A method and system for detecting phase synchronization between signals

Abstract

The present application provides a method and system for detecting phase synchronization between signals, the method comprising acquiring a first signal and a second signal; performing a discrete Fourier transform on the first signal to obtain a first Fourier spectrum, and performing a discrete Fourier transform on the second signal to obtain a second Fourier spectrum; calculating the cross-spectrum of the first signal and the second signal based on the first Fourier spectrum and the second Fourier spectrum; calculating the full complex plane mean ratio and the half complex plane distribution ratio based on the cross-spectrum; determining a target measurement value based on the full complex plane mean ratio and the half complex plane distribution ratio, so as to determine the degree of phase synchronization between the first signal and the second signal based on the target measurement value. The method can comprehensively consider the full complex plane mean ratio and the half complex plane distribution ratio based on the imaginary part of the cross spectrum, thereby more accurately detecting the degree of phase synchronization between the signals. At the same time, different calculation methods can be matched according to different polarity types of the imaginary part of the cross spectrum to improve the efficiency of phase synchronization detection between signals.

Description

Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a method and system for detecting phase synchronization between signals. Background Art

[0002] For a signal, energy determines its amplitude, while the phase of its frequency and other related components determines its shape. The phase of these components is related to the signal's generation process, while the signal's shape is related to its encoding, which can be determined through phase analysis. Therefore, analyzing the signal's phase—that is, performing phase analysis—is necessary when analyzing its shape.

[0003] When performing phase analysis on a signal, a phase synchronization analysis method can be used. The weighted phase lag index (WPLI) is a frequency-domain phase synchronization parameter. When performing phase synchronization analysis on a signal in the frequency domain, the weighted phase lag index WPLI can be used to measure it. The weighted phase lag index WPLI can be used to statistically calculate the sign distribution of the imaginary part of the cross-spectrum and weight it using the absolute value of the imaginary part of the cross-spectrum. The value range of the weighted result is 0-1. The closer the result is to 0, the weaker the synchronization between the two signals. The closer the result is to 1, the stronger the phase synchronization between the two signals.

[0004] Although the above method can analyze the phase synchronization relationship between signals, the analysis method of the weighted phase lag index WPLI is limited to the case where the imaginary part of the cross spectrum is concentrated in positive or negative. Therefore, when the imaginary part of the cross spectrum is not the single dominant polarity mentioned above, such as when the imaginary part of the cross spectrum has both positive and negative phases, and the two phases are symmetrically distributed about the real axis, according to the calculation method of the weighted phase lag index WPLI, due to the cancellation of the symmetrical positive and negative polarities, the phase synchronization correlation calculated by this method is 0, that is, a completely non-phase-locked result will be obtained. In fact, if the two dominant phases are concentrated in a position far away from the real axis, there is phase lock, that is, the actual correlation should be greater than 0. Therefore, when using the weighted phase lag index WPLI method to analyze the phase synchronization between signals, there are errors, resulting in its low accuracy. Summary of the Invention

[0005] Some embodiments of the present application provide a method and system for detecting phase synchronization between signals.

[0006] In a first aspect, some embodiments of the present application provide a method for detecting phase synchronization between signals, including:

[0007] Acquire a first signal and a second signal;

[0008] Performing a discrete Fourier transform on the first signal to obtain a first Fourier spectrum, and performing a discrete Fourier transform on the second signal to obtain a second Fourier spectrum;

[0009] Calculating a cross spectrum of the first signal and the second signal according to the first Fourier spectrum and the second Fourier spectrum;

[0010] Calculating a full complex plane mean ratio and a half complex plane distribution ratio according to the cross spectrum;

[0011] A target metric value is determined according to the full complex plane mean ratio and the half complex plane distribution ratio, so as to determine a phase synchronization degree between the first signal and the second signal according to the target metric value.

[0012] In some embodiments, the step of calculating a cross spectrum of the first signal and the second signal based on the first Fourier spectrum and the second Fourier spectrum includes:

[0013] Acquire the first Fourier spectrum and the second Fourier spectrum;

[0014] calculating a complex conjugate of the second Fourier spectrum according to the second Fourier spectrum;

[0015] A product operation is performed on the first Fourier spectrum and the complex conjugate to obtain a cross spectrum of the first signal and the second signal.

[0016] In some embodiments, the cross spectrum of the first signal and the second signal is calculated based on the first Fourier spectrum and the second Fourier spectrum according to the following formula:

[0017] X(f)=Z1(f)Z2 * (f);

[0018] Wherein, f is the spectrum generated by performing discrete Fourier transform on the first signal and the second signal; X(f) is the cross spectrum of the first signal and the second signal; Z1(f) is the first Fourier spectrum; Z2 * (f) is the complex conjugate of the second Fourier spectrum.

