Method and device for suppressing channel low-frequency common-mode noise based on time division multiplexing difference

Abstract

The invention belongs to the field of common-mode noise suppression, and particularly discloses a method and device for suppressing channel low-frequency common-mode noise based on time division multiplexing difference, and the method comprises the steps: carrying out the time division multiplexing of a to-be-detected signal and a reference signal, and outputting the to-be-detected signal and the reference signal to a same channel, and obtaining a multiplexing signal; time division multiplexing is used for periodically and alternately outputting a signal to be measured and a reference signal in a time-sharing manner; sampling the multiplexing signals, and averaging sampling data in each half period to obtain a group of first superposed signal average values and a group of second superposed signal average values; respectively interpolating the group of first superposed signal average values and the group of second superposed signal average values to obtain the group of interpolated first superposed signal average values and the group of interpolated second superposed signal average values; and performing differential subtraction on the average value of the group of first superposed signals after interpolation and the average value of the group of second superposed signals after interpolation to obtain measurement data. According to the invention, the low-frequency common-mode noise can be effectively suppressed.

Description

Technical Field

[0001] The present application belongs to the field of common mode noise suppression, and more specifically, to a method and device for suppressing low-frequency common mode noise of a channel based on time division multiplexing differential. Background Art

[0002] In precision optical measurement, electronic instrument measurement and other systems, noise is a key factor affecting system performance indicators. In particular, in application scenarios that require long-term high-precision measurement, the impact of low-frequency drift noise is particularly significant, seriously affecting the stability and reliability of the system. Low-frequency drift noise refers to the signal deviation caused by factors such as temperature, vibration, and device aging during long-term operation, and its frequency is usually less than 1 Hz.

[0003] The traditional method of suppressing low-frequency noise is mainly the common-mode suppression method. This method suppresses common-mode noise by differential input. Generally, it is necessary to balance the signal to be measured and the reference signal. The common-mode suppression ratio is limited by the matching accuracy of components. The circuit structure design is relatively complex. The consistency of the test channels cannot be exactly the same, and the noise suppression effect is limited. In some scenarios that pay special attention to low-frequency signal measurement, the above method cannot effectively resist the influence of low-frequency noise. Therefore, how to suppress low-frequency noise more effectively is an important issue worthy of discussion. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of this application is to provide a method and device for differentially suppressing low-frequency common-mode noise of a channel based on time-division multiplexing, aiming to solve the problem that the traditional circuit for suppressing low-frequency noise of the channel is complex and has poor effect.

[0005] To achieve the above objectives, in a first aspect, the present application provides a method for differentially suppressing low-frequency common-mode noise of a channel based on time division multiplexing, comprising: The test signal and the reference signal are time-division multiplexed and output to the same channel to obtain a multiplexed signal; the time-division multiplexing is to output the test signal and the reference signal alternately in a periodic time-division manner; within one cycle of the multiplexed signal, half of the cycle is a first superimposed signal obtained by mixing the test signal with the channel noise at this time, and the other half of the cycle is a second superimposed signal obtained by mixing the reference signal with the channel noise at this time; The multiplexed signal is sampled, and the sampled data in each half cycle are averaged to obtain a group of first superimposed signal average values ​​and a group of second superimposed signal average values; the sampling times of two adjacent superimposed signal average values ​​in the same group differ by one cycle, and the sampling times of the superimposed signal average values ​​with the same sequence number in the two groups differ by half a cycle; Interpolating the group of first superimposed signal average values ​​and the group of second superimposed signal average values ​​respectively to obtain a group of first superimposed signal average values ​​after interpolation and a group of second superimposed signal average values ​​after interpolation; the interpolation is used to obtain the superimposed signal average value at the intermediate sampling time according to the two adjacent superimposed signal average values, so that the sampling times of the superimposed signal average values ​​with the same sequence number in the two groups are aligned after interpolation; A group of interpolated first superimposed signal average values ​​and a group of interpolated second superimposed signal average values ​​are differentially subtracted to obtain measurement data; the measurement data is the difference between the signal to be measured and the reference signal measured in each half cycle.

