Research On Synchronization, Imaging And Interferometric Application Techniques For The Bsar Based On Spaceborne Illuminators

Bistatic synthetic aperture radar(BSAR) based on spaceborne illuminators is a kind of novel radar system, in which a launched satellite(such as SAR satellite, navigation satellite and communication satellite) serves as the transmitter of opportunity, while the receiver is mounted on another platform(such as aerostat, airplane, vehicle and fixed platform). It benefits from low-cost, high operational flexibility, and reduced vulnerability to counter-measurement, consequently, is a promising technique with great potential. This paper is referred to two particular subclasses with different system configurations-the navigation satellites-based BSAR and the SAR satellites-based BSAR. The navigation satellites-based BSAR utilizes the launched navigation satellites as the transmitter, while the receiver is mounted on the fixed surface-platform. The SAR satellites-based BSAR utilizes the launched SAR satellites as the transmitter, while the receiver is mounted on the aerostat. Combining the theoretical research and the engineering application, this dissertation focuses on the synchronization, imaging and interferometric application techniques for these two particular BSAR systems. Through the in-depth study of the common and the special issues on the above mentioned techniques, we have achieved some valuable research results.The main achievements and contributions of this dissertation are as follow:1. The system concept and peculiarity of the BSAR based on spaceborne illuminators are studied. Thus the theoretical basis for following studies is established. The main work includes:(1) The system concept of the navigation satellites-based BSAR is presented, and then the system peculiarities, including geometric configuration, signal-to-noise ratio(SNR), resolution and time/space coverage ability, are deeply analyzed.(2) Correspondingly, the system concept of the SAR satellites-based BSAR is presented, and then these system peculiarities are deeply analyzed as well.(3) The sameness and the difference between these two BSAR systems are compared and analyzed, mainly focusing on the SNR and Doppler characteristics.2. The synchronization and imaging algorithm for the navigation satellites-based BSAR is studied. The main work includes:(1) The signal model of the system echo is derived, and the impacts of the navigation signal format and phase synchronization errors are analyzed.(2) The pre-processing method of synchronization is presented. The effective detection of the navigation message and the high-precision estimation of the Doppler frequency are achieved. Thus the impact of the navigation signal format is eliminated.(3) Taking advantage of the characteristic of the extreme asymmetrical geometry, we theoretically prove that the range measurement errors for the direct-path signal and the echo signal can be neutralized.(4) An integrative synchronization and imaging algorithm is proposed based on the neutralization principle of measurement errors and the time-domian imaging algorithm. The experimental data is used to verify the proposed algorithm.3. The synchronization and imaging algorithm for the SAR satellites-based BSAR is studied. The main work includes:(1) A space synchronization approach based on the operation model with the wide-beam and the continuous data acquisition is adopted. As a consequence, the data acquisition of the experiment can be confirmed and the coverage of a wide imaged scene can be achieved.(2) The time and frequency synchronization error model is established, and the influence of the synchronization errors on the imaging is analyzed.(3) An integrated synchronization and imaging algorithm is proposed. For the proposed algorithm, firstly, the synchronization is achieved by using the extracted time delay and the peak phase to compensate the corresponding terms in the echo signal. Then the two-dimensional spectrum of the synchronized echo is derived based on the Taylor series expansion and the linear approximation. At last, considering the peculiarity of the derived spectrum, we propose a frequency-domain imaging algorithm using two-dimensional inverse scaled Fourier transform(2-D ISFT). This algorithm can be able to achieve the well focused imaging for the wide scene.4. The interferometric application techniques for the BSAR based on spaceborne illuminators are studied. The main work includes:(1) The complex image model of the BSAR based on spaceborne illuminators is derived, and the coherence is analyzed for the interferometric application. Hence, the interferometric theory model for the BSAR based on spaceborne illuminators is built.(2) The technique of coherent change detection using the navigation satellites-based BSAR is investigated. For this application, the technical principle and the data processing approach are discussed, and then the performance is analyzed through studing its coherence.(3) The technique of interferometric hight measurement using the SAR satellites-based BSAR is investigated. The principle of this technique is presented. Then the interferometric features are analyzed taking into account the ‘three-dimentional hight measurement’ peculiarity. Through the in-depth study of the coherence characteristic, we make an accurate evaluation of the performance of this application technique.An abundance of simulated and experimental data is used to carry out the validation in this dissertation. Consequently, the achieved research results are proved to be of good application values.