Multi-frequency area touch detection

Abstract

The input device includes a transmitter electrode disposed in a sensing region of the input device, a receiver electrode within the sensing region, and a processing system. The processing system includes a plurality of demodulators and is configured to simultaneously drive at least a subset of the transmitter electrodes with a number of transmitter signals having unique frequencies. The processing system is also configured to receive resultant signals at the receiver electrodes and demodulate the resultant signals with the plurality of demodulators to generate a number of sense signals, each of the demodulators operating at a different one of the unique frequencies.

Description

[Technical field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority under Article 8 of the Patent Cooperation Treaty to U.S. Patent Application No. 17 / 518,307, filed November 3, 2021, and U.S. Patent Application No. 17 / 564,159, filed December 28, 2021.

[0002] The described embodiments relate generally to electronic devices, and more specifically to touch sensors. [Background technology]

[0003] Input devices with touch sensor devices (e.g., touch pads and touch sensor devices) are widely used in various electronic systems. Touch sensor devices typically have a sensing area, often defined by a surface, where the touch sensor device identifies the presence, location and / or movement of one or more input objects. Touch sensor devices may be used to provide an interface for electronic systems. For example, touch sensor devices are often used as input devices for larger computing systems (e.g., invisible touch pads integrated into or peripheral to notebook or desktop computers). Touch sensor devices come in a variety of sizes. The number of sensor electrodes in a touch sensor device may depend on the size of the touch sensor device. In large touch sensor devices, the number of sensor electrodes may create problems, especially when higher time resolution of touch detection is desired. Summary of the Invention

[0004] In general, in one aspect, one or more embodiments relate to an input device that includes a plurality of transmitter electrodes disposed in a sensing region of the input device, a receiver electrode in the sensing region, and a processing system that includes a plurality of demodulators configured to simultaneously drive at least a subset of the plurality of transmitter electrodes with a plurality of transmitter signals having unique frequencies, receive resultant signals at the receiver electrodes, and demodulate the resultant signals with a plurality of demodulators to generate a plurality of sense signals, each of the plurality of demodulators operating at a different one of the unique frequencies.

[0005] In general, in one aspect, one or more embodiments relate to a processing system for an input device, the processing system including a plurality of demodulators configured to simultaneously drive at least a subset of a plurality of transmitter electrodes in a sensing region of the input device with a plurality of transmitter signals having unique frequencies, receive resultant signals at receiver electrodes in the sensing region, and demodulate the resultant signals with the plurality of demodulators to generate a plurality of sense signals, each of the plurality of demodulators operating at a different one of the unique frequencies.

[0006] In general, in one aspect, one or more embodiments relate to a method for operating an input device, the method including simultaneously driving at least a subset of a plurality of transmitter electrodes with a plurality of transmitter signals having unique frequencies, receiving resultant signals at receiver electrodes, demodulating the resultant signals with a plurality of demodulators to generate a plurality of sense signals, and performing touch sensing using the resultant signals, the plurality of transmitter electrodes and the receiver electrodes being disposed in a sense region of the input device, and each of the plurality of demodulators operating at a different one of the unique frequencies.

[0007] Other aspects of the embodiments will be apparent from the following description and the appended claims. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 illustrates a block diagram of an input device according to one or more embodiments.

[0009] [Diagram 2] FIG. 2 illustrates a sensing configuration according to one or more embodiments.

[0010] [Diagram 3] FIG. 3 illustrates a processing configuration according to one or more embodiments.

[0011] [Figure 4] FIG. 4 illustrates a flow chart illustrating a method for multi-frequency domain touch sensing in accordance with one or more embodiments.

[0012] [Diagram 5] FIG. 5 illustrates sample data according to one or more embodiments.

[0013] [Figure 6A] FIG. 6A illustrates a sensing configuration according to one or more embodiments.

[0014] [Figure 6B] FIG. 6B illustrates a sensing configuration according to one or more embodiments.

[0015] [Figure 7] FIG. 7 illustrates a processing configuration according to one or more embodiments.

[0016] [Figure 8] FIG. 8 illustrates an example of inter-band interference analysis in accordance with one or more embodiments.

[0017] [Figure 9] FIG. 9 illustrates a flow chart illustrating a method for inter-band harmonic interference mitigation for multi-frequency domain parallel scanning in accordance with one or more embodiments.

[0018] [Figure 10] FIG. 10 illustrates a flow chart illustrating a method for multi-frequency domain touch sensing in accordance with one or more embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The following detailed description is exemplary in nature and is not intended to limit the invention or its application and uses. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, summary, brief description of the drawings, or the following detailed description.

[0020] Throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives for elements (i.e., any noun in the application). With the exception of four consecutive quarter cycles, the use of the ordinal numbers does not imply or create a particular ordering of the elements, nor does it limit any element to being only a single element, unless expressly disclosed, for example, by use of the words "before," "after," "single," or other similar terminology. Rather, the use of the ordinal numbers is to distinguish elements from one another. By way of example, a first element is distinct from a second element, and a first element may encompass more than one element and follow (or precede) the second element in the ordering of the elements.

[0021] The use of ordinal numbers in relation to the four successive quarter cycles indicates an ordering among the four successive quarter cycles. In particular, a first successive quarter cycle is the first quarter cycle which precedes a second successive quarter cycle, which in turn precedes a third successive quarter cycle which in turn precedes a fourth (or final) successive quarter cycle.

[0022] Various embodiments provide input devices and methods that facilitate improved usability along with various other benefits. The embodiments of the present disclosure may be used to achieve high frame rates for touch sensing even with large sensing areas. The embodiments of the present disclosure simultaneously drive multiple sensing electrodes in a sensing area with transmitter signals having different frequencies. Simultaneous driving of multiple sensing electrodes can be performed at shorter time intervals than sequential driving of the same number of sensing electrodes. Thus, a larger number of sensing operations can be performed during a fixed time period. Thus, touch sensing can be performed for larger sensing areas without undesirable or unacceptable degradation of the frame rate used for detection. Similarly, frame rates can be increased for smaller sensing areas when using simultaneous driving of multiple sensing electrodes. As described in more detail below.

[0023] FIG. 1 is a block diagram of an exemplary input device (100), according to an embodiment. The input device (100) may be configured to provide input to an electronic system (not shown). In this document, the term "electronic system" (or "electronic device") broadly refers to any system capable of electronically processing information. Some non-limiting examples of electronic systems include personal computers, such as desktop computers, laptop computers, and netbook computers, tablets, web browsers, e-book readers, and personal digital assistants (PDAs). Additional examples of electronic systems include composite input devices, such as a physical keyboard that includes the input device (100) and a separate joystick or key switches. Further examples of electronic systems include peripherals, such as data input devices (including remote controllers and mice) and data output devices (including display screens and printers). Other examples include remote terminals, kiosks, and gaming devices (e.g., video game consoles and handheld gaming devices). Other examples include communication devices (including mobile phones such as smart phones), media devices (including recorders, editors, and players such as televisions, set-top boxes, music players, digital photo frames, digital cameras), etc. In addition, an electronic system may be both a host and a slave to an input device.

[0024] In FIG. 1, the input device (100) is illustrated as a touch sensitive device (e.g., a "touch pad" or "touch sensitive device") configured to detect input provided by one or more input objects within a sensing area (120). Examples of input objects include a stylus, an active pen (140), and a finger (142). Furthermore, which individual input objects are within the sensing area may change over the course of one or more gestures. For example, a first input object may be present in the sensing area to perform a first gesture, then the first input object and a second input object may be present in the surface sensing area, and finally, a third input object may perform a second gesture. To avoid unnecessarily complicating the description, the singular form of input object is used to refer to all of the above variations.

[0025] The sensing region 120 encompasses any space above, around, within, and / or near the input device 100 in which the input device 100 can sense user input (e.g., user input provided by one or more input objects). The size, shape, and location of individual sensing regions can vary widely depending on the embodiment.

[0026] The input device 100 may use any combination of sensor components and sensing technologies to detect user input within the sensing area 120. The input device 100 includes one or more sensing elements for detecting the user input, which may be capacitive.

[0027] In capacitive implementations of the input device 100, a voltage or current is applied to generate an electric field. A nearby input object causes a change in the electric field, resulting in a detectable change in capacitive coupling that can be detected as a change in voltage, current, etc.

[0028] Some capacitive implementations use an array of capacitive sensing elements or other regular or irregular patterns to generate an electric field. In some capacitive implementations, separate sensing elements are ohmically shorted to form a larger sensor electrode. Some capacitive implementations use a resistive sheet, which may be uniform in resistance.