[0006] It should be noted that the present application controls the measured signal and the reference signal to pass through the same sensing channel and sampling channel through time division multiplexing, so that the same channel noise is introduced into the measured signal and the reference signal. After that, through subsequent interpolation and differential processing, the influence of the channel low-frequency common-mode noise can be better suppressed, thereby ensuring the measurement accuracy of the measured signal.

[0007] In a possible implementation, the interpolation is linear interpolation, and the linear interpolation is: averaging two adjacent superimposed signal average values ​​and then inserting a corresponding value between the two superimposed signal average values.

[0008] In a possible implementation, the signal to be tested and the reference signal are time-division multiplexed and output to the same channel, including: The output of the signal to be tested and the reference signal are controlled by a periodic square wave timing signal, so that the signal to be tested and the reference signal are output to the same channel in time division multiplexing; when the square wave timing signal is at a high level, the signal to be tested is output to the channel, and when the square wave timing signal is at a low level, the reference signal is output to the channel; or when the square wave timing signal is at a high level, the reference signal is output to the channel, and when the square wave timing signal is at a low level, the signal to be tested is output to the channel.

[0009] In a possible implementation, a clock used for sampling the multiplexed signal is co-sourced with a clock of the square wave timing signal; and / or a time interval for sampling the multiplexed signal is less than or equal to a half period of the square wave timing signal.

[0010] In a possible implementation, when performing the differential subtraction, the transfer function H(f) of the channel noise in the frequency domain is: H(f) =1–e -j2πfτ Where f is the frequency of the channel noise and τ is half a period.

[0011] In a second aspect, the present application provides a signal measurement method. When the signal to be measured is a low-frequency signal, the signal to be measured is measured using the method described in the first aspect or any possible implementation of the first aspect.

[0012] In a third aspect, the present application provides a device for differentially suppressing low-frequency common-mode noise of a channel based on time-division multiplexing, comprising: a time-division multiplexing module, a signal sampling module, and a data processing module; The time division multiplexing module is used to output the test signal and the reference signal to the same channel in time division multiplexing to obtain a multiplexed signal; within one cycle of the multiplexed signal, half of the cycle is a first superimposed signal obtained by mixing the test signal with the channel noise at this time, and the other half of the cycle is a second superimposed signal obtained by mixing the reference signal with the channel noise at this time; The signal sampling module is used to sample the multiplexed signal and average the sampled data in each half cycle to obtain a group of first superimposed signal average values ​​and a group of second superimposed signal average values; the sampling times of two adjacent superimposed signal average values ​​in the same group differ by one cycle, and the sampling times of the superimposed signal average values ​​with the same sequence number in the two groups differ by half a cycle; The data processing module is used to interpolate the group of first superimposed signal average values ​​and the group of second superimposed signal average values ​​respectively to obtain a group of interpolated first superimposed signal average values ​​and a group of interpolated second superimposed signal average values; the interpolation is used to obtain the superimposed signal average value at the middle sampling time according to the two adjacent superimposed signal average values, so that the sampling times of the superimposed signal average values ​​with the same sequence number in the two groups are aligned after interpolation; and to perform differential subtraction on the interpolated group of first superimposed signal average values ​​and the interpolated group of second superimposed signal average values ​​to obtain measurement data; the measurement data is the difference between the signal to be measured and the reference signal measured in each half cycle.

[0013] In a possible implementation, the data processing module is used to perform linear interpolation on the group of first superimposed signal average values ​​and the group of second superimposed signal average values ​​respectively; the linear interpolation is: averaging two adjacent superimposed signal average values ​​and then inserting a corresponding value between the two superimposed signal average values.

