A novel synthetic bandwidth method based on BP imaging for stepped-frequency SAR

ABSTRACT A novel imaging first and synthesizing later (IFSL) synthetic bandwidth method for stepped-frequency synthetic aperture radar is proposed in this article to compensate the space-variant range errors between the pulses in a cluster. The sub-band images are separately obtained through the time-domain back projection (BP) imaging algorithm. The space-variant range errors are corrected through concise multiplication and the continuity of spatial spectrum phase at the edges of adjacent sub-bands is well maintained due to the accurate imaging ability of BP algorithm. The derivation of analytical BP imaging formula is very difficult because of the complicated integrand. This difficulty is overcome through some rational approximations. By using this new method, the space-variant range error compensation is greatly simplified and the synthesized image quality is considerably enhanced compared with the conventional IFSL methods in which frequency-domain imaging algorithms are used. The simulation results validate the advantages.

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