This Small Business Innovation Research Phase I proposal will demonstrate the feasibility of an ultra-low power radio frequency (RF) field sensor based on novel magnetic tunnel junction (MTJ) technology. The sensor will be comprised of an MTJ sensing element that, when placed in a component or system, will monitor for perturbations in the ambient RF field profile during various stages of operation. The configured sensor is environmentally robust and is sensitive to the field direction. This project will also develop a low power complementary metal oxide semiconductor (CMOS) concept to provide digital readout of the measured signal with post processing to look for perturbations to be done off-chip. The results of this effort will provide a concise path forward for the fabrication of prototype sensors in the Phase II program. Approved for Public Release 14-MDA-8047 (14 Nov 14)