Detection techniques for validating Doppler estimates in heterodyne lidar

We investigate the ability of detection techniques based on the likelihood ratio to discriminate between heterodyne lidar Doppler estimates at low signal levels using examples generated by simulation. The distinction between estimates that are regarded as acceptable and as spurious is based on the Cramer-Rao lower bound. The conditional false alarm probability, which ordinarily describes recording detection of a signal when none is present, is then found to be an approximate upper bound on the probability of selection of a spurious estimate. The method is superior theoretically to similar techniques based on detection functions other than the likelihood ratio. The likelihood ratio also provides a basis for reprocessing rejected data in the light of contextual information provided by those estimates that are accepted.