[0014] In a possible implementation, the device further includes: a timing generation module and a time-sharing output module; The timing generation module is used to provide a periodic square wave timing signal to the time division multiplexing module and the time division output module; The time division multiplexing module is used to output the signal to be tested and the reference signal to the same channel in time division multiplexing under the drive of the square wave timing signal; when the square wave timing signal is at a high level, the signal to be tested is output to the channel, and when the square wave timing signal is at a low level, the reference signal is output to the channel, or when the square wave timing signal is at a high level, the reference signal is output to the channel, and when the square wave timing signal is at a low level, the signal to be tested is output to the channel; The time-sharing output module is used to output a group of first superimposed signal average values ​​and a group of second superimposed signal average values ​​obtained by the signal sampling module in a time-sharing manner under the triggering of the square wave timing signal; the timing of the time-sharing output is the same as the timing of the time-division multiplexing output.

[0015] In a possible implementation, a clock used for sampling the multiplexed signal is co-sourced with a clock of the square wave timing signal; and / or a time interval for sampling the multiplexed signal is less than or equal to a half period of the square wave timing signal.

[0016] In a possible implementation manner, when the data processing module performs the differential subtraction, the transfer function H(f) of the channel noise in the frequency domain is: H(f) =1–e -j2πfτ Where f is the frequency of the channel noise and τ is half a period.

[0017] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art: The present application provides a method and device for differentially suppressing low-frequency common-mode noise of a channel based on time-division multiplexing. The method controls a signal to be measured and a reference signal to pass through the same sensing channel and sampling channel in a time-division multiplexing manner, so that the same channel noise is introduced into the signal to be measured and the reference signal. The channel noise is then effectively deducted through subsequent interpolation and differential processing. By studying the frequency domain transfer function of the above-mentioned channel noise, it is found that the above-mentioned scheme can have a better suppression effect on the low-frequency channel noise, thereby ensuring the measurement accuracy of the signal to be measured. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a flow chart of a method for differentially suppressing low-frequency common-mode noise of a channel based on time-division multiplexing provided in an embodiment of the present application.

[0019] Figure 2 It is a structural diagram of a device for suppressing low-frequency common-mode noise of a channel based on time-division multiplexing differential provided in an embodiment of the present application.

[0020] Figure 3 It is a schematic diagram of the signal waveform and timing provided in the embodiment of the present application.

[0021] Figure 4 It is a data waveform diagram of signal sampling, time-sharing output, interpolation and differential processing provided in an embodiment of the present application.

[0022] Figure 5 It is a schematic diagram of the signal and data processing process provided in the embodiment of the present application.

[0023] In all the drawings, the same figure marks are used to represent the same elements or structures, wherein: 10 is a structure of an object to be measured, 11 is a signal module to be measured, 12 is a reference signal module; 20 is a time division multiplexing and time division output structure, 21 is a timing generation module, 22 is a time division multiplexing module, 23 is a signal sampling module, 24 is a time division output module, 25 is a channel noise module, 26 is an addition module; 30 is a data processing structure, 31 is a first interpolation module, 32 is a second interpolation module, 33 is a differential module, and 34 is a measurement data module. DETAILED DESCRIPTION

[0024] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0025] First, the technical terms involved in the embodiments of the present application are introduced.

[0026] (1) Signal to be tested In electronic testing, the signal under test is the signal that needs to be measured or analyzed. It may be the output of an electronic device or system to evaluate whether its performance meets the expected standards or specifications.

[0027] (2) Reference signal A reference signal is a signal used as a benchmark for comparison. In measurement and testing, a reference signal is usually a known, stable signal used to calibrate measurement equipment or as a standard of comparison to ensure the accuracy of measurement results.

[0028] (3) Common mode noise Common-mode noise refers to noise signals that appear simultaneously on two or more conductors in a circuit, usually caused by external environmental interference, power supply spurious, noise introduced by the ground, etc.

[0029] The embodiments of the present application are described below in conjunction with the drawings in the embodiments of the present application.

