Electrical audio signal processing systems and devices – Including frequency control – Having automatic equalizer circuit
Patent
1983-10-12
1986-01-21
Isen, Forester W.
Electrical audio signal processing systems and devices
Including frequency control
Having automatic equalizer circuit
333 28T, H03G 500
Patent
active
045661197
ABSTRACT:
An adjustable equalizer network comprises a series chain of N all pass amplifier stages driving M minimum phase shift transversal filters connected to a final summing circuit that includes means to adjust each filter output to obtain a ripple free predetermined frequency response over a given frequency range. Each filter includes N+1 scaling circuits connected to an intermediate summing circuit; the scaling circuits have scaling coefficients, of magnitude and sign determined by Fourier analysis and an appropriate truncation function, such that the filter has a pass band representative of one of M contiguous bands conjointly encompassing the frequency range. The adjustable equalizer, once adjusted for a desired frequency response, may be supplied with a DC reference input and used to determine the contribution (magnitude and sign) to the frequency response from each tap on the all pass chain, thus developing a set of N+1 scaling coefficients for a simplified equalizer network, comprising the all pass chain with just one set of N+1 scaling circuits, that duplicates the response characteristic of the more complex adjustable equalizer. Some embodiments incorporate digital programming and control of the frequency response characteristic.
REFERENCES:
patent: 2024900 (1935-12-01), Wiener et al.
patent: 2128257 (1938-08-01), Lee et al.
patent: 3624298 (1971-11-01), Davis et al.
patent: 3715666 (1973-02-01), Mueller et al.
Tattersall, Linear Phase Analog Active Filters with Equiripple Passband Responses, IEEE Transactions on Circuits and Systems, vol. CAS-28, No. 9, pp. 925-927.
Industrial Products, Inc.
Isen Forester W.
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