Sign of the wind vector: a simple method for its determination with a homodyne cw laser Doppler velocimeter.

A simple method has been developed to determine the sign of the wind vector in a homodyne cw laser Doppler velocimeter (LDV). In contrast to the usual heterodyne technique-which requires the signal carrier frequency to be large compared to the signal frequency-this method makes use of a small additional frequency change which is superimposed onto either the signal or the local oscillator reference beam. Therefore, the sign of the wind signal Doppler shift can easily be determined and the ambiguity in wind direction-typical for homodyne systems-is removed. Some inconsistencies in earlier publications concerning vertical wind components are now explainable.