Extracting instantaneous mean frequency information from Doppler signals using the Wigner distribution function.
The Wigner distribution function (WDF) does not require the analysed signals to be stationary within the time segment used for analysis, and instantaneous frequency (IF) information can be obtained from it. Because of the influence of the cross-power of the signal components, however, the interpretation of the IF results is physically clear only for monocomponent signals with infinite data lengths. The IF results for multicomponent signals also suffer from spike problems and are quite unstable even when the signal-to-noise ratio is high. It is suggested that a "pseudo-instantaneous mean frequency," which uses the positive part of the WDF to follow the power distribution changes among frequency components, is used as a simple and rapid way to track frequency changes of Doppler signals. Simulation results show that the pseudo-instantaneous mean frequency does not have the same spike problems and gives stable and relatively accurate information about frequency changes when the sampling frequency is properly chosen.
Fan
L
L
Division of Medical Physics, Faculty of Medicine, Leicester University, UK.
Evans
D H
DH
D018608:Ultrasonography, Doppler