I. Introduction
Advances in electronics and RF design have made radio receivers smaller, cheaper, and more common than ever before. These new devices enable a plethora of innovative applications, but they can also be used maliciously to initiate explosives. One way to indirectly locate potential explosive devices is to locate the radio receiver, thus mitigating this threat. Radio receivers use many different high-frequency signals that readily escape into the environment, resulting in unintended electromagnetic emissions. It is possible to detect radio receivers using these unintended electromagnetic emissions [1]–[4].