Time-dependent ARMA modeling of continuous wave ultrasonic Doppler signals

This paper presents a new approach to the problem of modeling nonstationary CW ultrasonic Doppler signals. A time-dependent ARMA model whose parameters vary periodically in time is proposed. The time variation of the model parameters is approximated by a weighted sum of a small number of Fourier base functions. It is seen that the spectral characteristics of the model output closely approximate to the spectral characteristics of the nonstationary CW ultrasonic Doppler signals. The technique is applied to blood flow velocity studies.