Touch screen device

• US 8,803,835 B2
• Filed: 11/26/2012
• Issued: 08/12/2014
• Est. Priority Date: 07/31/2012
• Status: Active Grant

• Current Assignee: FocalTech Systems Co.,Ltd
• Original Assignee: FocalTech Systems Co.,Ltd
• Inventors: Li, Chen, Mo, Lianghua, Zhang, Jingkai, Jiang, Xinxi, Xu, Huaiyi
• Primary Examiner(s): Liang, Regina
• Application Number:
  US13/684,936
• Publication Number:
  US 20140035863A1
• Time in Patent Office: 624 Days
• Field of Search: 345173-179, 178 1801- 1811, 178 1901- 1904
• US Class Current: 345/173
• CPC Class Codes: G06F 3/04162 for exchanging data with external devices, e.g. smart pens, via the digitiser sensing hardware
• 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

Abstract

It is provided a touch screen device applied in an electronic information technology area. In the touch screen device supporting an active capacitance stylus, a demodulation unit demodulates a signal received by a reception unit by two orthogonal signals, and then an amplitude recovery unit recovers an amplitude of the signal received by the reception unit, the amplitude of the signal received by the reception unit can be recovered relatively exactly without the need that the demodulation signal must be synchronous with the signal received by the reception unit (or the signal transmitted from the active capacitance stylus), and there is no need to add additional hardware resources for synchronization in the touch screen device of the embodiment of the present invention compared with the existing detection method which needs to perform synchronization of the demodulation signal and the signal transmitted from the active capacitance stylus in the prior art.

Claims

1. A touch screen device, comprising a reception unit, a signal processing unit and a mutual capacitor connected with the reception unit, the touch screen device further comprises a demodulation unit and an amplitude recovery unit;

the demodulation unit is connected with an output end of the reception unit for demodulating a signal received by the reception unit by two orthogonal signals;

an output end of the demodulation unit is connected with the amplitude recovery unit, the amplitude recovery unit is used for obtaining low pass portions of two demodulated signals demodulated by the demodulation unit, determining an amplitude of the signal received by the reception unit according to the amplitudes of the low pass portions of the two demodulated signals, and transmitting the determined amplitude of the signal to the signal processing unit.

2. The touch screen device according to claim 1, wherein the demodulation unit comprises a signal input unit and two multipliers, the amplitude recovery unit comprises a square sum calculator and two low pass filters, wherein

the signal input unit comprises two signal output ends, the two signal output ends are connected with an input end of a first multiplier and an input end of a second multiplier of the two multipliers respectively for outputting the two orthogonal signals;

the output end of the reception unit is connected with another input end of the first multiplier and another input end of the second multiplier, output ends of the first multiplier and the second multiplier are connected with input ends of the two low pass filters respectively;

output ends of the two low pass filters are connected with two input ends of the square sum calculator respectively;

an output end of the square sum calculator is connected with the signal processing unit.

3. The touch screen device according to claim 2, wherein the touch screen device further comprises a frequency detector;

the output ends of the two low pass filters are also connected with two input ends of the frequency detector respectively, an output end of the frequency detector is connected with a frequency control end of the signal input unit;

the frequency detector is used for outputting a frequency difference between a signal inputted by the signal input unit and the signal received by the reception unit;

the signal input unit is used for adjusting a frequency of the two output orthogonal signals according to the frequency difference received by the frequency control end, so as to make the two orthogonal signals and the signal received by the reception unit have a same frequency.

4. The touch screen device according to claim 3, wherein the signal input unit comprises a frequency control unit, a phase accumulator and two output units;

an output end of the frequency control unit is connected with an input end of the phase accumulator for controlling a frequency of a signal output by the phase accumulator;

an output end of the phase accumulator is connected with another input end of the phase accumulator by a feedback circuit, the output end of the phase accumulator is connected with the two output units for accumulating a frequency control value output by the frequency control unit under a drive of a clock signal inputted by a clock signal input end of the feedback circuit and outputting a triangular wave signal;

the two output units are used for converting the triangular wave signal into two orthogonal signals.

5. The touch screen device according to claim 4, wherein the frequency detector comprises a subtracter, a first delayer, a second delayer, a gain controller, a third multiplier and a fourth multiplier;

the output ends of the two low pass filters are connected with input ends of the first delayer and the second delayer respectively, output ends of the first delayer and the second delayer are connected with an input end of the fourth multiplier and an input end of the third multiplier respectively;

the output ends of the two low pass filters are connected with another input end of the third multiplier and another input end of the fourth multiplier respectively, output ends of the third multiplier and the fourth multiplier are connected with two input ends of the subtracter respectively;

an output end of the subtracter is connected with an input end of the gain controller, an output end of the gain controller is connected with an input end of the frequency control unit included in the signal input unit.

6. The touch screen device according to claim 2, further comprising a transmission unit, and the mutual capacitor is connected between the transmission unit and the reception unit.

7. The touch screen device according to claim 3, further comprising a transmission unit, and the mutual capacitor is connected between the transmission unit and the reception unit.

8. The touch screen device according to claim 4, further comprising a transmission unit, and the mutual capacitor is connected between the transmission unit and the reception unit.

9. The touch screen device according to claim 5, further comprising a transmission unit, and the mutual capacitor is connected between the transmission unit and the reception unit.

10. The touch screen device according to claim 1, wherein the demodulation unit comprises a multiplier and a signal input unit, the amplitude recovery unit comprises a square sum calculator, a delayer and a low pass filter, wherein:

an output end of the signal input unit is connected with an input end of the multiplier, the output end of the reception unit is connected with another input end of the multiplier, an output end of the multiplier is connected with an input end of the low pass filter;

an output end of the low pass filter is connected with an input end of the square sum calculator and an input end of the delayer;

the signal input unit is used for outputting two orthogonal signals in a time sharing manner;

an output end of the delayer is connected with another input end of the square sum calculator, an output of the square sum calculator is connected with the signal processing unit.

11. The touch screen device according to claim 10, further comprising a transmission unit, and the mutual capacitor is connected between the transmission unit and the reception unit.

12. The touch screen device according to claim 1, wherein the demodulation unit comprises a multiplier and a signal input unit, the amplitude recovery unit comprises a square sum calculator, a delayer and two low pass filters, wherein:

an output end of the signal input unit is connected with an input end of the multiplier, the output end of the reception unit is connected with another input end of the multiplier;

the signal input unit is used for outputting two orthogonal signals in a time sharing manner;

an output end of the multiplier is connected with an input end of one low pass filter and an input end of the delayer, an output end of the delayer is connected with an input end of another low pass filter, output ends of the two low pass filters are connected with two input ends of the square sum calculator respectively, an output of the square sum calculator is connected with the signal processing unit.

13. The touch screen device according to claim 12, further comprises a transmission unit, and the mutual capacitor is connected between the transmission unit and the reception unit.