| 摘要 |
PROBLEM TO BE SOLVED: To provide a self-tuning crystal notch filter which is suitable for blocking a carrier wave signal inside the receiving channel of an ultrasonic imaging system. SOLUTION: Filters 54 and 60 have a resonance frequency which is tuned electronically. Its tuning is performed under the control of software without intervention of an operator. The software instructs channels other than a channel, to be turned, to be transmitted to a transducer. The receiving channel to be tuned amplifiers a received signal, and it transmits the amplified signal to a corresponding digital signal processing(DSP) circuit 88 via the filters 54, 60, a TGC amplifier 28 and an A/D converter 86. The software reads out the amplitude of a digital received signal output from the DSP circuit 88. By programming a D/A converter 66 inside a filter, a value by which the amplitude of the signal output by the DSP circuit 88 is made minimum, i.e., the amount of a prevented carrier-wave signal is made maximum, can be detected. The value is used when imaging data is acquired after that.
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