| 摘要 |
PROBLEM TO BE SOLVED: To obtain a digital filter capable of obtaining sufficient attenuation characteristics, even if a numeric calculation cycle is larger than an attenuation point frequency by having specific characteristics and operating an output from plural inputs. SOLUTION: This digital filter has characteristics represented by expressions I to III, operates an output Y(k) from inputs X(k), X(k-1), X(k-2),... and X(k-2m) of the closest 2m+1 time (where (m) is a natural number) and has the characteristics of a notch filter. However,θi=i×ωb×T, whereinωrepresents an attenuation point angle frequency and T represents a numerical calculation cycle. Even through an FOR type low-pass filter characteristics is included in the notch filter in this case, the digital filter is not limited by this, and for instance, a low-pass filter realized by hardware can serially be connected to the notch filter. Thus, it is possible to obtain sufficient attenuation characteristics, even if the numerical calculation cycle is large with respect to the attenuation point frequency.
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