Systems, methods, and apparatus for capacitive sensing with sinusoidal demodulation

Abstract

Systems, methods, and devices improve sensitivity of a capacitive sensor. A device can include an attenuator configured to receive an input from at least one sensing electrode of a capacitive sensing device. The attenuator can be included in a sensing channel of the capacitive sensor. The device can further include a signal generator coupled to an input of the attenuator. The signal generator can include one or more processors configured to generate a sinusoidal signal based at least in part on one or more noise characteristics of a scan sequence associated with one or more transmit electrodes of the capacitive sensing device, and provide the sinusoidal signal to the input of the attenuator.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority under U.S. Patent Application No. 63 / 006,298, filed April 7, 2020, section 119e of the U.S. Patent Act, the entire provisions of which are incorporated herein by reference for all purposes. Technical Field

[0003] This disclosure generally relates to capacitive sensors, and more specifically, to improving the external noise immunity of such capacitive sensors. Background Technology

[0004] Devices and systems (e.g., mobile communication devices) may include various input devices (e.g., touchscreens and buttons). Touchscreens and buttons may utilize one or more sensing modes to receive input from a physical entity (e.g., a user of the mobile communication device). An example of such a mode could be capacitive sensing, where the touchscreen or button may include conductive elements that can be used to obtain various capacitance measurements. For example, a touchscreen may include an array of electrodes, and a touchscreen controller may be used to measure the capacitance associated with those electrodes. However, many capacitive sensors remain limited because they are susceptible to external noise, such as the sensitivity of their sensing channels to harmonics of the operating frequency. Attached Figure Description

[0005] Figure 1A An example of a device for enhancing the noise immunity of a capacitive sensor, configured according to some embodiments, is shown.

[0006] Figure 1B Another example of a device for enhancing the noise immunity of a capacitive sensor, configured according to some embodiments, is shown.

[0007] Figure 2 An example of an improved charge-time converter configured according to some embodiments is shown.

[0008] Figure 3A An example of a variable gain attenuator configured according to some embodiments is shown.

[0009] Figure 3B Another example of a variable gain attenuator configured according to some embodiments is shown.

[0010] Figure 3C Another example of a variable gain attenuator configured according to some embodiments is shown.

[0011] Figure 4 Another example of an improved charge-time converter configured according to some embodiments is shown.

[0012] Figure 5A An example implementation of a variable gain attenuator configured according to some embodiments is shown.

[0013] Figure 5B An example implementation of an attenuator configured according to some embodiments is shown.

[0014] Figure 6 An example of a variable gain attenuator configured according to some embodiments is shown.

[0015] Figure 7 An example of a system for enhancing the noise immunity of a capacitive sensor, configured according to some embodiments, is shown.

[0016] Figure 8 A flowchart illustrating an example of a method for scanning using a sensing slot of a capacitive sensor, implemented according to some embodiments, is shown.

[0017] Figure 9 A flowchart is shown as another example of a method for using multiple scanning slot scanning panels or other sensor arrays, implemented according to some embodiments.

[0018] Figure 10 A flowchart is shown as an additional example of a method for enhancing the sensitivity of a capacitive sensor by providing phase calibration of the transmitted signal, implemented according to some embodiments.

[0019] Figure 11A and Figure 11B The illustration shows examples of attenuator inputs and outputs with different numbers of gain steps, implemented according to some embodiments.

[0020] Figure 12A and Figure 12B An illustration shows an example of a signal sensed by one or more sensing channels, implemented according to some embodiments. Detailed Implementation

[0021] The following description elaborates on numerous specific details to provide a thorough understanding of the proposed ideas. The proposed ideas can be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail to avoid unnecessarily obscuring the described ideas. Although some ideas will be described with specific examples, it will be understood that these examples are not intended to be limiting.

[0022] Figure 1AAn example of a device for enhancing the noise immunity of a capacitive sensor, configured according to some embodiments, is shown. As will be discussed in more detail below, a capacitive sensor may include various components configured to identify the presence of an object using capacitance measurements. As disclosed herein, presence can refer to contact, hovering, or other sensed events. For example, a capacitive sensor may utilize various electrodes to sense proximity or contact with a user's finger based on capacitance-based measurements. More specifically, a capacitive sensor may include a sensing channel with an input attenuator configured to receive sensed input from a sensing device (e.g., a touch panel that may include a capacitive touchscreen). As will be discussed in more detail below, a device (e.g., device 100) may be configured to modulate the input signal received by the input attenuator to reduce noise and increase the sensitivity of downstream components used for measurement when sensing is performed by the capacitive sensor.

[0023] Therefore, device 100 includes input 102, which can be an input to one or more components coupled to the sensing device. As discussed similarly above, capacitive sensors can include sensing devices comprising electrodes for performing various measurements that can be used to infer the presence of adjacent or contacting objects (e.g., fingers, styluses, or other conductive objects). It will be understood that any suitable conductive object can be used. Furthermore, such an object can be made of any suitable material from which altering the physical environment of the sensing electrodes causes a change in capacitance. More specifically, the sensing device can be a touch panel including an array of transmitting electrodes and an array of receiving electrodes. A scanning sequence can be implemented in which signals are transmitted through one or more of the transmitting electrodes, and measurements are taken at one or more of the receiving electrodes. The measurements can be capacitance measurements and can be affected by adjacent or contacting objects. For example, a user's finger touching or hovering near the touch panel at a particular location may affect the capacitance measurement of the electrodes at that location. The sensed signals from the receiving electrodes can be received at input 102.

