Method and system for determining a noise-robust acquisition configuration for operating a sensor system - Patents.com

Abstract

A system and method for determining a noise-robust acquisition configuration for a sensor or communication system is disclosed. An exemplary method includes a noise scan having the steps of acquiring a sensor receive signal from the sensor system, determining a digital receive signal from the sensor receive signal by A / D conversion of the sensor receive signal at a predefined noise scan frequency, determining a plurality of decimated digital receive signals by integer decimation of the digital receive signal using two or more decimation rates different from each other, each of the two or more decimation rates being associated with a respective candidate acquisition configuration, determining one or more noise metrics for a plurality of the candidate acquisition configurations using one or more of the plurality of decimated digital receive signals, and determining an acquisition configuration for operation of the sensor system from the candidate acquisition configurations using the one or more noise metrics.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 126,137, filed in the U.S. Patent and Trademark Office on December 16, 2020. The contents of the aforementioned patent application are incorporated herein for all purposes.

[0002] (Field) The present disclosure relates to methods and systems for determining a noise-robust acquisition configuration, and in particular for a sensor system. [Background technology]

[0003] This Background section is provided for the purpose of generally describing the background of the present disclosure. The work of the inventors, as well as aspects of this description that may not otherwise be admitted as prior art at the time of filing, are not admitted explicitly or implicitly as prior art to the present disclosure.

[0004] Sensor systems, sometimes referred to as "sensing systems", are known for a variety of applications. For example, capacitive touch sensor systems are used in the user interfaces of electronic devices such as computers, tablets, smartphones, and other electronic devices.

[0005] A capacitive touch sensor system may be realized, for example, by generating an alternating electric field and measuring the potential difference (i.e., voltage) acquired over one cycle at a sensor electrode in this 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, i.e., it is affected by an object such as a human finger or hand. Alternatively, the current (i.e., the movement of charge) flowing between the electrode and the sensor circuitry may be used to determine the capacitance between the sensor electrode and its electrical environment.

[0006] One problem with conventional systems that operate according to the above principles is that sources of electrical noise such as switched mode power supplies, fluorescent lighting, or wireless communications near the sensor can affect the electric field, and therefore estimating this voltage accurately and reliably in a noisy environment becomes problematic.

[0007] The inventors have determined that robustness to noise is a challenge for any sensor system, including capacitive touch sensing systems, and also for communication systems. In particular, passing standard International Electrotechnical Commission (IEC) noise tests, such as IEC 61000-4-6 amplitude modulated noise, bulk current injection (BCI) tests, such as ISO 11452-4 automotive standards, or robustness to squared noise, has been problematic in the past. Summary of the Invention

[0008] Based on the above, there exists a need to enable a noise-robust operation of a sensor system, e.g. a capacitive touch sensor system. This object is solved by the subject matter of the independent claims. The dependent claims and the following description contain various embodiments of the invention.

[0009] In one general exemplary aspect, a method is provided for determining a noise robust acquisition configuration for operation of a sensor system, the method comprising: 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 mutually distinct decimation rates, each of the two or more decimation rates being associated with a respective candidate acquisition configuration; determining one or more noise metrics for a plurality of the candidate acquisition configurations using one or more of the plurality of decimated digital received signals; and determining an acquisition configuration for operation of the sensor system from the candidate acquisition configurations using the one or more noise measures.

[0010] In general and another exemplary embodiment, a sensor circuit is provided for determining an acquisition configuration for operation of a sensor system, the sensor circuit comprising: a sensor interface for acquiring a sensor received signal from the sensor system; an A / D converter for 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; a decimation circuit configured to determine a plurality of decimated digital received signals by integer decimation of the digital received signal using two or more mutually different decimation rates, each of the two or more decimation rates being associated with a respective candidate acquisition configuration; a noise estimation circuit configured to determine one or more noise metrics for more than one of the acquisition configurations using one or more of the plurality of decimated digital received signals; and a configuration circuit configured to determine an acquisition configuration for operation of the sensor system from candidate acquisition configurations using the one or more noise measures.

[0011] In general and another exemplary aspect, a capacitive touch sensing system is provided, the capacitive touch sensing system comprising: one or more electrodes configured for capacitive sensing; The sensor circuit of any of the previous aspects further comprises a sensor circuit connected to at least one of the one or more electrodes.

[0012] In general and another exemplary aspect, a method for determining a noise robust acquisition configuration for operation in a communication system is provided, the method comprising: obtaining a received signal from a communication system; determining a digital received signal from the received signal by A / D conversion of the 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 mutually distinct decimation rates, each of the two or more decimation rates being associated with a respective candidate acquisition configuration; determining one or more noise metrics for more than one of the acquisition configurations using one or more of the plurality of decimated digital received signals; and determining an acquisition configuration for operation of the communication system from the candidate acquisition configurations using the one or more noise measures.

[0013] In general and another exemplary aspect, a communications circuit for determining an acquisition configuration for operation of a communications system is provided, the communications circuit comprising: a communication system interface for acquiring a received signal from the communication system; an A / D converter for determining a digital received signal from the received signal by A / D conversion of the received signal at a defined noise scan frequency; a decimation circuit configured to determine a plurality of decimated digital receive signals by integer decimation of the digital receive signal using two or more mutually different decimation rates, each of the two or more decimation rates being associated with a respective acquisition configuration; a noise estimation circuit configured to determine one or more noise metrics for more than one of the acquisition configurations using one or more of the plurality of decimated digital received signals; and a configuration circuit configured to determine an acquisition configuration for operation of the communication system from the candidate acquisition configurations using the one or more noise metrics.

[0014] The 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 description of the drawings]

[0015] [Figure 1] 1 illustrates a schematic block diagram of a first exemplary embodiment of a sensor circuit; [Diagram 2] 1 illustrates in schematic form an exemplary embodiment of a capacitive touch sensing system. [Diagram 3] 2 illustrates the functioning of the sensor circuit of FIG. 1 in an exemplary flow diagram according to a first embodiment. [Figure 4] 2 shows a schematic diagram of the functioning of a decimation circuit of the sensor circuit of FIG. 1; [Diagram 5] 2 shows a schematic of two signal processing chains for noise and SN scans. [Figure 6] 2 illustrates the functioning of the sensor circuit of FIG. 1 in an exemplary flow diagram according to a second embodiment. [Figure 7] 1 illustrates an example magnitude of the transfer function of an ideal ADC in a schematic diagram. [Figure 8A] 2 illustrates the functionality of the sensor circuit of FIG. 1 in an exemplary flow diagram according to a further embodiment. [Figure 8B] 2 illustrates the functionality of the sensor circuit of FIG. 1 in an exemplary flow diagram according to a further embodiment. [Figure 9] Shows spectral noise suppression using a digital LPF. [Figure 10] 2 illustrates the functionality of the sensor circuit of FIG. 1 in an exemplary flow diagram according to another embodiment. [Figure 11] 1 shows a basic exemplary diagram and corresponding timing diagram for charge measurement using current integration. [Figure 12] 13 shows another exemplary diagram for charge measurement using two current integrators along with a corresponding timing diagram. [Figure 13] 1 illustrates a schematic of two slices of an exemplary analog front-end (AFE) of a touchscreen controller. [Figure 14] FIG. 13 shows an example timing diagram for current integration and integrator reset with slice independent control of aperture and reset switches. [Figure 15] FIG. 13 shows an example timing diagram for current integration and integrator reset without slice independent control of aperture and reset switches. [Figure 16] 16 shows data acquired using the timing arrangement of FIG. [Figure 17] 4 shows the spectral noise suppression by the digital LPF for two packet lengths. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Specific embodiments of the present invention are described in detail below. In the following description of the embodiments of the present invention, specific details are described in order to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known features have not been described in detail in order to avoid unnecessarily complicating the present description.

[0017] In the following description, the terms "connected to" or "connected with" are used to indicate a data or signal connection between at least two components, devices, units, processors, circuits, or modules of the invention according to the described embodiments. Such connections may be direct connections between the respective components, devices, units, processors, circuits, or modules, or may be indirect, i.e., through intermediate components, devices, units, processors, circuits, or modules. Connections may be permanent or temporary, wireless or conductor-based, digital or analog.

[0018] In the following description, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives to elements (i.e., any noun in this application). The use of ordinal numbers does not imply or create any particular ordering of the elements, nor does it limit any element to only a single element, unless expressly disclosed, such as by use of the terms "before," "after," "single," and other such terminology. Rather, the use of ordinal numbers is to distinguish between similarly named elements. For example, a first element is distinct from a second element, a first element can encompass more than one element, and can succeed (or precede) a second element in the order of elements.

[0019] In many applications, sensor systems are used. For example, today's electronic devices, such as smartphones, laptops, tablets, wearables, are unthinkable without a touch screen, which generally uses capacitive or resistive touch sensor systems. Current developments are leading to the use of touch panels in more complex systems, such as automobiles, aircraft, or industrial equipment.

[0020] Robustness to noise is a key issue for any such sensor system, as mentioned above. A particular problem with capacitive touch screens is that they, by design, face the user and must be constructed such that the electric fields they employ can be affected by the proximity of, for example, the user's hand or finger. This makes these types of touch screens particularly vulnerable to noise from the ambient field.

[0021] Furthermore, as the inventors have recognized, there is no reliable means to determine the expected signal-to-noise ratio (hereinafter "SNR") for a given sensor and configuration, leading to insufficient output SNR or wasted resources, such as acquisition time. For customers of touch sensing systems (e.g., smartphone manufacturers), it is important to have a high touch reporting rate with reliable and accurate output estimates. Touch reporting rate, as used herein, refers to the rate at which a touch controller transfers estimates of (x,y) position to a host controller.

[0022] Some influencing factors affecting the noise robustness of a sensor system are, for example, the operating frequency (in the case of a capacitive sensor system, the operating frequency of the so-called "stimulus signal") and associated one or more of the sampling frequency of the A / D conversion, the scan period, and the selection of the low-pass filter coefficients. In the context of this paper, the set of configurable parameters of the sensor system that affect these influencing factors is understood as the "acquisition configuration" or "data acquisition configuration" (hereinafter also referred to as "AC" for simplicity) of the sensor system. In some embodiments, the acquisition configuration comprises at least one or more of the following parameters: the sampling frequency for the A / D conversion, the operating frequency (carrier frequency) of the stimulus signal for the (acquisition) operation of the sensor system, the scan period, the number of samples to acquire, the "packet length", and the low-pass filter coefficients. Different ACs differ in one or more of these parameters. These parameters can be used to configure the "analog front-end" of the sensor control circuitry as well as the digital processing.

