IMPROVED ESTIMATION OF LOW VELOCITIES IN COLOR DOPPLER IMAGING BY ADAPTING THE MEAN FREQUENCY ESTIMATOR TO THE CLUTTER REJECTION FILTER

An adaptive mean frequency estimator is proposed for color how imaging , It is based on a series expansion of the first derivative of the aut ocorrelation function of the Doppler signal at origin, Its bias can be reduced by shifting the integration bounds in the series expansion an d its variance adjusted by adapting the coefficients of the serial dev elopment, This estimator can be fitted to the specific characteristics of the clutter rejection filter using the signal-to-noise ratio (SNR) of the Doppler signal as an adaptive parameter, Its performance is co mpared to that of the usual correlation angle estimator, and its thres holded version, as well as that of the general mean frequency estimato r, using a model of Doppler signal, The detection of low frequencies w as significantly improved, The mean square error (MSE) was reduced an average 15 fold over a 25-dB range on the SNR, compared to the correla tion angle estimator (CAE) or the general mean frequency estimator, A two-fold reduction in the MSE was obtained compared to the thresholded correlation angle estimator.