Detecting Electronic Initiators Using Electromagnetic Emissions

Case Description

Explosive devices typically contain at least three components: propellant, a payload, and an initiator. Each of these components provides a different opportunity to detect the device. Although the first two components are the most specific indication that explosives are present, another way to detect potential explosive devices is to detect the initiator. Explosive devices are commonly initiated using proximity sensors or remote triggers (Wilson, 2006; Griffith, 2007). Such initiators generate electrical signals which can radiate into the environment as electromagnetic emissions. By detecting potential initiators, it is possible to indirectly infer the presence of an explosive device.

The purpose of this work is to improve techniques for detecting specific types of electronic initiators. Radio receivers of every variety, such as doorbells, automobile key fobs, two-way radios, and cellular telephones, have been used by insurgents as remote initiators (Smith & Coderre, 2008). For example, the devices used in the 2013 Boston Marathon bombings contained parts from a remote-control car (Chuchmach, 2013). These radio receivers unintentionally radiate low-power radio signals during normal operation. By using a weak stimulation signal, it is possible to inject a known signal into these unintended emissions. This technique has proven to be effective at detecting super-regenerative (Seguin, 2009a) and superheterodyne (Stagner, Conrad, Osterwise, Beetner, & Grant, 2011) radio receivers. The following sections detail the research and development process of an improved radio-receiver detector.