[0023] The received signal of a communication or sensing system is usually a mixture of actual information that needs to be received and evaluated, and noise. This information can be, for example, a measure of the capacitance or distance between the sensor electrode and the user's finger. In the case of additive noise, the received signal is simply the sum of information and noise. Typically, the information part cannot be easily extracted from the received signal, since both the information and noise parts are unknown, which is comparable to one equation with two unknowns that cannot be uniquely solved. However, it is possible to estimate the amount of information from a noisy received signal while assuming properties about the information, the noise, or both, such as "information varies slowly over time". The less noise there is, the more accurate the resulting estimate will be, i.e., the smaller the uncertainty of the estimate. It is therefore desirable to employ an acquisition configuration that is almost noiseless, e.g., an acquisition configuration that exhibits less noise in the resulting estimate compared to another acquisition configuration.

[0024] It is possible to perform test measurements using the sensor system and to calculate from the measurement data a noise metric representative of the amount of noise. Such test measurements are referred to in the present context as "noise scans".

[0025] A noise scan may be performed for different candidate ACs, and the AC that produced the least amount of noise may be selected given the respective determined noise. A measurement where the received signal contains both the desired information and noise will be called a signal-and-noise scan, or "SN scan". During a SN scan, the sensor or communication system may need to generate and transmit a stimulus signal to excite an alternating electric field and obtain the information portion at the receiving end. From the data acquired during the noise scan, an estimate of the amount of noise expected during a SN scan for a predefined candidate AC may be calculated. Such an estimate is referred to herein as a "noise estimate". The ACs for which a noise estimate is calculated from noise scan data acquired during one noise scan may differ at least in their operating frequency and sampling frequency, which are considered as parameters of the analog front end of the sensor system.

[0026] In the present context, a "stimulation signal" or simply "stimulation" is understood as an actively controlled movement of charge between an electrode and a sensor circuit, e.g., a chip, for driving the potential of the electrode to a given target value or signal. In some embodiments, this target value or signal is specified before the stimulation is started. For example, if the target signal is a rectangular pulse train with a given pulse frequency, this pulse frequency is selected before driving the potential of the electrode to this target signal.

[0027] 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 mentioned above, also called the "carrier frequency". In some embodiments, the stimulus signal alternately settles at high and low signal levels once during the carrier signal period. At the receiving side, 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, in some embodiments, sampling may be performed at twice the carrier frequency. Demodulation may be performed in some embodiments by alternating multiplication of the A / D converted samples by plus one and minus one.

[0028] Based on the above, a need addressed by embodiments of the present invention is to select a suitable AC from a set of candidate ACs, for example to achieve a high touch report rate with reliable and accurate output estimates.

[0029] Basic exemplary concepts of the present invention include: a) the concept of base and sub-frequency that allows processing the same sequence of noise scan measurement data in different ways, or more precisely, with different parameters, to obtain reliable noise (power) estimates for multiple ACs (e.g., with respect to carrier frequency and scan time); and b) a robust noise measure that provides an accurate estimate for the true noise power of the SN scan measurement data after demodulation and low-pass filtering.

[0030] According to a first exemplary aspect, a method for determining a noise robust acquisition configuration for operation of a sensor system includes, in a noise scan, determining: 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 decimation rates different from one another, the two or more decimation rates being associated with respective candidate acquisition configurations; determining one or more noise metrics for a plurality of the candidate acquisition configurations using one or more of the plurality of decimated digital received signals; and determining an acquisition configuration for operation of the sensor system from the candidate acquisition configurations using the one or more noise measures.

[0031] The sensor system of the present aspect may be of any suitable type, including, but not limited to, a sensor system for detecting and measuring 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, such as for a touch screen display. For example, the sensor system may be a non-contact sensor system.

[0032] In some embodiments, the methods of the present aspect are performed using sensor circuitry, e.g., a sensor circuitry that includes a control unit, such as a microcontroller and / or microprocessor with suitable programming. Alternatively or additionally, the sensor circuitry may include dedicated circuitry that provides at least some of the functionality of the methods of the present exemplary aspects.

[0033] As mentioned above, the noise scan of this aspect may be considered as a test measurement to determine, for example, the effect of noise on the respective sensor system. In some embodiments, the measurement data acquired during the noise scan does not include any information, only noise, i.e., the sensor received signal during the noise scan is acquired without a stimulus signal being applied to the sensor system.

[0034] The (sensor) received signal (i.e., the signal received, measured or acquired during a noise or SN scan) may be, for example, a current flowing between an electrode and a sensor circuit, i.e., a movement of charge, a current integrated over a certain time interval, or a potential or voltage of an electrode relative to a reference potential. The sensor received signal may be obtained from the sensor system by any suitable means, for example by a corresponding conductive connection.

[0035] This received signal may be affected by stimuli during use, possibly modified by environmental factors such as a human finger, and in most circumstances affected by environmental noise sources. In addition to these environmental or external influences, there may be analog pre-processing in the sensor circuitry, which may add further internal noise to the received signal, such as 1 / f noise or quantization noise of the A / D converter. Robustness against noise from internal sources can usually be addressed during system design, but environmental noise sources are at least to some extent unknown at design time. The methods and systems described herein address robustness against external noise. Ignoring internal noise, any change in the received signal, i.e. any change in any current or potential, is caused by this external noise of interest.

[0036] According to a first exemplary aspect, the method includes 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. The A / D conversion may be performed using any suitable method, for example, but not limited to, a flash A / D converter, an integrating 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 balance A / D converter, a dual slope A / D converter, a delta coding A / D converter, a pipelined 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 an analog front-end setup with a suitable A / D converter. The A / D conversion is performed at a predefined noise scan frequency, which may be set depending on the application. In some embodiments, the noise scan frequency is significantly higher than the operating frequency of the stimulus signal during 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 3 to 40 times the operating frequency. In some embodiments, the noise scan frequency is set to 3 to 4 times the operating frequency.

[0037] 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 during the noise scan compared to the SN scan, which reduces the time available for analog processing of the A / D converted samples of the received input signal. As a result, the timing of the analog processing desired for the SN scan cannot be applied to the noise scan due to the reduced time between A / D conversions. In the following, embodiments are described using a specific ratio of the aperture time of the noise scan to the aperture time of the SN scan.

[0038] According to a first exemplary aspect, a method includes determining a plurality of decimated digital received signals by decimating the digital received signal by an integer multiple using two or more mutually distinct decimation rates.

[0039] In other words, after A / D conversion, i.e., in the digital domain, the digital received signal is then 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 a respective candidate acquisition configuration. In some embodiments, the two or more decimation rates are multiples of two, e.g., 2 and 4. In some embodiments, the decimation rates are more than two. rate is used.

[0040] Two or more decimation rates are associated with respective candidate acquisition configurations, for example in view of the different sampling rates that result upon application of the different decimation rates.

[0041] According to this aspect, one or more noise metrics for a plurality of candidate acquisition configurations are determined using one or more of the plurality of decimated digital received signals. An acquisition configuration for operation of the sensor system is then determined from the candidate acquisition configurations using the one or more noise metrics.

[0042] As is evident from the above, the method according to the first aspect allows for determining a plurality of decimated digital received signals using the same measurement data of the sensor received signal. Since two or more decimation rates are used, the plurality of decimated digital received signals correspondingly have 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. the "candidate AC", the described method thus allows for example to use the same measurement data for testing a plurality of different candidate ACs.

[0043] In some embodiments, oversampling is performed during the noise scan, and then a decimation rate for decimating the noise scan signal may be selected such that, for example, the decimated sampling rate is equal to the SN scan sampling rate to provide the same aliasing (of the noise) as in the SN scan.

[0044] In contrast to other known approaches, the teachings herein provide, at least in some embodiments, a complete solution for noise robustness, as well as a solution for identifying the relatively best carrier frequency. Determination of one or more noise measures for different AC from the same measurement data provides robustness against, for example, AM noise and squared noise. This method is also inherently fast, saving measurement time. In some embodiments, the method further allows for finding a trade-off between touch report rate and output SNR.

[0045] As mentioned above, the method of the first exemplary aspect includes determining one or more noise measures for a plurality of the (two or more) candidate acquisition configurations from one or more of the plurality of decimated digital received signals. The determination of the noise measures may be performed, for example, in the digital domain. In some embodiments, one or more noise measures are determined for each of the candidate acquisition configurations, thereby enabling a comparison of different candidate ACs. In some embodiments, a noise measure is calculated for each decimation rate from at least one decimated digital received signal associated with the respective decimation rate. In some embodiments, a noise measure is calculated for each decimation rate from the plurality of decimated digital received signals. This method is described in more detail below.

[0046] The noise metric may be of any suitable type for obtaining a comparable measure of noise, for example, the noise metric may typically be a numerical value that quantifies the noise level present in at least one of the multiple decimated digital received signals.

[0047] The noise measure in some embodiments may be a power measure, such as obtained by effective noise power estimation (ENPE), but may also be, for example, but not limited to, the square root of the power measure or another linear measure, i.e., a quantity calculated from the input data using only linear functions. In some embodiments, the noise measure is a phase instantaneous noise measure. For example, as discussed in U.S. Patent No. 10,151,608 (B2), which is incorporated herein for all purposes, there are also approaches in which the noise measure is a score value, with a higher score indicating a lower noise level of the SN scan.

[0048] In some embodiments, the stimulus is present during the scan for acquiring data for calculating the noise metric, i.e., during a noise scan. Measurement data acquired during this type of scan is likely to be affected by, for example, a human finger in the vicinity of the sensor, but can still be used to provide a sufficiently good decision basis for identifying a suitable AC. With this in mind, the term "power measure" may be used interchangeably with the term "noise measure" in some embodiments.

