Signal processing circuit and position detection device

Abstract

The present invention provides a signal processing circuit, which includes a control unit, a transmitting driving unit, an analog switch array, a signal amplifying unit, a detection integration unit and a transmitting and receiving antenna connected to the analog switch array. The transmitting and receiving antenna includes a Y-direction transmitting and receiving antenna and an X-direction transmitting and receiving antenna, and the analog switch array includes a Y-direction analog switch array connected to the Y-direction transmitting and receiving antenna and an X-direction analog switch array connected to the X-direction transmitting and receiving antenna. The control unit has two built-in analog-to-digital converters to process the signals received by the transmitting and receiving antennas respectively, and the signal processing circuit also includes a level conversion unit arranged between the analog-to-digital converter and the signal amplifying unit, and the level conversion unit linearly converts the signals received by the Y-direction transmitting and receiving antenna and the X-direction transmitting and receiving antenna respectively. The signal processing circuit provided by the present invention has low cost, fast handwriting speed and less cursor jitter.

Description

[Technical field]

[0001] The present invention relates to the field of electromagnetic induction technology, and in particular to a signal processing circuit and a position detection device. [Background technology]

[0002] The system block diagram of the existing electromagnetic passive handwriting system is shown in Figure 1 , it outputs a pulse signal to the transmitting circuit through the MCU control unit (micro control unit), so that an electromagnetic transmitting signal with a certain intensity is generated on the writing surface. The LC resonant circuit in the stylus senses the electromagnetic transmitting signal and gathers energy. When the electromagnetic transmitting signal stops, the LC resonant circuit generates an electromagnetic signal with a gradually attenuated amplitude at its inherent resonant frequency. When the transmitting and receiving antenna receives the electromagnetic signal emitted by the stylus, it is first amplified by the signal amplification circuit, then detected and integrated, and the high-frequency fundamental signal is removed. The obtained low-frequency envelope signal is sent to the MCU control unit for processing to complete the positioning and pressure sensing functions.

[0003] The above technology is often used on digital tablets or digital screens with little interference. However, when it is applied to LCD modules, the LCD drive signal is strong and the electromagnetic interference generated is large, which will cause the digital screen cursor to jitter. To solve this problem, the method of increasing the amplitude of the transmitted signal or improving the system signal-to-noise ratio is currently widely used. This method requires the addition of a boost circuit, and the transmitting part must use high-voltage components, which increases the cost of the electromagnetic passive handwriting system; at the same time, high-power transmission will increase the power consumption of the entire machine, which is not conducive to energy saving.

[0004] Therefore, it is necessary to provide a signal processing circuit and a position detection device to solve the above problems. [Summary of the invention]

[0005] The electromagnetic passive handwriting system in the prior art is relatively expensive and is not conducive to energy saving. Therefore, the present invention provides a signal processing circuit and a position detection device for solving the above problems.

[0006] A signal processing circuit comprises a control unit, a transmitting drive unit, an analog switch array, a signal amplifying unit, a detection integration unit and a transmitting and receiving antenna connected to the analog switch array, which are connected in sequence. The invention is characterized in that the transmitting and receiving antenna comprises a Y-direction transmitting and receiving antenna and an X-direction transmitting and receiving antenna, the analog switch array comprises a Y-direction analog switch array connected to the Y-direction transmitting and receiving antenna and an X-direction analog switch array connected to the X-direction transmitting and receiving antenna, the control unit has two built-in analog-to-digital converters to respectively process the signals received by the transmitting and receiving antennas, the signal processing circuit also comprises a level conversion unit arranged between the analog-to-digital converter and the signal amplifying unit, the level conversion unit respectively performs linear conversion on the signals received by the Y-direction transmitting and receiving antenna and the X-direction transmitting and receiving antenna, and the signals received by the transmitting and receiving antennas are sent to the analog-to-digital converter via the level conversion unit.

[0007] Preferably, each of the analog-to-digital converters includes at least two channels.

