Variant Bistatic Sar Imaging Algorithm

Bistatic SAR proposes many advantages, for example, improving object scattering factor. It can be widely applied to terrain mapping, detecting moving targets and evaluating the war results. In nowadays military field, the demands for flexibility of radar system is higher and higher. Based on this background, we develop several new radar work modes: translate variant mode and spaceborne/airborne hybrid mode. These systems have obvious spatial variant characteristics, and the imaging algorithms under them become the research hotspots.From the public literatures, the imaging algorithm research under spatial variant Bi-SAR is still in the early stage. Focusing on the imaging theories, the main works of this thesis are shown as below:Airborne translate variant Bi-SAR system is studied. Project the system echo in vector to the wave number domain first; work over several important imaing characteristics under the translate variant mode: baseline distance, range history, etc.; the spatial resolutions is derived through the 2-D ambiguity function, and analyze the changing trend of them under different scatterer positions and bistatic angles. The simulation experiment results are given in the article.Spaceborne/airborne hybrid Bi-SAR system is studied. Unify the coordinate system of satellite, aircraft, the earth and scatterer through analyzing the satellite geometry; analyze the synthesize aperture time, Doppler properties and spatial resolution changing trend with satellite geometry and squint angle of aircraft in detail; conclude the results: SA-BiSAR is approximate to a squint mono-static SAR, because all the characteristics are determined by satellite. The simulation experiments are presented in this article, and the results testify the validity.In this article, we improve the classical RD algorithm, and made it fit to the SA Bi-SAR imaging: revise the range migration with range migration phase factor while range compensation. The simulation experiments testify the validity in the small slant angle case. While, the approximate range history maybe not clear, so the results are unideal under big slant angle and the scatterers away from the reference poin. We also proposed an translate variant Bi-SAR imaging polar format algorithm based on Chirp-Z transform. We expand the mono-static PFA: compensate the range migration with a real-time reference slant range to finish the coarse focus; derive the relationship beetween equivalent azimuth angle, squint angle and the echo, and finish the fine focus combine with chirp-Z transform, which escape the 2-D interpolation and save the computation cost. The simulation experiments are presented in this article, and the results testify the validity, even imaging the plane target under the airborne case.