On-line data reduction of the Doppler-difference autocorrelation function

The application of the Doppler-difference autocorrelation function to estimation of the velocity distribution of gas flows is discussed. The uses of the discrete Fourier transform, the curve-fitting method, and the matrix-transformation method to derive the frequency distribution from the autocorrelation function are described; the effectiveness of the methods are evaluated. It is determined that the matrix-transformation method is the most effective method because it is fast and has no restrictions; the range of application of the Fourier transform method is restricted and the curve-fitting method is time-consuming.