Frequency-based noise removal

Abstract

An electronic device samples a radio frequency signal measured by a plurality of antennas positioned across a digitizer, where the radio frequency signal includes a noise component. The electronic device selects an orthogonal frequency outside of the defined bandwidth of the operating frequency and removes at least some of the noise components from the radio frequency signal measured by each antenna based at least on the sensing signal measured by each antenna at the orthogonal frequency.

Description

Background Art

[0001] Many modern computing devices support touch input and electronic stylus interaction via a sensor panel on the computing device's display. The sensor panel includes an antenna array capable of detecting transmissions from an active stylus and / or changes in capacitance on or near the display surface, such as those caused by the proximity, removal, or presence of a conductive object (e.g., a finger or stylus). The locations of the antennas in the array that detect the signals / capacitance changes correspond to the locations of the conductive objects on or near the display. In this way, the sensor panel enables the computing device to track touch and stylus position on the display. Summary of the Invention

[0002] In some aspects, the techniques described herein relate to a method of managing RF noise in a digitizer to detect an active stylus signal having an operating frequency within a defined bandwidth, the method comprising sampling RF signals measured by a plurality of antennas positioned across the digitizer, wherein the RF signals include a noise component; selecting an orthogonal frequency outside the defined bandwidth of the operating frequency; and removing at least some of the noise component from the RF signal measured by each antenna based at least on a sensed signal measured by each antenna at the orthogonal frequency.

[0003] In some aspects, the techniques described herein relate to a system for managing RF noise in a digitizer to detect an active stylus signal having an operating frequency within a defined bandwidth, the system comprising one or more hardware processors; a signal sampler executable by the one or more hardware processors and configured to sample RF signals measured by multiple antennas positioned across the digitizer, wherein the RF signals include a noise component; a frequency selector executable by the one or more hardware processors and configured to select an orthogonal frequency outside the defined bandwidth of the operating frequency, wherein the orthogonal frequency differs from the operating frequency by at least an inverse of a correlator window duration; and a noise cleaner executable by the one or more hardware processors and configured to remove at least some noise components from the RF signal measured by each antenna based at least on a sensed signal measured by each antenna at the orthogonal frequency.

[0004] In some aspects, the technology described herein relates to one or more tangible, processor-readable storage media carrying instructions for executing, on one or more processors and circuits of a computing device, a process for managing radio frequency noise in a digitizer to detect an active stylus signal having an operating frequency within a defined bandwidth, the process comprising: sampling radio frequency signals measured by a plurality of antennas positioned across the digitizer, wherein the radio frequency signals include a noise component; selecting an orthogonal frequency outside the defined bandwidth of the operating frequency; and removing at least some of the noise component from the radio frequency signal measured by each antenna based at least on a sensed signal measured by each antenna at the orthogonal frequency and a sensed signal measured by a reference antenna at the orthogonal frequency.

[0005] This summary is intended to introduce some concepts in a simplified form. These concepts are further elaborated in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0006] Other implementations are also described and listed herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 An example of an electronic device including a touch screen and a noise remover is shown.

[0008] Figure 2 Examples of quadrature frequencies related to the operating frequency are shown.

[0009] Figure 3 An example of the operation of frequency-based noise removal is shown.

[0010] Figure 4 Examples of cleanup results obtained using different noise removal techniques are shown.

[0011] Figure 5 An exemplary computing device for implementing the described techniques is shown. DETAILED DESCRIPTION

[0012] The described technology aims to provide accurate tracking on the display screen of an electronic device by removing at least some of the noise from the signals received by the antenna array in a sensor panel (sometimes called a digitizer). Sources of noise may include, but are not limited to, radio frequency (RF) emissions generated by the display itself and other RF signals from the environment. For example, a nearby RF emission source (such as a poorly shielded hi-fi system) may generate an RF noise signal that can be detected by the antennas in the array and interpreted as an attempt by a stylus to draw digital ink on the display screen. If the noise signal detected by the sensor panel is of sufficient strength (e.g., exceeding a preset threshold), the presence and XY position of the electronic stylus tip relative to the display screen can be detected. In some cases, the noise can reduce the strength of the stylus signal and introduce errors in the sensor panel's detection. Even in the absence of actual touch or writing events, background noise experienced by the sensor panel antennas can introduce erroneous writing (e.g., "ghost ink"), negatively impact power consumption (e.g., by attempting to synchronize with a non-existent stylus), and introduce delays in detecting real events.

[0013] Existing noise removal techniques are based on assumptions about the characteristics of the sensor panel (e.g., assuming that the noise response is relatively consistent from one side of the sensor panel to the other) and typically rely on the position or index of a reference antenna (e.g., an antenna in the sensor panel that does not participate in touch detection) in a row or column of the sensor array. However, in some electronic device touch screen implementations, such assumptions do not hold. For example, some devices have a stronger noise response in the center area of ​​the display screen than in the edge area, which results in the selection of one antenna as a reference antenna rather than another, which can have a significant impact on the accuracy of noise removal. It should be understood that noise removal does not need to be perfect or complete. Instead, noise removal may remove some or all of the noise components from the sensed signal, especially frequency-based methods, to provide the technical advantage of more accurate stylus signal detection, thereby minimizing or reducing false ink and other undesirable artifacts.

[0014] Accordingly, the technology employs frequency-based elements to perform noise removal when possible. In particular, the technology improves the removal of background noise, regardless of the presence of a stylus or other conductive object, to reduce the likelihood of false positives due to background noise.

[0015] Figure 1An example of an electronic device 100 is shown, including a touch screen 102 and a noise remover 106. The electronic device 100 can be in the form of a mobile phone, a tablet computer, a touchpad, a laptop computer, a desktop computer, a touch screen display, etc. The touch screen 102 includes a digitizer 104 having an antenna array arranged along the x-axis and the y-axis. The electronic device 100 also includes one or more input / output controllers (e.g., I / O controller 108) and other components. The I / O controller 108 includes a combination of random access memory (RAM), sensing channels, channel scanning logic, a charge pump, and driver logic, which manages touch and / or stylus sensing through the digitizer. The I / O controller 108 is connected to the antenna array to receive touch and / or stylus input when the touch screen 102 is in use. In various embodiments, the touch screen 102 may also include an array of light-emitting elements (e.g., pixels) to provide display functionality.

