Method for signal interference suppression and method for sensor operation

Abstract

The invention relates to a method for signal interference suppression (30) of an analogue sensor signal (26) of a microsensor (10), having a periodic interference signal (24). The invention also relates to a method for sensor operation (18) of a microsensor (10).

Description

[0001] Description

[0002] title

[0003] Methods for signal interference suppression and methods for sensor operation

[0004] The invention relates to a method for signal interference suppression according to the preamble of claim 1. Furthermore, the invention relates to a method for sensor operation.

[0005] State of the art

[0006] DE 10 2020 215 511 A1 describes an analog front-end architecture for capacitive pressure sensors, which has a first integrator unit that performs a boxcar integration for low-noise amplification of the input signals and a second integration unit that further processes the amplified signals.

[0007] Disclosure of the invention

[0008] According to the present invention, a method for signal interference suppression with the features of claim 1 is proposed. This allows the sensor signal to be easily and cost-effectively suppressed of noise and periodic interference. The signal-to-noise ratio of the sensor signal can be increased. Signal noise and periodic interference in the sensor signal can be suppressed. A correlation between the subdivision of the sensor signal and the periods of the interference signal can be reduced or avoided.

[0009] The microsensor can be a pressure sensor, microphone, gyroscope, and / or acceleration sensor. The microsensor can be a micromechanical sensor. The microsensor can measure a variable surrounding the microsensor, such as an absolute ambient pressure or a differential pressure, or an acceleration acting on the microsensor. The microsensor can be a capacitive pressure sensor. The microsensor can be used in a transportation device, a vehicle, an industrial device, a robot, a household device, a household appliance, a gardening device, a gardening tool, a medical device, a sports device, a sports device, a consumer electronics device, an aircraft, a gaming device, a gaming device, and / or a building device.

[0010] The analog sensor signal can be tapped by an evaluation circuit on the microsensor. The evaluation circuit can include an analog-to-digital converter for converting the analog sensor signal into a digital sensor signal. The evaluation circuit can be implemented in an evaluation unit. The evaluation unit can be designed as an application-specific integrated circuit (ASIC).

[0011] The periodic interference signal can be caused by a periodic external excitation, for example, a vibration in the microsensor or a vibration of the microsensor itself. The periodic interference signal can be caused by a periodic internal excitation, for example, by switching processes, particularly when the analog sensor signal is read by the evaluation circuit. The periodic interference signal can be a harmonic interference signal.

[0012] The general window function, also called a boxcar function, specifies a window that can be positioned anywhere with respect to the x-axis and has a value greater than zero, preferably one, whereby all values ​​outside the window are zero or approximately zero. The sequential application of the general window function, in particular as masking of the sensor signal, can comprise a temporally offset or simultaneous application of general window functions that are sequential in the time dimension of the sensor signal and whose windows are arranged sequentially one after the other in the time dimension, thereby dividing the sensor signal into readout sections. The sensor signal can be divided into readout sections by the sequential application of the general window function. In order to limit the respective readout section, the general window functions can each have a predetermined window width that specifies the readout width of the readout section.The readout width of the readout sections can be the same or different. The window width can depend on the readout width and can preferably be smaller than the readout width. The window sections can occupy a sub-area of ​​the respective assigned readout section.

[0013] If the window width of the window section is smaller than the readout width of the associated readout section, the remaining area in the readout section can be excluded from the integration. The window section can be arranged centrally in the readout section or off-center. The window section can be spaced from a beginning and / or end of the readout section. The window sections can assume a predetermined, in particular equal, proportion, for example, specified as a percentage, with respect to the respectively associated readout section. The window width can be greater than 50% of the readout width.

[0014] The window position indicates the position of the window section relative to the readout section, in particular relative to at least one reference point of the readout section. The reference point can be the center of the readout section, the beginning, and / or the end of the readout section. The window position can be determined by an offset from the reference point that is dependent on or independent of the readout width.

[0015] The first readout section does not necessarily have to be the initial readout section, but can occur anywhere in time with the sensor signal. The second readout section, however, follows the first readout section immediately in time. A temporal overlap between the readout sections and window sections can be completely excluded. The readout sections can follow one another immediately in time. The window sections can all be spaced apart in time.

[0016] The signal interference suppression method can be applied in a path of analog signal processing of the sensor signal, in particular in the evaluation unit.

