Touch-control method, sensing signal processing circuit, and mutual capacitance touch-control apparatus

Abstract

A touch-control method, a sensing signal processing circuit, and a mutual capacitance touch-control apparatus. The sensing signal processing circuit comprises: a first signal processing branch and a second signal processing branch, wherein two input ends of a first frequency mixer of the first signal processing branch respectively receive a superimposed sensing signal and a first local oscillator signal, and an output end of the first frequency mixer is coupled to an input end of a first integral circuit; the first integral circuit outputs a baseband signal corresponding to a first sensing signal; two input ends of a second frequency mixer of the second signal processing branch respectively receive the superimposed sensing signal and a second local oscillator signal, and an output end of the second frequency mixer is coupled to an input end of a second integral circuit; and the second integral circuit outputs a baseband signal corresponding to a second sensing signal, and a second driving frequency is determined on the basis of a first zero-point frequency of a low-pass filter and a first driving frequency. By using the solution, the complexity of a dual-frequency mutual capacitance touch-control apparatus is not excessively increased while mutual interference between two driving frequencies is effectively suppressed.

Description

Touch control method and sensing signal processing circuit, mutual capacitance touch device

[0001] This application claims priority to Chinese Patent Application No. 202510034668.6, filed on January 8, 2025, entitled “Touch Method and Sensing Signal Processing Circuit, Mutual Capacitive Touch Device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This invention relates to the field of touch technology, and in particular to a touch control method, a sensing signal processing circuit, and a mutual capacitance touch device. Background Technology

[0003] In traditional single-frequency mutual capacitance touch devices, a single driving frequency is typically used to drive the transmitting electrode (TX). The receiving electrode (RX) uses a local oscillator signal of the same frequency to mix with the sensing signal. The mixed signal is then integrated, and the resulting calculation yields the signal change at the touch node. The single-frequency mutual capacitance touch device determines whether a touch action has occurred at the touch node based on the change in the signal at the touch node.

[0004] Single-frequency mutual capacitance touch devices are insufficient to meet the demands of high reporting rates. Currently, dual-frequency and multi-frequency mutual capacitance touch devices exist. In traditional dual-frequency mutual capacitance touch devices, two different driving frequencies are used to drive different transmitting electrodes. Compared to single-frequency mutual capacitance touch devices, dual-frequency mutual capacitance touch devices double the reporting rate.

[0005] In dual-frequency mutual-capacitance touch devices, interference between the two driving frequencies can affect the signal variation of the touch nodes. Existing technologies include the following methods to suppress mutual interference between the two driving frequencies: 1) utilizing the orthogonality of the two driving frequencies in the measurement time to eliminate mutual interference; 2) using the out-of-band rejection capability of filters to remove interference signals; and 3) measuring the amount of interference signal in advance and then filtering it out through signal processing.

[0006] The dual-frequency mutual capacitance touch device employing the above-mentioned mutual interference suppression method is highly complex. Summary of the Invention

[0007] The purpose of this invention is at least to provide a sensing signal processing circuit that can effectively suppress mutual interference between two driving frequencies without excessively increasing the complexity of the dual-frequency mutual capacitance touch device.

[0008] In a first aspect, the present invention provides a sensing signal processing circuit, comprising: a first signal processing branch and a second signal processing branch, wherein the first signal processing branch includes a first mixer and a first integrator circuit, and the second signal processing branch includes a second mixer and a second integrator circuit; wherein the first mixer has a first terminal for receiving a superimposed sensing signal, a second terminal for receiving a first local oscillator signal, and an output terminal coupled to the input terminal of the first integrator circuit; the superimposed sensing signal includes a first sensing signal generated by coupling a receiving electrode to a first transmitting electrode, and a second sensing signal generated by coupling the receiving electrode to a second transmitting electrode, wherein the first transmitting electrode receives a driving signal of a first driving frequency, and the second transmitting electrode receives a driving signal of a first driving frequency; The emitter electrode receives a drive signal at a second drive frequency, wherein the first drive frequency is not equal to the second drive frequency; the first integrator circuit outputs a baseband signal corresponding to the first sensing signal; the second mixer has a first terminal for receiving the superimposed sensing signal, a second terminal for receiving a second local oscillator signal, and its output terminal coupled to the input terminal of the second integrator circuit; the frequency of the first local oscillator signal is equal to the first drive frequency, and the frequency of the second local oscillator signal is equal to the second drive frequency; the second integrator circuit outputs a baseband signal corresponding to the second sensing signal; the second integrator circuit includes a second low-pass filter, and the second drive frequency is determined by the first zero-point frequency of the second low-pass filter.