[0016] The antennas in the touch screen 102 are arranged along the x-axis and indexed from 0 to X, and along the y-axis and indexed from 0 to Y. The antennas in each direction extend along their respective axes to the touch screen 102 and overlap at intersections called "touch nodes" (e.g., touch node 107), although other antenna configurations may also form touch nodes (e.g., adjacent antennas rather than overlapping antennas). In one embodiment, the x-axis antennas are referred to as "sense lines" and the y-axis antennas are referred to as "drive lines," although other embodiments may also be used. The I / O controller 108 can detect and measure active stylus signals and / or capacitance changes to determine the xy position of one or more conductive objects when they touch or are in proximity to the antennas in the touch screen 102. The I / O controller 108 is electrically connected to the drive lines through the drive interface 110 and to the sense lines through the sense interface 112.

[0017] In some embodiments, an AC waveform is provided to the drive line, and the change in capacitance of the corresponding touch node can be measured. When a conductive object approaches a touch node, the capacitance value of the touch node changes (for example, the capacitance value decreases in a mutual-capacitive touch screen and increases in a self-capacitive touch screen) due to capacitive coupling with the approaching conductive object (such as a finger). Similarly, when the conductive object moves away from the touch node, the capacitance value of the touch node changes to indicate the object's removal.

[0018] In some embodiments, the digitizer of touch screen 102 can sense an electronic stylus, which can generate an active stylus signal. An example of an active stylus signal is generally centered around a 25kHz radio frequency signal, where 25kHz is referred to as the "working frequency" or "WF" of the electronic stylus signal. In some embodiments, digitizer 104 is synchronized with the display signal to open a window in time (e.g., a scan window or correlator window duration) in which the sense lines "listen" for the active stylus signal to determine the position of the electronic stylus tip. By correlating the rows and columns of antennas in digitizer 104 that detect the active stylus signal, I / O controller 108 can determine the position of the electronic stylus tip on the x-axis and y-axis of touch screen 102. For example, the antenna values ​​within the scan window are sampled and converted to DFTs (discrete Fourier transforms). If the DFT values ​​measured by digitizer 104 for one or more specific antennas exceed a pen detection threshold, an active stylus signal is detected. After detecting the electronic stylus signal, the I / O controller 108 tracks the active stylus signal via the digitizer 104. Furthermore, in some embodiments, the touch screen 102 can distinguish between an active stylus signal and a finger or palm touching the touch screen 102 (e.g., for palm rejection). Accordingly, in some embodiments, the touch screen 102 can be configured to detect both passive conductive objects (e.g., fingers, passive styluses) and active styluses.

[0019] Various detection functions of touch screen 102 may be negatively impacted by electromagnetic noise, which is categorized herein as external noise sources (e.g., external noise sources 116) and internal noise sources (e.g., internal noise sources 118). Exemplary external noise sources 116 may include nearby audio speakers, external display screens, etc. Exemplary internal noise sources 118 may include electronic system components such as processors, memory, power supplies, etc., as well as other antennas and circuits within touch screen 102. Such noise may be falsely detected as an active stylus signal, resulting in erroneous ink (e.g., "ghost ink"), negatively impacting power consumption (e.g., attempting to synchronize with a non-existent stylus), delaying the detection of real events, etc. For example, in some cases, such noise may cause digital ink to appear on the touch screen display when no active stylus is present.

[0020] Accordingly, the noise remover 106 interacts with the I / O controller 108 to remove noise from the sensed signal processed by the I / O controller 108. In certain embodiments, referred to as "common noise removal" or "CNR," the noise remover 106 can remove noise from the sensed signal by subtracting the signal value sensed by a single reference antenna. For example, assume that the antennas (Ant(i)) are arranged along the x-axis, with indices from i=0 to 30. The noise remover 106 can select antenna Ant(10) as the reference antenna. Thus, using the following equation, the noise remover 106 can remove noise from the signal sensed by Ant(i) by subtracting the signal sensed by the reference antenna Ant(10):

[0021] Ant(i) WF_cleaned =Ant(i) WF -Ant(10) WF

[0022] Noise removal works best when the noise is distributed roughly evenly across the x-axis (or across the antenna distribution on the x-axis). In some cases, the noise is not evenly distributed across the antenna distribution (e.g., there is more noise at the center of the distribution than at the ends), which indicates that some antennas are sensing more noise than others. In this case, the choice of reference antenna can have a significant impact on noise removal. For example, if reference antenna Ant(10) senses more noise than Ant(i), the final "cleaned" signal value may be artificially lowered, even to a negative value, thereby falsely lowering the value of the active stylus signal sensed by Ant(i) and preventing it from meeting the pen detection threshold. Similarly, if reference antenna Ant(10) senses less noise than Ant(i), the final "cleaned" signal value may be artificially higher, even meeting the pen detection threshold in the absence of an active stylus. Thus, using a single reference antenna to clean noise from the digitizer's sensed signal may still result in incorrect detection of active stylus signals, leading to writing errors (e.g., "ghost ink"), negative impacts on power consumption (e.g., attempting to synchronize with a non-existent stylus), and delays in detecting real events.

[0023] Therefore, the noise remover 106 can use two or more reference antennas to remove noise through "background noise removal" or "BNR". The values ​​of the sensing signal are measured from multiple reference antennas, and the slope of the sensing signal values ​​along the x-axis (index axis) between the reference antennas is calculated. However, although BNR can work effectively in the area where the values ​​on the x-axis are significantly monotonically increasing or decreasing, in some cases, local spikes or other situations that do not conform to the sensing signal values ​​will appear. In this case, BNR may not be able to accurately remove the noise in the sensing signal, resulting in ink errors (such as "ghost ink"), negative impact on power consumption (such as trying to synchronize with a non-existent stylus), delays in detecting real events, etc. In addition, in some cases, there is no second reference antenna available in the target area, preventing BNR from removing at least some noise components. Accordingly, the technology can accurately remove noise in many situations where BNR cannot be used, thereby bringing technical advantages.

[0024] In this technique, rather than simply relying on the value of the sensed signal measured along the x-axis from a reference antenna, the noise remover 106 evaluates the frequency of the sensed signal. In this technique, an antenna in the digitizer that is not sensing touch input is selected as the reference antenna. The signal sampler 120 of the noise remover 106 samples the RF signal measured by multiple antennas on the digitizer, where the RF signal includes a noise component. By sampling signals from multiple antennas, the system offers the technical advantage of being able to detect the proximity of objects (including active styluses) on the display surface—the more antennas distributed across the digitizer array, the more accurately the object's position can be detected.