[0030] Figure 1 1 is a flow chart of a method for suppressing low-frequency common-mode noise of a channel based on time-division multiplexing differential provided in an embodiment of the present application. Figure 1 As shown, the following steps are included: Step S101, outputting the test signal and the reference signal to the same channel by time division multiplexing to obtain a multiplexed signal; the time division multiplexing is to output the test signal and the reference signal alternately in a periodic time division; within one cycle of the multiplexed signal, half of the cycle is a first superimposed signal obtained by mixing the test signal and the channel noise at this time, and the other half of the cycle is a second superimposed signal obtained by mixing the reference signal and the channel noise at this time; In one example, the output of the signal to be tested and the reference signal are controlled by a periodic square wave timing signal, so that the signal to be tested and the reference signal are output to the same channel in time division multiplexing; when the square wave timing signal is at a high level, the signal to be tested is output to the channel, and when the square wave timing signal is at a low level, the reference signal is output to the channel, or when the square wave timing signal is at a high level, the reference signal is output to the channel, and when the square wave timing signal is at a low level, the signal to be tested is output to the channel.

[0031] Step S102, sampling the multiplexed signal, and averaging the sampled data in each half cycle to obtain a group of first superimposed signal average values ​​and a group of second superimposed signal average values; the sampling times of two adjacent superimposed signal average values ​​in the same group differ by one cycle, and the sampling times of the superimposed signal average values ​​with the same sequence number in the two groups differ by half a cycle; In one example, the clock used for sampling the multiplexed signal is the same source as the clock of the square wave timing signal; further, the time interval for sampling the multiplexed signal is less than or equal to half a period of the square wave timing signal.

[0032] Step S103, interpolating a group of first superimposed signal average values ​​and a group of second superimposed signal average values ​​respectively to obtain a group of first superimposed signal average values ​​after interpolation and a group of second superimposed signal average values ​​after interpolation; the interpolation is used to obtain the superimposed signal average value at the intermediate sampling time according to the average values ​​of two adjacent superimposed signals, so that the sampling times of the superimposed signal average values ​​with the same sequence number in the two groups are aligned after interpolation; In an example, the above interpolation is linear interpolation, and the linear interpolation is: averaging the average values ​​of two adjacent superimposed signals and then inserting the corresponding value between the average values ​​of the two superimposed signals.

[0033] Step S104, performing differential subtraction on a group of interpolated first superimposed signal average values ​​and a group of interpolated second superimposed signal average values ​​to obtain measurement data; the measurement data is the difference between the signal to be measured and the reference signal measured in each half cycle.

[0034] In a more specific embodiment, Figure 2 is a structural diagram of a device for suppressing low-frequency common-mode noise of a channel based on time-division multiplexing differential provided in an embodiment of the present application, such as Figure 2As shown, the device includes a time division multiplexing and time division output mechanism 20 and a data processing mechanism 30; the corresponding test object is: the object mechanism 10 to be tested.

[0035] The object to be tested 10 includes a signal to be tested 11 and a reference signal 12. The signal to be tested can be denoted as s 1 (t), the reference signal can be recorded as s 2 (t), the goal of the embodiment of the present application is to accurately measure the difference between the measured signal 11 and the reference signal 12 1 (t)-s 2 (t).

[0036] The time division multiplexing and time division output mechanism 20 includes: a timing generation module 21, a time division multiplexing module 22, a signal sampling module 23, and a time division output module 24; in order to vividly describe the introduction of channel noise, the channel noise of the test signal and the reference signal multiplexed in one channel is vividly represented as a channel noise module 25 and an addition module 26. In the process of measuring the test signal 11 and the reference signal 12, it is inevitable to be interfered by the channel noise 25. Further exemplarily, the above-mentioned channel noise may be introduced by the timing generation module 21, the time division multiplexing module 22, the signal sampling module 23, the time division output module 24, and the transmission lines between the modules.

