A MM-Wave SAR-Design for Helicopter Application (ROSAR)

First developments on Synthetic Aperture Radar (SAR) system based on use of Doppler information to obtain high resolution in azimuth direction were originated in 1951 by Carl Wiley. For short range battlefield reconnaissance applications mm wave imaging sensors find increasing interest. Preliminary studies show that high resolution SAR sensors in the usual sidelooking configuration may be developed at 35 GHz and 94 GHz in the near future. Imaging systems, based on Synthetic Aperture Radar concept for airborne and spaceborne applications are designed for a straight linear flight path. In this paper an unusual concept of a Synthetic Aperture Radar with rotating antennas for high resolution imaging is discussed, based on the rotational rather than the translational movement of the antenna phase center. The ROSAR concept has potential benefits for civil and military helicopter borne imaging applications, if the antennas are mounted at the tips of the rotor blades, for example. The concept has two main potential benefits, that are, the imaging field of view is 360° and there is no need for a forward velocitiy, because the rotor induced Doppler spectrum is used for imaging only. For the special helicopter requirements the mm wave frequencies (35 GHz/94 GHz) looks feasible. As opposed to SAR systems, based on linear antenna movement, high resolution ROSAR imaging is based on synthetic apertures of circular shape and the ROSAR processing differs considerably from the regular SAR processing schemes.