Method and system for determining a noise-robust acquisition configuration for the operation of a sensor system

Abstract

Systems and methods for determining a noise-robust acquisition configuration for a sensor or communication system are disclosed. An exemplary method comprises: acquiring a sensor received signal from a sensor system; determining a digital received signal from the sensor received signal by A / D conversion of the sensor received signal at a predefined noise scan frequency; determining a plurality of decimated digital received signals by integer decimation of the digital received signal using two or more different decimation rates, each of the two or more decimation rates being associated with its own candidate acquisition configuration; determining one or more noise indices for a plurality of candidate acquisition configurations using one or more of the plurality of decimated digital received signals; and determining an acquisition configuration for the operation of the sensor system from the candidate acquisition configurations using one or more noise indices.

Description

Technology Field

[0001] Cross-reference of related applications

[0002] This application claims priority to U.S. Provisional Patent Application No. 63 / 126,137 filed with the U.S. Patent and Trademark Office on December 16, 2020. The contents of the aforementioned patent application are incorporated herein by reference for all purposes.

[0003] Technology field

[0004] The present disclosure relates to methods and systems for determining a noise-robust acquisition configuration, particularly for sensor systems. Background Technology

[0005] This background section is provided for the purpose of providing an overview of the context of the present disclosure. The results of the inventor(s) mentioned herein, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are not recognized as prior art to the present disclosure, either expressly or impliedly.

[0006] Sensor systems, sometimes also referred to as 'sensing systems,' are known for various applications. For example, capacitive touch sensor systems are used in user interfaces of electronic devices such as computers, tablets, smartphones, and other electronic devices.

[0007] Capacitive touch sensor systems can be realized, for example, by generating an alternating electric field and measuring the potential difference (i.e., voltage) obtained in one cycle at a sensor electrode within this electric field. A single electrode, or a combination of a transmitting electrode and one or more receiving electrodes, may be used. This voltage is a measure of the capacitance between the sensor electrode and its electrical environment, that is, it is affected by objects such as a person's finger or hand. Alternatively, the current flowing between the electrode and the sensor circuit (i.e., the movement of electric charges) can be used to determine the capacitance between the sensor electrode and its electrical environment.

[0008] A problem with conventional systems operating according to the aforementioned principles is that electrical noise sources, such as switching-mode power supplies, fluorescent lamps, or wireless communication located near the sensor, can affect the electric field. Consequently, accurately and reliably estimating these voltages in noisy environments becomes a problem.

[0009] As determined by the inventors, robustness against noise is a challenge for any sensor system, including capacitive touch sensing systems, and also for communication systems. In particular, passing standard IEC noise tests using amplitude modulation noise, such as in IEC 61000-4-6, bulk current injection (BCI) tests according to the ISO 11452-4 automotive standard, or robustness against square noise has been a problem in the past.

[0010] Based on the above, there is a need to allow for noise-robust operation of sensor systems, such as, for example, capacitive touch sensor systems. This objective is addressed by the subject of the independent claims. The dependent claims and the following description include various embodiments of the present invention.

[0011] Generally and in one exemplary aspect, a method is provided for determining a noise-robust acquisition configuration for the operation of a sensor system. The method includes the following steps in a noise scan:

[0012] A step of acquiring a sensor reception signal from a sensor system;

[0013] A step of determining a digital received signal from a sensor received signal by A / D conversion of the sensor received signal at a predefined noise scan frequency;

[0014] A step of determining a plurality of decimated digital received signals by integer decimation of a digital received signal using two or more different decimation rates - each of the two or more decimation rates is associated with its own candidate acquisition configuration -;

[0015] A step of determining one or more noise indices for a plurality of candidate acquisition configurations using one or more of a plurality of decimated digital reception signals; and

[0016] A step of determining an acquisition configuration for the operation of a sensor system from candidate acquisition configurations using one or more noise indices.

[0017] Generally and in other exemplary cases, a sensor circuit is provided for determining an acquisition configuration for the operation of a sensor system, and the sensor circuit is,

[0018] Sensor interface for acquiring a sensor reception signal from a sensor system;

[0019] An A / D converter for determining a digital received signal from a sensor received signal by A / D conversion of the sensor received signal at a predefined noise scan frequency;

[0020] A decimation circuit configured to determine multiple decimated digital received signals by integer decimation of a digital received signal using two or more different decimation rates - each of the two or more decimation rates is associated with its own candidate acquisition configuration -;

[0021] A noise evaluation circuit configured to determine one or more noise indices for a plurality of acquisition configurations using one or more of a plurality of decimated digital received signals; and

[0022] It includes a configuration circuit configured to determine an acquisition configuration for the operation of a sensor system from candidate acquisition configurations using one or more noise indicators.

[0023] Generally and in other exemplary cases, a capacitive touch sensing system is provided, and the capacitive touch sensing system is,

[0024] One or more electrodes configured for capacitive sensing; and

[0025] The sensor circuit of the previous sun - the sensor circuit is connected to at least one of one or more electrodes - includes.

[0026] In general and in other exemplary embodiments, a method is provided for determining a noise-robust acquisition configuration for the operation of a communication system. The method includes the following steps in a noise scan:

[0027] A step of acquiring a received signal from a communication system;

[0028] A step of determining a digital received signal from a received signal by A / D conversion of the received signal at a predefined noise scan frequency;

[0029] A step of determining a plurality of decimated digital received signals by integer decimation of a digital received signal using two or more different decimation rates - each of the two or more decimation rates is associated with its own candidate acquisition configuration -;

[0030] A step of determining one or more noise indices for a plurality of acquisition configurations using one or more of a plurality of decimated digital reception signals; and

[0031] A step of determining an acquisition configuration for the operation of a communication system from candidate acquisition configurations using one or more noise indices.

[0032] In general and in other exemplary embodiments, a communication circuit is provided for determining an acquisition configuration for the operation of a communication system. The communication circuit is,

[0033] A communication system interface for acquiring a received signal from a communication system;

[0034] An A / D converter for determining a digital received signal from a received signal by A / D conversion of the received signal at a predefined noise scan frequency;

[0035] A decimation circuit configured to determine multiple decimated digital received signals by integer decimation of a digital received signal using two or more different decimation rates - each of the two or more decimation rates is associated with its own acquisition configuration -;

[0036] A noise evaluation circuit configured to determine one or more noise indices for a plurality of acquisition configurations using one or more of a plurality of decimated digital received signals; and

[0037] It includes a configuration circuit configured to determine an acquisition configuration for the operation of a communication system from candidate acquisition configurations using one or more noise indicators.

[0038] Details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description, drawings, and claims. Brief explanation of the drawing

[0039] FIG. 1 illustrates a first exemplary embodiment of a sensor circuit in a schematic block diagram. FIG. 2 schematically illustrates an exemplary embodiment of a capacitive touch sensing system. FIG. 3 is an exemplary flowchart according to the first embodiment illustrating the function of the sensor circuit of FIG. 1. Figure 4 schematically illustrates the function of the decimation circuit of the sensor circuit of Figure 1. Figure 5 schematically illustrates two signal processing chains for noise scanning and SN-scan. FIG. 6 is an exemplary flowchart according to a second embodiment illustrating the function of the sensor circuit of FIG. 1. Figure 7 schematically illustrates exemplary magnitudes of the transfer function of an ideal ADC. FIGS. 8a and 8b are exemplary flowcharts according to additional embodiments illustrating the function of the sensor circuit of FIG. 1. Figure 9 illustrates spectral noise suppression by a digital LPF. FIG. 10 is an exemplary flowchart according to another embodiment illustrating the function of the sensor circuit of FIG. 1. FIG. 11 illustrates a basic exemplary diagram and corresponding timing diagram for measuring charge using current integration. FIG. 12 illustrates another exemplary diagram for charge measurement using two current integrators, along with a corresponding timing diagram. FIG. 13 schematically illustrates two slices of an exemplary analog front-end (AFE) of a touchscreen controller. FIG. 14 illustrates an exemplary timing diagram for a current integrator and integrator reset having slice-independent control of aperture and reset switches. FIG. 15 illustrates an exemplary timing diagram for a current integrator and integrator reset that does not have slice-independent control of the aperture and reset switches. Figure 16 illustrates data obtained using the timing configuration of Figure 15. Figure 17 illustrates spectral noise suppression by a digital LPF for a packet length of 2. Specific details for implementing the invention

[0040] Below, specific embodiments of the present invention are now described in detail. In the following description of the embodiments of the present invention, specific details are described to provide a complete understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without such specific details. In other cases, well-known features have not been described in detail to avoid unnecessarily complicating this description.

[0041] In the following description of the invention according to the described embodiments, the terms “connected to” or “connected with” are used to denote a data or signal connection between at least two components, devices, units, processors, circuits, or modules. Such a connection may be direct between each of the components, devices, units, processors, circuits, or modules; or indirect, that is, through intermediate components, devices, units, processors, circuits, or modules. The connection may be permanent or temporary; wireless or conductor-based; digital or analog.

[0042] In the following description, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives for elements (i.e., any noun in this application). The use of ordinal numbers does not imply or create any particular ordering of elements, nor does it limit any element to a single element unless explicitly disclosed by, for example, the use of terms “before,” “after,” “single,” and other such terms. Rather, the use of ordinal numbers is intended to distinguish elements of similar names. For example, the first element is distinct from the second element, and the first element may include more than one element and follow (or precede) the second element in the ordering of elements.

[0043] Sensor systems are used in many applications. For example, today's electronic devices, such as smartphones, laptops, tablets, and wearables, would be unimaginable without touchscreens, which generally utilize capacitive or resistive touch sensor systems. Current developments are increasing the use of touchscreens in more complex systems, such as automobiles, airplanes, or industrial equipment.

[0044] As mentioned above, robustness against noise is a key challenge for any such sensor system. A specific problem with capacitive touchscreens is that, by design, they need to be configured so that the electric field used can be affected when facing a user, for example, when the user's hand or finger is in close proximity. This makes this type of touchscreen particularly vulnerable to noise from ambient electric fields.

[0045] Furthermore, as recognized by the inventors, there is no reliable means to determine the expected signal-to-noise ratio (also referred to as 'SNR' below) for a given sensor and configuration, which leads to an insufficient output SNR or a waste of resources, for example, acquisition time. For customers of a touch sensing system (e.g., smartphone manufacturers), it is important to produce a high touch reporting rate with reliable and accurate output estimates. Accordingly, the touch reporting rate refers to the rate at which the touch controller forwards, for example, (x, y) position estimates to a host controller.

[0046] There are several influencing factors affecting the noise robustness of the sensor system, such as the operating frequency with its associated sampling frequency for A / D conversion (the operating frequency of the so-called 'stimulus signal' in the case of a capacitive sensor system), the scan duration, and one or more of the selection of low-pass filter coefficients. In the context of this discussion, the set of configurable parameters of the sensor system affecting these influencing factors is understood as the 'acquisition configuration' or 'data acquisition configuration' of the sensor system (also referred to as 'AC' below for brevity). In some embodiments, the acquisition configuration includes at least one of the following parameters: the sampling frequency for A / D conversion, the operating frequency of the stimulus signal for the (acquisition) operation of the sensor system (carrier frequency), the scan duration, the number of samples to be acquired, the 'packet length', and the low-pass filter coefficients. Different ACs differ in one or more of these parameters. The parameters can be used to configure the digital processing of the sensor control circuit as well as the 'analog front-end'.

[0047] The received signal of a communication or sensing system is typically a mixture of noise and actual information that needs to be received and evaluated. This information could be, for example, a measure of the capacitance or distance between a sensor electrode and a user's finger. In the case of additive noise, the received signal is simply the sum of information and noise. Since typically both the information and noise parts are unknown, the information part cannot be easily extracted from the received signal—this is analogous to a single equation with two unknowns that is inherently unsolvable. However, given a noisy received signal, it is possible to estimate the information part by making assumptions about the characteristics of the information, noise, or both, for example, that 'information changes slowly over time.' The less noise there is, the more accurate the resulting estimate is; that is, the less uncertainty there is in the estimate. Accordingly, one would want to use an acquisition configuration with almost no noise, for example, one that exhibits less noise in the resulting estimate compared to other acquisition configurations.