[0019] In some embodiments, the step of calculating the full complex plane mean ratio based on the cross spectrum includes:

[0020] Obtaining a cross-spectrum imaginary part according to the cross-spectrum;

[0021] Calculating an average value of the imaginary part of the cross spectrum imaginary part according to the cross spectrum imaginary part;

[0022] Calculate the imaginary part mean absolute value of the imaginary part of the cross spectrum according to the imaginary part average value;

[0023] Calculating the absolute value of the imaginary part of the cross spectrum imaginary part according to the cross spectrum imaginary part;

[0024] Calculating the absolute mean of the imaginary parts of the cross-spectrum imaginary parts according to the absolute values ​​of the imaginary parts;

[0025] A ratio operation is performed on the absolute value of the imaginary part mean and the absolute mean of the imaginary part to obtain a full complex plane mean ratio of the imaginary part of the cross spectrum.

[0026] In some embodiments, a ratio operation is performed on the imaginary part mean absolute value and the imaginary part absolute mean according to the following formula:

[0027]

[0028] Wherein, W is the full complex plane mean ratio, X is the cross spectrum of the first signal and the second signal, Im(X) is the imaginary part of the cross spectrum, E represents the average value, and abs is the absolute value function.

[0029] In some embodiments, the step of calculating the half-complex plane distribution ratio according to the cross spectrum includes:

[0030] Obtaining a cross-spectrum imaginary part according to the cross-spectrum;

[0031] Calculating the absolute value of the imaginary part of the cross spectrum imaginary part according to the cross spectrum imaginary part;

[0032] Calculating the median function of the imaginary part of the cross spectrum according to the absolute value of the imaginary part;

[0033] Obtaining the probability percentile of the imaginary part of the cross spectrum;

[0034] A ratio operation is performed on the median function and the probability percentile to obtain a half-complex plane distribution ratio.

[0035] In some embodiments, a ratio operation is performed on the median function and the probability percentile according to the following formula:

[0036]

[0037] Wherein, L is the half-complex plane distribution ratio, X is the cross spectrum of the first signal and the second signal, Im(X) is the imaginary part of the cross spectrum, abs is the absolute value function, ratio is the probability of the imaginary part of the cross spectrum, and percentile is the percentile of the probability.

[0038] In some embodiments, the step of determining a target metric value based on the full complex plane mean ratio and the half complex plane distribution ratio includes:

[0039] comparing the full complex plane mean ratio and the half complex plane distribution ratio;

[0040] If the full complex plane mean ratio is greater than the half complex plane distribution ratio, taking the full complex plane mean ratio as a target measurement value;

[0041] If the full complex plane mean ratio is smaller than the half complex plane distribution ratio, the half complex plane distribution ratio is used as a target metric value.

[0042] In some embodiments, the method further comprises:

[0043] Identifying a polarity type of the imaginary part of the cross spectrum, wherein the polarity type includes single polarity and symmetrical polarity;

[0044] If the polarity type is the single polarity, detecting a degree of phase synchronization between the first signal and the second signal based on the full complex plane mean ratio;

[0045] If the polarity type is the symmetrical polarity, the degree of phase synchronization between the first signal and the second signal is detected based on the half-complex plane distribution ratio.

[0046] In a second aspect, some embodiments of the present application provide a system for detecting phase synchronization between signals, including:

[0047] Signal acquisition module: acquires the first signal and the second signal;

[0048] A Fourier transform module; performing a discrete Fourier transform on the first signal to obtain a first Fourier spectrum, and performing a discrete Fourier transform on the second signal to obtain a second Fourier spectrum;

[0049] A cross spectrum calculation module is configured to calculate a cross spectrum of the first signal and the second signal according to the first Fourier spectrum and the second Fourier spectrum;

[0050] Ratio calculation module: calculates the full complex plane mean ratio and the half complex plane distribution ratio according to the cross spectrum;

[0051] A target detection module is configured to determine a target measurement value according to the full complex plane mean ratio and the half complex plane distribution ratio, so as to determine a phase synchronization degree between the first signal and the second signal according to the target measurement value.

