A Novel Method for RF Tomography and Acquiring Dielectric Signatures for Security Applications

Quickly imaging and discriminating materials is becoming increasingly important for security screening. Conventional techniques are effective, but their results can be difficult to interpret when screening for low-z energetic materials such as explosives. In this paper, we present a novel method to identify the distinct signatures that many dielectric materials - potentially including energetic materials - exhibit when excited under radio frequency wavelengths. This novel system combines the ability to penetrate objects with lower-frequency radio waves while achieving a resolution potential traditionally reserved for millimeter waves or X-rays. The system measures impedance changes along a transmission line, generating data on the composition and location of materials in an object under study. This data can be stitched together to form an image via a “transmission line tomography.” A prototype system detected a volume of water concealed within a block of paraffin wax - both low-z materials. The detection system requires no moving parts and can utilize low-cost electronics to move the signals to the analysis computer.