Injection locking in active antenna

An oscillator type active antenna is designed using two-port microstrip antenna as feedback element for RF BJT amplifier. The injection locking of active antenna is demonstrated in time domain for first time. As per the reported literature active antenna circuit takes some time to lock at the frequency of injection signal. The locking time delay depends on injected power level and difference of active antenna free-running frequency and injected signal frequency. However it is observed experimentally for the first time that the dependency is weak, and only near the edge of the locking band does the locking delay rise sharply.