Touch detection method, readout circuit and electronic device

Abstract

This application discloses a touch detection method, readout circuit, and electronic device to solve the problem of balancing signal-to-noise ratio, frame rate, and circuit complexity in high-channel-count touch detection. The method includes: generating and applying a code-frequency hybrid driving signal; acquiring a sensed signal and converting it into a digital signal; performing double cross-correlation demodulation on the digital signal, and obtaining accurate touch information by calculating its cross-correlation values ​​with in-phase and quadrature reference signals and summing the squares of the two values. The circuit includes corresponding functional modules. This invention improves the signal-to-noise ratio through code-frequency hybridization and simultaneously completes decoding and frequency discrimination while eliminating phase errors through double cross-correlation demodulation, achieving a balance between high frame rate and low circuit complexity.

Description

Technical Field

[0001] This application relates to the field of touch display technology, and in particular to a touch detection method, a readout circuit, and an electronic device. Background Technology

[0002] Touch display panels, with their intuitive human-computer interaction features, have become a core component in the consumer electronics field. With the rapid expansion of the market for large-size, high-resolution touch applications such as interactive whiteboards and digital signage, the continuous increase in panel size poses unprecedented challenges to touch detection technology. Specifically, these challenges manifest as follows: the number of touch channels increases exponentially, leading to a relatively narrower system bandwidth and a significant increase in electrode load impedance, resulting in severe attenuation of the useful signal amplitude. Simultaneously, in large-size display applications, the interference of display driving noise on touch signals (display noise) is significantly enhanced, further deteriorating the overall signal-to-noise ratio (SNR).

[0003] To cope with the pressure brought by the increase in the number of channels, the traditional serial scanning scheme was widely used in the industry due to its simple architecture. However, this scheme has an inherent flaw: as the number of channels increases, in order to maintain a certain frame rate, the signal integration time allocated to each channel must be compressed, resulting in a sharp drop in the signal-to-noise ratio (SNR); if the SNR is to be maintained, the integration time must be extended, which results in a significant reduction in the frame rate. Therefore, in application scenarios with a large number of channels, the serial scheme is caught in a fundamental contradiction where SNR and frame rate cannot be simultaneously achieved.

[0004] To overcome the aforementioned bottlenecks, existing technologies have shifted towards parallel-driven approaches, primarily including code division parallelism (CDM) and frequency division parallelism (FDM). However, both approaches have their limitations:

[0005] Code Division Parallelism (CDM): Its performance is limited by the length of the orthogonal codes. When the number of channels increases significantly, the required orthogonal code length also increases dramatically, leading to a longer signal transmission period and causing a decrease in frame rate.

[0006] Frequency Division Parallel (FDM): Its performance is limited by the total system bandwidth. Increasing the number of channels means that more carrier frequencies need to be allocated, which can lead to excessively dense frequency spacing within a fixed bandwidth. This not only exacerbates inter-frequency interference but also increases the design difficulty and cost of the receiver's filtering and frequency discrimination circuits, making it difficult to maintain an ideal signal-to-noise ratio.

[0007] Furthermore, both CDM and FDM typically require a step-by-step process at the receiver: frequency discrimination (separating different frequencies) followed by decoding (separating different codes for the same frequency). This approach often relies on the coordinated operation of multiple discrete functional circuits (such as filter banks and correlator banks), which not only significantly increases the overall circuit complexity, power consumption, and physical size of the system but also incurs additional hardware costs.

[0008] In summary, existing technologies struggle to achieve a balance between high signal-to-noise ratio, high frame rate, low system complexity, and low cost in large-size, high-channel-count touch applications. Therefore, there is an urgent need in this field for an innovative touch detection architecture and method that can fundamentally solve these multi-objective optimization challenges to meet the pressing needs of next-generation large-size, high-performance touch interaction applications. Summary of the Invention

[0009] This application proposes a touch detection method, readout circuit, and electronic device to solve the problem of balancing high signal-to-noise ratio, high frame rate, and low circuit complexity in high-channel-number touch detection.