[0029] Some capacitive implementations use a "self-capacitance" (or "absolute capacitance") sensing scheme based on the change in capacitive coupling between a sensor electrode and an input object. In various embodiments, an input object near the sensor electrode changes the electric field near the sensor electrode and therefore changes the measured capacitive coupling. In one implementation, an absolute capacitive sensing scheme works by modulating the sensor electrode relative to a reference voltage (e.g., system ground) and detecting the capacitive coupling between the sensor electrode and the input object. In various embodiments, the reference voltage may be a substantially constant voltage or a varying voltage. The reference voltage may be a system ground. Measurements obtained using an absolute capacitive sensing scheme may be referred to as absolute capacitive measurements.

[0030] Some capacitive implementations use a "mutual capacitance" (or "transcapacitive") sensing scheme based on changes in capacitive coupling between sensor electrodes. In various embodiments, an input object near the sensor electrodes changes the electric field between the sensor electrodes, thus changing the measured capacitive coupling. In one implementation, the mutual capacitance sensing scheme operates by detecting capacitive coupling between one or more transmitter sensor electrodes (also referred to as "transmitter electrodes" or "transmitters") and one or more receiver sensor electrodes (also referred to as "receiver electrodes" or "receivers"). The transmitter sensor electrodes may transmit a transmitter signal modulated relative to a reference voltage (e.g., system ground). The receiver sensor electrodes may be held substantially constant relative to the reference voltage to facilitate reception of the resulting signal. The reference voltage may be a substantially constant voltage, and in various embodiments, the reference voltage may be system ground.

[0031] In some embodiments, both the transmitter and receiver sensor electrodes may be modulated. The transmitter electrodes may be modulated to transmit a transmitter signal to the receiver electrodes to facilitate receiving a result signal. The result signal may include one or more transmitter signals and / or effects corresponding to one or more ambient interference sources (e.g., other electromagnetic signals). The effects may be the transmitter signal, changes in the transmitter signal caused by one or more input objects and / or ambient interference, or other similar effects. The sensor electrodes may be dedicated transmitters or receivers and may be configured to both transmit and receive. Measurements obtained using a mutual capacitance sensing scheme may be referred to as mutual capacitance measurements.

[0032] In FIG. 1, a processing system (110) is illustrated as part of the input device (100). The processing system (110) is configured to operate the hardware of the input device (100) to detect inputs in the sensing area (120). The processing system (110) may include some or all of one or more integrated circuits (ICs) and / or other circuit components. For example, a processing system (110) for a mutual capacitance sensor device may include transmitter circuitry configured to transmit signals using transmitter sensor electrodes and / or receiver circuitry configured to receive signals using receiver sensor electrodes. Further, a processing system (110) for an absolute capacitance sensor device may include driver circuitry configured to apply absolute capacitance signals to the sensor electrodes and / or receiver circuitry configured to receive signals at those sensor electrodes. In one or more embodiments, a processing system (110) for a mutual and absolute capacitance composite sensor device may include any combination of the mutual and absolute capacitance circuitry described above. The processing system 110 may further include receiver circuitry configured to receive signals emitted by different signal sources, such as signals emitted by an active pen 140. Signals from the active pen 140 may be received by receiver sensor electrodes, and transmitted signals are not necessarily emitted by transmitter sensor electrodes.

[0033] In some embodiments, the processing system (110) may also include electronically readable instructions, such as firmware code, software code, and the like. In some embodiments, the components that make up the processing system (110) may be located together, such as near the sensing elements of the input device (100). In other embodiments, the components of the processing system (110) may be physically separated, with one or more components near the sensing elements of the input device (100) and one or more components at other locations. For example, the input device (100) may be a peripheral device coupled to a computing device, and the processing system (110) may comprise software configured to run on a central processing unit of the computing device and one or more ICs (possibly associated with firmware) separate from the central processing unit. As another example, the input device (100) may be physically integrated into a mobile device, and the processing system (110) may comprise circuitry and firmware that is part of the mobile device's main processor. In some embodiments, the processing system (110) may be dedicated to implementing the input device (100). In other embodiments, the processing system (110) performs other functions as well, such as operating the display screen (155) and driving haptic actuators.

[0034] The processing system 110 may be implemented as a set of modules that handle different functions of the processing system 110. Each module may comprise circuitry, firmware, software, or a combination thereof that is part of the processing system 110. In various embodiments, different combinations of modules may be used. For example, as shown in FIG. 1, the processing system 110 may comprise a determination module 150 and a sensor module 160. The determination module 150 may be capable of determining, if at least one input object is present in the sensing area, a signal-to-noise ratio, position information of the input object, a gesture, an action to be performed based on the gesture, a combination of gestures or other information, and / or other actions.

[0035] The sensor module 160 is operable to drive the sensing elements to transmit transmitter signals and receive result signals. For example, the sensor module 160 may include sensor circuitry coupled to the sensing elements. The sensor module 160 may include, for example, a transmitter module and a receiver module. The transmitter module may include transmitter circuitry coupled to a transmitting portion of the sensing elements. The receiver module may include receiver circuitry coupled to a receiving portion of the sensing elements and may be operable to receive result signals. The receiver module of the sensor module 160 may receive result signals from the sensor electrodes in the electrode pattern using, for example, a capacitive sense signal having a sense frequency generated by the transmitter module. The result signals may include desired signals, such as active pen data and signal components caused by the presence of an input object in the vicinity of the electrode pattern, and undesired signals, such as noise and interference. As described in more detail below, the sensor module 160 may perform one or more demodulation operations on the result signals.

[0036] Although FIG. 1 illustrates a determination module (150) and a sensor module (160), alternative or additional modules may be present according to one or more embodiments. Such alternative or additional modules may correspond to other modules or sub-modules than one or more of the modules discussed above. Examples of alternative or additional modules include a hardware operation module for operating hardware, such as the sensor electrodes and the display screen (155), a data processing module for processing data, such as the sensor signals and position information, a reporting module for reporting information, an identification module configured to identify a gesture, such as a mode change gesture, and a mode change module for changing an operating mode. Furthermore, various modules may be combined in separate integrated circuits. For example, a first module may be included at least partially in a first integrated circuit and another module may be included at least partially in a second integrated circuit. Furthermore, portions of a single module may span multiple integrated circuits. In some embodiments, the processing system may perform the operations of the various modules as a whole.

[0037] In some embodiments, the processing system (110) responds to the user input (or lack of user input) in the sensing area (120) by directly initiating one or more actions. Examples of actions include graphical user interface (GUI) actions such as cursor movement, selection, menu navigation, and other functions, as well as changes in operational mode. In some embodiments, the processing system (110) provides information about the input (or lack of input) to some portion of the electronic system (e.g., to a central processing system of the electronic system, if such a central processing system exists, separate from the processing system (110)). In some embodiments, some portion of the electronic system processes information received from the processing system (110) to act on the user input to facilitate general actions, such as mode change actions or GUI actions.

[0038] In some embodiments, the input device (100) includes a touch screen interface and a sensing area (120) that overlaps at least a portion of an active area of ​​the display screen (155). For example, the input device (100) may include a substantially transparent sensor electrode that overlaps the display screen to provide a touch screen interface to an associated electronic system. The display screen may be any type of dynamic display capable of displaying a visual interface to a user and may include any type of light emitting diode (LED), organic light emitting diode (OLED), cathode ray tube (CRT), liquid crystal display (LCD), plasma, organic luminescent (EL) or other display technology. The input device (100) and the display screen (155) may share physical elements. For example, some embodiments use some of the same electrical components for display and sensing. In various embodiments, one or more display electrodes of the display device may be configured to both display updates and input sensing. As another example, the display screen (155) may be partially or fully operated by the processing system (110).

[0039] 1 illustrates an arrangement of components, other arrangements may be used without departing from the scope of this disclosure. For example, various components may be combined to create a single component. As another example, functions performed by a single component may be performed by two or more components. Additionally, although an arrangement for touch sensing is described, other variables may be sensed, such as force.

[0040] FIG. 2 illustrates a sensing configuration 200 according to one or more embodiments. The sensing configuration 200 relies on an arrangement of sensor electrodes within a sensing region 120. Transmitter (Tx) electrodes 220 and receiver (Rx) electrodes 230 may be provided in the sensing region 120. In the example of FIG. 2, the Tx electrodes 220 are elongated rectangular structures arranged in columns, while the Rx electrodes 230 are elongated rectangular structures arranged in rows. In general, Tx and Rx electrodes of any shape may be used.