[0008] Preferably, the detection integration unit and the level conversion unit are respectively connected to the analog-to-digital converter, and the signals received by the transmitting and receiving antennas are respectively sent to the analog-to-digital converter through the channel through the detection integration unit and the level conversion unit, and the analog-to-digital converter selects one of the processing methods.

[0009] Preferably, the analog-to-digital converter is processed by a digital band filtering process and then by a waveform fitting algorithm.

[0010] Preferably, the digital bandpass filter comprises a FIR bandpass filter or a Butterworth filter.

[0011] Preferably, the waveform fitting algorithm includes a least squares curve fitting algorithm or a sinusoidal curve fitting algorithm.

[0012] Preferably, the clock frequency of the control unit is not less than 150 MHz.

[0013] Preferably, the sampling rate of the analog-to-digital converter is not less than 5 MSPS.

[0014] The present invention also provides a position detection device, which includes the above-mentioned signal processing circuit.

[0015] Compared with the prior art, the signal processing circuit and position detection device provided by the present invention have the following beneficial effects:

[0016] (1) Digital processing is adopted, with flexible software programming, high data processing speed, good digital filter performance and strong anti-interference performance;

[0017] (2) The signal processing circuit is simple, and low-voltage components can be selected to reduce costs;

[0018] (3) Horizontal and vertical coordinates are processed simultaneously to shorten the signal processing time. This allows the opportunity to report more coordinates and pressure data within the same time. The increase in the reporting rate will result in faster handwriting speed and reduced cursor jitter on the digital screen.

Brief Description of the Drawings

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0020] Figure 1 A system block diagram of a signal processing circuit shown in the prior art;

[0021] Figure 2 It is a system block diagram of the signal processing circuit shown in the present invention. [Specific implementation method]

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] The present invention provides a signal processing circuit 100, which includes a control unit 10, a transmitting driving unit 20, an analog switch array 30, a signal amplifying unit 40, a detection integration unit 50, a transmitting and receiving antenna 60 connected to the analog switch array 30, and a level conversion unit 70 connected to the control unit 10. In this embodiment, the control unit 10 is an MCU micro control unit.

[0024] The transmitting and receiving antenna 60 includes a Y-direction transmitting and receiving antenna 61 and an X-direction transmitting and receiving antenna 62, and the analog switch array 30 includes a Y-direction analog switch array 31 connected to the Y-direction transmitting and receiving antenna 61 and an X-direction analog switch array 32 connected to the X-direction transmitting and receiving antenna 62. The transmitting antenna 60 processes the vertical and horizontal coordinates simultaneously through the Y-direction transmitting and receiving antenna 61 and the X-direction transmitting and receiving antenna 62, respectively, shortening the time for signal reception and processing, and can shorten the time, process more coordinates and pressure sensing data in the same time, improve the reporting rate, and obtain a faster handwriting speed.

[0025] The control unit 10 has two built-in analog-to-digital converters 11, and the analog-to-digital converters 11 are used to process the signals received by the transmitting and receiving antennas 60. Specifically, the analog-to-digital converters 11 are respectively connected to the detection and integration unit 50 and the level conversion unit 70, and the level conversion unit 70 performs linear conversion on the signals received by the Y-direction transmitting and receiving antennas 61 and the X-direction transmitting and receiving antennas 62, respectively.

[0026] Each analog-to-digital converter 11 includes at least two channels, the detection integration unit 50 and the level conversion unit 70 are respectively connected to the analog-to-digital converter 11, and the signals received by the transmitting and receiving antennas are respectively sent to the analog-to-digital converter 11 through the channels through the detection integration unit 50 and the level conversion unit 70, and the analog-to-digital converter 11 selects one of the processing methods. Specifically, the analog data converter 11 processes the handwriting signal through digital band filtering, and then restores it to an ideal electromagnetic handwriting signal through a waveform fitting algorithm to eliminate the interference of the screen timing signal. In particular, the waveform fitting algorithm includes a least squares curve fitting algorithm or a sine curve fitting algorithm, and the digital bandpass filter includes a FIR bandpass filter or a Butterworth filter. In the present invention, in order to meet the high-speed computing requirements for digital signal processing, the clock frequency of the control unit 10 is not less than 150MHz. At this time, the sampling rate of the analog-to-digital converter 11 is not less than 5MSPS.

