Method and apparatus for controlling coefficients of adaptive filter
A method or apparatus for controlling coefficients of an adaptive filter (3) for identifying unknown system or predicting periodic signals by correcting coefficients of the adaptive filter (3) in such a manner that the difference signal obtained by subtracting an output signal of the adaptive filter (3) from a mixed signal of the output signal from the unknown system and an interference signal comprises steps or means (9) for obtaining the information relating to the magnitude of the coefficients or output of the adaptive filter, and adaptively varying the amount of correction in coefficients of the adaptive filter in response to the obtained information.
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Claims
1. A method of controlling coefficients of an adaptive filter, said method comprising the steps of:
- obtaining a mixed signal by combining an interference signal with an output signal from an unknown system;
- obtaining an output signal generated by said adaptive filter, and subtracting said output signal generated by said adaptive filter from said mixed signal to obtain a difference signal;
- obtaining a square value of the output signal generated by the adaptive filter, and utilizing said square value of the output signal of the adaptive filter as obtained information relating to magnitude of the coefficients of said adaptive filter; and
- adaptively varying corrections applied to the coefficients of said adaptive filter according to said obtained information.
2. A method as defined in claim 1, also comprising:
- obtaining information relating to a short-time average magnitude and a long-time average magnitude of the coefficients of said adaptive filter and utilizing said information to obtain a ratio between said short-time average magnitude and said long-time average magnitude; wherein
- said step of adaptively varying corrections applied to the coefficients of said adaptive filter includes the step of adaptively varying the amount of the corrections applied to the coefficients of said adaptive filter according to the ratio between the short-time average magnitude and the long-time average magnitude of the coefficients of said adaptive filter.
3. A method of controlling coefficients of an adaptive filter, said method comprising the steps of:
- obtaining a mixed signal by combining an interference signal with an output signal from an unknown system;
- obtaining an output signal generated by said adaptive filter, and subtracting said output signal of said adaptive filter from said mixed signal to obtain a difference signal;
- obtaining an absolute value of the output signal generated by the adaptive filter, and utilizing said absolute value of the output signal generated by the adaptive filter as obtained information relating to magnitude of the coefficients of said adaptive filter; and
- adaptively varying corrections applied to the coefficients of said adaptive filter according to said obtained information.
4. A method as defined in claim 3, also comprising:
- obtaining information relating to a short-time average magnitude and a long-time average magnitude of the coefficients of said adaptive filter and utilizing said information to obtain a ratio between said short-time average magnitude and said long-time average magnitude; wherein
- said step of adaptively varying corrections applied to the coefficients of said adaptive filler includes the step of adaptively varying the amount of the corrections applied to the coefficients of said adaptive filter according to the ratio between the short-time average magnitude and the long-time average magnitude of the information on the magnitude of the output signal.
5. A method as defined in claim 4, wherein said step of utilizing said information to obtain the ratio between the short time average magnitude and long time average magnitude comprises the steps of inverting the long time average magnitude to obtain an inverted signal and multiplying the inverted signal by the short time average magnitude, wherein the step of inverting is made by a linear approximation of an exponent of 2.
6. A method as defined in claim 5, wherein the step of inverting includes the step of determining a variable X according to a linear approximation of -2.sup.-2-r X+2.sup.-r-1 (2.sup.-1 +1) using the maximum integer r not exceeding log.sub.2 (x).
7. Electronic filter apparatus comprising:
- an adaptive filter which upon receiving a reference signal generates a pseudo output for an unknown system;
- first means for generating a mixed signal from interference signals and an output signal of the unknown system;
- a first subtracter for subtracting the pseudo output from said mixed signal;
- an information extraction circuit that receives coefficients for the adaptive filter to extract the information on the magnitude of said coefficients and generate an output (a);
- an arithmetic circuit to receive the output (a) for calculating and providing a signal (b) which decreases as the output (a) increases or increases as the output (a) decreases;
- second means for correcting the coefficients of the adaptive filter utilizing the outputs from the first subtracter, said arithmetic circuit and the reference signal; and
- said information extraction circuit comprising a square circuit for developing the output of said adaptive filter.
8. Electronic filter apparatus as set forth in claim 7, wherein said arithmetic circuit comprises a first average circuit for averaging an input signal with a first parameter, a second average circuit for averaging the input signal with a second parameter that differs from the first parameter in said first average circuit, and a divider for developing a ratio of an output of said first average circuit and an output of said second average circuit.
9. Electronic filter apparatus as in claim 8 wherein said divider comprises an inverter for outputting an inverted signal of the output from said second average circuit and a first multiplier for multiplying the inverted signal with the output from said first average circuit.
10. Electronic filter apparatus as set forth in claim 7 wherein said information extraction circuit comprises additional square circuits which together with said square circuit form a group of square circuits each developing a squared value of each coefficient value; and a summer for developing a summed value of outputs of said group of square circuits.
11. Electronic filter apparatus as in claim 7 wherein said arithmetic circuit is an inverse circuit comprising:
- an amplitude evaluation circuit to provide the maximum integer r not exceeding log.sub.2 (X) of an input signal X;
- a second multiplier to multiply the output of said amplitude evaluation circuit by -1;
- a second adder to add -1 to the out/put of said second multiplier;
- a third adder to provide the sum of the outputs of said second multiplier and said second adder;
- a first address generation circuit to provide a RAM address signal to give an exponent of 2 corresponding to the output of said third adder;
- a second address generation circuit to provide a RAM address signal to give an exponent of 2 corresponding to the output of said second adder;
- a RAM to provide a corresponding exponent output of 2 on receiving the outputs of said first and second address generation circuits;
- a third multiplier to multiply the output corresponding to the address generated from said first address generation circuit in said RAM by -1;
- a fourth multiplier to multiply the output of said third multiplier by the input signal to the input terminal;
- a fifth multiplier to multiply the output corresponding to the address generated by said second address generation circuit in said RAM by 1.5; and
- a fourth adder to add the outputs of said fifth and fourth multipliers for outputting from the output terminal.
