A Design Method for Linear Phase FIR Filters with Multiple Variable Factors in the Stopband and Specified High Attenuation
Toma Miyata, Takahiro Natori, Naoyuki Aikawa · 2019
To measure mass of goods, automatic checkweighers are widely used, and is composed by a sensor of scale and a conveyor-belt. Variable digital filters (VDFs) are used to reduce the noise overlapping on the measurement signals in the instruments. The VDFs have piecewise high attenuation in the stopband to reduce delay. Conventional VDFs were difficult to obtain the desired piecewise high attenuation in order to change the attenuation by weight function. In this paper, we are proposed a design method for equiripple linear-phase FIR filters having multiple variable components in the stopband and the specified piecewise high attenuation. The proposed method adds a constraint in the minimax design problem, that directly changes piecewise high attenuation band by a variable parameter. The optimization methodology known as semi-definite programming (SDP) is used. The obtained VDF has high attenuation in part of the stopband, and then its attenuation, position, and stopband edge frequency are variable. Effectiveness of the proposed method is illustrated by a design example.