[0024] Device 100 further includes an attenuator 104 configured to set the input impedance as seen by a sensing device (e.g., a touch panel) and also configured to set the output impedance as seen by other components of the sensing channel, as will be referred to below at least Figure 3 and Figure 4 This will be discussed in more detail. Therefore, the sensed signal received at input 102 can be coupled to the input of attenuator 104. Thus, according to various embodiments, attenuator 104 is configured to provide several characteristics. More specifically, it attenuates the input signal, it provides impedance transformation characteristics, it provides low input impedance and high output impedance, and it acts as a current source, wherein the output current is determined based on the input current.

[0025] Device 100 further includes a signal generator 106 configured to generate a signal that reduces specific characteristics of the input signal sensed at input 102. As will be discussed in more detail below, the sensed signal may be susceptible to external noise that may be caused by various sources. For example, noise may be generated by other components (e.g., a liquid crystal display (LCD) panel) and may be capacitively coupled between components or even the user's finger (such as charger noise). In various sensing channel embodiments, noise may manifest as increased sensitivity at odd harmonics of frequencies that can be used during sensing operation. For example, a scan sequence of electrodes included in a touch panel may involve scan bursts implemented at a specific scan frequency. The aforementioned noise sources and associated parasitic capacitances can cause increased sensitivity to noise at odd harmonics of the scan frequency. For example, a measured increase in signal may occur at the third, fifth, seventh, and ninth harmonics of the scan frequency. Such measured harmonics are undesirable because they are primarily products of the noise characteristics of the sensing channel, rather than the potential touch / hover being measured. Therefore, some capacitive sensing channels may be sensitive to odd harmonics of the operating frequency.

[0026] The embodiments disclosed herein eliminate sensing channel sensitivity to odd harmonics without requiring significant or costly modifications to the channel itself. This can be accomplished by adding a mixer as part of an existing sensing channel, as will be discussed in more detail below. The mixer provides input current multiplication on non-negative (including zero, meaning zero gain) harmonics. In various embodiments, the mixer input waveform is a rectified sine wave with the same frequency as the transmitted signal. It will be understood that the mixer implementation can differ across embodiments. For example, the mixer can be implemented as a variable gain amplifier with discrete gain levels, or driven by the output of a sigma modulator. In one embodiment, the mixer is an on / off switch that operates at relatively high oversampling frequencies (e.g., 48 MHz for a 100 kHz transmitted signal). As will be discussed in more detail below, various features of the mixer can be implemented within the sensing channel, for example, by changing the attenuator gain at the attenuator front end, as can be achieved using the previously described switch.

[0027] In various embodiments, the signal generated by signal generator 106 is configured to reduce or attenuate the effect of these noise sources on the sensed signal. Signal generator 106 provides a rectified sine wave with a frequency determined by the operating frequency of the transmitted signal. The waveform amplitude is configured to provide mixer operation in the linear range and prevent analog saturation. In this way, adding an analog mixer driven by a rectified sine signal at the front end of the sensing channel eliminates sensitivity to odd harmonics. In various embodiments, the operating frequency is configured to provide the lowest noise level for the output reading in the presence of external noise (e.g., LCD noise). Therefore, the operating frequency is configured such that the overlap with the frequency response of the sensing channel in the frequency domain of the noise spectrum is reduced. Eliminating sensitivity to odd transmitted frequency harmonics provides a reduction in noise spectrum overlap and additionally provides attenuation of external noise. The result of noise attenuation is an increase in the signal-to-noise ratio of the capacitive sensing system. As discussed above, the output of signal generator 106 is coupled to a mixer (e.g., mixer 108). Therefore, as discussed above, mixer 108 is configured to multiply the output of signal generator 106 with the sensed signal received at input 102, and provide the result as input to attenuator 104.

[0028] Figure 1B Another example of an apparatus for enhancing the external noise immunity of a capacitive sensor, configured according to some embodiments, is shown. As discussed similarly above, the apparatus (e.g., apparatus 110) can be configured to modulate the input signal received by the input attenuator to reduce out-of-band noise (noise outside the transmission frequency) and increase the sensitivity of downstream components used for measurement when sensing operations are performed by the capacitive sensor.

[0029] As discussed above, device 110 may also include input 102 and attenuator 104. In various embodiments, the device further includes modulator 112, which may be included in a signal generator and may be coupled to variable gain amplifier 114. Thus, as Figure 1B As shown, modulator 112 is configured to generate a signal that is configured to reduce the noise characteristics of the input signal sensed at input 102. Furthermore, variable gain amplifier 114 is configured as a mixer and is configured to combine the signal generated by modulator 112 with the sensed signal received at input 102. In this way, variable gain amplifier 114 is configured to operate as an analog mixer and attenuate the out-of-band noise components of the sensing channel (those noise components outside the passband of the sensing channel), as discussed above. (Refer to below...) Figures 3A-3C Additional details regarding the configuration of the variable gain amplifier will be discussed in more detail.

[0030] Figure 2Examples of systems configured according to some embodiments for enhancing the noise immunity of capacitive sensors are shown. As discussed similarly above, capacitive sensors can include various components configured to detect the presence of an object using capacitance measurements. For example, a capacitive sensor can utilize various electrodes to sense the presence or contact of a user's finger based on capacitance-based measurements. In various embodiments, the system (e.g., system 200) can be configured to initialize and utilize a signal generator to reduce noise, and thus improve the signal-to-noise ratio.

[0031] Therefore, system 200 includes attenuator 202, which is configured to set the input impedance as seen by the sensing device (e.g., a touch panel) and is also configured to set the output impedance as seen by other components of system 200, discussed in more detail below. Thus, attenuator 202 can be configured to reduce input current and provide low input impedance for touchscreen input current. Furthermore, attenuator 202 can be further configured to provide high output impedance for various components (e.g., capacitors, discussed in more detail below). In various embodiments, attenuator 202 and components of system 200 are implemented as a sensing channel of a capacitive sensor. In various embodiments, the sensing channel operates as a charge-balanced charge-to-time converter circuit.

