抄録
In the conventional ultrasonic pulse Doppler method, target velocity is obtained from the Doppler-shift at the center frequency of the transmitted ultrasonic pulse wave. In this method, since Doppler signals are sampled by the pulse repetition frequency, there is a limit of the measurable velocity due to the sampling theory. This limit gives a serious problem to measure fast velocity components in the practical applications.
In this paper, we propose a new method for determining the Doppler-shift not only at the center frequency but also in the frequency band around it, so that velocity components which are faster than the velocity limit in the conventional method, can be successfully measured. The principle of the new method is confirmed by the theoretical consideration and the experiment in a water tank. The velocity limit of the new method is also investigated theoretically.
