Systems and methods for reducing artifacts and improving performance of a multi-path analog-to-digital converter

Patent metadata

Field	Value
Publication number	US-9959856-B2
Application number	US-201514739289-A
Country	US
Kind code	B2
Filing date	Jun 15, 2015
Priority date	Jun 15, 2015
Publication date	May 1, 2018
Grant date	May 1, 2018

Abstract

In accordance with embodiments of the present disclosure, a processing system may include multiple selectable processing paths for processing an analog signal in order to reduce noise, increase dynamic range, and mask audio artifacts associated with a change in noise floor. Techniques are employed to transition between processing paths and calibrate operational parameters of the two paths in order to reduce or eliminate artifacts caused by switching between processing paths.

First claim

What is claimed is:

1. A method of ensuring an inaudible change in noise floor when transitioning between signal paths in a multiple-path analog-to-digital converter system, wherein:
the multiple-path analog-to-digital converter system comprises a controller and a plurality of processing paths including a first processing path and a second processing path, wherein:
the first processing path comprises a first analog-to-digital converter, wherein the first processing path is configured to convert an analog signal into a first digital signal; and
the second processing path comprises a second analog-to-digital converter, wherein the second processing path is configured to convert the analog signal into a second digital signal; and
the controller is configured to select one of the first digital signal and the second digital signal as a digital output signal of the processing system based on a magnitude of the analog signal and, when changing selection between the first digital signal and the second digital signal as the digital output signal, transition between the first digital signal and the second digital signal such that during the transition, the digital output signal is a weighted average of the first digital signal and the second digital signal wherein a weight of the first digital signal relative to a weight of the second digital signal increases or decreases during the transition; and the method comprises:
detecting a condition for auditory masking of the change in the noise floor; and
transitioning between signal paths of the multiple-path analog-to-digital converter system in response to detecting the condition.

2. The method of claim 1 , wherein detecting the condition comprises determining whether a magnitude of an input signal to the multiple-path analog-to-digital converter system is above a predetermined threshold magnitude.

3. The method of claim 1 , wherein detecting the condition comprises:
filtering an input signal to the multiple-path analog-to-digital converter system based on spectral content of the input signal to generate a frequency-filtered input signal; and
determining whether a magnitude of the frequency-filtered input signal is above a predetermined threshold magnitude.

4. The method of claim 3 , wherein filtering the input signal comprises filtering with a filter that models relative loudness perceived by a human ear as a function of frequency of sound incident on the human ear.

5. The method of claim 4 , wherein the filter comprises one of an A-weighting filter and an ISO 226 filter.

6. The method of claim 1 , wherein the signal paths comprise a first processing path for processing audio signals of lower magnitudes and a second processing path for processing audio signals of higher magnitudes, the method further comprising:
generating an adjustable fading coefficient defining the relative levels by which the respective outputs of the first processing path and the second processing path contribute to an overall output signal generated by the multiple-path analog-to-digital converter system during a transition between selection of the first processing path and the second processing path; and
setting a minimum fading level of the fading coefficient to an intermediate fading level between that at which the first processing path contributes entirely to the overall output signal and that at which the second processing path contributes entirely to the overall output signal.

7. The method of claim 1 , wherein:
the condition for auditory masking of the change in the noise floor is a frequency-dependent threshold for switching between signal paths of the multiple-path analog-to-digital converter system; and
transitioning between signal paths of the multiple-path analog-to-digital converter system comprises switching between signal paths of the multiple-path analog-to-digital converter system in response to the audio signal having a magnitude at a frequency of the audio signal increasing above the frequency-dependent threshold at the frequency.

8. A processing system comprising:
a plurality of processing paths including a first processing path and a second processing path, wherein:
the first processing path comprises a first analog-to-digital converter, wherein the first processing path is configured to convert an analog signal into a first digital signal; and
the second processing path comprises a second analog-to-digital converter, wherein the second processing path is configured to convert the analog signal into a second digital signal; and

a controller configured to:
select one of the first digital signal and the second digital signal as a digital output signal of the processing system based on a magnitude of the analog signal;
when changing selection between the first digital signal and the second digital signal as the digital output signal, transition between the first digital signal and the second digital signal such that during the transition, the digital output signal is a weighted average of the first digital signal and the second digital signal wherein a weight of the first digital signal relative to a weight of the second digital signal increases or decreases during the transition;
ensure an inaudible change in noise floor when transitioning between the first processing path and the second processing path by:
detecting a condition for auditory masking of the change in the noise floor; and
transitioning between the first processing path and the second processing path in response to detecting the condition.

9. The processing system of claim 8 , wherein detecting the condition comprises determining whether a magnitude of the analog signal is above a predetermined threshold magnitude.

10. The processing system of claim 8 , wherein the controller implements a filter and detecting the condition comprises:
filtering the input signal with the filter based on spectral content of the input signal to generate a frequency-filtered input signal; and
determining whether a magnitude of the frequency-filtered input signal is above a predetermined threshold magnitude.

11. The processing system of claim 10 , wherein the filter models relative loudness perceived by a human ear as a function of frequency of sound incident on the human ear.

12. The processing system of claim 11 , wherein the filter comprises one of an A-weighting filter and an ISO 226 filter.

13. The processing system of claim 8 , wherein the controller is further configured to:
generate an adjustable fading coefficient defining the relative levels by which the respective outputs of the first processing path and the second processing path contribute to an overall output signal generated by the multiple-path analog-to-digital converter system during a transition between selection of the first processing path and the second processing path; and
set a minimum fading level of the fading coefficient to an intermediate fading level between that at which the first processing path contributes entirely to the overall output signal and that at which the second processing path contributes entirely to the overall output signal.

14. The processing system of claim 8 , wherein:
the condition for auditory masking of the change in the noise floor is a frequency-dependent threshold for switching between signal paths of the multiple-path analog-to-digital converter system; and
transitioning between signal paths of the multiple-path analog-to-digital converter system comprises switching between signal paths of the multiple-path analog-to-digital converter system in response to the audio signal having a magnitude at a frequency of the audio signal incr

Assignees

• Cirrus Logic Int Semiconductor Ltd
• Cirrus Logic Inc

Inventors

• Satoskar Aniruddha
• Allen Daniel J
• Schneider Edmund Mark

Classifications

• H03M1/188 Primary

  Multi-path, i.e. having a separate analogue/digital converter for each possible range · CPC title

• H03M3/466

  Multiplexed conversion systems · CPC title

• H03M1/0631 Primary

  Smoothing · CPC title

• H03M1/0854

  of quantisation noise · CPC title

• H04H20/10

  Arrangements for replacing or switching information during the broadcast or the distribution · CPC title