Focusing of translational variant bistatic forward-looking SAR with Chirp-Z transform

The forward-looking imaging problem of synthetic aperture radar can be resolved by adopting the bistatic configuration. This paper introduces a translational variant bistatic forward-looking SAR (BFSAR) configuration with a moving transmitter and a forward-looking receiver. Focusing bistatic SAR data in frequency domain requires two-dimensional (2D) point target spectrum. However, the existence of the double square root (DSR) term in the bistatic range makes it difficult to get the exact solution for the 2D spectrum. Approximate solutions such as the method of series reversion (MSR) have been derived to get the 2D spectrum, but the accumulative error to DSR of MSR is not the smallest one. To improve the accuracy of the 2D spectrum, the method of Legendre polynomial expansion is proposed to obtain the least square approximation of the bistatic range and get a more accurate 2D spectrum. Then, the Chirp-Z transform is chosen to focus the translational variant BFSAR data based on this spectrum, and the imaging quality is compared with the traditional MSR spectrum; the simulation results verify the 2D imaging ability of the proposed method.