Synthetic Aperture Radar Signal Processing with MATLAB Algorithms

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CROSS-RANGE IMAGING

Introduction

This chapter provides a relatively modem view of cross-range imaging from the information obtained by a discrete or sampled aperture; this is also referred to as an array. The origin of this approach can be found in the wave equation inversion theory, which is also known as wavefront reconstruction or holography [born; gab; wol]. This theory is the principal foundation of many imaging systems in optics [goo; wol], geophysics [ber80; ber81; hag; loe; mil; pet; rob; sto], and diagnostic medicine [chr; mue). The basic principle behind wavefront reconstruction is the use of the Fourier decomposition of a Green’s function, which is also known as the spherical phase function and represents the impulse response of an imaging system [ber80; goo; mor; s94].

The foundation of most analog optical imaging systems, which utilize lenses for image formation, is based on approximations of the wavefront reconstruction, for example, the Fresnel or Fraunhofer approximation. The early SAR systems, which utilized some form of analog processing of the received signals, were also based on these approximations [broo; br67; br69; curt; cut; fit; kir75l; kir752; kov76; kov77; tom; wil].

The introduction of powerful computers and fast digital signal processing algorithms, for example, FFT, has provided a fresh way to approach array imaging problems [ber81; chr; loe; mue; s94]. A similar revolution has occurred in other information processing systems. For example, one can ...