Electronic stylus, capacitive touchpad module, and apparatus for touch input

• US 8,564,553 B2
• Filed: 01/04/2010
• Issued: 10/22/2013
• Est. Priority Date: 01/06/2009
• Status: Expired due to Fees

• Current Assignee: Elan Microelectronics Corporation
• Original Assignee: Elan Microelectronics Corporation
• Inventors: Yeh, I-Hau, Wang, Tsun-Min, Huang, Chun-Chung, Yeh, Chi-Tein, Cheng, Chung-Han, Huang, Hung-Ming
• Primary Examiner(s): Wang, Quan-Zhen
• Assistant Examiner(s): EURICE, MICHAEL
• Application Number:
  US12/651,575
• Publication Number:
  US 20100170726A1
• Time in Patent Office: 1,387 Days
• Field of Search: 178/18.01, 178/18.06, 178/19.03, 178/19.06, 178/19.07, 345/173, 345/179
• US Class Current: 345/173
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/0441 using active external devices, e.g. active pens, for receiving changes in electrical potential transmitted by the digitiser, e.g. tablet driving signals
• CPC Class Codes: G06F 3/0442 using active external devices, e.g. active pens, for transmitting changes in electrical potential to be received by the digitiser
• 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

An electronic stylus emits an excitation signal to apply to a trace of a capacitive touchpad module near a touch point when the electronic stylus touches the capacitive touchpad module, so as to change a waveform of a charging/discharging signal in the trace, and depending on the waveform variation, the capacitive touchpad module can identify the touch point.

Claims

1. An apparatus for touch input, comprising:

a capacitive touchpad module actively driving a plurality of traces with a charging/discharging signal, the capacitive touchpad module including a detection circuit connected to the plurality of traces for detecting the charging/discharging signal conducted by the plurality of traces and sensing a touch input responsive to a capacitive coupling to the capacitive touchpad module changing an amplitude of the charging/discharging signal input to the detection circuit from at least two orthogonal traces of the plurality of traces, the detection circuit generating an excitation signal to have a fixed relationship with respect to a phase and a frequency of the charging/discharging signal; and

an electronic stylus coupled to the detection circuit for receiving the excitation signal therefrom, the electronic stylus including a longitudinally extended housing, a conductive tip disposed at one end of the housing and an insulator disposed between the conductive tip and the housing to provide electrical isolation therebetween, the excitation signal being output from the conductive tip, the excitation signal being capacitively coupled to the least two orthogonal traces of the plurality of traces of the capacitive touchpad module near a touch point when the tip of the electronic stylus touches the capacitive touchpad module, the capacitive coupling of the excitation signal to the at least two orthogonal traces altering the amplitude of the charging/discharging signal to thereby simulate the touch input by a user'"'"'s finger.

2. The apparatus of claim 1, wherein the excitation signal has a frequency which is an integral multiple of that of the charging/discharging signal.

3. The apparatus of claim 1, wherein the excitation signal has a constant phase difference from the charging/discharging signal.

4. The apparatus of claim 1, wherein the excitation signal has a frequency equal to that of the charging/discharging signal and a duty ratio of 50%.

5. The apparatus of claim 1, wherein the excitation signal has a frequency equal to one half of that of the charging/discharging signal and a duty ratio of 25%.

6. The apparatus of claim 1, wherein the excitation signal has a frequency equal to one third of that of the charging/discharging signal and a duty ratio of 16.7%.

7. The apparatus of claim 1, wherein the excitation signal has a frequency equal to one quarter of that of the charging/discharging signal and a duty ratio of 12.5%.

8. The apparatus of claim 1, wherein the tip comprises a metal wrapped by a nonconductor.

9. The apparatus of claim 1, wherein the excitation signal has a waveform where rising edges thereof coincide with rising edges of a waveform of the charging/discharging signal to thereby enable the detection circuit to distinguish a touch input being made by the electronic stylus from a touch input being made by a user'"'"'s finger.

10. The apparatus of claim 1, wherein the electronic stylus is wirelessly coupled to the detection circuit and the capacitive touchpad module further comprises:

an up-converter circuit connected to the detection circuit for up-converting the excitation signal to generate a high-frequency signal; and

a transceiver system connected to the up-converter circuit for transmitting the high-frequency signal to the electronic stylus.

11. The apparatus of claim 10, wherein the electronic stylus comprises:

a down-converter circuit for receiving and down-converting the high-frequency signal to recover the excitation signal, the down-converter circuit having an output coupled to the conductive a tip for emitting the excitation signal.

12. The apparatus of claim 1, wherein the electronic stylus is wirelessly coupled to the detection circuit and the capacitive touchpad module further comprises:

a modulation circuit connected to the detection circuit for modulating the excitation signal to generate a carrier modulated by the excitation signal; and

a transceiver system connected to the modulation circuit for transmitting the carrier to the electronic stylus.

13. The apparatus of claim 12, wherein the electronic stylus comprises:

a demodulation circuit for receiving and demodulating the carrier to recover the excitation signal, the demodulation circuit having an output coupled to the conductive for emitting the excitation signal.

