A. Zeira et al., PSEUDO-WIGNER DISTRIBUTION FOR ANALYSIS OF PULSED DOPPLER ULTRASOUND, IEEE transactions on ultrasonics, ferroelectrics, and frequency control, 41(3), 1994, pp. 346-352
Existing pulsed Doppler ultrasound systems apply the spectrogram as a
tool for analysis and display of signals scattered from the blood. The
spectrogram is a time-frequency representation (TFR) of a signal that
maps a one-dimensional signal of time into a two-dimensional function
of time and frequency. The analysis of Doppler ultrasound signals req
uires application of a two-dimensional TFR rather than one-dimensional
spectral representations due to the nonstationary nature of the signa
ls scattered from blood. The classical spectrogram is a smoothed Wigne
r distribution (SWD) with a specific smoothing function. For this smoo
thing function, the smoothing, and hence the resolution in time and fr
equency, cannot be controlled independently. The purpose of this study
is to examine the application of other SWD's to analysis and display
of Doppler ultrasound signals. The present paper concentrates on the p
seudo-Wigner distribution (PWD). The PWD and the spectrogram are exami
ned and compared as analysis tools for nonstationary Doppler ultrasoun
d signals. The performance of these two TFR's as a function of Doppler
bandwidth is evaluated and compared for time-varying flow.