Patent ID: 6078384
Filing Date: 2000-06-20
Classification: G01P,G01S,Y02A

Abstract:
A Method for the evaluation of laser Doppler signals using a laser Doppler anemometer (LDA) with bandpass filtration and frequency tracking demodulation to compensate for changes in the Doppler frequency with respect to the bandpass filtration, comprising:generating at least one orthogonal frequency system formed of a sine function and a cosine function;transforming said system into a system of rectangular functions having a sequence, recurring at 2.pi., of four state intervals in an invertible one-to-one correlation, wherein interval limits in the form of jumps of one of two additively superimposed rectangular functions are assigned to the state intervals at a phase of .pi./2;comparing, after bandpass filtering and with respect to phase, a detector signal containing the Doppler frequency (f.sub.D) with the state intervals of the orthogonal frequency system, wherein a change in phase position relative to the orthogonal frequency system containing at least one jump and, therefore, a transition to another state interval, is used to trigger said compensation of the change in Doppler frequency (f.sub.D) by generating a regulated mixing frequency (f.sub.M) which is coupled into the LDA; andevaluating the Dopper frequency (f.sub.D) as being an equivalent of said mixing frequency (f.sub.M), wherein the regulated mixing frequency (f.sub.M) is scanned and compared with an orthogonal frequency system, and detected such that a direction of change is designated due to the invertible one-to-one sequence of the state intervals of the orthogonal frequency system.