[0010] In a first aspect, embodiments of this application provide a touch detection method, the method comprising:

[0011] A code-frequency hybrid driving signal is generated; the driving signal includes: grouping the transmission channels, using orthogonal carriers of different frequencies for different groups, and modulating the transmission channels within the same group using orthogonal coding sequences;

[0012] The driving signals are applied in parallel to multiple transmit ports;

[0013] Analog induction signals generated by the coupling of the drive signal are acquired from multiple receiving ports;

[0014] The analog sensing signal is amplified and converted from analog to digital to obtain a digital sensing signal;

[0015] Performing a double cross-correlation demodulation operation on the digital sensing signal includes:

[0016] Calculate the cross-correlation values ​​between the digital inductive signal and the in-phase reference signal and the quadrature reference signal, respectively;

[0017] Calculate the sum of squares for two cross-correlated values.

[0018] In one embodiment, the quadrature reference signal and the in-phase reference signal have a fixed phase difference of 90 degrees.

[0019] In one embodiment, the grouping of the transmission channels specifically involves dividing them into K frequency groups, each containing N channels, and generating the code-frequency hybrid driving signal using K carriers of different frequencies and orthogonal codes of length N.

[0020] The orthogonal code is a Hadamard matrix sequence or a maximum length sequence.

[0021] In one embodiment, the dual cross-correlation demodulation operation is performed in the digital domain, and the in-phase reference signal and the quadrature reference signal are 1-bit digital signals.

[0022] In one embodiment, the orthogonal coding sequence used for channels within the same group is a binary phase modulation signal.

[0023] Secondly, embodiments of this application also provide a touch readout circuit for implementing the touch detection method as described in any embodiment of the first aspect, comprising: a transmission channel module for generating a code-frequency hybrid driving signal; the driving signal comprising: grouping the transmission channels, using orthogonal carriers of different frequencies for different groups, and modulating the transmission channels within the same group using an orthogonal coding sequence; having multiple transmission ports for parallel output of the driving signal. A receiving channel module having multiple receiving ports for acquiring analog sensing signals, amplifying and converting the analog sensing signals to digital signals, and outputting digital sensing signals. A dual cross-correlation demodulation module, the input of which is connected to the output of the receiving channel module, for performing dual cross-correlation demodulation on the digital sensing signals, the demodulation operation comprising: calculating the cross-correlation values ​​of the digital sensing signals with the in-phase reference signal and the quadrature reference signal respectively, calculating the sum of squares of the two cross-correlation values, and outputting detection information characterizing the signal strength.

[0024] In one embodiment, the transmit channel module includes: a digital waveform generation unit for generating a digital sine wave signal corresponding to a frequency group; a digital-to-analog converter unit, whose input is connected to the digital waveform generation unit, for converting the digital sine wave signal into an analog signal; and a phase encoding unit, whose input is connected to the digital-to-analog converter unit, for performing in-phase or out-of-phase gating on the analog signal according to the orthogonal encoding sequence to generate the drive signal.

[0025] In one embodiment, the receiving channel module includes: a charge amplifier, whose input is connected to the receiving port, for performing charge-to-voltage conversion and primary amplification on the analog inductive signal; a differential amplifier, whose input is connected to the output of the charge amplifier, for performing differential operations on adjacent channel signals to suppress common-mode noise; and a programmable gain amplifier, whose input is connected to the output of the differential amplifier, for amplifying the signal with adjustable gain and outputting it to the analog-to-digital converter.

[0026] In one embodiment, the dual cross-correlation demodulation module includes digital logic circuitry for performing multiply-accumulate operations and sum-of-squares operations.

[0027] In one embodiment, the dual cross-correlation demodulation module performs cross-correlation operations through a multiplexer and an accumulator.

