Target geo-location is an important task in over-the-horizon radar. A useful approach is based on the Doppler signatures of the micro-multipath signals which reveal target motion and enable target state estimation. Target Doppler signatures, however, are sensitive to irregular target motions, thereby complicating the Doppler signature analyses. In this paper, we consider the Doppler signatures of micro-multipath signals for a target that moves with a constant altitude but its azimuth velocity and altitude are perturbed. We analyze the effect of such velocity and altitude variations in the resulting Doppler signatures. The Doppler frequency difference is estimated using the self-stationarized signals.