Chapter 21: Synthetic Aperture Radar
L. J. Cutrona
Sarcutron, Inc.
21.1 BASIC PRINCIPLES AND EARLY HISTORY
For airborne ground-mapping radar there has been continuous pressure and desire to achieve finer resolution. Initially, this finer resolution was achieved by the application of "brute-force" techniques. Conventional radar systems of this type were designed to achieve range resolution by the radiation of a short pulse and azimuth resolution by the radiation of a narrow beam.
The range resolution problem and some of the pulse compression techniques are discussed in Chap. 10. There it is shown that techniques are available for achieving a resolution significantly finer than that corresponding to the pulse width, provided a signal of sufficient bandwidth is transmitted. Since pulse compression is adequately treated in that chapter, the present chapter will discuss pulse compression techniques only for cases in which the pulse compression technique is intimately involved with synthetic aperture techniques. This is particularly true for configurations that perform both pulse compression and azimuth compression simultaneously rather than with techniques that perform range compression and azimuth compression sequentially.
The basic technology discussed in this chapter is the exploitation of synthetic aperture techniques for improving the azimuth resolution of a mapping radar to a value significantly finer than that achievable by making use of the radiated beamwidth.
Synthetic aperture radar (SAR) is based on the generation of an effective long antenna by signal-processing means rather than by the actual use of a long physical antenna. In fact, only a single, relatively small, physical antenna is used in...