指定減衰量と阻止帯域が可変な直線位相可変FIRフィルタの等リプル設計法

抄録

Variable digital FIR filters (VDFs) are used to reduce noise in automatic weighing instruments. VDFs can reduce delay without degrading measurement accuracy by piecewise high attenuation in the stopband. However, conventional VDFs were difficult to obtain the desired piecewise high attenuation in order to change the attenuation by weight function. In this paper, we propose a design method for equiripple linear-phase variable digital FIR filter having the specified piecewise high attenuation in the stopband. The proposed VDF has high attenuation in part of the stopband, and its attenuation, position, and stopband edge frequency are variable. The VDF's filter coefficients are realized by polynomial using variable parameters. Therefore, when multiple elements are varied, the polynomial orders increase. The proposed method reduces the degree of the polynomial by taking advantage of the fact that the higher order terms of the polynomial have little effect on the filter coefficients. The proposed method adds and a constraint in the minimax design problem, that directly changes piecewise high attenuation band by a variable parameter. Effectiveness of the proposed method is illustrated by design examples.