[0028] The above-described technical solutions adopted in the embodiments of this application can achieve the following beneficial effects:

[0029] The technical solution adopted in this application, through an innovative combination of code-frequency hybrid modulation and dual cross-correlation demodulation, achieves several significant beneficial effects. First, at the signal transmitting end, the code-frequency hybrid modulation technology, through dual orthogonal design in both the frequency and coding dimensions, enables limited system bandwidth and a shorter orthogonal coding length to support the parallel driving of a large number of channels. This design fundamentally solves the problems of frame rate reduction due to excessive coding length in traditional code division multiplexing (CDM) as the number of channels increases, and signal-to-noise ratio degradation due to frequency interference in frequency division multiplexing (FDM) when channels are dense. Thus, in high-channel-count, large-size touch applications, both high signal-to-noise ratio and high refresh rate are simultaneously achieved. Second, at the signal receiving and processing end, the dual cross-correlation demodulation technology, by introducing two reference signals with a 90-degree phase difference for cross-correlation calculation and performing a sum-of-squares operation on the results, can accurately eliminate phase shifts introduced by factors such as the RC delay of the touch panel itself, accurately restore the amplitude information of the touch signal, and ensure detection accuracy. More importantly, this method utilizes the frequency selection and code matching characteristics of cross-correlation operations to simultaneously complete signal decoding (separating channels with the same frequency but different codes) and frequency discrimination (separating carriers of different frequencies) in a single-step digital operation, eliminating the complex discrete circuits required by traditional schemes that first filter and divide the frequency, and then decode separately. This greatly simplifies the receiver hardware architecture, reduces the use of analog circuits, and lowers system power consumption, area, and overall cost, which is particularly beneficial for chip integration. In summary, the technical solution of this application provides a high-performance, highly integrated, and low-cost systematic solution for large-size, high-precision touch detection, effectively overcoming the core technical challenges that have long faced in this field. Attached Figure Description

[0030] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0031] Figure 1-1 This is a system architecture diagram of the touch readout circuit provided in the embodiments of this application;

[0032] Figure 1-2A flowchart of a touch detection method provided in an embodiment of this application;

[0033] Figure 2-1 A schematic diagram of a touch readout circuit provided in an embodiment of this application;

[0034] Figure 2-2 This is a schematic diagram of the transmission channel circuit provided in an embodiment of this application;

[0035] Figure 3 This is a schematic diagram of the receiving channel circuit provided in an embodiment of this application;

[0036] Figure 4 This is a schematic diagram illustrating the implementation structure of the dual cross-correlation detection circuit provided in an embodiment of this application. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] The technical solutions provided by the various embodiments of this application are described in detail below with reference to the accompanying drawings.

[0039] Figure 1-1 This is a system architecture diagram of the touch readout circuit provided in an embodiment of this application.

[0040] like Figure 1-1 As shown, the system mainly includes: a transmit channel (TX) 107, a receive channel (RX) 106, an analog-to-digital converter (ADC) 103, a dual cross-correlation array 104, and a microcontroller unit (MCU) 105. In one specific embodiment, the system is configured to drive 32 transmit channels and receive signals from 64 receive channels. The transmit channel 107 generates a quadrature signal with mixed code and frequency to drive all the transmit electrodes of the touch panel. The induced charge signal generated on the touch panel due to touch is differentially amplified by the receive channel 106 and then converted into digital code by the ADC 103. The dual cross-correlation array 104 performs a dual cross-correlation operation on the digital signal to obtain the capacitance change information of the entire panel, and finally sends it to the MCU 105 for processing to obtain the touch point coordinates.

[0041] Figure 1-2 This is a flowchart of a touch detection method according to an embodiment of this application.

[0042] In a first aspect, embodiments of this application provide a touch detection method, the method comprising: steps 110-150.

[0043] Step 110: Generate a code-frequency hybrid driving signal; the driving signal includes: grouping the transmission channels, using orthogonal carriers of different frequencies for different groups, and modulating the transmission channels within the same group using orthogonal coding sequences.

[0044] The "code-frequency mixing" in this step refers to the technique of using both frequency orthogonality and code orthogonality to distinguish different transmission channels.

[0045] Specifically, "grouping the transmission channels" means dividing the total number of M transmission channels into K frequency groups, each containing N channels, satisfying M = K × N. "Using different orthogonal carriers of different frequencies for different groups" means assigning K orthogonal (i.e., carrier frequencies are different and reasonably spaced to avoid interference) sine or square waves as carrier signals to the K different frequency groups. "Modulating the transmission channels within the same group using orthogonal coding sequences" means using a set of orthogonal coding sequences (e.g., +1 / -1 sequences) of length N to modulate the carriers (e.g., binary phase-shift keying modulation) for each of the N channels sharing the same carrier frequency, making the signals of each channel within the same group distinguishable in the coding domain. In this way, a limited number of K frequency points and N-bit short codes can be used to uniquely identify and drive a large number of M channels, achieving parallel driving. The signal s represents a code-frequency mixture. u,k (t) can be expressed as:

[0046] Formula 1

[0047] Where cu(t) is the encoding sequence, f k For carrier frequency.