[0048] It is possible to perform test measurements using a sensor system and, from this measurement data, calculate a noise index indicating the amount of noise. Such test measurements are referred to as 'noise scandals' in this context.

[0049] Noise scans may be performed on different candidate ACs, and once their respective noise is determined, the AC that yields the lowest amount of noise may be selected. Measurements in which the received signal contains both the desired information and noise will be referred to as signal and noise scans or 'SN-scans'. During an SN-scan, the sensor or communication system may need to generate and emit an excitation signal to excite an alternating electric field and yield the information portion at the receiving end. From the data acquired during the noise scan, estimates of the expected amount of noise during the SN-scan for predefined candidate ACs may be calculated. Here, such estimates are referred to as 'noise estimates'. The ACs for which noise estimates are calculated from noise scan data acquired during a single noise scan may differ in their operating frequency and sampling frequency, which are considered at least as parameters of the analog front-end of the sensor system.

[0050] In this context, 'stimulation signal' or simply 'stimulation' is understood as the actively controlled movement of charges between a sensor circuit, e.g., a chip and an electrode, to drive the potential of an electrode to a given target value or target signal. In some embodiments, such target value or target signal is specified before stimulation is initiated; for example, when the target signal is a rectangular pulse train having a given pulse frequency, such pulse frequency is selected before driving the potential of the electrode to such target signal.

[0051] In some embodiments, the stimulus may be a periodic signal, e.g., a rectangular pulse train. The frequency of this periodic signal, e.g., the pulse frequency, is the operating frequency discussed above, also referred to as the 'carrier frequency'. In some embodiments, the stimulus signal alternately stabilizes at a higher signal level and a lower signal level, respectively, during the carrier signal cycle. At the receiving end, the received signal may be demodulated and low-pass filtered—both of which may be performed in the digital domain after analog-to-digital (A / D) conversion. When the stimulus is a rectangular pulse train, sampling may be performed at twice the carrier frequency in some embodiments. In some embodiments, demodulation may be performed by alternately multiplying the A / D converted samples by plus 1 and minus 1.

[0052] Based on the above, the need addressed by the embodiments of the present invention is, for example, to select a suitable AC from a set of candidate ACs to achieve a high touch reporting rate with reliable and accurate output estimates.

[0053] The basic exemplary ideas of the present invention include a) the idea of ​​fundamental and sub-frequencies that enable the same sequence of noise scan measurement data to be processed in different ways, more precisely with different parameters, in order to yield reliable noise (power) estimates for a number of ACs (e.g., for carrier frequencies and scan times), and b) a robust noise indicator that provides an accurate estimate of the true noise power of the SN-scan measurement data after demodulation and low-pass filtering.

[0054] According to the first exemplary embodiment, a method for determining a noise-robust acquisition configuration for the operation of a sensor system, in a noise scan,

[0055] A step of acquiring a sensor reception signal from a sensor system;

[0056] A step of determining a digital received signal from a sensor received signal by A / D conversion of the sensor received signal at a predefined noise scan frequency;

[0057] A step of determining a plurality of decimated digital received signals by integer decimation of the digital received signals using two or more different decimation rates - the two or more decimation rates are associated with their respective candidate acquisition configurations -;

[0058] A step of determining one or more noise indices for a plurality of candidate acquisition configurations using one or more of a plurality of decimated digital reception signals; and

[0059] It includes the step of determining an acquisition configuration for the operation of a sensor system from candidate acquisition configurations using one or more noise indices.

[0060] The sensor system of the present solar system may be of any suitable type, including, without limitation, sensor systems that detect and measure proximity, pressure, position, displacement, force, humidity, fluid level, and acceleration. For example, the sensor system may be an infrared sensor system or an ultrasonic sensor system. For example, the sensor system may be a capacitive or resistive touch sensor system, for example, for a touchscreen display. For example, the sensor system may be a touchless sensor system.

[0061] In some embodiments, the method of the present embodiment is performed using a sensor circuit comprising a control unit, such as a microcontroller and / or microprocessor having suitable programming. Alternatively or additionally, the sensor circuit may include a dedicated circuit portion that provides at least some of the functions of the method of the exemplary embodiment.

[0062] As discussed above, the noise scan of the present invention can be considered, for example, as a test measurement to determine the effects of noise on each sensor system. In some embodiments, the measurement data acquired during the noise scan contains no information and contains only noise, that is, the sensor reception signal during the noise scan is acquired without any stimulus signal being applied to the sensor system.

[0063] The (sensor) received signal (i.e., the signal received, measured, or acquired during a noise scan or SN-scan) may be, for example, a current flowing between the electrode and the sensor circuit, i.e., the movement of charges, a current integrated over a predetermined time interval, or the potential or voltage of the electrode relative to a reference potential. The sensor received signal may be acquired from the sensor system by any suitable means, for example, by a corresponding conductive connection.

[0064] These received signals may be affected by stimuli when used, modified by environmental factors such as human fingers, and, in most cases, affected by environmental noise sources. In addition to these environmental or external influencing factors, there may be analog preprocessing within the sensor circuitry that can add additional internal noise to the received signal, such as 1 / f noise from an A / D converter or quantization noise. While robustness against noise from internal sources can typically be addressed during system design, environmental noise sources are not known at least to some extent at the time of design. The methods and systems discussed herein address robustness against external noise. If internal noise is ignored, any change in the received signal—that is, any change in current or potential above—is caused by this external noise of interest.

[0065] According to a first exemplary embodiment, the method comprises the step of determining a digital received signal from a sensor received signal by A / D conversion of the sensor received signal at a predefined noise scan frequency. The A / D conversion may be performed using any suitable method, for example, without limitation, using a flash A / D converter, an integral A / D converter, a successive approximation A / D converter, a sigma-delta A / D converter, a direct-conversion A / D converter, a ramp-comparison A / D converter, a Wilkinson A / D converter, a charge-balancing A / D converter, a dual-gradient A / D converter, a delta-encoded A / D converter, a pipelining A / D converter, a time-interleaved A / D converter, an intermediate FM stage A / D converter, a TS-ADC, or any equivalent. The term "A / D converter" in this specification includes setups of an analog front-end having a suitable A / D converter. The A / D conversion is performed at a predefined noise scan frequency that can be set according to the application. In some embodiments, the noise scan frequency is significantly higher than the operating frequency of the stimulus signal during the operation of the sensor system. In some embodiments, the noise scan frequency may be set to at least three times the operating frequency, such as three to forty times the operating frequency. In some embodiments, the noise scan frequency is set to three to four times the operating frequency.

[0066] In some embodiments, the noise scan frequency, i.e., the sampling rate of the A / D converter during the noise scan, may be significantly higher than the sampling rate of the A / D converter during the SN-scan. Conversely, the sampling interval of the A / D converter may be significantly shorter for the noise scan compared to the SN-scan, as well as the time available for analog processing of the received input signal for the analog-to-digital (A / D) converted samples. As a result, the timing for analog processing required for the SN-scan may not be applicable to the noise scan because there is less time between A / D conversions. Embodiments utilizing a specific ratio of aperture time for the noise scan to aperture time for the SN-scan are discussed below.

[0067] According to the first exemplary embodiment, the method includes the step of determining a plurality of decimated digital reception signals by integer decimation of the digital reception signals using two or more different decimation rates.

[0068] In other words, after the performed A / D conversion, i.e., in the digital domain, the digital received signal at that time is decimated by integer decimation to obtain a plurality of decimated digital received signals. At least two different decimation rates are used, each of which is associated with its respective candidate acquisition configuration. In some embodiments, two or more decimation rates are multiples of 2, such as, for example, 2 and 4. In some embodiments, more than two decimation rates are used.

[0069] Two or more decimation rates are associated with their respective candidate acquisition configurations, for example, by considering the resulting different sampling rates when applying different decimation rates.

[0070] According to the present embodiment, one or more noise indices for a plurality of candidate acquisition configurations are determined using one or more of a plurality of decimated digital received signals. Then, using one or more noise indices, an acquisition configuration for the operation of a sensor system is determined from the candidate acquisition configurations.

[0071] As will be apparent from the above, the method according to the first aspect allows the use of the same measurement data of a sensor reception signal to determine a plurality of decimated digital reception signals. Since two or more decimation rates are used, the plurality of decimated digital reception signals have correspondingly two or more different sampling frequencies. Since the sampling frequency and the associated operating frequency may be part of the acquisition configuration to be tested, i.e., 'candidate ACs', the method discussed accordingly allows testing a plurality of different candidate ACs, for example, using the same measurement data.

[0072] In some embodiments, oversampling is performed during the noise scan. Then, to yield the same aliasing (of the noise) as for the SN-scan, the decimation rate for decimating the noise scan signal may be selected, for example, such that the decimated sampling rate is the same as the SN-scan sampling rate.

[0073] In contrast to other known approaches, the teachings of this specification provide, in at least some embodiments, a complete solution for noise robustness as well as a solution for identifying the relatively best carrier frequency. For example, robustness against AM noise and square noise is provided by determining one or more noise indicators for different ACs from the same measurement data. This method is also inherently rapid and saves measurement time. In some embodiments, the method also allows finding a trade-off between the touch reporting rate and the output SNR.

[0074] As discussed above, the method of the first exemplary sun includes the step of determining one or more noise indices for a number of (two or more) candidate acquisition configurations from one or more of a plurality of decimated digital received signals. The determination of the noise indices may be performed, for example, in the digital domain. In some embodiments, one or more noise indices are determined for each of the candidate acquisition configurations, which allows for the comparison of different candidate ACs. In some embodiments, a noise indices for each decimation rate are calculated from at least one decimated digital received signal associated with each decimation rate. In some embodiments, a noise indices for each decimation rate are calculated from a plurality of decimated digital received signals. Such a method will be discussed in more detail below.

[0075] The noise indicator may be any suitable type for obtaining a similar measure of noise. For example, the noise indicator may be a numeric value that quantifies the noise level present in at least one of a plurality of decimated digital received signals.

[0076] In some embodiments, the noise indicator may be a power scale, such as that obtained by, for example, the Effective Noise Power Estimation (ENPE), but it may also be a quantity calculated from input data using only linear functions, for example, the square root of the power scale or other linear scales, i.e., without limitation. In some embodiments, the noise indicator is a phase-instantaneous noise indicator. There are also approaches in which the noise indicator is a scoring value where a higher score indicates a lower noise level for the SN-scan, for example, as discussed in US10151608 B2 incorporated herein for all purposes.

[0077] In some embodiments, a stimulus is present during the scan for acquiring data to calculate noise indices, i.e., during the noise scan. Although the measurement data acquired during this type of scan is more likely to be affected, for example, by a person's finger near the sensor, it can still be used to yield a sufficiently good decision basis for identifying a suitable AC. With this in mind, the term 'power scale' may be used interchangeably with the term 'noise indices' in some embodiments.

[0078] Once one or more noise indices are determined according to the first exemplary sun, an acquisition configuration for the operation of the sensor system is determined from the given candidate acquisition configurations. This determination is based on one or more noise indices. As will be discussed in more detail below, and in some embodiments, the determination may be influenced by additional considerations, such as, for example, the shortest scan time (also referred to as 'scan duration').

[0079] In some embodiments, the step of determining the acquisition configuration includes selecting a preferred noise indicator from one or more noise indicators, and the acquisition configuration is set to correspond to a candidate acquisition configuration associated with the preferred noise indicator.

[0080] In some embodiments, a preferred noise index is selected based on a predefined criterion, for example, based on a predefined threshold of maximum noise.

[0081] In some embodiments, the preferred noise indicator yields the lowest noise level of one or more noise indicators. That is to say, in these embodiments, the preferred noise indicator may also be referred to as the 'best' noise indicator, and the best noise indicator is understood as a noise indicator having a quantity representing the lowest noise level relative to all other noise indicators within a given comparison set of noise indicators. For example, when the noise indicator is determined by ENPE, the best noise indicator will have the lowest value, and according to the disclosure of US10151608B2, it will have the highest value.

[0082] In some embodiments, for each of two or more decimation rates, corresponding groups of decimated digital received signals (i.e., groups of two or more decimated digital received signals) are determined as part of the determination of a plurality of decimated digital received signals. Accordingly, and considering two or more decimation rates, at least two groups of decimated digital received signals are provided according to the embodiments, and the group 'members' of one group share the same decimation rate.