[0052] As can be seen from the above technical solutions, some embodiments of the present application provide a method and system for detecting phase synchronization between signals, the method comprising acquiring a first signal and a second signal; performing a discrete Fourier transform on the first signal to obtain a first Fourier spectrum, and performing a discrete Fourier transform on the second signal to obtain a second Fourier spectrum; calculating the cross spectrum of the first signal and the second signal based on the first Fourier spectrum and the second Fourier spectrum; calculating the full complex plane mean ratio and the half complex plane distribution ratio based on the cross spectrum; determining a target measurement value based on the full complex plane mean ratio and the half complex plane distribution ratio, so as to determine the degree of phase synchronization between the first signal and the second signal based on the target measurement value. The method can comprehensively consider the full complex plane mean ratio and the half complex plane distribution ratio based on the imaginary part of the cross spectrum, thereby more accurately detecting the degree of phase synchronization between the signals. At the same time, different calculation methods can be matched according to different polarity types of the imaginary part of the cross spectrum to improve the efficiency of phase synchronization detection between signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate some embodiments of the present application or technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0054] Figure 1 A schematic flow chart of a method for detecting phase synchronization between signals provided in some embodiments of the present application;

[0055] Figure 2 A schematic diagram of a process for calculating the full complex plane mean ratio based on the cross spectrum provided in some embodiments of the present application;

[0056] Figure 3 A schematic diagram of a process for calculating a half-complex plane distribution ratio based on a cross spectrum provided in some embodiments of the present application;

[0057] Figure 4 A schematic diagram of the simulation effect of symmetrical distribution of simulated cross-spectrum along the real axis provided in some embodiments of the present application;

[0058] Figure 5 This is a diagram showing the difference between the weighted phase lag index and the target measurement value phase synchronization analysis results under the alpha rhythm of the spatial memory task provided by some embodiments of the present application;

[0059] Figure 6 A schematic diagram of the structure of a detection system for phase synchronization between signals provided in some embodiments of the present application. DETAILED DESCRIPTION

[0060] To make the objectives, technical solutions, and advantages of some embodiments of the present application more clear, the following will clearly and completely describe the technical solutions of some embodiments of the present application in conjunction with the specific embodiments of the present application and the corresponding drawings. Obviously, the described embodiments are only some of the embodiments of the present application, not all of the embodiments.

[0061] It should be noted that the brief descriptions of terms in some embodiments of the present application are only for the purpose of facilitating understanding of the embodiments described below, and are not intended to limit the embodiments of some embodiments of the present application. Unless otherwise specified, these terms should be understood according to their ordinary and usual meanings.

[0062] For a signal, energy determines the amplitude of the signal, and the phase of the frequency component and other related components determines the shape of the signal. In some embodiments, the phase of the frequency component and other related components is related to the signal generation process, and the shape of the signal is related to the signal encoding, and the signal encoding can be found through phase analysis methods. Therefore, when analyzing the shape of the signal, it is necessary to analyze the phase of the signal, that is, it is necessary to perform phase analysis. For example, in the field of neural signal analysis, phase analysis methods such as phase synchronization are important communication mechanisms between neurons, and the shape of neural signals can be analyzed through phase analysis methods such as phase synchronization.

[0063] In the process of performing phase analysis on a signal, a phase synchronization analysis method can be used. In some embodiments, the phase synchronization analysis method refers to examining the stability or distribution concentration of the phase difference between one signal segment and another signal segment. Exemplarily, the examination can be conducted in the time domain or in the frequency domain. If a phase synchronization analysis is performed on a signal in the time domain, the signal type is required to be a narrowband signal. If a phase synchronization analysis is performed on a signal in the frequency domain, there is no restriction on the signal type. Therefore, in order to not be restricted by the signal type, a phase synchronization analysis can be performed on the signal in the frequency domain.

[0064] The weighted phase lag index WPLI is a frequency domain phase synchronization parameter. Therefore, when performing phase synchronization analysis on a signal in the frequency domain, the weighted phase lag index WPLI can be used for measurement. In some embodiments, when performing phase synchronization analysis on a signal, the imaginary part of the cross spectrum can be calculated, that is, by analyzing the polarity of the imaginary part of the cross spectrum between two signals, the phase synchronization between the signals can be measured. In combination with the weighted phase lag index WPLI, the weighted phase lag index WPLI can be used to statistically calculate the sign distribution of the imaginary part of the cross spectrum, and the absolute value of the imaginary part of the cross spectrum is used for weighting. The value range of the weighted result is 0-1. The closer the result is to 0, the weaker the synchronization between the two signals. The closer the result is to 1, the stronger the phase synchronization between the two signals.

[0065] Although the above method can analyze the phase synchronization relationship between signals, the analysis method of the weighted phase lag index WPLI is limited to the case where the imaginary part of the cross spectrum is concentrated in positive or concentrated in negative, that is, it is limited to the case of a single dominant polarity, such as a single dominant polarity that is only positive or only negative. Therefore, when the imaginary part of the cross spectrum is not the single dominant polarity mentioned above, for example, when the imaginary part of the cross spectrum has both positive and negative phases, and the two phases are symmetrically distributed about the real axis, according to the calculation method of the weighted phase lag index WPLI, due to the cancellation of the symmetrical positive and negative polarities, the phase synchronization correlation calculated by this method is 0, that is, a result of completely non-phase lock will be obtained. Among them, phase lock is the abbreviation of phase lock, which means the phase synchronization between two signals.

