An introduction to synthetic-aperture radar

One way of achieving fine-resolution terrain imagery using airborne, side-looking radar is to boost frequency; another is to decrease along-track tracking. Neither is attractive. But they would have had to do were it not for coherent wave radar-upon which synthetic-aperture radar is premised. Using coherent radar, resolution can depend, not on the width of the beam, but on Doppler frequency shift. The azimuthal resolution of side-looking radar can therefore be of the same order of magnitude as that for range resolution. The key to converting the theoretical groundwork into a ``full-bodied'' system is an appropriate data-processing scheme. And the simplest scheme for working, processing, and deciphering the data is optical.