Active stylus receiving circuit and touch panel system using active stylus

Abstract

A stylus receiving circuit receives a vector data signal emitted by a stylus, the vector data signal carrying vector data including in-phase data and quadrature data. The stylus receiving circuit includes an analog-to-digital converter, an interpolation circuit and a demodulation circuit. The analog-to-digital converter samples and converts the vector data signal into a digital signal having a plurality of samples. The interpolation circuit interpolates the digital signal to increase the number of samples representing the digital signal, thereby generating an interpolated digital signal. The demodulation circuit demodulates the interpolated digital signal to generate demodulated in-phase data and demodulated quadrature data, thereby obtaining demodulated vector data.

Description

Technical Field

[0001] This invention relates to the technical field of active pens, and more particularly to an active pen receiving circuit and a touch panel system using an active pen. Background Technology

[0002] Active styluses are widely used in electronic devices with touch panels to provide input. An active stylus contains a transmitting circuit that emits modulated vector data signals, which are received by the touch panel to detect the stylus's coordinates. To correctly receive and demodulate the vector data signals emitted by the active stylus, the touch panel is equipped with multiple sensors to sense these signals, and corresponding receiving circuits receive and demodulate these signals to obtain the vector data.

[0003] In the aforementioned process of modulation, transmission, reception, and demodulation of vector data, the active pen modulates the vector data using a carrier wave. The vector data includes in-phase data and quadrature data. The modulated vector data signal is transmitted by the active pen and received by the corresponding receiving circuit. The receiving circuit converts the received vector data signal into a digital signal using an analog-to-digital converter (ADC), and then demodulates this digital signal using in-phase and quadrature carrier waves respectively to demodulate the in-phase and quadrature data, thereby obtaining the original vector data.

[0004] In the operation of the aforementioned touch panel using an active pen, one of the main factors affecting the performance of the active pen is the data sampling rate of the analog-to-digital converter in the receiving circuit. Higher sampling data results in better noise immunity for the active pen, while lower sampling data makes it more susceptible to noise interference. Therefore, under limited sampling rates of the analog-to-digital converter, a significant amount of hardware space is often required to meet the specifications of an active pen, which is insufficient for practical needs.

[0005] Therefore, there are still many shortcomings in the design of the existing active pen receiver circuit, which need to be improved. Summary of the Invention

[0006] The main purpose of this invention is to provide an active pen receiving circuit and a touch panel system using an active pen. By using active pen interpolation technology, the performance of the active pen can be effectively improved, the ability to resist interference and noise can be increased, and the area of ​​the front-end analog circuit can be reduced.

[0007] According to one aspect of the present invention, an active pen receiving circuit is provided for receiving a vector data signal emitted by an active pen, the vector data signal carrying vector data including in-phase data and quadrature data. The active pen receiving circuit includes: an analog-to-digital converter for sampling the vector data signal and converting it into a digital signal having a plurality of sampling points; an interpolation circuit for performing interpolation operations on the digital signal to increase the number of sampling points representing the digital signal, thereby generating an interpolated digital signal; and a demodulation circuit for demodulating the interpolated digital signal to generate demodulated in-phase data and demodulated quadrature data, thereby obtaining demodulated vector data.

[0008] According to another aspect of the present invention, a touch panel system is provided, comprising: an active pen that emits a vector data signal carrying vector data, wherein the vector data includes in-phase data and quadrature data; a touch panel having a plurality of sensors for sensing the vector data signal emitted by the active pen; and a receiving device having a plurality of active pen receiving circuits, each active pen receiving circuit corresponding to at least one sensor, and comprising: an analog-to-digital converter that samples the vector data signal and converts it into a digital signal having a plurality of sampling points; an interpolation circuit that performs interpolation operations on the digital signal to increase the number of sampling points representing the digital signal, thereby generating an interpolated digital signal; and a demodulation circuit that demodulates the interpolated digital signal to generate demodulated in-phase data and demodulated quadrature data, thereby obtaining demodulated vector data.

[0009] The above overview and the following detailed description are illustrative in nature and are intended to further illustrate the technical solution of the present invention. Other objects and advantages of the present invention will be explained in the following description and drawings. Attached Figure Description

[0010] Figure 1 This invention demonstrates a touch panel system using an active pen according to the present invention.

[0011] Figure 2 This diagram shows the vector data signal emitted by the active pen.

[0012] Figure 3 This is a schematic diagram of the active pen receiving circuit.

[0013] Figure 4 This is a schematic diagram of the digital signal after the demodulation transformer interpolation point in the demodulation transformer circuit.

[0014] Symbol explanation:

[0015] Active pen 10, nib 11

[0016] Pen Ring 13 Touch Panel 20

[0017] Receiver 30 Active pen receiver circuit 31

[0018] Sensor Sx Microcontroller 50

[0019] Integrated Circuit 60 Analog-to-Digital Converter 311

[0020] Interpolation circuit 313, demodulation circuit 315

[0021] Sampling points 35, 351, 352 Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of implementation methods and are not intended to limit the scope of the invention.