[0066] In fact, if the two dominant phases are concentrated at a position far away from the real axis, there is phase locking, that is, the actual correlation should be greater than 0. Therefore, there are errors when using the weighted phase lag index WPLI to analyze the phase synchronization between signals, resulting in low accuracy.

[0067] To address the problem of low accuracy in phase synchronization analysis between signals, the present application provides a method for detecting phase synchronization between signals. The method combines two parameters based on the imaginary part of the cross spectrum to comprehensively judge and measure the phase synchronization between signals. This method can be applied to the analysis of the limited synchronization characteristics of multi-channel signals, more accurately reflecting the phase synchronization between two signal segments. This compensates for the fact that the weighted phase lag index (WPLI) method is limited to a single dominant polarity, as well as for the case where the phase synchronization result is incorrectly calculated when the imaginary part of the cross spectrum has a symmetrical distribution of signals.

[0068] In order to facilitate the understanding of the technical solutions in some embodiments of the present application, each step is described in detail below in conjunction with some specific embodiments and drawings. Figure 1 A flow chart of a method for detecting phase synchronization between signals provided in some embodiments of the present application is shown in FIG. Figure 1 As shown, the method may include the following steps:

[0069] Step S1: Acquire a first signal and a second signal.

[0070] In order to distinguish the signals, the two signals may be recorded as a first signal and a second signal. For example, the two signals may be marked as S1 and S2. After step S1 is completed, step S2 may be executed.

[0071] Step S2: performing a discrete Fourier transform on the first signal to obtain a first Fourier spectrum, and performing a discrete Fourier transform on the second signal to obtain a second Fourier spectrum.

[0072] In some embodiments, a discrete Fourier transform (DFT) transforms signals from the time domain to the frequency domain, thereby studying the signal's spectral structure and variation patterns. A DFT is performed on the first signal S1 to obtain a first Fourier spectrum Z1(f), and a DFT is performed on the second signal S2 to obtain a second Fourier spectrum Z2(f), where f is the spectrum generated by performing DFTs on the first and second signals. After step S2 is completed, step S3 can be executed.

[0073] Step S3: Calculating a cross spectrum of the first signal and the second signal according to the first Fourier spectrum and the second Fourier spectrum.

[0074] In some embodiments, the cross spectrum of the first signal and the second signal can be calculated in the following manner: first, the first Fourier spectrum and the second Fourier spectrum are obtained, then, the complex conjugate of the second Fourier spectrum is calculated based on the second Fourier spectrum, and finally, a product operation is performed on the first Fourier spectrum and the complex conjugate to obtain the cross spectrum of the first signal and the second signal.

[0075] Exemplarily, the cross spectrum of the first signal and the second signal may be denoted as X(f), and the cross spectrum of the first signal and the second signal may be calculated according to the first Fourier spectrum and the second Fourier spectrum according to the following formula:

[0076] X(f)=Z1(f)Z2 * (f);

[0077] Among them, the calculation process of discrete Fourier transform is equivalent to the signal changing from time domain to frequency domain, and the signal becomes a frequency point sequence after discrete Fourier transform. Therefore, f is the spectrum generated by the discrete Fourier transform of the first signal and the second signal, X(f) is the cross spectrum of the first signal and the second signal, Z1(f) is the first Fourier spectrum; Z2 * (f) is the complex conjugate of the second Fourier spectrum, i.e., Z2 * represents the complex conjugate of Z2. In some embodiments, the imaginary part of the cross spectrum, that is, the distance between a point on the cross spectrum and the real axis, reflects the degree of phase advance or lag. After step S3 is completed, the following step S4 may be executed.

[0078] Step S4: Calculate the full complex plane mean ratio and the half complex plane distribution ratio according to the cross spectrum.

[0079] In some embodiments, the full complex in the full complex plane mean ratio can be understood as the case where the imaginary parts of the cross spectrum are all positive or all negative, and the half complex in the half complex plane distribution ratio can be understood as the case where the positive and negative imaginary parts of the cross spectrum are symmetrically distributed. Since the algorithm of the full complex plane mean ratio is more sensitive to a single polarity, and the algorithm of the half complex plane distribution ratio is more sensitive to the polarity of symmetrical distribution, in order to improve the accuracy of phase synchronization between signals, the present application takes both the full complex plane mean ratio and the half complex plane distribution ratio into consideration, and in the actual judgment process, comprehensively judges and measures the phase synchronization between signals.