[0041] In one or more embodiments, the Tx electrode (220) and the Rx electrode (230) together implement mutual capacitance or trans-capacitive sensing. At the intersection of the Tx electrode (220) and the Rx electrode (230), a local capacitive coupling is formed between a portion of the Tx electrode (220) and the Rx electrode (230). This area of ​​local capacitive coupling may be referred to as a "capacitive pixel" and may also be referred to herein as a sensing element (225). A trans-capacitance Ct is associated with the sensing element (225). When an input object (not shown) approaches the sensing element (225), the trans-capacitance Ct may change by an amount ΔCt. Thus, the presence or absence of the input object may be detected by monitoring ΔCt. ΔCt may be measured by applying a transmitter signal (222) to the Tx electrode (220) and receiving a result signal (232) from the Rx electrode (230). The resulting signal is a function of the transmitter signal and ΔCt, depending on the presence or absence of an input object, which may be acquired for multiple sensing elements, for example, to generate a capacitance image across the sensing region 120.

[0042] In one or more embodiments, multiple Tx electrodes (220) are driven simultaneously. In the example of FIG. 2, three Tx electrodes are driven simultaneously to transmit the transmitter signal T XF1 , T XF2 and T XF3 When driven by (222), Rx electrode R x1 …R Xn The result signal (232) on each of (230) is T XF1 , T XF2and T XF3 Each of the result signals (232) may thus carry information regarding the presence or absence of an input object in the vicinity of the three detector elements (225).

[0043] As described with reference to FIG. 3, demodulation may be performed to obtain separate sense signals for each of the three sense elements (225). The described operation is performed by detecting the Rx electrodes R X1 …R Xn The operation can then be performed on each of the resulting signals (232) on (230). To obtain a complete capacitance image, the operation is then repeated for the same T XF1 , T XF2 and T XF3 This repetition may be repeated for the other set of three Tx electrodes using . This repetition may continue until all Tx electrodes (220) are driven. For purposes of driving the Tx electrodes (220), the Tx electrodes may be grouped by frequency domain. Based on the use of three frequencies for simultaneous driving in the example of FIG. 2, the sensing configuration (200) includes three frequency domains (242, 244, and 246).

[0044] Each of the three frequency regions (242, 244, 246) includes the same or nearly the same number of Tx electrodes. For example, if the sensing configuration (200) includes 60 Tx electrodes, each of the frequency regions (242, 244, 246) may include 20 Tx electrodes. One Tx electrode from each group may be selected for simultaneous drive. For example, as shown in FIG. 2, the leftmost Tx electrode in each of the frequency regions (242, 244, 246) may be selected for simultaneous drive. Then, the immediately adjacent Tx electrode in each of the frequency regions (242, 244, 246) may be selected for simultaneous drive. A complete capacitive image may be obtained when all Tx electrodes (220) in all three frequency regions (242, 244, 246) are driven once and corresponding result signals (232) are received on the Rx electrodes (230).

[0045] In one or more embodiments, multiple Tx electrodes (220) are driven simultaneously. In the example of FIG. 2, assume that multiple Tx electrodes in the Frequency 1 domain (242) are driven simultaneously with multiple Tx electrodes in the Frequency 2 domain (244) and multiple Tx electrodes in the Frequency 3 domain (246). The simultaneously driven Tx electrodes in the Frequency 1 domain (242) may be driven with a transmitter signal having a first frequency, the simultaneously driven Tx electrodes in the Frequency 2 domain (244) may be driven with a transmitter signal having a second frequency, and the simultaneously driven Tx electrodes in the Frequency 3 domain (246) may be driven with a transmitter signal having a third frequency. If the frequencies of the transmitter signals are selected to satisfy certain orthogonality principles (discussed below with reference to FIG. 3), signal processing may be performed separately for the different frequency domains with no or minimal interference. To enable localization of touch at individual sensing elements (225), they may be repeatedly driven with bursts of transmitter signals (222), as described in the example below. In this example, let us assume that there are 20 Tx electrodes (220) per frequency region (242, 244, 246), i.e., 60 Tx electrodes in total assuming three frequency regions. Thus, in this example, there are 20 sensing elements (225) per frequency region per Rx electrode intersected by 20 Tx electrodes. To be able to assess the presence or absence of touch at each of the 20 sensing elements (225), the 20 Tx electrodes are driven simultaneously 20 times, in sequence, with a burst pattern having a sequence of 20 bursts that allows for a unique solution of a system of equations with 20 unknowns. While the frequency of the transmitter signal used within the sensing region may be the same for the entire burst pattern, the phase of the transmitter signal may differ across the series of bursts within the burst pattern and across the Tx electrodes being driven. By processing the resulting signal (232) obtained on a single Rx electrode in response to the 20 bursts on all 20 Tx electrodes, a ΔCt may be determined for each of the sensing elements.The same operation may be performed simultaneously on all resultant signals (232) on all Rx electrodes (230). The same operation may also be performed simultaneously in other frequency regions. Thus, in this example with three frequency regions, a total of 60 Tx electrodes may be driven simultaneously with a series of 20 bursts each of the transmitter signal.

[0046] In the example of FIG. 2, the simultaneous driving of the Tx electrodes (220) can reduce the time required to obtain a complete capacitive image by a factor of three, assuming no other parameters are adjusted. For example, assuming a required frame rate of 240 fps for a 17-inch touchscreen with 60 Tx electrodes, the time available to drive the Tx electrodes in one burst of the transmitter signal would be limited to 1 / (240×60)=70 μs. This may reduce noise immunity. In contrast, if a set of Tx electrodes is driven simultaneously across three frequency ranges, the time available to drive the Tx electrodes per burst would be 1 / (240×20)=210 μs. This may provide superior noise immunity without reducing the frame rate. The same may be true for smaller touchscreens operating at higher frame rates, e.g., 480 fpx or 600 fps.

[0047] While FIG. 2 illustrates a particular sensing configuration, and the example describes a particular touch screen scenario, embodiments of the present disclosure may be used with many different configurations. For example, embodiments of the present disclosure may use different types of electrode arrangements, may drive fewer or more Tx electrodes simultaneously, may cover larger or smaller sensing areas, etc. Although FIG. 2 suggests a particular order for driving the set of three Tx electrodes (220) simultaneously, any order may be used to drive the Tx electrodes without departing from the present disclosure. Additionally, while FIG. 2 illustrates a particular configuration of frequency domains (242, 244, 246), the frequency domains may be in different configurations. For example, the frequency domains need not be contiguous, the same number of Tx electrodes may be randomly assigned to frequency domains, etc.

[0048] FIG. 3 illustrates a processing arrangement (300) according to one or more embodiments. The processing arrangement (300) may be used in conjunction with the sensing arrangement (200) of FIG. 2. Specifically, in the example illustrated in FIG. 3, transmitter signals of three different frequencies are emitted simultaneously to drive the Tx electrodes (220) (e.g., as illustrated in FIG. 2). FIG. 3 illustrates processing of a result signal (332) obtained at one of the Rx electrodes (230). To process multiple result signals on multiple Rx electrodes, the processing arrangement (300) may be implemented to operate multiple times in parallel. For example, for n Rx electrodes, the components illustrated in FIG. 3 may be implemented n times.

[0049] The processing implementation (300) includes an analog front end (340) and a digital processing block (360). The analog front end (340) may include a charge integrator (342) and an analog-to-digital converter (ADC) (344). The digital processing block (360) may include operations implementing a set of demodulators (362). In the illustrated example, the digitally implemented set of demodulators (362) demodulates the result signal (332) obtained by the analog front end (340) to generate a sense signal (364). The sense signal (364) may provide a measurement of the transformer capacitance of the three sensing elements (225) and may therefore indicate the presence or absence of an input object (not shown). Additional downstream operations may be performed on the sense signal (364) to perform touch sensing. A detailed description is provided below.

[0050] In one or more embodiments, the transmitter signals for simultaneously driving a set of transmitter electrodes (230) have different frequencies. More specifically, each of the simultaneously driven transmitter electrodes is driven with a transmitter signal (322) of one unique frequency. In one or more embodiments, the transmitter signals (322) used for simultaneous driving are orthogonal. In one or more embodiments, the transmitter signals (322) used for simultaneous driving are selected from an orthogonal frequency division multiplexing (OFDM) spectrum of subcarriers, as illustrated in FIG. 3. FIG. 3 illustrates an example OFDM spectrum with eleven subcarriers. Any of the subcarriers may be used due to the orthogonality of the subcarriers. For example, ω 0The subcarrier at the first frequency and the subcarriers immediately to the left and right may be selected to obtain a transmitter signal (322) having three different frequencies. Bursts of the transmitter signal (322) may then be used to simultaneously drive Tx electrodes (220) in the sensing region (120). A first of the three frequencies may be used to drive Tx electrodes in a frequency 1 region (242), a second of the three frequencies may be used to drive Tx electrodes in a frequency 2 region (244), and a third of the three frequencies may be used to drive Tx electrodes in a frequency 3 region (246). Although a single frequency may be used in a frequency region, the phase of the transmitter signal in the frequency region may be different between electrodes and / or between successive bursts of the transmitter signal. In one embodiment, the phase may be changed by 180 degrees to use a transmitter signal and an inverted transmitter to drive the Tx electrodes. Any other phase change may be used without departing from this disclosure.

