An integrated active circulator antenna

An active circulator is integrated with a quarter-wave short-circuited microstrip patch antenna to produce a fully duplexed transceiver with transmit and receive operation at the same frequency and with the same polarization. The active circulator antenna is shown to have 14-dBi transmit gain and 7.4-dBi receive gain with a transmit-receive isolation of 26.9 dB at 3.745 GHz. This active antenna has potential uses in both short-range communication and radar systems.