[0025] Frequency selector 122 of noise remover 106 evaluates the sensed signal at one or more selected frequencies that are close to the active stylus signal (e.g., in this example, centered at 25 kHz). Each selected frequency is referred to as an orthogonal frequency (e.g., orthogonal to the frequency of the active stylus signal) because the selected frequencies exclude the active stylus signal, and any signal at the selected frequencies can be assumed to be noise. For example, the active stylus signal can be assumed to be substantially visible only within a narrow bandwidth centered at 25 kHz and not at the orthogonal frequencies. Thus, the orthogonal frequencies are considered to be similar or close to the working frequency (WF), but do not include a substantial component of the active stylus signal (e.g., the bandwidth of the active stylus signal does not include the orthogonal frequencies).

[0026] In various embodiments, the frequency selector 122 may select a frequency based on the duration or period (T correlator ) selects the quadrature frequencies, for example using the following equations:

[0027]

[0028] In other embodiments, other adjacent frequencies may be selected as orthogonal frequencies, including frequencies where the signal value is known to be close to zero, which can be determined independently of the duration of the correlator. Orthogonal frequencies are sometimes referred to herein as "noise bin frequencies." Accordingly, in this context, orthogonality means that the frequency spacing is substantially Hertz, where T is the correlator duration (eg, scanning window size), and k is a positive integer, typically equal to 1. Orthogonal frequencies are expected to produce no or minimal crosstalk between the sensed signals of the frequencies.

[0029] The sensed signals at the quadrature frequencies are evaluated according to the cleanup ratio condition. In one embodiment, for the described technique, the effective quadrature frequencies have The ratio is within a predetermined upper and lower limit (described in detail below). Other cleaning ratio conditions can also be used.

[0030] If the frequency selector 122 selects a valid orthogonal frequency, the noise cleaner 124 subtracts a proportional portion of the sensed signal value measured by the antenna at the orthogonal frequency from the sensed signal value measured by the antenna at the operating frequency to obtain a cleaned sensed signal value measured by the antenna at the operating frequency. In one embodiment described below, the proportionality is based on a ratio of the sensed signal value measured by the reference antenna at the operating frequency to the sensed signal value measured by the reference antenna at the orthogonal frequency. In some embodiments, the sensed signal measured by the reference antenna includes a combination of sensed signals measured by multiple reference antennas, such as an average of the sensed signal values ​​of all reference antennas. In this manner, the noise cleaner 124 provides a technical advantage by removing at least some noise components from the sensed signal based, at least in part, on noise detected at frequencies known to be unaffected by and / or uncoupled from active stylus signals, thereby providing a more accurate level of noise removal.

[0031] In summary, noise remover 106 can use various methods to remove at least some of the noise from the sensed signal from digitizer 104, including CNR, BNR, and frequency-based noise removal. It should be understood that the techniques described can be applied to one or two axes of the digitizer (e.g., the x-axis and the y-axis), particularly for detecting active stylus signals—thus, noise removal can be performed along both axes. Furthermore, in some embodiments, the sense lines can be distributed across one or both axes of the digitizer.

[0032] Figure 2 An example of orthogonal frequencies related to the operating frequency is shown. The term "frequency bin" generally refers to a bin that includes information in the frequency axis and is defined between a low frequency limit f1 and a high frequency limit f h The segment between A noise bin is a DFT frequency bin that contains or is expected to contain noise rather than signal components. As used herein, the term "noise bin frequencies" refers to the orthogonal frequencies within a noise bin.

[0033] Figure 2 Graph 200 in FIG. 1 illustrates the concept of quadrature frequencies associated with an active stylus signal 202. The x-axis of graph 200 represents frequency, and the y-axis of graph 200 represents amplitude. Accordingly, if frequency 204 is the operating frequency of active stylus signal 202 and has a substantial amplitude to indicate the presence of active stylus signal 202, then frequencies 206 and 208 are quadrature frequencies (noise bin frequencies) characterized by little or no signal amplitude for active stylus signal 202.

[0034] In one embodiment, the quadrature frequency is as shown in equation (1) above, such that the difference between the operating frequency and the quadrature frequency is based on the duration of the correlator used to detect the active stylus signal (e.g., ). For example, based on T correlator =400 μs and an operating frequency of 25 kHz, 22.5 kHz and 27.5 kHz are selected as quadrature frequencies. In other embodiments, the quadrature frequencies may be selected in other ways (eg, selecting frequencies known not to include a substantial component of the active stylus signal 202).

[0035] Graph 210 shows the DFT amplitude value of the sensed signal of each antenna (indexed along the x-axis) before noise removal. Solid line 212 represents the sensed signal component of each antenna at an operating frequency of 25 kHz before cleaning. Dashed line 214 represents the sensed signal component of each antenna at a noise bin frequency of 22.5 kHz before cleaning. Dashed line 216 represents the sensed signal component of each antenna at a noise bin frequency of 27.5 kHz before cleaning. In the described technology, as Figure 2 As shown, one or more noise bin frequencies are used for frequency-based noise removal from the sensed signal in the digitizer.

[0036] Figure 3 An example of frequency-based noise removal operation 300 is shown. Operation 300 manages RF noise in a digitizer to detect active stylus signals operating within a defined bandwidth. Sampling operation 302 samples RF signals measured by multiple antennas on the digitizer. The RF signal includes a noise component of the RF noise.

[0037] A selection operation 304 selects an orthogonal frequency outside of a defined bandwidth of the operating frequency. In one embodiment, the selection operation 304 includes selecting the orthogonal frequency for removing at least some noise components based on a ratio of a sensed signal measured by the reference antenna at the operating frequency to a sensed signal measured by the reference antenna at the orthogonal frequency. In some embodiments, the orthogonal frequency differs from the operating frequency by at least an inverse of a correlator window duration.

