Noise suppression method for stylus and mobile device
By introducing a noise suppression circuit into the stylus system and utilizing signal comparison and adjustment techniques, the problem of limited noise suppression effect was solved, resulting in reduced noise energy and improved signal-to-noise ratio, thus enhancing the signal quality of the stylus system.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- FOCALTECH ELECTRONICS LTD
- Filing Date
- 2023-10-25
- Publication Date
- 2026-05-12
AI Technical Summary
In existing stylus systems, noise suppression is limited by the sampling rate, leading to problems such as high frequency noise reflection probability and excessively high white noise levels, especially with poor noise suppression before downsampling.
A noise suppression circuit is employed, which compares the sampled signal with the sampled signal at a nearby time and determines whether to output or adjust the signal based on the difference. This circuit includes a charge amplifier, an analog-to-digital converter, a pre-buffer, a post-buffer, a digital comparator circuit, an addition/subtraction circuit, and a multi-task selection circuit, ensuring that the signal remains within the allowable variation range under the influence of noise.
It effectively reduces noise energy, improves the signal-to-noise ratio, ensures that the signal remains stable under the influence of noise, and improves the signal quality of the stylus system.
Smart Images
Figure CN119883010B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a wireless sensing technology, and more particularly to a method for noise suppression of a stylus and a mobile device with a stylus using the same. Background Technology
[0002] A stylus is an input device for mobile devices or tablets. It resembles a traditional pen or pencil but has a special design for interacting with touchscreens. Styluses typically have a pointed tip, allowing users to precisely tap, draw, write, or manipulate the screen without using their fingers.
[0003] The design and functionality of a stylus can vary from device to device, but generally, a stylus works by using capacitive touch technology in conjunction with modulated digital signals. These signals contain information about the pen's position, pressure, and tilt angle. Once the stylus signal is transmitted to the mobile device, the device's touch controller decodes it. The touch controller identifies the pen's position, movement, and other relevant information, then converts it into data that the application can understand.
[0004] Figure 1 This is a circuit diagram of the decoding circuit for a current stylus system. Please refer to it. Figure 1 The decoding circuit of this stylus system includes a stylus 101 and a stylus receiver 102. The stylus 101 is the signal transmitter, and the stylus receiver 102 is the receiver. The stylus 101 (transmitter) transmits data after phase-shift modulation (PSK modulation) and carrier modulation. The stylus receiver 102 (receiver) samples the data via an ADC and then demodulates it in the digital system. However, there are many noise sources in the environment. If the sampling frequency is not high enough, it will increase the probability of various high-frequency noise reflections and cause excessively high levels of (white) noise. Although a filter (IIR or FIR filter) can be used at the receiver after digital demodulation to filter out noise and improve performance, the filter bandwidth is related to the number of sampling points. With a low sampling rate, the filter's effectiveness will be greatly reduced. Summary of the Invention
[0005] The present invention provides a noise suppression method for a stylus and a mobile device having a stylus, for suppressing and inhibiting noise in the sampled stylus signal before downsampling.
[0006] An embodiment of the present invention provides a mobile device including a stylus and a display touch device. The stylus is used to emit a stylus signal. The display touch device includes a plurality of touch electrodes, a plurality of signal sampling devices, and a plurality of noise suppression circuits. Each signal sampling device includes an input terminal and an output terminal, wherein the input terminals of the plurality of signal sampling devices are respectively coupled to the plurality of touch electrodes. Each noise suppression circuit includes an input terminal and an output terminal, wherein the input terminals of the plurality of noise suppression circuits are respectively coupled to the output terminals of the plurality of signal sampling devices.
[0007] One of the aforementioned noise suppression circuits, a specific noise suppression circuit, is used to compare the sampled signal from the corresponding signal sampling device with a sampled signal from a nearby time period. When the difference between the sampled signal and the nearby time period is greater than a signal tolerance value, the specific noise suppression circuit outputs the sampled signal as a first noise suppression signal as an output signal. When the difference between the sampled signal and the nearby time period is less than a signal tolerance value, the specific noise suppression circuit outputs a second noise suppression signal as the output signal, wherein the value of the second noise suppression signal is between the sampled signal and the nearby time period.