[0083] In some embodiments, each decimated digital reception signal in a given group is different from all other decimated digital reception signals in a given group. Groups of decimated digital reception signals may differ from one another in any suitable manner. Groups of decimated digital reception signals may have the same or different number of samples.

[0084] In some embodiments and in each group, the decimated digital received signals may differ from one another by having different start phases, at least but without limitation. These embodiments allow for a more improved determination of noise, as will be apparent from the following discussion. The term 'start phase' for digital signals is typically understood as the delay of the first sample of the decimated signal relative to the first sample of the digital received signal in samples at the sampling rate of the received signal. Thus, different start phases for two signals refer to the two signals having different start samples.

[0085] As will be readily apparent, not all possible starting phases need to be represented in a given group of decimated digital received signals. For example, for each of at least two decimation rates R(0,j), a digital received signal x can be decimated for a subset of starting phases v = v0, v0+dv, v0+2dv, ..., R(0,j)-1, where j =0,1,... is indicated as a lower frequency index. In other embodiments, a group of decimated digital received signals represents all possible starting phases. For example, for each of at least two decimation rates R(0,j), the signal x can be decimated for all starting phases v = 0, 1, ..., R(0,j)-1. Thus, in the exemplary case of a digital received signal having 24 samples and a decimation rate of 4 (i.e., R=4), the group will include four corresponding decimated digital received signals, each having 6 samples, and each signal starts at a different starting phase among the total of 4 possible starting phases. Each of the decimated digital received signals in the group contains only every 4th sample, but due to a phase shift of one sample, all samples are still represented in the group, resulting in an improved noise index.

[0086] In some embodiments, one or more noise indices are determined by an effective noise power estimate (ENPE), which includes determining the (e.g., normalized) sum of phase-instantaneous noise indices for each of the decimated digital received signals in one group of groups of decimated digital received signals. In some embodiments, the effective noise power estimate is performed for all groups, that is, for all decimation rates. The determination of the sum of phase-instantaneous noise indices may be performed by any suitable method. In some embodiments, the phase-instantaneous noise indices is the sum of (all) samples of the decimated digital received signal weighted by coefficients from a coefficient vector. For example, the coefficient vector may be a vector containing the coefficients of a low-pass filter. For example, the coefficients of a boxcar window (all 1s) or a Hann (or Hanning) window of a desired length. Normalization of such a sum term may be performed, for example, by dividing such a sum term by the sum of all coefficients in the coefficient vector. This normalization does not need to be performed directly on the weighted sum term, but can also be performed in a later processing stage, for example, after the summation of phase-instantaneous noise indices, which can reduce computational complexity.

[0087] For example, to calculate ENPE for a given decimation rate, for each decimated digital received signal of a given group, the inner product with the assigned coefficient vector is calculated. In some embodiments, these inner products are normalized by dividing by the sum of all coefficients. Then, the average of the squared inner products can be calculated to yield ENPE.

[0088] In some embodiments, the step of determining an acquisition configuration from a set of candidate acquisition configurations includes selecting a candidate acquisition configuration having the shortest scan time while the noise index satisfies a (predefined) noise threshold. These embodiments provide a particularly high touch reporting rate as the shortest possible scan time is utilized.

[0089] Regarding the comparison of noise indices with noise thresholds, it should be noted that this also includes an alternative of comparing the expected output signal-to-noise ratio (SNR) with a (predefined) SNR threshold. The SNR can be calculated from the deductively determined signal power and noise indices discussed above.

[0090] In some embodiments, the step of determining an acquisition configuration from a set of candidate acquisition configurations further comprises comparing one or more noise indicators with a noise threshold; and, if the noise threshold is not satisfied by any of the one or more noise indicators, increasing the scan time of at least one of the candidate acquisition configurations to acquire at least one updated candidate acquisition configuration; determining one or more updated noise indicators for at least one updated candidate acquisition configuration; and comparing one or more updated noise indicators with a noise threshold.

[0091] These embodiments allow for the gradual evaluation of candidate acquisition configurations with increased scan times when none of the original candidate acquisition configurations meet a desired noise threshold, which may be set, for example, according to the respective application. Correspondingly, and in some embodiments, the steps discussed may be repeated until an acquisition configuration meeting the noise threshold is found. In a given iteration, if multiple candidate acquisition configurations meeting the threshold are found, in some embodiments, the candidate acquisition configuration having the lowest noise level during the scan time of a given iteration is selected as the acquisition configuration for system operation. In some embodiments, the scan time of multiple or all candidate acquisition configurations is increased in a given iteration of the preceding steps. This provides multiple updated candidate acquisition configurations that may have the same operation and sampling frequency, but different coefficient vectors.

[0092] In some embodiments, the scan time is increased by a substantially integer multiple of the scan time of the original / previous candidate acquisition configuration. These embodiments are particularly beneficial for reducing noise. In some embodiments, 'substantially integer multiple' is approximately It includes percentage deviations from integer multiples of, where T is the original scan time.

[0093] To increase the scan time, in some embodiments, a new noise scan is performed with a correspondingly increased scan time to obtain at least one updated candidate acquisition configuration.

[0094] In other embodiments, during the step of acquiring a sensor received signal from a sensor system, it is possible to acquire the sensor received signal with a maximum scan time and initially consider only a portion thereof. For example, and in some embodiments, after A / D conversion is performed, while the original sensor received signal is stored, only a portion of the sensor received signal is further processed and forms the basis for the discussed decimation, i.e., the minimum scan time. In these embodiments, it is possible to 'increase' the scan time by subsequently using a longer portion of the stored copy of the original sensor received signal, i.e., by an increased scan time. In some embodiments, the maximum scan time may be four times the minimum scan time.

[0095] In some embodiments, a predefined minimum output reporting rate for the sensor system may be provided, or conversely, a maximum duration for a scan cycle (i.e., a continuous operation of one or more noise scans and SN-scans) in which respective measurement data are acquired may be provided. This time available for the scan cycle is distributed across all individual measurements to be performed during the scan cycle, including auxiliary measurements such as noise scans and at least one SN-scan. Accordingly, for example, for one individual measurement of an SN-scan, a maximum scan time T can be calculated. Sampling frequency , for example, operating frequency or carrier frequency twice of Given, maximum It is possible to fit ADC samples to time T. Therefore, in order to fully utilize this available scan time T, in some embodiments, for a given AC, the number of samples to be acquired and processed, denoted herein as the 'packet length' L, is It is possible to set it to.

[0096] In some embodiments, and where a finite input response (FIR) low-pass filter is used to process the acquired data, the filter length may also be set to L to utilize all of the acquired data, because a single output value for the data acquired during a scan time T may be required while requiring the low-pass filter output to be stable. A vector of low-pass filter coefficients may be selected, for example, in some embodiments to control the spectral suppression of the filter. For example, the first elements of the vector may be positive values ​​smaller than the intermediate elements of the vector. For example, such a vector may be [0.05, 0.1, 0.2, 0.3, 0.2, 0.1, 0.05]. In some embodiments, the vector is symmetric. For example, it is possible to select a Hanning window of length L as the vector of low-pass filter coefficients. As defined by Mathworks, the nth element of the Hanning window is as follows.

[0097]

[0098] In some embodiments, after a noise scan, the method includes the step of operating a sensor system during an SN-scan using an acquisition configuration determined during the noise scan. During the SN-scan, the sensor system may be operated to emit an excitation signal to excite an alternating electric field, and the alternating electric field may subsequently be evaluated for respective sensing applications, such as touch detection.

[0099] In some embodiments, the sensor system is operated during the SN-scan using the acquisition configuration of the most recent noise scan, considering that the acquisition configuration of the most recent scan represents the most recent configuration for the current noise scenario. In some embodiments, after the SN-scan, an additional noise scan is performed. In some embodiments, the resulting cyclic operation may be repeated until the sensing operation of the sensor system is stopped, such as when the sensor system is powered down.

[0100] In some embodiments, the method comprises the step of subsequently performing a number of noise scans between two SN-scans, wherein the number of noise scans utilize predefined noise scan frequencies, and at least some (or, for example, all) of the predefined noise scan frequencies of the number of noise scans are different from one another. These embodiments allow for further improvement in determining a noise-robust acquisition configuration, particularly when candidate acquisition configurations that do not share common multiples need to be evaluated.

[0101] For example, it is possible to determine the overall acquisition configuration for the operation of the sensor system from the acquisition configurations obtained during a number of subsequently performed noise scans. In other words, a 'desirable' or 'best' overall acquisition configuration can be determined from a number of acquisition configurations obtained in each execution of the noise scan. In some embodiments, the overall acquisition configuration can be determined from a group of acquisition configurations determined during the number of noise scans by comparing associated noise indices and / or their respective scan times.

[0102] Alternatively, in some embodiments, it is possible to continuously perform noise scans for, for example, only two (or different numbers) of predefined noise scan frequencies during a scan cycle, while maintaining one candidate noise scan frequency that yields the best AC and looping cyclically over the remaining candidate noise scan frequencies to select a second candidate noise scan frequency.

[0103] In some embodiments, the aperture time of the A / D conversion for determining the acquisition configuration (i.e., during a noise scan) is set to be substantially the same as the aperture time of the SN-scan or an integer fraction of the aperture time of the SN-scan. In other words, the aperture time is predefined for the SN-scan according to the respective application (e.g., in terms of touch reporting rate) or selected as desired, and the aperture time for the A / D conversion during the noise scan is set accordingly, i.e., to be the same as the predefined aperture time or an integer fraction of the predefined aperture time. In the context of the present invention, the term "aperture time" is generally understood as the duration of time during which an analog signal is input to a measurement system, that is, the time during which the measurement system is exposed to the outside world and, consequently, its internal analog state is changed by the analog input signal. In some embodiments, the aperture time relates to the time during which the sensor received signal is input to the sensor interface of the sensor circuit, as discussed below. In some embodiments, the aperture time relates to the time during which the sensor received signal is input to the A / D converter of the sensor circuit, as discussed below.

[0104] When the noise scan aperture time is equal to the SN-scan aperture time, it is possible to ensure that the best carrier frequency determination is obtained. When the noise scan aperture time is an integer fraction of the SN-scan aperture time and the noise is narrowband, it is still possible to obtain the best carrier frequency, even if an absolute effective noise power estimate cannot be provided.

[0105] As confirmed by the inventors, for certain ratios between SN-scan and noise scan aperture times, it is possible to ensure that a relatively positive carrier frequency determination is obtained. This is the case when the noise scan aperture time is a) equal to the SN-scan aperture time, or b) when the noise scan aperture time is an integer fraction of the SN-scan aperture time, or correspondingly, when the SN-scan aperture time is an integer multiple of the noise scan aperture time.

[0106] In some embodiments, (a given fundamental frequency having fundamental frequency index i) Regarding) Duration It is approximately the same for all index pairs (i,j).

[0107] In some embodiments, the method steps are performed at least partially by a sensor circuit for a sensor system. In some embodiments, a (e.g., non-transient) computer-readable medium has content configured to enable the sensor circuit to perform the method steps as described herein.

[0108] According to another aspect, a sensor circuit for determining an acquisition configuration for the operation of a sensor system is provided. The sensor circuit includes, but is not limited to:

[0109] A sensor interface or input for acquiring a sensor reception signal from a sensor system;

[0110] An A / D converter for determining a digital received signal from a sensor received signal by A / D conversion of the sensor received signal at a predefined noise scan frequency;

[0111] A decimation circuit configured to determine multiple decimated digital received signals by integer decimation of a digital received signal using two or more different decimation rates - each of the two or more decimation rates is associated with its own candidate acquisition configuration -;

[0112] A noise evaluation circuit configured to determine one or more noise indices for a number of candidate acquisition configurations using one or more of a plurality of decimated digital received signals; and

[0113] A configuration circuit configured to determine an acquisition configuration for the operation of a sensor system from candidate acquisition configurations using one or more noise indicators.

[0114] In some embodiments, the sensor circuit according to the present aspect is configured according to one or more of the embodiments discussed above with respect to the prior aspect(s). For the terms used and their definitions, the prior aspect(s) are referenced.