[0038] In other embodiments, the selecting operation 304 includes determining, for each of the plurality of frequencies, a ratio of a sensed signal measured by the reference antenna at the operating frequency to a sensed signal measured by the reference antenna at each of the frequencies, and selecting a frequency from the plurality of frequencies whose ratio is closest to 1 as an orthogonal frequency for noise removal, because the frequency is considered to be more representative of the signal and is not affected by active stylus signals, touch input signals, or other noise components that appear at one orthogonal frequency but not at another orthogonal frequency. In certain embodiments, the selecting operation 304 includes determining, for each of the plurality of frequencies, a ratio of a sensed signal measured by the reference antenna at the operating frequency to a sensed signal measured by the reference antenna at each of the frequencies, and excluding from the selection of the orthogonal frequencies each frequency whose ratio does not satisfy the cleaning ratio condition.

[0039] As previously mentioned, the reference antenna enables the noise canceller to determine a reference noise level that is expected to exclude active noise signals. Similarly, two reference antennas can determine the slope of the sensed signal amplitude between two spatially separated antennas in the digitizer, allowing the noise canceller to interpolate and / or extrapolate the reference noise levels expected to be present at different locations in the digitizer. The dual-antenna approach is particularly effective when the noise distribution across the digitizer is uneven or non-uniform.

[0040] Nevertheless, the technique goes a step further by correlating the noise component with signal components at frequencies outside the operating frequency bandwidth, thereby removing at least some of the noise component from the sense signal based at least in part on proportional sense signal frequency components outside the operating frequency. WF The component is Ant(i) NB The component (expected to be mainly noise) is reduced by the ratio of the corresponding component on the reference antenna. In this way, when the ratio of the corresponding component sensed by the reference antenna is considered valid, the system provides a more accurate WF The technical advantage of removing at least part of the expected noise component from the component.

[0041] In some cases, using proportional sensed signal values ​​measured by the antennas (Ant(i)) at orthogonal frequencies to remove at least some of the noise components from each antenna may result in unsatisfactory results. Accordingly, in some embodiments, the ratio used in the proportional process is tested to determine whether it is effective (e.g., expected to provide satisfactory results). To verify the effectiveness of a potential orthogonal frequency, the ratio is compared to a cleaning ratio condition, such as a range from a low ratio lower limit to a high ratio upper limit (e.g., a low ratio lower limit of 0.693889 and a high ratio upper limit of 1.44). If Ant(Ref) WF with Ant(Ref) NB If the ratio of Ant(Ref) is not within the range between the low ratio limit and the high ratio limit, the ratio does not meet the cleaning ratio condition and the frequency is excluded as an orthogonal frequency. WF with Ant(Ref) NB The ratio of is within the range between the lower ratio limit and the upper ratio limit, the ratio satisfies the cleaning ratio condition, and the frequency is verified as a potential orthogonal frequency that can be used to remove at least some noise components. If all potential orthogonal frequencies are eliminated, data cleaning can be performed using BNR or CNR, although in some cases, BNR is performed before the described techniques.

[0042] Furthermore, if multiple frequencies meet the cleaning ratio condition to be considered as valid orthogonal frequencies, one of the frequencies may be selected as the orthogonal frequency for removing at least some noise components. For example, in one embodiment, the valid orthogonal frequency having a ratio closest to 1 compared to another valid orthogonal frequency may be selected for removing at least some noise components.

[0043] In other embodiments, the sensed signal value measured by the reference antenna at the operating frequency and the sensed signal value measured by the reference antenna at the orthogonal frequency may include a combination of measurement values ​​from multiple reference antennas, such as an average of sensed signal values ​​from four different reference antennas.

[0044] In some embodiments, the SQUARE_SUMMED_VALUE_RATIO parameter refers to a method for enhancing the electronic stylus signal by summing the DFT values ​​of adjacent antennas, so that the signals are summed and enhanced (for example, this method is useful when the electronic stylus is located between two adjacent antennas) - the operating frequency sensed signals are summed, while the noise bin frequency sensed signals are not summed. In this way, when calculating the ratio of the sensed signal value measured by the reference antenna at the operating frequency to the sensed signal value measured by the reference antenna at the orthogonal frequency, the difference in the relative contributions of the signals at these frequencies is taken into account (for example, by multiplying the denominator by the SQUARE_SUMMED_VALUE_RATIO parameter). For example: if the summation is performed for five adjacent antennas, it can be assumed that the SQUARE_SUMMED_VALUE_RATIO parameter value is equal to 5 when there is no active stylus signal.

[0045] The cleaning operation 306 removes at least some noise components from the radio frequency signal measured by each antenna based on the sensed signals measured by each antenna at the orthogonal frequencies. In some embodiments, the cleaning operation 306 includes removing at least some noise components from the radio frequency signal measured by each antenna based on the sensed signals measured by each antenna at the orthogonal frequencies and the sensed signals measured by the reference antenna at the orthogonal frequencies. In other embodiments, the cleaning operation 306 includes removing at least some noise components from the radio frequency signal of each antenna based on the sensed signals measured by each antenna at the orthogonal frequencies, the sensed signals measured by the reference antenna at the orthogonal frequencies, and the sensed signals measured by the reference antenna at the operating frequency. In other embodiments, the cleaning operation 306 includes removing at least some noise components from the radio frequency signal measured by each antenna at the operating frequency by subtracting a proportional amplitude of the sensed signals measured by each antenna of the plurality of antennas at the orthogonal frequencies, wherein the proportional amplitude is proportional to the ratio of the sensed signals measured by the reference antenna at the operating frequency to the sensed signals measured by the reference antenna at the orthogonal frequencies.