[0051] A single result signal R XF1、F2、F3 A result signal R (332) may be obtained from one Rx electrode (232) for further processing. XF1、F2、F3 (332) may include the effect of the transmitter signal (322) being radiated at all sensing elements (225) corresponding to Tx electrodes driven with transmitter signals having three different frequencies and different phases. An example is provided in FIG. 5. The result signal R XF1、F2、F3 (332) may further include the effect of the presence or absence of an input object at the sensing element (225).

[0052] The charge integrator (342) outputs a result signal R XF1、F2、F3 (332) and outputs the result signal R over an integration period. XF1、F2、F3 (332) may be integrated. The ADC (344) outputs the integrated result signal R XF1、F2、F3 (332) and performs analog-to-digital conversion. Further discussion of the ADC is provided below.

[0053] The output of the ADC is provided to a set of digitally implemented demodulators (362). In one or more embodiments, the demodulators (362) are configured to generate a detected signal (364). In one or more embodiments, the demodulators (362) include demodulators for in-phase (I) demodulation and quadrature (Q) demodulation dedicated to each of the unique frequencies of the three transmitter signals (322). In other words, as shown in FIG. 3, there may be six demodulators (three I demodulators and three Q demodulators) configured to perform three I / Q demodulations. Each of the six demodulators may include multiplier and windowing operations to generate the I and Q components of the detected signal. The multipliers are connected to their inputs (i.e., the integrated and analog-to-digital converted result signal R XF1、F2、F3 The demodulation may be performed by multiplying the mixer result (332) with a demodulation waveform. The windowing operation may perform low-pass filtering, for example a weighted average of the mixer result (resulting from the multiplier operation). The demodulation waveform may be based on the transmitter signal (322).

[0054] Specifically, each of the multipliers may be provided with a copy of one of the three transmitter signals (322) and perform demodulation at the frequency of the provided transmitter signal. The demodulators (362) then combine and perform code division multiplexing (CDM) decoding at each of the three frequencies to separate the detected signals (364) corresponding to the three detector elements (225). The demodulated I and Q components of the detected signal corresponding to a detector element may be combined to obtain an acceptably accurate detected signal, even in the presence of possible phase shifts.

[0055] Using this IQ complex demodulation, the integrated and analog-to-digital converted result signal R XF1、F2、F3Precise phase matching between (332) and the demodulation waveform is not necessary to perform the demodulation. As a result, the ADC (344) may be relatively slow, for example 3 to 5 times the speed of the transmitter signal frequency. This may introduce a phase offset, which is mitigated by the use of IQ complex demodulation. The use of a slow ADC reduces power consumption and cost, while the additional Q demodulator is digitally implemented and therefore associated with negligible additional cost and power. Thus, the above-described configuration using digital I / Q demodulation and analog-to-digital conversion before demodulation is cost-effective and energy-efficient. Although digital I / Q demodulation has been described, analog I / Q demodulation followed by analog-to-digital conversion may be performed without departing from this disclosure.

[0056] In one embodiment, only an I demodulator (without a Q demodulator) is used to perform the demodulation. To obtain a satisfactory but not perfect phase alignment using only an I demodulator, a faster ADC (344) may be used to reduce possible phase offsets. For example, the ADC may operate at least 16 times the speed of the transmitter signal frequency.

[0057] Although Figure 3 illustrates a particular processing configuration, other configurations may be used without departing from this disclosure. For example, although Figure 3 illustrates the simultaneous driving of three Tx electrodes with transmitter signals having three unique frequencies, any number of Tx electrodes may be driven simultaneously. Additionally, although Figure 3 illustrates a processing configuration for processing a single resultant signal obtained from three Rx electrodes, multiple analog and digital processing components such as those illustrated may be used to process additional resultant signals.

[0058] FIG. 4 illustrates a flow chart in accordance with one or more embodiments. One or more steps of FIG. 4 may be performed by components discussed above with reference to FIG. 1, FIG. 2, and FIG. 3. Although the various steps of this flow chart are presented and described sequentially, one skilled in the art will understand that at least some of the blocks may be performed in a different order, combined, or omitted, and some of the blocks may be performed in parallel. Additional steps may also be performed. Thus, the scope of the disclosure should not be considered limited to the particular arrangement of the steps of FIG. 4.

[0059] The flow chart of FIG. 4 illustrates a method (400) for multi-frequency domain touch sensing in accordance with one or more embodiments.

[0060] In step 402, a set of Tx electrodes are simultaneously driven with multiple transmitter signals having unique frequencies. Any number of Tx electrodes may be simultaneously driven. Additional details are described with reference to Figures 2 and 3.

[0061] In step 404, a result signal is obtained on the Rx electrode. Step 404 may be performed in parallel with step 402. Furthermore, step 404 may be performed simultaneously for multiple Rx electrodes. The result signal received on the Rx electrode is affected by multiple transmitter signals coupled to the Rx electrode. Coupling occurs where the Rx electrode is spatially close to the Tx electrode (e.g., at the sensing element where the Tx electrode crosses the Rx electrode). Since capacitive coupling is affected by the presence or absence of an input object, the result signal is also affected by the presence or absence of an input object near the sensing element.

[0062] In step 406, the resultant signal is demodulated to generate a set of sensed signals. One resultant signal may be obtained for each of one or more Tx electrodes driven with a transmitter signal having a particular frequency. If both I and Q demodulation are performed, the I and Q components of the resulting sensed signal may be processed to determine the amplitude and / or phase of the sensed signal. Additional details are described with reference to Figures 2 and 3. Additional steps may be performed before demodulation. For example, the resultant signal may be integrated and / or analog-to-digital converted as described above. A solution for the sensed signal specific to an individual sense element may be obtained by evaluating the sensed signal over multiple bursts of the transmitter signal. For example, for a configuration including 20 sense elements, 20 bursts may be used to obtain a unique solution. If step 404 is performed for multiple Rx electrodes, step 406 may also be performed multiple times to demodulate each of the resultant signals corresponding to the multiple Rx electrodes.

[0063] The above steps may be repeated. For example, steps 402-406 may be repeated while driving a different set of Tx electrodes selected from the Tx electrodes in the frequency domain as described above with reference to Figures 2 and 3. A capacitance image with sensed signals corresponding to the complete set of sensing elements of the capacitance image may be available after performing steps 402-406 for all Tx electrodes in the sensing region.

[0064] In step 408, touch detection may be performed using the detection signals. Touch detection may involve evaluating the detection signals against a previously determined baseline value. If the detection signal deviates from the baseline by at least a certain amount, an input object may be considered to be present in the vicinity of the detection element corresponding to the detection signal. Step 408 may be performed for some or all of the detection signals corresponding to the detection elements of the capacitive image.

[0065] To perform touch detection over time, steps 402-408 may be repeated, for example, periodically.

[0066] 5 illustrates sample data (500) according to one or more embodiments. The sample is for three Tx electrodes driven simultaneously with three transmitter signals having three unique frequencies: 100 kHz, 109.9 kHz, and 119.8 kHz. The three frequencies are selected from an OFDM spectrum (e.g., as illustrated in FIG. 3).

[0067] The resulting signal at the Rx electrodes is shown in the time domain (502). It is also shown in the frequency domain (504). Although the resolution of the frequency spectrum (obtained using an FFT applied to a single burst of the transmitter signal) is not sufficient to distinguish between the three Tx frequencies, the contributions from the three transmitter signals are clearly distinguishable. The contribution from a noise signal at 50 kHz is also visualized.

