Measurement of Doppler Spectrum Parameters by Crossing Rate Methods

Abstract

The effect of discrete sampling on the measurement of the root mean square frequency frms of the Doppler spectrum by the bipolar video zero-crossing rate method is discussed. It is shown that discrete sampling results in an underestimate of frms. A method of correcting for the underestimate is suggested. Conditional positive and negative axis-crossing rates, or the rates at which the signal vector crosses a phase angle in the counterclockwise and clockwise directions, are defined and shown to be equal to (frms + f?)/2 and (frms ? f?)/2, respectively, where f? is the mean of the Doppler spectrum of the signal. This result suggests that the conditional axis-crossing rates may be used for the measurement of spectrum mean and variance. The effect of discrete sampling on the conditional axis-crossing rates is also discussed.