Retro-directive Antenna Array with Phase Conjugation Circuit Using Subharmonically Injection-locked Self-oscillting Mixers

In this paper, a novel approach for phase conjugation circuit and its application in retro-directive antenna are developed and tested. The phase4 conjugation is achieved by using balanced structure of subharmonically injection locked self-oscillating mixers (SILSOMs) with oscillating frequency at ω. An input signal at ω/2 is converted to its phase-conjugated signal using the nonlinear effect of SILSOM. No external source is needed for LO pumping, and the input and output signals are at the same frequency due to the locking phenomenon of oscillators. The phase conjugation circuit is then loaded with active antennas to become a retro-directive antenna array, and is demonstrated with measurement results.