Wide Swath Imaging And Moving Target Detection For Frequency-Modulated Continuous-Wave Synthetic Aperture Radar

Synthetic aperture radar(SAR),which is as an important high resolution imaging system,should be miniaturized,to be used in the novel small sensing platforms,such as unmanned arerial vehicles,near-space vehicles and micro satellites.As a compact and cheap radar system,frequency-modulated continuous wave(FMCW)radar is the most popular system to be exploited for high resolution imaging application.The novel combination of FMCW technology and SAR techniques leads to the development of a small,lightweight,power-consuming,and cost-effective high-resolution imaging sensor with low probability of intercept.FMCW SAR is now developing rapidly with a tendency to be going with more channels and more functions.Based on this,I mainly study the high-resolution wide-swath imaging technology and the ground moving target detection technology for FMCW SAR.In detail the contents include the imaging using single-channel,the azimuth reconstruction for multi-channel,moving targets signal model,moving targets focusing,waveform design,and multi-channel system design for FMCW SAR.I study different imaging methods for FMCW SAR including range Doppler algorithm,back projection algorithm,frequency scaling algorithm and wavenumber domain method.After a general modeling of the beat signal for FMCW SAR,both the relationships and differences between different imaging algorithms in Doppler frequency Domain are researched.Then I improve the radio residual phase compensation method and the frequency scaling algorithm by considering the effect of the Doppler shift in one sweeping interval on the residual video phase.I also improve the wavenumber algorithm by reducing the interpolation data size with a modified Stolt mapping.To widen the imaging swath of FMCW SAR with high azimuth resolution,the multi-channel azimuth reconstruction methods are studied in this dissertation.A novel reconstruction method based on Vandermonder matrix is proposed.At first,the multichannel signal model is built by using a Vandermonder matrix in the system function matrix.The SNR scaling factor is also expressed by using the Vandermonder matrix.Altimately,I improve the conventional matrix inversion method by using the derived SNR scaling factor.The ill-condition problem where two or more channels are coherent or nearly coherent is overcomed.Altimately,a two-dimensional reconstruction process for FMCW SAR is illustrated.To detect the ground moving taegets for FMCW SAR optimally within a long coherent interval,the relative motion concept is applied to the sigmal model of FMCW SAR,and a novel concept called equivalent squint angle is proposed in this dissertation.The moving targets are newly described for FMCW SAR by using the parameters such as relative factor,equivalent squint angle and equivalent aspect angle.An optimal moving target detection method by searching the relative factor and the ambiguity number is proposed.The targets no matter moving slowly or fast could be detected and imaged with high resolutions both in azimuth and range direction.The motion parameters could be also estimated when the targets are detected.Furthermore,the method is suited for the detection of multiple targets or extended targets.All the moving targets with the same motion parameters will be focused when the relative factor is matched.At the end of my dissertation,a multi-input multi-output FMCW SAR system and its design are described.Addationally,the primary experimental results are also introduced.The amplitude and phase errors between different receive channels,and the range resolution requirement meet the design requirements.In this dissertation,all the improved imaging methods,azimuth reconstruction methods and the moving target detection methods are validated with sufficient simulation experiments by changing the velocity of the platform,the SNR,or the velocity of the moving targets.The studied and validated key techniques would promote the miniaturization development of the FMCW SAR.