[0008] According to a preferred embodiment of the mobile device of the present invention, each of the signal sampling devices further includes a charge amplifier and an analog-to-digital converter. The charge amplifier includes an input terminal and an output terminal, wherein the input terminal of the charge amplifier is coupled to the input terminal of the signal sampling device, and the charge amplifier is used to receive the signal from the coupled touch electrode to output an amplified touch signal. The analog-to-digital converter includes an input terminal and an output terminal, wherein the input terminal of the analog-to-digital converter is coupled to the output terminal of the charge amplifier to receive the amplified touch signal, and the output terminal of the analog-to-digital converter is coupled to the output terminal of the signal sampling device to output a sampled signal corresponding to the signal sampling device.
[0009] According to a preferred embodiment of the mobile device of the present invention, each of the noise suppression circuits further includes a pre-buffer, a post-buffer, a digital comparator circuit, an addition / subtraction circuit, and a multitasking selection circuit. The pre-buffer receives and temporarily stores the sampled signal corresponding to the signal sampling device. The post-buffer stores the previously output sampled signal and outputs the output signal. A first input port of the digital comparator circuit is coupled to the pre-buffer to receive the sampled signal corresponding to the signal sampling device, a second input port of the digital comparator circuit is coupled to the post-buffer, and the output of the digital comparator circuit outputs a selection signal. The logic of the selection signal is determined by the digital comparator circuit based on the difference between the input values of the first input port and the second input port of the digital comparator circuit.
[0010] The first input port of the addition / subtraction circuit is coupled to the post-buffer to receive the previously output sampled signal. The second input port of the addition / subtraction circuit receives a variation tolerance value, and its output terminal outputs a second noise suppression signal. The first input port of the multitasking selection circuit is coupled to the pre-buffer to receive the sampled signal corresponding to the signal sampling device. The second input port of the multitasking selection circuit is coupled to the output port of the addition / subtraction circuit to receive the second noise suppression signal. The selection terminal of the multitasking selection circuit is coupled to the output terminal of the digital comparator circuit to receive the selection signal. The output port of the multitasking selection circuit determines, based on the logic of the selection signal, whether to output the data from the first input port of the multitasking selection circuit or the data from the second input port of the multitasking selection circuit.
[0011] According to a preferred embodiment of the present invention, the input port of the post-buffer is coupled to the output port of the multitasking selection circuit to receive data output by the output port of the multitasking selection circuit as the previously output sampling signal. The output port of the post-buffer outputs the first noise suppression signal or the second noise suppression signal based on the temporarily stored data.
[0012] According to a preferred embodiment of the mobile device of the present invention, the aforementioned pre-buffer further includes a storage block coupled to the output port of the post-buffer for storing data output by the output port of the post-buffer as a second previously output sampling signal. Each noise suppression circuit further includes a second multitasking selection circuit. The first input port of the second multitasking selection circuit is coupled to the storage block of the pre-buffer to receive the second previously output sampling signal. The second input port of the second multitasking selection circuit is coupled to the output port of the post-buffer to receive the data output by the output port of the post-buffer. The selection terminal of the multitasking selection circuit receives a delay selection signal. The output port of the second multitasking selection circuit is coupled to the second input port of the multitasking selection circuit and the second input port of the digital comparator circuit.
[0013] An embodiment of the present invention further provides a noise suppression method for a stylus. This noise suppression method includes: sampling a signal received by a touch sensing electrode as a sampled signal; comparing the sampled signal with a sampled signal from a nearby time period; outputting a first noise suppression signal when the difference between the sampled signal and the sampled signal from the nearby time period is greater than a signal tolerance value, wherein the first noise suppression signal is equal to the sampled signal; and outputting a second noise suppression signal when the difference between the sampled signal and the sampled signal from the nearby time period is less than the signal tolerance value, wherein the value of the second noise suppression signal is between the sampled signal and the sampled signal from the nearby time period.
[0014] In summary, embodiments of the present invention sample the received signal and compare it with a previously sampled signal. The system determines whether the currently sampled signal has changed based on whether the comparison result is greater than a signal tolerance value. If the comparison result is greater than the signal tolerance value, the currently sampled signal is directly output. If the comparison result is less than the signal tolerance value, a change tolerance value is added to or subtracted from the previously sampled signal to obtain the output signal. This ensures that the processed signal, even under noise conditions, maintains its variation within the aforementioned change tolerance value, and only outputs the currently sampled signal when a real change occurs. This reduces the magnitude of various noise energies and increases the signal-to-noise ratio.