[0115] According to another sun, a capacitive touch sensing system (capacitive sensor) is provided. The capacitive touch sensing system of this sun is,

[0116] One or more electrodes configured for capacitive sensing; and

[0117] It includes a sensor circuit connected to at least one of the electrodes; the sensor circuit,

[0118] A sensor interface or input for acquiring a sensor reception signal from one or more electrodes;

[0119] An A / D converter for determining a digital received signal from a sensor received signal by A / D conversion of the sensor received signal at a predefined noise scan frequency;

[0120] A decimation circuit configured to determine multiple decimated digital received signals by integer decimation of a digital received signal using two or more different decimation rates - each of the two or more decimation rates is associated with its own candidate acquisition configuration -;

[0121] A noise evaluation circuit configured to determine one or more noise indices for a number of candidate acquisition configurations using one or more of a plurality of decimated digital received signals; and

[0122] It includes a configuration circuit configured to determine an acquisition configuration for the operation of a sensor system from candidate acquisition configurations using one or more noise indicators.

[0123] In some embodiments, the sensor circuit according to the present aspect is configured according to one or more of the embodiments discussed above with respect to the prior aspect(s). For the terms used and their definitions, the prior aspect(s) are referenced. As used herein, the term "capacitive touch sensing system" is understood to include, for example, touchless sensor systems based on proximity detection.

[0124] Now, numerical designations will be given to various elements of the embodiments, and additional embodiments will be discussed by referring to the drawings.

[0125] In exemplary embodiments, the described components of the embodiments each represent individual features that should be considered independent of one another, in combinations as illustrated or described, and in combinations other than those illustrated or described. Furthermore, the described embodiments may also be complemented by features of the invention other than those described.

[0126] FIG. 1 illustrates a first exemplary embodiment of a sensor circuit (1) in a schematic block diagram. The sensor circuit (1) is adapted to operate a sensor system or a communication system (both not shown in FIG. 1). For example, a sensor (20) of a capacitive touch sensing system (21), schematically illustrated in FIG. 2, may be connected to the sensor circuit (1). For the purposes of this discussion, the capacitive touch sensing system (21) will be referred to, but it is emphasized that the invention is not limited to capacitive touch sensing systems.

[0127] The exemplary sensor circuit (1) of the embodiment of FIG. 1 may be implemented by a microcontroller with hardware / software that provides the following operations and components. For improved clarity, the microcontroller itself is not shown in the schematic block diagram of FIG. 1.

[0128] The sensor circuit (1) includes a sensor interface (2) that can be connected to a sensor (20) of a capacitive touch sensing system (21) using sensor connections (3). Capacitive touch sensing is known for use in capacitive touch screen panels of electronic devices, such as, for example, computers, tablets, smartphones, wearables, and smart home equipment, and electronic components for vehicles, trains, ships, aircraft / spacecraft, and industrial or scientific equipment, without limitation. In one example, the capacitive touch sensing system (21) is a 'touchless' sensor system.

[0129] The sensor interface (2) and sensor connections (3) enable the sensor circuit (1) to operate / drive the sensor (20) of the capacitive touch detection system (21) during an acquisition operation, which is referred to herein as a 'signal and noise scan' or SN-scan. During the SN-scan, the sensor circuit (1), or more precisely, the driving circuit (4) of the sensor circuit (1), generates and transmits a stimulus signal to excite an alternating electric field near the sensor (20) of the capacitive touch detection system (21), which subsequently produces an information portion at the receiving side, i.e., regarding the capacitive touch detection, regardless of whether one or more fingers of a user or different objects are detected near the surface of the sensor (20). Both the transmission of the stimulus signal and the reception of the returning sensor reception signal are handled by the sensor interface (2). For the purposes of this discussion and as an example, the stimulus signal is a periodic signal, i.e., a rectangular pulse train. The frequency of this periodic signal, i.e., the pulse frequency, is referred to as the operating frequency or carrier frequency of the SN-scan.

[0130] In addition to the acquisition operation, the sensor circuit (1) performs a noise scan in a corresponding noise scan mode. During the noise scan, preferably, no stimulus signal is applied to the sensor by the sensor circuit (1).

[0131] As discussed above, the noise scan serves as a test measurement and allows for the calculation of noise indices from the measurement data acquired during the noise scan, and the noise indices indicate the amount of noise expected during the SN-scan. Robustness against noise is a key challenge for any communication system or sensor system, including the capacitive touch sensing system (21). In particular, standard IEC noise tests using amplitude-modulated noise, such as in IEC 61000-4-6, bulk current injection (BCI) tests according to the ISO 11452-4 automotive standard, or passing robustness against square noise are addressed. Additionally, for various applications of the capacitive touch sensing system (21), it is important to produce a high touch reporting rate with reliable and accurate output estimates.

[0132] The goal of performing a noise scan is to determine an acquisition configuration for the operation of the capacitive touch sensing system (21) during the SN-scan. The acquisition configuration includes one or more parameters for the operation of the capacitive touch sensing system (21) during the SN-scan, and may include one or more of a sampling frequency for A / D conversion, an operating frequency (carrier frequency) of the stimulus signal for the operation (acquisition) of the sensor system, a scan duration, the number of samples to be acquired, and low-pass filter coefficients.

[0133] For the purposes of this discussion, it should be noted that the sampling frequency for A / D conversion during the SN-scan is considered to be related to the operating frequency / carrier frequency of the stimulus signal. One reason for this relationship is that the sensor received signal in this embodiment is a semi-static signal, that is, a stimulus signal in the shape of a rectangular pulse train, which is a signal that does not change or hardly changes over time during given time intervals. When the signal undergoes low-pass filtering at the receiving or sensing side and as discussed below, its edges are rounded, and the signal exhibits a transition duration until the signal stabilizes to a constant level after each edge. Here, the received signal is sampled once after each edge when the signal has stabilized to a sufficient degree, i.e., when there are two samples per period of the rectangular pulse train during the SN-scan, corresponding to a sampling frequency that is twice the carrier frequency.

[0134] The sensor circuit (1) further includes an A / D converter (5), a digital signal processing circuit (15), a noise evaluation circuit (8), a configuration circuit (9), a memory (10), a touch detector (11), and an output (12). The digital signal processing circuit (15) specifically includes a decimation circuit (not shown in FIG. 1) configured to determine a plurality of decimated digital reception signals, as will be discussed in more detail below. It should be noted that FIG. 1 does not illustrate all control connections between the aforementioned components for controlling, for example, the sampling rate of the A / D converter (5) or access to the memory (10) by the signal processing circuit (15).

[0135] During the noise scan, the signal processing chain of the A / D converter (5), digital signal processing circuit (15), noise evaluation circuit (8), and configuration circuit (9) is active.

[0136] During the SN-scan, the noise evaluation circuit (8) and the configuration circuit (9) are disabled or inactive. In this case, the sensor received signal is provided to the touch detector (11) for determining a user touch on the sensor (20) after A / D conversion and signal processing. The result is provided to a connected external component via the output (12).

[0137] The functions of the sensor circuit (1) and its components will be explained below with reference to the flowcharts of FIGS. 1 and FIGS. 3.

[0138] For the sake of brevity of the example, an exemplary capacitive touch or touchless sensing system (21) is assumed to have a plurality of acquisition configurations in which the analog front-end parameters are identical, but for the operating frequencies and their respective sampling frequencies, the respective sampling frequencies are twice the carrier frequencies in this exemplary embodiment as discussed above. The different sampling frequencies have a common multiple of a predefined noise scan frequency. Other digital signal processing parameters may or may not differ between these ACs, such as the number of samples to be filtered and the selection of low-pass filter coefficients.

[0139] Noise scanning begins at step 30 with the initialization / power-up of the sensor circuit (1). At step 31, the sensor reception signal is obtained from the sensor (20) using the sensor interface (2) as discussed above, without the application of a stimulus signal. Accordingly, the signal contains only noise.

[0140] Subsequently, in step 32, the sensor received signal is converted to A / D using an A / D converter (5) to obtain a digital sensor received signal. During the noise scan, the frequency indicated as the fundamental frequency or a predefined noise scan frequency. Data is acquired from. During the configuration phase (not shown), is selected to be a common multiple of the SN-scan sampling frequencies of multiple ACs. One of these ACs is, for example, a candidate carrier frequency Let's assume it has . During an SN-scan using such AC, the sampling frequency is It will be. However, the predefined noise scan frequency is R times higher, i.e. ..., where R is the decimation rate. Accordingly, the A / D converter (5) has a sampling frequency During the noise scan, the analog sensor received signal is sampled, meaning the sampling frequency is R times higher than that for the SN-scan.

[0141] In step 33, decimated digital reception signals are generated from digital sensor reception signals by the decimation circuit of the digital signal processing circuit (15).

[0142] Decimation of the digital sensor received signal reduces the number of samples within each decimated digital received signal. FIG. 4 schematically illustrates the operation of a digital signal processing circuit (15) for exemplary decimation rates R=2, 3, 4 and 6.

[0143] Decimation utilizes a number of different decimation rates, namely decimation rates R=2, 3, 4, and 6 as shown in FIG. 4. For each decimation rate, a number of decimated digital received signals are provided, which will be discussed in more detail below.

[0144] The application of decimation using multiple decimation rates allows multiple possible 'candidate' acquisition configurations to be evaluated from the same measurement data, i.e., the digital sensor received signal. As discussed above, the (candidate) acquisition configurations in this embodiment have sampling frequencies that are common multiples of the noise scan sampling frequency. Low-pass filter lengths and coefficient values ​​may also differ in some examples. Decimation of the noise scan digital sensor received signal using multiple decimation rates provides decimated digital received signals having these different sampling frequencies, thereby making it possible to evaluate different candidate acquisition configurations using the same sensor received signal. As will be evident from the example in FIG. 4, the scan duration is constant (i.e., The number of samples in decimated digital received signals equal to the packet length L of each AC varies according to the decimation rate. In some embodiments, the scan duration for different ACs may differ. For example, if a noise scan yields a total of 20 samples, R=4 will result in 4*5=20 samples, but if R=3, there will only be 3*6=18 samples, because 3*7=21 does not 'fit' the original sample length of 20.

[0145] Once the decimated digital received signals are generated, in step 34, the digital signal processing circuit (15) demodulates the decimated digital received signals. This is done by alternately multiplying the samples by plus 1 and minus 1, as is also done during the SN-scan, without limitation, as described herein. After demodulation, digital low-pass filtering using, for example, one or more finite impulse response (FIR) filters removes unwanted high-frequency signal components. Different decimation rates R may require differences in further processing, and in particular, the number of filter coefficients of the FIR filters may be different from the number of samples after decimation. Note that it may be identical to, that is, identical to the packet length L of each candidate AC, and that the values ​​of the filter coefficients may differ accordingly for different decimation rates R. In this embodiment, the filtering is a vector of low-pass filter coefficients with length L It is applied using the Hanning window. As defined by MathWorks, the nth element of the Hanning window is as follows:

[0146]

[0147] After filtering, Additional decimation is applied by providing a single output value for a block of acquired ADC samples. The resulting digital processing chain of the digital signal processing circuit (15) is discussed in more detail below with reference to FIG. 5, and for brevity, Is L It is abbreviated as .

[0148] Evaluation is performed by a noise evaluation circuit (8) that determines noise indicators for candidate acquisition configurations from the digital reception signals decimated in step 35.

[0149] As mentioned above, for each decimation rate, a group of decimated digital received signals is determined. For example, and as illustrated in FIG. 4, the upper part is Dog samples The original ADC 5 output signal having is shown. Below that, the decimation rates Regarding, a single original ADC signal is different starting samples It illustrates how it is demultiplexed into R signals having . By this, samples of the decimated signals are It is renamed as. That is, in Fig. 4 Dog samples and For the exemplary values ​​of, respectively, the lengths and decimated signals of 4 samples are produced.

[0150] As can be seen from Figure 4, for a decimation rate R=3, a total of three decimated digital received signals are determined, which show different starting phases, i.e., different starting samples. This is done to calculate a particularly useful noise indicator in step 35, namely the 'Effective Noise Power Estimate', also referred to as 'ENPE'.

[0151] Therefore, the process of Fig. 3, in the digital domain, has different signal phases of a digitally received signal. It provides decimation using, where each of the resulting R signals is a sampling rate It has. In some embodiments, the set of signal phases used is also the entire set of phases. A subset of, for example Note that this is possible. In other words, each group of decimated digital received signals does not necessarily include all possible signal phases.