[0009] The sensing signal processing circuit includes a first signal processing branch and a second signal processing branch. The first signal processing branch obtains the baseband signal corresponding to the first sensing signal; the second signal processing branch obtains the baseband signal corresponding to the second sensing signal. Both the first and second integrating circuits include a low-pass filter. The second driving frequency is determined by the first driving frequency and the first zero-point frequency of the low-pass filter. In other words, the second driving frequency is related to the first driving frequency and the first zero-point frequency. Therefore, by reasonably setting the second driving frequency, the mutual interference between the second and first driving frequencies can be reduced, and only a corresponding second signal processing branch needs to be added, which has a minimal impact on the complexity of the dual-frequency mutual-capacitance touch device.

[0010] Optionally, the second driving frequency is the sum of the first driving frequency and the first zero-point frequency.

[0011] The second driving frequency is the sum of the first driving frequency and the first zero-point frequency. In other words, the difference between the second driving frequency and the first driving frequency is the first zero-point frequency. Therefore, the mutual interference between the second driving frequency and the first driving frequency is 0.

[0012] Optionally, the filter coefficients of the low-pass filter are first filter coefficients; when the filter coefficients are the first filter coefficients, the offset between the first zero-point frequency and the first difference is within a preset threshold range, and the first difference is the difference between the second driving frequency and the first driving frequency.

[0013] Optionally, the sensing signal processing circuit further includes a control unit coupled to both low-pass filters, adapted to adjust the filter coefficients of both low-pass filters to the first filter coefficients.

[0014] Optionally, the control unit is adapted to: determine candidate filter coefficients for the two low-pass filters based on the scan time of the drive signal, the candidate filter coefficients corresponding to candidate zero frequencies; adjust the candidate filter coefficients to the first filter coefficients if the difference between the second difference and the first drive frequency is outside the threshold range; and determine the candidate filter coefficients to the first filter coefficients if the difference between the first difference and the first drive frequency is within the threshold range; wherein the second difference is the difference between the second drive frequency and the candidate zero frequency.

[0015] The first and second drive frequencies are typically obtained by dividing a reference clock signal generated by a clock signal generation circuit. Therefore, the difference between the second and first drive frequencies may deviate from the first zero-point frequency. By adjusting the filter coefficients of the low-pass filter, the filter coefficients can be adjusted to match the first filter coefficients. This ensures that the difference between the second and first drive frequencies falls within the first zero-point frequency.

[0016] Optionally, the first zero-point frequency can be any zero-point frequency of the low-pass filter.

[0017] Optionally, the first zero-point frequency is the zero-point frequency with the smallest frequency value of the low-pass filter.

[0018] Optionally, the low-pass filter has at least two zero frequencies; the first zero frequency is any zero frequency among all the zero frequencies of the low-pass filter that is free from interference.

[0019] Optionally, the first zero-point frequency is the zero-point frequency with the smallest frequency value among the at least two zero-point frequencies that are free from interference.

[0020] Optionally, the low-pass filter includes any one of the following: a finite impulse response digital filter or an infinite impulse response digital filter.

[0021] Secondly, the present invention also provides a touch control method, comprising: determining a first driving frequency; determining candidate filter coefficients of a low-pass filter based on the scan time of the acquired driving signal; the candidate filter coefficients corresponding to candidate zero-point frequencies; detecting that the difference between a second difference and the first driving frequency is outside a preset threshold range, adjusting the candidate filter coefficients to first filter coefficients; and when the filter coefficients of the low-pass filter are the first filter coefficients, the offset between the first zero-point frequency and the first difference is within a preset threshold range, the first difference being the difference between the second driving frequency and the first driving frequency, and the second difference being the difference between the second driving frequency and the candidate zero-point frequency; driving the first transmitting electrode with the first driving frequency, and driving the second transmitting electrode with the second driving frequency.

[0022] Thirdly, the present invention also provides a mutual capacitance touch device, including a transmitting electrode and a receiving electrode arranged in a cross configuration, wherein a first transmitting electrode of the transmitting electrode receives a driving signal of a first driving frequency, and a second transmitting electrode of the transmitting electrode receives a driving signal of a second driving frequency, wherein the first driving frequency and the second driving frequency are not equal; and a sensing signal processing circuit as described above. Attached Figure Description

[0023] Figure 1 is a schematic diagram of the electrode distribution of a traditional mutual capacitance touch device;

[0024] Figure 2 shows the waveforms of the driving signals for the transmitting electrode TX1 and the transmitting electrode TX2.

