Technology now allows the use of microwave and millimeter wave sensors for the detection of concealed objects, typically weapons and explosive devices, on the human body. This book discusses these developments and includes examples of actual devices built and tested by the authors. Topics include active millimeter wave sensor using the direct detection approach and the heterodyne approach, active microwave sensor for CNR-based object detection, passive millimeter wave sensors, and the role of shielding effects in operating non-imaging MM-wave sensors-- Provided by publisher.