[0049] According to a first exemplary aspect, once one or more noise metrics are determined, an acquisition configuration for operation of the sensor system is determined from the given candidate acquisition configurations. The determination is based on the one or more noise metrics. As discussed in more detail below, and in some embodiments, the determination may be influenced by further considerations, such as, for example, a minimum scan time (also referred to as "scan duration").

[0050] In some embodiments, determining the acquisition configuration includes selecting a preferred noise measure from one or more noise measures, and the acquisition configuration is set to correspond to a candidate acquisition configuration associated with the preferred noise measure.

[0051] In some embodiments, the preferred noise measure is selected based on predefined criteria, for example based on a predefined threshold of maximum noise.

[0052] In some embodiments, the preferred noise measure results in the lowest noise level of one or more noise measures. In other words, in these embodiments, the preferred noise measure can also be called the "best" noise measure, and the best noise measure is understood as the noise measure whose amount shows the lowest noise level compared to all other noise measures in a given comparison set of noise measures. For example, if the noise measures are determined by ENPE, the best noise measure will have the lowest value, and according to the disclosure of US Patent No. 10151608 (B2), it will have the highest value.

[0053] In some embodiments, for each of the two or more decimation rates, a corresponding group of decimated digital receive signals (i.e., a group of two or more decimated digital receive signals) is determined as part of determining the plurality of decimated digital receive signals. Thus, and in view of the two or more decimation rates, in accordance with the present embodiments, at least two groups of decimated digital receive signals are provided, with group "members" of a group sharing the same decimation rate.

[0054] In some embodiments, each decimated digital receive signal of a given group is different from every other decimated digital receive signal of that given group. The groups of decimated digital receive signals may differ from each other in any suitable manner. The groups of decimated digital receive signals may have the same or different numbers of samples.

[0055] In some embodiments, the decimated digital received signals in each group may differ from each other at least, but not limited to, by having different starting phases. This embodiment allows for a further improvement in the determination of noise, as will become clear from the following description. The term "start phase" with respect to a digital signal is understood as the delay of the first sample of the decimated signal relative to the first sample of the digital received signal, typically a delay in units of samples at the sampling rate of the received signal. Different starting phases for two signals therefore refer to the two signals having different starting samples.

[0056] As is obvious, in a given group of decimated digital received signals, not all possible starting phases need to be represented. For example, for each of at least two decimation rates R(0,j), the digital received signal x may be decimated to a subset of starting phases v=v0, v0+dv, v0+2dv,...,R(0,j)-1, where j=0,1,... is denoted as a sub-frequency index. In other embodiments, the 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 may be decimated to 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), a group would consist of four corresponding decimated digital received signals having 6 samples, each signal starting with a different starting phase for a total of four possible starting phases. Although each of the decimated digital received signals of a group would contain only every fourth sample due to the phase shift of certain samples, all samples would still be represented within the group, resulting in an improved noise measure.

[0057] In some embodiments, the one or more noise measures are determined by an effective noise power estimate (ENPE), which includes a determination of a (e.g., normalized) sum of phase instantaneous noise measures over each of the decimated digital received signals of one of the groups of decimated digital received signals. In some embodiments, the effective noise power estimate is performed for all groups, i.e., for all decimation rates. The determination of the sum of the phase instantaneous noise measures may be performed by any suitable method. In some embodiments, the phase instantaneous noise measure is the sum of (all) samples of the decimated digital received signals weighted with coefficients from a coefficient vector. For example, the coefficient vector may be a vector containing coefficients of a low-pass filter, e.g., the coefficients of a boxcar window (all ones) or a Hann (or Hanning) window of a desired length. Such normalization of the sum term may be performed, for example, by dividing the sum term by the sum of all coefficients in the coefficient vector. This normalization does not have to be performed directly on the weighted sum terms, but can also be performed at a later processing stage, for example after the summation of the phase instantaneous noise measures, which can reduce computational complexity.

[0058] For example, to calculate the ENPE for a given decimation rate, a dot product with an assigned coefficient vector is calculated for each decimated digital received signal of a given group. In some embodiments, these dot products are normalized by dividing by the sum of all the coefficients. The average of the normalized squared dot products can then be calculated to obtain the ENPE.

[0059] In some embodiments, determining an acquisition configuration from the set of candidate acquisition configurations includes selecting a candidate acquisition configuration that has the shortest scan time while the noise metric satisfies a (predefined) noise threshold, which provides a particularly high touch report rate since the shortest available scan time is employed.

[0060] It should be noted that the context of comparing a noise measure to a noise threshold is understood to encompass the alternative of comparing an expected output signal-to-noise ratio (SNR) to a (predefined) SNR threshold, which may be calculated from a priori determined signal power and noise measure determinations, as explained above.

[0061] In some embodiments, the step of determining an acquisition configuration from the set of candidate acquisition configurations further includes comparing the one or more noise measures to a noise threshold, and if the noise threshold is not met by any of the one or more noise measures, increasing a scan time of at least one of the candidate acquisition configurations to obtain at least one updated candidate acquisition configuration, determining one or more updated noise measures for the at least one updated candidate acquisition configuration, and comparing the one or more updated noise measures to the noise threshold.

[0062] This embodiment allows for incremental evaluation of candidate acquisition configurations by increasing the scan time if none of the original candidate acquisition configurations meets the desired noise threshold, which can be set, for example, according to the respective application. Correspondingly, in some embodiments, the described steps can be repeated until an acquisition configuration that meets the noise threshold is found. If multiple candidate acquisition configurations that meet the threshold are found in a given iteration, in some embodiments, the candidate acquisition configuration is selected as the acquisition configuration for system operation that has the lowest noise level for the scan time of the given iteration. 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 operating frequency and sampling frequency, but different coefficient vectors.

[0063] In some embodiments, the scan time is increased by substantially an integer multiple of the scan time of the original / previous candidate acquisition configuration. These embodiments are particularly useful for reducing noise. In some embodiments, "substantially an integer multiple" refers to approximately

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[0064] To increase the scan time, in some embodiments, a new noise scan may be performed with a correspondingly increased scan time to obtain at least one updated candidate acquisition configuration.

[0065] In other embodiments, during the step of acquiring the sensor received signal from the sensor system, it is possible to acquire the sensor received signal at a maximum scan time and to initially consider only a portion of it. For example, in some embodiments, after A / D conversion is performed, only a portion of the sensor received signal, i.e. at a minimum scan time, is further processed while the original sensor received signal is stored and forms the basis for the discussed decimation. In these embodiments, it is possible to "increase" the scan time by later using a longer portion of the stored copy of the original sensor received signal, i.e. by increasing the scan time. In some embodiments, the maximum scan time may be four times the minimum scan time.

[0066] In some embodiments, a predefined minimum output report rate of the sensor system may be given, or conversely, a maximum duration of a scan cycle (i.e., the continuous operation of one or more noise scans and SN scans) during which each measurement data is acquired may be given. This time available for a scan cycle is distributed across all individual measurements made during the scan cycle, including the noise scan and ancillary measurements such as at least one SN scan. For example, a maximum scan time T can be obtained for one individual measurement of an SN scan. Sampling frequency f s is given to AC, for example, f s =2 f c is the operating frequency or carrier frequency f c It is twice as much as

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[0067] In some embodiments, and where a finite input response (FIR) low pass filter is employed to process the acquired data, the filter length may be set to L since a single output value for data acquired during scan time T may be desired, as well as to utilize all of the acquired data while still requiring stability of the low pass filter output. A vector of low pass filter coefficients may be selected to control the spectral suppression of the filter in some embodiments, for example. For example, the first element of the vector may be a less positive value than the middle element 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, a Hanning window of length L may be selected as the vector of low pass filter coefficients. The nth element of the Hanning window, as defined by Mathworks, is:

number

[0068] In some embodiments, the sensor system is operated during an SN scan using the acquisition configuration of the most recent noise scan, with the view that the acquisition configuration of the most recent scan represents the most recent configuration for the current noise scenario. In some embodiments, the SN scan is followed by a further noise scan. The resulting cyclic operation may be repeated until sensing operation of the sensor system ceases in some embodiments, such as when the sensor system is powered off.

[0069] In some embodiments, the method includes performing multiple subsequent noise scans between the two SN scans, the multiple noise scans using predefined noise scan frequencies, and at least some (or, for example, all) of the multiple noise scans differing from each other in the predefined noise scan frequencies. This embodiment allows for further improving the determination of a noise-robust acquisition configuration, especially when candidate acquisition configurations that do not share a common multiple are to be evaluated.

[0070] For example, an overall acquisition configuration for operation of the sensor system can be determined from acquisition configurations acquired during multiple subsequent noise scans. In other words, a "preferred" or "best" overall acquisition configuration can be determined from multiple acquisition configurations acquired in each run of a noise scan. In some embodiments, an overall acquisition configuration can be determined from a group of acquisition configurations determined during multiple noise scans by comparing associated noise metrics and / or respective scan times.

[0071] Alternatively, in some embodiments, during a scan cycle, it is possible to perform noise scans consecutively for, for example, only two (or a different number) predefined noise scan frequencies, keeping the one that results in the best AC, while circularly looping through the remaining candidate noise scan frequencies to select the second one.

[0072] In some embodiments, the aperture time of the A / D conversion for determining the acquisition configuration (i.e. during the noise scan) is set to be substantially the same as or an integer fraction of the aperture time of the SN scan. That is, for the SN scan, an aperture time is predefined or selected as desired according to the respective application (e.g. in terms of touch report rate), and the aperture time for the A / D conversion during the noise scan is set accordingly, i.e. the same as 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 during which an analog signal is input to the measurement system, i.e. the measurement system is exposed to the outside world and thus its internal analog state is altered by the analog input signal. In some embodiments, the aperture time is related to the time when the sensor receive signal is input to the sensor interface of the sensor circuit, which will be discussed below. In some embodiments, the aperture time is related to the time when the sensor receive signal is input to the A / D converter of the sensor circuit, which will be discussed below.

[0073] When the noise scan aperture time is the same as the SN scan aperture time, it is possible to guarantee that it will result in the relative best carrier frequency determination. If 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 optimal carrier frequency, although an absolute effective noise power estimate is not possible.