[0025] Figure 3 is a waveform diagram of the superimposed sensing signal received by the receiving electrode;

[0026] Figure 4 is a schematic diagram of a signal processing device according to an embodiment of the present invention;

[0027] Figure 5 shows the pole-zero plot of a 7th-order FIR digital low-pass filter;

[0028] Figure 6 is the amplitude-frequency diagram of the 7th-order FIR digital low-pass filter corresponding to Figure 5;

[0029] Figure 7 shows the pole-zero plot of a fourth-order Bishkek type II IIR digital low-pass filter;

[0030] Figure 8 is the amplitude-frequency diagram of the fourth-order Byshev type II IIR digital low-pass filter corresponding to Figure 7;

[0031] Figure 9 is a flowchart of a touch control method in an embodiment of the present invention. Detailed Implementation

[0032] Referring to Figure 1, a schematic diagram of the electrode distribution of a mutual capacitance touch device is shown. In Figure 1, the horizontal line represents the transmitting electrode TX (including TX1, TX2, ..., TXn), and the vertical line represents the receiving electrode RX (including RX1, RX2, ..., RXn). The intersection of the transmitting electrode TX and the receiving electrode RX constitutes the touch node. The signal change of the touch node is detected to determine whether a touch has occurred, and the coordinates of the corresponding touch node are reported.

[0033] In a dual-frequency mutual capacitance touch device, two different driving frequencies are used to send driving signals to different transmitting electrodes (such as TX1 and TX2, or TX1 and TX3, etc.). The different driving frequencies are used to distinguish the signal changes at different touch nodes on the same receiving electrode. Thus, the receiving electrode can receive the superposition of the sensing signals from the two driving frequencies.

[0034] Figure 2 shows the waveforms of the driving signal on the transmitting electrode TX1 and the driving signal on the transmitting electrode TX2. The driving frequency of the driving signal on the transmitting electrode TX1 is different from that of the driving frequency of the driving signal on the transmitting electrode TX2.

[0035] Figure 3 shows the waveform of the superimposed sensing signal received by the receiving electrode (RX).

[0036] However, in dual-frequency mutual capacitance touch devices, there is mutual interference between the two different driving frequencies, which in turn affects the amount of signal change at the touch node.

[0037] In the prior art, there are several methods to suppress mutual interference between two driving frequencies: 1) using the orthogonality of the two driving frequencies in the measurement time to eliminate mutual interference; 2) using the out-of-band rejection capability of the filter to filter out the interference signal; 3) measuring the interference amount of the interference signal in advance and filtering out the interference signal through signal processing in the later stage.

[0038] For method 1) above, high accuracy of the two driving frequencies is required. If one of the driving frequencies deviates, the orthogonality of the two driving frequencies will be disrupted. Therefore, a phase-locked loop (PLL) or a digital direct frequency synthesizer (DDS) needs to be set in the dual-frequency mutual capacitance touch device to ensure the accuracy of the two driving frequencies.

[0039] For method 2) above, it is necessary to increase the frequency interval between the two driving frequencies, which makes it difficult to select a suitable driving frequency.

[0040] For method 3) above, it is necessary to know in advance the amount of interference signals corresponding to different driving frequencies and different measurement durations, which increases the complexity of the dual-frequency mutual capacitance touch device.

[0041] In this embodiment of the invention, the sensing signal processing circuit includes a first signal processing branch and a second signal processing branch. The first signal processing branch includes a first mixer and a first integrator circuit, and the second signal processing branch includes a second mixer and a second integrator circuit. Both the first integrator circuit and the second integrator circuit include a low-pass filter, and the second driving frequency is determined by the first driving frequency and the first zero-point frequency of the low-pass filter.

[0042] In other words, the second driving frequency is related to the first driving frequency and the first zero-point frequency. Therefore, by reasonably setting the second driving frequency, the mutual interference between the second driving frequency and the first driving frequency can be reduced, and only a corresponding second signal processing branch needs to be added, which has little impact on the complexity of the dual-frequency mutual capacitance touch device.

[0043] To make the above-mentioned objectives, features and beneficial effects of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0044] This invention provides a sensing signal processing circuit that can be applied in a dual-frequency mutual capacitance touch device. The sensing signal processing circuit can be coupled to a receiving electrode, which can receive the superimposed sensing signal.

[0045] In a specific implementation, the superimposed sensing signal is the superposition of the first sensing signal and the second sensing signal. The first sensing signal is generated by coupling the receiving electrode and the first transmitting electrode, and the first transmitting electrode receives a driving signal at the first driving frequency; the second sensing signal is generated by coupling the receiving electrode and the second transmitting electrode, and the second transmitting electrode receives a driving signal at the second driving frequency; the first driving frequency is not equal to the second driving frequency.

[0046] In this embodiment of the invention, the first emitting electrode and the second emitting electrode mentioned above can refer to two emitting electrodes scanned within a single scan time. In other words, a corresponding first emitting electrode and a second emitting electrode exist within different scan times. The first emitting electrode and the second emitting electrode constitute all emitting electrodes.

[0047] Referring to the example in Figure 1, during the first scan time, the first emitting electrode is emitting electrode TX1 and the second emitting electrode is emitting electrode TX2; during the second scan time, the first emitting electrode is emitting electrode TX3 and the second emitting electrode is emitting electrode TX4.

