FDM BASED CAPACITIVE TOUCH SYSTEM AND OPERATING METHOD THEREOF

• US 20170139536A1
• Filed: 11/13/2015
• Published: 05/18/2017
• Est. Priority Date: 11/13/2015
• Status: Abandoned Application

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: PixArt Imaging Incorporated
• Inventors: CHEN, Hsin-Chia, CRANDALL, Kenneth, SAHGAL, Raman
• Application Number:
  US14/941,256
• Publication Number:
  US 20170139536A1
• Time in Patent Office: Days
• CPC Class Codes: G06F 3/04166 Details of scanning methods, e.g. sampling time, grouping of sub areas or time sharing with display driving Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally G06F3/04184
• 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: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

A capacitive touch system including a capacitive touch panel, a storage element and a control chip is provided. The storage element is configured to store a lookup table which contains a plurality of mixing signals. The control chip concurrently drives the capacitive touch panel with a plurality of frequency division multiplexed drive signals to generate a plurality of detection signals, and determine a plurality pairs of mixing signals according to the lookup table for respectively modulating the detection signals to generate a plurality pairs of modulated detection signals, wherein the pair of mixing signals corresponding to different drive signals are different from one another.

Claims

1. A capacitive touch system comprising:

a plurality of drive electrodes and a plurality of receiving electrodes configured to form a plurality of sensing elements therebetween;

a plurality of drive circuits respectively coupled to the drive electrodes and configured to concurrently output a plurality of drive signals to the drive electrodes, wherein a plurality of drive frequencies of the drive signals outputted by different drive circuits are different from one another;

a plurality of detection circuits respectively coupled to the receiving electrodes, each of the detection circuits comprising two mixers configured to modulate a detection signal outputted by the coupled receiving electrode with a pair of mixing signals to generate a pair of modulated detection signals; and

a processing unit configured to

determine the pair of mixing signals corresponding to each of the detection circuits according to the drive frequencies, and

calculate a norm of vector of the pair of modulated detection signals to accordingly identify a touch event.

2. The capacitive touch system as claimed in claim 1, wherein each of the detection circuits further comprises two filters configured to filter the pair of modulated detection signals, respectively.

3. The capacitive touch system as claimed in claim 1, wherein each of the detection circuits further comprises two integrators configured to accumulate a plurality of modulated detection signals within a drive slot.

4. The capacitive touch system as claimed in claim 1, wherein the pair of mixing signals is determined according to a lookup table and comprises a sine signal and a cosine signal.

5. The capacitive touch system as claimed in claim 1, wherein phase shifts are formed between drive signals corresponding to different drive frequencies based on a random phase offset or a formulated phase offset.

6. The capacitive touch system as claimed in claim 1, further comprising a plurality of analog to digital convertors respectively coupled between the receiving electrodes and the detection circuits.

7. The capacitive touch system as claimed in claim 1, wherein a circuit number of the detection circuits coupled to each of the receiving electrodes is identical to a frequency number of the drive frequencies.

8. A capacitive touch system comprising

a capacitive touch panel;

a storage element configured to previously store a plurality of mixing signals; and

a control chip configured to

concurrently drive the capacitive touch panel with a plurality of frequency division multiplexed drive signals to output a plurality of detection signals, and

read a plurality pairs of mixing signals from the storage element to respectively modulate the detection signals to generate a plurality pairs of modulated detection signals, wherein the pair of mixing signals corresponding to different drive signals are different from one another.

9. The capacitive touch system as claimed in claim 8, wherein the control chip is further configured to calculate a norm of vector of each pair of modulated detection signals.

10. The capacitive touch system as claimed in claim 8, wherein the storage element stores a lookup table, and the lookup table comprises a generating algorithm of a plurality of sine signals and/or a plurality of cosine signals for generating the mixing signals.

11. The capacitive touch system as claimed in claim 8, wherein the control chip further comprises a plurality of Nyquist filters configured to filter the modulated detection signals.

12. The capacitive touch system as claimed in claim 8, wherein the control chip further comprises a plurality of integrators configured to accumulate the modulated detection signals.

13. The capacitive touch system as claimed in claim 8, wherein the pair of mixing signals corresponding to each of the drive signals is orthogonal to each other.

14. The capacitive touch system as claimed in claim 8, wherein phase shifts are formed between drive signals based on a random phase offset or a formulated phase offset.

15. An operating method of a capacitive touch system, the capacitive touch system comprising a plurality of drive electrodes, a plurality of receiving electrodes, a plurality of drive circuits, a plurality of detection circuits and a processing unit, the operating method comprising:

providing, by the drive circuits, a plurality of drive signals to the drive electrodes, wherein at least a part of a plurality of drive frequencies of the drive signals outputted by different drive circuits are different from one another;

modulating, by each of the detection circuits, a detection signal outputted by the coupled receiving electrode with a pair of mixing signals to generate a pair of modulated detection signals; and

determining, by the processing unit, the pair of mixing signals corresponding to each of the detection signals according to the drive frequencies.

16. The operating method as claimed in claim 15, further comprises:

calculating, by the processing unit, a norm of vector of the pair of modulated detection signals; and

comparing the norm of vector with a threshold.

17. The operating method as claimed in claim 15, further comprising:

filtering the pair of modulated detection signals.

18. The operating method as claimed in claim 15, further comprising:

accumulating a plurality of modulated detection signals within a drive slot.

19. The operating method as claimed in claim 15, further comprising:

digitizing the detection signal.

20. The operating method as claimed in claim 15, wherein the pair of mixing signals is determined according to a lookup table and comprises a sine signal and a cosine signal.