[0080] Figure 2 A schematic diagram of a process for calculating the full complex plane mean ratio based on the cross spectrum provided in some embodiments of the present application, such as Figure 2 As shown, in some embodiments, when calculating the full complex plane mean ratio, the imaginary part of the cross spectrum can be first obtained according to the cross spectrum, and then the average value of the imaginary part of the cross spectrum imaginary part is calculated according to the imaginary part of the cross spectrum, and then the absolute value of the mean of the imaginary part of the cross spectrum imaginary part is calculated according to the imaginary part average value; then, the absolute value of the imaginary part of the cross spectrum imaginary part is calculated according to the cross spectrum imaginary part, and the absolute mean of the imaginary part of the cross spectrum imaginary part is calculated according to the absolute value of the imaginary part, and finally a ratio operation is performed on the absolute value of the imaginary part mean and the absolute mean of the imaginary part to obtain the full complex plane mean ratio of the imaginary part of the cross spectrum.

[0081] Exemplarily, a ratio operation is performed on the absolute value of the imaginary part mean and the absolute mean of the imaginary part according to the following formula:

[0082]

[0083] Where W represents the mean ratio of the entire complex plane, X represents the cross spectrum of the first and second signals, Im represents the imaginary part, Im(X) represents the imaginary part of the cross spectrum, E represents the average value, and abs represents the absolute value function. This formula shows that the mean ratio W of the entire complex plane is defined as the ratio of the absolute value of the mean of the imaginary parts of the cross spectra to the mean of the absolute values ​​of the imaginary parts of the cross spectra.

[0084] Figure 3 A schematic diagram of a process for calculating the half-complex plane distribution ratio based on the cross spectrum provided in some embodiments of the present application, such as Figure 3 As shown, in some embodiments, when calculating the half-complex plane distribution ratio, the cross-spectrum imaginary part can first be obtained based on the cross-spectrum, and the absolute value of the imaginary part of the cross-spectrum imaginary part can be calculated based on the cross-spectrum imaginary part. Then, the median function of the imaginary part of the cross-spectrum can be calculated based on the absolute value of the imaginary part, and the probability percentile of the imaginary part of the cross-spectrum can be obtained. Finally, a ratio operation is performed on the median function and the probability percentile to obtain the half-complex plane distribution ratio.

[0085] Exemplarily, a ratio operation is performed on the median function and the probability percentile according to the following formula:

[0086]

[0087] Wherein, L represents half-complex plane distribution ratio, X represents the cross spectrum of the first signal and the second signal, Im represents the imaginary part, Im(X) represents the imaginary part of the cross spectrum, abs represents the absolute value function, median is the median function, represents the median calculation, ratio represents the probability of the cross spectrum imaginary part, percentile represents the percentile of the calculated probability, that is, percentile represents the percentile of the probability ratio of the cross spectrum imaginary part. In some embodiments, probability ratio can be selected to be equal to 90 or 100, which is the maximum value of the cross spectrum imaginary part when equal to 100. It can be seen from the above formula that the definition of half-complex plane distribution ratio is the ratio of the median of the absolute value of the cross spectrum imaginary part to the maximum value of the cross spectrum imaginary part. After step S4 is executed, the following step S5 can be performed.

[0088] Step S5: determining a target metric value according to the full complex plane mean ratio and the half complex plane distribution ratio, so as to determine the phase synchronization degree between the first signal and the second signal according to the target metric value.

[0089] After the full complex plane mean ratio and the half complex plane distribution ratio are calculated, the target measurement value can be determined based on the full complex plane mean ratio and the half complex plane distribution ratio. Finally, the phase synchronization degree between the first signal and the second signal can be determined based on the target measurement value to improve the accuracy of phase synchronization detection.

[0090] In some embodiments, the full complex plane mean ratio and the half complex plane distribution ratio are comprehensively considered, and a final target metric value can be determined by comparing the full complex plane mean ratio and the half complex plane distribution ratio. If the full complex plane mean ratio is greater than the half complex plane distribution ratio, the full complex plane mean ratio is used as the target metric value; and if the full complex plane mean ratio is less than the half complex plane distribution ratio, the half complex plane distribution ratio is used as the target metric value.

[0091] Exemplarily, the target measurement value can be recorded as S, W is the full complex plane mean ratio, and L is the half complex plane distribution ratio. The target measurement value S can be calculated using the formula S=max(W, L). Wherein, max represents the maximum value, and S is the maximum value of the full complex plane mean ratio W and the half complex plane distribution ratio L. The value of the target measurement value S is 0-1. In some embodiments, the value of S represents the degree of phase locking between the two signals, that is, the degree of correlation of phase synchronization. The larger the value of S, the stronger the correlation of phase synchronization, that is, the stronger the phase locking degree. The smaller the value of S, the weaker the correlation of phase synchronization, that is, the weaker the phase locking degree. When S=1, it means that the two signals are completely phase-locked, and when S=0, it means complete loss of lock.

