Microstrip active antennas and arrays

A description is presented of active antennas and arrays fabricated using microstrip patch antennas and Gunn diodes. Injection-locking experiments were carried out on these X-band antennas to achieve frequency coherency and to calculate the circuit Q-factor. An electronic tuning range of over 9% has been achieved for the single active patch element. A two-element active array was also developed. The output power levels from the two elements were combined in free space, resulting in higher power in the main beam. The tuning range was much narrower and the antenna pattern broke from a single beam into two separate beams as the DC bias voltage was varied. The breakup limits the practical tuning range.<>