Techniques for wideband touch sensing and related systems, methods, and devices

Abstract

Touch sensing methods, and related methods and systems, are described. In some embodiments of the touch sensing methods, the energy of a drive signal is allocated among frequencies of RF subcarriers such that the allocated energy meets electromagnetic emissions requirements for the application of a touch sensing system implementing the touch sensing method. Methods for determining a spectrally shaped time-domain digital waveform for use in generating a spectrally shaped drive signal are also described.

Description

[Technical Field]

[0001] (Priority Claim) This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 62 / 882,393, filed August 2, 2019, for "An OFDM-BASED APPROACH To Wideband Touch Sensing," the entire contents and disclosure of which are incorporated herein by this reference.

[0002] (Technical field) The disclosed embodiments relate generally to touch sensing and controllers for capacitive touch sensing. [Background technology]

[0003] A typical touch interface system may incorporate touch sensors (e.g., without limitation, capacitive and / or resistive sensors) that respond to objects in proximity to or in physical contact with the touch-sensitive surface of the touch interface system. Such responses may be captured and interpreted to infer information about the touch, including the location of the object relative to the touch interface system.

[0004] Touchpads used with personal computers, including keyboards on laptop computers and tablets, often incorporate or work in conjunction with touch interface systems. Displays often include touchscreens that incorporate elements of touch interface systems (typically at least touch sensors) to allow users to interact with a graphical user interface (GUI) and / or computer applications. Examples of devices that incorporate touch displays include portable media players, televisions, smartphones, tablet computers, personal computers, and wearable devices such as smartwatches, to name a few. Additionally, automobiles, appliance (e.g., ovens, refrigerators, or washing machines), security systems, automated teller machines (ATMs), home climate control systems, and industrial equipment control panels can couple touch interface systems to their displays and housings, such as to enable buttons, sliders, wheels, and other touch elements.

[0005] Objects and advantages of various embodiments of the present disclosure will become apparent to those skilled in the art from the detailed description taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a process for generating a spectrally shaped drive signal in accordance with one or more embodiments of the present disclosure. [Figure 2] 1 is a process for selecting waveforms for modulating signals and selecting component frequencies that may be used to generate a spectrally shaped drive signal according to disclosed embodiments. [Figure 3] FIG. 1 is a functional block diagram illustrating a process for generating an encoded digital signal representing a spectrally shaped time-domain waveform in accordance with one or more embodiments. [Figure 4]FIG. 1 is a block diagram of a touch sensing system configured to use a drive signal including a spectrally shaped drive signal in accordance with one or more disclosed embodiments. [Figure 5] FIG. 4 is a functional block diagram of an embodiment of the transmit path of FIG. 3. [Figure 6] FIG. 2 is a functional block diagram of an embodiment of a receive path for receiving a spectrally shaped continuous-time analog signal. [Figure 7] 1 is a block diagram of circuitry that, in some embodiments, may be used to implement various functions, operations, acts, algorithms, methods and / or processes described herein. DETAILED DESCRIPTION OF THE INVENTION

[0007] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and which show, by way of illustration, specific exemplary embodiments in which the present disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present disclosure. However, other embodiments may be utilized, and changes in structure, materials, and processes may be made without departing from the scope of the present disclosure.

[0008] The figures presented herein are not intended to be actual illustrations of any particular method, system, device, or structure, but merely idealized representations used to describe embodiments of the present disclosure. The figures presented herein are not necessarily drawn to scale. Similar structures or components in various figures may retain the same or similar numbering for the convenience of the reader. However, similarity in numbering does not necessarily mean that the structures or components are identical in size, composition, configuration, or any other characteristic.

[0009] It will be readily understood that the components of the embodiments, as generally described and illustrated in the figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following description of various embodiments is not intended to limit the scope of the present disclosure, but merely represents representative examples of various embodiments. While various aspects of the embodiments may be presented in drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

[0010] The following description may include examples to assist those skilled in the art in practicing the disclosed embodiments. The use of the terms "exemplary," "example," and "for example" means that the associated description is explanatory, and the scope of the present disclosure is intended to encompass examples and legal equivalents. The use of such terms is not intended to limit the embodiments or the scope of the present disclosure to specific components, steps, features, functions, etc.

[0011] Furthermore, the specific implementations shown and described are merely examples and should not be construed as the only way to implement the present disclosure, unless otherwise specified herein. Elements, circuits, and functions may be shown in block diagram form so as not to obscure the present disclosure in unnecessary detail. Conversely, the specific implementations shown and described are merely exemplary and should not be construed as the only way to implement the present disclosure, unless otherwise specified herein. Furthermore, the block definitions and partitioning of logic among various blocks are exemplary specific implementations. It will be readily apparent to one skilled in the art that the present disclosure can be implemented with numerous other partitioning solutions. For the most part, details regarding timing considerations and the like have been omitted; such details are not necessary to obtain a complete understanding of the present disclosure and are within the capabilities of those skilled in the art.

[0012] The information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, and symbols that may be referenced throughout this specification may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof. Some figures may illustrate signals as a single signal for clarity of presentation and explanation. Those skilled in the art will understand that a signal may represent a bus of signals, which may have various bit widths, and that the present disclosure may be implemented with any number of data signals, including a single data signal.

[0013] Any reference to elements herein using designations such as "first," "second," etc. should be understood not to limit the quantity or order of those elements unless such limitation is expressly stated. Rather, these designations are used herein as a convenient method of distinguishing between two or more elements or instances of an element. Thus, reference to a first element and a second element does not imply that only two elements may be used or that the first element must precede the second element in any way. Also, unless otherwise specified, a set of elements may include one or more elements. Similarly, sometimes an element referred to in the singular may also include one or more instances of the element.

[0014] As used herein, the term "substantially" when referring to a given parameter, characteristic, or condition means and includes the extent to which one of ordinary skill in the art would understand that the given parameter, characteristic, or condition is met with small variations, such as, for example, within acceptable manufacturing tolerances. As an example, depending on the particular parameter, characteristic, or condition that is substantially met, the parameter, characteristic, or condition may be at least 90% met, at least 95% met, or even at least 99% met.