[0092] In order to improve the efficiency of phase synchronization detection between signals, in some embodiments, the polarity type of the imaginary part of the cross spectrum can be identified. Exemplarily, the polarity type can include single polarity and symmetrical polarity. Single polarity is a polarity that is purely positive or purely negative. This is because the two algorithms, the full complex plane mean ratio and the half complex plane distribution ratio, have different sensitivities to different polarities. That is, the full complex plane mean ratio algorithm is more sensitive to single polarity, and the half complex plane distribution ratio algorithm is more sensitive to symmetrically distributed polarity. Therefore, the polarity type can be identified to match the appropriate algorithm to improve the detection efficiency of phase synchronization between signals. Exemplarily, if the polarity type is single polarity, the degree of phase synchronization between the first signal and the second signal can be detected based on the full complex plane mean ratio, and if the polarity type is symmetrical polarity, the degree of phase synchronization between the first signal and the second signal can be detected based on the half complex plane distribution ratio.

[0093] It can be seen from the above technical solution that the above embodiment provides a method for detecting phase synchronization between signals, including obtaining a first signal and a second signal; performing a discrete Fourier transform on the first signal to obtain a first Fourier spectrum, and performing a discrete Fourier transform on the second signal to obtain a second Fourier spectrum; calculating the cross spectrum of the first signal and the second signal based on the first Fourier spectrum and the second Fourier spectrum; calculating the full complex plane mean ratio and the half complex plane distribution ratio based on the cross spectrum; determining the target measurement value based on the full complex plane mean ratio and the half complex plane distribution ratio, so as to determine the degree of phase synchronization between the first signal and the second signal based on the target measurement value. The method can comprehensively consider the full complex plane mean ratio and the half complex plane distribution ratio based on the imaginary part of the cross spectrum, and thus more accurately detect the degree of phase synchronization between the signals. At the same time, different calculation methods can be matched according to different polarity types of the imaginary part of the cross spectrum to improve the efficiency of phase synchronization detection between signals.

[0094] In order to further verify the technical effect achieved by the above-mentioned phase synchronization detection method, in some embodiments, the following simulation experiment may be performed. Figure 4 This is a schematic diagram of the simulation effect of the simulated cross spectrum symmetrically distributed along the real axis provided in some embodiments of the present application, such as Figure 4 As shown, the experiment simulates the situation where the imaginary part of the cross spectrum is concentrated at a position far away from the real axis and is symmetric about the real axis. The values ​​of the weighted phase lag index WPLI and the target measurement value S in this situation are calculated and compared. Figure 4The figure shows the distribution histogram of the imaginary part of the cross-spectrum from the simulation experiment, as well as the calculation results of the weighted phase lag index (WPLI) and the target metric value (S). The calculated value of the weighted phase lag index (WPLI) approaches 0, indicating that the two signals have almost lost phase synchronization when the cross-spectrum is symmetrically distributed along the real axis. In reality, phase synchronization is present in this symmetrically distributed cross-spectrum, and the target metric value (S) is 0.77. Therefore, the target metric value (S) provides a more accurate measure of phase synchronization.

[0095] In order to more intuitively present the difference between the calculation of the weighted phase lag index WPLI and the target measurement value S, in some embodiments, the following simulation experiment can be performed. In some embodiments, taking the brain wave signal under a spatial memory task as an example, the collected brain wave signal is segmented according to the trial length and rhythm, and the signal of each segment on N electrodes can be obtained. Among them, N is a positive integer, and the specific value is related to the relevant equipment of the experiment and is not limited to it. A trial is the smallest unit for measurement and recording in an experiment. Depending on the experimental method, the time span of each trial and the total number of trials may be different. For example, N can be 32, so that the signal s(k) of each segment on 32 electrodes can be obtained, where K is the number of electrodes. It can be understood that when N is 32, 1≤K≤32.

[0096] In some embodiments, the signals of any two electrode pairs can be set as s(i) and s(j), and the discrete Fourier transforms of these two signals can be calculated, which are Z i (f) and Z j (f), then the cross spectrum between them is in Z j After obtaining the cross spectrum X(f), for all 32×32 electrode pairs, the target metric values ​​are calculated according to the target metric value determination method, and a 32×32 adjacency matrix can be obtained.

[0097] After calculating the adjacency matrix for all subjects, two sets of experimental data can be provided and compared for differences between the weighted phase lag index (WPLI) and the target measure (S). For example, when the alpha rhythm range of a spatial memory task is 8 Hz to 13 Hz, two sets of experimental data can be provided: experimental group T and control group C. Phase synchronization analysis is performed on these two sets of data using the weighted phase lag index (WPLI) and the target measure (S), respectively, to identify electrode pairs with significant differences in phase synchronization between experimental group T and control group C.

