Subpulse Processing for Unambiguous Doppler Estimation in Pulse-Doppler Noise Radars

The Doppler dilemma, an inherent dichotomy between range and velocity estimation in pulse-Doppler radars, has been the subject of many works in literature. Classical approaches for solving its intrinsic ambiguities usually rely on the subdivision of the coherent processing interval into multiple bursts of different pulse repetition frequency (PRF). Besides some additional complexity related to the PRF selection and the extraction of the unambiguous measurements, these techniques reduce the coherent gain, introducing losses that, in some cases, can be in the order of several decibels. Within this context, this article presents a novel velocity estimation scheme, based on a subpulse processing architecture and random waveforms. It is shown that, with the proper selection of system parameters, the subpulse-to-subpulse phase shift can be evaluated and used to extend the unambiguous measurements as far as needed. The algorithm performance has been evaluated through statistical simulations, and its complexity addressed with a real-time implementation. The proposed architecture was also verified considering different noise waveforms, including sidelobe optimized ones. The results have shown that, besides extending the unambiguous measurements, and improving the Doppler tolerance, the subpulse processing has also increased the system robustness to the Doppler mismatch effects, reducing sidelobes, and thus, extending its applicability.