[0032] System 200 also includes a signal generator 204 configured to generate a gain control signal provided to attenuator 202, and configured to reduce specific characteristics of an input signal sensed at an input that can be received from one or more electrodes in a touch panel. As will be discussed in more detail below, in some embodiments, signal generator 204 is configured to include a demodulator configured to generate a rectified sine wave that can be provided to attenuator 202. Therefore, the output signal generated by signal generator 204 can be used to change the gain of attenuator 202 based on the output signal. When configured in this way, attenuator 202 operates as an analog mixer that multiplies the input signal received from the sensing electrodes with the rectified sine wave. Therefore, the gain of attenuator 202 is in, for example, the range 0…K. MAX (where K) MAXThe gain level is varied within the maximum gain level. In various embodiments, the attenuator input signal is bipolar, but the gain variation factor is unipolar. In some embodiments, the signal generator 204 is configured to implement a lookup table (LUT) for determining the gain value of the signal generator 204 using a pre-programmed set of gain levels. Therefore, a pre-programmed LUT can be used instead of a demodulator. Furthermore, as will be discussed in more detail below, the signal generator 204 can be further configured to implement windowing via a window function to further narrow the frequency response peak and further increase the noise attenuation and signal-to-noise ratio of the system 200. In various embodiments, the signal generator 204 is implemented using a single-bit (dual-level) or multi-bit (multi-level) sigma-delta modulator.

[0033] System 200 further includes a first integrated capacitor 206 and a second integrated capacitor 208, configured to perform various operations, such as balancing the output of integrated charge from attenuator 202, which can be generated based on received or sensed input. Thus, the first integrated capacitor 206 can be an even-phase integrated capacitor, and the second integrated capacitor can be an odd-phase integrated capacitor, and they can together achieve time-separated (interleaved) phases for charge accumulation and balancing. In various embodiments, the output of system 200 is generated using a balancing time interval, represented as a value determined proportional to the total charge integrated by one or more of the integrated capacitors during half of a transmission cycle or other suitable time intervals. The integration of multiple balancing intervals (e.g., 10 transmission cycles, and a total of 20 intervals) produces a baseline value.

[0034] System 200 further includes a current source 210 (which may be a balancing current source) configured to generate a current associated with the first integrated capacitor 206 and the second integrated capacitor 208 discussed above. In various embodiments, the current is used to charge the first integrated capacitor 206 and the second integrated capacitor 208. For example, a digitizer can use the current to charge and discharge the integrated capacitors. Therefore, depending on the specific characteristics of the sensing channel including current source 210, current source 210 can have several different uses. In one example, it can be used for both digitization and calibration associated with balancing operations. Thus, current source 210 may include source current sources and sink current sources configured to generate the appropriate current used during balancing operations. Figure 2As shown, current source 210, first integrated capacitor 206, and second integrated capacitor 208 can be coupled to comparator 212, which can be configured to detect changes in the voltage of the first integrated capacitor 206 and the second integrated capacitor 208 relative to a reference voltage.

[0035] System 200 further includes a controller 214 configured to measure the output of comparator 212 and generate various control signals for use by other components of system 200. For example, controller 214 may be configured to generate control signals for balancing operations, controlling the coupling of the first integrated capacitor 206 and the second integrated capacitor 208, reset operations, and initializing attenuator 202 at the start of capacitance switching. In this way, controller 214 can obtain measurements from the sensing channels implemented by system 200 and can control various components within system 200.

[0036] Figure 3A Examples of attenuators configured according to some embodiments are shown. As discussed above, an attenuator (e.g., attenuator 302) can be implemented in the environment of a sensing channel and its gain can be modulated to reduce or attenuate undesirable noise characteristics of the sensed signal, such as at odd harmonics of the scan frequency. Thus, attenuator 302 can be specifically configured to achieve variable gain in this manner.

[0037] More specifically, attenuator 302 may include an input stage 304 that may have a fixed gain and an output stage 306 that may have a variable gain. Figure 3A As shown, input stage 304 includes operational amplifier 308, and output stage 306 includes multiple current mirrors (e.g., current mirror 310). Furthermore, output stage 306 includes multiple switches (e.g., a set of switches 312) such that each current mirror has an individual switch, and each current mirror can be selectively coupled or decoupled to the output of attenuator 302. In various embodiments, the switches are controlled via control signals to dynamically couple and decouple the various current mirrors during sensing operation. In this way, the operation of the switches can be controlled to achieve current summation of the current mirrors in a dynamically configurable manner, wherein the magnitude of the output current of attenuator 302 is directly proportional to the number of coupled current mirrors. As discussed above, such control signals can be generated by components (e.g., controllers).

[0038] As discussed above, the output of attenuator 302 can be coupled to one or more capacitors (e.g., integrated capacitors (Cint)). Therefore, the configuration of the gain of attenuator 302 can affect the output current, and thus the attenuator gain modulation affects the total charge in the integrated capacitor and the corresponding voltage across the integrated capacitor. Due to the configuration of the implementation of multiplication of the input signal on the rectified sine signal, out-of-band noise is attenuated, thus reducing sensitivity to odd harmonics of the transmission frequency.