[0048] In one embodiment, the quadrature reference signal and the in-phase reference signal have a fixed phase difference of 90 degrees.

[0049] This is a crucial prerequisite for achieving "dual cross-correlation demodulation" to eliminate phase shift. At the receiver, two local reference signals need to be generated for each transmit channel: one "in-phase reference signal" that is in phase with the theoretical transmit signal, and another "quadrature reference signal" that is 90 degrees out of phase with it. These two signals will be used for subsequent cross-correlation calculations. Let the received signal components be:

[0050] Formula 2

[0051] Two reference signals are generated at the receiving end: an in-phase signal and a... and orthogonal signals (Phase difference 90°).

[0052] In one embodiment, the grouping of the transmission channels specifically involves dividing them into K frequency groups, each containing N channels, and generating the code-frequency hybrid driving signal using K carriers of different frequencies and orthogonal codes of length N.

[0053] The orthogonal code is a Hadamard matrix sequence or a maximum length sequence.

[0054] For example, in a system with 32 transmit channels (M=32), it can be divided into 4 frequency groups (K=4), with 8 channels in each group (N=8). The system uses 4 carriers at different frequencies (e.g., f1, f2, f3, f4), and modulates the carriers at each frequency using the rows (or columns) of an 8th-order Hadamard matrix as 8 mutually orthogonal coded sequences. Hadamard codes and maximum-length sequences (m-sequences) are two commonly used binary orthogonal codes with good autocorrelation and cross-correlation properties, making them very suitable for this type of coded modulation system. With the architecture of this embodiment, the system only needs to manage 4 frequency points and short codes of length 8 to drive all 32 channels in parallel, effectively balancing system bandwidth, signal orthogonality, and processing complexity.

[0055] In one embodiment, the orthogonal coding sequence used for channels within the same group is a binary phase modulation signal.

[0056] This means that the value of the orthogonal coded sequence is typically +1 or -1 (corresponding to binary '0' and '1'). In circuit implementation, when the code is +1, a carrier signal in phase is output; when the code is -1, a carrier signal out of phase (180-degree phase shift) is output. This binary phase modulation (BPSK) is simple to implement, has good noise immunity, and is a preferred modulation method. The binary phase modulation can be specifically implemented through a phase coding mechanism: when the code value is +1, a signal in phase with the carrier is output; when the code value is -1, a signal out of phase with the carrier is output.

[0057] Step 120: Apply the driving signals in parallel to multiple transmit ports.

[0058] The transmitting port is the interface that is physically connected to the driving electrodes of the touch sensor (such as a touch panel). The multi-channel driving signals generated in step 110, which have undergone code-frequency mixing modulation, are simultaneously (i.e., in parallel) output and applied to each driving electrode of the touch sensor through their respective transmitting ports in this step. This parallel driving method is the basis for achieving high frame rate detection with a large number of channels.

[0059] Step 130: Acquire the analog induction signal generated by the coupling of the drive signal from multiple receiving ports.

[0060] The receiving port is the interface physically connected to the sensing electrode of the touch sensor. When a finger or stylus touches the panel, it changes the mutual capacitance at the intersection of the driving electrode and the sensing electrode. Therefore, the driving signal applied to the driving electrode is coupled to the sensing electrode through the changing mutual capacitance, forming an induced current signal containing touch information. This step involves synchronously acquiring these weak analog induced current signals from each receiving port. This step corresponds to the process of receiving the sensing signal output by the touch sensor.

[0061] Step 140: Amplify and convert the analog sensing signal to digital signal to obtain digital sensing signal.

