Photonics for simultaneous transmit and receive

Many systems would benefit from the ability to transmit and receive signals within the same frequency band from the same aperture and at the same time. A key technology breakthrough enabling this simultaneous transmit and receive (STAR) capability is the recent development of a transmit-isolating photonic receive (TIPRx) link that functions both as the first-stage LNA in the receive front end and as an RF circulator, enabling a bidirectional interface to an antenna while isolating the receive chain from the transmit signal by 40 dB or more over bandwidths spanning multiple decades. While broadband LNAs have been commercially available for many years, to the authors' knowledge the TIPRx is the only technology that can presently offer such high T/R isolation over such wide bandwidths while simultaneously ensuring low noise figure for the receive chain. This paper describes the TIPRx and some additional issues involved in implementing a single-aperture STAR system.