[0039] Figure 3B Another example of an attenuator configured according to some embodiments is shown. As discussed above, an attenuator (e.g., attenuator 320) can be implemented in the environment of a sensing channel and its gain can be modulated to reduce or attenuate undesirable noise characteristics of the sensed signal, such as at odd harmonics of the scan frequency. As discussed above, attenuator 320 may include an input stage 322 and an output stage 324, which may include various current mirrors and switches.

[0040] As referenced above Figure 3A The switch discussed can be used to control the output of a current mirror for current summation. For example... Figure 3B As shown, a switch (e.g., switch 326) can be used to control the gate circuit of the current mirror. Therefore, as... Figure 3B As shown, the current mirror and switch can be configured such that the gate switch is used to control the operation of the current mirror. Therefore, control signals can be generated to dynamically control the operation of the gate switch and the activation of the transistors included in the current mirror. Thus, in various embodiments, the gate switch can be used to modify the output current of the attenuator 320 and the voltage applied to the downstream integrated capacitor.

[0041] Figure 3C Another example of a variable gain attenuator configured according to some embodiments is shown. As discussed above, the attenuator (e.g., attenuator 330) can be implemented in the environment of a sensing channel and its gain can be modulated to reduce or attenuate undesirable noise characteristics of the sensed signal, such as at odd harmonics of the scan frequency. In various embodiments, attenuator 330 is configured to use low-voltage, low-injection differential stages to achieve current switching between the integrated capacitor and the analog buffer. In various embodiments, a differential current switch redistributes the current mirror output current between the integrated capacitor and the buffer output. Distributing the current in this way ensures that the voltage across the integrated capacitor remains constant and provides ultra-low injection gain adjustment.

[0042] Therefore, attenuator 330 may include stages 332 and 334, which may be coupled to integrated capacitor 336 and buffer 338. Figure 3C As shown, stage 332 can be a differential stage operating at a relatively low switching voltage (e.g., 100mV). Therefore, the configuration of stage 332 results in lower parasitic injection in the integrated capacitor 336. Furthermore, stage 334 can include components similar to those shown for stage 332. In various embodiments, attenuator 330 can include one or more differential current switching stages, such as stage 332. In various embodiments, the output current to integrated capacitor 340 is determined by the number of stages simultaneously activated or “on”, and this number varies based on half a cycle of the rectified sine wave, as discussed similarly above.

[0043] Furthermore, despite Figure 3C The attenuator 330 is shown to have two identical differential current switches, but it will be understood that the attenuator 330 can have any number of differential current switches. For example, as discussed above, the number of current switches can be determined based on one or more characteristics of the modulator's output. More specifically, the modulator can be a multi-level delta-sigma modulator, and the number of levels can be determined based on the number of levels used by the delta-sigma modulator.

[0044] Figure 4 Another example of a system for enhancing the noise immunity of a capacitive sensor, configured according to some embodiments, is shown. As discussed similarly above, the system (e.g., system 400) can be configured to initialize a signal generator during measurement and utilize the signal generator to reduce noise and increase the signal-to-noise ratio. As discussed above, system 400 may include an attenuator 402, a first integrated capacitor 406, a second integrated capacitor 408, a current source 410, a comparator 412, and a controller 414.

[0045] like Figure 4As shown, system 400 further includes a switch 416 included in the attenuator feedback path 418. When turned on, switch 416 couples the current output of attenuator 402 back to its sensed input, and attenuator 402 is set to a reset or initialized state. More specifically, when the integrated capacitor is turned off, switch 416 can be turned on to keep attenuator 402 in a reset state, thus preventing parasitic charge accumulation at the attenuator output stage. In various embodiments, control signals can be specifically configured to control the operation of switch 416 and other components to reduce parasitic charge accumulation and thus reduce noise present in the obtained measurements. More specifically, control signals can be configured to control the operation of switch 416, and additional control signals can be configured to control the operation of switch 420 coupled to the first integrated capacitor 406 and switch 422 coupled to the second integrated capacitor 408. Control signals can be generated based on values ​​stored in a timer table, and therefore can be generated based on a data value table operating as a LUT. Such a timer table can be stored in a set of registers and can include data values ​​that define the sequence of coupling and decoupling of switches in a manner that can be implemented periodically.

[0046] As will be discussed in more detail below, a timer table can be generated by first performing a frequency scan to identify the frequencies that need to be attenuated, and then generating a timer table based on the identified frequencies. In this way, a LUT can be used during the scan operation to implement the values ​​of control signals and the operation of switching. Therefore, the switching control signal can be a single-bit representation of a rectified sine wave signal and can be generated in any suitable manner (e.g., via a single-bit sigma-delta modulator, LUT, timer table, etc.).

[0047] Figure 5A An implementation of an attenuator configured according to some embodiments is shown. Also, as discussed above, the attenuator (e.g., attenuator 502) can be configured such that the input to the attenuator is modulated to reduce the sensitivity to out-of-band transmission frequency components. Figure 5AAs shown, attenuator 502 can be coupled to input controller 504, which includes switch 506. In various embodiments, switch 506 is configured to switch coupling between a sensed input and different inputs of attenuator 502. For example, in a first position, switch 506 can couple an input to a first input of attenuator 502, which is also coupled to a feedback path. In a second position, switch 506 couples an input to a second input of attenuator 502, which is also coupled to a reference voltage. In various embodiments, switch 506 can be a single-pole double-throw (SPDT) switch. Furthermore, as discussed above, the operation of switch 506 can be controlled via a timer table configured as a LUT. Therefore, switch 506 is configured to provide a single-bit (dual-level: gain factor of zero or one) discrete-time mixer that reduces external, out-of-transmit band noise components, similar to the reference above. Figures 3A-3C Other discrete-time mixer / variable gain attenuator implementations are discussed.

