Conductive Shield for Shaping an Electric Field of a Conductive Wire

• US 20130120052A1
• Filed: 07/02/2012
• Published: 05/16/2013
• Est. Priority Date: 11/14/2011
• Status: Active Grant

• Current Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Original Assignee: Atmel Corporation (Microchip Technology Incorporated)
• Inventors: Siska, Andrew
• Granted Patent: US 8,786,356 B2
• Time in Patent Office: Days
• US Class Current: 327/517
• CPC Class Codes: G01R 27/2605 Measuring capacitance capacitive sensors G01D5/24
• CPC Class Codes: G06F 2203/04107 Shielding in digitiser, i.e. guard or shielding arrangements, mostly for capacitive touchscreens, e.g. driven shields, driven grounds
• CPC Class Codes: G06F 2203/04108 Touchless 2D- digitiser, i.e. digitiser detecting the X/Y position of the input means, finger or stylus, also when it does not touch, but is proximate to the digitiser's interaction surface without distance measurement in the Z direction
• CPC Class Codes: G06F 3/041662 using alternate mutual and self-capacitive scanning
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 2217/960765 Details of shielding arrangements
• CPC Class Codes: H03K 2217/96078 Sensor being a wire or a strip, e.g. used in automobile door handles or bumpers

Abstract

In one embodiment, a method comprises generating, by a control unit, a first drive signal and a second drive signal. The method further comprises emitting, by a conductive wire coupled to a capacitive touch sensor, a first electric field that extends in a plurality of directions in response to reception of the first drive signal. The method further comprises shaping, by a conductive shield that surrounds the conductive wire, at least a portion of the first electric field that extends from the capacitive touch sensor towards the conductive shield by generating a second electric field in response to reception of the second drive signal.

Claims

1. A device comprising:

a capacitive touch sensor configured to store an amount of charge indicative of whether an object is within a range of the capacitive touch sensor;

a conductive wire coupled to the capacitive touch sensor, the conductive wire configured to transport a first drive signal to the capacitive touch sensor to charge the capacitive touch sensor, the conductive wire generating a first electric field when transporting the first drive signal;

a dielectric layer surrounding a first portion of the conductive wire;

a conductive shield surrounding the dielectric layer and the first portion of the conductive wire, the conductive shield configured to transport a second drive signal, the conductive shield generating a second electric field when transporting the second drive signal, the second electric field shaping the first electric field generated by the conductive wire;

a control unit coupled to the conductive wire and the shielding cable, the control unit configured to generate the first drive signal and the second drive signal;

a sensing unit configured to sense whether an object is within the range of the capacitive touch sensor based on the amount of charge stored by the capacitive touch sensor; and

a logic circuit in communication with the sensing unit and configured to initiate an action of the device based upon a determination by the sensing unit of whether an object is within the range of the capacitive touch sensor.

2. The device of claim 1, wherein the action initiated by the logic circuit includes turning off the engine of a machine in response to a determination that an object is not within the range of the capacitive touch sensor.

3. The device of claim 1, further comprising a metal steering column of a machine, the metal steering column surrounding at least a portion of the conductive wire and at least a portion of the shielding cable.

4. The device of claim 1, wherein the capacitive touch sensor is a second portion of the conductive wire that is not surrounded by the conductive shield or the dielectric layer.

5. The device of claim 1, wherein the first portion of the conductive wire has a length of at least 10 centimeters.

6. The device of claim 1, further comprising a buffer configured to amplify the first drive signal to generate the second drive signal.

7. The device of claim 1, wherein the first drive signal and the second drive signal have the same phase and polarity.

8. The device of claim 1, further comprising a conductive shield configured to generate a third electric field in response to receiving the second drive signal, the third electric field shaping a fourth electric field generated by the capacitive touch sensor in response to receiving the first drive signal.

9. An apparatus comprising:

a capacitive touch sensor configured to store an amount of charge indicative of whether an object is within a range of the capacitive touch sensor;

a conductive wire coupled to the capacitive touch sensor, the conductive wire configured to transport a first drive signal to the capacitive touch sensor to charge the capacitive touch sensor, the conductive wire generating a first electric field when transporting the first drive signal; and

a conductive shield surrounding a first portion of the conductive wire, the conductive shield configured to transport a second drive signal, the conductive shield generating a second electric field when transporting the second drive signal, the second electric field shaping the first electric field generated by the conductive wire.

10. The apparatus of claim 9, wherein the capacitive touch sensor is a second portion of the conductive wire that is not surrounded by the shielding cable.

11. The apparatus of claim 9, further comprising a buffer that amplifies the first drive signal to generate the second drive signal.

12. The apparatus of claim 9, wherein the conductive wire is a center conductor of a coaxial cable.

13. The apparatus of claim 9, further comprising a dielectric layer between the active conductive shield and the conductive wire, the dielectric layer surrounding the first portion of the conductive wire.

14. The apparatus of claim 9, further comprising a conductive shield configured to generate a third electric field in response to receiving the second drive signal, the third electric field shaping a fourth electric field generated by the capacitive touch sensor in response to receiving the first drive signal.

15. The apparatus of claim 9, wherein the first drive signal and the second drive signal have the same phase and polarity.

16. The apparatus of claim 9, wherein the capacitive touch sensor is a conductive plate.

17. A method comprising:

generating, by a control unit, a first drive signal and a second drive signal;

emitting, by a conductive wire coupled to a capacitive touch sensor, a first electric field that extends in a plurality of directions in response to reception of the first drive signal; and

shaping, by a conductive shield that surrounds the conductive wire, at least a portion of the first electric field that extends from the capacitive touch sensor towards the conductive shield by generating a second electric field in response to reception of the second drive signal.

18. The method of claim 17 further comprising:

measuring an amount of charge stored by the capacitive touch sensor by transferring the charge from the capacitive touch sensor to the control unit through the conductive wire; and

detecting whether an object is within a range of the capacitive touch sensor based on the measured amount of charge.

19. The method of claim 17, wherein the first drive signal and the second drive signal have the same phase and polarity.

20. The method of claim 18, wherein the second drive signal has an amplitude that is greater than the first drive signal.