[0068] The embodiments of the present disclosure have various advantages. The use of simultaneously emitted transmitter signals having different frequencies allows touch sensing over a large sensing area using relatively high frame rates without compromising noise immunity. In particular, the embodiments of the present disclosure allow driving a large number of Tx electrodes (which may be necessary for larger touch screens) at high frame rates without shortening the burst of emitted transmitter signal, since multiple transmitter electrodes may be driven simultaneously at different frequencies. A high degree of noise immunity is achieved when using burst lengths as proposed. Furthermore, the embodiments of the present disclosure allow the addition of other bursts (e.g., for noise measurements, absolute capacitive sensing, etc.) without significant changes to the timing. For example, in an example requiring 20 bursts per frame, the time required to add a burst to complete a frame would increase by only 5%. The embodiments of the present disclosure are cost-effective and energy-efficient, since a relatively slow ACD may be used and many demodulation operations can be performed digitally using standard DSPs. The embodiments of the present disclosure also allow the use of transmitter signals based on waveforms that contain many harmonics. For example, compared to using a sine wave, a trapezoidal wave may be used, which may have several advantages, such as being relatively easy to generate high voltages using, for example, a stack of transistors, and being able to operate using lower transmit power (because for a 1V square wave, the amplitude of the fundamental waveform is 1.27V).

[0069] In one or more embodiments, a non-sinusoidal transmitter signal is used to simultaneously drive the sensing electrodes. The use of a non-sinusoidal transmitter signal has various advantages, but can lead to the emission of harmonics. One or more embodiments mitigate interference that may result from the presence of harmonics. A detailed description is provided below.

[0070] FIG. 6A illustrates a sensing configuration (600) according to one or more embodiments. The sensing configuration (600) relies on an arrangement of sensor electrodes within a sensing region (120). Transmitter (Tx) electrodes (620) and receiver (Rx) electrodes (630) may be provided within the sensing region (120). In the example of FIG. 6A, the Tx electrodes (620) are elongated rectangular structures arranged in columns, and the Rx electrodes (630) are elongated rectangular structures arranged in rows. In general, any shape of Tx and Rx electrodes may be used.

[0071] In one or more embodiments, the Tx electrode (620) and the Rx electrode (630) together implement mutual capacitance or trans-capacitive sensing. At the intersection of the Tx electrode (620) and the Rx electrode (630), a localized capacitive coupling is formed between a portion of the Tx electrode (620) and the Rx electrode (630). This area of ​​localized capacitive coupling may be referred to as a "capacitive pixel" and may also be referred to herein as a sensing element (625). A transformer capacitance Ct is associated with the sensing element (625). When an input object (not shown) approaches the sensing element (625), the transformer capacitance Ct may change by an amount ΔCt. Thus, the presence or absence of the input object may be detected by monitoring ΔCt. ΔCt may be measured by applying a transmitter signal (622) to the Tx electrode (620) and receiving a resultant signal (632) from the Rx electrode (630). The resulting signal is a function of the transmitter signal and ΔCt, depending on the presence or absence of an input object, which may be acquired for multiple sensing elements, for example, to generate a capacitance image across the sensing region 120.

[0072] In one or more embodiments, multiple Tx electrodes (620) are driven simultaneously. In the example of FIG. 6A, three Tx electrodes transmit the transmitter signal T XF1 , T XF2 and T XF3 When driven simultaneously by (622), each Rx electrode R x1 …R Xn The result signal (632) on (630) is T XF1 , T XF2 and TXF3 Each of the result signals (632) may thus carry information regarding the presence or absence of an input object in the vicinity of the three detector elements (625).

[0073] As described with reference to FIG. 7, demodulation may be performed to obtain separate sense signals for each of the three sense elements (625). The described operation is performed by detecting the Rx electrodes R X1 …R Xn The operation can then be performed on each of the resulting signals (632) on (630). To obtain a complete capacitance image, the operation can then be repeated for the same T XF1 , T XF2 and T XF3 This repetition may be repeated for another set of three Tx electrodes using . This repetition may continue until all Tx electrodes (620) are driven. For purposes of driving the Tx electrodes (620), the Tx electrodes may be grouped by frequency domain. Based on the use of three frequencies for simultaneous driving in the example of FIG. 6A, the sensing configuration (600) includes three frequency domains (642, 644, and 646).

[0074] Each of the three frequency regions (642, 644, 646) includes the same or nearly the same number of Tx electrodes. For example, if the sensing configuration (600) includes 60 Tx electrodes, then each of the frequency regions (642, 644, 646) may include 20 Tx electrodes. One Tx electrode from each group may be selected for simultaneous drive. For example, as shown in FIG. 6A, the leftmost Tx electrode in each of the frequency regions (642, 644, 646) may be selected for simultaneous drive. Then, the immediately adjacent Tx electrode in each of the frequency regions (642, 644, 646) may be selected for simultaneous drive. A complete capacitive image may be obtained once all Tx electrodes (620) in all three frequency regions (642, 644, 646) have been driven once and corresponding result signals (632) have been received on the Rx electrodes (630).

[0075] In one or more embodiments, multiple Tx electrodes (620) are driven simultaneously. In the example of FIG. 6A, let us assume that multiple Tx electrodes in the Frequency 1 region (642) are driven simultaneously with multiple Tx electrodes in the Frequency 2 region (644) and multiple Tx electrodes in the Frequency 3 region (646). The simultaneously driven Tx electrodes in the Frequency 1 region (642) may be driven with a transmitter signal having a first frequency, the simultaneously driven Tx electrodes in the Frequency 2 region (644) may be driven with a transmitter signal having a second frequency, and the simultaneously driven Tx electrodes in the Frequency 3 region (646) may be driven with a transmitter signal having a third frequency. If the frequencies of the transmitter signals are selected to satisfy certain orthogonality principles (discussed below with reference to FIG. 7), signal processing may be performed separately for the different frequency regions with no or minimal interference. To enable localization of touch at individual sensing elements (625), they may be repeatedly driven with bursts of transmitter signals (622), as described in the example below. In this example, let us assume that there are 20 Tx electrodes (620) per frequency region (642, 644, 646), i.e., 60 Tx electrodes in total assuming three frequency regions. Thus, in this example, there are 20 sensing elements (625) per frequency region per Rx electrode intersected by 20 Tx electrodes. To be able to assess the presence or absence of touch at each of the 20 sensing elements (625), the 20 Tx electrodes are driven simultaneously 20 times, in sequence, with a burst pattern of 20 successive bursts that allows for a unique solution of a system of equations with 20 unknowns. While the frequency of the transmitter signal used within the sensing region may be the same for the entire burst pattern, the phase of the transmitter signal may differ across the bursts in the burst pattern and across the Tx electrodes driven. A ΔCt may be determined for each of the sensing elements by processing a resultant signal (632) obtained on a single Rx electrode in response to the 20 bursts on all 20 Tx electrodes. The same operation may be performed simultaneously for all resultant signals (632) on all Rx electrodes (630).The same operations may also be performed simultaneously in other frequency regions, so in this example with three frequency regions, a total of 60 Tx electrodes may be simultaneously driven with a series of 20 bursts each of the transmitter signal.

[0076] In the example of FIG. 6A, the simultaneous driving of the Tx electrodes (620) can reduce the time required to obtain a complete capacitive image by a factor of three, assuming no other parameters are adjusted. For example, assuming a required frame rate of 240 fps for a 17-inch touchscreen with 60 Tx electrodes, the time available to drive the Tx electrodes in one burst of the transmitter signal would be limited to 1 / (240×60)=70 μs. This may reduce noise immunity. In contrast, if a set of Tx electrodes is driven simultaneously across three frequency ranges, the time available to drive the Tx electrodes per burst would be 1 / (240×20)=210 μs. This may provide superior noise immunity without reducing the frame rate. The same may be true for smaller touchscreens operating at higher frame rates, e.g., 480 fps or 600 fps.

[0077] Figure 6B illustrates a sensing configuration 650 according to one or more embodiments. The physical configuration of the sensing configuration, including the placement of the Tx electrodes 620 and Rx electrodes 630, may be as described with reference to Figure 6A.

[0078] In one or more embodiments, multiple Tx electrodes (620) are driven simultaneously. In the example of FIG. 6B, n Tx electrodes are driven simultaneously to transmit the transmitter signal T XF1 …T XFn The n Tx electrodes may include a subset of all the Tx electrodes in the sensing region (120), or may include all of the Tx electrodes in the sensing region. Thus, each Rx electrode R x1 …R Xn The result signal (662) on (630) is T XF1 …T XFnEach of the result signals (662) may thus carry information about the presence or absence of an input object in the vicinity of the sensing element (655). XF1 …T XFn (652) may be selected to be mutually orthogonal. The above described operation is x1 …R Xn This may be performed for each of the result signals (662) on (630).

[0079] As discussed above with reference to Figure 6A, in the example of Figure 6B, the time required to acquire a complete capacitive image can be reduced by simultaneously driving the Tx electrodes (620). The amount of reduction can depend on various factors, such as, for example, how many Tx electrodes are driven simultaneously and the burst pattern used to drive the Tx electrodes.