[0015] To further understand the technology, means, and effects of the present invention, reference can be made to the following detailed description and accompanying drawings, which will provide a thorough and concrete understanding of the purpose, features, and concepts of the present invention. However, the following detailed description and accompanying drawings are for reference and illustration only and are not intended to limit the present invention. Attached Figure Description
[0016] The accompanying drawings are provided to enable those skilled in the art to further understand the invention, and are incorporated in and constitute a part of the specification of the invention. The drawings illustrate exemplary embodiments of the invention and are used together with the specification to explain the principles of the invention.
[0017] Figure 1 This is a circuit diagram of the decoding circuit of a current stylus system.
[0018] Figure 2 The diagram illustrates a circuit diagram of a decoding circuit for a mobile device using a stylus, according to a preferred embodiment of the present invention.
[0019] Figure 3 The diagram illustrates an ideal scenario of a signal sampled by a signal sampling device 204 of a stylus-based mobile device according to a preferred embodiment of the present invention.
[0020] Figure 4 The illustration shows a schematic diagram of the actual signal sampled by the signal sampling device 204 of a mobile device using a stylus according to a preferred embodiment of the present invention.
[0021] Figure 5 The diagram shows a block diagram of a noise suppression circuit according to a preferred embodiment of the present invention.
[0022] Figure 6 The diagram illustrates the signal output by a noise suppression circuit according to a preferred embodiment of the present invention.
[0023] Figure 7 The diagram shows a block diagram of a noise suppression circuit according to a preferred embodiment of the present invention.
[0024] Figure 8 The flowchart illustrates a preferred embodiment of a noise suppression method for a stylus according to the present invention.
[0025] Symbol explanation:
[0026] 101: Stylus
[0027] 102: Stylus receiver
[0028] 201: Stylus
[0029] 202: Mobile Device
[0030] 203: Touch electrode
[0031] 204: Signal sampling device
[0032] 205: Noise Suppression Circuit
[0033] 206: Charge Amplifier
[0034] 207: Analog-to-digital converter
[0035] 501: Pre-buffer
[0036] 502: Post buffer
[0037] 503: Digital Comparator Circuit
[0038] 504: Addition and Subtraction Circuit
[0039] 505: Multitasking Selection Circuit
[0040] A[n]: The sampled signal from the signal sampling device
[0041] B[n-1]: The sampled signal from the previous time step.
[0042] VAR: Allowable Value for Change
[0043] 601, 602, 603: Sampling signals with reduced variation after processing by noise suppression circuitry.
[0044] S800~S804: Flow steps of a noise suppression method for a stylus according to a preferred embodiment of the present invention Detailed Implementation
[0045] Reference will now be made in detail to exemplary embodiments of the invention, which are illustrated in the accompanying drawings. Where possible, the same component reference numerals are used in the drawings and description to refer to the same or similar parts. Furthermore, the exemplary embodiments are merely one way of implementing the design concept of the invention, and the following examples are not intended to limit the invention.
[0046] Figure 2 The diagram illustrates a circuit block diagram of a decoding circuit for a stylus-based mobile device according to a preferred embodiment of the present invention. Please refer to... Figure 2 In an embodiment of the decoding circuit for a mobile device using a stylus, a stylus 201 and a mobile device 202 are included. The decoding circuit is disposed in the mobile device 202 and includes a plurality of touch electrodes 203, a plurality of signal sampling devices 204, and a plurality of noise suppression circuits 205. Each of the signal sampling devices 204 includes a charge amplifier (CA) 206 and a plurality of analog-to-digital converters (ADCs) 207.
[0047] Figure 3 The illustration shows a signal sampling device 204 of a stylus-based mobile device according to a preferred embodiment of the present invention, under ideal conditions. Please refer to... Figure 3 ,Depend on Figure 3As can be seen, ideally, the signal received by the touch electrode 203 from the stylus 201 should be a perfect square wave after passing through the analog-to-digital converter. Therefore, ideally, only two values will be obtained during sampling.
[0048] Figure 4 The illustration shows a signal sampling device 204 of a stylus-based mobile device according to a preferred embodiment of the present invention, under conditions of signal interference. Please refer to... Figure 4 ,Depend on Figure 4 As can be seen, in actual signal transmission, the signal received by the stylus 201 from the touch electrode 203 will become a signal with other high and low fluctuations after being received and converted from a perfect square wave containing only two values due to high frequency noise, aliasing effect and white noise.