[0046] For example, in one embodiment, the cleaning operation 306 removes at least some noise from the sensed signal value measured by the antenna (Ant(i)) at the operating frequency by subtracting a proportional sensed signal value measured by the antenna (Ant(i)) at the orthogonal frequency. In one embodiment, the proportional processing is based on the ratio of the sensed signal value measured by the reference antenna at the operating frequency to the sensed signal value measured by the reference antenna at the orthogonal frequency, as shown below:

[0047]

[0048] in:

[0049] Ant(i) WF_cleaned= DFT value of the sensing signal measured by antenna Ant(i) at the operating frequency after cleaning

[0050] Ant(i) WF = DFT value of the sensing signal measured by antenna Ant(i) at the operating frequency before cleaning

[0051] Ant(i) NB = DFT value of the sensing signal measured by antenna Ant(i) at the orthogonal frequency before cleaning

[0052] Ant(Ref) WF = DFT value of the sensing signal measured by the antenna Ant(Ref) at the operating frequency before cleaning

[0053] Ant(Ref) NB = DFT value of the sensing signal measured by the antenna Ant(Ref) at the orthogonal frequency before cleaning

[0054] In one embodiment, complex division is used to obtain the subtrahend to be subtracted from the sensed signal value before cleaning by Ant(i) at the operating frequency as follows:

[0055] Given Then subtrahend The components of are expressed in complex form as follows:

[0056] Ant(i) NB =Re1+Im1·j

[0057] Ant(Ref) NB =Re2+Im2·j

[0058] Ant(Ref) WF =Re3+Im3·j

[0059] Accordingly, complex number division can be implemented using the following method:

[0060]

[0061] Therefore, the ratio of equation (2) is given by:

[0062]

[0063] Likewise, the following can be used to implement complex multiplication:

[0064] (a+bi)(c+di)=ac-bd+i(ad+bc)

[0065] Figure 4Example cleaning results obtained using different noise removal techniques are shown. Graph 400 shows the DFT magnitude values ​​of the sensed signal for each antenna (indexed along the x-axis). Solid line 402 indicates the sensed signal component at an operating frequency of 25 kHz before noise removal. Dashed line 404 indicates the sensed signal component at 25 kHz for each antenna after cleaning using a noise bin frequency of 22.5 kHz. Dashed line 406 indicates the sensed signal component at 25 kHz for each antenna after cleaning using a noise bin frequency of 27.5 kHz.

[0066] Dashed lines 408 represent the sensed signal components for each antenna at a 25kHz operating frequency after processing using only CNR. As an example of how CNR cleaning can produce erroneous results, region 410 in the CNR plot (dashed lines 408) exhibits a steep downward slope from high to low amplitude, which could be interpreted by the I / O controller as an active stylus signal from one side of the touch screen. In contrast, sensed signals cleaned using orthogonal frequencies do not exhibit this erroneous behavior. In summary, in the described technique, one or more noise bin frequencies are used to remove frequency-based noise from the sensed signal in the digitizer.

[0067] Figure 5 An example of a computing device 500 for implementing the described techniques is shown. The computing device 500 can be a client computing device (e.g., a laptop, desktop, or tablet), a server / cloud computing device, an Internet of Things (IoT), any other type of computing device, or a combination of these options. The computing device 500 includes one or more processors 502 and memory 504. The memory 504 typically includes volatile memory (e.g., RAM) and non-volatile memory (e.g., flash memory), although one type of memory may be omitted. An operating system 510 resides in the memory 504 and is executed by the processor 502. In some embodiments, the computing device 500 includes memory 520 and / or is communicatively coupled to the memory 520.

[0068] exist Figure 5In the illustrated example computing device 500, one or more modules or segments (e.g., application 550, noise remover, signal sampler, frequency selector, noise cleaner, I / O controller, and other program code and modules) are loaded into memory 504 and / or operating system 510 on memory 520 and executed by a processor. Memory 520 can store sampled sense signals, DFT values, ratio values, one or more noise cleaning conditions (including potential upper and lower ratio limits), SQUARE_SUMMED_VALUE_RATIO, and other data, and can be located locally on the computing device 500 or remotely located and communicatively coupled to the computing device 500. In particular, in one embodiment, components of a system for managing RF noise in a digitizer to detect active stylus signals operating within a defined bandwidth can be implemented entirely in hardware or a combination of hardware circuitry and software.

[0069] Computing device 500 includes a power supply 516, which may include or be connected to one or more batteries or other power sources and provide power to other components of computing device 500. Power supply 516 may also be connected to an external power source, which may override or recharge the internal batteries or other power sources.

[0070] The computing device 500 may include one or more communication transceivers 530 that may be connected to one or more antennas 532 to provide network connectivity (e.g., mobile phone networks, ) to one or more other servers, client devices, IoT devices, and other computing and communication devices. The computing device 500 may further include a communication interface 536 (e.g., a network adapter or I / O port, which are types of communication devices). The computing device 500 can use adapters and other types of communication devices to establish a connection through a wide area network (WAN) or a local area network (LAN). It should be noted that the network connection shown is exemplary, and in actual applications, other communication devices and means of establishing communication links can be used to achieve connections between the computing device 500 and other devices.

[0071] The computing device 500 may include one or more input devices 534 so that a user can enter commands and information (e.g., a keyboard, a touchpad, or a mouse). These and other input devices may be connected to the server via one or more interfaces 538 (e.g., a serial port interface, a parallel port, or a universal serial bus (USB)). The computing device 500 may also include a display 522, such as a touch screen display.

[0072] The computing device 500 may include various tangible processor-readable storage media and intangible processor-readable communication signals. Tangible processor-readable storage media can be any available media that the computing device 500 can access, and can include volatile and non-volatile storage media as well as removable and non-removable storage media. Tangible processor-readable storage media does not include intangible communication signals (e.g., the signals themselves) and includes volatile and non-volatile, removable and non-removable storage media implemented in any method or technology for storing information, such as processor-readable instructions, data structures, program modules, or other data. Tangible processor-readable storage media include, but are not limited to, RAM, ROM, EEPROM, flash memory or other storage technology, CDROM, digital versatile discs (DVD) or other optical disk storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other tangible medium that can be used to store the desired information and can be accessed by the computing device 500. Unlike tangible processor-readable storage media, intangible processor-readable communication signals can embody processor-readable instructions, data structures, program modules, or other data residing in a modulated data signal (such as a carrier wave or other signal transmission mechanism). The term "modulated data signal" means a signal that has one or more of its characteristics set or changed in such a manner as to encode information in the signal. Examples of intangible communication signals include, but are not limited to, signals transmitted over wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, RF, infrared, and other wireless media.

[0073] Item 1. A method for managing radio frequency noise in a digitizer to detect an active stylus signal having an operating frequency within a defined bandwidth, the method comprising: sampling radio frequency signals measured by multiple antennas positioned across the digitizer, wherein the radio frequency signals include a noise component; selecting an orthogonal frequency outside the defined bandwidth of the operating frequency; and removing at least some of the noise component from the radio frequency signal measured by each antenna based at least on a sensed signal measured by each antenna at the orthogonal frequency.