[0080] 6A and 6B illustrate separate sensing configurations, and the examples describe particular touch screen scenarios, embodiments of the present disclosure may be used with many different configurations, for example, embodiments of the present disclosure may use different types of electrode arrangements, may drive fewer or more Tx electrodes simultaneously, may target larger or smaller sensing areas, etc.

[0081] FIG. 7 illustrates a processing configuration (700) according to one or more embodiments. The processing configuration (700) may be used with the sensing configuration (600) of FIG. 6A. A modified processing configuration (with an additional demodulator) may be used with the sensing configuration (650) of FIG. 6B. Specifically, in the example illustrated in FIG. 7, transmitter signals (722) having three different frequencies are emitted simultaneously to drive the Tx electrodes (620) (e.g., as illustrated in FIG. 6A). The nature of the transmitter signals (722) is discussed below. FIG. 7 illustrates the processing of a result signal (732) obtained at one of the Rx electrodes (630). To process multiple result signals on multiple Rx electrodes, the processing configuration (700) may be implemented to operate multiple times in parallel. For example, for n Rx electrodes, the components illustrated in FIG. 7 may be implemented n times.

[0082] The processing implementation (700) includes an analog front end (740) and a digital processing block (760). The analog front end (740) may include a charge integrator (742) and an analog-to-digital converter (ADC) (744). The digital processing block (760) may include operations implementing a set of demodulators (762). In the illustrated example, the digitally implemented set of demodulators (762) demodulates the result signal (732) obtained by the analog front end (740) to generate a sense signal (764). The sense signal (764) may provide a measurement of the transformer capacitance at the three sensing elements (625) and may therefore indicate the presence or absence of an input object (not shown). Additional downstream operations may be performed on the sense signal (764) to perform touch sensing. A detailed description is provided below.

[0083] Each of the simultaneously driven transmitter electrodes is driven by a non-sinusoidal transmitter signal (722) having a unique frequency (e.g., using a trapezoidal or square waveform with a unique fundamental frequency). In one or more embodiments, the non-sinusoidal transmitter signals (722) used for simultaneous driving are orthogonal. With reference to FIG. 6A, bursts of non-sinusoidal transmitter signals may be used to simultaneously drive Tx electrodes (620) in the sensing region (120). A first of the three frequencies may be used to drive Tx electrodes in a frequency 1 region (642), a second of the three frequencies may be used to drive Tx electrodes in a frequency 2 region (644), and a third of the three frequencies may be used to drive Tx electrodes in a frequency 3 region (646). Although only a single frequency may be used in a frequency domain, the phase of the non-sinusoidal transmitter signal within the frequency domain may be different between electrodes and / or between successive bursts of the non-sinusoidal transmitter signal. In one embodiment, the phase may be changed by 180° to use a non-sinusoidal transmitter signal and an inverted non-sinusoidal transmitter to drive the Tx electrodes. Any other phase change may be used without departing from this disclosure.

[0084] A single result signal R XF1、F2、F3 A result signal R (732) may be obtained from one Rx electrode (632) for further processing. XF1、F2、F3 (732) may include the effect of the non-sinusoidal transmitter signal (722) radiated at all sensing elements (625) corresponding to the Tx electrodes driven with the non-sinusoidal transmitter signal having three different fundamental frequencies and different phases. XF1、F2、F3 (732) may further include the effect of the presence or absence of an input object at the sensing element (625).

[0085] The charge integrator (742) outputs a result signal R XF1、F2、F3 (732) and outputs the result signal R over an integration period. XF1、F2、F3(732) may be integrated. The ADC (744) outputs the integrated result signal R XF1、F2、F3 (332) and performs analog-to-digital conversion.

[0086] The output of the ADC is provided to a set of digitally implemented demodulators (762). In one or more embodiments, the demodulators (762) are configured to generate a detected signal (764). In one or more embodiments, the demodulators (762) include demodulators for in-phase (I) demodulation and quadrature (Q) demodulation dedicated to each of the unique frequencies of the three non-sinusoidal transmitter signals (722). In other words, as shown in FIG. 7, there may be six demodulators (three I demodulators and three Q demodulators) configured to perform three I / Q demodulations. Each of the six demodulators may include multiplier and windowing operations to generate the I and Q components of the detected signal. The multipliers may be coupled to their inputs (i.e., the integrated and analog-to-digital converted result signal R XF1、F2、F3 The demodulation waveform is performed by multiplying the mixer result (732) by the demodulation waveform. The windowing operation may perform low-pass filtering, such as a weighted average of the mixer result (resulting from the multiplication operation). As discussed further below, the windowing operation may pass a signal at the fundamental frequency of the corresponding non-sinusoidal transmitter signal while strongly attenuating the fundamental frequency of the other (orthogonal) non-sinusoidal transmitter signal. The demodulation waveform may be based on the non-sinusoidal transmitter signal (722). For example, the demodulation waveform may be a sinusoidal waveform at the fundamental frequency of the corresponding non-sinusoidal transmitter signal.

[0087] Thus, each of the demodulators performs demodulation at the fundamental frequency of the corresponding non-sinusoidal transmitter signal. In combination, the demodulators (762) perform code division multiplexing (CDM) decoding at each of the three fundamental frequencies to separate the detected signals (764) corresponding to the three detector elements (625). The demodulated I and Q components of the detected signal corresponding to a detector element can be combined to obtain an acceptably accurate detected signal, even in the presence of possible phase shifts.

[0088] Using this IQ complex demodulation, the integrated and analog-to-digital converted result signal R XF1、F2、F3 Precise phase matching between (732) and the demodulation waveform is not necessary to perform the demodulation. As a result, the ADC (744) may be relatively slow, for example 3 to 5 times faster than the fundamental frequency of the non-sinusoidal transmitter signal frequency. This may introduce a phase offset, which is mitigated by the use of IQ complex demodulation. The use of a slow ADC reduces power consumption and cost, while the additional Q demodulator is digitally implemented and therefore associated with negligible additional cost and power. Thus, the above-described configuration using digital I / Q demodulation and analog-to-digital conversion before demodulation is cost-effective and energy efficient. Although digital I / Q demodulation has been described, analog I / Q demodulation followed by analog-to-digital conversion may be performed without departing from this disclosure.

[0089] In one embodiment, only an I demodulator is used (without a Q demodulator) to perform demodulation. To obtain a satisfactorily accurate phase alignment using only an I demodulator, a faster ADC (744) may be used to reduce possible phase offsets. For example, the ADC may operate at least 16 times the speed of the fundamental frequency of the non-sinusoidal transmitter signal frequency.

[0090] As mentioned above, one or more embodiments use a non-sinusoidal transmitter signal (722). In the example of FIG. 7, a single non-sinusoidal transmitter signal having a trapezoidal waveform may be used. Any other non-sinusoidal waveform, such as a square wave, may be used without departing from this disclosure. Compared to sinusoidal waveforms, non-sinusoidal waveforms may have various advantages. For example, it may be relatively easy to synthesize a non-sinusoidal waveform using basic circuit elements. Furthermore, it may be relatively easy to generate a non-sinusoidal waveform with an amplitude higher than the system voltage. For example, an amplitude of 9V may be achieved using a system voltage of 3V. A non-sinusoidal waveform may also have more signal energy at the fundamental frequency than a sinusoidal waveform with the same nominal amplitude. In FIG. 7, a trapezoidal waveform used as the non-sinusoidal transmitter signal (722) is illustrated in the time domain (left) and frequency domain (right). The trapezoidal waveform has a fundamental frequency of 100 kHz and an amplitude of 1V. As the frequency spectrum shows, the amplitude at the fundamental frequency is 1.254V (1.97dB). Thus, for the same voltage of the non-sinusoidal transmitter signal at the fundamental frequency, the trapezoidal waveform has higher signal energy compared to the sinusoidal waveform, which provides various potential advantages, such as allowing a lower transmitter signal voltage to be used, resulting in a higher signal-to-noise ratio when using the same voltage. However, as shown in FIG. 7, a non-sinusoidal waveform such as a trapezoidal waveform also contains harmonics different from the fundamental frequency. In the case of the trapezoidal wave shown in FIG. 7, there are harmonics at the third (700kHz), fifth (100kHz), etc. In the frequency spectrum shown in FIG. 7, the amplitude of the fundamental frequency at the third harmonic is 10.6dB lower than the fundamental frequency, the amplitude of the fundamental frequency at the fifth harmonic is 17.4dB lower than the fundamental frequency, etc. The total harmonic distortion for the first 10 harmonics is -9.6dB.

