Digital filter


PURPOSE:To realize the approximation of the desired frequency (amplitude) characteristics on a nonlinear frequency scale like a mel scale, etc., by converting the delay element of a nonangular feedback type filter into a full band pass filter. CONSTITUTION:It is supposed that the transmission function H(z) of a digital filter to be attained is obtained by the polynomials (1) and (2) of the transmission function HA(z) of an appropriate full band pass filter. The frequency characteristics HA(e<j> ) is shown by the formulae (3) and (4), where OMEGA=omegaDELTAt, omega: angular frequency, DELTAt: unit delay time of digital filter. Accordingly the frequency H(e<j> ) of the desired filter is shown by the formula (5). The coefficient gm is selected so that the approximation is possible to the desired frequency characteristics G(OMEGA') given with a nonlinear frequency OMEGA' with the value of the formula (5).




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Patent Citations (2)

    Publication numberPublication dateAssigneeTitle
    JP-S52123152-AOctober 17, 1977Enuefu Kairo Setsukei BurotsukDigital filter
    JP-S539450-AJanuary 27, 1978Nec CorpPrimary digital overall areas passing circuit

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Cited By (3)

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    JP-H053237-B2January 14, 1993Matsushita Electric Ind Co Ltd
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    JP-S59148595-AAugust 25, 1984Matsushita Electric Ind Co LtdElectric cleaning machine