[0017] In an advantageous embodiment of the invention, it is provided that if the first and second readout widths deviate from an integer multiple, in particular also from an integer divisor, of a period of the interference signal, the first and second readout widths are the same. The value of the predefined readout width of the first and second readout sections, which deviates from an integer multiple of the period of the interference signal, can be selected by calibrating the microsensor in a defined test environment with constant ambient conditions by applying different values ​​for the readout width and evaluating the result of the integration in each case.The maxima occurring during integration, which, for example, are present at readout width values ​​that correspond to an integer multiple and / or an integer divisor of the period of the interference signal, can serve as limit values ​​from which the selected readout width value should be spaced, in particular as far as possible. Alternatively or additionally, the selected readout width value can be obtained by optimizing an objective function, searching for minimal correlation, and / or creating an empirical and / or analytical model and deriving advantageous readout widths therefrom. The readout width of the majority of the readout sections can be the same.

[0018] In an advantageous embodiment of the invention, the first and second window widths are the same. The window width of all window sections can be constant.

[0019] In a specific embodiment of the invention, it is advantageous if the respective window section is arranged centrally within the associated readout section. The window section can be equally spaced on both sides from the immediately adjacent readout sections.

[0020] In a specific embodiment of the invention, it is advantageous that if the first window position deviates from the second window position, the first and second readout widths are the same. Preferably, the window positions of the window sections within the associated readout sections are randomly selected. Within a readout section, a distance before the window section can randomly differ from a distance after the window section. The variance of the window positions can depend on the uniform readout width or, in the case of differing readout widths, on the average readout width. The variance can be inversely proportional to the uniform or average readout width.

[0021] In a specific embodiment of the invention, it is advantageous that if the first readout width differs from the second readout width, the first and second window widths also differ from each other. The window widths can have a constant proportion value with respect to the associated readout sections.

[0022] In a preferred embodiment of the invention, it is advantageous for the respective values ​​of the first and second readout widths to be randomly selected. This allows the respective values ​​of the first and second window widths to be randomly specified.

[0023] Preferably, the window widths of the window sections are randomly distributed. This allows the interference signal to be reduced as efficiently as possible. The variance of the window widths can depend on the uniform readout width or, if the readout widths differ, on the average readout width. The variance can be inversely proportional to the uniform or average readout width.

[0024] In a preferred embodiment of the invention, the application of the general window function to the sensor signal comprises a, preferably point-by-point, multiplication of the sensor signal by the general window function. With the multiplication, the values ​​of the sensor signal outside the window section become zero or approximately zero. If the window function within the window has the value of one, the sensor signal can be restricted to the window section and clipped without changing the values ​​of the sensor signal within the window section. The sequential application of the general window function can comprise multiplications of the sensor signal with the general window functions offset in the time dimension of the sensor signal, either consecutively or simultaneously.The integration of the sensor signal, preferably multiplied pointwise by the general window function, in the respective window section can represent a convolution of the sensor signal.

[0025] In a preferred embodiment of the invention, an integration value formed by the integration is calculated for each window section. The integration can include calculating a mean value. The integration can form a mean value as the integration value for the associated window section.

[0026] In a preferred embodiment of the invention, the interference-suppressed sensor signal is formed by averaging the integration values. The sensor signal can be interference-suppressed over at least one time period by compensating for the interference signal over the time period of the sensor signal by averaging the integration values ​​over the window sections within the time period. This further reduces noise in the sensor signal.

[0027] According to the present invention, a method for sensor operation is further proposed, having the features of claim 10. The digital sensor signal can be output for further processing and / or evaluation, in particular for calculating the ambient variable. Furthermore, the invention relates to a microsensor configured to be operated by such a method for sensor operation.

[0028] Furthermore, the invention relates to a control circuit which is configured to carry out the method for signal interference suppression with at least one of the features specified above.

[0029] Further advantages and advantageous embodiments of the invention emerge from the description of the figures and the illustrations.

[0030] Character description

[0031] The invention is described in detail below with reference to the figures. They show in detail:

[0032] Figure 1: A side view of a microsensor in a specific embodiment of the invention.

[0033] Figure 2: A method for sensor operation of the microsensor from Figure 1 with a

[0034] Methods for signal interference suppression in a specific embodiment of the invention.

[0035] Figures 3 to 5: An analog sensor signal over time when applying a method for signal interference suppression, each in a specific embodiment of the invention.

[0036] Figure 1 shows a side view of a microsensor in a specific embodiment of the invention. The microsensor 10 is, for example, a micromechanical pressure sensor 12 with a microelectromechanical (MEMS) sensor element 14, which changes at least one electrical variable depending on an ambient pressure, which in turn influences an analog sensor signal of the microsensor 10. As a result, the sensor signal is dependent on the ambient pressure, and the ambient pressure can be detected by evaluating the sensor signal. The sensor element 14 comprises, in particular, a sensor membrane 15, which is deflectable depending on the ambient pressure and, depending on the deflection, changes an electrical measuring capacitance of the sensor element 14 as the electrical variable.