[0015] The various illustrative logic blocks, modules, and circuits described in connection with the embodiments disclosed herein may be implemented or performed using a general-purpose processor, a special-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor (which may also be referred to herein as a host processor or simply a host) may be a microprocessor, although alternatively, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, such as a DSP with a microprocessor, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. A general-purpose computer including a processor is considered a special-purpose computer, and a general-purpose computer is configured to execute computing instructions (e.g., software code) related to the embodiments of the present disclosure.

[0016] Also, it should be noted that the embodiments may be described in terms of a process that is depicted as a flowchart, a flow diagram, a structure diagram, or a block diagram. While a flowchart may describe operational acts as a sequential process, many of these acts may be performed in another sequence, in parallel, or substantially simultaneously. Additionally, the order of acts may be rearranged. A process may correspond to, but is not limited to, a method, a thread, a function, a procedure, a subroutine, and / or a subprogram. Furthermore, the methods disclosed herein may be implemented in hardware, software, or both. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media, such as any medium that facilitates transfer of a computer program from one place to another.

[0017] As understood for purposes of the embodiments described in this disclosure, a capacitive sensor may respond to contact of an object (such as, but not limited to, a finger or stylus) with or proximity of an object to a touch-sensitive area of ​​the capacitive sensor. In this disclosure, "contact" and "touch" are meant to encompass both physical contact of an object with a touch-sensitive area (such as, but not limited to, an electrode or one or more overlays covering an electrode or group of electrodes) and the presence of an object in proximity to a touch-sensitive area without physical contact. Actual physical contact with a capacitive sensor is not necessarily required.

[0018] As an example, when an object touches a capacitive sensor, a change in capacitance may occur within the capacitive sensor at or near the touch location. An analog acquisition front end may detect the touch if a certain threshold is met. "Charge-then-transfer" is a non-limiting example of a technique implemented in some touch acquisition front ends to detect capacitance changes, whereby a sensing capacitor is charged (e.g., charged faster or slower) in response to a change in capacitance, and the charge is transferred to an integrating capacitor over multiple transfer cycles. The amount of charge associated with such charge transfer may be converted to a digital signal by an analog-to-digital converter (ADC), and a digital controller may process those digital signals (typically referred to as "delta counts" or simply "delta") to determine measurements and / or detect whether an object has touched the sensor.

[0019] Self-capacitance sensors (also referred to herein as "self-capped sensors") are capacitive electric field sensors that respond to changes in capacitance relative to ground. They are typically laid out in arrays of rows and columns that respond independently to touch. By way of non-limiting example, a self-capped sensor may include circuitry that employs repeated charge-and-transfer cycles using a common integrated CMOS (i.e., complementary metal-oxide semiconductor) push-pull driver circuit with floating terminals.

[0020] A mutual capacitance sensor is a capacitive electric field sensor that detects / responds to changes in capacitance between two electrodes (a drive electrode and a sense electrode). A pair of drive and sense electrodes forms a capacitor at each intersection of the drive and sense lines. Self-capacitance and mutual capacitance techniques can be used in the same touch interface system and can be complementary to each other. For example, self-capacitance can be used to confirm a touch detected using mutual capacitance.

[0021] As an example, touch sensors may be overlaid in a two-dimensional (2-D) arrangement for, for example, a touchpad or a display screen's 2-D touch-sensitive surface to facilitate user interaction with an associated appliance or device. An insulating protective layer (e.g., without limitation, resin, glass, and / or plastic) may be used to cover the touch sensors and may be referred to herein as an "overlay." A "touch display," as a non-limiting example, is a display (such as a liquid crystal display (LCD), thin film transistor (TFT) LCD, or light-emitting diode (LED) display) that incorporates 2-D touch sensors mounted in a transparent medium above the display, sometimes with an additional transparent medium such as glass in front of the touch sensors.

[0022] Using a touch sensor embodiment using a matrix sensor approach of mutual capacitance sensors employing charge transfer techniques, drive electrodes may extend in rows on one side of a substrate, and sense electrodes may extend in columns on the other side of the substrate, defining a "matrix" array of N x M nodes. Each node corresponds to the intersection of a conductive line of a drive electrode and a conductive line of a sense electrode. The drive electrodes simultaneously drive all of the nodes in a given row, and the sense electrodes sense all of the nodes in a given column. The capacitive coupling between the drive and sense electrodes (mutual capacitance) or the coupling between the sense electrodes and ground (self-capacitance) may be measured separately at the node location in response to a capacitance change indicative of a touch event, or both may be measured. For example, if a drive signal is applied to the drive electrode in row 2 and the sense electrode in column 3 is active, the node location is row 2, column 3. The node may be scanned by sequencing through different combinations of drive and sense electrodes. In one mode, the drive electrodes may be driven sequentially while the sense electrodes are all continuously monitored, while in another mode, each sense electrode may be sampled sequentially.

[0023] Using an embodiment of a touch sensor that uses a matrix sensor approach of self-capacitance sensors, electrodes may extend in rows and columns to define a "matrix" array of N x M nodes. The matrix sensor may be constructed with an electrode for each node, and each electrode may be individually addressable, or each row and column may be an addressable electrode, with each node corresponding to a unique row / column pair. A drive signal (i.e., an alternating current (A / C) stimulus) is repeatedly provided to the sensor's electrodes. When an object touches the sensor, coupling between the object and the electrodes changes the current drawn by the electrodes (i.e., increasing or decreasing, as a non-limiting example, depending on whether the object is electrically grounded or electrically floating), which increases the apparent sensor capacitance, and this increase in sensor capacitance can be detected. For example, if an increase in capacitance is detected while a drive signal is applied to electrode row 2 and electrode column 3, the location of the touch may be row 2, column 3. Interpolation techniques can be used to identify locations between nodes. The nodes may be scanned sequentially by sequencing through combinations of electrode rows and columns.