[0037] For example, the signal to be measured 11 and the reference signal 12 are respectively Figure 3 The output signal of the timing generation module is Figure 3 In one example, when the square wave is at a high level, B1 is connected to A1 and is superimposed with the channel noise 25 in the adding module 26; when the square wave is at a low level, B1 is connected to A2 and is superimposed with the channel noise 25 in the adding module 26. Therefore, the data after B1 and the channel noise are superimposed is Figure 3 Signal C1 shown in (c).

[0038] In general, the signal to be measured and the reference signal contain common mode noise that varies with time; however, in this embodiment, for the sake of simplicity, the reference signal uses a constant offset, and the signal to be measured contains the same offset. In addition, according to the noise characteristics of the actual circuit channel components, the channel noise in this embodiment uses 1 / f noise. The power spectrum density of this type of noise is inversely proportional to the frequency, and the noise data has obvious drift in the time domain.

[0039] After sampling, the signal C1 obtains a discrete digital signal D1, such as Figure 4As shown in (a) in the figure. In this embodiment, the time interval of signal sampling is less than or equal to the half period of the square wave, so D1 has multiple data points at high level and low level. The average value of some data points at high level is obtained by intercepting and averaging to obtain E1, and the average value of some data points at low level is obtained by intercepting and averaging to obtain E2.

[0040] The data processing mechanism 30 includes a first interpolation module 31, a second interpolation module 32, a difference module 33 and measurement data 34. The first interpolation module 31 performs linear interpolation on the sampled data E1 of the measured signal; the second interpolation module 32 performs linear interpolation on the sampled data E2 of the reference signal. The sampling rate of the interpolated data F1 or F2 is twice the sampling rate of E1 or E2 before interpolation, and the sampling time of the F1 data is the same as that of the F2 data.

[0041] Further preferably, the above linear interpolation can be to insert the average value at the middle moment of adjacent data. The high-level sampling data separated by one square wave cycle are averaged in pairs as the interpolation at the middle moment to obtain discrete data separated by half a square wave cycle. The low level is processed in the same way to obtain two sets of data with synchronized sampling time, and subtraction is performed in the differential module.

[0042] Since there is a time delay of half a square wave period between the high-level sampling data E1 and the low-level sampling data E2, directly differentiating E1 and E2 will result in noise terms at different times being subtracted. Considering the randomness of noise, it is difficult to completely suppress common-mode noise by direct subtraction. Based on this, the interpolated data F1 and F2 are used for differentiation, and their sampling times are synchronized, such as Figure 4 Output F1 and F2 to the differential module for subtraction, and obtain differential data G1 as shown in (b). Figure 4 As shown in (c). Figure 4 (d) is the result of differential data for a long time. It can be seen that the method described in the present application can significantly suppress the influence of channel common-mode low-frequency noise.

[0043] In traditional methods, the signal to be measured and the reference signal need to pass through different sensing channels and different sampling channels, which will introduce different channel noises. Assume that the noises of the two channels are n 1 (t) and n 2 (t), the difference processing cannot deduct n 1 (t)-n 2 (t) Noise.

[0044] Therefore, we propose a method based on time division multiplexing to differentially suppress channel common mode low-frequency noise, and give the principle of noise suppression by this method, such as Figure 5 This method can time-division multiplex the sensing channel and the acquisition channel to avoid the introduction of different channel noises by two or more channels. The specific process is: the signal to be measured s1 (t) and the reference signal s 2 (t) After passing through the dual multiplexer, the output signal is B1. This signal has gone through the same sensing channel and acquisition channel. During this process, s 1 (t) and s 2 (t) is superimposed with the same source noise n(t), but there is a fixed time delay in the moment of superimposing the noise. The signal B1 is superimposed with the noise to become C1, and C1 becomes D1 after signal sampling. The time-sharing output module outputs D1 as two discrete signals E1 and E2 according to the square wave timing. The period of the square wave timing is T, and the sampling time interval of the signal sampling module is Ts. The relationship between the two is T / 2≥Ts. Therefore, when the square wave is at a high level or a low level, there are several sampling data greater than 1. When the timing is at a high level, the average value of several sampling data is taken to obtain E1, which can be written as s 1 [k·T]+n[k·T] (where k is a positive integer); Similarly, when the timing is low, taking a number of sampled data and averaging the obtained E2 can be written as s 2 [(k- )T]+n[(k- )T]. Here, the sampling times of E1 and E2 are inconsistent, with a difference of half a square wave period.