[0152] Mathematically, for each decimation rate R, a coefficient vector having the same length as the decimation signals is assigned, for example, the coefficients of an FIR low-pass filter (LPF). To calculate ENPE for a decimation rate R, for each of up to R decimated signal vectors, the inner product with the assigned coefficient vector is calculated by the noise evaluation circuit (8) in step 35. Optionally, and in some embodiments, these inner products may be normalized by dividing by the sum of all coefficients. Then, the average of the squared inner products is calculated to yield ENPE.

[0153] In mathematical terms, Fig. 4 shows each The original signal vector for Illustrates how this is divided into up to R signal vectors.

[0154]

[0155] Here, , and It represents. is the length assigned to each decimation rate R. Let's assume that it represents the coefficient vector of. Next, Carrier frequency sampled from, demodulated and filtered by coefficients ENPE for the received signal at is the fundamental frequency It is calculated as follows from the sampled noise scan data vector x, decimation rate R, and coefficient vector w:

[0156]

[0157] Accordingly,

[0158]

[0159] is referred to as the phase-instantaneous noise indicator. Normalization term It guarantees a filter DC gain of 1 and can be shifted from the sum across phases ν—subsequently squared—and considered in a later processing step, leaving the following:

[0160]

[0161] To distinguish different decimation rates R, the j-th decimation rate index for Assigns a superscript having. Likewise, the decimation rate For the coefficient vector assigned to, Calculates.

[0162] Since the same measurement data is used to calculate noise indices for different candidate ACs, for example, temporal variations in experiencing amplitude-modulated noise affect the noise indices; however, the noise indices calculated from the same data remain similar to reliably identify the AC with the relatively lowest noise indices.

[0163] For decimation rates that are multiples of 2, phases The sum across phases Computational complexity can be reduced by changing it to a sum over, where is. For example, For this, the following can be used to calculate the reduced complexity ENPE.

[0164]

[0165] Once noise indices, i.e., ENPEs in this specification, are determined for each candidate acquisition configuration, the ENPEs are transferred to a configuration circuit (9) that selects an acquisition configuration for the operation of the sensor system from the candidate acquisition configurations using the ENPEs determined in step 36.

[0166] In this embodiment, the configuration circuit (9) determines which of the candidate acquisition configurations yields the lowest noise by evaluating the associated ENPEs in step 36.

[0167] Once a candidate acquisition configuration is selected as the acquisition configuration, the noise scan is completed. The acquisition configuration is provided to the driving circuit (4) by the configuration circuit (9). Additionally, the selected acquisition configuration is stored in memory (10) for future reference. Subsequently, the capacitive touch sensing system (21) is operated in at least one SN-scan (step 37) according to the results of the noise scan. It should be noted that, particularly in the case of mutual capacitive sensors, an SN-scan may be performed on multiple sensor (transmit) lines (3). After the SN-scan(s), starting from step 30, a new noise scan is performed.

[0168] Two resulting signal processing chains for noise scanning and SN-scan are illustrated in a simplified and schematic diagram in FIG. 5.

[0169] In the upper section, FIG. 5 illustrates digital processing of data acquired during an SN-scan. The sensor received signal is processed using an ADC (5) at the carrier frequency Twice as much, that is A digital sensor reception signal is obtained by converting from the analog domain to the digital domain. Subsequently, the digital ADC output signal, i.e., the digital sensor reception signal, is provided to a digital signal processing circuit (15) comprising a demodulator (13), an FIR low-pass filter (6), and a decimation circuit (7). The digital ADC output signal, i.e., the digital sensor reception signal, is demodulated by the demodulator (13) by alternately multiplying its samples by plus and minus 1, and the demodulated signal is input to a digital low-pass LPF filter (6) with L filter coefficients and finally decimated by factor L, that is, after inputting L samples, only one sample is output from the decimator (7).

[0170] In the lower part of FIG. 5, the processing of the digital processing circuit (15) and the noise evaluation circuit (8) during the noise scan is illustrated in more detail. The ADC (5) samples the analog sensor received signal at a predefined noise scan frequency. In FIG. 5, the processing of one exemplary AC is illustrated. The operation will be performed for each AC to be considered.

[0171] The exemplary AC is the carrier frequency It has. The sampled signal after conversion for obtaining the digital sensor reception signal by the ADC (5) is It is demultiplexed into R signals indexed by, and each of the R signals is at the sampling rate To provide conditions similar to those during an SN-scan and similar to those during an SN-scan, each of the demultiplexed signals is demodulated by its respective demodulator (13) by alternately multiplying its samples by plus and minus 1, and each demodulated signal is filtered by an FIR low-pass filter LPF (6) and decimated by a decimation circuit (7). Dog samples After analog-to-digital conversion and processing, one decimated sample is obtained for each decimated signal. Each decimated sample is squared by a noise evaluation circuit (8), and then the average of these R squared samples is calculated by the noise evaluation circuit (8) to produce ENPE.

[0172] It should be noted that the processing discussed above with reference to FIGS. 3 and FIGS. 5 does not necessarily need to be completed 'online'. Instead, and as discussed above with reference to FIGS. 3 through 5, each ADC sample go In one embodiment, samples are discarded as soon as they are multiplied and can yield a demodulated value as an intermediate product. It can be stored in memory (10) for offline processing. In this embodiment, the processing discussed with reference to FIGS. 3 and FIGS. 5 is initiated after A / D conversion.

[0173] FIG. 6 illustrates an exemplary flowchart of the operation of the sensor circuit (1) in another embodiment. The operation corresponds to the discussion above, particularly with reference to FIG. 3. Accordingly, the operation in steps 60 through 67 corresponds to the operation in steps 30 through 37, respectively, except for step 66a, in which the configuration circuit (9) sets the aperture time of the acquisition configuration used by the driving circuit (4) for the SN-scan to an integer multiple of the aperture time used by the A / D converter (5) during the current noise scan (including the same aperture times, i.e., integer = 1). To do so, the configuration circuit (9) is connected to the A / D converter (5) (not shown in FIG. 1). The aperture time is set back to the original aperture time in step 60 during the next noise scan cycle.

[0174] This embodiment is based on the inventor's recognition that when capturing analog data to generate time-discrete samples, the duration during which the analog signal is input to the measurement system—that is, the time during which the measurement system is exposed to the outside world and, consequently, its internal analog state is changed by the analog input signal—can affect the value of the output sample. For the ADC (5), this duration is the so-called 'aperture time'. A schematic diagram in FIG. 7 shows the frequency for aperture times of 0.833 µs and 2.5 µs. The magnitude of the transfer function of an ideal ADC, also referred to as the susceptibility to single-tone signals having, is shown. Spectral zeros can be observed at multiples of inverse aperture times, namely at 1 / 0.833us = 1.2 MHz and 1 / 2.5us = 400 kHz, respectively.

[0175] For some touch sensing devices, upon detection by an electrode, the current flowing to or from the sensor electrode is integrated over a deterministic amount of time. This integration time is also considered to be the aperture time.

[0176] The aperture time cannot be longer than the sample interval, which is the time between two consecutive samples, because the aperture time windows of two consecutive samples cannot overlap. The higher the sampling frequency, the shorter the sample interval, and consequently, the shorter the maximum aperture time. Therefore, the predefined noise scan frequency When sampling from (here is the carrier frequency of an exemplary AC), maximum aperture time The sampling frequency is It is shorter than during the SN-scan.

[0177] The desired aperture time may also depend on the sensor type. For example, signal settling times are typically higher for ITO sensors than for PCB sensors due to the lower conductivity of ITO compared to copper. Therefore, a longer aperture time may be required for ITO sensors compared to similarly shaped PCB sensors. Note that there are also cases where the aperture time has a virtually negligible effect on the measurements. These may include, for example, voltage measurements performed on the output of a voltage follower circuit ('buffer amplifier').

[0178] However, in certain scenarios, it is possible for the desired aperture time to be shorter than the SN-scan sample interval but exceed the noise scan sample interval. In that case, obviously, the desired aperture time is not applicable to the noise scan. Different, shorter aperture times can be selected for the noise scan. However, selecting different aperture times for the SN-scan and the noise scan may compromise the possibility of obtaining a reliable ENPE from the noise scan data for the SN-scan. In particular, when the noise scan sensitivity spectrum has zeros at frequencies where the SN-scan sensitivity spectrum does not, harmful noise is not visible in the noise scan data, and it is possible for the noise robustness algorithm to make insensitive decisions.

[0179] However, for certain ratios between SN-scan and noise scan aperture times, it is possible to yield a relatively optimal carrier frequency determination, that is, a determination regarding a relatively optimal acquisition configuration for some noise scenarios. This is the case when the noise scan aperture time is an integer fraction of the SN-scan aperture time, or correspondingly when the SN-scan aperture time is an integer multiple of the noise scan aperture time. This is illustrated as an example in FIG. 7 for a fraction 1 / 3 when all 'noise-scan zeros' (integration time 0.833us) belong to the 'SN-scan zeros' (integration time 2.5us).

[0180] ENPE provides an absolute estimate of the noise power of the received signal after demodulation and low-pass filtering. For some sensor systems or applications, there may be an upper threshold for this noise power, and operation exceeding this threshold is undesirable.

[0181] One exemplary approach to yield lower noise power is to increase the number of acquired and processed samples L, denoted herein as 'packet length,' so that the filter length is equal to L. Note that the filter length is equal to the filter order N+1, i.e., L=N+1. However, increasing the packet length alone and by itself generally does not improve noise suppression. Noise suppression relies primarily on selected low-pass filtering where the packet and filter lengths are only one sun. FIG. 17 illustrates an example of spectral noise suppression when the packet size is increased from 5 samples to 7 samples for a boxcar window and a Hanning window. For example, in the upper plot with a boxcar window, the noise sensitivity is normalized frequency It increases with respect to radians / samples and does not decrease.

[0182] FIG. 9 shows all noise frequencies in FIG. 9 for boxcar or rectangular window low-pass filters (top) and 'Hanning' window low-pass filters (bottom). or all normalized frequencies This illustrates how the packet length needs to be increased to improve noise suppression. In particular, the spectral zeros for shorter packet lengths must correspond to the zeros for longer packet lengths. In Fig. 9, this is shown to be achieved when, for a Boxcar window LPF, the longer packet length is a multiple of the shorter packet length, and for a Hanning window LPF, the longer packet length is a multiple of the shorter packet length plus 1. For Boxcar, Hanning window, and MATLAB Hanning window (where the Hanning window corresponds to the Hanning window with the first and last samples removed) low-pass filters, the rule for increasing the packet length L to L' to ensure improved noise suppression for all noise frequencies is as follows:

[0183] [Equation 1]

[0184] (1)

[0185] Another requirement for the sensor systems may be a minimum reporting rate, that is, the capacitive touch or touchless detection system (21) may be required to output data estimated at a reporting rate equal to or higher than the minimum reporting rate. This estimated data may be, for example, low-pass filtered and decimated data, such as as exemplified as "to the touch detector (11)" in FIG. 5 (top), or data calculated therefrom. Such a minimum reporting rate is typically independent of how the reported data is acquired and processed, that is, it is independent of, for example, the carrier frequency. However, the minimum reporting rate sets an upper limit for the measurement time as the inverse of the minimum reporting rate. Another requirement for the capacitive touch detection system (21) may be a minimum SNR, or in other words, that the expected noise power of the output value is below a limit. In some embodiments, this may even be a primary requirement, and when it cannot be achieved at a desired reporting rate, the reporting rate is reduced (i.e., the scan time is increased) while maintaining—and attempting to satisfy—noise power limits, as discussed below with reference to FIGS. 8a and 8b.

[0186] FIGS. 8a and 8b illustrate a flowchart of the operation of the sensor circuit (1) in another exemplary embodiment. The operation corresponds to the discussion above, particularly with reference to FIG. 6. Accordingly, the operation in steps 80 through 87 corresponds to the respective operation in steps 60 through 67, except for steps 82a and 86a through 86g as discussed below.

[0187] In step 82, the sensor reception signal obtained from the capacitive touch sensing system (21) is A / D converted to obtain a digital reception signal, which corresponds to the processing discussed above with reference to steps 32 and 62. In this embodiment, the sensor reception signal obtained during step 81 has a predefined maximum scan time, i.e., a predefined maximum duration. For example, the predefined maximum duration may be 200 microseconds.