[0024] The drive signal (i.e., A / C stimulus) mentioned above is one source of electromagnetic emissions (EME). The capacitance is typically measured synchronously with the drive signal. Therefore, there is a direct relationship between the sampling rate of the measurement and the frequency of the EME emissions.

[0025] By way of non-limiting example, a microcontroller, digital logic circuit, and configurable state machine may be configured to perform the functions of the acquisition circuit and touch controller described herein, including, but not limited to, controlling drive electrodes, monitoring sense electrodes, analyzing capacitive effects on the touch sensor (e.g., but not limited to, detected from measured changes in channel capacitance and / or absolute channel capacitance), and more generally processing and reporting touches. An integrated circuit (IC) package including the microcontroller may provide input and output pins for communicating with a host, as well as firmware to perform techniques and operations, including those described herein, in connection with various embodiments.

[0026] Some embodiments generally relate to systems and methods for providing a drive signal to a touch sensor. In particular, a drive signal may be generated whereby the total energy of a touch-sensitive stimulus (i.e., an A / C signal) is allocated across multiple frequencies. In one embodiment, spectral shaping may be performed to generate a drive signal characterized by the total energy allocated across multiple specified frequencies.

[0027] Some embodiments generally relate to systems and methods for performing spectral shaping of a drive signal in response to, by way of non-limiting example, application-specific requirements. By way of non-limiting example, the target application-specific requirements may be noise immunity requirements and / or limits on electromagnetic emissions. As used herein, "spectral characteristics" means one or more of noise, electromagnetic emissions, or energy. "Acceptable spectral characteristics" are spectral characteristics that are within specified limits or requirements.

[0028] In one embodiment, radio frequency (RF) signals are generated, each corresponding to a different designated frequency (i.e., component frequencies). Each of the RF signals is generated in response to an encoded digital signal having a designated amplitude. In one embodiment, the component frequencies may be preselected based at least in part on the component frequencies and / or application-specific requirements for the given component frequency. As a non-limiting example, one or more of the component frequencies of the RF signal may be selected because they are associated with the largest EME limitations compared to other available frequencies. Alternatively or additionally, one or more of the component frequencies of the RF signal may be selected because they have the lowest noise immunity requirements (i.e., the least restrictive noise immunity requirements) of the available frequencies. In one embodiment, the RF signals may be generated using a digital modulation scheme. Non-limiting examples of digital modulation schemes include quadrature amplitude modulation (QAM) or phase shift keying.

[0029] 1 illustrates a touch sensing process 100 using a spectrally shaped drive signal for a touch sensor, such as spectral shaping, configured to allocate energy in the drive signal among multiple frequencies, in accordance with one or more embodiments. As discussed herein, the energy allocated to a particular frequency may be selected such that the resulting EME is within the acceptable EME for a given frequency. In particular, for a given touch sensing operation, the amount of energy allocated to a particular frequency may be the same or different. As a non-limiting example, the amount of allocated energy may differ because different frequencies may have different acceptable EMEs.

[0030] It will be understood that process 100 includes at least two constituent processes: a first process including operations 102, 104, and 106 for generating a spectrally shaped time-domain digital waveform, and a second process including operations 108, 110, 112, 114, 116, and 118 for performing touch sensing operations to detect a touch on a touch sensor. Both of the two constituent processes need not be performed, and the first process may be performed without the second process, or partially without the second process, and the second process may be performed without the first process, without departing from the scope of this disclosure. For example, operations 102, 104, 106, and 118 may be performed without requiring operations 108, 110, 112, 114, and 116.

[0031] In operation 102, process 100 receives an indication of an acceptable EME. In various embodiments, the acceptable EME may include an acceptable EME for a number of designated frequencies. By way of non-limiting example, the designated frequencies may include one or more of individual frequencies and / or frequency bands.

[0032] In operation 104, process 100 selects a set of RF subcarriers based on the metric of acceptable EME. Each such RF subcarrier has a specified frequency and a specified amplitude. Selecting the RF subcarriers may involve selecting the frequencies and amplitudes of the RF subcarriers. In some embodiments, a phase relationship between the selected frequencies may also be selected (i.e., a specified phase relationship may be selected). The specified phase relationship is a degree of phase orthogonality of the respective subcarriers such that at least a portion of the energy of each RF subcarrier is out of phase with the other RF subcarriers (e.g., perfectly orthogonal RF subcarriers have a 90-degree phase shift).

[0033] In operation 106, process 100 generates a spectrally shaped time-domain digital waveform. In some embodiments, process 100 generates the spectrally shaped time-domain digital waveform by performing static amplitude quadrature amplitude modulation using a selected set of RF subcarriers. In some embodiments, generating the spectrally shaped time-domain digital waveform includes performing an inverse fast Fourier transform (IFFT) on the sum of the set of RF subcarriers. In particular, the spectrally shaped time-domain digital waveform may include an in-phase waveform (also referred to as the I component of the waveform) and a quadrature-phase waveform (also referred to as the Q component of the waveform). Preferably, operation 106 is performed digitally.

[0034] At operation 108, process 100 generates a spectrally shaped continuous time-domain analog signal in response to the spectrally shaped time-domain digital waveform. In some embodiments, a "continuous" analog signal may be generated by repeatedly applying the spectrally shaped time-domain digital waveform. In some embodiments, the spectrally shaped time-domain digital waveform is represented as a stream of bits (i.e., a bitstream) that, when applied to a digital-to-analog converter (DAC), causes the DAC to generate an analog signal, i.e., a spectrally shaped continuous time-domain analog signal corresponding to the spectrally shaped time-domain digital waveform.

[0035] In operation 110, the process 100 generates a drive signal in response to the spectrally shaped continuous time domain analog signal. The process 100 generates the drive signal by mixing in-phase and quadrature components of the spectrally shaped continuous time domain analog signal. In particular, the drive signal is characterized by the energy of the drive signal allocated across specified frequencies of the subcarriers.

[0036] In operation 112, process 100 provides the drive signal generated in operation 110 (i.e., the drive signal characterized by the energy of the drive signal allocated across the specified frequencies of the subcarrier) to the touch sensor, and more specifically, to the transmitter line of the touch sensor.

