Patent ID: 6810124
Filing Date: 2004-10-26
Classification: G05B,H03H

Abstract:
An adaptive noise canceling system for tracking and canceling a narrowband noise component present in an output signal of an electronic component without introducing tangible phase shift to said output signal, and wherein said narrowband noise component varies in frequency over a broad frequency spectrum, said noise canceling system comprising:a notch filter having a first input for receiving said output signal from said electronic component, said output signal containing said narrowband noise component; a first scaling multiplier responsive to said output signal from said electronic component; an error reference and gradient system including: a first input responsive to said output signal from said electronic component for generating an error reference signal and an error gradient signal, and a bandpass filter for receiving said output signal from said electronic component, and having a passband sufficiently broad to encompass expected minimum and maximum frequencies of said noise component; an automatic gain control circuit responsive to an output of said bandpass filter; a scaling element responsive to an output of said automatic gain control circuit; a biquadratic allpass filter responsive to an output of said scaling element; an adder for summing an output of said biquadratic allpass filter and said output of said scaling element; a subtractor for receiving said output from said scaling element and said biquadratic allpass filter and producing a difference output signal; a unit delay element responsive to said difference output signal of said subtractor; wherein an output of said adder comprises said error reference signal, and said output of said unit delay element comprises said error gradient signal; a correlator system responsive to said error reference signal and said error gradient signal for generating a tuning parameter signal, said tuning parameter signal being applied to a second input of said notch filter for tuning said notch filter, in real time, to a center frequency of said narrowband noise component, such that said narrowband noise component can be removed by said notch filter; and wherein said error reference and gradient system includes a second input responsive to said tuning parameter signal for modifying said error reference and error gradient signals, in closed loop fashion, to thereby track said narrowband noise component in real time.