Neutralizing Electromagentic Noise for a Capacitive Input Device

• US 20100188362A1
• Filed: 12/16/2009
• Published: 07/29/2010
• Est. Priority Date: 11/28/2005
• Status: Active Grant

• Current Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Original Assignee: Avago Technologies ECBU IP Singapore Pte Limited (Broadcom, Inc.)
• Inventors: Deitz, Zachary T., Mahowald, Peter H., Elsheimer, Robert, Thelen, Robert M., Misek, Brian J.
• Granted Patent: US 8,121,806 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G06F 3/03548 Sliders, in which the moving part moves in a plane
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device
• CPC Class Codes: G06F 3/0418 for error correction or compensation, e.g. based on parallax, calibration or alignment
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G09G 2330/06 Handling electromagnetic interferences [EMI], covering emitted as well as received electromagnetic radiation

Abstract

A method of capturing user control inputs for an electronic device comprises sampling an input measurement signal at a capacitive input sensor of the electronic device to capture user control inputs for operating the electronic device. Electromagnetic interference affecting the sampling or the input measurement signal is electronically neutralized.

Claims

1. A method of capturing user control inputs for an electronic device, the method comprising:

sampling a measurement signal at a capacitive input sensor of the electronic device to capture user control inputs for operating the electronic device; and

neutralizing an electromagnetic noise with the measurement signal adjacent the time the measurement signal is sampled.

2. The method of claim 1 wherein the electromagnetic noise comprises a pulsed radiofrequency signal emitted by the electronic device and wherein neutralizing the electromagnetic noise comprises synchronizing sampling the measurement signal with pulses of the pulsed radiofrequency signal.

3. The method of claim 1 wherein the electromagnetic noise comprises ambient electromagnetic noise coupled to the capacitive input sensor and wherein neutralizing the electromagnetic noise comprises providing a parallel capacitive structure arranged in a mirrored orientation adjacent to the capacitive input sensor to enable sampling the measurement signal via differential signaling.

4. The method of claim 1 wherein the electromagnetic noise comprises ambient electromagnetic noise coupled to the capacitive input sensor and wherein neutralizing the electromagnetic noise comprises substantially randomly varying the sampling of the measurement signal via at least one of:

randomly varying a frequency of the sampling of the measurement signal; and

introducing random time delays in the sampling the measurement signal.

5. A method of capturing user control inputs for an electronic device, the method comprising:

sampling, within a presence of a pulsed radiofrequency signal, a position measurement signal at a capacitive position sensor of the electronic device to capture user control inputs for operating the electronic device; and

synchronizing the sampling of the position measurement signal relative to individual pulses of the pulsed radiofrequency signal.

6. The method of claim 5 wherein synchronizing the sampling of the position measurement signal comprises sampling the position measurement signal only during pulses of the pulsed radiofrequency signal and in between the pulses of the pulsed radiofrequency signal.

7. The method of claim 5 wherein synchronizing the sampling of the position measurement signal comprises sampling the position measurement signal only in between adjacent pulses of the pulsed radiofrequency signal.

8. The method of claim 5 and further comprising:

wirelessly transmitting the pulsed radiofrequency signal from a radiofrequency transceiver of the electronic device; and

wherein synchronizing the sampling comprises providing an electronic communication link between the radiofrequency transceiver and the capacitive position sensor to enable the radiofrequency transceiver to control the synchronizing of the sampling of the position measurement signal.

9. The method of claim 5 wherein synchronizing the sampling comprises tracking the pulsed radiofrequency pulses via an antenna associated with the capacitive position sensor.

10. The method of claim 5 wherein the electronic device comprises a wireless mobile phone and the pulsed radiofrequency signal is transmitted according to a time domain communication access protocol.

11. A capacitive input device comprising:

a capacitive position sensor including;

a plurality of first position electrodes extending in generally the same plane and laterally spaced apart from each other; and

a first sensor electrode generally parallel to and spaced from the plurality of position electrodes, the first sensor electrode being capacitively coupled and slidably movable relative to the first position electrodes;

at least one conductive element positioned generally parallel to and spaced from the plurality of first position electrodes on an opposite side of the plurality of first position electrodes relative to the sensor electrode, the at least one conductive element being stationary relative to the first position electrodes; and

a differential signal controller configured to sample a position measurement signal relative to an overlap capacitance at the capacitive position sensor and the at least one conductive element.

12. The capacitive input device of claim 11, and further comprising:

a ground reference element positioned between the plurality of first position electrodes and the at least one conductive element.

13. The capacitive input device of claim 11 wherein the at least one conductive element comprises:

a plurality of second position electrodes extending in generally the same plane to, and laterally spaced apart from, each other; and

a second sensor electrode generally parallel to and spaced from the plurality of second position electrodes and being capacitively coupled relative to the second position electrodes;

wherein the plurality of second position electrodes and the second sensor electrode are positioned on an opposite side of the first position electrodes relative to the first sensor electrode, and the second sensor electrode is stationary relative to the second position electrodes.

14. The capacitive input device of claim 13, and further comprising:

a first dielectric member disposed between the first sensor electrode and each respective first position electrode; and

a second dielectric member disposed between the second sensor electrode and each respective second position electrode,

wherein the first dielectric member and the second dielectric member are made of the same dielectric material and have the same dielectric value.

15. The capacitive input device of claim 13 wherein the plurality of first position electrodes comprises a first center position electrode located centrally between the other respective first position electrodes and the plurality of second position electrodes comprises a second center position electrode located centrally between the other respective second position electrodes.

16. The capacitive input device of claim 11 wherein the at least one conductive element comprises:

a second sensor electrode generally parallel to and spaced from the plurality of first position electrodes and being capacitively coupled to the first position electrodes, the second sensor electrode being positioned on an opposite side of the first position electrodes relative to the first sensor electrode and having a axed position relative to the first position electrodes.

17. The capacitive input device of claim 11 and further comprising an electronic device incorporating the capacitive input device to enable capture user control inputs for the electronic device via the capacitive input device.

18. A capacitive input system comprising:

a capacitive position sensor; and

a position signal circuit coupled to the capacitive position sensor and configured to periodically sample a position measurement signal at the capacitive position sensor at substantially random intervals.

19. The capacitive input system of claim 18 wherein the position signal circuit comprises a pseudo random signal generator configured to enable a signal mechanism to produce the position measurement signal at the capacitive position sensor and to enable a sampler mechanism to periodically sample the position measurement signal.

20. The capacitive input system of claim 19 wherein the position signal controller comprises a frequency controller coupled to the pseudo random signal generator to randomly vary both a frequency of the position signal and a frequency at which the position signal is periodically sampled via the signal sampler mechanism.

21. The capacitive input system of claim 19 wherein the position signal controller enables periodic sampling at substantially random intervals via a time delay mechanism configured to introduce a random time delay in the periodic sampling of the position signal.

22. The capacitive input system of claim 18 wherein the capacitive position sensor comprises:

a plurality of position electrodes extending in generally the same plane and laterally spaced apart from each other; and

a sensor electrode generally parallel to and spaced from the plurality of position electrodes, the sensor electrode being capacitively coupled and slidably movable relative to the position electrodes.

23. The capacitive input system of claim 22 and further comprising:

at least one conductive element generally parallel to and spaced from the plurality of position electrodes, positioned on an opposite side of the plurality of position electrodes relative to the sensor electrode and fixed relative to the position electrodes; and

a differential signal controller configured to sample the position measurement signal as an overlap capacitance relative to the capacitive position sensor and relative to the at least one conductive element.