Passive radiometric imaging systems in millimeter wavelength range

The sub-terahertz passive radiometric imaging systems based on the single channel design are developed for disclosure of dangerous objects concealed under persons' clothing in short distances and for passive visualization of remote targets. Antenna systems, such as based on aspheric lens and on parabolic reflector, were adopted and refined for passive imaging application. Low-noise, compact receiver (noise factor 4.5dB for 90–100GHz) involving four stages was developed. The radiometric imaging peculiarities of the different reflecting and absorbing targets were investigated against the brightness temperature of sky. The system was demonstrated to successfully detect and recognize the metallic weapon hidden under outer clothing in the distance about 10 m. The scanning process (80×80 pixels in an area about 32×32 cm) approximately takes 40 seconds.