[0037] In operation 114, process 100 observes the energy of the sensed signal of the touch sensor. In some embodiments, the sensed signal may be received via a receiver line of the touch sensor while providing the drive signal generated in operation 110 to the touch sensor. In particular, a sensed signal received in response to a drive signal characterized by its energy allocated among certain frequencies may also be characterized by the energy allocated among the frequencies of the subcarriers. In one or more embodiments, observing the energy of the sensed signal of the touch sensor may include one or more of IQ demodulation, demultiplexing, inverse fast Fourier transform (IFFT) and / or fast Fourier transform (FFT) decoding, and amplitude reconstruction, as shown in FIG.

[0038] At operation 116, process 100 observes the channel capacitance of the touch sensor in response to the observed energy of the sensed signal. In one or more embodiments, observing the channel capacitance of the touch sensor in response to the observed energy level of the sensed signal may include performing a weighted sum of the amplitude values ​​to arrive at a sensor capacitance estimate, as shown in FIG.

[0039] At operation 118, process 100 detects a touch at the touch sensor in response to observing that the energy of the sensed signal differs from the energy of the drive signal. As a non-limiting example of a contemplated touch sensing system, the difference may be due to attenuation of the drive signal due to an increase in channel capacitance caused by an object contacting the touch sensor.

[0040] As discussed herein, allowable subcarriers at specified frequencies and amplitudes are selected (e.g., operation 104 in FIG. 1 ) so that a spectrally shaped time-domain digital waveform can be generated (e.g., operation 106 in FIG. 1 ).

[0041] Some embodiments relate generally to systems and methods for selecting RF subcarriers for a spectrally shaped time-domain digital waveform, and more particularly to selecting the amplitude, phase, and frequency of each of the RF subcarriers. In one embodiment, requirements (i.e., describing acceptable EME) are received for one or more target applications of, by way of non-limiting example, a touch sensor or a touch sensing system including a touch sensor and a touch controller configured to generate a spectrally shaped drive signal for the touch sensor via process 100. As noted above, such requirements may be, by way of non-limiting example, EME limits or noise immunity requirements. A test frequency, a test amplitude, and a test phase are selected. In one embodiment, a given test frequency is selected such that it is orthogonal to other test frequencies.

[0042] An RF subcarrier is orthogonal to another RF subcarrier if the cross-correlation of the subcarrier codes is essentially zero, i.e., the two RF subcarriers do not (or will not) interfere with each other, including the absence of constructive and destructive interference. As a non-limiting example, a property of orthogonal signals, and RF subcarriers, is more specifically that the dot product of the two signals is zero. Perfect orthogonality may be desirable but not practical or necessary, so in some cases, a designer may select an appropriate orthogonality as needed.

[0043] An IFFT may be used to generate a time-domain digital waveform (with in-phase and quadrature components) representing the sum of the test RF subcarriers. The test frequency, test amplitude, and test phase may be checked by running a time series of a continuous time-domain analog drive signal corresponding to the time-domain digital waveform and observing spikes and / or EMEs. As a non-limiting example, spikes may be observed because the phase relationship between the RF subcarriers at the test frequency is additive (i.e., the amplitudes add constructively). In one embodiment, one or more of the test frequency and test amplitude may be selected, at least in part, using a constellation map to represent a respective RF signal modulated using one or more of QAM and phase shift keying.

[0044] FIG. 2 illustrates an embodiment of a process 200 for selecting component frequencies and amplitudes for component RF test frequencies that can be used to generate a spectrally shaped time-domain digital waveform of a spectrally shaped RF signal (e.g., a spectrally shaped drive signal).

[0045] In operation 202, process 200 receives an indication of the acceptable EME for each available frequency. In some embodiments, the acceptable EME may be described as an EME requirement and may be described for each available frequency.

[0046] In operation 204, process 200 selects test frequencies from the available frequencies and selects test amplitudes. In the particular non-limiting example process shown in Figure 2, there is a phase relationship between the selected test frequencies, and each test frequency is orthogonal to all of the other test frequencies.

[0047] In operation 206, process 200 allocates RF subcarriers, each having a frequency and amplitude specified by the test frequency and test amplitude of the selected test frequency and test amplitude.

[0048] In operation 208, process 200 generates a test time-domain digital waveform that is the sum of the RF subcarriers. In some embodiments, the test time-domain digital waveform may be generated in the digital domain by performing an IFFT using test frequencies, test amplitudes, and / or phase relationships (discussed below) of each of the RF subcarriers.

[0049] In optional operation 210, process 200 generates a time series of test drive signals responsive to the test time-domain digital waveform.

[0050] In some cases, the phase relationship of the test frequencies of the RF subcarriers may result in spikes (i.e., as a non-limiting example, amplitudes outside the dynamic range of the touch sensor). In optional operation 212, process 200 observes spikes, if any, in the time series of the test drive signal. In optional operation 214, process 200 determines whether all observed spikes are within the dynamic range of the touch sensor. If it is determined that one or more observed spikes are not within the dynamic range of the touch sensor, in operation 214, process 200 selects a new phase relationship between the test frequencies of the particular RF subcarriers associated with the observed spikes that are outside the dynamic range of the sensor and loops back to operation 206.

[0051] If the observed spike is determined to be within the dynamic range of the touch sensor, then in optional operation 218, process 200 generates and provides a test drive signal to the touch sensor and observes the spectral characteristics exhibited by the touch sensor (e.g., without limitation, EME noise) while the test drive signal is provided to the touch sensor.

[0052] In operation 220, process 200 compares the observed spectral characteristics (for example, but not limited to, EME noise) to the acceptable spectral characteristics of the touch sensor.

