A compact retrodirective wire antenna with two isolated ports

Retrodirective arrays have the unique characteristic that they reradiate an incoming signal back toward the source without a priori knowledge of the arrival direction or reliance on sophisticated digital-signal-processing algorithms. The unique feature makes the retrodirective array an attractive candidate for advanced digital mobile communication, where high link gain and self-beam-tracking are desired. In conventional retrodirective arrays, the space between elements is usually greater than 0.5/spl lambda/, making it difficult to meet the requirement of some mobile stations, such as handheld systems, whose inter-element spacing is limited. We use a compact wire antenna with two highly isolated ports as a retrodirective antenna by introducing phase conjugation with heterodyne mixing to each port. The retrodirective ability of the antenna is studied using EM simulation. Simulation results show that the antenna can track an incident wave from 0/spl deg/ to 360/spl deg/ with its main beam. Compared with the standard monopole, the antenna gain in the incident wave direction is improved by 4-8 dB.