[0074] As the inventors have determined, it is possible to guarantee that a certain ratio between the SN scan aperture time and the noise scan aperture time will result in the relative best carrier frequency determination, where the noise scan aperture time is either a) the same as the SN scan aperture time or b) an integer fraction of the SN scan aperture time, or correspondingly, an integer multiple of the noise scan aperture time.

[0075] In some embodiments, a fundamental frequency index i is(i) About) Duration

number

[0076] In some embodiments, the method steps are performed at least in part by sensor circuitry for the sensor system. In some embodiments, a (e.g., non-transitory) computer-readable medium is provided having content configured to cause the sensor circuitry to perform the method steps as described herein.

[0077] According to another aspect, there is provided a sensor circuit for determining an acquisition configuration for operation of a sensor system, the sensor circuit comprising: a sensor interface or input for acquiring a sensor receive signal from the sensor system; an A / D converter for 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; a decimation circuit configured to determine a plurality of decimated digital received signals by integer decimation of the digital received signal using two or more mutually different decimation rates, each of the two or more decimation rates being associated with a respective candidate acquisition configuration; a noise assessment circuit configured to determine one or more noise metrics for a plurality of the candidate acquisition configurations using one or more of the plurality of decimated digital received signals; and a configuration circuit configured to determine an acquisition configuration for operation of the sensor system from candidate acquisition configurations using the one or more noise measures.

[0078] In some embodiments, the sensor circuit according to the present aspect is configured according to one or more of the embodiments previously discussed with respect to the preceding aspects. Regarding the terms used and their determination, reference is made to the preceding aspects.

[0079] According to another aspect, a capacitive touch sensing system (capacitive sensor) is provided. The capacitive touch sensing system of this aspect comprises: one or more electrodes configured for capacitive sensing; and a sensor circuit connected to at least one of the electrodes, the sensor circuit comprising: a sensor interface or input for acquiring a sensor receive signal from one or more electrodes; an A / D converter for 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; a decimation circuit configured to determine a plurality of decimated digital received signals by integer decimation of the digital received signal using two or more mutually different decimation rates, each of the two or more decimation rates being associated with a respective candidate acquisition configuration; a noise assessment circuit configured to determine one or more noise metrics for a plurality of the candidate acquisition configurations using one or more of the plurality of decimated digital received signals; and a configuration circuit configured to determine an acquisition configuration for operation of the sensor system from candidate acquisition configurations using the one or more noise measures.

[0080] In some embodiments, the sensor circuit according to this aspect is configured according to one or more of the embodiments previously discussed with respect to the preceding aspects. With respect to the terms used and their determination, reference is made to the preceding aspects. The term "capacitive touch sensing system" as used herein is understood to include, for example, non-contact sensor systems based on proximity detection.

[0081] Reference is now made to the drawings in which the various elements of the embodiments are given numerical designations and in which further embodiments are discussed.

[0082] In the exemplary embodiments, the components of the described embodiments each represent individual features which should be considered independently of one another, both in the combination as shown or described and in combinations other than those shown or described. In addition, the described embodiments can be supplemented by features of the invention other than those described.

[0083] Fig. 1 shows in a schematic block diagram a first exemplary embodiment of a sensor circuit 1. The sensor circuit 1 is adapted to operate a sensor system or a communication system (neither of which is shown in Fig. 1). For example, a sensor 20 of a capacitive touch sensing system 21 as shown diagrammatically in Fig. 2 may be connected to the sensor circuit 1. It is emphasized that the invention is not limited to capacitive touch sensing systems, but in the present description reference is made to the capacitive touch sensing system 21.

[0084] The exemplary sensor circuit 1 of the embodiment of Figure 1 may be embodied by a microcontroller having hardware / software providing the following operations and components. For greater clarity, the microcontroller itself is not shown in the schematic block diagram of Figure 1.

[0085] Sensor circuit 1 comprises a sensor interface 2 connectable to a sensor 20 of a capacitive touch sensing system 21 using sensor connections 3. Capacitive touch sensing is known for use in, for example, but not limited to, capacitive touch panel panels of electronic devices such as computers, tablets, smartphones, wearables, and smart home devices, electronic components for vehicles, trains, ships, aircraft / spacecraft, and industrial or scientific equipment. In one embodiment, capacitive touch sensing system 21 is a "touchless" sensor system.

[0086] The sensor interface 2 and the sensor connections 3 allow the sensor circuit 1 to operate / drive the sensor 20 of the capacitive touch sensing system 21 during an acquisition operation, referred to herein as a "signal and noise scan", or SN scan. During an SN scan, the sensor circuit 1, or more precisely the driver circuit 4 of the sensor circuit 1, creates and transmits a stimulus signal to excite an alternating electric field near the sensor 20 of the capacitive touch sensing system 21, which then results in an information portion at the receiving side, i.e. for capacitive touch sensing, whether one or more fingers of a user or different objects have been detected near the surface of the sensor 20. Both the transmission of the stimulus signal and the reception of the return sensor reception signal are handled by the sensor interface 2. For the purposes of this description 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.

[0087] 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 stimulation signal is applied to the sensor by the sensor circuit 1.

[0088] The noise scan, as explained above, serves as a test measurement and allows the calculation of a noise metric from the measurement data acquired during the noise scan, which represents the amount of noise expected during the SN scan. Robustness against noise is an important issue for any communication or sensor system including the capacitive touch sensing system 21. In particular, passing standard IEC noise tests with amplitude modulated noise, e.g. IEC 61000-4-6, Bulk Current Injection (BCI) tests, e.g. ISO 11452-4 automotive standards, or robustness against squared noise are addressed. Furthermore, for various applications of the capacitive touch sensing system 21, it is important to provide a high touch reporting rate with reliable and accurate output estimates.

[0089] The purpose of performing a noise scan is to determine an acquisition configuration for operation of capacitive touch sensing system 21 during an SN scan. The acquisition configuration comprises one or more parameters for operation of capacitive touch sensing system 21 during an SN scan and may comprise one or more of a sampling frequency for A / D conversion, an operating frequency (carrier frequency) of a stimulus signal for (acquisition) operation of the sensor system, a scan duration, a number of samples to acquire, and low pass filter coefficients.

[0090] It should be noted that in this description, the sampling frequency for A / D conversion during 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 quasi-static signal, i.e. a signal that does not change or hardly changes over time during a given time interval in terms of the stimulus signal in the form of a rectangular pulse train. On the receiving or sensing side, when the signal undergoes low-pass filtering, as described below, its edges are rounded and after each edge the signal exhibits a transition period until it settles to a constant level. Here, the received signal is sampled once after each edge when the signal is sufficiently stable. That is, during SN scan, there are two samples per period of the rectangular pulse train, which corresponds to a sampling frequency of twice the carrier frequency.

[0091] The sensor circuit 1 further comprises an A / D converter 5, a digital signal processing circuit 15, a noise estimation circuit 8, a configuration circuit 9, a memory 10, a touch detector 11 and an output 12. The digital signal processing circuit 15 comprises in particular a decimation circuit (not shown in FIG. 1) configured to determine a plurality of decimated digital received signals, as will be explained in more detail below. It is noted that FIG. 1 does not show all the control connections between the aforementioned components, for example for controlling the sampling rate of the A / D converter 5 or the access of the memory 10 by the signal processing circuit 15.

[0092] During a noise scan, the signal processing chain consisting of the A / D converter 5, the digital signal processing circuit 15, the noise evaluation circuit 8 and the configuration circuit 9 is in an active state.

[0093] During an SN scan, the noise evaluation circuit 8 and the configuration circuit 9 are disabled, i.e. inactive. In this case, the sensor received signal, after A / D conversion and signal processing, is provided to the touch detector 11 for determining the user's touch on the sensor 20. The result is provided to a connected external component via an output 12.

[0094] The function of the sensor circuit 1 and its components will now be described with reference to the flow diagrams of FIG. 1 and FIG.

[0095] For ease of explanation, the exemplary capacitive touch or touchless sensing system 21 has multiple acquisition configurations whose analog front-end parameters are equal except for the operating frequency and the respective sampling frequency, the latter of which is assumed to be twice the carrier frequency in this exemplary embodiment as described above. The different sampling frequencies have a common multiple, which is a predefined noise scan frequency. Other digital signal processing parameters such as the number of samples filtered and the selection of low pass filter coefficients may or may not differ between these ACs.

[0096] In step 30, a noise scan is initiated by initializing / powering up the sensor circuit 1. In step 31, the sensor received signal is acquired from the sensor 20 using the sensor interface 2, as described above, without any stimulus signal being applied. Thus, the signal consists of noise only.

[0097] Subsequently, in step 32, the sensor received signal is A / D converted using A / D converter 5 to obtain a digital sensor received signal. During the noise scan, data is collected at a frequency f bDuring the configuration step (not shown), b is chosen to be a common multiple of the SN scan sampling frequencies of multiple ACs. If one of these ACs is, for example, a candidate carrier frequency f c During this SN scan using AC, the sampling frequency is f c =2 f c However, the predefined noise scan frequency is R times higher, i.e., f b = R 2 f c where R is the decimation rate. Therefore, the A / D converter 5 operates at a sampling frequency of f b =2 R f c During the noise scan, the analog sensor received signal is sampled at , i.e., the sampling frequency is R times higher than in the SN scan.

[0098] In step 33, a decimated digital receive signal is generated by a decimation circuit in the digital signal processing circuit 15 from the digital sensor receive signal.

[0099] Decimation of the digital sensor receive signals reduces the number of samples in each decimated digital receive signal. Figure 4 shows a schematic of the operation of the digital signal processing circuit 15 for example decimation rates R = 2, 3, 4, and 6.

[0100] The decimation uses a number of different decimation rates, namely decimation rates R=2, 3, 4, and 6, as shown in Figure 4. For each decimation rate, a number of decimated digital received signals are provided, which will be described in more detail below.