[0023] Figure 1 The diagram illustrates a touch panel system using an active pen according to the present invention. It includes an active pen 10, a touch panel 20, and a receiving device 30. The receiving device 30 is housed in an integrated circuit (IC) 60, which further includes a microcontroller (MCU) 50. The active pen 10 has a tip 11 and a ring 13, and can emit vector data signals at a transmission frequency fin. The touch panel 20 has a plurality of sensors Sx that can sense the vector data signals emitted by the tip 11 or ring 13 of the active pen 10. The receiving device 30 has a plurality of active pen receiving circuits 31 that receive and process the vector data signals X(t) to obtain the vector data emitted by the active pen. It is worth noting that the touch panel 20 in this embodiment can be an in-cell touch display panel, a stand-alone touch panel, or other electronic devices with similar functions as described in this application.

[0024] Figure 2 The diagram shows the vector data signal X(t) transmitted by the aforementioned active pen 10. As shown in the figure, the aforementioned active pen 10 modulates the vector data x(t) with a carrier signal cos(ωt) + sin(ωt) having an in-phase modulated carrier signal cos(ωt) and a quadrature modulated carrier signal sin(ωt), so that the vector data signal X(t) carries the vector data x(t), wherein the vector data x(t) includes in-phase data xi(t) and quadrature data xq(t). The modulated vector data signal X(t) = xi(t) × cos(ωt) + xq(t) sin(ωt) is emitted by the pen tip 11 or pen ring 13 of the active pen 10.

[0025] Please refer to the above as well. Figure 1 and Figure 2 The aforementioned touch panel 20's sensor Sx can sense the vector data signal X(t) emitted by the pen tip 11 or pen ring 13 of the active pen 10, and receive it by the corresponding active pen receiving circuit 31 of the receiving device 30. Each active pen receiving circuit 31 corresponds to at least one sensor Sx, and an active pen receiving circuit 31 can receive the vector data signal X(t) sensed by a plurality of sensors Sx in a multitasking manner.

[0026] Figure 3 The above-mentioned active pen receiving circuit 31 is shown in the figure. Each active pen receiving circuit 31 has an analog-to-digital converter (ADC) 311, an interpolation circuit 313 and a demodulation circuit 315. The ADC 311 samples the received vector data signal X(t) at a sampling frequency fs and converts it into an n-bit digital signal X(n) = xi(n) × cos((2π × n × fin) / fs) + xq(n) × sin((2π × n × fin) / fs), where fs is the sampling frequency of the ADC 311, fin is the transmission frequency of the active pen 10 transmitting the vector data signal X(t), and the digital signal obtained by the sampling conversion has a plurality of sampling points 35.

[0027] To improve the performance of the active pen 10, enhance its anti-interference and anti-noise capabilities, and reduce circuit area, the active pen receiving circuit 31 incorporates an interpolation circuit 313 to perform interpolation operations on the aforementioned digital signal X(n), thereby increasing the number of sampling points 35 representing the digital signal X(n). Figure 3 As shown, the sampling points 351 originally representing the digital signal X(n) are represented by solid circles. Since the distribution of these solid circle sampling points 351 is relatively sparse, it may not be sufficient to completely represent the vector data signal X(t). Therefore, the interpolation circuit 313 performs interpolation operations on the digital signal X(n) to insert sampling points 352, represented by hollow circles, through the interpolation circuit operation between the solid circle sampling points 351. This makes the overall distribution of sampling points 35 denser, thus enabling it to completely represent the vector data signal X(t). In one embodiment of the present invention, the interpolated digital signal generated by the interpolation circuit 313 performing interpolation operations on the digital signal X(n) can be expressed as:

[0028]

[0029] Where Y() represents the digital signal after interpolation, X() represents the digital signal output by the digital converter 311, and floor() represents the floor function. For example, Y(1) = X(1), Y(2) = (X(1) + X(2)) / 2, Y(3) = X(2), Y(4) = (X(3) + X(4)) / 2, and so on.

[0030] The aforementioned interpolation circuit 313 can use any interpolation operation technique to interpolate the digital signal X(n), such as the two-point interpolation method described in the previous embodiment. However, the present invention is not limited to this. The interpolation operation used by the interpolation circuit 313 can also be a polynomial interpolation method or a original value interpolation method, etc. The implementation methods are known to those skilled in the art, so they will not be described in detail here.

[0031] Please refer to the following: Figure 3 As shown, the digital signal Y(m) after interpolation is demodulated by demodulation circuit 315 to generate demodulated vector data x_rx. Figure 4 The diagram shows the demodulation circuit 315 demodulating the previously interpolated digital signal Y(m). The demodulation circuit 315 demodulates the interpolated digital signal Y(m) using an in-phase modulated carrier signal cos(ωt) to generate demodulated in-phase data xi_rx, and uses a quadrature modulated carrier signal sin(ωt) to demodulate the interpolated digital signal Y(m) to generate demodulated quadrature data xq_rx. Based on this, the demodulated vector data x_rx = xi_rx + xq_rx is obtained and transmitted to... Figure 1 The microcontroller 50 shown performs calculations to obtain active pen coordinate data.

