Analysis of phase modulation caused by target motion in SAR images

Abstract

Moving targets in SAR images cause phase modulation of the phase history corresponding to the target. Depending on the motion, such modulations cause SAR image distortions. A simple case is an oscillating point reflector which causes sinusoidal phase modulation. Such signals can be analyzed with time-frequency techniques. The techniques reveal the time dependent Doppler frequency corresponding to the target. Using both direct instantaneous frequency estimates and quadratic time-frequency methods, we may estimate the oscillation parameters. Examples are given from simulated and real data. In the case of real data, the results agree well with ground truth. The direct estimates are best for high signal-to-noise ratios and single reflectors. In other cases the more sophisticated and computationally intensive quadratic methods perform best.