| 摘要 |
PURPOSE:To attain high speed filter control while decreasing the storage capacity of the device by using 2 sets of filter coefficients with respect to the indicated resonance index to interpolate the filter coefficient. CONSTITUTION:A filter coefficient with respect to the minimum value of a resonance figure designated by a resonance variable resistor 3 is stored to a coefficient ROM reference by a 1st coefficient generating circuit 1 as to each of discrete cut-off frequencies and a filter coefficient with respect to the maximum value of a resonance figure designated by the resonance variable resistor 3 is stored to a coefficient ROM reference by a 2nd coefficient generating circuit 2 as to each of discrete cut-off frequencies. Then each of the coefficient generating circuits 1, 2 has an interpolation function referencing each coefficient ROM to interpolate the filter coefficient corresponding to the cut-off frequency given via an A/D converter 19 from a variable resistor 18. Thus, while the storage capacity is being saved, the relevant filter coefficient is calculated at high speed by using an indicated value of the variable cut-off frequency and the indicated value of the variable resonance figure. |
