Concept and Experimental Verification of a New Electronic Tacan-Antenna

The existing mechanically rotating radio navigational TACAN-antennas will be replaced by electronic ones. The historical technical background and some related antenna basics are treated. Applying the extended phase mode theory for circular arrays a new concept is presented which uses sequential sets of conjugate phase modes yielding a drastic reduction of radiating elements (N = 16 compared to N = 32 or 36). Some hardware details are outlined by describing an experimental antenna. This antenna uses a special 6 × 16 BUTLER-matrix which excites phase modes of maximum order M = 5 whilst 3 digital phase shifters provide the specified pattern rotation. Theoretical and measured results are presented showing the general feasibility and the successful operation with typical airborne receivers.