[0053] In operation 222, process 200 determines whether the observed spectral characteristics are within the acceptable spectral characteristics. If process 200 determines that the observed spectral characteristics are not within the acceptable spectral characteristics, in operation 224, process 200 selects new frequencies and / or amplitudes for the test frequency and test amplitude, assigns RF subcarriers, and loops back to operation 208. If process 200 determines that the observed spectral characteristics are within the acceptable spectral characteristics, in operation 226, process 200 stores the time-domain digital waveform of operation 208 and, alternatively or additionally, stores component frequency, amplitude, and / or phase relationships for the RF subcarriers. The time-domain digital waveform determined according to process 200 is a non-limiting example of a spectrally shaped time-domain digital waveform. The stored time-domain waveform corresponds to a quadrature amplitude modulated signal.

[0054] As discussed herein, test frequencies may be selected using at least part of process 200 that have low cross-correlation (and therefore low coherence). Stated differently, waveforms may be selected (i.e., they are stored in operation 226) to optimize the degree of orthogonality between the test frequencies, and ultimately between the respective frequencies of the RF subcarriers selected to generate the sensor drive signals.

[0055] FIG. 3 is a functional block diagram illustrating a functional block 300 for generating an encoded digital signal (a bitstream in the particular non-limiting example illustrated by FIG. 3 ) in which information about a spectrally shaped time-domain digital waveform is encoded on the digital signal.

[0056] The inputs to function block 300 are the phase relationships 310, amplitudes 312, and component frequencies 308 corresponding to the desired spectrally shaped time-domain digital waveform. As discussed herein, the desired spectrally shaped time-domain digital waveform may be a test waveform or a waveform selected to generate a drive signal.

[0057] In the embodiment shown in FIG. 3 , functional block 300 includes several functional blocks, described further below: a constellation mapper 302, an IFFT transformer 304, and a serializer 306. The constellation mapper 302 receives the phase relationships 310, amplitudes 312, and component frequencies 308 and, in response, generates and provides a constellation map 314. Any suitable technique for generating a constellation map known to those skilled in the art may be performed by the constellation mapper 302. The IFFT transformer 304 receives the constellation map 314 and, in response, generates a spectrally shaped time-domain digital waveform 316 responsive to the constellation map 314. The output of the IFFT transformer 304 includes a real or “in-phase” portion (denoted as the I component) and an imaginary or “quadrature” portion (denoted as the Q component). Typically, the output of the IFFT transformer 304 will be parallelized data. The serializer 306 receives the parallelized data and, in response, generates a bit stream representing the spectrally shaped time-domain digital waveform 318 (in other words, the “serialized spectrally shaped time-domain digital waveform 318”).

[0058] In various embodiments, the time-domain digital waveform 318 may be an encoded bitstream (i.e., a particular sequence of 1s and 0s) that, when repeatedly input into a digital-to-analog converter (DAC), causes the DAC to generate a continuous time-domain analog signal corresponding to the time-domain digital waveform 318.

[0059] In various embodiments, the time-domain digital waveform 318 may be stored and used to generate a spectrally shaped drive signal by a touch controller, including touch controller 402, as discussed herein.

[0060] FIG. 4 is a block diagram illustrating a touch sensing system 400 configured to implement drive signals, including a spectrally shaped drive signal generated in accordance with one or more embodiments. The example touch sensing system 400 shown in FIG. 4 includes a touch controller 402 operably coupled to a touch sensor 404 such that the touch controller 402 can be in electrical communication with the touch sensor 404. The touch controller 402 can be configured to provide a drive signal 412 to one or more sensor lines (e.g., drive lines, not shown) of the touch sensor 404 and observe a sensed signal 414 indicative of sensor capacitance on the one or more sensor lines (e.g., sense lines, not shown). The touch controller 402 includes a transmit path 406 (Tx 406 in FIG. 4 ) configured to generate a spectrally shaped drive signal according to one or more embodiments as discussed herein. The touch controller also includes a receive path 408 (Rx 408 in FIG. 4 ) for receiving the sensed signal 414 according to one or more embodiments as discussed herein.

[0061] In particular, the signals at Rx 408 and Tx 406 may be asynchronous with respect to one another due to the phase lag introduced by the touch sensor 404. In other words, in the disclosed embodiments, Rx 408 and Tx 406 do not necessarily need to be synchronized to compensate for the phase lag introduced by the touch sensor 404.

[0062] The touch controller 402 may be configured to store a spectrally shaped time-domain digital waveform for generating a spectrally shaped drive signal, such as the spectrally shaped time-domain digital waveform 318 of FIG. 3. To generate the drive signal 412, the touch processor 410 may be configured to provide a drive control signal 416 to the Tx 406. More specifically, the drive control signal 416 may be a spectrally shaped time-domain digital waveform stored in the touch controller 402 and used by the touch processor 410. Even more specifically, the spectrally shaped time-domain digital waveform may include an I component and a Q component, each stored in the touch controller 402. The control signal 416 may be a bitstream including the spectrally shaped time-domain digital waveform that is repeated as necessary to generate a continuous waveform.

[0063] The transmit path Tx 406 may be configured to generate the drive signal 412 in response to a drive control signal 416, for example, as discussed with reference to Figure 5. The drive signal 412 is spectrally shaped in response to the drive control signal 416 being a spectrally shaped time-domain digital waveform stored in the touch controller 402.

[0064] 5 is a functional block diagram illustrating an embodiment of a transmit path 500 for generating a spectrally shaped drive signal. In some embodiments, the transmit path 406 (Tx 406) of FIG. 4 may be configured as the transmit path 500 of FIG. 5. In some embodiments, the transmit path 500 may be used to generate a drive signal for performing touch sensing operations. In some embodiments, the transmit path 500 may be used to generate a test drive signal, such as the test drive signal discussed with reference to FIG. 2.

[0065] 5, the input to the transmit path 500, in this particular example, is the I and Q components of a spectrally shaped time-domain digital waveform 506 stored in a computer-readable memory 512. The spectrally shaped time-domain digital waveform 506 may correspond to a serialized spectrally shaped time-domain digital waveform generated by performing an IFFT and serialization, for example, by the IFFT transformer 304 and serializer 306, as described with reference to FIG.