[0101] By applying decimation by multiple decimation rates, multiple possible "candidate" acquisition configurations can be evaluated from the same measurement data, i.e., digital sensor receive signal. As mentioned above, the (candidate) acquisition configurations in this embodiment have sampling frequencies that are common multiples of the sampling frequency of the noise scan. The low pass filter length and coefficient values ​​may be different in some examples as well. Decimating the noise scan digital sensor receive signal by multiple decimation rates provides decimated digital receive signals with these different sampling frequencies, thus making it possible to evaluate different candidate acquisition configurations using the same sensor receive signal. As is evident from the example of FIG. 4, the scan duration is constant (i.e., L (i) = 24 samples), but the number of samples in the decimated digital received signal for each AC packet length is equal to the packet length L. The number of samples in the decimated digital received signal varies depending on the decimation rate. In some embodiments, the scan duration for different ACs may be different. For example, if a noise scan results in a total of 20 samples, R=4 is 4. * 5=20 samples, but with R=3, 3 * 3 because 7=21 does not "fit" into the original sample length of 20 * There will be only 6=18 samples.

[0102] Once the decimated digital received signal is generated, in step 34 the digital signal processing circuit 15 demodulates the decimated digital received signal. This is done by alternating multiplication of the samples with plus and minus one, which may also be done during the SN scan, but is not limited to this specification. After demodulation, unwanted high frequency signal components are removed using digital low pass filtering, for example one or more finite impulse response (FIR) filters. It should be noted that different decimation rates R may require differences in further processing. In particular, the number of filter coefficients of the FIR filter is proportional to the number of samples after decimation.

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[0103] After filtering,

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[0104] The evaluation is performed in step 35 by a noise evaluation circuit 8 which determines the noise countermeasures of candidate acquisition configurations from the decimated digital received signal.

[0105] As mentioned above, for each decimation rate, a group of decimated digital received signals is determined. For example, as shown in FIG. 4, in the top part of the figure, L (i) = 24 samples x k , k=0,1,...,23. Below that is the original ADC 5 output signal with decimation rates R=2,3,4,6, with different starting samples x νand demultiplexing it into R signals with ν=0,1,...,R-1. This means that the samples of the decimated signal are

number

[0106] As can be seen from figure 4, for a decimation rate R=3, a total of three decimated digital received signals are determined, which exhibit different starting phases, i.e. different starting samples. This is done in order to calculate in step 35 a particularly useful noise measure, namely the "effective noise power estimate", also called "ENPE".

[0107] Thus, the process of FIG. 3 can be understood as follows: in the digital domain, the digital received signal is decimated using different signal phases ν ∈ {0,1,...,R-1}, and each of the resulting R signals is sampled at a sampling rate f s =f b / R. Note that in some embodiments, the set of signal phases employed may also be a subset of the complete set of phases {0, 1, ..., R-1}, e.g., {0, 2, 4, ..., R-1}. In other words, each group of decimated digital received signals does not necessarily include all possible signal phases.

[0108] Mathematically, each decimation rate R is assigned a coefficient vector having the same length as the decimated signal, including, for example, the coefficients of an FIR low-pass filter (LPF). To calculate the ENPE for a decimation rate R, a dot product with the assigned coefficient vector for each of the up to R decimated signal vectors is calculated by the noise estimation circuit 8 in step 35. Optionally, in some embodiments, these dot products may be normalized by dividing by the sum of all the coefficients. The average of the normalized squared dot products is then calculated to obtain the ENPE.

[0109] Mathematically, Figure 4 shows that for each R ∈ {2,3,4,6}, the original signal vector x = [x0 x1 x2...x 23 ] is split into up to R signal vectors,

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[0110] Here, the term

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[0111] To distinguish between different decimation rates R, we use the jth decimation rate R (0,j) We assign superscripts with indices j=0,1,2,... to the decimation rate R (0,j) The coefficient vector assigned to is w (0,j) Gives.

[0112] Because the same measurement data is used to calculate the noise metric of different candidate ACs, although the time variations experienced, for example in amplitude modulated noise, will affect the noise metric, the noise metrics calculated from the same data will still remain comparable, ensuring identification of the AC with the relatively lowest noise metric.

[0113] For decimation rates that are multiples of 2, the computational complexity can be reduced by changing the phase sum ν=0,1,...,R-1 to the phase sum ν=v0,v0+R / 2, where ν0∈{0,1,...,R / 2-1}. For example, for R=6,

number

[0114] Once the noise measure, i.e., ENPE in this specification, has been determined for each candidate acquisition configuration, the ENPE is passed to the configuration circuit 9, which uses the ENPE determined in step 36 to select an acquisition configuration for operation of the sensor system from the candidate acquisition configurations.

[0115] In this embodiment, the configuration circuit 9 determines, in step 36, which of the candidate acquisition configurations results in the lowest noise by evaluating the associated ENPEs.

[0116] Once the candidate acquisition configuration is selected as the acquisition configuration, the noise scan is completed. The acquisition configuration is provided by the configuration circuit 9 to the drive circuit 4. In addition, the selected acquisition configuration is stored in the memory 10 for future reference. The capacitive touch sensing system 21 is then operated in at least one SN scan according to the result of the noise scan (step 37). It should be noted that the SN scan may be performed for multiple sensor (transmission) lines 3, especially in the case of mutual capacitance sensors. After the SN scan, a new noise scan is performed starting from step 30.

[0117] The two resulting signal processing chains for noise and signal-to-noise scans are shown in simplified schematic in FIG.

[0118] Figure 5 shows in the upper part of the figure the digital processing of the data acquired during the SN scan. The sensor received signal is at a carrier frequency f c is converted from the analog domain to the digital domain at twice the frequency, i.e., f s =2 f cand a digital sensor received signal is obtained using an ADC 5. The digital ADC output signal, i.e. the digital sensor received signal, is then provided to a digital signal processing circuit 15, which comprises a demodulator 13, an FIR low-pass filter 6, and a decimation circuit 7. The digital ADC output signal, i.e. the digital sensor received signal, is demodulated by the demodulator 13 by multiplying its samples alternately by plus one and minus one, and the demodulated signal is input to a digital low-pass LPF filter 6 with a filter coefficient of L, and finally decimated by a factor L, i.e. after inputting L samples, only one sample is the output of the decimator 7.

[0119] The lower part of Fig. 5 shows in more detail the operation of the digital processing circuit 15 and the noise evaluation circuit 8 during the noise scan. The ADC 5 samples the analog sensor received signal at a predefined noise scan frequency. In Fig. 5 the operation of one exemplary AC is shown. This operation is performed for each AC considered.

[0120] An example AC has a carrier frequency f c =f b / (2·R). The sampled signal after conversion by ADC5 to obtain the digital sensor received signal is demultiplexed into R signals indexed by ν∈{0,1,...,R−1}, where each of the R signals has a sampling rate f s =2 f c In order to provide conditions similar to those during the SN scan, each of the demultiplexed signals is demodulated by a respective demodulator 13 by multiplying its samples alternately by plus and minus one, and each demodulated signal is filtered in a FIR low pass filter LPF6 and decimated by a decimation circuit 7. R·L samples x kAfter analog-to-digital conversion and processing, one decimated sample is obtained for each decimated signal. Each decimated sample is squared by the noise estimation circuit 8, and then the average of these R squared samples is calculated by the noise estimation circuit 8 to obtain ENPE.

[0121] It should be noted that the processes described above with reference to Figures 3 and 5 do not necessarily have to be completed "on-line." Instead, as described above with reference to Figures 3-5, each ADC sample x k may be discarded as soon as it is multiplied by (±1) to obtain the demodulated value as an intermediate product. k can be stored in memory 10 for off-line processing. In this embodiment, the processing described with reference to Figures 3 and 5 begins after A / D conversion.

[0122] FIG. 6 shows an exemplary flow diagram of the operation of the sensor circuit 1 in another embodiment. This operation corresponds to the above description, particularly with reference to FIG. 3. Thus, the operations of steps 60 to 67 correspond to the operations of the respective steps 30 to 37, except for step 66a, in which the configuration circuit 9 sets the aperture time of the acquisition configuration used by the drive circuit 4 for the SN scan to an integer multiple (including the same aperture time, i.e. integer=1,) of the aperture time used by the A / D converter 5 during the current noise scan. To this end, the configuration circuit 9 is connected to the A / D converter 5 (not shown in FIG. 1). The aperture time is restored to the original aperture time in step 60 at the next noise scan period.

[0123] This embodiment is based on the inventor's realization that when capturing analog data to create time-discrete samples, the duration that the analog signal is input to the measurement system, i.e., the duration that the measurement system is exposed to the outside world and, as a result, has its internal analog state altered by the analog input signal, can affect the value of the output sample. In the case of the ADC5, this duration is the so-called "aperture time". The schematic diagram in FIG. 7 shows a frequency f n The magnitude of the transfer function of an ideal ADC, also called its sensitivity to a single-tone signal, is shown for aperture times of 0.833 μs and 2.5 μs. Spectral zeros are observed at multiples of the inverse of the aperture time, i.e., 1 / 0.833 μs=1.2 MHz and 1 / 2.5 μs=400 kHz, respectively.

[0124] In some touch sensitive devices, when an electrode is sensed, the current flowing to or from the sensor electrode is integrated over a deterministic amount of time, this integration time also being considered the opening time.

[0125] Since the aperture time windows of two consecutive samples cannot overlap, the aperture time cannot be longer than the time between two consecutive samples, i.e., the sample interval. The higher the sampling frequency, the shorter the sample interval and therefore the shorter the maximum aperture time. Therefore, the predefined noise scan frequency f b =2 R f c When sampling at f c is the exemplary AC carrier frequency and the maximum aperture time 1 / (2 R f c ) is the sampling frequency 1 / (2 f c ) is shorter than during SN scans.

[0126] The desired aperture time may also depend on the type of sensor used. For example, ITO has a lower conductivity compared to copper, so there is typically a longer settling time for the signal in an ITO sensor compared to a PCB sensor. Therefore, a longer aperture time may be desirable for an ITO sensor compared to a similarly shaped PCB sensor. Note that there are also cases where the aperture time has little effect on the measurements. These may include, for example, voltage measurements made at the output of a voltage follower circuit (a "buffer amplifier").