[0091] The presence of harmonics causes aliasing in the ADC (744) in one or more embodiments. The effect of aliasing can be detrimental to the accuracy of the sensed signal (764). This effect is explained below based on the following scenario: Assume that the three fundamental frequencies of the non-sinusoidal transmitter signal (722) are 100 kHz, 109.9 kHz, and 119.8 kHz. For a burst length of 200 μs, the fundamental frequencies are spaced 9.9 kHz apart, which makes them orthogonal (or nearly orthogonal) when performing demodulation using a Hanning window (discussed below). Other frequency spacings can be used for other types of windows, other burst lengths, etc. Furthermore, the ADC sampling frequency F of the ADC (744) is ... S Let's say that F is set to 500kHz. S At Hz = 500 kHz, the Nyquist frequency is 250 kHz. Thus, aliasing occurs for all three harmonics of the non-sinusoidal transmitter signal (722). As a result of aliasing, in one or more embodiments, the harmonics appear as aliasing distortion at lower frequencies in the output of the ADC (744).

[0092] The low frequency where the aliasing distortion appears can be identified by a combination of shifting and folding operations. Aliasing can result in an erroneous detection signal when harmonics appear as aliasing distortion at or near one of the fundamental frequencies of the non-sinusoidal transmitter signals. In the above example, the 5th harmonic of the 119.8 kHz non-sinusoidal transmitter signal is 5 x 119.8 kHz = 599 kHz. When aliasing analysis is performed using shifting and folding operations, the 5th harmonic appears as aliasing distortion at 99 kHz when using an ADC sampling frequency of 500 kHz. Since 99 kHz is close to the 100 kHz fundamental frequency of one of the non-sinusoidal transmitter signals, the detection signal obtained for demodulation performed at 100 kHz is not accurate.

[0093] In one or more embodiments, the ADC sampling frequency F Sis chosen to reduce errors caused by harmonics that appear as aliasing distortion near the fundamental frequency. More specifically, F S is adjusted so that there is no aliasing distortion near any fundamental frequency. S systematically reduces F while monitoring for inter-band interference (i.e., the presence of aliasing distortion near the fundamental frequency). S The desired F S is the F where interband interference is minimal. S Inter-band interference is explained below with reference to the example illustrated in FIG.

[0094] Although Figure 7 illustrates a particular processing configuration, other configurations may be used without departing from this disclosure. For example, although Figure 7 illustrates the simultaneous driving of three Tx electrodes with non-sinusoidal transmitter signals having three unique fundamental frequencies, any number of Tx electrodes may be simultaneously driven with any number of non-sinusoidal transmitter signals. Additionally, although Figure 7 illustrates a processing configuration for processing a single resultant signal obtained from three Rx electrodes, multiple analog and digital processing components as illustrated may be used to process additional resultant signals.

[0095] FIG. 8 illustrates an example of an analysis of inter-band interference in accordance with one or more embodiments. In this example, F S However, F S The frequency range analyzed is limited (in this example to ±10%) to reduce the possibility of interference caused by external noise (noise coming from sources different from the input device). External noise can come from various components, e.g. the power supply, the display device. External noise can be concentrated at certain frequencies, and the first F S (500kHz) is sometimes chosen to have low potential for interference from external noise. SVarying r reduces the likelihood that external noise will select a frequency that will cause significant interference.

[0096] As FIG. 8 illustrates in band interference plot (802), F S is adjusted in the frequency range from 450kHz to 550kHz to identify the inter-band interference, which is a measure of the interference caused by driving one or more Tx electrodes at a first frequency while digitally demodulating (after A / D conversion and possible aliasing) at a second frequency. Referring to the example introduced earlier, using 100kHz, 109.9kHz and 119.8kHz for non-sinusoidal transmitter signals, aliasing can result in the following inter-band interference: (i) Drive at 100kHz and demodulate at 109.9kHz (ii) Drive at 100kHz and demodulate at 119.8kHz (iii) Drive at 109.9kHz and demodulate at 100kHz (iv) Drive at 109.9kHz and demodulate at 119.8kHz (v) Drive at 119.8kHz and demodulate at 100kHz (vi) Drive at 119.8kHz and demodulate at 109.9kHz

[0097] The inter-band interference for each of these six cases may be obtained across the frequency range. Thus, a plot 802 may be obtained for each of the six cases. Each plot may include frequencies where the inter-band interference is unacceptably high, and may also include frequencies where the inter-band interference is acceptably low or very low. As plot 802 shows, given the particular scenario, the inter-band interference is at a low F S On the other hand, high F S For , the inter-band interference is reduced to a very low level.

[0098] The outline of inter-band interference (804) is the worst frequency (F S=449kHz) and the best frequency (F S = 520 kHz). The worst case interference is found to be 21.491% when a non-sinusoidal transmitter signal is radiated at F2 (109.9 kHz) while demodulation is performed at F3 (119.8 kHz). This inter-band interference is clearly visible in plot (802) (left-most peak). In contrast, for the best frequencies, all interference remains below 0.02%. In plot (802) (expanded frequency range), an almost complete absence of interference is seen.

[0099] The optimization is performed to find the frequency F where interference is tolerable for all six cases. S The selection can be made as follows. S A method for determining σ is discussed below. The example of Figure 8 is for three non-sinusoidal transmitter signals, however, a similar analysis can be performed for any number of non-sinusoidal transmitter signals.

[0100] 9 and 10 illustrate flow charts according to one or more embodiments. One or more of the steps in FIG. 9 and 10 may be performed by the components discussed above with reference to FIG. 1, FIG. 6A, FIG. 6B, and FIG. 7. Although the various steps of these flow charts are presented and described in sequence, one skilled in the art will understand that at least some of the steps may be performed in a different order, may be combined or omitted, and some of the steps may be performed in parallel. Additional steps may also be performed. Thus, the scope of the disclosure should not be considered limited to the specific arrangement of the steps illustrated in FIG. 9 and 10.

[0101] The flowchart of FIG. 9 illustrates a method (700) for inter-band harmonic interference mitigation for multi-frequency domain parallel scanning according to one or more embodiments.

[0102] In step 902, a noise measurement is made. The noise may be measured under real operating conditions, e.g., in the presence of possible noise sources such as displays, power supplies, etc. This noise measurement may be used to distinguish noisy frequency regions from quiet or noise-free frequency regions. Spectral analysis may be performed to make this distinction.

[0103] In step 904, the non-sinusoidal transmitter signal is selected such that interference due to the noise identified in step 902 is avoided or at least reduced. In other words, a frequency region in which relatively little noise is present may be selected for the non-sinusoidal transmitter signal. For example, assume that based on the execution of step 902, noise is detected at 50 kHz. To avoid the detected noise, the fundamental frequency of the non-sinusoidal transmitter signal may be placed in a region around 100 kHz. The frequency spacing of the fundamental frequency, the burst length, the shape of the non-sinusoidal transmitter signal, etc. may be selected such that specific orthogonality and timing requirements are met, as discussed above. Step 904 may be performed for any number of non-sinusoidal transmitter signals radiated simultaneously. Although the flowchart illustrates the measurement of noise and the selection of the non-sinusoidal transmitter signal as separate steps, these steps may be combined. For example, measurements may be performed on a selected set of non-sinusoidal transmitter signals. If too much noise is found to be present based on the measurements, a different set of non-sinusoidal transmitter signals may be selected. Switching to different sets of non-sinusoidal transmitter signals may continue until a set is identified in which the noise is deemed acceptable.

[0104] In step 906, the sampling frequency F of the analog-to-digital converter (ADC) is S In one or more embodiments, F Sis selected such that aliasing distortion associated with harmonics of the non-sinusoidal transmitter signal is located at a frequency different from the fundamental frequency of the non-sinusoidal transmitter signal. S is adjusted to reduce the amplitude of the aliasing distortion at the fundamental frequency to reduce or eliminate inter-band harmonic interference. Additional details are described with reference to FIG. S The selection of may start from a default sampling frequency. The optimization may be performed within a limited range around the default sampling frequency. The optimization may be performed to minimize aliasing distortion at the fundamental frequency of the non-sinusoidal transmitter signal. Any criterion may be used to specify an acceptable level of aliasing at the fundamental frequency. For example, 1 / 1000 of inter-band harmonic interference may be set as the threshold. Step 906 may be performed for a single set of non-sinusoidal transmitter signals or for multiple sets of non-sinusoidal transmitter signals in different frequency ranges. Using multiple sets of non-sinusoidal transmitter signals may allow the input device to operate in different frequency ranges depending on, for example, the noise environment. The operation of step 906 may be performed by measuring inter-band harmonic interference on an actual input device or by simulation. If simulation is used, various components of the input device may be approximated by a simulation model. For example, the characteristics of the sensing element and analog front-end may be approximated by a first approximation (single-pole) simulation model having time constants that approximate the characteristics of the actual sensing element and the actual analog front-end, respectively.

