Millimeter-Wave Imaging of Person-Borne Improvised Explosive Devices.

摘要

With the recent rise in casualties and threat of casulties resulting from person-borne improvised explosive devices (PBIEDs) there is an urgent need for building imaging systems to perform standoff and portal detection of such threats. An optimum system that fulfills the requirements of PBIED detection must be low cost and have a high probability of detection with low probability of false alarm. A standoff detection system must also be portable while a portal imaging system can be stationary. Currently there are a variety of modalities being researched to perform standoff detection of PBIED's including: backscatter X-ray imaging, infrared imaging, optical detection, terahertz imaging, video analytics, and millimeter-wave (MMW) imaging. MMW imaging is a perferable modality for full body imaging of PBIEDs for many reasons. MMWs can propagate through the atmosphere and clothing with very little attenuation, while at the same time do not cause damage to human skin tissue. MMWs are small enough to build physical and synthetic aperture systems small enough to have a realistic physical system footprint while also providing excellent cross-range resolution. Present technology is available to generate very wideband coherent MMWsignals, which can be used to generate very high resolution images of targets at both standoff (> 15 meters) and portal ( 1 meter) distances.;Due to the large expense of building MMW imaging systems there is a large need to accurately model such systems numerically. With a forward model complex geometries, novel sensor and system configurations can be tested with minimal cost and overhead. Models also allow researchers to carry out extremely precise and repeatable analyses that have the ability to give extraordinary insight to scattering processes. The finite difference method in the frequency domain (FDFD) is a forward model which yields itself as an excellent method to analyze the scattering at MMW frequencies. However, due to the matrix inversion method of solving, it is not a realistic method for simulating 3D body geometries.;In this thesis two major aspects associated with MMW imaging are discussed: simulating the scattering of MMWs with a forward model and reconstructing MMW field data from both simulated and experimental continuous wave (CW) radar systems (both portal and standoff scenarios).