| 摘要 |
PURPOSE:To make a filter small-scale, by cascading a finite impulse response digital filter and an infinite impulse response digital filter between an interpolator and a thinner. CONSTITUTION:The signal sampled by a sampling frequency f1 is inputted to an interpolator 2, and a zero point is inserted to this signal. A low-pass filter 3 is provided to take out a signal of a frequency f1/2 or below of required components from the frequency spectrum of the signal obtained as the result. In the low-pass filter 3, a finite impulse response digital filter which is a noncyclic digital filter and has the end of the pass band lower than the half of f1 and the end of the attenuation band slightly higher than the half of f1 and an infinite impulse response digital filter which is a cyclic filter and has the end of the pass band slightly lower than the half of f1 and the end of the attenuation band slightly lower then the half of f1 are cascaded. The output of the low-pass filter 3 is thinned by a sampling frequency f2. |
