Doppler Signature Analysis of Over-The-Horizon Radar Signals with Target Altitude Perturbation

In this paper, we examine the Doppler signatures of local-multipath signals in over-the-horizon radar for a target that moves with a constant horizontal velocity but experiences altitude perturbation. In practice, the target altitude may deviate from its scheduled altitude due to, e.g., flight dynamics. After describing the Doppler signatures for a target that maintains a constant altitude without perturbation, we develop the mathematical framework for target Doppler signature analysis that includes target altitude perturbations. It is observed that altitude variations result in spreading of Doppler frequencies, and the bias is associated with the average target altitude. It is observed that, for mild target altitude perturbations, existing analysis methods remain effective for local-multipath Doppler frequency estimation. The Doppler frequency estimation capability and performance are verified using simulation results.