Active and Passive Millimeter Wave imaging systems employed for security screening at the airports and finding landmines

Electromagnetic waves in the millimeter-wave band  (with frequencies between 30 and 300 GHz, or wavelengths between 10 and 1.0 mm) have attractive characteristics. One of their features is the wider usable frequency band compared with waves in the microwave band or lower bands. Another feature of using the millimeter-wave band is the fact that it becomes possible to design smaller and lighter equipment that utilizes that band. So it is useful to adapt millimeter waves for short-range broadband communication systems, high resolution sensing systems and radio astronomy.