[0188] In step 82a, a copy of the digital received signal having the maximum scan time is stored in memory (10). Subsequently, a portion of the digital received signal, namely a portion having a predefined minimum scan time, is selected. Further processing in steps 83 through 85 is based on this portion of the digital received signal.

[0189] In step 86, an acquisition configuration is selected from candidate acquisition configurations. For clarity, the processing in step 86 is illustrated in FIG. 8b, which is broken down into steps 86a through 86g.

[0190] In step 86a, the configuration circuit (9) selects a candidate acquisition configuration that yields the lowest noise by evaluating the associated ENPEs as determined in step 85. In step 86b, the configuration circuit (9) determines whether the selected ENPE meets or is lower than a predefined noise threshold, which may be defined as noise power or SNR. For example, the predefined noise threshold for SNR may be 20 dB. If the selected ENPE meets or is lower than the predefined noise threshold, the selected candidate acquisition configuration is set to be the acquisition configuration for the SN-scan in step 87, corresponding to the previous description. The aperture time for the SN-scan is set in step 86c as discussed with reference to FIG. 6.

[0191] If the noise index for the selected candidate acquisition configuration exceeds a predefined noise threshold, processing continues to step 86d. In step 86d, assuming that the predefined maximum scan time has not been reached, the configuration circuit (9) increases the scan time by approximately an integer multiple and evaluates this increased scan time. To do so, in step 86e, the configuration circuit (9) obtains from memory (10) a copy of the original digital received signal having the maximum scan time, which was stored in step 82a. Then, in step 86f, a larger portion of the original digital received signal having a scan time that is an integer multiple of the previous scan time, for example, twice the scan time of the evaluated previous portion, is selected. Processing then continues to step 83, and the increased scan time is evaluated according to steps 83 through 86, as previously discussed.

[0192] Mathematically, the Noise Robustness Level (NRL) is used herein as an index for a predefined maximum scan or measurement time. For example, NRL shortest maximum scan time Let's assume it represents the lowest NRL corresponding to . For each candidate acquisition configuration, its packet length is the sampling frequency The maximum number of samples that can be acquired during this time It is set to, and here is the carrier frequency of AC. For example, and When, the resulting packet length is There are several ADC samples.

[0193] Next higher NRL Regarding this, for each AC, the packet length is, for example, the parameter An equation that relies on a low-pass filter design having, i.e., approximately twice the scan time. It is determined according to.

[0194] The discussed steps are repeated in a repetitive manner until an acquisition configuration satisfying the noise threshold is found or a predefined maximum scan time is reached and the acquisition configuration does not satisfy the noise threshold. In the latter case, the query in step 86d leads to the generation of a warning signal at the output (12) in step 86g, warning that no suitable acquisition configuration was found. The operation then proceeds to step 86c, which calculates the best noise indicator for operation in the SN-scan using the AC.

[0195] As will be apparent from the above, the scan cycle may consist of an SN-scan using the AC that yielded the best noise index, followed by a noise scan. This is followed by the next scan cycle having the next noise scan and the SN-scan. The scan cycle is then repeated until the device is shut down.

[0196] As discussed above, the goal is to find the lowest NRL, i.e., the shortest required scan time and consequently the highest reporting rate, which has a candidate acquisition configuration that yields an ENPE of at most the noise threshold. When there is more than one acquisition configuration with the same scan time that yields an ENPE below the limit, the process of FIGS. 8a and FIGS. 8b selects the AC that yields the lowest ENPE.

[0197] When there are candidate ACs whose sampling frequencies do not share common multiples, a slightly modified process using multiple predefined noise scan frequencies may be used. A corresponding exemplary embodiment is illustrated in the flowchart of FIG. 10.

[0198] Predefined noise scan frequency Given a noise scan signal sampled from, it is possible to select multiple different values ​​for the integer decimation rate R.

[0199] However, noise scan frequency Carrier frequencies for which ENPE can be calculated given a signal sampled from The number is effectively limited.

[0200] To increase the set of candidate carrier frequencies, additional noise scan frequencies may be evaluated in the matched embodiment. To distinguish these noise scan frequencies, the i-th candidate fundamental frequency index for Assign a superscript having. The j-th decimation rate for the i-th candidate fundamental frequency is It is denoted as, and its corresponding candidate carrier frequency and coefficient vectors are, respectively, and It is displayed as.

[0201] Packet length for AC with fundamental frequency index i, sub-frequency index j, and NRL ρ It is indicated as.

[0202] The process begins at step 100 with the initialization of the sensor circuit (1). For each predefined noise scan frequency, individual noise scans are performed in steps 101, 102, and 103. It should be noted that the present embodiment is not limited to the performance of three subsequent noise scans. The operation during each noise scan corresponds to one of the embodiments discussed above with reference to FIGS. 1 through 9. In each of steps 101, 102, and 103, a noise index for at least one candidate AC is obtained. In some embodiments, noise indexes for the same candidate AC may be obtained in multiple steps 101, 102, and 103.

[0203] In step 104, the overall acquisition configuration is determined from the candidate acquisition configurations evaluated in steps 101, 102, and 103. The overall acquisition configuration is determined by selecting the candidate acquisition configurations of steps 101, 102, and 103 from which the lowest ENPE is calculated overall. In other words, the overall acquisition configuration corresponds to the best possible candidate acquisition configuration of the noise scans (101, 102, 103). The idea of ​​NRLs can also be applied to this case for multiple noise scan frequencies. In step 105, the sensor system is operated in an SN-scan using the overall acquisition configuration. The operation then returns to step 100 until the processing of the sensor circuit (1) is stopped.

[0204] In contrast to other known approaches, the approach described according to various embodiments provides not only a solution for identifying the relatively optimal carrier frequency but also a complete solution for noise robustness. It even yields robustness against, for example, AM noise and square noise. This is made possible by highly accurate quantitative SNR or noise power estimates that can be calculated from the same measurement data but for different ACs. This also allows finding the trade-off between the touch reporting rate and the output SNR.

[0205] Furthermore, for a selected low-pass filter design method, e.g., a boxcar window filter function, and with the requirement to ensure improved noise robustness when increasing the scan time while leaving other AC parameters unchanged, many of the parameters of the candidate ACs (e.g., filter length and filter coefficient values) can be derived from some high-level requirements (e.g., 200us scan time), allowing for a simple noise robustness configuration without the need for extreme training.

[0206] Further exemplary aspects of the present disclosure relate to digital processing for signal acquisition using superimposed aperture windows as well as acquiring separate copies of currents.

[0207] When capturing analog data to generate time-discrete or digital output samples, the time duration during which the analog signal is input to the measurement system—that is, the time during which the measurement system is exposed to the outside world and, consequently, its internal analog state is changed by the analog input signal—can affect the value of the output sample.

[0208] For an analog-to-digital converter (ADC), this time duration is known as the aperture time, as discussed above. As mentioned above, FIG. 7 shows the frequency for aperture times of 0.833 µs and 2.5 µs. The magnitude of the transfer function of an ideal ADC, also referred to as sensitivity to single-tone signals having, is plotted. Spectral zeros are observed at multiples of inverse aperture times, e.g., 1 / 0.833us = 1.2 MHz and 1 / 2.5us = 400 kHz, respectively.

[0209] Using some available touchscreen controllers, upon electrode detection, the current flowing to or from the sensor electrode is integrated over a deterministic time period to measure the amount of charge transferred during this time. This integration time is the aperture time. A basic exemplary diagram of charge measurement using current integration is shown in Fig. 11. It is the signal exemplified on the right side of the diagram. The aperture switch controlled by is on and the signal While the reset switch controlled by is off, the capacitor Current integrated on the phase Illuminate an unknown current source that generates [something]. The resistor R of the current source is negligible when the aperture switch is on.

[0210] According to standard serial processing of analog signals, the aperture time cannot be longer than the time between two consecutive samples, which is typically the sample interval, because the aperture time windows of two consecutive samples cannot overlap. The higher the sampling frequency, the shorter the sample interval and consequently the shorter the maximum aperture time.

[0211] There are applications where it may be beneficial to have adjacent or overlapping aperture time windows for consecutive samples. For example, above, two different types of measurements, namely 'noise scan' and 'SN scan', are described, where the sampling frequency of the first type is a multiple of the sampling frequency of the second type, but the same aperture time is required for both. An aperture time is selected for the SN scan, but the sampling frequency for the noise scan may be too high to fit within the selected time aperture window between the two consecutive samples—the aperture windows will overlap.

[0212] To yield overlapping aperture time windows, several means of parallel processing may be beneficial. For example, for systems such as the aforementioned touchscreen controllers, two or more integrators would be beneficial. The problem is the risk that these two or more integrators may potentially interfere with each other's measurements when tapping the same pad or measurement node. This is illustrated in Fig. 12, where the states of the aperture switches are on the right. and It is floating over time. Both aperture switches During this ON-in time, the unknown input current is split uncontrolled between the two integrators. Therefore, deterministic measurements using overlapping aperture time windows may not be possible. The same analog input current cannot be measured multiple times in this way without interference between the measurements.

[0213] In capacitive sensing, the desired aperture time may depend, for example, on the sensor type. For instance, signal settling times are typically higher for ITO sensors than for PCB sensors due to the lower conductivity of ITO compared to copper. Therefore, longer aperture times may be required for ITO sensors compared to similarly shaped PCB sensors.

[0214] Based on the above, the solution may be to use a current amplifier having one input and multiple outputs to produce multiple separate copies of the input current. Each copy may then be tapped into a single integrator, and the integrator input currents are separated, that is, mutually independent. In a digital post-processing step, the data obtained from the multiple analog copies may be rearranged, for example, to produce a single digital output signal.

[0215] The principle approach of this discussion is to generate multiple separate copies of an analog input signal. Subsequently, analog processing and A / D conversion can be performed individually for each of the signal copies. The final step is to interleave or multiplex digital samples from different processing branches into a single output signal.

[0216] A standard electronic component in which the input current is independent of the output current is a transistor. For more complex components, such as amplifiers that may contain such transistors, this independence is also maintained. When an input current controls two output currents and the input current is independent of either of the output currents, this implies that the output currents are also mutually independent.

[0217] For some touchscreen controller devices and classic touchscreen controller measurements, the analog input signal is current. The analog front-end (AFE) of some conventional touchscreen controllers provides a number of essentially identical parallel units for analog processing, referred to as slices. Each slice includes an integrator.

[0218] While it would be desirable to have completely independent timings for different integrators, some touchscreen controller devices may be limited to a common sampling interval or sampling frequency for all slices. However, aside from the small digital modifications required, existing devices will allow independent measurements of two copies of the input current, where the aperture time windows of the two measurements overlap. Fig. 13 schematically illustrates two of the so-called slices of an exemplary AFE of a touchscreen controller. The pad of the main slice in the upper left of Fig. 13 is connected to the input X of a current amplifier. The non-inverting output Z0 of this current amplifier is connected to an integrator, the output of which is connected to an ADC. The inverting output Z1 of the current amplifier of the main slice is connected to the input of an integrator on the second slice, followed again by an ADC. The current amplifier of the second slice is isolated so that only the inverting current of the main slice amplifier is input to the integrator. The aperture switches INTMOE can be controlled independently for the main and secondary slices, but the integrator reset switches RST1 and RST2 may not be controllable independently.

[0219] In the above, the need for overlapping aperture time windows or current integration windows was discussed for noise scans. For such noise scans, interest may be primarily in measurement data from a single slice, for example, a slice connected to a sensor electrode where the highest noise level may be expected. Assuming that the main slice is connected to this noisiest electrode, for example, that this noisiest electrode is connected to a pad of the main slice in FIG. 13, theoretically, two separate copies of the input current of the main slice are obtained, and it is possible to open or close the aperture or reset switches in both the main and secondary slices without affecting the current on the other slice.

