| 摘要 |
PROBLEM TO BE SOLVED: To precisely obtain information about a movement speed by reducing the influence of noise caused by the periodical operation of equipment arranged in the periphery of an ultrasonic probe. SOLUTION: A signal processing circuit 15 orthogonally detects a reflected ultrasonic signal, Fourier-transforms an orthogonal analytic signal obtained by this, and judges Doppler shift based on a component about a frequency band other than a prescribed frequency band containing OHz in the result of the Fourier transformation. A system control circuit 19 judges the operation frequency of an electric appliance (such as an insulation type switching power source 42) existing in the periphery of the probe 2 and performing the periodical operation, and sets a sampling frequency in the Fourier transformation so as to become a measure of the operation frequency. COPYRIGHT: (C)2007,JPO&INPIT
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