associated with each slot and defining a cavity disposed on the other side of the ground-plane conductor and opening at its associated slot, the depths of the cavities being such as to give the subarray a sensitivity to electromagnetic radiation received from the direction of the high-frequency end of the subarray that is lower than its sensitivity to radiation received from the direction of the low-frequency end of the subarray.