Millimetrewave systems-past, present and future

Millimetrewave and submillimetrewave systems are reviewed. The three characteristics which make millimetrewaves useful for radar, communications and radiometric systems are described. These are the narrow beamwidths and high resolution obtainable from antennas, the propagation characteristics of the atmosphere, and the wide frequency bandwidth available. The past is reviewed by describing the early work based on the discoveries of Hertz, and by describing the millimetrewave low-loss waveguide project of the middle part of this century. The present state of millimetrewave components and devices is reviewed. Millimetrewave radar is the most developed area, with systems for precision guidance, tracking and target signature. Millimetrewave communications is starting to be used for short distance terrestrial distribution and for satellite communications, where the large bandwidths are attractive. Millimetrewave radio astronomy is pioneering the technologies in the submillimetrewaveband. Progress in using millimetrewaves for meteorology, remote sensing and detection of targets is also rapid. The review concludes that the future of millimetrewave systems is bright.