[0074] Clause 2. A method according to clause 1, wherein the removing comprises removing at least some noise components from the radio frequency signal measured by each antenna based at least on a sensing signal measured by each antenna at an orthogonal frequency and a sensing signal measured by a reference antenna at an orthogonal frequency, wherein the reference antenna does not sense the touch input.

[0075] Clause 3. A method according to clause 1, wherein the removing comprises removing at least some noise components from the radio frequency signal measured for each antenna based at least on a sensing signal measured by each antenna at an orthogonal frequency, a sensing signal measured by a reference antenna at an orthogonal frequency, and a sensing signal measured by the reference antenna at an operating frequency.

[0076] Clause 4. The method of clause 1, wherein the removing comprises removing at least some of the noise component from the radio frequency signal measured by each antenna at the operating frequency by subtracting a proportional amplitude of the sensing signal measured by each antenna of the plurality of antennas at the orthogonal frequency, wherein the proportional amplitude is proportional to a ratio of the sensing signal measured by the reference antenna at the operating frequency and the sensing signal measured by the reference antenna at the orthogonal frequency.

[0077] Clause 5. The method of clause 1, wherein selecting comprises selecting an orthogonal frequency for removing at least some noise components based at least on a ratio of a sensed signal measured by the reference antenna at the operating frequency and a sensed signal measured by the reference antenna at the orthogonal frequency.

[0078] Clause 6. A method according to clause 1, wherein the selecting comprises: for each frequency of a plurality of frequencies, determining a ratio of a sensed signal measured by a reference antenna at an operating frequency to a sensed signal measured by the reference antenna at each frequency; and selecting a frequency of the plurality of frequencies whose ratio is closest to 1 as an orthogonal frequency.

[0079] Clause 7. The method of clause 1, wherein the quadrature frequency differs from the operating frequency by at least the inverse of the correlator window duration.

[0080] Clause 8. A method according to clause 1, wherein the selecting comprises: for each frequency of a plurality of frequencies, determining a ratio of a sensing signal measured by a reference antenna at an operating frequency to a sensing signal measured by the reference antenna at each frequency; and excluding from the selection range of orthogonal frequencies each frequency whose ratio does not satisfy a clearing ratio condition.

[0081] Item 9. A system for managing RF noise in a digitizer to detect an active stylus signal having an operating frequency within a defined bandwidth, the system comprising: one or more hardware processors; a signal sampler executable by the one or more hardware processors and configured to sample RF signals measured by multiple antennas positioned across the digitizer, wherein the RF signals include a noise component; a frequency selector executable by the one or more hardware processors and configured to select an orthogonal frequency outside the defined bandwidth of the operating frequency, wherein the orthogonal frequency differs from the operating frequency by at least the inverse of a correlator window duration; and a noise cleaner executable by the one or more hardware processors and configured to remove at least some noise components from the RF signal measured by each antenna based at least on a sensed signal measured by each antenna at the orthogonal frequency.

[0082] Clause 10. The system of clause 9, wherein the noise canceller is further configured to remove at least some noise components from the radio frequency signal measured by each antenna based at least on a sensed signal measured by each antenna at an orthogonal frequency and a sensed signal measured by a reference antenna at an orthogonal frequency.

[0083] Clause 11. A system according to clause 9, wherein the noise remover is further configured to remove at least some noise components from the radio frequency signal measured by each antenna based at least on a sensing signal measured by each antenna at an orthogonal frequency, a sensing signal measured by a reference antenna at an orthogonal frequency, and a sensing signal measured by the reference antenna at an operating frequency, wherein the reference antenna does not sense touch input.

[0084] Clause 12. The system of clause 9, wherein the noise remover is further configured to remove at least some noise components from the radio frequency signal measured by each antenna at the operating frequency by subtracting a proportional amplitude of the sensed signal measured by each antenna of the plurality of antennas at the orthogonal frequency, wherein the proportional amplitude is proportional to a ratio of the sensed signal measured by the reference antenna at the operating frequency and the sensed signal measured by the reference antenna at the orthogonal frequency.

[0085] Clause 13. The system of clause 9, wherein the frequency selector is further configured to select an orthogonal frequency for removing at least some noise components based at least on a ratio of a sensed signal measured by the reference antenna at the operating frequency and a sensed signal measured by the reference antenna at the orthogonal frequency.

[0086] Clause 14. A system according to clause 9, wherein the frequency selector is further configured to determine, for each frequency in a plurality of frequencies, a ratio of a sensing signal measured by the reference antenna at the operating frequency to a sensing signal measured by the reference antenna at each frequency, and select the frequency in the plurality of frequencies whose ratio is closest to 1 as the orthogonal frequency.

[0087] Item 15. One or more tangible, processor-readable storage media carrying instructions for executing, on one or more processors and circuits of a computing device, a process for managing radio frequency noise in a digitizer to detect an active stylus signal having an operating frequency within a defined bandwidth, the process comprising: sampling radio frequency signals measured by a plurality of antennas positioned across the digitizer, wherein the radio frequency signals include a noise component; selecting an orthogonal frequency outside the defined bandwidth of the operating frequency; and removing at least some of the noise component from the radio frequency signal measured by each antenna based at least on a sensed signal measured by each antenna at the orthogonal frequency and a sensed signal measured by a reference antenna at the orthogonal frequency.

[0088] Clause 16. A tangible, processor-readable storage medium as described in clause 15, wherein the removing comprises: removing at least some noise components from the radio frequency signal measured for each antenna based at least on a sensing signal measured by each antenna at an orthogonal frequency, a sensing signal measured by the reference antenna at an orthogonal frequency, and a sensing signal measured by the reference antenna at an operating frequency.

[0089] Clause 17. A tangible, processor-readable storage medium as described in clause 15, wherein the removing comprises: removing at least some noise components from the radio frequency signal measured by each antenna at the operating frequency by subtracting a proportional amplitude of the sensing signal measured by each antenna of the plurality of antennas at the orthogonal frequency, wherein the proportional amplitude is proportional to a ratio of the sensing signal measured by the reference antenna at the operating frequency and the sensing signal measured by the reference antenna at the orthogonal frequency.

[0090] Clause 18. A tangible, processor-readable storage medium as described in clause 15, wherein the selecting includes: selecting an orthogonal frequency for removing at least some noise components based at least on a ratio of a sensing signal measured by the reference antenna at the operating frequency and a sensing signal measured by the reference antenna at an orthogonal frequency, wherein the reference antenna is not sensing touch input.