[0027] The signal processing circuit works as follows:

[0028] The transmitting and receiving antenna 60 respectively transmits the X fundamental wave signal and the Y fundamental wave signal to the analog-to-digital converter 11 to convert them into digital signals after being processed by the signal amplifying unit 40 through the Y-direction transmitting and receiving antenna 61 and the X-direction transmitting and receiving antenna 62. After the handwriting signal is processed by the signal amplifying unit 40, it can be selected to be linearly converted by the detection integration unit 50 or the level conversion unit 70 to eliminate interference signals, restore the ideal electromagnetic handwriting signal, and obtain its coordinate value and pressure sensitivity value.

[0029] The present invention also provides a position detection device, which includes the above-mentioned signal processing circuit.

[0030] Compared with the prior art, the signal processing circuit and position detection device provided by the present invention have the following beneficial effects:

[0031] (1) Digital processing is adopted, with flexible software programming, high data processing speed, good digital filter performance and strong anti-interference performance;

[0032] (2) The signal processing circuit is simple, and low-voltage components can be selected to reduce costs;

[0033] (3) Horizontal and vertical coordinates are processed simultaneously to shorten the signal time. This allows the opportunity to report more coordinates and pressure data within the same time. The increase in the reporting rate will result in faster handwriting speed and reduced cursor jitter on the digital screen.

[0034] The above description is only an implementation mode of the present invention. It should be pointed out that, for ordinary technicians in this field, improvements can be made without departing from the creative concept of the present invention, but these all belong to the protection scope of the present invention.

Claims

1. A signal processing circuit, comprising a control unit, a transmitting driving unit, an analog switch array, a signal amplifying unit, a detection integrating unit and a transmitting and receiving antenna connected to the analog switch array, characterized in that: The transmitting and receiving antenna comprises a Y-direction transmitting and receiving antenna and an X-direction transmitting and receiving antenna, the analog switch array comprises a Y-direction analog switch array connected to the Y-direction transmitting and receiving antenna and an X-direction analog switch array connected to the X-direction transmitting and receiving antenna, the control unit has two built-in analog-to-digital converters to process the signals received by the transmitting and receiving antennas respectively, the signal processing circuit further comprises a level conversion unit arranged between the analog-to-digital converter and the signal amplification unit, the level conversion unit respectively performs linear conversion on the signals received by the Y-direction transmitting and receiving antenna and the X-direction transmitting and receiving antenna, and the signals received by the transmitting and receiving antennas are sent to the analog-to-digital converter via the level conversion unit; The control unit is a MCU micro control unit; Each of the analog-to-digital converters includes at least two channels; wherein the detection integration unit and the level conversion unit are respectively connected to the analog-to-digital converter, and the signals received by the transmitting and receiving antennas are respectively sent to the analog-to-digital converter through the channels through the detection integration unit and the level conversion unit, and the analog-to-digital converter selects one of the processing methods.

2. The signal processing circuit according to claim 1, characterized in that: The analog-to-digital converter is processed by a digital bandpass filter and then by a waveform fitting algorithm.

3. The signal processing circuit according to claim 2, characterized in that: The digital bandpass filter includes a FIR bandpass filter or a Butterworth filter.

4. The signal processing circuit according to claim 2, characterized in that: The waveform fitting algorithm includes a least squares curve fitting algorithm or a sine curve fitting algorithm.

5. The signal processing circuit according to claim 1, characterized in that: The clock frequency of the control unit is not less than 150 MHz.

6. The signal processing circuit according to claim 1, characterized in that: The sampling rate of the analog-to-digital converter is not less than 5MSPS.

7. A position detection device, characterized in that: The invention comprises the signal processing circuit described in any one of claims 1 to 6.

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