[0220] FIG. 14 illustrates an exemplary timing diagram for current integration and integrator reset assuming slice-independent control of the aperture and reset switches. Each integration window is preceded by a reset of the integration capacitor. The integration windows of the main and secondary slices are interleaved and superimposed in time. After analog-to-digital (A / D) conversion, samples from the two slices are interleaved to produce a single digital signal. For example, the new single digital signal is generated by chaining a first output sample from the main slice, a first output sample from the secondary slice, a second sample from the main slice, a second sample from the secondary slice, and so on. In the context of a noise scan, note that the acquired signal is decimated before further processing, and that after decimation, the current integration windows corresponding to consecutive samples within these decimated signals are no longer superimposed.

[0221] However, although the integration can be controlled individually for the main and secondary slices, the timing of FIG. 14 may not be achievable with some touchscreen controller devices due to the integrator reset control being common to the main and secondary slices.

[0222] What can be done with some touchscreen controllers is timing with non-overlapping integration windows, similar to that in FIG. 14 but as exemplified in FIG. 15. In practice, A / D conversion is also performed synchronously on the main and secondary slices, as indicated by the vertical dashed line, and thus one filtered digital sample from each slice is not required—because it is acquired not at the end of the integration stage of the current integrators but perhaps during a random integrator state—and can be discarded accordingly.

[0223] Data obtained from a test implementation using the timing configuration of FIG. 15 is illustrated in FIG. 16. A single-tone signal having 20 kHz is coupled to a sensor electrode connected to slice Y34, and the sampling frequency is 200 kHz. Samples from the main slice Y34 and the secondary slice Y35 are shown in an interleaved manner, while solid and dashed lines connect samples from each slice, respectively. Since the signal for Y35 is a mirror image of the signal for Y34 mirrored at a level of approximately ADC value -15, it can be observed that the signal for slice Y35 (dashed line) still needs to be re-inverted and shifted. The required offset would need to be determined before actual signal acquisition (e.g., with the pad / electrode disconnected, i.e., without an input signal), but signal reconstruction in the digital domain is feasible.

[0224] When referring to the 'copying' of an analog signal in this specification, an exact one-to-one copy is not necessarily required. For some applications, a strictly monotonic copying function may be sufficient, and any distortion may be compensated for in the digital domain.

[0225] However, for systems having processing such as touchscreen controller devices where current is integrated before A / D conversion, only linear distortion of the input signal, i.e., the input current, may be acceptable in some embodiments to allow digital equalization (i.e., compensation of distortion). Additionally, generally, more or fewer linear radiation functions may be beneficial, for example, when considering signal equalization with ADC quantization noise.

[0226] The proprietary solution of previous touchscreen controllers allows for the overlap of aperture time windows when the acquisition frequencies on the main and secondary slices are the same, but only the acquisition phases differ. However, when hardware control allows for completely independent timing for different slices given multiple copies of the same analog signal, it will be possible to yield a general solution to the problem of signal acquisition for noise level evaluation using different AFE configurations, including arbitrary different sampling frequencies and aperture time windows.

[0227] Some embodiments of a sensor system having an analog input signal x(t) have two or more analog copies y of x(t) i Provides making (t), i=0, 1, ...

[0228] In some embodiments, copy y i (t) is a strictly monotonic function of x(t).

[0229] In some embodiments, copy y i (t) are linear functions of x(t) y i (t)=b i *x(t)+a i am.

[0230] In some embodiments, the sensor system is a capacitive sensing system.

[0231] In some embodiments, the signal x(t) is a current.

[0232] In some embodiments, the signal y(t) is a current.

[0233] In some embodiments, two or more copies of an analog signal y i (t) is an analog circuit H to generate digital samples. i Input to and at least two circuits H i The aperture windows of overlap in time.

[0234] In some embodiments, analog circuits H i It includes an integrator.

[0235] In some embodiments, two or more circuits H i The sampling frequency of the image is the same.

[0236] In some embodiments, the sensor system includes a current amplifier whose input is supplied as x(t), where the current amplifier has two or more output stages that share one input stage.

[0237] In some embodiments, samples from signals on different branches are multiplexed to produce a single output signal.

[0238] A general solution for making copies of analog input signals to produce separated signals for independent processing made possible in this specification is useful for solving the problem of comparing any AFE configurations with one another and for finding a suitable acquisition configuration.

[0239] In some embodiments, the aperture time is increased beyond the sampling period, thereby allowing for very accurate noise power estimation.

[0240] Compared to alternative approaches that evaluate signals from different sensor electrodes, the discussed approach—because all evaluated data originates from a single sensor electrode—does not pose a risk of noise coupling to different sensor electrodes with different coupling strengths, which can introduce false bias to the estimates.

[0241] Although the present invention has been described with respect to specific embodiments thereof, such embodiments are merely illustrative and are not intended to limit the invention. The description of the illustrative embodiments of the invention in this specification, including the descriptions in the 'Abstract' and 'Content of the Invention,' is intended to be comprehensive and is not intended to limit the invention to the exact form disclosed herein (and in particular, the inclusion of any specific embodiment, feature, or function in the 'Abstract' or 'Content of the Invention' is not intended to limit the scope of the invention to such embodiment, feature, or function). Rather, the description is intended to explain illustrative embodiments, features, and functions to provide a context for understanding the invention to a person skilled in the art, including any such embodiment, feature, or function described in the 'Abstract' or 'Content of the Invention,' without limiting the invention to any specifically described embodiment, feature, or function. While specific embodiments of the invention and specific examples thereof are described herein for illustrative purposes only, as will be recognized and acknowledged by those skilled in the art, various equivalent modifications are possible within the spirit and scope of the invention. As indicated, such modifications may be made to the invention in consideration of the above description of the exemplary embodiments of the invention and shall be contained within the spirit and scope of the invention. Accordingly, although the invention has been described herein with respect to specific embodiments thereof, freedom of modification, various changes and substitutions is intended to be within the foregoing disclosure, and it will be recognized that in some cases, certain features of the embodiments of the invention may be utilized without corresponding use of other features without departing from the scope and spirit of the invention as described. Accordingly, many modifications may be made to adapt specific situations or materials to the essential scope and spirit of the invention.

[0242] Throughout this specification, references to “one embodiment,” “an embodiment,” or “a specific embodiment” or similar terms mean that a specific feature, structure, or characteristic described in relation to that embodiment is included in at least one embodiment and may not necessarily be present in all embodiments. Accordingly, the respective appearances of phrases “in one embodiment,” “in an embodiment,” or “in a specific embodiment” or similar terms throughout this specification do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of any specific embodiment may be combined with one or more other embodiments in any suitable manner. It should be understood that other variations and modifications of the embodiments described and illustrated herein are possible in light of the teachings of this specification and should be considered part of the spirit and scope of the invention.

[0243] In the description herein, numerous specific details, such as examples of components and / or methods, are provided to provide a thorough understanding of the embodiments of the invention. However, those skilled in the art will recognize that the embodiments may be implemented without one or more of the specific details, or with other devices, systems, assemblies, methods, components, materials, parts, etc. In other cases, well-known structures, components, systems, materials, or operations are not specifically illustrated or described in detail to avoid obscuring aspects of the embodiments of the invention. While the invention may be illustrated by the use of specific embodiments, this does not limit the invention to any specific embodiment, and those skilled in the art will recognize that additional embodiments are readily understood and are part of the invention.

[0244] Any suitable programming language, including C, C++, Java, and assembly language, without limitation, may be used to implement the routines, methods, or programs of the embodiments of the invention described herein. For example, different programming techniques, such as procedural or object-oriented, may be used. Any particular routine may be executed on a single computer processing device or multiple computer processing devices, a single computer processor or multiple computer processors. Data may be stored on a single storage medium or distributed across multiple storage media, and may be in a single database or multiple databases (or other data storage technologies). Steps, operations, or calculations may be presented in a specific order, but such order may be changed in different embodiments. In some embodiments, where multiple steps are presented as sequential in this specification, any combination of such steps may be performed simultaneously in alternative embodiments. The sequence of operations described herein may be interrupted, suspended, or otherwise controlled by other processes, such as an operating system, kernel, etc. Routines may operate in an operating system environment or as standalone routines. The functions, routines, methods, steps, and operations described in this specification may be performed in hardware, software, firmware, or any combination thereof.

[0245] The embodiments described herein may be implemented in the form of control logic in software, hardware, or a combination of both. The control logic may be stored on an information storage medium, such as a computer-readable medium, as a plurality of instructions adapted to instruct an information processing device to perform a set of steps disclosed in various embodiments. Based on the disclosures and teachings provided herein, a person skilled in the art will recognize other modes and / or methods for implementing the invention.

[0246] It is also within the spirit and scope of the invention to implement any of the steps, operations, methods, routines, or parts thereof described herein in software programming or code, such software programming or code may be stored on a computer-readable medium and operated by a processor to enable a computer to perform any of the steps, operations, methods, routines, or parts thereof described herein. The invention may be implemented by utilizing software programming or code on one or more general-purpose digital computers, by utilizing application-specific integrated circuits, programmable logic devices, field-programmable gate arrays, etc. Optical, chemical, biological, quantum, or nanoengineered systems, components, and mechanisms may be utilized. In general, the functions of the invention may be achieved by any means known in the art. For example, distributed or networked systems, components, and circuits may be utilized. In other examples, the communication or transmission of data (or otherwise moving from one place to another) may be wired, wireless, or by any other means.

[0247] "Computer-readable medium" may be any medium capable of containing, storing, communicating, propagating, or transporting a program for use by or in connection with an instruction execution system, device, system, or device. Computer-readable medium may be, by example and not limitation, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor systems, devices, systems, devices, propagation media, or computer memory. Such computer-readable medium will generally be machine-readable and will contain software programming or code that is human-readable (e.g., source code) or machine-readable (e.g., object code). Examples of non-transient computer-readable media may include random access memories, read-only memories, hard drives, data cartridges, magnetic tapes, floppy disks, flash memory drives, optical data storage devices, compact disc read-only memories, and other suitable computer memories and data storage devices. In exemplary embodiments, some or all of the software components may be on a single server computer or on any combination of separate server computers. As will be recognized by those skilled in the art, a computer program product implementing an embodiment disclosed herein may include one or more non-transient computer-readable media storing computer instructions that are translatable by one or more processors in a computing environment.

[0248] "Processor" includes any hardware system, mechanism, or component that processes data, signals, or other information. A processor may include a system having a general-purpose central processing unit, multiple processing units, dedicated circuitry for achieving functions, or other systems. Processing is not limited to a geographical location or time. For example, a processor may perform its functions in "real-time," "offline," "batch mode," etc. Parts of the processing may be performed by different (or identical) processing systems at different times and at different locations.

[0249] Terms such as “component,” “module,” “circuit part,” “circuit,” “device,” “unit,” and “system” are intended to include hardware, software, firmware, or any combination thereof. For example, a system or component may be a process, a process running on a processor, or a processor. Furthermore, a function, component, or system may be localized on a single device or distributed across multiple devices. The described subject may be embodied as a device, method, or manufactured article utilizing standard programming or engineering techniques to create software, firmware, hardware, or any combination thereof for controlling one or more computing devices.

[0250] As used herein, the terms “comprising,” “comprising,” “equipping,” “equipping,” “having,” “having,” or any other variations thereof are intended to encompass non-exclusive inclusion. For example, a process, product, article, or device comprising a list of elements is not necessarily limited to such elements alone and may include other elements not explicitly listed or unique to such process, process, article, or device. Throughout this specification, the term “exemplary” means “serving as an example, case, or illustration” and does not mean “preferential” or “having advantages” over other embodiments.

[0251] Furthermore, as used herein, the term “or” is generally intended to mean “and / or” unless otherwise indicated. For example, condition A or B is satisfied by any one of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); and both A and B are true (or exist). Including the claims below, as used herein, the term preceded by “a” or “an” (and “the” where the preceding basis is “a” or “an”) includes both the singular and plural forms of such term unless otherwise explicitly indicated within the claim (i.e., unless the mention of “a” or “an” explicitly indicates only the singular or only the plural). Also, as used in the description herein and throughout the claims below, the meaning of “in” includes “in” and “on” unless the context otherwise explicitly indicates.

[0252] It will also be recognized that one or more of the elements depicted in the drawings / figures may be implemented in a more separate or integrated manner, as useful for a particular application, or even removed or rendered as non-operable in certain cases. Additionally, any signal arrows in the drawings / figures should be considered merely illustrative and not limiting, unless otherwise clearly stated.

