Alias-free interpolation technique for pulsed doppler signal

Conventional pulsed ultrasound Doppler technique has a fundamental limitation in the product of maximum velocity and maximum range because the Doppler shifted frequency is evaluated from the pulsed Doppler signal sampled at pulse repetition frequency, and the range is also restricted by pulse repetition frequency. This limitation sometimes causes the confusion in the measurement of blood flow velocity in a human heart. This paper describes a principle of alias-free interpolation technique for pulsed Doppler signal. This technique enables to synthesize the Doppler signal with high Nyquist frequency by interpolating the roughly spaced samples of the Doppler signal. The velocity range is expanded, and minimum sampling interval is not less than that in conventional technique, so that the range-velocity product can be expanded with this technique. Two cases of the interpolation are shown here. One is the interpolation for the single component Doppler signal and the other is for the two component Doppler signal. It is shown in simulation that these interpolation make the range-velocity product double.