Signal processing strategy for ALADIN

The atmospheric laser Doppler instrument ALADIN will provide information about the wind velocity using the motion of small particles and the resulting Doppler shift between the transmitted and received laser frequency. The accuracy of the frequency estimation depends mainly on the signal-to-noise ratio (SNR) of the received signal. An improvement of the signal quality i.e. SNR can be done by reducing the bandwidth and by averaging over some shots. The bandwidth reduction can be performed either analogue or digital. The analogue technique includes a lot of risks and error sources, the digital demodulation and filtering shows only one critical component, the analogue to digital converter. The shot averaging can also be performed by two different techniques: coherent or incoherent accumulation. Both, the bandwidth reduction as well as the averaging techniques are presented.