| 摘要 |
PURPOSE:To exactly measure a high blood flow speed by deriving in advance an instantaneous phase difference vector of a receiving signal between continuous transmitting pulses, and also, measuring a difference of Doppler frequencies, and deriving a speed by an operation. CONSTITUTION:Two continuous phase difference vectors U1 and Ui+1 in a repeated period gamma of a transmitting pulse are measure,d and a difference of both the vectors, that is, a difference vector Si=Ui+1.Ui* (* denotes a complex conjugate) of a phase difference is measured. Accordingly, even if the phase difference vector Ui+1 is brought to area sing, unless a phase difference DELTAtheta1 and a difference DELTADELTAtheta1 of the phase difference are brought to area sing, a phase difference DELTAi+1 is derived exactly. In this case, by using an output of a conventional method speed arithmetic circuit 1, an average phase difference (DELTAtheta)2 being free from a phase difference area sing (a first area sing) is obtained. However, in the case the difference of the phase difference is brought to area sing (a second area sing) and exceeds pi, a phase difference arithmetic output of an acceleration cumulating method speed arithmetic circuit 2 is inputted to a second area sing detecting circuit 3, corrected, and thereafter, an exact phase difference output (DELTAtheta)2 is obtained from a terminal 69. |
