Measuring propagating RF signals is useful for communications and for sensing of intended and unintended (adversarial) radio signals. The common high frequency receiver implementation of an antenna followed by local-oscillator driven down-conversion stage and RF-cabling can adversely impact SWAP and in some cases disrupt the very signal one wants to measure. Additionally, such systems need careful packaging to avoid generating or receiving electromagnetic interference. Optical-based RF sensors can be fully passive, primarily dielectric (almost no metal), and are entirely wired via low loss, low weight, and zero-interference fiber optical cable. No local-oscillator is needed at the remote antenna location even when transferring received carrier frequencies >100 GHz. This project will improve the sensitivity and utility of fiber-optic coupled electromagnetic receivers, allowing for instance information from many antennas to be combined and jointly analyzed for applications like angle-of-arrival measurements. The small size, weight, and power (SWAP) of the receivers allow placement in awkward locations and cost-effective, low-profile high-frequency antenna arrays. Improvements over state of the art come both from system design and advances at the component level, including high efficiency of RF-to-optical conversion, and by exploiting photonic integration. These advances will be modeled and evaluated during the project to predict the performance of example use-cases to show the feasibility and utility of the technology for both military and commercial applications.