[0127] However, in certain scenarios, the desired aperture time may be shorter than the sample interval of the SN scan, but may exceed the sample interval of the noise scan. In this case, obviously, the desired aperture time cannot be applied to the noise scan. A different, shorter aperture time may be selected for the noise scan. However, selecting different aperture times for the SN scan and the noise scan may impair the possibility of obtaining reliable ENPE from the noise scan data for the SN scan. In particular, if the noise scan susceptibility spectrum has zeros at frequencies where the SN scan susceptibility spectrum does not have zeros, the harmful noise may not be seen in the noise scan data, and the noise robustness algorithm may make a meaningless decision.

[0128] However, for a certain ratio between the SN scan aperture time and the noise scan aperture time, it is possible to obtain a relatively good carrier frequency determination, i.e. a relatively good determination of the acquisition configuration for some noise scenarios, 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 shown as an example in FIG. 7 for a ratio of 1 / 3 where all "noise scan zeros" (integration time 0.833 μs) span "SN scan zeros" (integration time 2.5 μs).

[0129] The ENPE provides an absolute estimate of the noise power of the received signal after demodulation and low-pass filtering, for which some sensor systems or applications may have an upper threshold above which undesirable operation may occur.

[0130] One exemplary approach to obtain lower noise power is to increase the number of samples L acquired and processed, referred to herein as the "packet length", thus making the filter length 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 does not usually improve noise suppression. Noise suppression depends primarily on the low-pass filtering selected, of which the packet and filter length are only one aspect. Figure 17 shows an example of the spectral noise suppression when the packet size is increased from 5 to 7 for a boxcar window and a Hanning window. For example, in the above table with a boxcar window, the normalized frequency

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[0131] FIG. 9 shows the noise at all noise frequencies f=f for a boxcar or rectangular window low-pass filter (top) and a “Hanning” window low-pass filter (bottom). n , or all normalized frequencies Ω=2πf / f in Fig. 9 s9 indicates that the packet length needs to be increased so that noise suppression is improved for all noise frequencies. In particular, the spectral zeros of the shorter packet length should fall on the zeros of the longer packet length. In FIG. 9, it is shown that this is achieved when the longer packet length is a multiple of the shorter packet length for the boxcar window LPF, and when the longer packet length is a multiple of the shorter packet length +1 for the Hanning window LPF. For the boxcar, Hanning window, and Matlab's Hanning window (the Hanning window in this specification corresponds to the Hanning window with the first and last samples removed) low pass filters, the rules of how to increase the packet length L to L' to ensure improved noise suppression effect for all noise frequencies are as follows:

number

[0132] Another requirement for the sensor system may be a minimum report rate, i.e. the capacitive touch or non-contact sensing system 21 may be required to output estimated data at a report rate equal to or higher than the minimum report rate. This estimated data may be, for example, low-pass filtered and decimated data, as illustrated in FIG. 5 (top) as “To Touch Detector 11”, or data calculated therefrom. Such a minimum report rate is typically independent of how the reported data is acquired and processed, i.e., independent of the carrier frequency, for example. However, the minimum report rate sets an upper limit on the measurement time, which is the inverse of the minimum report rate. Another requirement for the capacitive touch sensing system 21 may be a minimum SNR, in other words the expected noise power of the output values ​​may be below a limit value. In some embodiments, this may be a first order requirement, and if it cannot be met with the desired report rate, the report rate is reduced (i.e. the scan is increased in time) while maintaining and attempting to meet the noise power limit, as described below with reference to FIGS. 8A and 8B.

[0133] 8A and 8B show a flow diagram illustrating the operation of the sensor circuit 1 in another exemplary embodiment. The operation corresponds to that described above with particular reference to Fig. 6. Thus, the operations of steps 80-87 correspond to the operations of steps 60-67, respectively, except for steps 82a and 86a-86g, as described below.

[0134] In step 82, the sensor received signal acquired from the capacitive touch sensing system 21 is A / D converted to obtain a digital received signal, which corresponds to the process described above with reference to steps 32 and 62. In this embodiment, the sensor received signal acquired 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.

[0135] In step 82a, a copy of the digital received signal having the maximum scan time is stored in memory 10. Then, a portion of the digital received signal is selected, i.e. the portion having the predefined minimum scan time. Further processing in steps 83-85 is based on this portion of the digital received signal.

[0136] In step 86, an acquiring configuration is selected from the candidate acquiring configurations. Note that in Fig. 8B, for ease of understanding, the processing of step 86 is broken down into steps 86a to 86g.

[0137] In step 86a, the configuration circuit 9 selects the candidate acquisition configuration that produces 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 determined 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 the acquisition configuration for SN scan in step 87, corresponding to the previous description. The aperture time for SN scan is set in step 86c, as described with reference to FIG. 6.

[0138] If the noise metric for the selected candidate acquisition configuration exceeds a predefined noise threshold, processing proceeds to step 86d. Assuming in step 86d 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 retrieves from the memory 10 a copy of the original digital reception signal having the maximum scan time stored in step 82a. Then, in step 86f, a larger portion of the original digital reception is selected 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. Processing then continues with step 83, and the increased scan time is evaluated according to steps 83-86, as described above.

[0139] Mathematically, we use the Noise Robustness Level (NRL) as an index of a predefined maximum scan or measurement time. For example, let NRL ρ = 0 denote the lowest NRL corresponding to the shortest maximum scan time T0. For each candidate acquisition configuration, its packet length is determined by the sampling frequency f s =2 f c, the maximum number of samples that can be taken during this time.

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number

[0140] For the next higher NRL ρ=1, the length of each AC packet is determined according to equation (1) depending on the low-pass filter design, for example, parameter k=2, ie, the scan time is approximately doubled.

[0141] The described steps are repeated iteratively until an acquisition configuration that satisfies the noise threshold is found or a maximum predefined scan time is reached and no acquisition configuration satisfies the noise threshold. In the latter case, the query of step 86d generates a warning signal at output 12 in step 86g to warn that a suitable acquisition configuration has not been found. Operation then proceeds to step 86c, where the AC is used to provide the best noise metric for operation in the SN scan.

[0142] As is evident from the above, a scan cycle may consist of a noise scan followed by an SN scan using the AC that gave the best noise metric, followed by a next scan cycle having a next noise scan and an SN scan, which is then repeated until the device is shut down.

[0143] As mentioned above, the goal is to find the lowest NRL, i.e., the shortest required scan time, i.e., the highest report rate, for which there exists a candidate acquisition configuration that results in an ENPE at the maximum noise threshold. If there exists more than one acquisition configuration with the same scan time that results in an ENPE below the limit, the process of Figures 8A and 8B selects the AC that results in the lowest ENPE.

[0144] If there are candidate ACs whose sampling frequencies do not share a common multiple, a slightly modified process using multiple predefined noise scanning frequencies may be adopted. A corresponding exemplary embodiment is shown in the flow diagram of FIG.

[0145] Predefined noise scan frequency f b Given a noise-scanned signal sampled at , it is possible to choose many different values ​​for the integer decimation rate R.

[0146] However, the noise scan frequency f b Carrier frequency at which ENPE can be calculated from a signal sampled at

number

[0147] To increase the set of candidate carrier frequencies, additional noise scanning frequencies may be evaluated according to an embodiment. To distinguish between these noise scanning frequencies, the i-th candidate fundamental frequency f (i) We assign superscripts to the indices i=0,1,2,.... We define the jth decimation rate for the ith candidate fundamental frequency as R (i,j) and the corresponding candidate carrier frequencies and coefficient vectors are denoted as f (i,j) and w (i,j) It is written as:

[0148] Let the packet length of an AC with fundamental frequency index i, sub-frequency index j, and NRL ρ be

number

[0149] The process starts with the initialization of the sensor circuit 1 in step 100. For each predefined noise scan frequency, an individual noise scan is performed in steps 101, 102 and 103. It should be noted that this embodiment is not limited to performing three subsequent noise scans. The operations during each noise scan correspond to one of the embodiments described above with reference to Figs. 1-9. In each step 101, 102 and 103, a noise metric is obtained for at least one candidate AC. In some embodiments, noise metric for the same candidate AC may be obtained in multiple steps 101, 102 and 103.

[0150] In step 104, an 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 acquisition configuration candidates of steps 101, 102 and 103 that result in the lowest overall ENPE. In other words, the overall acquisition configuration corresponds to the best available candidate acquisition configuration of the noise scans 101, 102, 103. The NRL concept can also be applied in such a case of multiple noise scan frequencies. In step 105, the sensor system is operated in an SN scan using the overall acquisition configuration. Then, the operation returns to step 100 until the processing of the sensor circuit 1 is stopped.

[0151] In contrast to other known approaches, the approach described according to various embodiments not only provides a relatively good solution for identifying carrier frequencies, but also provides a complete solution for noise robustness. It even provides robustness against AM noise and squared noise, for example. This is made possible by a very accurate and quantitative SNR or noise power estimate that can be calculated from the same measurement data but for different ACs. This further allows finding a trade-off between touch report rate and output SNR.

[0152] Furthermore, for a selected low-pass filter design method, e.g., a boxcar window filter function, with the requirement that guarantees improved noise robustness when the scan time is increased while other AC parameters are left unchanged, the parameters of many candidate ACs (e.g., filter length and filter coefficient values) can be derived from a few high-level requirements (e.g., 200 μs scan time), allowing for a simple noise robustness configuration without the need for extensive training.

[0153] A further exemplary aspect of the present disclosure relates to obtaining a separated copy of the current and digital processing for signal acquisition using overlapping aperture windows.

[0154] When capturing analog data to create time-discrete or digital output samples, the duration that the analog signal is input to the measurement system, i.e., the time that the measurement system is exposed to the outside world and as a result has its internal analog states altered by the analog input signal, can affect the value of the output sample.

[0155] In the case of an analog-to-digital converter (ADC), this duration is known as the aperture time, as previously mentioned. nRecall that the magnitude of the transfer function of an ideal ADC, also called its sensitivity to a single-tone signal, is shown for aperture times of 0.833 μs and 2.5 μs. Spectral zeros are observed at multiples of the inverse of the aperture time, e.g., 1 / 0.833 μs=1.2 MHz and 1 / 2.5 μs=400 kHz, respectively.