[0049] Figure 5 The diagram illustrates a circuit block diagram of a noise suppression circuit 205 according to a preferred embodiment of the present invention. Please refer to... Figure 5 The noise suppression circuit 205 includes a pre-buffer 501, a post-buffer 502, a digital comparator circuit 503, an addition / subtraction circuit 504, and a multi-task selection circuit 505. The pre-buffer 501 receives and temporarily stores the sampled signal A[n] from the corresponding signal sampling device. The post-buffer 502 stores the previously output and processed sampled signal B[n-1].
[0050] In this embodiment, the digital comparator circuit 503 receives the sampled signal A[n] stored in the pre-buffer 501 and the sampled signal B[n-1] stored in the post-buffer 502 from the previous time, and compares the two. When the difference between the sampled signal A[n] and the sampled signal B[n-1] is large enough to exceed a set signal tolerance value, it indicates that the signal transition occurs from sampling time n-1 to sampling time n. At this time, the selection signal SEL_1 output by the digital comparator circuit 503 is set to logic 1. The sampled signal A[n] input to the input terminal of the multi-task selection circuit 505 corresponding to logic 1 will be fed into the output terminal of the multi-task selection circuit 505. Therefore, the post-buffer 502 will treat the received sampled signal A[n] as the output signal B[n] for the next time, that is, A[n] = B[n].
[0051] However, when the difference between the sampling signal A[n] and the sampling signal B[n-1] is insufficient and does not exceed a set signal tolerance value, it indicates that the signal difference from the sampling time n-1 to the sampling time n may be affected by interference and change. At this time, the selection signal SEL_1 output by the digital comparison circuit 503 will be set to logic 0. At this time, the signal input to the corresponding logic 0 input terminal of the multiplexer 505 will be introduced to the output terminal of the multiplexer 505. Since the signal input to the corresponding logic 0 input terminal of the multiplexer 505 is calculated by the addition and subtraction circuit 504. In this embodiment, the output of the addition and subtraction circuit 504 can be regarded as B[n-1]+VAR, where VAR represents the tolerance value of change in this embodiment. That is to say, although there is actually a difference between the sampling signal A[n] and the sampling signal B[n-1], this difference is considered to be possibly noise. Therefore, in this embodiment, only this signal is allowed to change partially within the limit of the tolerance value of change VAR. The rule of the above tolerance value of change VAR is that when A[n]>B[n-1], B[n]=B[n-1]+VAR, and when A[n]<B[n-1], B[n]=B[n-1]-VAR. After that, the post buffer 502 will take the received sampling signal B[n-1]+VAR or B[n-1]-VAR as the output signal B[n] for the next time.
[0052] Figure 6 It is a schematic diagram of the signal output by the noise suppression circuit 205 according to a preferred embodiment of the present invention. Please refer to Figure 6 , those of ordinary skill in the art should be able to see that after the reference numerals 601, 602, and 603 are processed by the noise suppression circuit 205, the amount of change is greatly reduced. Thereby, the influence of noise is also suppressed, making the output signal closer to the ideal.
[0053] Figure 7 It is a block diagram of the noise suppression circuit 205 according to a preferred embodiment of the present invention. Please refer to Figure 7In addition to the aforementioned pre-buffer 501, post-buffer 502, digital comparator circuit 503, addition / subtraction circuit 504, and multitasking selection circuit 505, the noise suppression circuit 205 also includes a second multitasking selection circuit 701. Furthermore, the pre-buffer 501 includes an additional storage block 702, coupled to the output port of the post-buffer, for storing the data B[n-2] output by the post-buffer's output port. The first input port of the second multitasking selection circuit 701 is coupled to the storage block 702 of the pre-buffer 501, receiving the previously output sampling signal B[n-2]. The second input port of the second multitasking selection circuit 701 is coupled to the output port of the post-buffer 502, receiving the data B[n-1] output by the post-buffer's output port. The selection terminal of the second multitasking selection circuit 701 receives a delay selection signal SEL_2. The delay selection signal SEL_2 is used to determine whether the sampling signal received by the digital comparator circuit 503 is a sampling signal B[n-1] delayed by one unit time or a sampling signal B[n-2] delayed by two unit times.
[0054] In a preferred embodiment of the present invention, when the sampling rate is sufficiently high, comparing the current sampled signal A[n] with a signal B[n-1] delayed by one unit time or with a signal B[n-2] delayed by two unit time will not affect the operation of the present invention. Therefore, users can choose to compare signals with different delays of different unit times to obtain better results according to different implementation environments. The present invention is not limited thereto.
