Channel crosstalk removal

Patent metadata

Field	Value
Publication number	US-9380388-B2
Application number	US-201213629855-A
Country	US
Kind code	B2
Filing date	Sep 28, 2012
Priority date	Sep 28, 2012
Publication date	Jun 28, 2016
Grant date	Jun 28, 2016

Abstract

Techniques for removing crosstalk from a system, e.g., an audio system, having first and second (e.g., left and right) channels. In an aspect, first and second output voltages of corresponding first and second amplifiers are sampled during a calibration mode, in which one of the amplifiers is driven with a reference voltage, and the output of the other of the amplifiers is configured to have a high impedance. The sampled first and second output voltages may be digitized for processing by a processor to estimate a crosstalk removal function. The crosstalk removal function may then be multiplied with the input signals and added in a cross-channel manner to the first and second input signals prior to amplification to remove crosstalk from the system. In certain aspects, multiple reference voltages may be applied during the calibration mode to improve the estimate of the crosstalk removal function.

First claim

The invention claimed is:

1. An apparatus with a first amplifier and a second amplifier, further comprising:
a first adder configured to add a first input signal with a product of a crosstalk removal function and a second input signal, wherein the crosstalk removal function is estimated based on a plurality of sampled first output voltages of the first amplifier and a plurality of sampled second output voltages of the second amplifier, an output of the first adder being coupled to an input of the first amplifier; and
a second adder configured to add the second input signal with a product of the crosstalk removal function and the first input signal, the output of the second adder being coupled to an input of the second amplifier.

2. The apparatus of claim 1 , wherein the first adder is a left adder, the first input signal is a left audio input signal, the first amplifier is a left audio amplifier, the second adder is a right adder, the second input signal is a right audio input signal, and the second amplifier is a right audio amplifier.

3. The apparatus of claim 1 , further comprising a processor configured to estimate the crosstalk removal function based on the plurality of sampled first output voltages and the plurality of sampled second output voltages.

4. The apparatus of claim 3 , the processor further configured to:
configure one of the first and second amplifiers to be driven with a first voltage V 1 while the output of another one of the first and second amplifiers is configured to have high impedance;
sample first-iteration first and second output voltages VOL( 1 ), VOR( 1 ) while driving with the first voltage V 1 ;
configure one of the first and second amplifiers to be driven with a second voltage V 2 distinct from V 1 while the output of another one of the first and second amplifiers is configured to have high impedance; and
sample second-iteration first and second output voltages VOL( 2 ), VOR( 2 ) while driving with the second voltage V 2 .

5. The apparatus of claim 4 , the processor further configured to estimate the crosstalk removal function as a function of [VOR( 2 )−VOR( 1 )]/[VOL( 2 )−VOL( 1 )] or [VOR( 2 )−VOR( 1 )]/[VOL( 2 )−VOL( 1 )].

6. The apparatus of claim 4 , the processor further configured to:
configure one of the first and second amplifiers to be driven with a third voltage V 3 distinct from V 1 and V 2 while the output of another one of the first and second amplifiers is configured to have high impedance; and
sample third-iteration first and second output voltages VOL( 3 ), VOR( 3 ) while driving with the third voltage V 3 .

7. The apparatus of claim 3 , further comprising a multiplexer configured to generate an output signal from selecting between the first output voltage and the second output voltage in response to a control signal generated by the processor.

8. The apparatus of claim 1 , the first and second adders being digital adders, the outputs of the adders coupled to digital-to-analog converters for generating analog signals, the analog signals coupled to the inputs of the first and second amplifiers.

9. The apparatus of claim 1 , further comprising the first amplifier and the second amplifier, the apparatus further comprising:
at least one switch for selectively coupling a ground node to a jack terminal; and
an inductor coupling the ground node to a reference terminal, the reference terminal coupled to input terminals of the first and second amplifiers.

10. The apparatus of claim 1 , further comprising:
a first multiplication element configured to scale the first input signal with a gain adjustment factor prior to the first adder; and
a second multiplication element configured to scale the second input signal with a gain adjustment factor prior to the second adder.

11. An apparatus with a first amplifier and a second amplifier, further comprising:
means for sampling a first output voltage coupled to a first amplifier output of the first amplifier, and for sampling a second output voltage coupled to a second amplifier output of the second amplifier;
means for estimating a crosstalk removal function based on a plurality of sampled first voltages and a plurality of sampled second output voltages; and
means for adding a first input signal with a product of the crosstalk removal function and a second input signal, and for adding the second input signal with a product of the crosstalk removal function and the first input signal.

12. The apparatus of claim 11 , further comprising:
means for configuring one of the first and second amplifiers to be driven with a first voltage V 1 while configuring the output of another one of the first and second amplifiers to have high impedance;
means for sampling the outputs of the amplifiers while driving each amplifier with the first voltage V 1 .

13. The apparatus of claim 12 , wherein the outputs of the amplifiers are sampled while the first amplifier is driven with the first voltage V 1 , and the outputs of the amplifiers are sampled while the second amplifier is driven with a second voltage V 2 .

14. The apparatus of claim 11 , further comprising:
means for converting the first and second output voltages to digital values prior to providing to the means for sampling.

15. The apparatus of claim 11 , the means for sampling comprising means for selecting from between the first and second output voltages in response to a control signal.

16. A method comprising:
estimating a crosstalk removal function based on a plurality of sampled first output voltages of a first amplifier and a plurality of sampled second output voltages of a second amplifier;
adding a first input signal with a product of the crosstalk removal function and a second input signal, an output of the adding the first input signal being coupled to an input of the first amplifier; and
adding the second input signal with a product of the crosstalk removal function and the first input signal, an output of the adding the second input signal being coupled to an input of the second amplifier.

17. The method of claim 16 , further comprising:
setting a digital input signal of the first amplifier to a first value;
setting the output of the second amplifier to a high impedance state;
digitizing the outputs of the first and second amplifiers while the digital input signal is set to the first value;
setting the digital input signal of the first amplifier to a second value; and
digitizing the outputs of the first and second amplifiers while the digital input signal is set to the second value; the estimating the crosstalk removal function comprising calculating the crosstalk removal function from the digitized outputs of the first and second amplifiers.

18. The method of claim 17 , wherein the calculating comprises dividing a difference between the outputs of the second amplifier when the digital input signal is set to the first and second values, by a difference between the outputs of the first amplifier when the digital input is set to the first and second values.

19. The method of claim 16 , wherein the first input signal is a left audio input signal, the first amplifier is a left audio amplifier, the second input signal is a right audio input signal, the second amplifier is a right audio amplifier.

20. The method of claim 16 , further comprising:
selecting between the first and second output voltages for digitization in response to a control signal.

Assignees

• Qualcomm Inc

Inventors

• Bazarjani Seyfollah S
• Mehrabi Arash

Classifications

• H04S1/00

  Two-channel systems (H04S5/00, H04S7/00 take precedence) · CPC title

• H04S1/005

  For headphones · CPC title

• H04R5/04 Primary

  Circuit arrangements, {e.g. for selective connection of amplifier inputs/outputs to loudspeakers, for loudspeaker detection, or for adaptation of settings to personal preferences or hearing impairments (combinations of amplifiers H03F3/68; stereophonic systems H04S)} · CPC title

• H04R1/1041

  Mechanical or electronic switches, or control elements (switches in general H01H) · CPC title