[0045] In order to ensure that the two sets of data are sampled at the same time, data interpolation can be used. The specific process is as follows: 1 [k·T]+n[k·T] and s 1 The interpolated data obtained by inserting the average value of the two points at the middle time of [(k-1)T]+n[(k-1)T] is s 1插 [(k- )T]+n 插 [(k- )T]; in E2 adjacent sampling data s 2 [(k- )T]+n[(k- )T] and s 2 [(k+ )T]+n[(k+ The interpolated data obtained by inserting the average value of the two points at the middle time of )T] is s 2插 [k·T]+n 插 [k·T] The sampling time interval is obtained by combining the interpolation data with the measured data. The integrated data, that is, the average value of a set of first superposition signals after interpolation, can be expressed as: s 1 [(k-1)T]+n[(k-1)T],s 1插 [(k- )T]+n 插[(k- )T]、s 1 [k·T]+n[k·T]......(k is a positive integer); the average value of a set of second superposition signals after interpolation can be expressed as: s 2 [(k- )T]+n[(k- )T]、s 2插 [k·T]+n 插 [k·T], s 2 [(k+ )T]+n[(k+ )T]......(k is a positive integer).

[0046] Furthermore, to simplify the representation, the above interpolated data can be expressed as The periodic integration is expressed as: The average value of the first superposition signal after interpolation is: s 1插 [ k·T]+n 插 [ k·T]...... (k is a positive integer); the average value of a set of second superposition signals after interpolation can be expressed as: s 2插 [ k·T]+n' 插 [ k·T]...... (k is a positive integer); half of the above interpolation data is the actual sampled data, and the other half is the interpolated data. The corresponding expression can be: high level data is s 1插 [ k·T]+n 插 [ k·T] (signal to be measured + channel noise), low-level data is s 2插 [ k·T]+n' 插 [ k·T] (reference signal + channel noise). At this point, two sets of time-synchronized data can be obtained. The two sets of data are subtracted using the differential module to obtain the final measurement data.

[0047] The measurement data obtained in this application has a significant suppression effect on the low-frequency components in the channel noise. The principle is that the subtraction of the same source noise before and after still has the effect of noise suppression. For easy understanding, consider the process of continuous signal processing: the channel noise at a high level is recorded as n(t), and its frequency domain expression after Fourier transform is N(f). The channel noise at a low level is n(t-τ). Considering the time shift characteristics of Fourier transform, its frequency domain expression after Fourier transform is N(f) · e -j2πfτBy performing differential processing on these two sets of data, the entire system processes the noise n(t) in the time domain as n(t) – n(t-τ), and its transfer function in the frequency domain can be written as H(f) = [ N(f)– N(f) ·e -j2πfτ ] / N(f) =1–e -j2πfτ , where f is the channel noise frequency. By analyzing this transfer function, it is easy to know that when the frequency f is smaller, H(f) is closer to 0, which is equivalent to the effect of a high-pass filter, that is, the system has a good suppression effect on the low-frequency components in the common-mode noise, so the method described in this application can effectively suppress the low-frequency common-mode noise of the channel.

[0048] It can be further understood that the method provided by the above embodiment of the present application is very suitable for measuring low-frequency test signals, so as to effectively suppress low-frequency common-mode noise and ensure high measurement accuracy for the above low-frequency test signals. It is particularly suitable for the case where the reference signal and the test signal go through the same acquisition channel and sensing channel, and the high-frequency component in the channel noise is smaller than the low-frequency component, so as to improve the suppression effect of common-mode noise, especially low-frequency drift noise.

