| 摘要 |
PURPOSE:To change a changing direction of a specific frequency fo at which a transfer characteristic of a signal waveform starts changing and its rate of change not only in the attenuating direction but also in the increasing direction by changing the specific frequency fo and its rate of change. CONSTITUTION:A transfer function H(Z) of the digital filter 11 is expressed in equation I. The pole of the transfer function H(Z) of the digital filter 11 exists at Z=B1 from the relation of the denominator (1-B1Z<-1>)=0, and the zero of the transfer function H(Z) of the digital filter 11 exists at Z=B2 from the relation of the numerator (1-B2Z<-1>)=0. The pole and the zero exist on a real axis in a unit circle in the Z plane and are marked.(pole) and O (zero). However, whether the gain characteristic is decreasing or increasing depends on whether the B1 is located to the left on the real axis or to the right with respect to the B2, because there are cases of B1<B2, B1>B2 and B1=B2. In the case of B1<B2, let a midpoint between the pole (B1) and the zero (B2) be C, and let the distance between the C and B1 and the distance between the C and B2 be respectively (d), then the relation of equation II is established. When it is desired to reverse the zero and the pole, the sign of the distance (d) is inverted from the relation in the equation II.
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