[0066] A digital-to-analog conversion (DAC) block 502 receives a serialized spectrally shaped time-domain digital waveform 506 (more specifically, its I and Q components) and, in response, generates the I and Q components of a spectrally shaped continuous time-domain analog signal 510. A signal summation block 504 receives the I and Q components of the spectrally shaped continuous time-domain analog signal 510 and, in response, generates a spectrally shaped drive signal 508. More specifically, in the signal summation block 504, the I and Q components of the spectrally shaped continuous time-domain analog signal 510 are mixed to generate an IQ-modulated output waveform.

[0067] Optionally, additional RF modulation of this baseband signal (ie, spectrally shaped continuous time domain analog signal 508) may be performed if desired.

[0068] 6 is a functional block diagram illustrating a receive path 600 for receiving a spectrally shaped continuous time domain analog signal in accordance with one or more embodiments. As a non-limiting example, the received spectrally shaped continuous time domain analog signal of receive path 600 may be the spectrally shaped continuous time domain analog signal 508 (FIG. 5), or more specifically, the detected signal that includes the same. In some embodiments, the receive path of a touch controller, such as Rx 408 for touch controller 402, may be configured as receive path 600.

[0069] The IQ demodulation and ADC block 610 receives an analog detected signal containing I and Q components and performs analog-to-digital conversion and IQ demodulation on the detected signal to generate a digital signal containing I and Q information.

[0070] The parallelization block 608 defines a set of digital I and Q components and quadrature carriers and generates parallelized digital data (I and Q) in response to the length of the IFFT / FFT sequence expected by the FFT decoding block 606. The parallelization block 608 provides the I and Q components of the parallelized digital data to the I and Q inputs, respectively, of the FFT decoding block 606.

[0071] The FFT decoding block 606 generates a constellation map in response to the respective I and Q components of the parallelized digital data received at its I and Q inputs, more specifically by applying an FFT to the parallelized digital data.

[0072] The amplitude reconstruction block 604 generates amplitude values ​​for the constellation map output by the FFT decoding block 606. In one embodiment, the amplitude values ​​may indicate the amount or degree of attenuation of one or more component RF signals used to generate the drive signal.

[0073] The weighted sum block 602 outputs a sensor capacitance estimate in response to the amplitude value. In one embodiment, a touch processor (such as touch processor 410 of FIG. 4) may be configured to detect a touch in response to the sensor capacitance estimate, for example, by observing that the sensor capacitance estimate exceeds a specified threshold for detecting a touch.

[0074] 7 is a block diagram of a circuit 700 that, in some embodiments, may be used to implement various functions, operations, acts, processes, and / or methods disclosed herein. The circuit 700 includes one or more processors 702 (sometimes referred to herein as “processors 702”) operably coupled to one or more data storage devices (sometimes referred to herein as “storage devices 704”). The storage devices 704 include machine-executable code 706 stored thereon, and the processors 702 include logic circuitry 708. The machine-executable code 706 includes information that describes functional elements that may be implemented (e.g., executed) by the logic circuitry 708.

[0075] Logic circuitry 708 is adapted to implement (e.g., execute) the functional elements described by machine-executable code 706. Circuitry 700, when executing the functional elements described by machine-executable code 706, should be considered as dedicated hardware configured to perform the functional elements disclosed herein. In some embodiments, processor 702 may be configured to execute the functional elements described by machine-executable code 706 sequentially, concurrently (e.g., on one or more different hardware platforms), or in one or more parallel processing streams.

[0076] When implemented by the logic circuitry 708 of the processor 702, the machine-executable code 706 is configured to adapt the processor 702 to perform the operations of the embodiments disclosed herein. For example, the machine-executable code 706 may be configured to adapt the processor 702 to perform at least a portion of, or all of, process 100 of Figure 1, process 200 of Figure 2, transmit path 500 of Figure 5, and receive path 600 of Figure 6. As another example, the machine-executable code 706 may be configured to adapt the processor 702 to perform at least a portion of, or all of, the operations discussed for function block 300 of Figure 3, touch controller 402, Tx path 406, Rx path 408, and / or touch processor 410 of Figure 4.

[0077] The processor 702 may include a general-purpose processor, a special-purpose processor, a central processing unit (CPU), a microcontroller, a programmable logic controller (PLC), a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, other programmable devices, or any combination thereof designed to perform the functions disclosed herein. A general-purpose computer that includes a processor is considered a special-purpose computer, and a general-purpose computer is configured to execute computing instructions (e.g., software code) related to embodiments of the present disclosure.

[0078] It is noted that a general purpose processor may be a microprocessor, but alternatively, the processor 702 may be any conventional processor, controller, microcontroller, or state machine. The processor 702 may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in combination with a DSP core, or any other such configuration.

[0079] In some embodiments, the memory device 704 includes a volatile data storage device (e.g., random access memory (RAM)), a non-volatile data storage device (e.g., flash memory, a hard disk drive, a solid state drive, an erasable programmable read-only memory (EPROM), etc.). In some embodiments, the processor 702 and the memory device 704 may be implemented in a single device (e.g., a semiconductor device product, a system-on-chip (SOC), etc.). In some embodiments, the processor 702 and the memory device 704 may be implemented in separate devices.

[0080] In some embodiments, machine-executable code 706 may include computer-readable instructions (e.g., software code, firmware code). As a non-limiting example, the computer-readable instructions may be stored by storage 704, accessed directly by processor 702, and executed by processor 702 using at least logic circuitry 708. Also, as a non-limiting example, the computer-readable instructions may be stored in storage 704, transferred for execution to a memory device (not shown), and executed by processor 702 using at least logic circuitry 708. Thus, in some embodiments, logic circuitry 708 includes electrically configurable logic circuitry 708.

[0081] In some embodiments, machine-executable code 706 may describe hardware (e.g., circuits) to be implemented in logic circuitry 708 to perform functional elements. This hardware may be described at any of a variety of levels of abstraction, ranging from low-level transistor layouts to high-level description languages. At high levels of abstraction, a hardware description language (HDL) may be used, such as, but not limited to, the Hardware Description Language (HDL) adopted by the Institute of Electrical and Electronics Engineers (IEEE). As non-limiting examples, Verilog™, System Verilog™, or Very Large Scale Integration (VLSI) Hardware Description Language (VHDL™) may be used.

