1. Millimeter-wave applications

The millimeter-wave spectrum, which extends from 30 to 300 GHz, has long been exploited for applications limited to scientific research, radio astronomy and military communications between satellites, for example. More recently, the market for satellite-to-earth communications has expanded to include broadband Internet access, wireless data transfer in the home, automotive radar for speed control or accident avoidance, and point-to-point or point-to-multipoint wireless telecommunication systems, approaching the performance of fiber optics but at a lower installation cost. In addition, these high frequencies are also used in the design of imaging systems to enhance security, notably at airports by detecting dangerous objects.

These millimeter-band systems are developing because of the scarcity of free bands in the centimeter-wave spectrum, but also because they enable...