[0048] Figure 5B An implementation of an attenuator configured according to some embodiments is shown. As discussed similarly above, the attenuator (e.g., attenuator 510) can be configured to modulate the input of the attenuator. Also as discussed above, attenuator 510 can be coupled to an input controller 512 including a first switch 514 and a second switch 516. In various embodiments, the first switch 514 is configured to selectively couple and decouple the sensed input from a global bus of a sensing channel associated with attenuator 510. Furthermore, the second switch 516 is configured to selectively couple and decouple the sensed input from the input of attenuator 510. Additionally, a third switch 518 can be implemented to couple and decouple the global bus from a reference voltage. As discussed similarly above, the operation of the first switch 514 and the second switch 516 is controlled via a timer table configured as a LUT. In various embodiments, switches 514, 516, and 518 can be part of a programmable touch panel multiplexer architecture.

[0049] Figure 6 An example of a system for enhancing the noise immunity of a capacitive sensor, configured according to some embodiments, is shown. As discussed similarly above, a system (e.g., system 600) can be configured and utilize a signal generator to reduce noise and increase the sensitivity of components used to perform such measurements. Therefore, system 600 may include an attenuator 602, a capacitor 604, a resistor 606, and a signal generator 608. In some embodiments, resistor 606 and capacitor 604 may represent the equivalent resistance and capacitance provided by the touch panel in self-capacitance sensing mode.

[0050] like Figure 6 As shown, system 600 further includes a programmable attenuator 610, which may be a multi-gain-level attenuator and may be programmable to select the gain applied to the input of attenuator 602. For example, programmable attenuator 610 may include a multiplexer (e.g., multiplexer 612) that can be configured to select a specific input coupling path provided between the inputs of multiplexer 612 and attenuator 602. Each different path may have a different gain, and the selection of the path may be controlled by a signal provided by signal generator 608. Thus, the selection of the path provided by multiplexer 612 can be used to modify the input gain provided to attenuator 602 because each different path has a different gain determined by a unique configuration of resistors. Although the operation of multiplexer 612 is shown as being controlled by signal generator 608, in some embodiments, the operation of multiplexer 612 is controlled via a timer table configured as a LUT. According to various embodiments, any suitable number of gain levels can be used. For example, in one embodiment, eight gain levels may be supported.

[0051] Figure 7 An example of a system for enhancing noise immunity to a capacitive sensor, configured according to some embodiments, is shown. As discussed above, the systems disclosed herein are configured to obtain impedance and capacitance measurements and to identify hover and touch events, such as those that may occur when a user hovers over or touches the sensing device, based on such measurements. Therefore, a system (e.g., system 700) may include such a sensing device that can be implemented in the context of a capacitive sensor.

[0052] Therefore, system 700 includes a sensing device 702, which may include components such as electrodes configured to sense measured changes in electrical performance within a specified distance of the sensing device. As discussed above, the sensing device may be a touchscreen, touch panel, or button that includes one or more electrodes. In one example, the electrodes may be arranged in an array of transmitting and receiving electrodes, wherein the transmitting electrodes are configured to transmit signals according to a scanning protocol or sequence, and the receiving electrodes are configured to receive signals, thereby obtaining a sensed impedance measurement between the two electrodes.

[0053] System 700 further includes one or more sensing channels 704 configured to receive signals sensed by sensing device 702, such as those generated by receiving electrodes included in the sensing device. As discussed above, sensing channel 704 includes various components, such as attenuators and integrated capacitors. Additional details regarding the operation of the sensing channels have been discussed above. Figure 7As shown, the sensing channel 704 can also be coupled to components such as the first signal generator 706 and the processing unit 708. As discussed above, the first signal generator 706 can generate a signal configured to reduce noise that may be present in the measurements obtained through the sensing channel 704 and can be caused by various sources (e.g., parasitic capacitance). Furthermore, the processing unit 708 can be configured to include a controller as discussed above, and one or more processors configured to perform other sensing operations. For example, the processing unit 708 can be configured to identify measurement data and store the measurement data in a memory device, and to perform one of several calculations to identify specific events, such as hover events and touch events. Although the first signal generator 706 and the processing unit 708 have been shown as being coupled to the sensing channel 704, it will be understood that the first signal generator 706 and the processing unit 708 can be included within the sensing channel 704.

[0054] System 700 further includes a transmit channel 710 configured to generate a signal provided to sensing device 702, which provides the signal for use during a scan sequence and forms the basis for subsequent measurements. Therefore, transmit channel 710 may include various components, such as amplifiers and / or buffers, and current and / or voltage sources. Figure 7 As shown, the transmit channel 710 can be coupled to a second signal generator 712 and a charge pump 714. Therefore, the second signal generator 712 can be configured to generate a signal for driving the transmit electrode during the scan sequence, and thus the parameters of this drive signal can be configured. The charge pump 714 can be configured to voltage-regulate the transmit channel 710. Furthermore, the multiplexer 720 can be configured to selectively couple the sensing channel 704 and the transmit channel 710 to specific electrodes of the sensing device 702 according to the scan sequence. Therefore, the multiplexer 720 can include a transmit multiplexer for the transmit electrode and a sensing multiplexer for the sensing (also referred to herein as a receive) electrode.

[0055] Figure 8A flowchart illustrating an example of a sensitivity enhancement method for a capacitive sensor implemented according to some embodiments is shown. As discussed above, a capacitive sensor may include various components configured to utilize capacitance to identify the presence of an object. For example, a capacitive sensor may utilize various electrodes to sense the presence of a user's finger or contact with it based on capacitance-based measurements. As discussed above, when a sensing operation is performed by a capacitive sensor, the operation of the attenuator gain may be modulated to reduce noise and increase the signal-to-noise ratio for the measurement. Therefore, according to various embodiments, a method (e.g., method 800) may be implemented during runtime to reduce noise that may occur at odd harmonics.