[0055] The above embodiments can be summarized into a method for noise suppression of a stylus. Figure 8 The flowchart illustrates a preferred embodiment of a noise suppression method for a stylus according to the present invention. Please refer to... Figure 8 The noise suppression method for this stylus includes the following steps:
[0056] Step S800: Start.
[0057] Step S801: Sample the signal received by a touch sensing electrode as a sampling signal A[n].
[0058] Step S802: Compare the sampled signal A[n] with the sampled signal B[n-1] from the nearest time and determine whether the comparison result is greater than the signal tolerance value VT. If the comparison result is greater than the signal tolerance value VT, proceed to step S803; if the comparison result is less than the signal tolerance value VT, proceed to step S804.
[0059] Step S803: When the difference between the sampled signal A[n] and the sampled signal B[n-1] at a nearby time is greater than the signal tolerance value VT, a first noise suppression signal is output, wherein the first noise suppression signal is equal to the sampled signal A[n].
[0060] Step S804: When the difference between the sampled signal A[n] and the sampled signal B[n-1] at a nearby time is less than the signal tolerance value VT, a second noise suppression signal is output, wherein the value of the second noise suppression signal is between the sampled signal A[n] and the sampled signal at a nearby time by B[n-1]. For example, B[n-1]+VAR or B[n-1]-VAR as mentioned above, so that the signal fluctuation is suppressed within the variation tolerance value VAR.
[0061] In the above-described noise suppression method for a stylus, although the sampled signal A[n] is compared with the sampled signal B[n-1] from the nearest time, i.e., the previous time, those skilled in the art will understand, after referring to the above embodiments, that the first two units of time, three units of time, or the first N units of time are all possible implementation methods, depending on the sampling rate and application. Therefore, the present invention is not limited thereto. Furthermore, although the above embodiments use the processed signal B[n-1] as an example, those skilled in the art will understand that using the unprocessed sampled signal A[n-1] from the nearest time can also be used as an embodiment. Therefore, the present invention is also not limited thereto.
[0062] In summary, embodiments of the present invention sample the received signal and compare it with a previously sampled signal. The system determines whether the currently sampled signal has changed based on whether the comparison result is greater than a signal tolerance value. If the comparison result is greater than the signal tolerance value, the currently sampled signal is directly output. If the comparison result is less than the signal tolerance value, a change tolerance value is added to or subtracted from the previously sampled signal to obtain the output signal. This ensures that the processed signal, even under noise conditions, maintains its variation within the aforementioned change tolerance value, and only outputs the currently sampled signal when a real change occurs. This reduces the magnitude of various noise energies and increases the signal-to-noise ratio.
[0063] It should be understood that the examples and embodiments described herein are for illustrative purposes only, and various modifications or changes thereto will be suggested to those skilled in the art and will be included within the spirit and scope of this application and the scope of the appended claims.
Claims
1. A mobile device, characterized in that, include: A stylus, used to transmit stylus signals; A display touch device, comprising: Multiple touch electrodes; Multiple signal sampling devices, each signal sampling device including an input terminal and an output terminal, wherein the input terminals of the multiple signal sampling devices are respectively coupled to the multiple touch electrodes; and Multiple noise suppression circuits are provided, each including an input terminal and an output terminal. The input terminals of the multiple noise suppression circuits are respectively coupled to the output terminals of the multiple signal sampling devices. Among them, one of the aforementioned noise suppression circuits, a specific noise suppression circuit, is used to compare the sampled signal sampled by the corresponding signal sampling device with the sampled signal sampled by the corresponding signal sampling device at a nearby time. Wherein, when the difference between the sampled signal sampled by the corresponding signal sampling device and the sampled signal sampled by the corresponding signal sampling device at an adjacent time is greater than a signal tolerance value, the specific noise suppression circuit outputs the sampled signal sampled by the corresponding signal sampling device as a first noise suppression signal as an output signal. Specifically, when the difference between the sampled signal from the corresponding signal sampling device and the sampled signal from a nearby time period is less than a signal tolerance value, the specific noise suppression circuit outputs a second noise suppression signal as the output signal. The value of the second noise suppression signal is between the sampled signal from the corresponding signal sampling device and the sampled signal from a nearby time period.