12. Electronic filter apparatus comprising:
- an adaptive filter which upon receiving a reference signal generates a pseudo output for an unknown system;
- first means for generating a mixed signal from interference signals and an output signal of the unknown system;
- a first subtracter for subtracting the pseudo output from said mixed signal;
- an information extraction circuit comprising a circuit that receives coefficients for the adaptive filter to extract the information on the magnitude of said coefficients and generate an output (a);
- an arithmetic circuit to receive the output (a) for calculating and providing a signal (b) which decreases as the output (a) increases or increases as the output (a) decreases;
- second means for correcting the coefficients of the adaptive filter utilizing the outputs from the first subtracter, said arithmetic circuit and the reference signal; and
- said information extraction circuit also comprising an absolute value circuit for developing an absolute value of the output of said adaptive filter.
13. Electronic filter apparatus as set forth in claim 12 wherein said information extraction circuit further comprises additional absolute value circuits which together with other portions of said information extraction circuit form a group of absolute value circuits each developing an absolute value of each coefficient value, and a first summer for developing a summed value of the outputs of said group of absolute value circuits.
14. Electronic filter apparatus comprising:
- an adaptive filter which upon receiving a reference signal generates a pseudo output for an unknown system;
- first means for generating a mixed signal from interference signals and an output signal of the unknown system;
- a first subtracter for subtracting the pseudo output from said mixed signal;
- an information extraction circuit that receives the output signal for the adaptive filter to extract the information on the magnitude of coefficients for the adaptive filter and generate an output (a);
- an arithmetic circuit to receive the output (a) for calculating and providing a signal (b) which decreases as the output (a) increases or increases as the output (a) decreases;
- second means for correcting the coefficients of the adaptive filter utilizing the outputs from the first subtracter, said arithmetic circuit and the reference signal; and
- said information extraction circuit comprising a square circuit for developing the output of said adaptive filter.
15. Electronic filter apparatus comprising:
- an adaptive filter which upon receiving a reference signal generates a pseudo output for an unknown system;
- first means for generating a mixed signal from interference signals and an output signal of the unknown system;
- a first subtracter for subtracting the pseudo output from said mixed signal;
- an information extraction circuit that receives the output signal of the adaptive filter to extract the information on the magnitude of coefficients for the adaptive filter and generate an output (a);
- an arithmetic circuit to receive the output (a) for calculating and providing a signal (b) which decreases as the output (a) increases or increases as the output (a) decreases;
- second means for correcting the coefficients of the adaptive filter utilizing the outputs from the first subtracter, said arithmetic circuit and the reference signal; and
- said information extraction circuit comprising an absolute value circuit for developing an absolute value of the output of said adaptive filter.
16. Electronic filter apparatus as set forth in claim 5, wherein said arithmetic circuit comprises a first average circuit for averaging an input signal with a first parameter, a second average circuit for averaging the input signal with a second parameter that differs from the first parameter in said first average circuit, and a divider for developing a ratio of an output of said first average circuit and an output of said second average circuit.
17. Electronic filter apparatus as in claim 15 wherein:
- said arithmetic circuit comprises a first average circuit for averaging an input signal with a first parameter, a second average circuit for averaging the input signal with a second parameter that differs from the first parameter in said first average circuit, and a divider for developing a ratio of an output of said first average circuit and an output of second average circuit; and
- said divider comprises an inverter for outputting an inverted signal of the output from said second average circuit and a first multiplier for multiplying the inverted signal with the output from said first average circuit.
18. A method of controlling coefficients of an adaptive filter, said method comprising the steps of:
- obtaining a mixed signal by combining an interference signal with an output signal from an unknown system;
- obtaining an output signal generated by said adaptive filter, and subtracting said output signal generated by said adaptive filter from said mixed signal to obtain a difference signal;
- obtaining a square value of the output signal generated by the adaptive filter, and utilizing said square value of the output signal generated by the adaptive filter as obtained information relating to magnitude of the output signal of said adaptive filter; and
- adaptively varying corrections applied to the coefficients of said adaptive filter according to said obtained information.
19. A method of controlling coefficients of an adaptive filter, said method comprising the steps of:
- obtaining a mixed signal by combining an interference signal with an output signal from an unknown system;
- obtaining an output signal generated by said adaptive filter, and subtracting said output signal generated by said adaptive filter from said mixed signal to obtain a difference signal;
- obtaining an absolute value of the output signal generated by the adaptive filter, and utilizing an absolute value of the output signal generated by the adaptive filter as obtained information relating to magnitude of the output signal of said adaptive filter; and
- adaptively varying corrections applied to the coefficients of said adaptive filter according to said obtained information.
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- "A Fast Convergence Algorithm For Adaptive Fir Filters", Akihiko Sugiyama et al., Institute of Electrical and Electronics Engineers, May 23-26, 1989, vol. 2, pp. 892-895.
Type: Grant
Filed: May 30, 1995
Date of Patent: Aug 4, 1998
Assignee: NEC Corporation
Inventor: Akihiko Sugiyama (Tokyo)
Primary Examiner: David H. Malzahn
Law Firm: Ostrolenk, Faber, Gerb & Soffen, LLP
Application Number: 8/453,152
International Classification: G06F 1710;
