Optimization of photonic transmit/receive module performance

Previous publications have described techniques that various researchers at photonic systems, Inc. and elsewhere have used to optimize the performance of analog photonic links. The success of these efforts has made the incorporation of antenna-remoting photonic links into radars and RF communications systems attractive to the designers of such systems. In this paper we show that the simple addition of photonic links to carry signals to and from an RF transmit/receive (Tx/Rx) module, while straightforward, is often not the most beneficial approach because it unnecessarily subjects the inherently broadband photonic components to the same bandwidth limitations as the RF circuitry in the module. If one instead begins with the idea that the broadband photonics technology should be central to the design of the antenna Tx/Rx interface, a completely new architecture emerges - one that not only has greater capabilities than the conventional RF interface, but is simpler as well. As an example of a photonics-based antenna interface design that is simple and yields improved capabilities, we present a Tx-isolating photonic Rx (TIPRX) link that operates over many octaves or even decades of bandwidth while providing 40 dB or more of isolation between the transmit and receive signals. The potential system impact of the TIPRX is that an antenna can receive low-power signals while simultaneously transmitting much higher-power signals.