| 摘要 |
PURPOSE:To simplify the scale of a circuit and to lower a price, by calculating the output of a digital filter on the other side based on a differential output between the input data and the output data of the digital filter on one side of a digital HPF having a cut-off frequency equivalent to that of a digital LPF. CONSTITUTION:The titled device is constituted of the digital LPF having a prescribed cut-off frequency, and the digital HPF having the cut-off frequency equivalent to that of the prescribed cut-off frequency. And it is formed so that the output of the digital filter on the other side can be calculated based on the differential output of the input data and the output data of the digital filter on one side. Assuming an input signal as X, an output signal as Y/2, an impressing voltage applied on both ends of a capacitor C as Y, and a voltage impressed on a resistor R as the synthetic resistor of two resistors R/2, an integral output can be obtained by a digital LPF circuit, and thereby, the output of a differentiation circuit can be obtained indirectly based on an equation X=X-Y. Furthermore, by performing the approximate arithmetic operation of an emitter follower circuit based on the above operation, the digital HPF is constituted, and respective time constant circuit included in a time constant network 70 becomes the same type of digital filter. Furthermore, by making allowance in the processing time of each digital filter, it is possible to constitute the circuit in which one digital filter can be shared.
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