[0098] Figure 5This is a diagram showing the difference between the weighted phase lag index and the target measurement value phase synchronization analysis results under the alpha rhythm of the spatial memory task provided by some embodiments of the present application, such as Figure 5 As shown, Figure 5 The figure shows the distribution of electrode pairs with significantly different phase synchronization programs detected by the target measurement value detection method compared with the weighted phase lag index detection method. The dotted line represents the significant difference in phase synchronization between the two electrodes in the experimental group T and the control group C.

[0099] Through the above comparison, it can be seen that when detecting the degree of phase synchronization between signals, the target measurement value detection method can detect more phase synchronization degrees, that is, detect more phase lock situations, compared with the weighted phase lag index detection method. Therefore, the phase synchronization detection method in the embodiment of the present application combines two parameters based on the imaginary part of the cross spectrum to comprehensively judge and measure the phase synchronization between signals, more accurately reflecting the phase synchronization between two signal segments, thereby compensating for the situation in which the weighted phase lag index WPLI method is limited to a single dominant polarity, and the situation in which the phase synchronization result is calculated incorrectly when the imaginary part of the cross spectrum has a symmetrical distribution of signals.

[0100] Some embodiments of the present application also provide a detection system for phase synchronization between signals. Figure 6 A schematic diagram of a detection system structure for phase synchronization between signals provided in some embodiments of the present application, such as Figure 6 As shown, in some embodiments, the detection system may include the following:

[0101] Signal acquisition module 100: acquires a first signal and a second signal;

[0102] Fourier transform module 200: performs discrete Fourier transform on the first signal to obtain a first Fourier spectrum, and performs discrete Fourier transform on the second signal to obtain a second Fourier spectrum;

[0103] Cross spectrum calculation module 300: calculates the cross spectrum of the first signal and the second signal according to the first Fourier spectrum and the second Fourier spectrum;

[0104] Ratio calculation module 400: calculates the full complex plane mean ratio and the half complex plane distribution ratio according to the cross spectrum;

[0105] The target detection module 500 determines a target metric value according to the full complex plane mean ratio and the half complex plane distribution ratio, so as to determine the phase synchronization degree between the first signal and the second signal according to the target metric value.

[0106] As can be seen from the above technical solutions, the above embodiments provide a system for detecting phase synchronization between signals. This system can comprehensively consider the full complex plane mean ratio and half complex plane distribution ratio based on the imaginary part of the cross spectrum, thereby more accurately detecting the degree of phase synchronization between signals. Furthermore, different calculation methods can be matched to different polarity types of the imaginary part of the cross spectrum, thereby improving the efficiency of phase synchronization detection between signals.

[0107] The same and similar parts between the various embodiments in this specification can be referenced to each other and will not be repeated here.

[0108] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein.

[0109] It should be understood that the present invention is not limited to the exact construction described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for detecting phase synchronization between signals, characterized in that: include: Acquire a first signal and a second signal; Performing a discrete Fourier transform on the first signal to obtain a first Fourier spectrum, and performing a discrete Fourier transform on the second signal to obtain a second Fourier spectrum; Calculating a cross spectrum of the first signal and the second signal according to the first Fourier spectrum and the second Fourier spectrum; Calculating a full complex plane mean ratio and a half complex plane distribution ratio according to the cross spectrum; determining a target metric value according to the full complex plane mean ratio and the half complex plane distribution ratio, so as to determine a degree of phase synchronization between the first signal and the second signal according to the target metric value; The full complex plane mean ratio is obtained by performing a ratio operation on the absolute value of the mean of the imaginary part of the cross-spectrum imaginary part and the absolute mean of the imaginary part of the cross-spectrum imaginary part according to the following formula: ； Wherein, W represents the full complex plane mean ratio, X represents the cross spectrum of the first signal and the second signal, represents the imaginary part of the cross spectrum, E represents the average value, and abs represents the absolute value function; The half-complex plane distribution ratio is obtained by performing a ratio operation on the median function of the imaginary part of the cross spectrum and the probability percentile of the imaginary part of the cross spectrum according to the following formula: ； Wherein, L represents the half complex plane distribution ratio, X represents the cross spectrum of the first signal and the second signal, Indicates finding the imaginary part of the cross spectrum, abs indicates taking the absolute value function, median indicates calculating the median, ratio indicates the probability of the imaginary part of the cross spectrum, and percentile indicates calculating the percentile of the probability.

2. The method for detecting phase synchronization between signals according to claim 1, characterized in that: The step of calculating a cross spectrum of the first signal and the second signal according to the first Fourier spectrum and the second Fourier spectrum includes: Acquire the first Fourier spectrum and the second Fourier spectrum; calculating a complex conjugate of the second Fourier spectrum according to the second Fourier spectrum; A product operation is performed on the first Fourier spectrum and the complex conjugate to obtain a cross spectrum of the first signal and the second signal.