[0049] It should be understood that expressions such as "including" and "may include" that may be used in the present application indicate the existence of the disclosed functions, operations, or constituent elements, and do not limit one or more additional functions, operations, and constituent elements. In the present application, terms such as "including" and / or "having" may be interpreted as indicating specific characteristics, numbers, operations, constituent elements, components, or combinations thereof, but may not be interpreted as excluding the existence or possibility of adding one or more other characteristics, numbers, operations, constituent elements, components, or combinations thereof.

[0050] In addition, in the present application, the expression "and / or" includes any and all combinations of the associated listed words. For example, the expression "A and / or B" may include A, may include B, or may include both A and B.

[0051] In the description of the embodiments of the present application, it should be noted that, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Among them, "fixed connection" means that the relative position relationship after connection remains unchanged. "Rotational connection" means that the two are connected to each other and can rotate relative to each other after connection. "Sliding connection" means that the two are connected to each other and can slide relative to each other after connection. The directional terms mentioned in the embodiments of the present application, such as "top", "bottom", "inside", "outside", "left", "right", etc., are only reference directions of the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present application, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the embodiments of the present application.

[0052] In addition, in the embodiments of the present application, the mathematical concepts mentioned are symmetry, equality, parallelism, verticality, etc. These limitations are all for the current state of the art, rather than being absolutely strict definitions in a mathematical sense, and allow a small amount of deviation, approximation to symmetry, approximation to equality, approximation to parallelism, approximation to verticality, etc. are all possible. For example, A and B are parallel, which means that A and B are parallel or approximately parallel, and the angle between A and B can be between 0 and 10 degrees. A and B are perpendicular, which means that A and B are perpendicular or approximately perpendicular, and the angle between A and B can be between 80 and 100 degrees.

[0053] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for differentially suppressing low-frequency common-mode noise of a channel based on time division multiplexing, characterized in that: include: The test signal and the reference signal are time-division multiplexed and output to the same channel to obtain a multiplexed signal; the time-division multiplexing is to output the test signal and the reference signal alternately in a periodic time-division manner; within one cycle of the multiplexed signal, half of the cycle is a first superimposed signal obtained by mixing the test signal with the channel noise at this time, and the other half of the cycle is a second superimposed signal obtained by mixing the reference signal with the channel noise at this time; The multiplexed signal is sampled, and the sampled data in each half cycle are averaged to obtain a group of first superimposed signal average values ​​and a group of second superimposed signal average values; the sampling times of two adjacent superimposed signal average values ​​in the same group differ by one cycle, and the sampling times of the superimposed signal average values ​​with the same sequence number in the two groups differ by half a cycle; Interpolating the group of first superimposed signal average values ​​and the group of second superimposed signal average values ​​respectively to obtain a group of first superimposed signal average values ​​after interpolation and a group of second superimposed signal average values ​​after interpolation; the interpolation is used to obtain the superimposed signal average value at the intermediate sampling time according to the two adjacent superimposed signal average values, so that the sampling times of the superimposed signal average values ​​with the same sequence number in the two groups are aligned after interpolation; A group of interpolated first superimposed signal average values ​​and a group of interpolated second superimposed signal average values ​​are differentially subtracted to obtain measurement data; the measurement data is the difference between the signal to be measured and the reference signal measured in each half cycle.

2. The method according to claim 1, characterized in that: The interpolation is linear interpolation, and the linear interpolation is: averaging the average values ​​of two adjacent superimposed signals and then inserting the corresponding value between the average values ​​of the two superimposed signals.