[0056] Therefore, method 800 can begin with operation 802, during which the transmit signal generator and the sense signal generator can be initialized at least in part based on a plurality of demodulation parameters. As discussed above, the transmit signal generator can be included in the transmit channel and used to drive the transmit electrodes during the scan sequence. Therefore, during operation 802, the transmit signal generator can be initialized based on a specified scan sequence or protocol. Furthermore, as discussed above, the sense signal generator can be a signal generator implemented in the sense channel and used to modulate the operation of one or more components in the sense channel. For example, the signal generator can modulate the gain of an attenuator included in the sense channel. Therefore, during operation 802, the sense signal generator can be initialized.

[0057] Method 800 can proceed to operation 804, during which scanning of multiple electrodes of the capacitive sensing device can be performed. Therefore, a scanning sequence can be realized. As will be discussed in more detail below, the scanning sequence can be implemented according to specified scanning parameters and can be based on sensed input received from the sensing device and measured according to the operation of the sensing signal generator, as discussed similarly above.

[0058] Method 800 can proceed to operation 806, during which scan data can be collected, at least in part, based on scanning of multiple electrodes. Therefore, the measured data can be stored in a memory device. Furthermore, one or more calculations can be performed. For example, the measurements can be used to identify one or more events, such as touch events and / or hover events. Such calculations can be based on comparisons of the measurements with one or more threshold values ​​or any suitable event detection technique.

[0059] Figure 9A flowchart illustrating another example of a method for enhancing the sensitivity of a capacitive sensor, implemented according to some embodiments, is shown. As discussed above, a unique configuration of the signal generator in the capacitive sensor can be implemented during runtime to reduce noise that may occur in the measurement, for example, at odd harmonics. Therefore, a method (e.g., method 900) can be implemented to control the operation of such a signal generator and enhance the sensitivity of the capacitive sensor, as discussed above.

[0060] Method 900 may begin with operation 902, during which one or more capacitive sensor electrodes may be initialized. In various embodiments, components such as signal generators and current sources may be initialized and configured based on one or more configuration parameters. In some embodiments of capacitive sensing configurations, the number of touch panel receiving electrodes is much greater than the number of sensing channels. Therefore, it is necessary to scan the entire panel in several scanning slots, where, in a particular scanning slot, a particular sensing channel is serially connected to a selected set of electrodes during a particular scanning slot. Thus, as used herein, a scanning slot may be a specific configuration or set of sensing channels and sensing electrodes that may be selected during several scanning iterations for scanning the entire capacitive sensor, which may include the touch panel.

[0061] Method 900 can proceed to operation 904, during which one or more multiplexers can be configured based on specified scan positions. As discussed above, the sensing device may include a plurality of transmitting and sensing electrodes, which may be arranged in an array with intersections. In various embodiments, the electrodes may be scanned sequentially. Therefore, during operation 904, the transmitting and sensing multiplexers can be configured to select specific electrodes from the transmitting and sensing electrodes. In various embodiments, such electrodes may be indexed by identifiers stored and maintained by a controller, and the multiplexers may be configured based on received selection signals.

[0062] Method 900 can proceed to operation 906, during which the transmit signal generator and the sense signal generator can be initialized synchronously. Therefore, the transmit signal generator can be initialized and started, and the sense signal generator can be initialized and started simultaneously. As discussed above, the sequence and output of the signal generators are configured such that the transmit signal generator generates a drive signal for driving the transmit electrodes in the sensing device, and the sense signal generator generates a signal that modulates one or more components in the sensing channel to reduce and mitigate noise components in the sensed signal received in response to the drive signal. For example, the sense signal generator can periodically modulate the gain of the attenuator of the sensing channel to effectively eliminate noise components in the sensed signal.

[0063] Method 900 can proceed to operation 908, during which a scan sequence can be implemented. Therefore, as discussed above, once the signal generator has been initialized, a scan sequence can be implemented for the selected electrode pair. The scan sequence can be implemented at a specific scan frequency and amplitude. Thus, during operation 908, the transmit signal generator can drive the transmit electrode at the scan frequency according to the scan parameters, and the sense signal generator generates a signal used to reduce the noise component of the signal sensed in response to the drive signal. As previously discussed, this may include modulating the gain of the attenuator, and / or operating one or more switches implemented in combination with the attenuator.

[0064] Method 900 can proceed to operation 910, during which scan data can be collected at least in part based on the scan sequence. As discussed above, measurements can be performed at a specified sampling rate, and the measured data can be stored in a memory device. As discussed above, one or more calculations can be performed. For example, the measurements can be used to identify one or more events, such as touch events and / or hover events. Such calculations can be performed based on comparisons of the measurements with one or more threshold values ​​or any suitable event detection technique. In some embodiments, such calculations can be performed after all measurement data has been acquired from all electrodes.

[0065] Method 900 can proceed to operation 912, during which it can be determined whether an additional scan should be performed. In various embodiments, this determination can be based on one or more aspects of the sensing device. As discussed above, the sensing device may include multiple electrodes, which can be identified based on indices or identifiers. During the scan sequence, the electrodes can be scanned sequentially. Therefore, the controller can cycle through the electrodes until the last electrode is scanned, as can be determined based on an identifier. In one example, the controller may use a state machine configured to cycle through the electrodes in this manner. Therefore, if it is determined that an additional scan should be performed, method 900 can return to operation 904, and a different set of electrodes can be selected and scanned. If it is determined that no additional scan should be performed, method 900 can terminate.

