Noise spectrum estimator and touch screen device including the same

• US 9,146,630 B2
• Filed: 12/18/2012
• Issued: 09/29/2015
• Est. Priority Date: 02/28/2012
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lee, Chang-Ju, Choi, Kwang-Ho
• Primary Examiner(s): Amadiz, Rodney
• Application Number:
  US13/717,955
• Publication Number:
  US 20130222290A1
• Time in Patent Office: 1,015 Days
• Field of Search: 345173-178, 178 1801- 1811
• US Class Current: 1/1
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/04184 Synchronisation with the driving of the display or the backlighting unit to avoid interferences generated internally
• 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 noise spectrum estimator for a touch panel includes an adaptive impulse response generation unit configured to generate impulse response information by performing an adaptive training operation on noise data, the noise data being generated by sampling a plurality of noise signals received from the touch panel, and an estimation unit configured to generate noise frequency spectrum estimation information associated with the noise data by performing a fast Fourier transform (FFT) on the impulse response information.

Claims

1. A noise spectrum estimator for a touch panel, comprising:

an adaptive impulse response generator to generate impulse response information by performing an adaptive training operation on noise data, the noise data being generated by sampling a plurality of noise signals received from the touch panel; and

an estimator to generate noise frequency spectrum estimation information associated with the noise data by performing a fast Fourier transform (FFT) on the impulse response information, wherein

first peak frequencies corresponding to first noise peak points are substantially equal to second peak frequencies corresponding to second noise peak points, the first noise peak points being detected based on the noise frequency spectrum estimation information, the second noise peak points being obtained by directly performing the FFT on the noise data.

2. The noise spectrum estimator as claimed in claim 1, further comprising:

a peak detector to detect the first peak frequencies by analyzing the noise frequency spectrum estimation information.

3. The noise spectrum estimator as claimed in claim 1, wherein the adaptive impulse response generator includes an adaptive line enhancer filter.

4. The noise spectrum estimator as claimed in claim 3, wherein the adaptive line enhancer filter includes:

a delay to generate delayed noise data by delaying the noise data;

a calculator to generate second estimated noise data by subtracting first estimated noise data from the noise data; and

an adaptive filter to generate the impulse response information and the first estimated noise data by performing the adaptive training operation based on the delayed noise data and the second estimated noise data.

5. The noise spectrum estimator as claimed in claim 4, wherein a tab coefficient of the adaptive filter is substantially equal to a number of FFT points for the FFT performed by the estimator.

6. A touch screen device, comprising:

a touch panel including a plurality of panel points for sensing respective input touch events;

a signal processor to generate voltage data based on a plurality of sensing signals corresponding to changes of capacitances of the touch panel;

a noise spectrum estimator to generate noise frequency spectrum estimation information based on the voltage data in a noise sensing mode, the voltage data including noise data in the noise sensing mode;

a filter unit including a plurality of filters, the filter unit to select from among the plurality of filters based on a filter selection signal and generate filtered data by filtering the voltage data based on a selected filter in a touch sensing mode; and

a touch panel controller to generate the filter selection signal by analyzing the noise frequency spectrum estimation information in the noise sensing mode, and to provide a driving signal to the touch panel and determine a touch point among the panel points based on the filtered data in the touch sensing mode, wherein the noise spectrum estimator includes;

an adaptive impulse response generator to generate impulse response information by performing an adaptive training operation on the noise data in the noise sensing mode, the noise data being generated by sampling a plurality of noise signals received from the touch panel; and

an estimator to generate the noise frequency spectrum estimation information by performing a fast Fourier transform (FFT) on the impulse response information in the noise sensing mode, wherein

the filter unit includes an averaging filter and a frequency filter, the filter unit selecting the averaging filter based on the filter selection signal when the noise frequency spectrum estimation information corresponds to uniform distribution, and the filter unit selecting the frequency filter based on the filter selection signal when the noise frequency spectrum estimation information corresponds to nonuniform distribution.

7. The touch screen device as claimed in claim 6, wherein the frequency filter includes a filter selected from a finite impulse response (FIR) filter and an infinite impulse response (IIR) filter.

8. The touch screen device as claimed in claim 6, wherein the touch panel controller detects peak frequencies corresponding to noise peak points by analyzing the noise frequency spectrum estimation information in the noise sensing mode, and determines a frequency of the driving signal except the detected peak frequencies.

9. The touch screen device as claimed in claim 6, wherein the touch panel controller generates a mode selection signal to determine an operation mode of the touch screen device.

10. The touch screen device as claimed in claim 9, wherein the touch panel controller determines whether the filtered data correspond to noises in the touch sensing mode, the touch panel controller changing the operation mode of the touch screen device from the touch sensing mode to the noise sensing mode based on the mode selection signal when the filtered data correspond to the noises, and the touch panel controller determining the touch point among the panel points based on the filtered data when the filtered data do not correspond to the noises.

11. The touch screen device as claimed in claim 6, wherein the signal processor includes:

a capacitive-to-voltage converter to generate a plurality of first voltage signals based on the plurality of sensing signals;

an anti-aliasing filter to generate a plurality of second voltage signals based on the plurality of first voltage signals; and

an analog-to-digital converter to generate the voltage data based on the plurality of second voltage signals.

12. The touch screen device as claimed in claim 11, wherein the analog-to-digital converter generates a third voltage signal by adding up at least two of the plurality of second voltage signals and generates the voltage data by performing an analog-to-digital conversion operation on the third voltage signal.

13. The touch screen device as claimed in claim 6, further comprising:

a display panel formed under the touch panel; and

a display driver to control the display panel to display an image on the display panel.

14. A touch screen device having a panel to respond to a touch input, the panel having a touch sensor array, the device comprising:

a plurality of sensors in the touch sensor array, each sensor providing a respective voltage signal in response to a touch input thereto; and

a noise spectrum estimator to receive voltage data from the respective voltage signals from the sensors, the noise spectrum estimator including;

an adaptive impulse response generator to generate impulse response information by performing an adaptive training operation on noise data of the voltage data, the noise data being generated by sampling a plurality of noise signals received from the sensors of the touch panel, the adaptive training operation including generating delayed noise data by delaying the noise data, generating first estimated noise data, and generating second estimated noise data by using the noise data and the first estimated noise data; and

an estimator to generate noise frequency spectrum estimation information associated with the noise data by performing a fast Fourier transform (FFT) on the impulse response information, wherein

the adaptive training operation is performed based on the delayed noise data and the second estimated noise data.

15. The device as claimed in claim 14, wherein the voltage data is derived from a change in capacitance in the sensors.

16. The device as claimed in claim 14, wherein at least one filter is applied to the voltage data so as to generate a signal indicative of an actual touch input, the at least one filter being selected from a group of one or more filters based on the noise frequency spectrum estimation information.

17. The device as claimed in claim 16, wherein the signal indicative of an actual touch input is used to generate a touch event in a microprocessor of the device.

18. The device as claimed in claim 14, wherein estimating the periodic noise component of the noise data using the adaptive filter includes processing the noise data using a finite impulse response filter.

19. The device as claimed in claim 14, wherein:

the first estimated noise data corresponds to a dominant noise component or a periodic noise component of the noise data, and

the second estimated noise data corresponds to a non-dominant noise component or a random noise component of the noise data.