TIME-BASED FREQUENCY TUNING OF ANALOG-TO-INFORMATION FEATURE EXTRACTION

• US 20190318720A1
• Filed: 06/26/2019
• Published: 10/17/2019
• Est. Priority Date: 10/22/2015
• Status: Active Grant

• Current Assignee: Texas Instruments, Inc.
• Original Assignee: Texas Instruments, Inc.
• Inventors: Zhang, Zhenyong, Ma, Wei
• Granted Patent: US 11,302,306 B2
• Time in Patent Office: Days
• CPC Class Codes: G10L 15/02 Feature extraction for speech recognition; Selection of recognition unit
• CPC Class Codes: G10L 15/22 Procedures used during a speech recognition process, e.g. man-machine dialogue
• CPC Class Codes: G10L 15/30 Distributed recognition, e.g. in client-server systems, for mobile phones or network applications
• CPC Class Codes: G10L 15/32 Multiple recognisers used in sequence or in parallel; Score combination systems therefor, e.g. voting systems
• CPC Class Codes: G10L 21/0224 Processing in the time domain
• CPC Class Codes: G10L 21/0264 characterised by the type of parameter measurement, e.g. correlation techniques, zero crossing techniques or predictive techniques
• CPC Class Codes: G10L 25/09 the extracted parameters being zero crossing rates
• CPC Class Codes: G10L 25/21 the extracted parameters being power information

Abstract

A sound recognition system including time-dependent analog filtered feature extraction and sequencing. An analog front end (AFE) in the system receives input analog signals, such as signals representing an audio input to a microphone. Features in the input signal are extracted, by measuring such attributes as zero crossing events and total energy in filtered versions of the signal with different frequency characteristics at different times during the audio event. In one embodiment, a tunable analog filter is controlled to change its frequency characteristics at different times during the event. In another embodiment, multiple analog filters with different filter characteristics filter the input signal in parallel, and signal features are extracted from each filtered signal; a multiplexer selects the desired features at different times during the event.

Claims

1. A method comprising:

receiving an analog signal;

extracting a first feature from the analog signal, wherein the first feature is associated with a first frequency band;

extracting a second feature from the analog signal, wherein the second feature is associated with a second frequency band that is different from the first frequency band;

multiplexing the first feature and the second feature to form a feature sequence; and

performing analog-to-digital conversion of the feature sequence to form a digitized feature sequence.

2. The method of claim 1 further comprising:

matching the feature sequence according to a matching criterion; and

providing an event trigger in response to the matching of the feature sequence.

3. The method of claim 2 further comprising waking a digital classification logic in response to the event trigger.

4. The method of claim 1 further comprising filtering the analog signal using a first filter associated with the first frequency band to produce a first filtered signal, wherein the extracting of the first feature is performed on the first filtered signal.

5. The method of claim 4 further comprising filtering the analog signal using a second filter associated with the second frequency band to produce a second filtered signal, wherein the extracting of the second feature is performed on the second filtered signal.

6. The method of claim 4, wherein the extracting of the first feature includes analyzing threshold crossing of the first filtered signal.

7. The method of claim 4, wherein the extracting of the first feature includes analyzing energy of the first filtered signal.

8. The method of claim 1, wherein the first feature is associated with a first time interval and the second feature is associated with a second time interval that is different from the first time interval.

9. The method of claim 8, wherein the first time interval and the second time interval have substantially the same duration.

10. An integrated circuit comprising:

first feature extraction circuitry coupled to receive an analog signal and to provide a first signal feature from the analog signal, wherein the first signal feature is associated with a first frequency characteristic;

second feature extraction circuitry coupled to receive the analog signal and to provide a second signal feature from the analog signal, wherein the second signal feature is associated with a second frequency characteristic that is different from the first frequency characteristic;

a multiplexer coupled to the first feature extraction circuitry and the second feature extraction circuitry to provide a feature sequence based on the first and second signal features; and

an analog-to-digital converter coupled to the multiplexer to provide a digitized feature sequence in response to the feature sequence.

11. The integrated circuit of claim 10 further comprising an event trigger coupled to the multiplexer to issue an event trigger signal in response to a match of the feature sequence.

12. The integrated circuit of claim 11 further comprising sound recognition circuitry coupled to wake in response to the event trigger signal.

13. The integrated circuit of claim 10 further comprising:

a first filter to filter the analog signal according to the first frequency characteristic and coupled to provide a first filtered signal to the first feature extraction circuitry; and

a second filter to filter the analog signal according to the second frequency characteristic and coupled to provide a second filtered signal to the second feature extraction circuitry.

14. The integrated circuit of claim 10, wherein:

the first feature extraction circuitry includes a first threshold crossing counter coupled to receive the analog signal; and

the second feature extraction circuitry includes a second threshold crossing counter coupled to receive the analog signal.

15. The integrated circuit of claim 10, wherein:

the first feature extraction circuitry includes a first integrator coupled to receive the analog signal; and

the second feature extraction circuitry includes a second integrator coupled to receive the analog signal.

16. An integrated circuit comprising:

first feature extraction circuitry coupled to receive an analog signal and to extract a first signal feature based on a first property of the analog signal from a first group consisting of;

zero-crossing and total energy of a first frequency band;

second feature extraction circuitry coupled to receive the analog signal and to extract a second signal feature based on a second property of the analog signal from a second group consisting of;

zero-crossing and total energy of a second frequency band that is different from the first frequency band;

a multiplexer coupled to the first feature extraction circuitry and the second feature extraction circuitry to provide a feature sequence comprising the first and second signal features; and

an event trigger coupled to the multiplexer to receive the feature sequence and to provide a trigger in response to a match of the feature sequence.

17. The integrated circuit of claim 16 further comprising:

a first filter to filter the analog signal according to the first frequency band and coupled to provide a first filtered signal to the first feature extraction circuitry; and

a second filter to filter the analog signal according to the second frequency band and coupled to provide a second filtered signal to the second feature extraction circuitry.

18. The integrated circuit of claim 17, wherein the first filter and the second filter are tunable.

19. The integrated circuit of claim 16, wherein the first signal feature is associated with a first time interval and the second signal feature is associated with a second time interval that is different from the first time interval.

20. The integrated circuit of claim 16 further comprising sound recognition circuitry coupled to wake in response to the trigger.