Micro-motion frequency estimation of radar targets with complicated translations

Micro-Doppler (m-D) signatures induced by micro-motion dynamics, which are of great importance for target classification, have received increasing attention among the radar community. However, most of the existing m-D signature-extraction methods are based on the assumption that translations of radar targets have been completely compensated by other methods or they merely involve scenarios when radar targets undergo low order polynomial translations. These methods may become invalid for maneuvering targets with complicated translations. In this work, radar targets with micro-motion and complicated translations are considered. Inspired by the differential element method and the shift invariant difference operation, a micro-motion frequency estimation method based on piecewise translation compensation (PTC) and time-frequency squared difference sequences (TFSDS) is proposed. The PTC can compensate the translations of radar targets at the largest extent. After compensation, the TFSDS-based frequency estimator gives an estimation of micro-motion frequency; this estimator can remove the effect of residual translation and avoid the separation of the multicomponent radar echo. The combination of PTC and TFSDS enables us to extract the micro-motion frequency of radar targets with complicated translations without a prior knowledge. Experiments with synthetic and measured data confirm the effectiveness and good performance of the proposed method.