Research On Synchronization And Imaging Of Airborne Bistatc Synthetic Aperture Radar

Bistatic SAR, which separates transmitting and receiving stations, has become a hot topic in radar area. Its transmitter and receiver are equipped on different platforms, which are separate with long distance. It has a number of advantages such as anti-detecting, anti-disturbing and high viability and can observably increase the efficiency in the war. To address a series of key problems for the bistatic SAR, the following work has been presented1) The airborne bistatic SAR operation modes and corresponding characteristics were studied to model radar echo, under certain conditions of different beam directions, space geometries, and flying models. Specifically, the echo for the squint range operation modes was modeled. Moreover, two-dimensional spectrum of the echo was accurately obtained by using the Loffeld model.2) Aiming at airborne bistatic SAR space resolution, mathematical expressions, directions and space-variant properties for space resolution of the airborne bistatic SAR were derived based on the Doppler characteristics of the transmitting and receiving stations. The main decisive factors and space variant characteristics of space resolution were expressed.3) Aiming at time, frequency and phase synchronization technology of airborne bistatic SAR, the impact of synchronization error on imaging was analyzed and, under the condition of a certain resolution, the error bounds were quantitatively derived. A pulse per second phase tracking smoothing technology using Global Position System (GPS) was proposed to deal with synchronization PLL missing lock caused by phase agile, and realize high stability and high accuracy synchronization.4) Considering non-association of transmitting and receiving stations and non-coherence of signals under the condition of non-synchronization, a Constant False Alarm Rate (CFAR) sliding-window tracking technology was proposed to capture and track the bistatic SAR echo, and realize non-synchronized echo acquisition and storage. 5) Towards irregular motion of platforms and the problem that disturbances of the attitude affect imaging quality, a motion compensation algorithm based on the bistatic extended Chirp Scanling (CS) algorithm was proposed. This method solves the problem of image focus out by flats motion and attitude disturbance on bistatic SAR. An airborne bistatic SAR high precision navigation and attitude measurement project were designed, providing a technical method for the airborne bistatic SAR motion compensation technology based on hardware platform.6) An experimental project on the airborne bistatic SAR was proposed. The experiment using typical bistatic operation modes was successful to obtain bistatic images. The first vehicleborne and airborne bistatic SAR images in China were obtained. The synchronization technology, imaging method and motion compensation method were validated in this experiment.