[0037] The sensor element 14 is arranged on an evaluation unit 16, which has an evaluation circuit. The evaluation unit 16 can be implemented as an application-specific integrated circuit (ASIC).

[0038] Due to vibrations or other environmental influences, the sensor membrane 15 can begin to vibrate and, for example, be subjected to a resonant vibration, which significantly influences the electrical value and causes a periodic interference signal superimposed on the sensor signal. The periodic readout of the electrical value can also impose a, particularly additional, periodic interference signal on the sensor signal via switching elements in the evaluation circuit.

[0039] Figure 2 shows a method for sensor operation of the microsensor from Figure 1 with a method for signal interference suppression, each in a specific embodiment of the invention. The method for sensor operation 18 of the microsensor 10 comprises providing 20 the microsensor 10, detecting 22 the analog sensor signal 26, which has a periodic interference signal 24, which arises, for example, from an interference influence P, over time from the microsensor 10, wherein the sensor signal 26 is dependent on an environmental variable E of the microsensor 10, and processing the sensor signal 26, in particular sampling the sensor signal 26, including signal interference suppression 28 of the sensor signal 26 by a signal interference suppression method 30, as explained in more detail below, and converting 32 the interference-suppressed sensor signal 31 into a digital sensor signal 34 by an analog-to-digital converter 36, and outputting 38 the digital sensor signal 34.

[0040] The method for signal interference suppression 30 comprises a sequential application 40 of a general window function 42 to the detected sensor signal 26 for dividing the sensor signal 26 into temporally sequential readout sections R with window sections A, wherein the readout sections each have a, in particular identical, readout width C and the window sections A each have a, in particular different, temporal window width B.

[0041] Furthermore, an integration 44 of the sensor signal 26 takes place in the respective window sections A. The areas of the respective readout section R outside the window section A are excluded from the integration 44. During the integration 44 in the individual window section A, an integration value 46, in particular a mean value 48, is calculated. Subsequently, the interference signal in the sensor signal 26 is compensated for at least over a time period 50 of the sensor signal 26 by the integration values ​​46 of the window sections A, in particular the mean values ​​48, being again averaged in the time period 50 by averaging 52. The sensor signal 31, which has been de-interferenced with respect to the interference signal by the averaging, is then output.

[0042] The application 40 of the general window function 42 to the sensor signal 26 is explained in more detail below with reference to Figures 3 to 5.

[0043] Figure 3 shows an analog sensor signal over time when applying a method for signal interference suppression in a specific embodiment of the invention. The sensor signal 26 is plotted over time t and includes the interference signal periodic with a period 54. The application of the general window function to the sensor signal 26 involves multiplying the sensor signal 26 by the general window function at a time offset. The application of the general window function divides the sensor signal 26 into readout sections R.

[0044] A first readout section R1 of the readout sections R has a first readout width C1, and a second readout section R2 of the readout sections R has a second readout width C2. A first window section A1 of the window sections A located in the first readout section R1 has a first window width B1, and a second window section A2 of the window sections A located in the second readout section R2 has a second window width B2. The first readout section R1 does not necessarily have to be the initial readout section, but can be present anywhere in time with the sensor signal 26. The second readout section R2 immediately follows the first readout section R1.

[0045] The first and second readout widths C1, C2, as well as all other readout widths C of the readout sections R, as well as the first window width B1 and the second window width B2, as well as all other window widths B of the other window sections A, are equal and each deviate from an integer multiple or an integer divisor of a period 54 of the interference signal superimposed on the sensor signal 26, for example, as a harmonic oscillation. This allows a correlation between the period of the interference signal and the window sections to be reduced, thus significantly suppressing the interference signal.Furthermore, the integration values ​​formed by the integration of the sensor signal 26 in the window sections A differ from one another in comparison between the window sections A and an average value of the integration values ​​over a time period, for example several window sections A, is preferably zero, which corresponds to a complete compensation of the interference signal.

[0046] The first and second window sections A1, A2 are arranged centrally with respect to the respectively associated first and second readout sections R1, R2.

[0047] If, however, the window widths B each corresponded to an integer multiple of the period 54 of the interference signal, the mean value of the integration values ​​caused by the interference signal would be non-zero and could be regarded as the actual value of the sensor signal 26, although the portion of the mean value is actually attributable to the interference signal.

