| 摘要 |
Constants {Pb00i, Qb00j, . . . , Pak2i, Qak2j, Pci, Qcj, Pdi, and Qdj} for calculating each of filter coefficients {ak1, ak2, b00, bk1, bk2, c and d} for a digital filter 15 by using non-linear polynomials for pass band position data x and pass band width data y are stored in a memory 13. The constants {Pb00i, Qb00j, . . . , Pak2i, Qak2j, Pci, Qcj, Pdi, and Qdj} are determined by using the least square method so that the sum of the square of the errors between the filter coefficients calculated by using non-liner polynomials and the filter coefficients of digital filter having known characteristics becomes the least or the minimum. A CPU 11 calculates the filter coefficients non-linearly by using the constants stored in the memory 13, and sets the results to the digital filter 15 when new pass band position data x or pass band width data y is input at knobs SC and SW.
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