[0066] Figure 10 A flowchart illustrating an additional example of a sensitivity enhancement method for a capacitive sensor based on transmit signal phase adjustment, implemented according to some embodiments, is shown. As discussed above, during runtime, a unique configuration of the signal generator in the capacitive sensor can be implemented to reduce noise in measurements that may occur, for example, at odd harmonics. Furthermore, methods (e.g., method 1000) can be implemented to calibrate the transmit signal generator to compensate for phase shifts introduced by the components of the capacitive sensor, and thus increase the effectiveness of the combination of signal generators discussed above. In various embodiments, to further increase the sensitivity of the capacitive sensor, the input sine wave is phase-aligned with the attenuator gain control signal. This alignment is performed based on a phase calibration procedure, which will be discussed in more detail below.

[0067] Method 1000 may begin with operation 1002, during which one or more multiplexers may be configured based on specified scan positions. As discussed above, the sensing device may include a plurality of transmit electrodes and sense electrodes that can be scanned sequentially. Therefore, during operation 1002, the transmit multiplexer and sense multiplexer may be configured to select specific electrodes from the transmit electrodes and sense electrodes. In various embodiments, such electrodes may be indexed by identifiers stored and maintained by a controller, and the multiplexer may be set based on a received selection signal.

[0068] Method 1000 can proceed to operation 1004, during which a sensing signal generator and a transmitting signal generator can be initialized. As discussed above, components such as the signal generator and current source can be initialized and configured based on one or more configuration parameters. Therefore, during operation 1004, the sensing signal generator can be phase-aligned with the current source used for that channel. Similarly, phase alignment can be implemented for the components of the transmitting channel.

[0069] Method 1000 can proceed to operation 1006, during which an initial phase offset value can be identified and retrieved. In various embodiments, the phase offset value can be identified for the transmit signal generator. This phase offset value may have been stored as a specified default phase value to be used at the start of the calibration procedure. This value may have been determined by the manufacturer or user during the initial configuration of the capacitive sensor. In one example, the initial phase offset value may be a value of 0, and the phase offset value may be increased in specified increments, as will be discussed in more detail below.

[0070] Method 1000 can proceed to operation 1008, during which the transmit signal generator can be initialized based on the phase shift value. Therefore, the transmit signal generator can be configured to achieve phase shifting when generating the output signal. In this way, phase shifting can be achieved using the transmit electrodes of a driving capacitive sensing device.

[0071] Method 1000 can proceed to operation 1010, during which a scan sequence can be implemented. Therefore, as discussed above, once the signal generator has been initialized and the phase offset value has been loaded, a scan sequence can be implemented. The scan sequence can be implemented with a specific scan frequency and amplitude. Thus, during operation 1010, the transmit signal generator can drive the transmit electrode at the scan frequency according to the scan parameters, and the sense signal generator generates a signal used to reduce the noise component of the signal sensed in response to the drive signal.

[0072] Method 1000 can proceed to operation 1012, during which a baseline value can be calculated and stored for the phase offset value. Therefore, measurement data can be stored, and a baseline value representing the baseline amplitude or magnitude of the received signal can be calculated. Thus, one or more averaging techniques or other computational techniques can be implemented to calculate the baseline value, which represents the sensitivity of the sensing channel at a selected phase offset value. In various embodiments, as referenced above... Figure 2 and Figure 4 The baseline value discussed can be proportional to the total output of the charge-time converter. For example, the baseline value can be calculated by summing over the balancing time intervals for the scan burst (e.g., over 10 emission cycles).

[0073] Method 1000 may proceed to operation 1014, during which it may be determined whether the maximum phase offset has been reached. In various embodiments, this determination may be made by the controller based at least in part on the phase offset value itself. As previously discussed, the phase offset value may be set to an initial value and may be incremented within a specified range. Thus, the controller may include a state machine configured to incrementally increment the offset value until a maximum value is reached. In some embodiments, the maximum value may be a specified value set by the user or manufacturer. For example, the maximum value may correspond to a phase offset of a full cycle or half cycle of the transmit frequency used by the transmit signal generator. If it has been determined that the maximum phase offset value has not yet been reached, method 1000 may proceed to operation 1016.

[0074] Method 1000 can proceed to operation 1016, during which the phase offset value can be incremented. As discussed above, the phase offset value can be incremented according to a specified increment scheme. More specifically, the controller can be configured to increment the phase offset value by a specified amount (e.g., a specified number of degrees), and the incremented value can be stored as a new phase offset value to be used. Method 1000 can then return to operation 1008, where additional measurements can be performed and additional baseline values ​​can be calculated until the maximum phase offset value has been reached.

[0075] Returning to operation 1014, if it has been determined that the maximum phase offset value has been reached, method 1000 can proceed to operation 1018, during which the peak baseline value can be identified. Therefore, the calculated baseline values ​​can be compared, and the maximum baseline value with the highest baseline value can be identified. The phase offset value associated with the maximum baseline value can also be identified.

[0076] Method 1000 can proceed to operation 1020, during which a phase offset value associated with the peak baseline value can be selected and stored as a phase offset value for the transmit signal generator. Therefore, the phase offset value identified during operation 1018 can be stored in a memory device and can be used to initialize and configure the transmit signal generator during subsequent scan operations. In this way, the transmit signal generator can be configured to compensate for various phase offsets introduced by components included in the capacitive sensor.