[0082] The HDL description may be converted into a description at any of a number of other levels of abstraction, as desired. As a non-limiting example, the high-level description may be converted into a logic-level description, such as a register transfer language (RTL), a gate-level (GL) description, a layout-level description, or a mask-level description. As a non-limiting example, the micro-operations performed by hardware logic circuits (e.g., but not limited to, gates, flip-flops, registers) of logic circuit 708 may be described in RTL and then converted by a synthesis tool into a GL description, which may be converted by a place-and-route tool into a layout-level description that corresponds to the physical layout of an integrated circuit of programmable logic devices, discrete gate or transistor logic, individual hardware components, or a combination thereof. Thus, in some embodiments, machine-executable code 706 may include HDL, RTL, a GL description, a mask-level description, other hardware descriptions, or any combination thereof.

[0083] In embodiments in which machine-executable code 706 includes a hardware description (at any level of abstraction), a system (not shown, but including storage 704) may be configured to implement the hardware description described by machine-executable code 706. As a non-limiting example, processor 702 may include a programmable logic device (e.g., an FPGA or PLC), and logic circuitry 708 may be electronically controlled to implement circuitry in logic circuitry 708 that corresponds to the hardware description. Also, as a non-limiting example, logic circuitry 708 may include hardwired logic manufactured by a manufacturing system (not shown, but including storage 704) according to the hardware description in machine-executable code 706.

[0084] Regardless of whether machine-executable code 706 includes computer-readable instructions or a hardware description, logic circuitry 708, when implementing the functional elements of machine-executable code 706, is adapted to perform the functional elements described by machine-executable code 706. Note that the hardware description may not directly describe the functional elements, but rather the hardware description indirectly describes the functional elements that the hardware elements described by the hardware description can perform.

[0085] In this disclosure, characterizations of something as "typical," "conventional," or "known" do not necessarily mean that it is disclosed in the prior art or that the discussed aspect is recognized in the prior art, or that it is widely known, well understood, or routinely used in the relevant field.

[0086] The terms used in this disclosure, and particularly in the appended claims (e.g., the body of the appended claims), are generally intended as "open" terms (e.g., the term "including" should be interpreted as "including, but not limited to," the term "having" should be interpreted as "having at least," the term "including" should be interpreted as "including, but not limited to," etc.).

[0087] Additionally, where a specific number is intended in an introduced claim recitation, such intention will be expressly recited in the claim; absent such recitation, no such intention exists. For example, as an aid to understanding, the following appended claims may include the use of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed as limiting any particular claim containing such introduced claim recitation to embodiments including only one of such recitations, even if the same claim includes the introductory phrases "one or more" or "at least one" and an indefinite article such as "a" or "an" (e.g., "a" and / or "an" should be construed to mean "at least one" or "one or more"). The same applies to the use of definite articles used to introduce claim recitations.

[0088] Additionally, even when a particular number of introduced claim recitations is explicitly recited, those skilled in the art will recognize that such recitation should be interpreted to mean at least the recited number (e.g., an explicit recitation of "two recitations" without other modifiers means at least two recitations or more than two recitations). Furthermore, when conventions similar to "at least one of A, B, and C, etc." or "one or more of A, B, and C, etc." are used, it is generally intended that such a structure include A only, B only, C only, A and B together, A and C together, B and C together, or A, B, and C together.

[0089] Furthermore, any disjunction or phrase presenting two or more alternative terms, whether in the specification, claims, or drawings, should be understood to intend the possibility of including one of the terms, either of the terms, or both terms. For example, the phrase "A or B" should be understood to include the possibilities of "A" or "B" or "A and B."

[0090] One or more non-limiting embodiments of the present disclosure are as follows. Embodiment 1: A touch sensing method comprising: generating a drive signal characterized by an energy of the drive signal allocated across particular frequencies of a subcarrier; providing the drive signal to a touch sensor; receiving a sensed signal at the touch sensor; observing the energy of the sensed signal; and detecting a touch at the touch sensor in response to observing that the observed energy of the sensed signal is different from the energy of the drive signal.

[0091] Embodiment 2: A touch sensing method as described in embodiment 1, wherein generating a drive signal characterized by the energy of the drive signal being allocated across specific frequencies includes generating a spectrally shaped continuous time domain analog signal; and generating the drive signal in response to the spectrally shaped continuous time domain analog signal.

[0092] Embodiment 3: A touch sensing method as described in embodiments 1 and 2, wherein the step of generating a drive signal in response to the spectrally shaped continuous time-domain analog signal includes the step of mixing in-phase and quadrature-phase components of the spectrally shaped continuous time-domain analog signal.

[0093] Embodiment 4: The touch sensing method of embodiments 1-3, further comprising observing a channel capacitance of the touch sensor in response to the observed energy of the sensed signal.

[0094] Embodiment 5: The touch sensing method of embodiments 1-4, further comprising detecting a touch with the touch sensor in response to observing a change in channel capacitance of the touch sensor.

[0095] Embodiment 6: A touch sensing method as described in embodiments 1 to 5, wherein generating a drive signal characterized by an energy of the drive signal allocated across specific frequencies includes generating a spectrally shaped drive signal selected so that the touch sensor exhibits spectral characteristics at multiple frequencies, the spectral characteristics being within an index of acceptable spectral characteristics.

[0096] Embodiment 7: A touch sensing system comprising: a touch sensor; and a touch controller configured to generate a drive signal characterized by an energy of the drive signal allocated across a particular frequency of a subcarrier, provide the drive signal to the touch sensor, observe an energy of a sensed signal received from the touch sensor, and detect a touch at the touch sensor in response to observing that the observed energy of the sensed signal is different from the energy of the drive signal.