[0048] Referring to Figure 4, a schematic diagram of a sensing signal processing circuit according to an embodiment of the present invention is shown.

[0049] In this embodiment of the invention, the sensing signal processing circuit may include: a first signal processing branch and a second signal processing branch. The first signal processing branch may include a first mixer 41 and a first integrator 42, and the second signal processing branch may include a second mixer 43 and a second integrator 44, wherein:

[0050] The first input terminal of the first mixer 41 receives the superimposed sensing signal, the second input terminal of the first mixer 41 receives the first local oscillator signal, and the output terminal of the first mixer 41 is coupled to the input terminal of the first integrating circuit 42.

[0051] The first integrating circuit 42 outputs the baseband signal corresponding to the first sensing signal;

[0052] The first input terminal of the second mixer 43 receives the superimposed sensing signal, the second input terminal of the second mixer 43 receives the second local oscillator signal, and the output terminal of the second mixer 43 is coupled to the input terminal of the second integrator circuit 44.

[0053] The second integrator circuit 44 outputs the baseband signal corresponding to the second sensing signal.

[0054] In practice, the frequency of the first local oscillator signal can be equal to the first driving frequency, and the frequency of the second local oscillator signal can be equal to the second driving frequency.

[0055] The sensing signal processing circuit may further include a first local oscillator circuit 45 and a second local oscillator circuit 46, wherein the first local oscillator circuit 45 is used to generate a first local oscillator signal and the second local oscillator circuit 46 is used to generate a second local oscillator signal.

[0056] Specifically, the specific circuit structure of the first local oscillator circuit 45 and the principle of generating the first local oscillator signal, as well as the specific circuit structure of the second local oscillator circuit 46 and the principle of generating the second local oscillator signal, can all be referred to the implementation of local oscillator circuits in the prior art, and will not be elaborated here.

[0057] In this embodiment of the invention, both the first integrating circuit 42 and the second integrating circuit 44 may include a low-pass filter, and the low-pass filter in the first integrating circuit 42 and the low-pass filter in the second integrating circuit 44 have the same zero-point frequency. The low-pass filter may include at least one zero-point frequency, and one of the at least one zero-point frequencies may be selected as the first zero-point frequency. The second driving frequency is determined jointly by the first driving frequency and the first zero-point frequency.

[0058] In practice, the difference between the second driving frequency and the first driving frequency can be equal to the first zero-point frequency. In other words, the second driving frequency is the sum of the first zero-point frequency and the first driving frequency.

[0059] In practice, a low-pass filter can be either an analog filter or a digital filter.

[0060] In some embodiments, the low-pass filter is a digital filter, specifically an Infinite Impulse Response (IIR) digital filter or a Finite Impulse Response (FIR) digital filter.

[0061] In this embodiment of the invention, for ease of distinction, the low-pass filter included in the first integrating circuit 42 can be simply referred to as the first low-pass filter, and the low-pass filter included in the second integrating circuit 44 can be simply referred to as the second low-pass filter. The first low-pass filter and the second low-pass filter can be low-pass filters with the same structure and the same filter parameters, thereby ensuring that their zero-point frequencies are the same.

[0062] For example, both the first low-pass filter and the second low-pass filter are FIR digital filters. Alternatively, both the first low-pass filter and the second low-pass filter may be IIR digital filters.

[0063] In the first signal processing branch, the first mixed signal output by the first mixer 41 can be low-pass filtered by the first low-pass filter to obtain the baseband signal corresponding to the first sensing signal. Correspondingly, in the second signal processing branch, the second mixed signal output by the second mixer 43 can be low-pass filtered by the second low-pass filter to obtain the baseband signal corresponding to the second sensing signal.

[0064] In this embodiment of the invention, the first signal processing branch and the second signal processing branch have the same structure. Their working principles and processing procedures are also almost identical. In the following embodiments, the sensing signal processing circuit will be described using the first signal processing branch as an example.

[0065] The first low-pass filter may include one or more zero frequencies. When the first low-pass filter includes only one zero frequency, that zero frequency can be used as the first zero frequency. When the first low-pass filter includes two or more zero frequencies, one of the zero frequencies corresponding to the first low-pass filter can be selected as the first zero frequency.

[0066] In practice, the order of the first low-pass filter can be greater than 3, thereby providing at least one zero-point frequency.

[0067] Taking a 7th-order FIR digital low-pass filter as an example.

[0068] Referring to Figure 5, a pole-zero plot of a 7th-order FIR digital low-pass filter is shown. In Figure 5, the horizontal axis is the real axis (Re[z]), and the vertical axis is the imaginary axis (Im[z]). Referring to Figure 6, the amplitude-frequency plot of the 7th-order FIR digital low-pass filter corresponding to Figure 5 is shown. In Figure 6, the horizontal axis is the frequency (Freq), and the vertical axis is the amplitude (Amp).

