Millimeter and Submillimeter Wave Applications

Many applications of millimeter and submillimeter wave systems have been suggested in the literature but, in general, they have not yet beea employed in practice to any significant degree. This report discusses the advantages and limitations of this frequency region and reviews the potential applications under the categories of radar, communications, radiometry and instrumentation. One of the problems of operating in this frequency range is that some of the advantages can also be considered as limitations. Even if transmitter powers and receiver sensitivities were the same as those obtained at microwaves, it would be unlikely that millimeter and submillimeter wave systems could compete with most of the major applications of microwaves. Successful applications of the shorter wavelengths will probably utilize characteristics that are distinct from those of microwaves. The special attributes of millimeter and submillimeter waves are narrow beamwidth with reasonably-sized apertures, wide bandwidth, and interactions with the constituents of the atmosphere and other gases. The more likely candidates for applications unique to this frequency range include remote sensing of the environment, interference-free communications and radar, low-angle radar tracking, high-resolution and imaging radar, extremely wideband communications, plasma diagnostics, and spectroscopy. If systems applications occur it seems more likely that they would be found initially at frequencies below 50 GHz rather than at the higher frequencies. At the present time, there does not seem to be imminent major systems applications of these wavelengths. The search for quick "riches" in practical millimeter wave systems applications probably should be minimized, and more emphasis should be placed on exploring the science and technology of this region for their own sake. ^-i" '■^^•»■fP^HW^^'i, m IIB