Capacitive sensing apparatus designs

• US 7,548,073 B2
• Filed: 02/13/2007
• Issued: 06/16/2009
• Est. Priority Date: 01/30/2006
• Status: Active Grant

• Current Assignee: Synaptics Incorporated
• Original Assignee: Synaptics Incorporated
• Inventors: Mackey, Bob Lee, Golovchenko, Mykola
• Primary Examiner(s): Dole; Timothy J
• Application Number:
  US11/706,501
• Publication Number:
  US 20070176608A1
• Time in Patent Office: 854 Days
• Field of Search: 324/660, 324/662, 324/663, 324/686, 324/688, 345/173
• US Class Current: 324/660
• CPC Class Codes: G01D 5/2415 adapted for encoders

Abstract

One type of capacitive sensing apparatus has a sensing element that includes a first portion and a second portion adjacent opposite edges of a sensing region. Signals from the first and second portions are combined. Another type of apparatus includes: a first sensing element including first and second portions; a second sensing element including third and fourth portions; and a third sensing element including fifth and sixth portions. The first, third and fifth portions form a first pattern, and the second, fourth and sixth portions form a second pattern. The patterns are bilaterally symmetrical about a median of a sensing region. In another type of apparatus, an electrical conductor coupled to a first sensing element passes through a gap in a second sensing element. An electrical conductor coupled to the second sensing element is dimensioned such that a capacitive coupling to the second sensing element is compensated for the gap.

Claims

1. A capacitive sensing apparatus comprising:

a plurality of electrically conductive sensing elements that have widths that vary according to a periodic waveform and lengths that traverse a sensing region, said sensing elements comprising a first sensing element, a second sensing element and a third sensing element, wherein said third sensing element comprises a first variable-width portion disposed adjacent a first edge of said sensing region and a second variable-width portion disposed adjacent a second edge of said sensing region opposite said first edge;

wherein a first sensor signal is output from said first sensing element and a second sensor signal is output from said second sensing element, and wherein a sensor signal output from said first portion and a sensor signal output from said second portion are combined to provide a third sensor signal.

2. The capacitive sensing apparatus of claim 1 wherein said first and second portions are connected to a same electrical conductor to provide said third sensor signal.

3. The capacitive sensing apparatus of claim 1 wherein a measure of said sensor signal output from said first portion is added to a measure of said sensor signal output from said second portion to provide said third sensor signal.

4. The capacitive sensing apparatus of claim 1 wherein said first, second and third sensing elements do not overlap each other in said sensing region.

5. The capacitive sensing apparatus of claim 1 further comprising circuitry coupled to said plurality of sensing elements, said circuitry operable to use said first, second and third sensor signals to determine an unambiguous position along an axis in the lengthwise dimension of said sensing region.

6. The capacitive sensing apparatus of claim 5 wherein said position is also determined along an axis in the widthwise dimension of said sensing region.

7. The capacitive sensing apparatus of claim 1 further comprising circuitry coupled to said plurality of sensing elements, said circuitry operable to use said first, second and third sensor signals to determine a rate of movement of an object proximate to said sensing region.

8. The capacitive sensing apparatus of claim 1 further comprising an electrode that forms the perimeter of an area that includes said sensing region.

9. The capacitive sensing apparatus of claim 1 wherein the surface areas of said first, second and third sensing elements are substantially equal.

10. The capacitive sensing apparatus of claim 1 wherein said sensing elements further comprise a fourth sensing element, a fifth sensing element and a sixth sensing element, wherein a fourth sensor signal output from said fourth sensing element and said first sensor signal are combined, a fifth sensor signal output from said fifth sensing element and said second sensor signal are combined, and a sixth sensor signal output from said sixth sensing element and said third sensor signal are combined.

11. The capacitive sensing apparatus of claim 1 wherein said waveform comprises a sinusoidal waveform.

12. The capacitive sensing apparatus of claim 1 wherein phases of neighboring sensing elements of said plurality of electrically conductive sensing elements are shifted to produce a complementary set of signals.

13. The capacitive sensing apparatus of claim 11 wherein sensing elements of said plurality of electrically conductive sensing elements each comprise less than one cycle of said sinusoidal waveform and each have a different phase.

14. A capacitive sensing method comprising:

receiving a first sensor signal that is output from a first sensing element of a plurality of electrically conductive sensing elements;

receiving a second sensor signal that is output from a second sensing element of said plurality of electrically conductive sensing elements, wherein said plurality of electrically conductive sensing elements have widths that vary according to a periodic waveform and lengths that traverse a sensing region, said plurality of sensing elements also comprising a third sensing element that comprises a first variable-width portion disposed adjacent a first edge of said sensing region and a second variable-width portion disposed adjacent a second edge of said sensing region opposite said first edge; and

combining a sensor signal output from said first portion and a sensor signal output from said second portion to provide a third sensor signal, wherein said first, second and third sensor signals are useful for determining an unambiguous position along an axis of said sensing region.

15. The method of claim 14 wherein said first, second and third sensing elements do not overlap each other in said sensing region.

16. The method of claim 14 wherein the surface areas of said first, second and third sensing elements are substantially equal.

17. A system comprising:

a plurality of electrically conductive sensing elements that have widths that vary according to a periodic waveform and lengths that traverse a sensing region, said sensing elements comprising a first sensing element, a second sensing element and a third sensing element, wherein said third sensing element comprises a first variable-width portion disposed adjacent a first edge of said sensing region and a second variable-width portion disposed adjacent a second edge of said sensing region opposite said first edge; and

sensing circuitry coupled to said plurality of sensing elements, said sensing circuitry operable for receiving a first sensor signal from said first sensing element and a second sensor signal from said second sensing element, said sensing circuitry also operable for receiving a third sensor signal comprising a sensor signal from said first portion combined with a sensor signal from said second portion.

18. The system of claim 17 further comprising an electrode that forms the perimeter of an area that includes said sensing region.

19. A capacitive sensing apparatus comprising:

means for sensing comprising a first means, a second means and a third means that each have widths that vary according to a periodic waveform and lengths that traverse a sensing region, wherein said third means comprises a first variable-width portion disposed adjacent a first edge of said sensing region and a second variable-width portion disposed adjacent a second edge of said sensing region opposite said first edge;

wherein a first sensor signal is output from said first means and a second sensor signal is output from said second means, and wherein a sensor signal output from said first portion and a sensor signal output from said second portion are combined to provide a third sensor signal.