[0156] In some available touch screen controllers, when an electrode is sensed, the current flowing to or from the sensor electrode is integrated over a deterministic amount of time to measure the amount of charge transferred during this time. This integration time is one aperture time. A basic, illustrative diagram of charge measurement using current integration is shown in FIG. 11. FIG. 11 shows the relationship between the signal s ap The aperture switch controlled by (t) is on, and the signal s res While the reset switch controlled by (t) is off, the capacitor C int The current i integrated on in The resistance R of the current source can be neglected when the aperture switch is on.

[0157] In standard serial processing of analog signals, the aperture time windows of two successive samples cannot overlap, so the aperture time cannot normally be longer than the time between two successive samples, i.e. the sample interval. The higher the sampling frequency, the shorter the sampling interval and therefore the shorter the maximum aperture time.

[0158] 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 are described, namely "noise scan" and "SN scan", 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 desirable for both. While the aperture time is selected for the SN scan, the sampling frequency of the noise scan may be too high to fit the aperture window of the selected time between two consecutive samples, resulting in overlapping aperture windows.

[0159] Some means of parallel processing may be beneficial to obtain overlapping aperture time windows. For example, in a system such as the touch screen controller mentioned above, two or more integrators would be useful. The problem is that when these two or more integrators tap the same pad or measurement node, there is a risk that their measurements could potentially interfere with each other. This is shown in Figure 12, where the state of the aperture switch is shown on the right side of the figure.

number

number

[0160] In capacitive sensing, the desired aperture time also depends on, for example, the type of sensor used. For example, ITO sensors typically have a longer settling time compared to PCB sensors because ITO has a lower electrical conductivity compared to copper. Therefore, a longer aperture time may be desirable for an ITO sensor compared to a PCB sensor of similar geometry.

[0161] Based on the above, a solution may be to employ a current amplifier with one input and multiple outputs to obtain multiple isolated copies of the input current. Each copy can then be tapped with an integrator, and the integrator input currents are isolated, i.e., independent of each other. In a digital post-processing step, the data obtained from the multiple analog copies may be rearranged, for example, to result in a single digital output signal.

[0162] The basic approach of this discussion is to create multiple separated copies of an analog input signal. Analog processing and A / D conversion can then be performed separately on each of the signal copies. The final step is to interleave or multiplex the digital samples from the different processing branches into a single output signal.

[0163] A typical electronic component whose input current is independent of its output current is the transistor. This independence also holds for more complex components such as amplifiers, which may contain multiple such transistors. If an input current controls two output currents and the input current is independent of either output current, this means that the output currents are also mutually independent of each other.

[0164] In some touchscreen controller devices and in classical touchscreen controller measurements, the analog input signal is a current. In some analog front-ends (AFEs) of existing touchscreen controllers, there are multiple substantially identical parallel units for analog processing called slices. Each slice includes an integrator.

[0165] While it would be desirable to have completely independent timing for the different integrators, some touchscreen controller devices may be limited to a common sampling interval or sampling frequency for all slices. However, apart from the small digital corrections required, existing devices would allow independent measurement of two copies of the input current if the aperture time windows of the two measurements overlap. Figure 13 is a schematic diagram of two of the so-called slices of an exemplary AFE of a touchscreen controller. The pad of the primary slice at the top left of Figure 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 then connected to the ADC. The inverting output Z1 of the current amplifier of the primary slice is connected to the input of an integrator on the secondary slice, the output of which is again connected to the ADC. The current amplifier of the secondary slice is disconnected and only the amplifier inverting current of the primary slice is input to the integrator. The aperture switch INTMOE may be independently controlled for the primary and secondary slices, while the integrator reset switches RST1 and RST2 may not be independently controllable.

[0166] In the above, we have explained the need to overlap the aperture time window or current integration window for noise scanning. For such noise scanning, we will be mainly interested in the measurement data from a single slice, for example the slice connected to the sensor electrode where the highest noise level can be expected. Assuming that the primary slice is connected to this noisiest electrode, for example the noisiest electrode is connected to the pad of the primary slice in Fig. 13, then in theory two separated copies of the input current of the primary slice are obtained, and it is possible to open and close the aperture or reset switch in both the primary slice and the secondary slice without affecting the current on the other slice.

[0167] FIG. 14 shows an example timing diagram of current integration and integrator reset when assuming slice-independent control of aperture and reset switches. Each integration window is preceded by a reset of the integration capacitor. The integration windows of the primary slice and the secondary slice are interleaved and overlap in time. After analog-to-digital (A / D) conversion, the samples from the two slices are interleaved to obtain a single digital signal. For example, a new single digital signal is created by concatenating a first output sample from the primary slice, a first output sample from the secondary slice, a second sample from the primary slice, a second sample from the secondary slice, etc. It is noted that in the context of noise scanning, the acquired signal is decimated before further processing, and after decimation, the current integration windows corresponding to successive samples of these decimated signals no longer overlap.

[0168] However, although integration can be controlled separately for the primary slice and the secondary slice, the timing of Figure 14 may not be achievable in some touch panel controller devices due to the integrator reset control common to the primary slice and the secondary slice.

[0169] What can be done with the touch screen controller is also possible with timing similar to Figure 14, but with non-overlapping integration windows, as shown in Figure 15. In fact, the A / D conversion is also done synchronously on the primary and secondary slices, as indicated by the vertical dashed lines, so every other digital sample from each slice is undesirable, since it is acquired during a possibly random integrator state, rather than at the end of the current integrator's integration phase, and so may be discarded.

[0170] Data acquired in a test implementation using the timing configuration of FIG. 15 is shown in FIG. 16. A 20 kHz single tone signal is coupled to the sensor electrode connected to slice Y34, with a sampling frequency of 200 kHz. Samples from primary slice Y34 and secondary slice Y35 are shown in an interleaved fashion, with solid and dashed lines connecting the samples from each slice, respectively. It can be observed that the signal of slice Y35 (dashed line) still needs to be re-inverted and shifted, since the signal for Y35 is almost a mirror image of the signal for Y34 mirrored at the level of ADC value -15. The required offset needs to be determined before the actual signal acquisition (e.g., with the pads / electrodes disconnected, i.e., with no input signal), but signal reconstruction in the digital domain is feasible.

[0171] When referring to a "copy" of an analog signal in this specification, an exact one-to-one copy is not necessarily required: in some applications, a strictly monotonic copy function may be sufficient, and any distortions may be compensated for in the digital domain.

[0172] However, for systems with processing such as touch screen controller devices where the 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 for digital equalization (i.e., compensation of distortion). Also, in general, a more or less linear copy function may be beneficial, for example, when considering signal equalization along with ADC quantization noise.

[0173] The touch screen controller specific solution mentioned above allows overlapping aperture time windows when the acquisition frequency on the primary and secondary slices is the same but only the acquisition phase is different. However, if the hardware control allows completely independent timing for different slices given multiple copies of the same analog signal, it becomes possible to obtain a generic solution to the problem of signal acquisition for noise level evaluation in different AFE configurations with any different sampling frequencies and aperture time windows.

[0174] Some embodiments of a sensor system having an analog input signal x(t) include a sensor system that detects two or more analog copies y of x(t). i (t), i=0,1,....

[0175] In some embodiments, the copy y i (t) is a strict monotone map of x(t).

[0176] In some embodiments, the copy y i (t) is a linear function of x(t) i (t)=b i * x(t)+a i It is.

[0177] In some embodiments, the sensor system is a capacitive sensing system.

[0178] In some embodiments, the signal x(t) is a current.

[0179] In some embodiments, the signal y(t) is a current.

[0180] In some embodiments, two or more analog signal copies y i (t) is connected to an analog circuit H i and at least two circuits H i The opening windows overlap in time.

[0181] In some embodiments, the analog circuit H i comprises an integrator.

[0182] In some embodiments, two or more circuits H i The above sampling frequencies are the same.

[0183] In some embodiments, the sensor system comprises a current amplifier having an input supplied with x(t), the current amplifier having two or more output stages sharing a single input stage.

[0184] In some embodiments, samples from signals on different branches are multiplexed to result in a single output signal.

[0185] A generic solution for creating a copy of the analog input signal to obtain a separated signal for independent processing is now possible, which is useful for solving the problem of comparing arbitrary AFE configurations with each other and finding a suitable acquisition configuration.

[0186] In some embodiments, the aperture time is increased over the sampling period, allowing for very accurate noise power estimation.

[0187] Compared to alternative approaches that evaluate signals from different sensor electrodes, there is no risk that noise may be coupled into different sensor electrodes with different coupling strengths and erroneously bias the estimates, simply because in the described approach all data evaluated originates from a single sensor electrode.

[0188] Although the present invention has been described with respect to specific embodiments of the present invention, these embodiments are merely illustrative and not limiting of the present invention disclosed herein. The description herein of illustrated embodiments of the present invention, including the description in the Abstract and Overview, is not intended to be exhaustive or to limit the present invention to the precise form disclosed herein (and in particular, the inclusion of any particular embodiment, feature, or function in the Abstract or Overview is not intended to limit the scope of the invention to such embodiment, feature, or function). Rather, the description is intended to describe exemplary embodiments, features, and functions to provide a context for understanding the present invention to those skilled in the art, including any such embodiment feature or function described in the Abstract or Overview, but not to limit the present invention to any specifically described embodiment, feature, or function. Specific embodiments of the present invention and examples of the present invention are described herein for illustrative purposes only, but various equivalent modifications are possible within the spirit and scope of the present invention, as those skilled in the art will recognize and appreciate. As shown, these modifications can be made to the present invention in light of the foregoing description of illustrated embodiments of the present invention, and are intended to be included within the spirit and scope of the present invention. Thus, although the invention has been described herein with reference to specific embodiments thereof, it will be understood that various modifications, variations, and substitutions are contemplated within the foregoing disclosure, and that in some instances, some features of the embodiments of the invention may be employed without a 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 a particular situation or material to the essential scope and spirit of the invention.

