5563817 :
Adaptive canceller filter module
10
CLAIMS
We claim:
 1. An adaptive canceller filter module means for use with filteredX algorithms in active noise cancellation systems, said module means comprising:
 a first signal sensor means to receive a reference signal;
 a first filter means adapted to produce a cancellation signal in response to said reference signal;
 a second filter means adapted to filter the reference signal produced by the first filter means, the impulse response of which models at least the phase characteristics of the external environment and produces an output signal;
 second signal sensor means to receive an error signal; and
 adaptive means using an adaptive output signal of said second filter means and said error signal to adapt the coefficients of said first filter means to minimize a measure of error.
 2. An adaptive canceller filter module means as in claim 1, wherein the second filter means and adaptive means are integrated into a single unit.
 3. An adaptive canceller filter module means as in claim 1, including a plant error signal generating means adapted to receive input from said signal sensor means and produce a plant error signal which is fed to said adaptive means.
 4. An adaptive canceller filter module means as in claim 1, including a noise generating means adapted to produce said cancellation signal in conjunction with said first filter means.
 5. An adaptive canceller filter module means as in claim 4, wherein the second filter means and the adaptive means consist of one integrated adaptive filter means.
 6. An adaptive canceller filter module means as in claim 1, wherein said first filter means is a FIR filter and said second filter means is a FIR filter.
 7. An adaptive canceller filter module means as in claim 6, wherein said first filter means has a vector of filter coefficients adapted to be acted upon and changed by the adaptive means output signal.
 8. An adaptive canceller filter module means as in claim 7, wherein said filter means comprise an adaptive Finite Impulse Response Filter chip.
 9. The method of minimizing a measure of error in an active noise cancellation system including a first delay line, a vector of filter coefficients, an adapter and a second delay line, comprising:
 providing a reference signal, shifting the contents of said first delay line one place;
 placing the reference signal in the initial position in the delay line;
 convoluting a current values of the filter coefficients with the first delay line to produce an output value;
 shifting the contents of the second delay line one place;
 placing the current input to the second delay line in the initial position thereof; and
 adapting the current values of the filter coefficients according to the adaption algorithm using the current values of the filter coefficients, the contents of the second delay line and an adaption rate to assure convergence.
 10. A method as in claim 9, wherein convoluting the current values of the filter coefficients is performed according to the formulas: [Figure]