[0062] The acquired raw analog induction signal is very weak and susceptible to noise interference. This step first uses analog front-end circuits such as charge amplifiers and programmable gain amplifiers to convert the micro-current signal into a voltage signal, followed by primary amplification and filtering (i.e., "amplification") to increase signal strength and suppress some noise. Then, an analog-to-digital converter (ADC) converts the processed analog voltage signal into a discrete digital signal for subsequent digital signal processing.

[0063] Step 150: Perform double cross-correlation demodulation on the digital sensing signal, including:

[0064] Calculate the cross-correlation values ​​between the digital inductive signal and the in-phase reference signal and the quadrature reference signal, respectively.

[0065] Calculate the sum of squares for two cross-correlated values.

[0066] This application embodiment is used to accurately calculate the signal strength (i.e., capacitance change) corresponding to each transmission channel from a mixed digital sensing signal. The key is that the double cross-correlation operation here is performed "for each transmission channel". For a specific transmission channel to be demodulated, the receiver needs to generate a local orthogonal coding sequence and carrier frequency that are exactly the same as those used in the modulation stage of that channel, and accordingly generate two reference signals with a 90-degree phase difference (i.e., an in-phase reference signal and a quadrature reference signal).

[0067] First, the received digital sensing signal (including the mixed signal of all channels) is subjected to a first cross-correlation operation with the in-phase reference signal corresponding to the channel to obtain a first cross-correlation value; then, a second cross-correlation operation is performed with the quadrature reference signal corresponding to the channel to obtain a second cross-correlation value.

[0068] Perform cross-correlation calculations separately:

[0069] Cross-correlation with in-phase signals:

[0070] Formula 3

[0071] Cross-correlation with orthogonal signals:

[0072] Formula 4

[0073] The resistive-capacitive (RC) characteristics of the touch panel cause an unknown phase shift φ in the signal. These two cross-correlation values ​​are proportional to cos(φ) and sin(φ), respectively.

[0074] Then, perform a sum of squares operation on these two cross-correlated values. According to the trigonometric identities...

[0075] sin²(φ) ​​+ cos²(φ) = 1 (Formula 5)

[0076] This calculation will completely eliminate the effect of the phase shift φ, yielding a quantity that is only proportional to the product of the original transmitted signal amplitude and the received signal amplitude, namely A. i B i T / 2, which satisfies the following relation:

[0077] Formula 6

[0078] in, To obtain the cross-correlation results between the received signal and the in-phase reference signal, To obtain the cross-correlation result between the received signal and the quadrature reference signal, the quadrature reference signal and the in-phase reference signal have a 90° phase difference; A i B i denoted by and , respectively, and T represents the integration time.

[0079] This quantity directly and accurately characterizes the change in mutual capacitance between the transmitting channel and the receiving port, i.e., the contact charge information. The core advantage of this operation lies in its ability to eliminate the unknown phase shift φ introduced by the resistive-capacitive (RC) characteristics of the signal during transmission. Traditional demodulation methods suffer from amplitude detection errors due to this phase shift. This method calculates the sum of squares of two positively correlated values, based on the trigonometric function principle (sin²φ + cos²φ = 1). This operation eliminates the influence of the phase shift φ through the sum of squares, obtaining information related to the signal amplitude.

[0080] In one embodiment, the dual cross-correlation demodulation operation is performed in the digital domain, and the in-phase reference signal and the quadrature reference signal are 1-bit digital signals.

[0081] This embodiment places demodulation entirely in the digital domain, with the reference signal being only a digital signal in two states: 0 and 1. This simplifies the core cross-correlation multiplication operation to an operation that selects whether to accumulate (or subtract) the input signal based on whether the reference signal is 0 or 1. This can be efficiently implemented using simple digital logic such as multiplexers and accumulators, greatly reducing hardware complexity and power consumption. In this embodiment, the reference signal is generated by digital circuitry and has only two logic states: 0 and 1. Therefore, the cross-correlation multiplication operation can be simplified to a gating operation implemented by a multiplexer, while the integration operation is completed by an accumulator, thus significantly reducing hardware complexity.

[0082] Figure 2-1 This is a schematic diagram of a touch-sensitive readout circuit according to an embodiment of this application.