[0189] References throughout this specification to "one embodiment," "an embodiment," or "a specific embodiment," or similar terminology mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment, and may not necessarily be present in all embodiments. Thus, each appearance of the phrases "in one embodiment," "in an embodiment," or "in a specific embodiment," or similar terminology in various places throughout this specification, does not necessarily refer to the same embodiment. Furthermore, the particular features, structures, or characteristics of any particular embodiment may be combined in any suitable manner with one or more other embodiments. It should be understood that other variations and modifications of the embodiments described and illustrated herein are possible in light of the teachings herein, and should be considered as part of the spirit and scope of the invention.

[0190] 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 present invention. However, one of ordinary skill in the art will recognize that the embodiments may be practiced without one or more of the specific details, or with other devices, systems, assemblies, methods, components, materials, parts, and / or equivalents. In other instances, well-known structures, components, systems, materials, or operations are not specifically shown or described in detail to avoid obscuring aspects of the embodiments of the present invention. The present invention may be illustrated by using a specific embodiment, but this is not any particular embodiment and does not limit the present invention thereto, and one of ordinary skill in the art will recognize that additional embodiments are readily apparent and part of the present invention.

[0191] Any suitable programming language may be used to implement the routines, methods, or programs of the embodiments of the invention described herein, including, but not limited to, C, C++, Java, assembly language. Different programming techniques may be employed, such as procedural or object-oriented. 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 in a single storage medium or distributed across multiple storage media, and may reside in a single database or multiple databases (or other data storage techniques). Although steps, operations, or computations may be presented in a particular order, this order may be changed in different embodiments. In some embodiments, to the extent that multiple steps are shown herein as sequential, some combinations of such steps in alternative embodiments may be performed simultaneously. The sequence of operations described herein may be interrupted, suspended, or otherwise controlled by another process, such as an operating system, kernel, etc. The routines may operate within an operating system environment or as independent routines. The functions, routines, methods, steps, and operations described herein may be implemented in hardware, software, firmware, or any combination thereof.

[0192] The embodiments described herein can be implemented in the form of control logic in software, or hardware, or a combination of both. The control logic can be stored in 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 disclosure and teachings provided herein, a person skilled in the art will appreciate other ways and / or methods for implementing the present invention.

[0193] It is also within the spirit and scope of the present invention to implement any of the steps, operations, methods, routines, or portions thereof described herein in software programming or code. Such software programming or code can be stored in a computer-readable medium and operated by a processor to cause a computer to perform any of the steps, operations, methods, routines, or portions thereof described herein. The present invention can be implemented by using software programming or code in one or more general-purpose digital computers, by using application specific integrated circuits, programmable logic devices, field programmable gate arrays, and the like. Optical, chemical, biological, quantum mechanical, or nano-fabricated systems, components, and mechanisms can be used. In general, the functions of the present invention can be accomplished by any means as known in the art. For example, distributed or networked systems, components, and circuits can be used. In another embodiment, communication or transfer of data (or otherwise moving it from one place to another) can be by wire, wireless, or any other means.

[0194] A "computer-readable medium" may be any medium that can contain, store, communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, system, or device. A computer-readable medium may be, by way of example only and not limitation, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, system, device, propagation medium, or computer memory. Such computer-readable media is generally intended to include software programming or code that is machine-readable and may be human-readable (e.g., source code) or machine-readable (e.g., object code). Examples of non-transitory computer-readable media may include random access memory, read-only memory, hard drives, data cartridges, magnetic tapes, floppy diskettes, flash memory drives, optical data storage devices, compact disc read-only memory, and other suitable computer memory and data storage devices. In an exemplary embodiment, some or all of the software components may reside on a single server computer or on any combination of separate server computers. As one skilled in the art can appreciate, a computer program product implementing embodiments disclosed herein may comprise one or more non-transitory computer-readable media that store computer instructions transformable by one or more processors in a computing environment.

[0195] A "processor" includes any hardware system, mechanism, or component that processes data, signals, or other information. A processor may include a general-purpose central processing unit, a system with multiple processing units, dedicated circuitry for achieving functionality, or other systems. Processing need not be limited to a geographic location, nor need it have a time limit. For example, a processor may perform its functions in "real-time," "offline," "batch mode," etc. Portions of processing may be performed by different (or the same) processing systems at different times and in different locations.

[0196] Terms such as "component," "module," "circuitry," "circuit," "device," "unit," and "system" encompass 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 in a single device or distributed across several devices. The subject matter described may be implemented as an apparatus, method, or article of manufacture using standard programming or engineering techniques to produce software, firmware, hardware, or any combination thereof to control one or more computing devices.

[0197] As used herein, the terms "comprises," "comprising," "includes," "including," "has," "having," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a process, product, article, or apparatus comprising a list of elements is not necessarily limited to only those elements and may include other elements not expressly listed or inherent to such process, process, article, or apparatus. The term "exemplary" as used throughout this specification means "serving as an example, instance, or illustration" and does not mean "preferred" or "having advantages" over other embodiments.

[0198] Furthermore, the term "or" as used herein 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 present) and B is false (or absent), A is false (or absent) and B is true (or present), and both A and B are true (or present). As used herein, including in the claims that follow, terms preceded by "a" or "an" (and "the" when the antecedent is "a" or "an") include both the singular and plural forms of such terms (i.e., a reference to "a" or "an" clearly indicates only the singular or only the plural), unless the context clearly indicates otherwise. Also, as used throughout this description and the claims that follow, the meaning of "in" includes "in" and "on," unless the context clearly indicates otherwise.

[0199] It will be understood that one or more of the elements shown in the drawings / diagrams may also be implemented in a more separate or integrated manner, or in some cases removed or rendered inoperative, as may be useful according to a particular application. Additionally, any signal arrows in the drawings / diagrams should be considered as merely illustrative and not limiting, unless specifically stated otherwise.

[0200] Accordingly, the scope of the present invention is intended to be defined solely by the following claims, as they may be amended, with each claim expressly incorporated into this specification as an embodiment of the present invention.

[0201] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor, module, or other unit may fulfill the functions of several items recited in the claims.

[0202] The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program can 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 can also be distributed in other forms, such as via the Internet or other wired or wireless communication systems. Any reference signs in the claims should not be interpreted as limiting the scope.

Claims

1. 1. A method for determining a configuration that achieves robustness against noise for the operation of a system, comprising the steps of: acquiring a system receive signal from the system; determining a digital receive signal from the system receive signal by A / D conversion of the system receive 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 decimation rates different from one another, each of the two or more decimation rates being associated with a respective candidate obtaining configuration; determining one or more noise metrics for a plurality of said candidate capturing configurations using one or more of said plurality of decimated digital received signals; determining the acquiring configuration for operation of the system from the candidate acquiring configurations using the one or more noise metrics; The step of determining the acquiring configuration for operation of the system from the candidate acquiring configurations comprises the steps of comparing the one or more noise measures to a noise threshold, and if the noise threshold is not met by any of the noise measures, increasing a scan time of at least one of the candidate acquiring configurations to obtain at least one updated candidate acquiring configuration; determining one or more updated noise measures for the at least one updated candidate configuration; and comparing the one or more updated noise measures to the noise threshold.

2. 2. The method of claim 1, wherein the step of determining the acquiring configuration comprises the step of selecting a preferred noise measure from the one or more noise measures, the acquiring configuration being set to correspond to an acquiring configuration of the candidate for the preferred noise measure.

3. The method of claim 2 , wherein the preferred noise metric results in a lowest noise level of the one or more noise metrics.

4. 4. The method according to claim 1, wherein for each of the two or more decimation rates a corresponding group of decimated digital received signals is determined, and in each group the decimated digital received signals differ from each other at different starting phases.

5. 5. The method of claim 4, wherein one or more of the noise measures are determined by an effective noise power estimation, the effective noise power estimation including a determination of a sum of phase instantaneous noise measures across each of the decimated digital received signals of one of the group of decimated digital received signals.

6. 6. The method of claim 5, wherein each of the phase instantaneous noise measures is a sum of samples of a respective decimated digital received signal weighted with a coefficient from a coefficient vector.

7. 7. The method of claim 1, wherein the acquiring configuration comprises at least one or more of a sampling frequency for A / D conversion, an operating frequency of a stimulus signal for operation of the system, a scan duration, a number of samples to be acquired, and a low pass filter coefficient.

8. The method according to any one of claims 1 to 7, wherein the predefined noise scan frequency is between 3 and 40 times the operating frequency of a stimulus signal during operation of the system.

9. The method according to any one of claims 1 to 8, wherein the two or more decimation rates are multiples of two.

10. The method according to any one of claims 1 to 9, wherein the system receive signal is acquired during the noise scan without a stimulus signal being applied to the system.

11. The method of claim 10 , wherein the scan time is increased by an integer multiple of the scan time of a preceding noise scan.

12. A method according to any preceding claim, comprising the step of: following the noise scan, operating the system during an SN scan using the acquiring configuration determined during the noise scan.

13. 13. The method of claim 12, comprising the step of performing a plurality of subsequent noise scans between two SN scans, the plurality of noise scans using predefined noise scan frequencies, and the predefined noise scan frequencies of at least some of the plurality of noise scans being different from each other.

14. 14. The method of claim 13, further comprising determining an acquisition configuration for operation of the system during an SN scan from acquisition configurations obtained during the subsequent multiple noise scans.

15. 15. The method according to claim 12, wherein an aperture time for A / D conversion during the noise scan is the same as an aperture time set for the SNR scan or is substantially an integer fraction of the aperture time.

16. The method of any one of claims 1 to 15, wherein the system is one or more of a capacitive sensor system and a touch screen sensor system.

17. The method according to any one of the preceding claims, wherein the system is a sensor system and the system received signals are sensor received signals.

18. A method according to any preceding claim, wherein the system is a communications system and the system receive signal is a communications receive signal.

19. 1. A method of operation for achieving noise robustness in a sensor system, comprising: performing at least one noise scan on the sensor system; conducting at least one SN scan on the sensor system; A method according to claim 1, wherein an aperture time of A / D conversion during said at least one noise scan is the same as an aperture time of A / D conversion of said at least one signal-to-noise scan or is substantially an integer fraction of said aperture time.

20. A computer readable medium comprising content configured to cause a sensor circuit to perform the method of any one of claims 1 to 19.

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