14. A control method for a capacitive touchpad, the control method comprising:

providing a capacitive touchpad module having a plurality of traces formed thereon;

actively driving the plurality of traces with a charging/discharging signal;

providing a detection circuit connected to the plurality of traces for detecting the charging/discharging signal conducted by the plurality of traces;

responsive to a user'"'"'s finger being brought into proximity to the capacitive touchpad module, detecting a change in an amplitude of the charging/discharging signal by the detection circuit for at least two of the plurality of traces disposed orthogonally with respect to one another and thereby identifying a touch input;

providing an electronic stylus;

generating an excitation signal having a fixed relationship with respect to a frequency and a phase of the charging/discharging signal;

supplying the excitation signal to a tip of the electronic stylus for emission therefrom; and

responsive to bringing the tip of the electronic stylus in proximity to the capacitive touchpad module, the emitted excitation signal being capacitively coupled to traces of the capacitive touchpad module, detecting a change in the amplitude of the charging/discharging signal by the detection circuit and for at least two of the plurality of traces disposed orthogonally with respect to one another in proximity to the tip of the electronic stylus and thereby simulate the touch input by a user'"'"'s finger;

wherein the touch input from either one of a user'"'"'s finger or the electronic stylus is detectable.

15. The control method of claim 14, wherein the step of generating an excitation signal having a fixed relationship with respect to a frequency of the charging/discharging signal includes the step of generating the excitation signal having a frequency equal to an integral multiple of a frequency of the charging/discharging signal.

16. The control method of claim 14, wherein the step of generating an excitation signal having a fixed relationship with respect to a frequency of the charging/discharging signal includes the step of generating the excitation signal having a frequency equal to that of the charging/discharging signal and a duty ratio of 50%.

17. The control method of claim 14, wherein the step of generating an excitation signal having a fixed relationship with respect to a frequency of the charging/discharging signal includes the step of generating the excitation signal having a frequency equal to one half of that of the charging/discharging signal and a duty ratio of 25%.

18. The control method of claim 14, wherein the step of generating an excitation signal having a fixed relationship with respect to a frequency of the charging/discharging signal includes the step of generating the excitation signal having a frequency equal to one third of that of the charging/discharging signal and a duty ratio of 16.7%.

19. The control method of claim 14, wherein the step of generating an excitation signal having a fixed relationship with respect to a frequency of the charging/discharging signal includes the step of generating the excitation signal having a frequency equal to one quarter of that of the charging/discharging signal and a duty ratio of 12.5%.

20. The control method of claim 14, wherein the step of generating an excitation signal comprises:

responsive to the charging/discharging signal, the detection circuit generating a detection signal;

up-converting the detection signal for generating a high-frequency signal;

transmitting the high-frequency signal to the electronic stylus; and

receiving and down-converting the high-frequency signal for generating the excitation signal.

21. The control method of claim 14, wherein the step of generating an excitation signal comprises:

responsive to the charging/discharging signal, the detection circuit generating a detection signal;

modulating the detection signal for generating a modulated carrier signal;

transmitting the modulated carrier signal to the electronic stylus; and

receiving and demodulating the modulated carrier signal for generating the excitation signal.

22. The control method of claim 14, wherein the step of generating an excitation signal comprises:

responsive to the charging/discharging signal 1, the detection circuit generating a detection signal;

embedding data representing one of the detection signal or the charging/discharging signal into a carrier signal;

transmitting the carrier signal to the electronic stylus;

extracting the data from the carrier signal; and

generating the excitation signal in correspondence to the extracted data.

23. The control method of claim 14, wherein the step of generating an excitation signal includes the step of generating the excitation signal with a waveform thereof having rising edges that coincide with rising edges of a waveform of the charging/discharging signal to thereby enable the detection circuit to distinguish a touch input being made by the electronic stylus from a touch input being made by a user'"'"'s finger.

24. A control method for a capacitive touchpad, the control method comprising:

providing a capacitive touchpad module having a plurality of traces formed thereon;

actively driving the plurality of traces with a charging/discharging signal;

providing a detection circuit connected to the plurality of traces for detecting the charging/discharging signal conducted by the plurality of traces;

detecting a decrease in an amplitude of the charging/discharging signal by the detection circuit for at least two of the plurality of traces disposed orthogonally with respect to one another and thereby identifying a touch input as being made by a user'"'"'s finger;

providing an electronic stylus;

generating an excitation signal having a fixed relationship with respect to a frequency of the charging/discharging signal, the excitation signal having a fixed phase relationship with the charging/discharging signal where a waveform of the excitation signal has rising edges that coincide with rising edges of a waveform of the charging/discharging signal;

supplying the excitation signal to a tip of the electronic stylus for emission therefrom; and

responsive to bringing the tip of the electronic stylus in proximity to the capacitive touchpad module, the emitted excitation signal being capacitively coupled to the capacitive touchpad module, detecting an increase in the amplitude of the charging/discharging signal by the detection circuit and for at least two of the plurality of traces disposed orthogonally with respect to one another in proximity to the tip of the electronic stylus and thereby identifying a touch input as being made by the electronic stylus;

wherein the touch input from either one of a user'"'"'s finger or the electronic stylus is detectable and distinguishable.

25. The method of claim 24, wherein the step of generating an excitation signal includes the step of generating the excitation signal having a frequency which is an integral multiple of the frequency of the charging/discharging signal.

26. The method of claim 24, wherein the step of generating an excitation signal includes the step of generating the excitation signal having a frequency equal to that of the charging/discharging signal and a duty ratio of 50%.

27. The method of claim 24, wherein the step of generating an excitation signal includes the step of generating the excitation signal having a frequency equal to one half of that of the charging/discharging signal and a duty ratio of 25%.

28. The method of claim 24, wherein the step of generating an excitation signal includes the step of generating the excitation signal having a frequency equal to one third of that of the charging/discharging signal and a duty ratio of 16.7%.

29. The method of claim 24, wherein the step of generating an excitation signal includes the step of generating the excitation signal having a frequency equal to one quarter of that of the charging/discharging signal and a duty ratio of 12.5%.