[0083] Secondly, embodiments of this application also provide a touch readout circuit for implementing the touch detection method as described in any embodiment of the first aspect, comprising:

[0084] The transmission channel module 21 is used to generate a code-frequency hybrid driving signal; the driving signal includes: grouping the transmission channels, using orthogonal carriers of different frequencies for different groups, and modulating the transmission channels within the same group using an orthogonal coding sequence; it has multiple transmission ports for parallel output of the driving signal.

[0085] Specifically, the circuit first generates a carrier signal of the corresponding frequency according to the grouping and frequency allocation strategy. The driving signal is generated by grouping the transmission channels, using orthogonal carriers of different frequencies for different groups, and modulating the transmission channels within the same group using orthogonal coding sequences.

[0086] The receiving channel module 22 has multiple receiving ports for acquiring analog sensing signals, amplifying and converting the analog sensing signals to digital signals, and outputting digital sensing signals.

[0087] The receiving channel module is responsible for processing the weak signals transmitted from the sensing electrodes of the touch sensor. It first synchronously acquires the analog induced current signal generated by the coupling of the drive signal through multiple receiving ports, and then converts the analog signal into a digital induced signal suitable for digital processing through the internally integrated amplification and analog-to-digital conversion function chain.

[0088] The dual cross-correlation demodulation module 23 has its input end connected to the output end of the receiving channel module. It is used to perform dual cross-correlation demodulation operation on the digital sensing signal. The demodulation operation includes: calculating the cross-correlation values ​​of the digital sensing signal with the in-phase reference signal and the quadrature reference signal respectively, and performing a sum of squares operation on the two cross-correlation values ​​to output detection information characterizing the signal strength.

[0089] It receives digital sensing signals from the receiving channel module and performs a specific dual cross-correlation demodulation operation for each transmitting channel. This operation includes: calculating the cross-correlation values ​​between the digital sensing signal and the corresponding in-phase reference signal and quadrature reference signal for that channel; then performing a sum-of-squares operation on the two cross-correlation values. This sum-of-squares result eliminates phase shifts in signal transmission, obtaining coupling strength information between each transmit-receive channel pair.

[0090] In one embodiment, the transmission channel module includes:

[0091] The digital waveform generation unit is used to generate digital sine wave signals corresponding to the frequency group.

[0092] The digital-to-analog converter unit, whose input is connected to the digital waveform generation unit, is used to convert the digital sine wave signal into an analog signal.

[0093] A phase encoding unit, whose input is connected to the digital-to-analog converter, is used to perform in-phase or out-of-phase gating on the analog signal according to the orthogonal encoding sequence to generate the driving signal.

[0094] The transmission channel circuit structure is as follows Figure 2-2 As shown in the diagram, the circuit first outputs a digitally encoded signal with the corresponding frequency and its inverse from a direct digital synthesizer (DDS) 201. The digital code is then converted into a stepped waveform by a digital-to-analog converter (DAC) 202, and high-frequency components are filtered out by a low-pass filter (LPF) 203 to obtain a high-quality sine wave signal, which is then output by a buffer 204. Finally, a phase encoding mechanism is employed, where the phase of the signal represents the quadrature encoded value.

[0095] It should be noted that this embodiment Figure 2-1 The “digital waveform generation unit,” “digital-to-analog conversion unit,” and “phase encoding unit” refer to the functional divisions within the transmission channel module. In actual circuit implementation, these functional units can be implemented by specific electronic components. For example, the digital waveform generation unit can be implemented by a direct digital frequency synthesizer (DDS); the digital-to-analog conversion unit can be implemented by a digital-to-analog converter (DAC); and the phase encoding unit can be implemented by logic circuitry containing multiplexers or switches. Figure 2-2 The circuit shown (DDS 201, DAC 202, LPF 203, buffer 204 and phase encoding control logic) is a specific hardware implementation scheme for the above three functional units.