[0077] Figure 11A and Figure 11B Illustrations show examples of attenuator inputs and outputs with different numbers of gain steps, implemented according to some embodiments. More specifically, Figure 11A The attenuator input current 1102 and attenuator output current 1104 are shown, and the attenuator has seven gain levels implemented using a 3-bit quantizer. Furthermore, Figure 11BThe attenuator input current 1106 and attenuator output current 1108 are shown, and the attenuator has two gain levels implemented using a 1-bit quantizer. In various embodiments, the output current approximates a sin(π / 2) similar to that of a conventional analog multiplier. 2 (t) function. For example... Figure 11A and Figure 11B As shown, increasing the number of gain levels can provide a better approximation of a sinusoidal signal.

[0078] Figure 12A and Figure 12B An illustration shows an example of a signal sensed by one or more sensing channels, implemented according to some embodiments. More specifically, Figure 12A The signal sensed at a specific transmission frequency is shown, wherein the sensed signal is sensed by a sensing channel not configured to provide noise immunity, as disclosed herein. In various embodiments, the sensed transmission signal at the transmission frequency (also referred to herein as the operating frequency) is represented by peak value 1202. Figure 12A Additional peaks at odd harmonics of the operating frequency are further shown, such as peaks 1204, 1206, 1208, and 1210. As discussed above, such peaks represent measurement noise, which reduces the overall signal-to-noise ratio of the capacitive sensor.

[0079] In various embodiments, Figure 12B The signal sensed at a specific transmission frequency is shown, wherein the sensed signal is sensed by a sensing channel configured to provide noise immunity, as disclosed herein. Therefore, the sensing of the transmitted signal at this transmission frequency is represented by a peak value 1212. Figure 12B As shown, there are no other peaks associated with odd harmonics. Therefore, the peaks in the measured signal caused by odd harmonics have been eliminated, and the overall signal-to-noise ratio of the capacitive sensor has been improved.

[0080] Although the foregoing concept has been described in detail for clarity of understanding, it will be apparent that certain changes and modifications can be practiced within the scope of the appended claims. It should be noted that many alternative implementations, systems, and apparatus exist. Therefore, this example should be considered illustrative rather than restrictive.

Claims

1. An apparatus comprising: An attenuator configured to receive input from at least one sensing electrode of a capacitive sensing device, the attenuator being included in the sensing channel of the capacitive sensor; as well as A signal generator coupled to the input of the attenuator, the signal generator including one or more processors configured to: A sinusoidal signal is generated based at least in part on one or more noise characteristics of a scan sequence associated with one or more emitter electrodes of the capacitive sensing device; as well as The sinusoidal signal is provided to the input of the attenuator. The device further includes a mixer configured to combine the sinusoidal signal received from the signal generator with the input received from the at least one sensing electrode, and further configured to generate an output based on the combination.

2. The device according to claim 1, wherein, The signal generator includes a sine modulator.

3. The device according to claim 1, wherein, The mixer is a variable gain amplifier configured to change the gain based on a gain control signal.

4. The device according to claim 1, wherein, The signal generator is configured to use the sinusoidal signal to modulate the gain of the attenuator, wherein the sinusoidal signal is a rectified sinusoidal signal.

5. The device according to claim 1, wherein, The signal generator is configured to provide the sinusoidal signal to the attenuator during the scan sequence.

6. The device according to claim 1, wherein, The signal generator is further configured to implement window functionality.

7. The device according to claim 1, wherein, The at least one sensing electrode and the one or more transmitting electrodes are included in the electrode array of the capacitive touchscreen.

8. The device according to claim 1, wherein, The signal generator is configured to synchronize with the transmitting signal generator, and the transmitting signal generator is configured to implement a phase offset value.

9. The device according to claim 8, wherein, The phase shift is determined based on the peak response of the capacitive sensor.

10. A method comprising: The emission drive signal is generated at least in part based on one or more scanning parameters and is provided to one or more emission electrodes of the capacitive sensing device. A signal generator is used to generate a sinusoidal signal, based at least in part on the transmit drive signal and one or more noise characteristics of the capacitive sensing device; Receive the sensed signal from at least one sensing electrode of the capacitive sensing device; as well as The reduction of one or more noise characteristics in the sensed signal is based at least in part on the sinusoidal signal, wherein the reduction includes: using a mixer at the input of the attenuator to combine the sensed signal with the sinusoidal signal.

11. The method according to claim 10, wherein, The signal generator includes a sine modulator.

12. The method according to claim 10, wherein, The mixer is a variable gain amplifier configured to change the gain based on a gain control signal.

13. The method according to claim 10, wherein, The reduction includes: The gain of the attenuator is modulated at least in part based on the sinusoidal signal.

14. A system comprising: Multiple sensing electrodes implemented in a capacitive sensing device; Multiple emitting electrodes are implemented in the capacitive sensing device; An attenuator configured to receive input from at least one of the plurality of sensing electrodes, the attenuator being included in the sensing channel of the capacitive sensor; A signal generator coupled to the input of the attenuator, the signal generator including one or more processors configured to: A sinusoidal signal is generated based at least in part on one or more noise characteristics of a scan sequence associated with one or more emitter electrodes of the capacitive sensing device; and The sinusoidal signal is provided to the input of the attenuator; as well as A controller configured to implement the scan sequence and obtain multiple measurements based on the scan sequence. The system further includes a mixer configured to combine the sinusoidal signal received from the signal generator with the input received from at least one of the plurality of sensing electrodes, and further configured to generate an output based on the combination.

15. The system according to claim 14, wherein, The signal generator includes a sine modulator.

16. The system according to claim 14, wherein, The signal generator is configured to use the sinusoidal signal to modulate the gain of the attenuator.

17. The system according to claim 14, wherein, The signal generator is configured to provide the sinusoidal signal to the attenuator during the scan sequence.

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