Interference detection

Patent metadata

Field	Value
Publication number	US-10203809-B2
Application number	US-201715605778-A
Country	US
Kind code	B2
Filing date	May 25, 2017
Priority date	May 25, 2017
Publication date	Feb 12, 2019
Grant date	Feb 12, 2019

Abstract

An input device including: a first in-phase touch sensing block including: an analog mixer configured to mix a resulting signal associated with a capacitive sensor electrode with a local oscillator (LO) signal; an analog to digital converter (ADC) configured to convert an output of the analog mixer into a digital signal; and a first decimation filter configured to determine an in-phase component of an interference at a frequency of the LO signal based, at least in part, on the digital signal; and a first quadrature interference detection block including: a second decimation filter configured to determine a quadrature component of the interference at the frequency.

First claim

What is claimed is:

1. An input device, comprising:
an in-phase touch sensing block comprising:
an analog mixer configured to mix a resulting signal associated with a capacitive sensor electrode with a local oscillator (LO) signal;
an analog to digital converter (ADC) configured to convert an output of the analog mixer into a digital signal; and
a first decimation filter configured to determine an in-phase component of an interference at a frequency of the LO signal based, at least in part, on the digital signal; and

a quadrature interference detection block comprising:
a first digital mixer configured to mix the digital signal from the ADC with an additional digital signal associated with an inverted and sampled version of the LO signal; and
a second decimation filter configured to determine a quadrature component of the interference at the frequency based on an output of the first digital mixer.

2. The input device of claim 1 , further comprising:
an interference engine configured to determine the interference based, at least in part, on the in-phase component determined by the first decimation filter and the quadrature component determined by the second decimation filter.

3. The input device of claim 1 , wherein the quadrature interference detection block further comprises:
a second digital mixer configured to mix the output of the first digital mixer with an orthogonal and sampled version of the LO signal,
wherein the second decimation filter inputs an output signal of the second digital mixer, and
wherein the additional digital signal is the inverted and sampled version of the LO signal.

4. The input device of claim 1 , wherein the additional digital signal is a ratio signal, and wherein the ratio signal is a ratio of an orthogonal and sampled version of the LO signal to the sampled version of the LO signal.

5. The input device of claim 1 , wherein the LO signal comprises a square wave.

6. The input device of claim 1 , wherein the first decimation filter determines the in-phase component during a first time window, wherein the second decimation filter determines the quadrature component during the first time window, and wherein the in-phase touch sensing block detects user input proximate to the capacitive sensor electrode during a second time window.

7. An input device, comprising:
a first in-phase touch sensing block comprising:
an analog mixer configured to mix a resulting signal associated with a capacitive sensor electrode with a local oscillator (LO) signal;
an analog to digital converter (ADC) configured to convert an output of the analog mixer into a digital signal; and
a first decimation filter configured to determine an in-phase component of an interference at a frequency of the LO signal based, at least in part, on the digital signal;

a first quadrature interference detection block comprising a second decimation filter configured to determine a quadrature component of the interference at the frequency;
a second in-phase touch sensing block comprising a third decimation filter;
a second quadrature interference detection block comprising a fourth decimation filter;
a filter coefficient engine configured to calculate a plurality of filter coefficients; and
a digital mixer configured to mix, for use by the second decimation filter and the fourth decimation filter, the plurality of filter coefficients with a ratio signal,
wherein the ratio signal is a ratio of an orthogonal and sampled version of the LO signal to a sampled version of the LO signal.

8. An input device, comprising:
a first in-phase touch sensing block configure to detect user input proximate to a first capacitive sensor electrode and comprising:
an analog mixer configured to mix a resulting signal associated with the first capacitive sensor electrode with a first local oscillator (LO) signal, wherein the first LO signal comprises a first frequency; and
an analog to digital converter (ADC) configured to convert an output of the analog mixer into a digital signal;

a first digital mixer configured to mix the digital signal from the ADC with an additional digital signal associated with an inverted and sampled version of the first LO signal; and
a first quadrature interference detection block comprising a first plurality of decimation filters configured to determine:
an in-phase component of an interference at a second frequency based on an output of the first digital mixer; and
a quadrature component of the interference at the second frequency.

9. The input device of claim 8 , further comprising:
a second quadrature interference detection block comprising:
a second plurality of decimation filters configured to determine, based on the digital signal from the ADC, an in-phase component and a quadrature component of an interference at a third frequency while the first in-phase touch sensing block is detecting user input.

10. The input device of claim 8 , further comprising:
an interference engine configured to determine the interference based on at least the in-phase component and the quadrature component.

11. The input device of claim 8 , wherein the first quadrature interference detection block further comprises:
a second digital mixer configured to mix the output of the first digital mixer with a second LO signal comprising the second frequency; and
a third digital mixer configured to mix the output of the first digital mixer with an orthogonal version of the second LO signal,
wherein each of the second digital mixer and the third digital mixer is connected to one of the first plurality of decimation filters.

12. The input device of claim 8 , wherein the first quadrature interference detection block further comprises:
a second digital mixer configured to mix the inverted and sampled version of the first LO with a second LO signal comprising the second frequency, wherein the additional digital signal is an output of the second digital mixer;
a third digital mixer configured to mix the inverted and sampled version of the first LO with an orthogonal version of the second LO signal; and
a fourth digital mixer configured to mix an output of the third digital mixer with the digital signal from the ADC,
wherein each of the first digital mixer and the fourth digital mixer is connected to one of the first plurality of decimation filters.

13. The input device of claim 8 , wherein the first local oscillator signal comprises a square wave.

14. An input device, comprising:
a first in-phase touch sensing block configure to detect user input proximate to a first capacitive sensor electrode and comprising:
an analog mixer configured to mix a resulting signal associated with the first capacitive sensor electrode with a first local oscillator (LO) signal, wherein the first LO signal comprises a first frequency; and
an analog to digital converter (ADC) configured to convert an output of the analog mixer into a digital signal; and

a first quadrature interference detection block comprising:
a first plurality of decimation filters configured to determine, based at least in part on the digital signal from the ADC, an in-phase component and a quadrature component of an interference at a second frequency;

a second in-phase touch sensing block configured to detect user input proximate to a second capacitive sensor electrode;
a second quadrature interference detection block comprising a second plurality of decimation filters;
a filter coefficient engine configured to determine a plurality of filter coefficients;
a first digital mixer configured to mix an inverted and sampled version of the first LO signal with a seco

Assignees

• Synaptics Inc

Inventors

• Sobel David
• Shan Peijun

Classifications

• G06F3/044

  by capacitive means · CPC title

• G06F3/0418 Primary

  for error correction or compensation, e.g. based on parallax, calibration or alignment · CPC title

• G06F3/0445 Primary

  using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer · CPC title

• G06F3/04182 Primary

  Filtering of noise external to the device and not generated by digitiser components · CPC title