[0096] This embodiment provides a specific circuit implementation of the transmit channel module. The circuit first uses a direct digital synthesizer (DDS) as the digital waveform generation unit, outputting a digitally encoded signal with the corresponding frequency and its inverse. A digital-to-analog converter (DAC) is used as the digital-to-analog conversion unit to convert the digital code into a stepped waveform. A low-pass filter (LPF) then filters out high-frequency components to obtain a high-quality sine wave signal. Finally, a phase encoding mechanism is employed. The phase encoding unit controls the selection of in-phase or in-phase signals according to an orthogonal encoding sequence to achieve modulation. A code value of +1 outputs an in-phase signal, and a code value of -1 outputs an in-phase signal, thereby generating the final drive signal.

[0097] In one embodiment, the receiving channel module includes:

[0098] A charge amplifier, whose input is connected to the receiving port, is used to perform charge-to-voltage conversion and primary amplification on the analog induced signal.

[0099] A differential amplifier, whose input is connected to the output of the charge amplifier, is used to perform differential operations on adjacent channel signals to suppress common-mode noise.

[0100] A programmable gain amplifier, whose input is connected to the output of the differential amplifier, is used to amplify the signal with adjustable gain and output it to the analog-to-digital converter.

[0101] The receiving channel adopts a three-level signal processing architecture, such as Figure 3 As shown, the front-end charge amplifier 301 converts the induced charge on the panel into a voltage signal and completes the primary amplification; the differential processing stage 302 effectively suppresses common-mode noise by subtracting signals from adjacent channels; and the final stage is equipped with a programmable gain amplifier 303 to adapt to the amplitude of the panel signal with different load characteristics.

[0102] Accordingly, the "charge amplifier", "differential amplifier" and "programmable gain amplifier" described in this embodiment define the core signal processing link of the receiving channel module. Figure 3 The circuit shown provides a specific implementation of this link: a front-end charge amplifier 301 implements the function of the charge amplifier; a differential processing stage 302 implements the function of the differential amplifier; and a programmable gain amplifier 303 implements the function of the programmable gain amplifier. The analog-to-digital converter (ADC) can be as follows: Figure 1-1 The device shown may be a standalone unit or integrated into a subsequent processing unit.

[0103] The analog-to-digital converter (ADC) uses time-division multiplexing to sample signals from multiple receiving channels. This embodiment details the preferred architecture of the receiving channel module.

[0104] This embodiment details the preferred architecture of the receiving channel module. The module employs a three-stage signal processing architecture: a front-end charge amplifier converts the panel-induced charge into a voltage signal and performs primary amplification; a differential processing stage effectively suppresses common-mode noise by subtracting signals from adjacent channels; and a final stage is configured with a programmable gain amplifier (PGA) to adapt to the amplitude of panel signals with different load characteristics. The analog-to-digital converter (ADC) can use time-division multiplexing to sample signals from multiple receiving channels.

[0105] In one embodiment, the dual cross-correlation demodulation module includes digital logic circuitry for performing multiply-accumulate operations and sum-of-squares operations.

[0106] The dual cross-correlation detection circuit includes digital logic circuitry configured to perform decoding and frequency discrimination operations for all transmission channels in parallel. This embodiment defines the hardware nature of the dual cross-correlation demodulation module. This module is composed of digital logic circuitry configured to perform decoding and frequency discrimination operations for all transmission channels in parallel. The operations include multiplying and accumulating the received digital signal with the corresponding in-phase reference code and quadrature reference code, and calculating the sum of squares of the two accumulation results.

[0107] In one embodiment, the dual cross-correlation demodulation module performs cross-correlation operations through a multiplexer and an accumulator.

[0108] like Figure 4 As shown, to ensure accuracy and reduce power consumption, the double cross-correlation operation is implemented in the digital domain. The reference signal is generated in the digital circuit and has only two states: 0 and 1. Therefore, the cross-correlation multiplication operation can be transformed into a multiplexer gating operation, and the integration operation can be transformed into an accumulator accumulation operation. This all-digital structure significantly reduces hardware complexity.

[0109] It should also be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0110] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” “the,” and “the” used herein may also include the plural forms. It should be further understood that the word “comprising” as used in this application’s specification means the presence of the stated features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when an element is “connected” or “coupled” to another element, it may be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, the terms “connected” or “coupled” as used herein may include wireless connections or wireless coupling.

[0111] In the description of this application, it should be understood that the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances. Furthermore, in the description of this application, unless otherwise stated, "multiple" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship.

