Time-domain estimation of the center frequency and spread of Doppler spectra in diagnostic ultrasound

Two sets of estimators of the center frequency and mean square bandwidth of a Doppler spectrum are analyzed. The first set is based on a linear combination of the complex autocorrelation of the Doppler signal for different lags. It is shown that the argument (phase angle) of the complex autocorrelation function at unit sample lag is a close approximation to the mean Doppler shift, whereas its modulus (magnitude) gives information about the mean square bandwidth of the spectrum. Approximate expressions for the bias and variance of the estimators are derived, valid for long averaging times. The performances of the estimators are compared for signals with rectangular spectra and different signal-to-noise ratios.<>