Adaptive filters for frequency estimate of heterodyne Doppler lidar returns: Recursive implementation and quality control

Unreliable frequency estimates at low signal-to-noise ratios, provided by a heterodyne Doppler lidar (HDL), undermines any data analysis scheme requir ing high-accuracy wind fields retrievals. To meet demanding specifications, that is, high accuracy associated with high reliability on radial velocity components, a quality control (QC) procedure has to be implemented at sign al processing level. The authors propose use of a recursive implementation of an adaptive filter for frequency estimate coupled with a QC that combine s a statistical test on the signal energy filtered out as proposed by Rye a nd Hardesty and a persistency criterion (PC). The PC leads to improved perf ormance with respect to the percentage of data finally accepted and frequen cy accuracy. The performance is validated using simulated signals and HDL a ctual data.