[0032] Therefore, it can be seen that the present invention can perform interpolation operations on the digital signal output by the analog-to-digital converter using an interpolation circuit, thereby increasing the number of sampling points representing the digital signal and being able to completely represent the vector data signal, thus effectively improving the performance of the active pen, increasing the anti-interference and anti-noise capabilities, and reducing the circuit area.

[0033] The above embodiments are merely illustrative examples for ease of explanation. The scope of the claims made in this invention should be determined by the claims themselves, and not limited to the above embodiments.

Claims

1. An active pen receiving circuit for receiving a vector data signal emitted by an active pen, the vector data signal carrying vector data, the vector data including in-phase data and quadrature data, the active pen receiving circuit comprising: An analog-to-digital converter samples the vector data signal and converts it into a digital signal with multiple sampling points; An interpolation circuit performs interpolation operations on the digital signal to increase the number of sampling points representing the digital signal, generating an interpolated digital signal; and A demodulation circuit demodulates the digital signal after the interpolation point to generate demodulated in-phase data and demodulated quadrature data, thereby obtaining the demodulated vector data. The interpolation circuit performs interpolation operations on the digital signal using a two-point interpolation method. The interpolated digital signal generated by the interpolation circuit is: ， In this context, Y() represents the digital signal after interpolation, X() represents the digital signal output by the digital converter, and floor() represents the floor function.

2. The active pen receiving circuit as described in claim 1, characterized in that, The vector data signal is: xi(t)cos(πωt)+xq(t)sin(ωt), where xi(t) represents in-phase data, xq(t) represents quadrature data, cos(ωt) represents in-phase modulated carrier signal, and sin(ωt) represents quadrature modulated carrier signal.

3. The active pen receiving circuit as described in claim 2, characterized in that, The digital signal obtained by sampling and converting the vector data signal by the digital converter is: xi(n)×cos((2π×n×fin) / fs)+ xq(n)×sin((2π×n×fin) / fs), where fs is the sampling frequency of the analog-to-digital converter and fin is the transmission frequency of the vector data signal transmitted by the active pen.

4. The active pen receiving circuit as described in claim 1, characterized in that, The demodulation circuit uses an in-phase modulated carrier signal to demodulate the digital signal after the interpolation point to generate in-phase data, and uses a quadrature modulated carrier signal to demodulate the digital signal after the interpolation point to generate quadrature data. The demodulated vector data is obtained as: xi_rx + xq_rx, where xi_rx represents the in-phase data after demodulation and xq_rx represents the quadrature data after demodulation.

5. A touch panel system, characterized in that, include: An active pen emits a vector data signal carrying vector data, wherein the vector data includes in-phase data and quadrature data; A touch panel with multiple sensors to sense the vector data signal emitted by the active pen; and A receiving device having a plurality of active pen receiving circuits, each active pen receiving circuit corresponding to at least one sensor, and comprising: An analog-to-digital converter samples the vector data signal and converts it into a digital signal with multiple sampling points; An interpolation circuit performs interpolation operations on the digital signal to increase the number of sampling points representing the digital signal, thereby generating an interpolated digital signal; and A demodulation circuit demodulates the digital signal after the interpolation point to generate demodulated in-phase data and demodulated quadrature data, thereby obtaining the demodulated vector data. The interpolation circuit performs interpolation operations on the digital signal using a two-point interpolation method. The interpolated digital signal generated by the interpolation circuit is: ， In this context, Y() represents the digital signal after interpolation, X() represents the digital signal output by the digital converter, and floor() represents the floor function.

6. The touch panel system as described in claim 5, characterized in that, The active pen modulates the vector data with a carrier signal to generate the vector data signal as: xi(t)cos(πωt) + xq(t)sin(ωt), where xi(t) represents in-phase data, xq(t) represents quadrature data, cos(ωt) represents in-phase modulated carrier signal, and sin(ωt) represents quadrature modulated carrier signal.

7. The touch panel system as described in claim 6, characterized in that, The digital signal obtained by sampling and converting the vector data signal by the digital converter is: xi(n)×cos((2π×n×fin) / fs) + xq(n)×sin((2π×n×fin) / fs), where fs is the sampling frequency of the analog-to-digital converter and fin is the transmission frequency of the vector data signal transmitted by the active pen.

8. The touch panel system as described in claim 5, characterized in that, The demodulation circuit uses an in-phase modulated carrier signal to demodulate the digital signal after the interpolation point to generate in-phase data, and uses a quadrature modulated carrier signal to demodulate the digital signal after the interpolation point to generate quadrature data. The demodulated vector data is obtained as: xi_rx + xq_rx, where xi_rx represents the in-phase data after demodulation and xq_rx represents the quadrature data after demodulation.

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