3. The method for detecting phase synchronization between signals according to claim 2, wherein: The cross spectrum of the first signal and the second signal is calculated according to the first Fourier spectrum and the second Fourier spectrum according to the following formula: ； Wherein, f is a frequency spectrum generated by performing discrete Fourier transform on the first signal and the second signal; is a cross spectrum of the first signal and the second signal; is the first Fourier spectrum; is the complex conjugate of the second Fourier spectrum.

4. The method for detecting phase synchronization between signals according to claim 1, wherein: The step of calculating the full complex plane mean ratio according to the cross spectrum includes: Obtaining a cross-spectrum imaginary part according to the cross-spectrum; Calculating an average value of the imaginary part of the cross spectrum imaginary part according to the cross spectrum imaginary part; Calculate the imaginary part mean absolute value of the imaginary part of the cross spectrum according to the imaginary part average value; Calculating the absolute value of the imaginary part of the cross spectrum imaginary part according to the cross spectrum imaginary part; Calculating the absolute mean of the imaginary parts of the cross-spectrum imaginary parts according to the absolute values ​​of the imaginary parts; A ratio operation is performed on the absolute value of the imaginary part mean and the absolute mean of the imaginary part to obtain a full complex plane mean ratio of the imaginary part of the cross spectrum.

5. The method for detecting phase synchronization between signals according to claim 1, wherein: The step of calculating the half-complex plane distribution ratio according to the cross spectrum comprises: Obtaining a cross-spectrum imaginary part according to the cross-spectrum; Calculating the absolute value of the imaginary part of the cross spectrum imaginary part according to the cross spectrum imaginary part; Calculating the median function of the imaginary part of the cross spectrum according to the absolute value of the imaginary part; Obtaining the probability percentile of the imaginary part of the cross spectrum; A ratio operation is performed on the median function and the probability percentile to obtain a half-complex plane distribution ratio.

6. The method for detecting phase synchronization between signals according to claim 1, wherein: The step of determining a target measurement value according to the full complex plane mean ratio and the half complex plane distribution ratio comprises: comparing the full complex plane mean ratio and the half complex plane distribution ratio; If the full complex plane mean ratio is greater than the half complex plane distribution ratio, taking the full complex plane mean ratio as a target measurement value; If the full complex plane mean ratio is smaller than the half complex plane distribution ratio, the half complex plane distribution ratio is used as a target metric value.

7. The method for detecting phase synchronization between signals according to claim 1, wherein: Also includes: Identifying a polarity type of the imaginary part of the cross spectrum, wherein the polarity type includes single polarity and symmetrical polarity; If the polarity type is the single polarity, detecting a degree of phase synchronization between the first signal and the second signal based on the full complex plane mean ratio; If the polarity type is the symmetrical polarity, the degree of phase synchronization between the first signal and the second signal is detected based on the half-complex plane distribution ratio.

8. A detection system for phase synchronization between signals, characterized in that: include: Signal acquisition module: acquires the first signal and the second signal; Fourier transform module; Performing a discrete Fourier transform on the first signal to obtain a first Fourier spectrum, and performing a discrete Fourier transform on the second signal to obtain a second Fourier spectrum; A cross spectrum calculation module is configured to calculate a cross spectrum of the first signal and the second signal according to the first Fourier spectrum and the second Fourier spectrum; Ratio calculation module: calculates the full complex plane mean ratio and the half complex plane distribution ratio according to the cross spectrum; A target detection module is configured to determine a target measurement value according to the full complex plane mean ratio and the half complex plane distribution ratio, so as to determine a phase synchronization degree between the first signal and the second signal according to the target measurement value; The full complex plane mean ratio is obtained by performing a ratio operation on the absolute value of the mean of the imaginary part of the cross-spectrum imaginary part and the absolute mean of the imaginary part of the cross-spectrum imaginary part according to the following formula: ； Wherein, W represents the full complex plane mean ratio, X represents the cross spectrum of the first signal and the second signal, represents the imaginary part of the cross spectrum, E represents the average value, and abs represents the absolute value function; The half-complex plane distribution ratio is obtained by performing a ratio operation on the median function of the imaginary part of the cross spectrum and the probability percentile of the imaginary part of the cross spectrum according to the following formula: ； Wherein, L represents the half complex plane distribution ratio, X represents the cross spectrum of the first signal and the second signal, Indicates finding the imaginary part of the cross spectrum, abs indicates taking the absolute value function, median indicates calculating the median, ratio indicates the probability of the imaginary part of the cross spectrum, and percentile indicates calculating the percentile of the probability.

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