An airborne highly squinted SAR imaging algorithm for space variance of squint angle

In the case of low-altitude airborne platforms with highly squinted synthetic aperture radar (SAR) imaging modes, the echo signal not only suffers from severe range-azimuth coupling, but more importantly, the squint angle is range-dependent. In order to solve this problem, this paper proposes an improved highly squinted SAR imaging algorithm based on range modified chirp scaling (MCS). The method first revises the geometric model to incorporate the squint angle variation across range cell. An improved range-domain CS function is then introduced to equalize the range-variant range cell migration (RCM) introduced jointly by the squint angle and the slant range. In the azimuth dimension, the azimuth frequency modulation (FM) rate is reformulated to reflect the same range-dependent squint angle, enabling construction of a new azimuth-matched filter that guarantees accurate azimuth compression. The combined two-dimensional processing yields a fully focused image. Simulation results confirm the algorithm’s validity and superior focusing performance under highly squinted, low-altitude conditions.