[0048] Figure 4 shows an analog sensor signal over time when applying a method for signal interference suppression in a further specific embodiment of the invention. The sequential application of the general window function divides the sensor signal 26 in the time dimension here specifically into readout sections R with window sections A with different window widths B. For example, the first readout width C1 differs from the second readout width C2 of the readout widths C and, since window section A occupies a constant proportion of the associated readout section R, the first window width B1 also differs from the second window width B2. The value of the readout widths C is, in particular, randomly selected and thus differs randomly between the respective readout sections R. This can reduce a correlation between the period of the interference signal and the window sections, thus significantly suppressing the interference signal.

[0049] The window position 56 of the window sections A within the associated readout sections R is centered in each case. This means that a first window position 56.1 of the first window section A1 is centered with respect to the first readout section R1, and a second window position 56.2 of the second window section A2 is centered with respect to the second readout section R2.

[0050] Figure 5 shows an analog sensor signal over time when applying a method for signal interference suppression in a further specific embodiment of the invention. The application of the general window function divides the sensor signal 26 into readout sections R. The first and second readout widths C1, C2 with the first and second window sections A1, A2 are the same and the first window position 56.1 with respect to the first readout section R1 differs from the second window position 56.2 with respect to the second readout section R2. This makes it possible to reduce a correlation between the period of the interference signal and the window sections and thus significantly suppress the interference signal. The window positions of the respective window sections can be randomly selected. The first window section A1 takes up the same proportion within the first readout section R1 as the second window section A2 within the second readout section R2.

Claims

Patent claims 1 . Method for signal interference suppression (30) of an analog sensor signal (26) of a microsensor (10) having a periodic interference signal (24), comprising the steps Acquiring (22) the sensor signal (26) of the microsensor (10) over time, sequentially applying (40) a general window function (42) to the acquired sensor signal (26) for dividing the sensor signal (26) into temporally sequential readout sections (R) having window sections (A), and at least integrating (44) the sensor signal (26) in the respective window sections (A), wherein the readout sections (R) each have a temporal readout width (C) and the window sections (A) each have a temporal window width (B), outputting a noise-suppressed sensor signal (31) that is conditioned as a function of the integration (44) in the individual window sections (A), characterized in that a first readout section (R1) of the readout sections (R) has a first readout width (C1) and a second readout section (R2) of the readout sections (R) has a second readout width (C2),a first window section (A1) of the window sections (A) located in the first readout section (R1) has a first window width (B1) and a second window section (A2) of the window sections (A) located in the second readout section (R2) has a second window width (B2), wherein the first readout width (C1) differs from the second readout width (C2), a first window position (56.1) of the first window section (A1) with respect to the associated first readout section (R1) differs from a second window position (56.2) of the second window section (A2) with respect to the associated second readout section (R2), and / or the first readout width (C1) and the second readout width (C2) differ from an integer multiple of a period (54) of the interference signal (24).

2. Method for signal interference suppression (30) according to claim 1, characterized in that if the first and second readout widths (C1, C2) deviate from an integer multiple of a period (54) of the interference signal (24), the first and second readout widths (C1, C2) are equal.

3. Method for signal interference suppression (30) according to claim 2, characterized in that the first and second window widths (B1, B2) are equal.

4. Method for signal interference suppression (30) according to one of the preceding claims, characterized in that the respective window section (A) is arranged centrally within the associated readout section (R).

5. Method for signal interference suppression (30) according to one of the preceding claims, characterized in that if the first window position (56.1) deviates from the second window position (56.2), the first and second readout widths (C1, C2) are equal.

6. Method for signal interference suppression (30) according to one of claims 1 to 4, characterized in that if the first readout width (C1) deviates from the second readout width (C2), the first and second window widths (B1, B2), which are predetermined in particular as a fixed component value of the assigned readout width (C1, C2), also deviate from one another.

7. Method for signal interference suppression (30) according to claim 6, characterized in that the respective value of the first and second readout widths (C1, C2) is randomly selected.

8. Method for signal interference suppression (30) according to one of the preceding claims, characterized in that the application (40) of the general window function (42) to the sensor signal (26) comprises a multiplication of the sensor signal (26) by the general window function (42).

9. Method for signal interference suppression (30) according to one of the preceding claims, characterized in that for each window section (A, A1, A2, A3) an integration value (46) formed by the integration (44) is calculated.

10. Method for sensor operation (18) of a microsensor (10), comprising the steps of providing (20) the microsensor (10), detecting (22) an analog sensor signal (26) of the microsensor (10) having a periodic interference signal (24) over time, Signal interference suppression (28) of the sensor signal (26) by a method for signal interference suppression (30) according to one of the preceding claims, conversion (32) of the analog sensor signal (31) suppressed by the signal interference suppression (28) into a digital sensor signal (34).

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