Today, the development and use of microwave (3-30 GHz) and millimeter wave (30-300 GHz) band is being actively promoted. Microwave has been used extensively since the Second World War when the sources were based on vacuum devices. Microwaves are presently playing a vital role in RADAR, land and satellite based communication and also have wide civilian and defence applications. Two typical areas of application of millimeter-wave are information communication and remote sensing.