[0097] Embodiment 8: A touch sensing system as described in embodiment 7, wherein generating a drive signal characterized by the energy of the drive signal being allocated across specific frequencies includes generating a spectrally shaped continuous time domain analog signal and generating the drive signal in response to the spectrally shaped continuous time domain analog signal.

[0098] Embodiment 9: A touch sensing system as described in embodiments 7 and 8, wherein generating the drive signal in response to the spectrally shaped continuous time-domain analog signal includes mixing in-phase and quadrature-phase components of the spectrally shaped continuous time-domain analog signal.

[0099] Embodiment 10: The touch sensing system of embodiments 7-9, wherein the touch controller is further configured to observe a channel capacitance of the touch sensor in response to observed energy of the sensed signal.

[0100] Embodiment 11: A touch sensing system as described in embodiments 7 to 10, wherein generating a drive signal characterized by the energy of the drive signal being allocated across specific frequencies involves generating a spectrally shaped drive signal selected so that the touch sensor exhibits spectral characteristics at multiple frequencies, the spectral characteristics being within an index of acceptable spectral characteristics.

[0101] Embodiment 12: A method for determining a spectrally shaped waveform, the method comprising the steps of receiving an indication of acceptable electromagnetic emissions, selecting radio frequency subcarriers in response to the indication of acceptable electromagnetic emissions, and generating and storing a spectrally shaped time domain digital waveform in response to the selected radio frequency subcarriers.

[0102] Embodiment 13: The method of embodiment 12, further comprising performing quadrature amplitude modulation using radio frequency subcarriers.

[0103] Embodiment 14: The method of embodiments 12 and 13, further comprising selecting a specified amplitude and a specified frequency for each of the radio frequency subcarriers.

[0104] Embodiment 15: The method of any one of embodiments 12 to 14, wherein the step of selecting radio frequency subcarriers in response to the indicator of allowable electromagnetic emissions includes the steps of selecting a test frequency and a test amplitude, and generating a test time-domain digital waveform of a test drive signal in response to the radio frequency subcarriers, each radio frequency subcarrier having a frequency and amplitude specified by the selected test frequency and test amplitude, respectively; generating the test drive signal; providing the generated test drive signal to a touch sensor; and storing the test time-domain digital waveform of the test drive signal in response to detecting that the observed electromagnetic emissions of the touch sensor are within the allowable electromagnetic emissions.

[0105] Embodiment 16: The method of any one of embodiments 12 to 15, further comprising generating a time series of test drive signals in response to the test time-domain digital waveform, and observing spikes, if any, in the time series of test drive signals.

[0106] Embodiment 17: The method of embodiments 12-16, further comprising selecting a new phase relationship between the radio frequency subcarriers in response to observing that one or more of the observed spikes are outside the dynamic range of the touch sensor.

[0107] Embodiment 18: The method according to embodiments 12 to 17, further comprising: generating a bitstream in response to the spectrally shaped time-domain digital waveform; and storing the bitstream in the touch controller.

[0108] While the present disclosure has been described herein with reference to certain illustrated embodiments, those skilled in the art will recognize and appreciate that the present invention is not so limited. Rather, numerous additions, deletions, and modifications can be made to the illustrated and described embodiments without departing from the scope of the invention as claimed below, along with their legal equivalents. In addition, features of one embodiment can be combined, as contemplated by the inventor, with features of other disclosed embodiments and still fall within the scope of the present disclosure.

Claims

1. 1. A touch sensing method, comprising: generating a drive signal, the drive signal being characterized by energy of the drive signal distributed across particular frequencies of orthogonal subcarriers, the subcarriers being selected in response to an indication of acceptable spectral characteristics; providing the drive signal to a touch sensor, wherein the spectral characteristics exhibited by the touch sensor at the particular frequency of the subcarrier are within an indication of the acceptable spectral characteristics; receiving a detected signal from the touch sensor; observing the energy of the detected signal; detecting a touch at the touch sensor in response to observing that the observed energy of the sensed signal is different from the energy of the assigned drive signal.

2. The step of generating the drive signal includes: generating a spectrally shaped time domain digital waveform using selected RF (radio frequency) orthogonal subcarriers, and generating a spectrally shaped continuous time domain analog signal in response to the spectrally shaped time domain digital waveform; and generating the drive signal in response to the spectrally shaped continuous time domain analog signal.

3. generating the drive signal in response to the spectrally shaped continuous time domain analog signal, The touch sensing method of claim 2 , comprising mixing in-phase and quadrature-phase components of the spectrally shaped continuous time-domain analog signal.

4. The touch sensing method of claim 1 , further comprising observing a channel capacitance of the touch sensor in response to the observed energy of the sensed signal.

5. The touch sensing method of claim 4 , further comprising detecting a touch at the touch sensor in response to observing a change in the channel capacitance of the touch sensor.

6. 1. A touch sensing system, comprising: A touch sensor; A touch controller, the touch controller comprising: generating a drive signal, the generated drive signal characterized by energy of the drive signal allocated across particular frequencies of orthogonal subcarriers, the subcarriers being selected in response to an indication of acceptable spectral characteristics; providing the drive signal to the touch sensor, wherein the spectral characteristics exhibited by the touch sensor at the particular frequency of the subcarrier are within an indication of the acceptable spectral characteristics; observing the energy of a sensed signal received from the touch sensor; a touch controller configured to detect a touch at the touch sensor in response to observing an observed energy of the sensed signal that is different from an energy of the assigned drive signal.

7. The generating of the drive signal comprises: generating a spectrally shaped time domain digital waveform using selected RF (radio frequency) orthogonal subcarriers, and generating a spectrally shaped continuous time domain analog signal in response to the spectrally shaped time domain digital waveform; and generating the drive signal in response to the spectrally shaped continuous time domain analog signal.

8. said generating said drive signal in response to said spectrally shaped continuous time domain analog signal comprising: The touch sensing system of claim 7 , comprising mixing in-phase and quadrature-phase components of the spectrally shaped continuous time-domain analog signal.

9. The touch controller The touch sensing system of claim 6 , further configured to observe a channel capacitance of the touch sensor in response to the observed energy of the sensed signal.

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