New imaging algorithm for range resolution improvement in passive Global Navigation Satellite System-based synthetic aperture radar

This study proposes a new imaging algorithm for passive Global Navigation Satellite System-based synthetic aperture radar to improve range resolution. In the proposed algorithm, to reduce range compressed pulse mainlobe ambiguity caused by pseudo-random noise code frequency, second-order differentiation is carried out to the square of range compressed signal with respect to range delay lag. Because the carrier phase value is distorted in the squaring procedure, thereafter, a recovery processing is applied to each identified range compressed pulse for preserving the carrier phase for azimuth compression. Both simulation and experimental results indicate that compared to the conventional imaging algorithm, a significant enhancement in range resolution can be achieved by the proposed imaging algorithm. Meanwhile, from the results, the proposed algorithm will not degrade the compressed scene illumination level.