2. The mobile device according to claim 1, characterized in that, Each signal sampling device further includes: A charge amplifier includes an input terminal and an output terminal, wherein the input terminal of the charge amplifier is coupled to the input terminal of the signal sampling device, and the charge amplifier is used to receive the signal from the coupled touch electrode to output an amplified touch signal; and An analog-to-digital converter includes an input terminal and an output terminal, wherein the input terminal of the analog-to-digital converter is coupled to the output terminal of the charge amplifier to receive the amplified touch signal, and the output terminal of the analog-to-digital converter is coupled to the output terminal of the signal sampling device to output a sampled signal corresponding to the signal sampling device.
3. The mobile device according to claim 1, characterized in that, Each noise suppression circuit further includes: A pre-buffer receives and temporarily stores the sampled signal from the corresponding signal sampling device; and A post-buffer is used to store the previously output sampled signal and to output the output signal. A digital comparator circuit includes a first input port, a second input port, and an output terminal. The first input port of the digital comparator circuit is coupled to the pre-buffer to receive the sampled signal corresponding to the signal sampling device. The second input port of the digital comparator circuit is coupled to the post-buffer. The output terminal of the digital comparator circuit outputs a selection signal. The logic of the digital comparator circuit determines the selection signal based on whether the difference between the input values of the first input port and the second input port of the digital comparator circuit is greater than the signal tolerance value. An addition / subtraction circuit includes a first input port, a second input port, and an output port. The first input port of the addition / subtraction circuit is coupled to the post-buffer to receive the previously output sampled signal. The second input port of the addition / subtraction circuit receives a variation tolerance value, and its output terminal outputs the second noise suppression signal. A multitasking selection circuit includes a selection terminal, a first input port, a second input port, and an output port. The first input port of the multitasking selection circuit is coupled to the pre-buffer to receive the sampled signal corresponding to the signal sampling device. The second input port of the multitasking selection circuit is coupled to the output port of the addition / subtraction circuit to receive the second noise suppression signal. The selection terminal of the multitasking selection circuit is coupled to the output terminal of the digital comparator circuit to receive the selection signal. The output port of the multitasking selection circuit determines, based on the logic of the selection signal, whether to output the data from the first input port or the second input port of the multitasking selection circuit.
4. The mobile device according to claim 3, characterized in that, The input port of the post-buffer is coupled to the output port of the multitasking selection circuit to receive the data output by the output port of the multitasking selection circuit as the previously output sampling signal. The output port of the post-buffer outputs the first noise suppression signal or the second noise suppression signal according to the temporarily stored data.
5. The mobile device according to claim 4, characterized in that, The pre-buffer further includes a storage block coupled to the output port of the post-buffer for storing the data output by the output port of the post-buffer as a second previously output sampled signal. Each noise suppression circuit further includes: A second multitasking selection circuit includes a selection terminal, a first input port, a second input port, and an output port. The first input port of the second multitasking selection circuit is coupled to the storage block of the pre-buffer to receive the second previously output sampling signal. The second input port of the second multitasking selection circuit is coupled to the output port of the post-buffer to receive the data output by the output port of the post-buffer. The selection terminal of the second multitasking selection circuit receives a delay selection signal. The output port of the second multitasking selection circuit is coupled to the second input port of the multitasking selection circuit and the second input port of the digital comparator circuit.
6. A noise suppression method for a stylus, applicable to a touch panel with stylus functionality, characterized in that, include: The signal received by a touch sensing electrode of the touch panel is sampled as a sampling signal; The sampled signal is compared with sampled signals from nearby times; When the difference between the sampled signal and a sampled signal from a nearby time period is greater than a signal tolerance value, a first noise suppression signal is used as an output signal, wherein the first noise suppression signal is equal to the sampled signal; and When the difference between the sampled signal and the sampled signal at the nearest time is less than the signal tolerance value, a second noise suppression signal is used as an output signal, wherein the value of the second noise suppression signal is between the sampled signal and the sampled signal at the nearest time.
7. The noise suppression method for a stylus according to claim 6, wherein, When the difference between the sampled signal and the sampled signal at a nearby time is less than the signal tolerance value, including: When the difference is positive, a variation tolerance value is added to the sampled signal from the nearest time to serve as the second noise suppression signal; and When the difference is negative or positive, the sampled signal from the nearest time is subtracted from the allowable variation value to obtain the second noise suppression signal. The allowable variation value is within the difference between the sampled signal and the sampled signal at the nearest time.
8. The noise suppression method for a stylus according to claim 6, characterized in that, The sampled signal at the nearest time includes the output signal from the previous time.
9. The noise suppression method for a stylus according to claim 6, characterized in that, The sampling signal for the nearest time includes the output signal for the previous N times, where N is a natural number.