[0069] As shown in Figure 5, the 7th-order FIR digital low-pass filter includes 7 zero frequencies, symmetrically distributed on both sides of the real axis. Zero frequency 1 and zero frequency 7 are symmetrical about the real axis, zero frequency 2 and zero frequency 6 are symmetrical about the real axis, zero frequency 3 and zero frequency 5 are symmetrical about the real axis, and zero frequency 4 is the point of the real axis on the unit circle, with a value of Fs / 2, where Fs is the sampling frequency.

[0070] As shown in Figure 6, F1 is the zero-point frequency 1, F2 is the zero-point frequency 2, and F3 is the zero-point frequency 3.

[0071] Taking a fourth-order Byshev II type IIR digital low-pass filter as an example.

[0072] Referring to Figure 7, a pole-zero plot of a fourth-order Byshev Type II IIR digital low-pass filter is shown. In Figure 7, the horizontal axis is the real axis (Re[z]), and the vertical axis is the imaginary axis (Im[z]). Referring to Figure 8, the amplitude-frequency plot of the fourth-order Byshev Type II IIR digital low-pass filter corresponding to Figure 7 is shown. In Figure 8, the horizontal axis is the frequency (Freq), and the vertical axis is the amplitude (Amp).

[0073] As shown in Figure 7, the fourth-order Byshev Type II IIR digital low-pass filter includes four zero frequencies, which are symmetrically distributed on both sides of the real axis. Zero frequency 1 and zero frequency 4 are symmetrical about the real axis, and zero frequency 2 and zero frequency 3 are symmetrical about the real axis.

[0074] As shown in Figure 8, F1 is the zero-point frequency 1, and F2 is the zero-point frequency 2.

[0075] In practice, the first zero-point frequency can be any zero-point frequency of the first low-pass filter.

[0076] For example, if the first low-pass filter is a 7th-order FIR digital low-pass filter, then the first zero frequency is F1, or F2, or F3.

[0077] For example, if the first low-pass filter is a fourth-order Byshev II type IIR digital low-pass filter, then the first zero frequency is F1 or F2.

[0078] In practice, the first zero-point frequency can be the zero-point frequency with the smallest frequency value of the first low-pass filter.

[0079] For example, if the first low-pass filter is a 7th-order FIR digital low-pass filter, then the first zero frequency is F1.

[0080] For example, if the first low-pass filter is a fourth-order Byshev II type IIR digital low-pass filter, then the first zero frequency is F1.

[0081] In specific implementations, the first low-pass filter may include two or more zero frequencies. In some embodiments, the first zero frequency may be a zero frequency among all the zero frequencies of the first low-pass filter that is free from interference.

[0082] For example, if the first low-pass filter is a 7th-order FIR digital low-pass filter and there is interference on F1, then F2 or F3 is selected as the first zero frequency.

[0083] Furthermore, if the first low-pass filter may include two or more zero frequencies, then the first zero frequency may be: the zero frequency with the smallest frequency value among all zero frequencies that is free from interference.

[0084] Continuing with the example of a 7th-order FIR digital low-pass filter as the first low-pass filter, interference exists on F1, but not on F2 and F3. Therefore, F2 is chosen as the first zero-point frequency.

[0085] In this embodiment of the invention, a first driving frequency can be selected to drive the first transmitting electrode based on the noise distribution and interference frequency distribution in the actual application scenario. The first driving frequency can be selected as a frequency with low noise and a large frequency interval between it and the interference frequency. That is, a frequency with low interference should be selected as the first driving frequency.

[0086] After selecting the first driving frequency, the filter coefficients of the first low-pass filter can be determined based on the scan time required to perform a complete scan of all emitter electrodes, and then the first zero-point frequency can be determined based on the filter coefficients. After determining the first zero-point frequency, the first zero-point frequency is summed with the first driving frequency, and the sum is the second driving frequency.

[0087] In practice, different mutual capacitance touch devices allocate different scan times for the transmitting electrode to perform one scan, resulting in different filter coefficients for the corresponding first low-pass filter. The filter coefficients can be pre-determined based on these different scan times.

[0088] In practical implementation, a dual-frequency mutual capacitance touch device may include a clock signal generation circuit and a frequency divider. The clock signal generation circuit generates and outputs a reference clock signal, which is then input to the frequency divider. After the frequency divider divides the reference clock signal, a first driving frequency and a second driving frequency can be obtained.

[0089] However, there is a scenario where the difference between the second driving frequency and the first driving frequency may not be exactly equal to the first zero-point frequency. That is, there is a certain deviation Δ1 between the difference between the second driving frequency and the first driving frequency (hereinafter referred to as the second difference) and the first zero-point frequency, and Δ1 is not equal to 0.