[0091] Clause 19. A tangible, processor-readable storage medium according to clause 15, wherein the selecting comprises: for each frequency of a plurality of frequencies, determining a ratio of a sensed signal measured by the reference antenna at the operating frequency to a sensed signal measured by the reference antenna at each frequency; and selecting the frequency of the plurality of frequencies whose ratio is closest to 1 as the orthogonal frequency.

[0092] Clause 20. The tangible, processor-readable storage medium of clause 15, wherein the quadrature frequency differs from the operating frequency by at least an inverse of a correlator window duration.

[0093] Item 21. A system for managing RF noise in a digitizer to detect active stylus signals having an operating frequency within a defined bandwidth, the system comprising: means for sampling RF signals measured by multiple antennas positioned across the digitizer, wherein the RF signals include noise components; means for selecting orthogonal frequencies outside the defined bandwidth of the operating frequency; and means for removing at least some of the noise components from the RF signals measured by each antenna based at least on a sensed signal measured by each antenna at the orthogonal frequencies.

[0094] Clause 22. The system of clause 21, wherein the means for removing comprises means for removing at least some noise components from the radio frequency signal measured by each antenna based at least on a sensed signal measured by each antenna at an orthogonal frequency and a sensed signal measured by a reference antenna at an orthogonal frequency.

[0095] Clause 23. A system according to clause 21, wherein the means for removing comprises means for removing at least some noise components from the radio frequency signal measured for each antenna based at least on a sensing signal measured by each antenna at an orthogonal frequency, a sensing signal measured by a reference antenna at an orthogonal frequency, and a sensing signal measured by the reference antenna at an operating frequency.

[0096] Clause 24. A system according to clause 21, wherein the means for removing comprises: removing at least some noise components from the radio frequency signal measured by each antenna at the operating frequency by subtracting a proportional amplitude of the sensing signal measured by each antenna of the plurality of antennas at the orthogonal frequency, wherein the proportional amplitude is proportional to a ratio of the sensing signal measured by the reference antenna at the operating frequency and the sensing signal measured by the reference antenna at the orthogonal frequency.

[0097] Clause 25. The system of clause 21, wherein the means for selecting comprises selecting an orthogonal frequency for removing at least some noise components based at least on a ratio of a sensed signal measured by the reference antenna at the operating frequency and a sensed signal measured by the reference antenna at the orthogonal frequency.

[0098] Clause 26. A system according to clause 21, wherein the means for selecting includes: for each frequency of a plurality of frequencies, means for determining a ratio of a sensed signal measured by a reference antenna at an operating frequency to a sensed signal measured by a reference antenna at each frequency; and means for selecting a frequency of the plurality of frequencies whose ratio is closest to 1 as an orthogonal frequency.

[0099] Clause 27. The system of clause 21, wherein the quadrature frequency differs from the operating frequency by at least the inverse of the correlator window duration.

[0100] Clause 28. A system according to clause 21, wherein the means for selecting includes: for each frequency of a plurality of frequencies, a means for determining a ratio of a sensing signal measured by a reference antenna at an operating frequency to a sensing signal measured by the reference antenna at each frequency; and a means for excluding from the selection range of orthogonal frequencies each frequency whose ratio does not satisfy a clearing ratio condition.

[0101] Some embodiments may include an article of manufacture, but not the software itself. An article of manufacture may include a tangible storage medium for storing logic and / or data. Examples of storage media may include one or more computer-readable storage media capable of storing electronic data, including volatile or non-volatile memory, removable or non-removable memory, erasable or non-erasable memory, writable or rewritable memory, etc. Examples of logic may include various software elements, such as software components, programs, applications, computer programs, application programs, system programs, machine programs, operating system software, middleware, firmware, software modules, routines, subroutines, operating segments, methods, programs, software interfaces, application program interfaces (APIs), instruction sets, computing code, computer code, code segments, computer code segments, words, values, symbols, or any combination thereof. For example, in one embodiment, an article of manufacture may store executable computer program instructions that, when executed by a computer, cause the computer to perform methods and / or operations in accordance with an embodiment. Executable computer program instructions may include any suitable code type, such as source code, compiled code, interpreted code, executable code, static code, dynamic code, etc. Executable computer program instructions can be implemented according to a predefined computer language, method or syntax to instruct the computer to perform a specific operation segment. The instructions can be implemented using any suitable high-level, low-level, object-oriented, visual, compiled and / or interpreted programming language.

[0102] The embodiments herein are implemented as logical steps in one or more computer systems. Logical operations can be implemented (1) as a sequence of processor-implemented steps executed in one or more computer systems, or (2) as interconnected machine or circuit modules in one or more computer systems. The choice of embodiment depends on the performance requirements of the computer system used. Therefore, the logical operations that constitute the embodiments of this specification are referred to as operations, steps, objects, or modules. In addition, it should be understood that unless expressly required otherwise, or the claim language inherently requires a specific order, the logical operations can be performed in any order.

Claims

1. A method (300) of managing radio frequency noise in a digitizer (104) to detect an active stylus signal (202) having an operating frequency (204) within a defined bandwidth, the method (300) comprising: sampling (302) radio frequency signals measured by a plurality of antennas positioned across the digitizer (104), wherein the radio frequency signals include a noise component; selecting (304) an orthogonal frequency (204) outside the defined bandwidth of the operating frequency (204); as well as At least some of the noise components are removed (306) from the radio frequency signal measured by each antenna based at least on the sensed signal measured by each antenna at the orthogonal frequency (204).

2. The method according to claim 1, wherein the removing comprises: At least some of the noise components are removed from the radio frequency signal measured by each antenna based at least on the sensing signal measured by each antenna at the orthogonal frequency and the sensing signal measured by a reference antenna at the orthogonal frequency, wherein the reference antenna is not sensing touch input.

3. The method according to claim 1, wherein the removing comprises: At least some of the noise components are removed from the radio frequency signal for each antenna based at least on the sensing signal measured by each antenna at the orthogonal frequency, the sensing signal measured at the orthogonal frequency at the reference antenna, and the sensing signal measured at the operating frequency at the reference antenna.

