Jc. Rajaonah et al., COMPENSATION OF THE BIAS CAUSED BY THE WALL FILTER ON THE MEAN DOPPLER FREQUENCY, IEEE transactions on ultrasonics, ferroelectrics, and frequency control, 41(6), 1994, pp. 812-819
In the presence of noise, any wall filter induces a bias on the mean D
oppler frequency estimated by the algorithm based on the calculation o
f the phase of the autocorrelation function at lag 1. In this paper, i
t is shown that the bias results from the nonzero value of the autocor
relation function of the filtered noise at lag 1. A general method for
compensating the bias was then deduced. It consists of a preliminary
estimation of the filtered noise contribution and its subtraction from
the autocorrelation function of the Doppler signal. The method is ind
ependent of the nature of the noise and wall filter. An evaluation of
this method on simulated Doppler signals and on measurements from a mo
ving-string phantom showed that effective compensation of the bias was
obtained, but at the expense of a higher variance. Taking into accoun
t both the bias and the variance, however, it was shown that this meth
od offers an improvement over the noncompensated method. Finally, the
performance of this method was demonstrated using in vivo measurements
taken from a human aorta.