Synthetic High-Range-Resolution Radar Imaging And Motion Compensation

Exploitation of high-resolution radar techniques has always been the direction of radar research and development in both military and civil applications. The improvement of radar range-resolution not only facilitates detection of targets in high clutter, but also makes it possible to image and recognize targets. The synthetic high-range-resolution radar has drawn attentions due to its high-range-resolution, low complexity of the system, low cost and easy implementation. The work of this dissertation is focused on research of target imaging and motion compensation techniques for the synthetic high-range-resolution radar. The main content of the dissertation is summarized as follows. Chapter 1 introduces the research background and the motivation of this dissertation, and reviews the previous work, including related research history and current status. The work of Chapter 2 is focused on the stepped/hopped frequency pulses, which are two wide-band waveforms employed in the synthetic high-range-resolution radar. From the view of radar resolution, the ambiguity function expression for the two wide-band waveforms is given out. By means of the ambiguity functions, the range- and Doppler- resolution performance of the two wide-band waveforms is analyzed in detail. Chapter 3 investigates the problem of optimizing the frequency hopping codes of the hopped-frequency pulses. A genetic algorithm for optimizing the frequency hopping codes of the waveform is presented. The random range-Doppler sidelobe peaks are well- controlled so that the ideal 搕humbtack?ambiguity function behavior is closely approximated by the genetic algorithm. Two optimal codes with the code length being 64 and 128 are given respectively, which can be used as reference in the system design. In Chapter 4, the effect of target motion on synthetic range profiles produced by stepped-frequency radar is analyzed, and then an efficient method for optimal estimation of motion parameter of targets is presented based on the minimum burst error rule. Simulation results indicate that the method can accomplish accurate estimation of target motion parameter with good anti-noise performance and low computational cost. iv In Chapter 5, the hopped-frequency pulses waveform is adopted in inverse synthetic aperture radar (ISAR), and a novel method for motion compensation in ISAR imaging, named the minimum waveform entropy method of parameter estimation, is proposed. A measure function, called the waveform entropy-like function, is employed to measure the effects of target motion on both Doppler spectrums and slant range profiles. The method can achieve optimal estimation of motion parameters of a target based on the minimum waveform entropy rule. In addition, the method converts a two-dimensional search for velocity and acceleration of a target into two one-dimensional searches for velocity and acceleration respectively, which decreases computational cost greatly, and realizes real- time processing conveniently. Simulation results indicate that the method can accomplish accurate estimation of motion parameters of a target with a good anti-noise performance, thus making it possible to image a target in clutter background. In Chapter 6, a novel algorithm for range-Doppler imaging of rotating targets is proposed with adoption of the multiple bursts of hopped-frequency pulses as a radar wide- band waveform. Compared with the stepped-frequency radar Fourier transform (FT) imaging algoritlun, the al...