[0090] In some embodiments, if the deviation value Δ1 is outside a preset threshold range, the filter coefficients of the first low-pass filter are adjusted. By adjusting the filter coefficients of the first low-pass filter, the first zero-point frequency is also adjusted accordingly. After the filter coefficients of the first low-pass filter are adjusted to the first filter coefficients, the deviation between the second difference and the adjusted first zero-point frequency is updated to Δ2, and Δ2 is within the preset threshold range.

[0091] In other embodiments, if the deviation value Δ1 is not equal to 0, the filter coefficients of the first low-pass filter are adjusted. By adjusting the filter coefficients of the first low-pass filter, the first zero-point frequency is also adjusted accordingly. When the filter coefficients of the first low-pass filter are adjusted to the first filter coefficients, the deviation between the second difference and the adjusted first zero-point frequency is 0.

[0092] In this embodiment of the invention, for a dual-frequency mutual capacitance touch device, a first driving frequency, a second driving frequency, and an adjusted first zero-point frequency can be predetermined, and these frequencies can be stored in a memory by programming. When the dual-frequency mutual capacitance touch device is working, the first driving frequency, the second driving frequency, and the adjusted first zero-point frequency can be read from the memory. The first driving frequency drives the first transmitting electrode, the second driving frequency drives the second transmitting electrode, and the filter coefficients of the first low-pass filter are set to the first filter coefficients.

[0093] In other words, the first driving frequency, the second driving frequency, and the adjusted first zero-point frequency can be pre-stored in the memory, and can be directly retrieved from the memory when the dual-frequency mutual capacitance touch device is working.

[0094] Alternatively, based on the specific working scenario of the dual-frequency mutual capacitance touch device, the corresponding first driving frequency and second driving frequency can be selected, and the corresponding first zero-point frequency can be determined.

[0095] Specifically, in this embodiment of the invention, the sensing signal processing circuit may further include a control unit, which may be coupled to the first low-pass filter. The control unit is adapted to adjust the filter coefficients of the first low-pass filter to the first filter coefficients.

[0096] The control unit can determine the candidate filter coefficients of the first low-pass filter based on the scan time of the drive signal. The candidate filter coefficients correspond to the candidate zero-point frequencies. The scan time of the aforementioned drive signal is the time required for all the first and second emitter electrodes to complete one full scan.

[0097] The control unit can detect whether the difference between the first difference and the first driving frequency is within a preset threshold range. If the difference is detected to be within the preset threshold range, the candidate zero frequency can be used as the first zero frequency; conversely, if the difference is detected to be outside the preset threshold range, the candidate filter coefficients can be adjusted to become the first filter coefficients, thereby ensuring that the difference between the first difference and the first driving frequency is within the preset threshold range. The aforementioned first difference is the difference between the second driving frequency and the candidate zero frequency.

[0098] Therefore, by adjusting the filter coefficients of the first low-pass filter, it can be ensured that the difference between the second driving frequency and the first driving frequency is the zero-point frequency of the first low-pass filter, thereby avoiding mutual interference between the second driving frequency and the first driving frequency.

[0099] It is understandable that the process of adjusting the filter coefficients of the second low-pass filter can be referred to in the above process of adjusting the filter coefficients of the first low-pass filter, and the filter coefficients of the second low-pass filter are also adjusted to the first filter coefficients.

[0100] The working principle and process of the sensing signal processing circuit provided in the embodiments of the present invention will be described below.

[0101] For the first signal processing branch:

[0102] The first signal processing branch receives the superimposed sensing signal, which includes the first sensing signal and the second sensing signal. The superimposed sensing signal is input to the first input terminal of the first mixer 41.

[0103] When the first sensing signal is input to the first mixer 41, the output of the first mixer 41 is: a baseband signal with a frequency of 0 (that is, the baseband signal corresponding to the touch node generated by the transmitting electrode Tx1 and the current receiving electrode), and a high-frequency signal with a frequency of 2 times (the frequency is twice the first driving frequency). The baseband signal is a useful signal, and the high-frequency signal with a frequency of 2 times is a useless signal. The high-frequency signal with a frequency of 2 times can be filtered out by the first integrating circuit 42.

[0104] When the second sensing signal is input to the first mixer 41, the output of the first mixer 41 is: a difference frequency signal (frequency is the difference between the second driving frequency and the first driving frequency) and a sum frequency signal (frequency is the sum of the second driving frequency and the first driving frequency). For the first signal processing branch, both the sum frequency signal and the difference frequency signal are useless signals, and the sum frequency signal can be filtered out by the first integrating circuit 42. However, the difference frequency signal is a low-frequency signal, which is difficult to filter out by the first integrating circuit 42, thus interfering with the 0-frequency baseband signal.