4. The method according to claim 1, wherein the removing comprises: At least some of the noise components are removed from the radio frequency signal measured by each of the plurality of antennas at the operating frequency by subtracting a proportional amplitude of the sensing signal measured by each antenna at the orthogonal frequency, wherein the proportional amplitude is proportional to a ratio of the sensing signal measured by a reference antenna at the operating frequency and the sensing signal measured by the reference antenna at the orthogonal frequency.

5. The method according to claim 1, wherein the selecting comprises: The orthogonal frequency for removing at least some of the noise components is selected based at least on a ratio of a sensed signal measured by a reference antenna at the operating frequency and a sensed signal measured by the reference antenna at the orthogonal frequency.

6. The method according to claim 1, wherein the selecting comprises: determining, for each frequency of a plurality of frequencies, a ratio of a sensed signal measured by a reference antenna at the operating frequency and a sensed signal measured by the reference antenna at each of the frequencies; as well as The frequency with the ratio closest to 1 among the multiple frequencies is selected as the orthogonal frequency.

7. The method of claim 1, wherein the orthogonal frequency differs from the operating frequency by at least the inverse of a correlator window duration.

8. The method of claim 1 , wherein the selecting comprises: determining, for each frequency of a plurality of frequencies, a ratio of a sensed signal measured by a reference antenna at the operating frequency and a sensed signal measured by the reference antenna at each of the frequencies; as well as Each frequency whose ratio does not satisfy the clearing ratio condition is excluded from the selection range of the orthogonal frequencies.

9. A system (106) for managing radio frequency noise in a digitizer (104) to detect an active stylus signal (202) having an operating frequency (204) within a defined bandwidth, the system (106) comprising: one or more hardware processors (502); a signal sampler (120), executable by the one or more hardware processors (502), and configured to sample (302) radio frequency signals measured by a plurality of antennas positioned across the digitizer (104), wherein the radio frequency signals include a noise component; a frequency (204) selector (122), executable by the one or more hardware processors (502), and configured to select (304) an orthogonal frequency (204) outside the defined bandwidth of the operating frequency (204), wherein the orthogonal frequency (204) differs from the operating frequency (204) by at least an inverse of a correlator window duration; as well as A noise cleaner (124), executable by the one or more hardware processors (502), is configured to remove (306) at least some of the noise components from the radio frequency signal measured by each antenna based at least on a sensed signal measured by each antenna at the orthogonal frequency (204).

10. The system of claim 9, wherein the noise remover is further configured to remove at least some of the noise components from the RF signal measured by each antenna based at least on the sensed signal measured by each antenna at the orthogonal frequency and the sensed signal measured by a reference antenna at the orthogonal frequency.

11. The system of claim 9 , wherein the noise remover is further configured to remove at least some of the noise components from the RF signal for each antenna based at least on the sensing signal measured by each antenna at the orthogonal frequency, the sensing signal measured by a reference antenna at the orthogonal frequency, and the sensing signal measured by the reference antenna at the operating frequency, wherein the reference antenna is not sensing touch input.

12. The system of claim 9 , wherein the noise remover is further configured to remove at least some of the noise components from the radio frequency signal measured by each of the plurality of antennas at the operating frequency by subtracting a proportional amplitude of the sensing signal measured by each antenna at the orthogonal frequency, wherein the proportional amplitude is proportional to a ratio of the sensing signal measured by a reference antenna at the operating frequency and the sensing signal measured by the reference antenna at the orthogonal frequency.

13. The system of claim 9 , wherein the frequency selector is further configured to select the orthogonal frequency for removing at least some of the noise components based at least on a ratio of a sensed signal measured by a reference antenna at the operating frequency and a sensed signal measured by the reference antenna at the orthogonal frequency.

14. The system of claim 9 , wherein the frequency selector is further configured to: determine, for each frequency among a plurality of frequencies, a ratio of a sensing signal measured by a reference antenna at the operating frequency and a sensing signal measured by the reference antenna at each of the frequencies, and select a frequency among the plurality of frequencies whose ratio is closest to 1 as the orthogonal frequency.

15. One or more tangible processor-readable storage (520) media carrying instructions for executing, on one or more processors (502) and circuits of a computing device (500), a process (300) for managing radio frequency noise in a digitizer (104) to detect an active stylus signal (202) having an operating frequency (204) within a defined bandwidth, the process (300) comprising: sampling (302) radio frequency signals measured by a plurality of antennas positioned across the digitizer (104), wherein the radio frequency signals include a noise component; selecting (304) an orthogonal frequency (204) outside the defined bandwidth of the operating frequency (204); as well as At least some of the noise components are removed (306) from the radio frequency signal measured by each antenna based at least on a sensed signal measured by each antenna at the orthogonal frequency (204) and a sensed signal measured by a reference antenna at the orthogonal frequency (204).

16. The tangible processor-readable storage medium of claim 15, wherein the removing comprises: At least some of the noise components are removed from the radio frequency signal measured for each antenna based at least on the sensing signal measured by each antenna at the orthogonal frequency, the sensing signal measured by the reference antenna at the orthogonal frequency, and the sensing signal measured by the reference antenna at the operating frequency.

17. The tangible processor-readable storage medium of claim 15, wherein the removing comprises: At least some of the noise components are removed from the radio frequency signal measured by each of the plurality of antennas at the operating frequency by subtracting a proportional amplitude of the sensing signal measured by each antenna at the orthogonal frequency, wherein the proportional amplitude is proportional to a ratio of the sensing signal measured by a reference antenna at the operating frequency and the sensing signal measured by the reference antenna at the orthogonal frequency.

18. The tangible, processor-readable storage medium of claim 15, wherein the selecting comprises: The orthogonal frequency is selected for removing at least some of the noise components based at least on a ratio of a sensed signal measured by a reference antenna at the operating frequency and a sensed signal measured by the reference antenna at the orthogonal frequency, wherein the reference antenna is not sensing touch input.

19. The tangible processor-readable storage medium of claim 15, wherein the selecting comprises: determining, for each frequency of a plurality of frequencies, a ratio of a sensed signal measured by a reference antenna at the operating frequency and a sensed signal measured by the reference antenna at each of the frequencies; as well as The frequency with the ratio closest to 1 among the multiple frequencies is selected as the orthogonal frequency.

20. The tangible processor-readable storage medium of claim 15, wherein the orthogonal frequency differs from the operating frequency by at least an inverse of a correlator window duration.

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