Patent ID: 8601043

Claim:
An equalizer for equalizing an input signal, comprising: an infinitive impulse response (IIR) filtering portion for filtering the input signal to produce N filtered outputs, wherein the IIR filtering portion includes N IIR filters for simultaneously filtering the input signal to produce the N filtered outputs, respectively, which have respective frequency response transfer functions SB 1 (f)˜SB N (f) fulfilling the following equation: ∑ n = 1 N ⁢ SBn ⁡ ( f ) = ∏ n = 1 N - 1 ⁢ APn ⁡ ( f ) where n is an integer no greater than N−1 and no less than 1 and AP n (f) are frequency response transfer functions of IIR all-pass filters fulfilling the following equation: LP n ( f )+HP n ( f )=AP n ( f ) where LP n (f) are IIR low-pass filters, and HP n (f) are IIR high-pass filters; a gain-adjusting portion coupled to the IIR filtering portion for adjusting the N filtered outputs with N gains to produce N gained outputs, respectively; and an adder for summing the N gained outputs to generate an equalized output signal; wherein N is an integer larger than 2, and when N gains are all set to a first level, an ideally flat frequency response is obtainable by the equalizer and the equalized output signal is an ideal equalized output signal.