[0105] In this embodiment of the invention, the second driving frequency is the sum of the first driving frequency and the first zero-point frequency of the low-pass filter. Therefore, the difference between the first driving frequency and the second driving frequency is exactly the zero-point position of the filter. Thus, the difference frequency signal (the frequency of which is the difference between the second driving frequency and the first driving frequency) will not interfere with the baseband signal at 0 frequency.

[0106] The superimposed sensing signal is processed by the first signal processing branch to finally obtain the baseband signal corresponding to the touch node generated by the transmitting electrode Tx1 and the current receiving electrode.

[0107] The working principle and process of the second signal processing branch can be referred to the first signal processing branch.

[0108] Referring to Figure 9, this embodiment of the invention also provides a touch control method, which will be described in detail below through specific steps.

[0109] Step 901: Determine the first driving frequency.

[0110] In practical implementation, the first driving frequency can be selected to drive the first transmitting electrode based on the noise distribution and interference frequency distribution in the actual application scenario. The first driving frequency should be selected as a frequency with low noise and a large frequency interval between it and the interference frequency. In other words, a frequency with less interference should be selected as the first driving frequency.

[0111] Step 902: Based on the scan time of the acquired driving signal, determine the candidate filter coefficients of the low-pass filter.

[0112] In this embodiment of the invention, after selecting the first driving frequency, the candidate filter coefficients of the low-pass filter can be determined based on the scan time required to perform a complete scan of all transmitting electrodes (i.e., the reception time of the driving signal).

[0113] In practice, different touch devices require different scan times for a single complete scan of the transmitting electrode, resulting in different low-pass filter coefficients. Candidate filter coefficients can be pre-determined based on these different scan times.

[0114] In practical implementation, a dual-frequency mutual capacitance touch device may include a clock signal generation circuit and a frequency divider. The clock signal generation circuit generates and outputs a reference clock signal, which is then input to the frequency divider. After the frequency divider divides the reference clock signal, a first driving frequency and a second driving frequency can be obtained.

[0115] There exists a scenario where the second difference between the obtained second driving frequency and the first driving frequency falls within a preset threshold range as well as the first zero-point frequency corresponding to the candidate filter coefficients. In this scenario, step 904 can be executed directly without executing step 903.

[0116] In other words, if it is determined that the first zero frequency corresponding to the second difference and the candidate filter coefficient is within a preset threshold range, then step 904 is executed; if it is determined that the first zero frequency corresponding to the second difference and the candidate filter coefficient is outside the preset threshold range, then steps 903 to 904 are executed.

[0117] Step 903: If the difference between the second difference and the first driving frequency is detected to be outside a preset threshold range, the candidate filter coefficients are adjusted to the first filter coefficients. However, there is also a scenario where the difference between the second driving frequency and the first driving frequency may not be exactly equal to the first zero-point frequency. That is, there is a certain deviation Δ1 between the difference between the second driving frequency and the first driving frequency (hereinafter referred to as the second difference) and the first zero-point frequency, and Δ1 is not equal to 0.

[0118] In some embodiments, if the deviation value Δ1 is outside a preset threshold range, the filter coefficients of the first low-pass filter are adjusted. By adjusting the filter coefficients of the first low-pass filter, the first zero-point frequency is also adjusted accordingly. After the filter coefficients of the first low-pass filter are adjusted to the first filter coefficients, the deviation between the second difference and the adjusted first zero-point frequency is updated to Δ2, and Δ2 is within the preset threshold range.

[0119] In other embodiments, if the deviation value Δ1 is not equal to 0, the filter coefficients of the first low-pass filter are adjusted. By adjusting the filter coefficients of the first low-pass filter, the first zero-point frequency is also adjusted accordingly. When the filter coefficients of the first low-pass filter are adjusted to the first filter coefficients, the deviation between the second difference and the adjusted first zero-point frequency is 0.

[0120] Step 904: Drive the first transmitting electrode with the first driving frequency and drive the second transmitting electrode with the second driving frequency.

[0121] In this embodiment of the invention, after determining the first driving frequency and the second driving frequency, the first driving frequency can be used to drive the first transmitting electrode; and the second driving frequency can be used to drive the second transmitting electrode.

[0122] In specific implementation, the execution process of steps 901 to 904 above can be referred to the relevant description of the sensing signal processing circuit in the above embodiments.

[0123] The control unit can be a chip or circuit structure with data processing capabilities, such as a controller, microcontroller, or central processing unit.

[0124] The present invention also provides a mutual capacitance touch device, including the sensing signal processing circuit provided in any of the above embodiments.

[0125] In practice, the aforementioned mutual capacitance touch device can be a dual-frequency mutual capacitance touch device.

