High-Squint High-Frame-Rate Uniform-Resolution Video SAR: Parameter Design and Fast Imaging

Traditional high-squint video synthetic aperture radar (ViSAR) with constant radar parameters suffers from the problem of nonuniform 2-D resolution, representing in two aspects: the first refers to the nonorthogonal -3-dB resolution ellipse of the 2-D point spread function; the second refers to the spatially varying 2-D resolution among different frames due to inconsistent squint angles. This problem can be solved by continuously adjusting the radar parameters, such as carrier frequency and chirp rate, according to instant geometry to achieve a trapezoidal-format wavenumber spectrum. However, such a strategy results in the problem of low azimuth bandwidth utilization ratio and, hence, of low imaging frame rate due to a waste of accumulation time. Thus, this article proposes a new annular-format parameter-adjusting method to achieve the highest available azimuth bandwidth utilization ratio and, hence, the highest available frame rate of video imaging. In addition, a new frame-interaction polar format algorithm is proposed for fast imaging in the case of the new annular-format wavenumber spectrum. The mechanism of speeding up the processing is to perform the interpolations within a group of frames, rather than a traditional single frame, to avoid repeatedly interpolating overlapped data among adjacent frames. The presented approach is validated via computer simulations.