Implementation and Testing of a Switching Circulator for Twin-Pair STAR Radio Architectures

Realization of simultaneous transmit and receive (STAR) wireless systems is desirable for spectral efficiency but challenging due to difficulties in isolating the receiver from the transmitter. A twin-pair STAR architecture based on two identical sequentially-switched delay line (SSDL) circulators is proposed for STAR. The twin-pair approach uses one circulator as a real-time model of the other circulator which is used for communication, thereby allowing cancellation of transmit signals from the receiver before reaching the first low-noise amplifier (LNA). A wideband SSDL circulator is designed and characterized to study its suitability in the proposed STAR architecture. The circulator has spur-free (over-multiplexed) operation up to 48 MHz and under-multiplexed operation up to 1.0 GHz with an insertion loss <; 10 dB and isolation >25 dB.