| 摘要 |
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.
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