Signal Detection, Processing and Validation

Abstract

Signal processing is understood as the process of determining the primary measurement quantities from the analog or digitized signal of the photodetector. The signal frequency is the foremost primary measurement quantity to be determined in the laser Doppler technique and the phase difference between two signals is an additional quantity to be determined in the phase Doppler technique. Further quantities, such as the arrival time, the signal duration (also known as transit time or residence time), amplitude and signal-to-noise ratio (SNR), are all necessary for some applications or with other measurement techniques. Processing these primary quantities into secondary quantities directly related to the fluid mechanics of the flow, for instance the mean velocity or spectral distributions of the flow fluctuations, will be referred to as data processing and is addressed in detail in chapters 11 and 12.