Implementation and testing of a switching circulator for twin-pair star radio architectures

Abstract

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.