[0126] Those skilled in the art will understand that all or part of the steps in the various methods of the above embodiments can be performed by a program instructing related hardware. The program can be stored in a computer-readable storage medium, which may include ROM, RAM, disk, or optical disk, etc.

[0127] While the present invention has been disclosed above, it is not limited thereto. Any person skilled in the art can make various modifications and alterations without departing from the spirit and scope of the invention; therefore, the scope of protection of the present invention should be determined by the scope defined in the claims.

Claims

1. A sensing signal processing circuit, characterized in that, include: A first signal processing branch and a second signal processing branch, wherein the first signal processing branch includes a first mixer and a first integrator circuit, and the second signal processing branch includes a second mixer and a second integrator circuit; wherein... The first mixer has a first input terminal for receiving a superimposed sensing signal, a second input terminal for receiving a first local oscillator signal, and an output terminal coupled to the input terminal of the first integrator circuit. The superimposed sensing signal includes a first sensing signal generated by coupling the receiving electrode to the first transmitting electrode, and a second sensing signal generated by coupling the receiving electrode to the second transmitting electrode. The first transmitting electrode receives a driving signal at a first driving frequency, and the second transmitting electrode receives a driving signal at a second driving frequency. The first driving frequency and the second driving frequency are not equal. The first integrating circuit outputs the baseband signal corresponding to the first sensing signal; The second mixer has a first input terminal for receiving the superimposed sensing signal, a second input terminal for receiving the second local oscillator signal, and an output terminal coupled to the input terminal of the second integrator circuit; the frequency of the first local oscillator signal is equal to the first driving frequency, and the frequency of the second local oscillator signal is equal to the second driving frequency; The second integrating circuit outputs a baseband signal corresponding to the second sensing signal; both the first integrating circuit and the second integrating circuit include a low-pass filter, and the second driving frequency is determined by the first driving frequency and the first zero-point frequency of the low-pass filter.

2. The sensing signal processing circuit as described in claim 1, characterized in that, The second driving frequency is the sum of the first driving frequency and the first zero-point frequency.

3. The sensing signal processing circuit as described in claim 2, characterized in that, The filter coefficients of the low-pass filter are the first filter coefficients; when the filter coefficients are the first filter coefficients, the offset between the first zero-point frequency and the first difference is within a preset threshold range, and the first difference is the difference between the second driving frequency and the first driving frequency.

4. The sensing signal processing circuit as described in claim 3, characterized in that, Also includes: The control unit is coupled to both low-pass filters and is adapted to adjust the filter coefficients of both low-pass filters to the first filter coefficients.

5. The sensing signal processing circuit as described in claim 4, characterized in that, The control unit is adapted to: determine candidate filter coefficients of the two low-pass filters based on the scan time of the drive signal, the candidate filter coefficients corresponding to candidate zero frequencies; and adjust the candidate filter coefficients to the first filter coefficients when the difference between the second difference and the first drive frequency is outside the threshold range. If the difference between the first difference and the first driving frequency is detected to be within the threshold range, the candidate filter coefficient is determined to be the first filter coefficient. The second difference is the difference between the second driving frequency and the candidate zero frequency.

6. The sensing signal processing circuit as described in claim 1, characterized in that, The first zero-point frequency is any zero-point frequency of the low-pass filter.

7. The sensing signal processing circuit as described in claim 1, characterized in that, The first zero-point frequency is the zero-point frequency with the smallest frequency value of the low-pass filter.

8. The sensing signal processing circuit as described in claim 1, characterized in that, The low-pass filter has at least two zero frequencies; the first zero frequency is any zero frequency among all the zero frequencies of the low-pass filter that is free from interference.

9. A touch control method, characterized in that, The touch method, applicable to the sensing signal processing circuit as described in claims 1 to 8, includes: Determine the first driving frequency; Based on the scan time of the acquired driving signal, candidate filter coefficients of the low-pass filter are determined; the candidate filter coefficients correspond to candidate zero frequencies. If the difference between the second difference and the first driving frequency is detected to be outside a preset threshold range, the candidate filter coefficients are adjusted to the first filter coefficients; and when the filter coefficients of the low-pass filter are the first filter coefficients, the offset between the first zero frequency and the first difference is within a preset threshold range, the first difference is the difference between the second driving frequency and the first driving frequency, and the second difference is the difference between the second driving frequency and the candidate zero frequency. The first transmitting electrode is driven using the first driving frequency, and the second transmitting electrode is driven using the second driving frequency.

10. A mutual capacitance touch device, characterized in that, It includes a cross-arranged transmitting electrode and a receiving electrode. The first transmitting electrode in the transmitting electrode receives a driving signal at a first driving frequency, and the second transmitting electrode in the transmitting electrode receives a driving signal at a second driving frequency. The first driving frequency and the second driving frequency are not equal. And, the sensing signal processing circuit as described in any one of claims 1 to 8.

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