| 摘要 |
A decimation filter in which a coefficient word length of a last-stage FIR filter is shorter than that which attains a necessary attenuation rate, and an interpolation filter in which a coefficient word length of a first-stage FIR filter is the same. The coefficient is arranged such that a region in which attenuation is insufficient is caused intensively around a Nyquist frequency. The attenuation in such a region relative to the first or last-stage FIR filter is enhanced so as to ensure sufficient attenuation, by its preceding or following FIR filter. As a result, sufficient attenuation is maintained in an inhibition region while maintaining a relatively small circuit size.
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