Method and apparatus for a tunable high-resolution spectral estimator

• US 20030074191A1
• Filed: 06/04/2002
• Published: 04/17/2003
• Est. Priority Date: 10/22/1998
• Status: Active Grant

• Current Assignee: Washington University In St Louis
• Original Assignee: Washington University In St Louis
• Inventors: Georgiou, Tryphon T., Lindquist, Anders, Byrnes, Christopher I.
• Granted Patent: US 7,233,898 B2
• Time in Patent Office: Days
• US Class Current: 704/203
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• CPC Class Codes: G10L 25/12 the extracted parameters being prediction coefficients
• CPC Class Codes: G10L 25/48 specially adapted for particular use

Abstract

A tunable high resolution spectral estimator is disclosed as a method and apparatus for encoding and decoding signals, signal analysis and synthesis, and for performing high resolution spectral estimation. The invention is comprised of an encoder coupled with either or both of a signal synthesizer and a spectral analyzer. The encoder processes a frame of a time-based input signal by passing it through a bank of lower order filters and estimating a plurality of lower order covariances from which a plurality of filter parameters may be determined. Coupled to the encoder, through any appropriate data link or interface including telecommunication links, is one or both of a signal synthesizer and a spectral analyzer. The signal synthesizer includes a decocer for processing the covariances and a parameter transformer. The signal synthesizer includes a decoder for processing the covariances and a parameter transformer for determining filter parameters for an ARMA filter. An excitation signal is processed through the ARMA filter to reproduce, or synthesize, a representation of the input filter. The spectral analyzer also includes a decoder which processes the covariances for input to a spectral plotter to detemine the power frequency spectrum of the input signal. The invention may be used in a myriad of applications including voice identification, doppler-based radar speed estimation, time delay estimation, and others.

Claims

1. A signal encoder for determining a plurality of filter parameters from an input signal for later reproduction of said signal, said encoder comprising a bank of first order filters, each of said filters being tuned to a preselected frequency, and a covariance estimator connected to the output of said filter bank for estimating covariances from which filter parameters may be calculated for a filter to reproduce said signal.

2. The signal encoder of claim 1 wherein said filter parameters comprise specification of filter bank poles and filter zeros.

3. The signal encoder of claim 2 wherein said filters comprising said bank of filters are adjustable to permit their being tuned to a desired frequency based on a priori information.

4. The signal encoder of claim 2 wherein said filters comprising said bank of filters are adjustable to permit their being tuned to a desired frequency based on properties of said input signal.

5. The signal encoder of claim 4 wherein said properties are measured frequencies of said input signal.

6. The signal encoder of claim 3 wherein the number of filters comprising said filter bank are adjustable.

7. The signal encoder of claim 6 wherein said filter bank parameters at least partially define an ARMA filter, and wherein one or more filter zeros are preselected to further define said ARMA filter.

8. The signal encoder of claim 7 wherein said ARMA filter is of lattice-ladder architecture.

9. The signal encoder of claim 1 further comprising a signal synthesizer coupled to said signal encoder.

10. The signal encoder/signal synthesizer of claim 9 wherein said signal synthesizer further comprises a decoder for receiving the covariances from said signal encoder and produce a plurality of filter parameters in response thereto, a parameter transformer coupled to said decoder, and an ARMA filter coupled to said parameter transformer, said ARMA filter being adjustable to effect reproduction of said input signal through processing of a preselected excitation signal.

11. The signal encoder/signal synthesizer of claim 10 wherein said ARMA filter is adjustable in response to said parameter transformer output.

12. The signal encoder/signal synthesizer of claim 11 wherein said excitation signal is preselected.

13. The signal encoder/signal synthesizer of claim 12 wherein said excitation signal is determined by said signal encoder and communicated to said signal synthesizer for excitation of said ARMA filter.

14. The signal encoder/signal synthesizer of claim 13 wherein said ARMA filter includes filter zeros, and wherein said filter zeros are preselected.

15. The signal encoder/signal synthesizer of claim 13 wherein said ARMA filter includes filter zeros, and wherein said filter zeros are specified by a set of MA parameters generated by said signal encoder, said set of MA parameters being adjustable in response to said input signal.

16. The signal encoder of claim 1 further comprising a spectral analyzer coupled to said signal encoder, said spectral analyzer determining the power frequency spectrum of said input signal in response to the output of said signal encoder.

17. The signal encoder/spectral analyzer of claim 16 wherein said spectral analyzer includes a decoder for producing a set of filter parameters, and a spectral plotter for producing a response reflective of the power frequency spectrum of the input signal.

18. A device for verifying the identity of a speaker based on his spoken speech, said device comprising a voice input device for receiving a speaker'"'"'s voice and processing it for further comparison, a bank of first order filters coupled to said voice input device, each of said filters being tuned to a preselected frequency, a covariance estimator coupled to said filter bank for estimating filter covariances, a decoder coupled to said covariance estimator for producing a plurality of filter parameters, and a comparator for comparing said produced filter parameters with prerecorded speaker input filter parameters and thereby verifying the speaker'"'"'s identity or not.

19. The device of claim 18 further comprising a memory coupled to said comparator for storing said prerecorded speaker input filter parameters.

20. The device of claim 18 further comprising an input device coupled to said comparator to allow for the contemporaneous input of prerecorded speaker filter parameters by a user.

21. A Doppler-based speed estimator comprising a pulse-Doppler radar for producing an output of Doppler frequencies, a HREE filter coupled to said radar, and a spectral plotter coupled to said HREE filter for determining the power frequency spectrum of said radar output, said power frequency spectrum thereby specifying the speed of any objects sensed by said radar.

22. A device for estimating the delay between any two signals, said device including a sensing device for producing a time based output reflective of any delay desired to be estimated, a Fourier transformer for converting said time based output to a frequency based output, a HREE filter coupled to said transformer, and a spectral plotter coupled to said HREE filter for determining the power frequency spectrum of said time based signal, said power frequency spectrum thereby specifying said delay.

23. A method for analyzing a signal comprising the steps of passing said signal through a bank of lower order filters, each of said filters being tuned to a preselected frequency, and estimating a plurality of covariances from the output of said filter bank, said covariances being sufficient for calculating a plurality of filter parameters for a HREE filter, said HREE filter thereby being capable of reproducing said signal.

24. The method of claim 23 further comprising the step of calculating the HREE filter parameters from said covariances, and adjusting a HREE filter in accordance with said calculated filter parameters for reproduction of said signal.

25. The method of claim 24 further comprising the step of adjusting said filter parameters based on the input signal.

26. A method of verifying the identity of a speaker based on his spoken speech, said method comprising the steps of receiving a speaker'"'"'s voice, processing said voice input for further comparison by passing it through a bank of lower order filters, each of said filters being tuned to a preselected frequency, estimating a plurality of filter covariances from said filter outputs, producing a plurality of filter parameters from said filter covariances, and comparing said filter parameters with prerecorded speaker input filter parameters and thereby verifying the speaker'"'"'s identity or not.

27. A method of estimating a speed of an object with a Doppler-based radar comprising the steps of producing an output of Doppler frequencies with said Doppler-based radar, passing said frequencies through a HREE filter, and determining the power frequency spectrum of said frequencies to thereby specify the speed of said object.

28. A method for estimating the delay between any two signals, said method comprising the steps of producing a time based output reflective of any delay desired to be estimated, converting said time based output to a frequency based output by taking its Fourier transform, and determining the power frequency spectrum of said frequency based signal to thereby specify said delay.