[0105] The operations of steps 902-906 involve the selection of one or more sets of frequencies of the non-sinusoidal transmitter signal and a matching sampling frequency F. S Alternatively, steps 902-906 may be performed during operation of the input device.

[0106] Touch sensing may be performed in step 908, as described below with reference to FIG.

[0107] The flowchart of FIG. 10 illustrates a method (1000) for multi-frequency domain touch sensing in accordance with one or more embodiments.

[0108] In step 1002, a set of Tx electrodes are simultaneously driven with multiple non-sinusoidal transmitter signals having unique fundamental frequencies. Any number of Tx electrodes may be simultaneously driven. Additional details are described with reference to Figures 6A, 6B, and 7.

[0109] In step 1004, a result signal is obtained at the Rx electrode. Step 1004 may be performed in parallel with step 1002. Furthermore, step 1004 may be performed simultaneously for multiple Rx electrodes. The result signal received at the Rx electrode is affected by multiple non-sinusoidal transmitter signals coupled to the Rx electrode. Coupling occurs where the Rx electrode is spatially close to the Tx electrode (e.g., at the sensing element where the Tx electrode crosses the Rx electrode). Since capacitive coupling is affected by the presence or absence of an input object, the result signal is also affected by the presence or absence of an input object in the vicinity of the sensing element.

[0110] In step 1006, the sampling frequency F determined in step 906 is S The resulting signal is analog-to-digital converted using an analog-to-digital converter operating at .

[0111] In step 1008, the resulting analog-to-digital converted signal is demodulated to generate a set of sensed signals. One sensed signal may be obtained for each of one or more Tx electrodes driven with a non-sinusoidal transmitter signal having a distinct frequency. If both I and Q demodulations are performed, the I and Q components of the obtained sensed signal may be processed to identify the amplitude and / or phase of the sensed signal. Additional details are described with reference to Figures 6A, 6B, and 7. A solution for the sensed signal specific to an individual sensed element may be obtained by evaluating the sensed signal over multiple bursts of the non-sinusoidal transmitter signal. For example, using 20 bursts for a configuration including 20 sensed elements may provide a unique solution. If step 1004 is performed for multiple Rx electrodes, step 1008 may also be performed multiple times to demodulate each of the resulting signals corresponding to the multiple Rx electrodes.

[0112] The above steps may be repeated. For example, steps 602-606 may be repeated while driving a different set of Tx electrodes selected from the Tx electrodes in the frequency domain, as described above with reference to Figures 6A, 6B and 7. A capacitance image with sensed signals corresponding to a complete set of sensing elements in the capacitance image may be available after performing steps 602-608 for all Tx electrodes in the sensing region.

[0113] In step 1010, touch detection may be performed using the detection signals. Touch detection may involve evaluating the detection signals against a previously determined baseline value. If the detection signals deviate from the baseline value by at least a certain amount, an input object may be considered to be present in the vicinity of the detection element corresponding to the detection signal. Step 1010 may be performed for some or all of the detection signals corresponding to the detection elements of the capacitive image.

[0114] To perform touch detection over time, steps 1002-1008 may be repeated, for example, periodically.

[0115] The embodiments of the present disclosure have various advantages. The use of simultaneously emitted transmitter signals at different frequencies allows driving of a large number of Tx electrodes at high frame rates (which may be necessary for large touch screens) without shortening the burst of emitted transmitter signals. The embodiments of the present disclosure use non-sinusoidal waveforms. Non-sinusoidal waveforms have the advantage that they are relatively easy to generate, even if they have a higher amplitude than the system voltage. Furthermore, non-sinusoidal waveforms have a higher voltage amplitude at the fundamental frequency than sinusoidal waveforms. The resulting higher signal energy at the fundamental frequency provides various advantages, such as allowing the use of lower transmitter signal voltages, resulting in a higher signal-to-noise ratio when using the same voltage.

[0116] While the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having the benefit of this disclosure, will appreciate that other embodiments may be devised without departing from the scope of the invention as disclosed herein. Accordingly, the scope of the present invention should be limited only by the scope of the appended claims.

Claims

1. 1. An input device comprising: transmitter electrodes disposed in a plurality of distinct frequency regions within a sensing region of the input device, each of the plurality of distinct frequency regions comprising a plurality of the transmitter electrodes; a receiver electrode within the sensing region; a processing system comprising a plurality of demodulators; Equipped with the processing system comprising: simultaneously driving at least two of the plurality of transmitter electrodes in each of the plurality of distinct frequency ranges with a plurality of transmitter signals having unique frequencies; receiving a result signal at the receiver electrode; configured to demodulate the resultant signals using the plurality of demodulators to generate a plurality of sensed signals; each of the plurality of demodulators operates at a different frequency from the unique frequency; Each of the plurality of distinct frequency ranges is unique to one of the unique frequencies. Input devices.

2. Simultaneously driving at least two of the plurality of transmitter electrodes in each of the plurality of distinct frequency ranges with the plurality of transmitter signals having unique frequencies includes simultaneously driving at least two of the plurality of transmitter electrodes in each of the plurality of distinct frequency ranges at frequencies unique to the frequency range among the unique frequencies. The input device of claim 1 .

3. simultaneously driving at least two of the plurality of transmitter electrodes in each of the plurality of distinct frequency ranges with the plurality of transmitter signals having unique frequencies; simultaneously driving at least two of the plurality of transmitter electrodes in a first frequency range of the plurality of separate frequency ranges at a first one of the unique frequencies; simultaneously driving at least two of the plurality of transmitter electrodes in a second frequency range of the plurality of distinct frequency ranges at a second one of the unique frequencies. The input device of claim 1 .

4. The plurality of transmitter signals are orthogonal to one another. The input device of claim 1 .

5. 1. A processing system for an input device, comprising: the processing system comprises a plurality of demodulators; and simultaneously driving at least two of a plurality of transmitter electrodes in a plurality of separate frequency regions within a sensing region of the input device using a plurality of transmitter signals having unique frequencies, each frequency region comprising a plurality of transmitter electrodes; receiving a result signal at a receiver electrode within the sensing region; configured to demodulate the resultant signals using the plurality of demodulators to generate a plurality of sensed signals. each of the plurality of demodulators operates at a different frequency from the unique frequency; Each of the plurality of distinct frequency ranges is unique to one of the unique frequencies. Processing system.

6. Simultaneously driving at least two of each of the plurality of transmitter electrodes in each of the separate frequency ranges with the plurality of transmitter signals having unique frequencies includes simultaneously driving at least two of each of the plurality of transmitter electrodes in each of the plurality of separate frequency ranges at frequencies unique to the frequency range among the unique frequencies. The processing system of claim 5 .

7. simultaneously driving at least two of each of the plurality of transmitter electrodes in each of the distinct frequency ranges with the plurality of transmitter signals having unique frequencies; simultaneously driving at least two of the plurality of transmitter electrodes in a first frequency range of the plurality of separate frequency ranges at a first one of the unique frequencies, while simultaneously driving at least two of the plurality of transmitter electrodes in a second frequency range of the plurality of separate frequency ranges at a second one of the unique frequencies. The processing system of claim 5 .

8. The plurality of transmitter signals are orthogonal to one another. The processing system of claim 5 .

9. 1. A method for operating an input device, said method comprising: simultaneously driving at least two respective ones of a plurality of transmitter electrodes in a plurality of separate frequency regions within a sensing region of the input device with a plurality of transmitter signals having unique frequencies, each frequency region comprising a plurality of transmitter electrodes; receiving a result signal at a receiver electrode disposed in the sensing area of ​​the input device; demodulating the resulting signal with a plurality of demodulators to generate a plurality of sensed signals; performing touch sensing using the result signal; Including, each of the plurality of demodulators operates at a different frequency from the unique frequency; Each of the plurality of distinct frequency ranges is unique to one of the unique frequencies. method.

10. 1. A method for operating an input device, said method comprising: obtaining a plurality of non-sinusoidal transmitter signals having unique fundamental frequencies; selecting a sampling frequency of an analog-to-digital converter (ADC) such that a plurality of aliasing distortions associated with harmonics of the non-sinusoidal transmitter signal are located at frequencies different from the fundamental frequency; Contains method.

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