3. The method according to claim 1, characterized in that The test signal and reference signal are time-division multiplexed and output to the same channel, including: The output of the signal to be tested and the reference signal are controlled by a periodic square wave timing signal, so that the signal to be tested and the reference signal are output to the same channel in time division multiplexing; when the square wave timing signal is at a high level, the signal to be tested is output to the channel, and when the square wave timing signal is at a low level, the reference signal is output to the channel; or when the square wave timing signal is at a high level, the reference signal is output to the channel, and when the square wave timing signal is at a low level, the signal to be tested is output to the channel.

4. The method according to claim 3, characterized in that: The clock used for sampling the multiplexed signal is of the same source as the clock of the square wave timing signal; and / or the time interval for sampling the multiplexed signal is less than or equal to half a period of the square wave timing signal.

5. The method according to any one of claims 1 to 4, characterized in that: When performing the differential subtraction, the transfer function H(f) of the channel noise in the frequency domain is: H(f) =1–e -j2πfτ Where f is the frequency of the channel noise and τ is half a period.

6. A signal measurement method, characterized in that: When the signal to be measured is a low-frequency signal, the method according to any one of claims 1 to 5 is used to measure the signal to be measured.

7. A device for suppressing low-frequency common-mode noise of a channel based on time-division multiplexing differential, characterized in that: include: Time division multiplexing module, signal sampling module and data processing module; The time division multiplexing module is used to output the test signal and the reference signal to the same channel in time division multiplexing to obtain a multiplexed signal; within one cycle of the multiplexed signal, half of the cycle is a first superimposed signal obtained by mixing the test signal with the channel noise at this time, and the other half of the cycle is a second superimposed signal obtained by mixing the reference signal with the channel noise at this time; The signal sampling module is used to sample the multiplexed signal and average the sampled data in each half cycle to obtain a group of first superimposed signal average values ​​and a group of second superimposed signal average values; the sampling times of two adjacent superimposed signal average values ​​in the same group differ by one cycle, and the sampling times of the superimposed signal average values ​​with the same sequence number in the two groups differ by half a cycle; The data processing module is used to interpolate the group of first superimposed signal average values ​​and the group of second superimposed signal average values ​​respectively to obtain a group of interpolated first superimposed signal average values ​​and a group of interpolated second superimposed signal average values; the interpolation is used to obtain the superimposed signal average value at the middle sampling time according to the two adjacent superimposed signal average values, so that the sampling times of the superimposed signal average values ​​with the same sequence number in the two groups are aligned after interpolation; and to perform differential subtraction on the interpolated group of first superimposed signal average values ​​and the interpolated group of second superimposed signal average values ​​to obtain measurement data; the measurement data is the difference between the signal to be measured and the reference signal measured in each half cycle.

8. The device according to claim 7, characterized in that The data processing module is used to perform linear interpolation on the group of first superimposed signal average values ​​and the group of second superimposed signal average values ​​respectively; the linear interpolation is: averaging two adjacent superimposed signal average values ​​and then inserting the corresponding value between the two superimposed signal average values.

9. The device according to claim 7, characterized in that It also includes: a timing generation module and a time-sharing output module; The timing generation module is used to provide a periodic square wave timing signal to the time division multiplexing module and the time division output module; The time division multiplexing module is used to output the signal to be tested and the reference signal to the same channel in time division multiplexing under the drive of the square wave timing signal; when the square wave timing signal is at a high level, the signal to be tested is output to the channel, and when the square wave timing signal is at a low level, the reference signal is output to the channel, or when the square wave timing signal is at a high level, the reference signal is output to the channel, and when the square wave timing signal is at a low level, the signal to be tested is output to the channel; The time-sharing output module is used to output a group of first superimposed signal average values ​​and a group of second superimposed signal average values ​​obtained by the signal sampling module in a time-sharing manner under the triggering of the square wave timing signal; the timing of the time-sharing output is the same as the timing of the time-division multiplexing output.

10. The device according to claim 9, characterized in that The clock used for sampling the multiplexed signal is of the same source as the clock of the square wave timing signal; and / or the time interval for sampling the multiplexed signal is less than or equal to half a period of the square wave timing signal.

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