While there are many topologies for implementing a graphical equalizer, this research explores a design and implementation that is based on time-varying infinite impulse response (IIR) filters. Filter blocks are obtained by interpolating between two time-invariant biquadratic filters having the same center frequency but possibly different gains and bandwidths. This corresponds to crossfading, which avoids transients during transitions. This design is suitable for digital implementation because the variable parameters are excluded from the feedback loops thus avoiding problems of stability during transitions. Moreover, the gain and the bandwidth of the band filters are jointly optimized to minimize interband interferences. Group delays are smaller than multirate or FIR implementations.
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