Fitch J.P. Synthetic Aperture Radar

Springer, 1988. — 175 p.Radar, like most well developed areas, has its own vocabulary. Words like Doppler frequency, pulse compression, mismatched filter, carrier frequency, in-phase, and quadrature have specific meaning to the radar engineer. In fact, the word radar is actually an acronym for RAdio Detection And Ranging. Even though these words are well defined, they can act as road blocks which keep people without a radar background from utilizing the large amount of data, literature, and expertise within the radar community. This is unfortunate because the use of digital radar processing techniques has made possible the analysis of radar signals on many general purpose digital computers. Of special interest are the surface mapping radars, such as the Seasat and the shuttle imaging radars, which utilize a technique known as synthetic aperture radar (SAR) to create high resolution images (pictures). This data appeals to cartographers, agronomists, oceanographers, and others who want to perform image enhancement, parameter estimation, pattern recognition, and other information extraction techniques on the radar imagery.
The first chapter presents the basics of radar processing: techniques for calculating range (distance) by measuring round trip propagation times for radar pulses. This is the same technique that sightseers use when calculating the width of a canyon by timing the round trip delay using echoes. In fact, the corresponding approach in radar is usually called the pulse echo technique. The second chapter contains an explanation of how to combine one dimensional radar returns into two dimensional images. A specific technique for creating radar imagery which is known as Synthetic Aperture Radar (SAR) is presented. Chapter 3 presents an optical interpretation and implementation of SAR. There are many similarities between SAR and other image reconstruction algorithms; a summary of tomography and ultrasound techniques is included as Chapter 4. Although the full details of these techniques are not explained, an intuitive understanding of the physical properties of these systems is possible from having studied the radar imaging problem.
Any type of digital radar processing will involve many techniques used in the signal processing community. Therefore a summary of the basic theorems of digital signal processing is given in Appendix A. The purpose of including this material is to introduce a consistent notation and to explain some of the simple tools used when processing radar data. Readers unfamiliar with the concepts of linear systems, circular convolution, and discrete Fourier transforms should skim this Appendix initially and refer to it as necessary. Matched filters are important in both pulse echo radar and SAR imaging: Appendices Band C discuss the statistical properties and digital implementation strategies for matched filters.
The approach in these notes is to present simple cases first, followed by the generalization. The objective is to get your feet wet, not to drown in vocabulary, mathematics, or notation. Usually an understanding of the geometry and physics of the problem will be more important than the mathematical details required to present the material. Standard techniques are derived or justified depending on which approach offers the most insight into the processing. Of course there are many radar related techniques which were simplified for presentation or omitted entirely-existing books and articles containing this information should be within the grasp of readers who studiously complete these notes.Radar Processing
Radar Imaging
Optical Processing Of SAR Data
Related Algorithms: An Overview
A: Signal Processing Tools
B: Matched Filter Derivation
C: Matched Filter Implementation
D: Solutions to Exercises