How do I design a millimeter wave body scanner for security screening applications?

Designing a millimeter wave body scanner for security screening applications creates an imaging system that detects concealed objects (weapons, explosives, contraband) under clothing by illuminating the person with low-power millimeter wave signals (typically 20-100 GHz) and forming an image from the reflected or transmitted radiation. The mmW frequencies are used because: mmW signals pass through clothing (cotton, wool, synthetic fabrics are nearly transparent at 30-90 GHz with less than 1 dB attenuation), but reflect from metals, plastics, ceramics, and the human body (the skin has high reflectivity at mmW due to its water content). Concealed objects create contrast against the skin, appearing as: bright spots (metallic objects) or dark shadows (dielectric objects like plastic explosives). Scanner types: active imaging (the scanner transmits mmW signals and receives the reflections to form a coherent image; frequency: typically 24-30 GHz or 70-80 GHz; the scanner uses a rotating array or a switched array to synthesize a large aperture; image resolution: approximately 1-3 cm at 1-2 m distance), and passive imaging (the scanner detects naturally emitted mmW thermal radiation from the body and concealed objects; no transmitter needed; the temperature contrast between the body (emissivity approximately 0.65 at 90 GHz) and concealed objects (different emissivity) creates the image; image quality: inferior to active imaging (lower SNR), but: no RF exposure to the subject).