[0253] Accordingly, the scope of the present invention is intended to be limited only to the following claims as they may be modified, each of which is explicitly incorporated herein as an embodiment of the present invention.

[0254] Other variations to the disclosed embodiments may be understood and made by a person skilled in the art in practicing the claimed invention from a review of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the singular form (the indefinite article “a” or “an”) does not exclude the plural. A single processor, module, or other unit may satisfy the functions of several items listed in the claims.

[0255] The mere fact that certain means are listed in different dependent claims does not indicate that a combination of these means cannot be used advantageously. A computer program may be stored / distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, for example, through the Internet or other wired or wireless communication systems. Any reference numerals in the claims should not be interpreted as limiting the scope.

Claims

Claim 1 A method for determining a noise-robust acquisition configuration for the operation of a sensor system comprises the step of performing a noise scan, wherein the noise scan comprises: the step of acquiring a sensor receive signal when no stimulus signal is applied to the sensor system; and the step of determining a digital sensor receive signal by A / D converting the sensor receive signal using an A / D converter at a predefined noise scan frequency from the sensor receive signal when no stimulus signal is applied to the sensor system. A method for determining a noise robustness acquisition configuration, comprising: a step of determining a plurality of decimated digital sensor reception signals by performing integer decimation on the digital sensor reception signals using two or more different decimation rates, wherein each decimation rate is associated with a candidate acquisition configuration of the sensor system; a step of determining one or more noise measures by evaluating one or more of the decimated digital sensor reception signals for the plurality of candidate acquisition configurations in response to the determination of the plurality of decimated digital sensor reception signals, by a controller; and a step of determining an acquisition configuration to be used for the operation of the sensor system among the plurality of candidate acquisition configurations using the one or more noise measures, wherein the step of determining the acquisition configuration includes a step of selecting a preferred noise measure among the one or more noise measures and a step of selecting one candidate acquisition configuration among the plurality of candidate acquisition configurations associated with the preferred noise measure as the acquisition configuration. Claim 2 delete Claim 3 A method for determining a noise robustness acquisition configuration, wherein the preferred noise indicator calculates the lowest noise level of one or more noise indicators in claim 1. Claim 4 A method for determining a noise robustness acquisition configuration according to claim 1, wherein for each of two or more different decimation rates, groups of corresponding decimated digital sensor received signals are determined, and within each group, said decimated digital sensor received signals have different starting phases. Claim 5 A method for determining a noise robustness acquisition configuration according to claim 4, wherein one or more noise indices are determined by effective noise power estimation, and the effective noise power estimation includes the step of determining the sum of phase-instantaneous noise measures for each decimated digital sensor received signal included in one of the groups of decimated digital sensor received signals. Claim 6 A method for determining a noise robustness acquisition configuration according to claim 5, wherein the phase-instantaneous noise index is the sum of samples of a decimated digital sensor received signal weighted by coefficients from a coefficient vector. Claim 7 A method for determining a noise robustness acquisition configuration according to claim 1, wherein the acquisition configuration comprises at least one of a sampling frequency for A / D conversion, an operating frequency of a stimulus signal for the operation of a sensor system, a scan duration, the number of samples to be acquired, and coefficients of a low-pass filter. Claim 8 A method for determining a noise robustness acquisition configuration according to claim 1, wherein the predefined noise scan frequency is higher than the operating frequency of the stimulus signal during the operation of the sensor system. Claim 9 A method for determining a noise robustness acquisition configuration according to claim 1, wherein the two or more decimation rates are multiples of 2. Claim 10 A method for determining a noise robustness acquisition configuration according to claim 1, wherein the sensor reception signal is acquired during a noise scan while the stimulus signal is not applied to the sensor system. Claim 11 A method for determining a noise robustness acquisition configuration according to claim 1, wherein the step of determining an acquisition configuration for the operation of a sensor system from the candidate acquisition configurations comprises: comparing one or more noise indicators with a noise threshold; if none of the noise indicators satisfy the noise threshold, increasing the scan time of at least one of the candidate acquisition configurations to generate an updated candidate acquisition configuration; determining one or more updated noise indicators for the updated candidate acquisition configuration; and comparing one or more updated noise indicators with the noise threshold. Claim 12 A method for determining a noise robustness acquisition configuration according to claim 11, wherein the increase in the scan time is an integer multiple of the scan time of the previous noise scan. Claim 13 A method for determining a noise robustness acquisition configuration according to claim 1, comprising the step of operating a sensor system during a signal-and-noise scan using the acquisition configuration determined during the noise scan after the noise scan. Claim 14 A method for determining a noise robustness acquisition configuration according to claim 13, comprising the step of subsequently performing a plurality of noise scans between two signal and noise scans, wherein the plurality of noise scans use a predefined noise scan frequency, and at least some of the noise scan frequencies among the plurality of noise scans are different from each other. Claim 15 A method for determining a noise robustness acquisition configuration according to claim 14, further comprising the step of determining an overall acquisition configuration for the operation of a sensor system during signal and noise scans from a plurality of acquisition configurations acquired during a plurality of noise scans subsequently performed. Claim 16 A method for determining a noise robustness acquisition configuration according to claim 13, wherein the aperture time of the A / D conversion during the noise scan is equal to the aperture time set for the signal and noise scan, or is a substantial integer fraction of the aperture time. Claim 17 A method for determining a noise robustness acquisition configuration, wherein, in claim 1, the sensor system is one or more of a capacitive sensor system or a touchscreen sensor system. Claim 18 delete Claim 19 delete Claim 20 delete Claim 21 A non-transient computer-readable medium storing command content that causes a sensor circuit to perform the method of claim 1. Claim 22 A sensor circuit for determining an acquisition configuration for the operation of a sensor system, comprising: a sensor interface for acquiring a sensor reception signal from a sensor system when no stimulus signal is applied; an A / D converter for determining a digital sensor reception signal by A / D converting the sensor reception signal at a predefined noise scan frequency; a decimation circuit for determining a plurality of decimated digital sensor reception signals by performing integer decimation on the digital sensor reception signal using two or more different decimation rates, wherein each decimation rate corresponds to each candidate acquisition configuration of the sensor system; and a noise evaluation circuit for determining one or more noise indices for the plurality of candidate acquisition configurations by evaluating one or more of the plurality of decimated digital sensor reception signals. A sensor circuit comprising a configuration circuit for determining an acquisition configuration to be used for the operation of a sensor system from a plurality of candidate acquisition configurations using one or more noise measures, wherein determining the acquisition configuration comprises selecting a preferred noise measure among the one or more noise measures and selecting a first candidate acquisition configuration among a plurality of candidate acquisition configurations associated with the preferred noise measure as the acquisition configuration. Claim 23 delete Claim 24 A capacitive touch sensing system comprising: one or more electrodes configured for capacitive sensing; and a sensor circuit according to claim 22, wherein the sensor circuit is connected to at least one of the one or more electrodes. Claim 25 delete Claim 26 A method for determining a noise-robust acquisition configuration for the operation of a communication system comprises the step of performing a noise scan, wherein the noise scan comprises: the step of acquiring a receive signal from a communication system when no stimulus signal is applied to the communication system; the step of determining a digital receive signal by performing A / D conversion on the receive signal using an A / D converter at a predefined noise scan frequency; the step of determining a plurality of decimated digital receive signals by performing integer decimation on the digital receive signal using two or more different decimation rates, wherein each of the two or more decimation rates is associated with one of a plurality of candidate acquisition configurations of the communication system; and in response to the determination of the plurality of decimated digital receive signals, for the plurality of candidate acquisition configurations, the A step of determining one or more noise measures by evaluating one or more of the decimated digital received signals;A method for determining a noise robustness acquisition configuration, comprising the step of determining an acquisition configuration to be used for the operation of a communication system among a plurality of candidate acquisition configurations using one or more noise measures, wherein the step of determining the acquisition configuration includes the step of selecting a preferred noise measure among the one or more noise measures and the step of selecting one candidate acquisition configuration among a plurality of candidate acquisition configurations associated with the preferred noise measure as the acquisition configuration. Claim 27 A communication circuit for determining an acquisition configuration for the operation of a communication system, comprising: a communication system interface—an interface for acquiring a receive signal from a communication system when a stimulus signal is not applied to the communication system; an A / D converter—a converter for determining a digital receive signal from the receive signal by A / D converting the receive signal at a predefined noise scan frequency; a decimation circuit—a circuit configured to determine a plurality of decimated digital receive signals by performing integer decimation on the digital receive signals using two or more different decimation rates—each of the two or more decimation rates being associated with one of a plurality of candidate acquisition configurations of the communication system—; and a noise evaluation circuit—on which the plurality of decimated digital receive signals have been determined A noise evaluation circuit configured to determine one or more noise measures for a plurality of candidate acquisition configurations by evaluating one or more of the plurality of decimated digital reception signals in response;and configuration circuit - comprising a configuration circuit configured to determine an acquisition configuration for the operation of a communication system from a plurality of candidate acquisition configurations using one or more noise measures, wherein determining the acquisition configuration includes selecting a preferred noise measure among the one or more noise measures and selecting a first candidate acquisition configuration among a plurality of candidate acquisition configurations associated with the preferred noise measure as the acquisition configuration. Claim 28 A method for determining a noise-robust acquisition configuration for the operation of a sensor system comprises the step of performing a noise scan, wherein the noise scan comprises: the step of acquiring a sensor receive signal when no stimulus signal is applied to the sensor system; and the step of determining a digital sensor receive signal by A / D converting the sensor receive signal from the sensor receive signal using an A / D converter at a predefined noise scan frequency when no stimulus signal is applied to the sensor system. A step of determining a plurality of decimated digital sensor receive signals by performing integer decimation on the digital sensor receive signals using two or more different decimation rates, wherein each decimation rate is associated with a candidate acquisition configuration of the sensor system; a step of determining one or more noise measures by evaluating one or more of the decimated digital sensor receive signals for the plurality of candidate acquisition configurations in response to the determination of the plurality of decimated digital sensor receive signals, by evaluating one or more of the decimated digital sensor receive signals in a controller; and a step of determining an acquisition configuration to be used for the operation of the sensor system among the plurality of candidate acquisition configurations using the one or more noise measures, wherein the step of determining an acquisition configuration to be used for the operation of the sensor system among the candidate acquisition configurations comprises a step of comparing one or more noise measures with a noise threshold.A method for determining a noise robustness acquisition configuration, comprising: a step of increasing the scan time of at least one candidate acquisition configuration to acquire at least one updated candidate acquisition configuration when the noise threshold is not satisfied by any noise measure; a step of determining one or more updated noise measures for the at least one updated candidate acquisition configuration; and a step of comparing the one or more updated noise measures with the noise threshold. Claim 29 A non-transient computer-readable medium storing command content that causes a sensor circuit to perform the method of claim 28. Claim 30 A sensor circuit for determining an acquisition configuration for the operation of a sensor system, comprising: a sensor interface for acquiring a sensor reception signal from a sensor system when no stimulus signal is applied; an A / D converter for determining a digital sensor reception signal by A / D converting the sensor reception signal at a predefined noise scan frequency; a decimation circuit for determining a plurality of decimated digital sensor reception signals by performing integer decimation on the digital sensor reception signal using two or more different decimation rates, wherein each decimation rate corresponds to each candidate acquisition configuration of the sensor system; and a noise evaluation circuit for determining one or more noise indices for the plurality of candidate acquisition configurations by evaluating one or more of the plurality of decimated digital sensor reception signals. The method includes a configuration circuit for determining an acquisition configuration to be used for the operation of a sensor system from a plurality of candidate acquisition configurations using one or more noise measures, and the step of determining an acquisition configuration to be used for the operation of a sensor system among the candidate acquisition configurations comprises: a step of comparing one or more noise measures with a noise threshold; and, if the noise threshold is not satisfied by any of the noise measures, a step of increasing the scan time of at least one candidate acquisition configuration to acquire at least one updated candidate acquisition configuration; and a step of determining one or more updated noise measures for the at least one updated candidate acquisition configuration.A sensor circuit comprising the step of comparing one or more updated noise indices with the noise threshold. Claim 31 A capacitive touch sensing system comprising: one or more electrodes configured for capacitive sensing; and a sensor circuit according to claim 30, wherein the sensor circuit is connected to at least one of the one or more electrodes.

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