[0112] Those skilled in the art will understand that, unless otherwise defined, all terms used herein (including technical, terminological, and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0113] The above description is merely an embodiment of this application and is not intended to limit the scope of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of the claims of this application.

Claims

1. A touch detection method, characterized in that, The method includes: A code-frequency hybrid driving signal is generated; the driving signal includes: grouping the transmission channels, using orthogonal carriers of different frequencies for different groups, and modulating the transmission channels within the same group using orthogonal coding sequences; The driving signals are applied in parallel to multiple transmit ports; Analog induction signals generated by the coupling of the drive signal are acquired from multiple receiving ports; The analog sensing signal is amplified and converted from analog to digital to obtain a digital sensing signal; Performing a double cross-correlation demodulation operation on the digital sensing signal includes: Calculate the cross-correlation values ​​between the digital inductive signal and the in-phase reference signal and the quadrature reference signal, respectively; Calculate the sum of squares for two cross-correlated values.

2. The touch detection method of claim 1, wherein, The quadrature reference signal and the in-phase reference signal have a fixed phase difference of 90 degrees.

3. The touch detection method of claim 1, wherein, The specific method of grouping the transmission channels is as follows: dividing them into K frequency groups, each containing N channels, and generating the code-frequency hybrid driving signal using K carriers of different frequencies and orthogonal codes of length N; The orthogonal code is a Hadamard matrix sequence or a maximum length sequence.

4. The touch detection method of claim 1, wherein, The dual cross-correlation demodulation operation is performed in the digital domain, and the in-phase reference signal and the quadrature reference signal are 1-bit digital signals.

5. The touch detection method of claim 1, wherein, The orthogonal coding sequence used for channels within the same group is a binary phase-modulated signal.

6. A touch-sensitive readout circuit, characterized in that, A method for implementing the touch detection method as described in any one of claims 1-5, comprising: The transmit channel module is used to generate a code-frequency hybrid drive signal; the drive signal includes: grouping the transmit channels, using orthogonal carriers of different frequencies for different groups, and modulating the transmit channels within the same group using an orthogonal coding sequence; It has multiple transmit ports for parallel output of the drive signals; The receiving channel module has multiple receiving ports for acquiring analog sensing signals, amplifying and converting the analog sensing signals to digital signals, and outputting digital sensing signals. The dual cross-correlation demodulation module has its input end connected to the output end of the receiving channel module. It is used to perform dual cross-correlation demodulation operation on the digital sensing signal. The demodulation operation includes: calculating the cross-correlation values ​​of the digital sensing signal with the in-phase reference signal and the quadrature reference signal respectively, calculating the sum of squares of the two cross-correlation values, and outputting detection information characterizing the signal strength.

7. The touch-sensitive readout circuit according to claim 6, characterized in that, The transmission channel module includes: The digital waveform generation unit is used to generate digital sine wave signals corresponding to the frequency group; A digital-to-analog converter unit, whose input terminal is connected to the digital waveform generation unit, is used to convert the digital sine wave signal into an analog signal; A phase encoding unit, whose input is connected to the digital-to-analog converter, is used to perform in-phase or out-of-phase gating on the analog signal according to the orthogonal encoding sequence to generate the driving signal.

8. The touch-sensitive readout circuit according to claim 6, characterized in that, The receiving channel module includes: A charge amplifier, whose input is connected to the receiving port, is used to perform charge-to-voltage conversion and primary amplification on the analog induced signal; A differential amplifier, whose input is connected to the output of the charge amplifier, is used to perform differential operations on adjacent channel signals to suppress common-mode noise. A programmable gain amplifier, whose input is connected to the output of the differential amplifier, is used to amplify the signal with adjustable gain and output it to the analog-to-digital converter.

9. The touch-sensitive readout circuit according to claim 6, characterized in that, The dual cross-correlation demodulation module includes digital logic circuits for performing multiply-accumulate operations and sum-of-squares operations.

10. The touch-sensitive readout circuit according to claim 6, characterized in that, The dual cross-correlation demodulation module performs cross-correlation operations through a multiplexer and an accumulator.

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