Wireless signal modulation identification method and device and wireless signal blind demodulation system

Abstract

The invention belongs to the technical field of signal processing, and provides a wireless signal modulation identification method and device and a wireless signal blind demodulation system, and the method comprises the steps: extracting a target feature from a wireless signal, the target feature being at least one of a time domain feature, a frequency domain feature and a time-frequency domain feature; obtaining a signal type of the wireless signal based on the target feature, and determining at least one candidate modulation mode according to the signal type; for each candidate modulation mode, performing blind modulation on the wireless signal by adopting the candidate modulation mode and calculating an error vector magnitude (EVM) to obtain a plurality of EVM values; and screening a target EVM value from the plurality of EVM values by adopting a synchronization point optimization strategy to obtain a target modulation mode so as to demodulate the wireless signal. According to the method, the multi-dimensional features of the wireless signals are fused, and the error vector amplitude is combined to assist judgment, so that the recognition robustness and accuracy under the condition of low signal-to-noise ratio are enhanced.

Description

Technical Field

[0001] The present invention relates to the field of signal processing technology, and in particular to a modulation identification method and device for wireless signals and a wireless signal blind demodulation system. Background Art

[0002] With the rapid development of modern communication technology, wireless communication systems are widely used in military, civil and industrial control and other fields. Since the modulation method directly determines the transmission characteristics of the signal, the accurate identification and blind demodulation of the modulation method of unknown signals has become an important research topic in the fields of wireless signal monitoring, spectrum regulation and non-cooperative communication.

[0003] In practical applications, the modulation methods of wireless signals include linear modulation (such as AM, FM), nonlinear modulation (such as PSK, QAM) and composite modulation (such as MSK+AM, 2FSK+FM). With the development of high-order modulation technology, the spectrum utilization of signals has been significantly improved, but it also brings higher challenges to the identification and demodulation of modulation methods in low signal-to-noise ratio, complex interference and unknown environments.

[0004] In related technologies, wireless signals are mainly modulated through linear modulation, and the blind demodulation capability of composite modulated signals containing multiple modulation components is limited, resulting in reduced accuracy of signal blind demodulation recognition in complex channels or low signal-to-noise ratio environments, and is unable to meet the diverse needs of modern wireless communications for complex signal processing. Summary of the invention

[0005] The present invention provides a modulation identification method and device for wireless signals and a wireless signal blind demodulation system, which are used to solve the defect in the prior art that the blind demodulation capability of a composite modulation signal containing multiple modulation components is limited, resulting in low accuracy of blind demodulation identification of signals in complex channels or low signal-to-noise ratio environments, thereby improving the accuracy and robustness of blind demodulation identification of signals.

[0006] The present invention provides a modulation identification method for a wireless signal, comprising: Extracting a target feature from the wireless signal, wherein the target feature is at least one of a time domain feature, a frequency domain feature, and a time-frequency domain feature; Acquire a signal type of the wireless signal based on the target feature, and determine at least one candidate modulation mode according to the signal type; For each of the candidate modulation modes, blindly modulate the wireless signal using the candidate modulation mode and calculate the error vector magnitude (EVM) to obtain multiple EVM values; A synchronization point optimization strategy is adopted to screen out a target EVM value from the multiple EVM values, and a target modulation mode is obtained to achieve demodulation of the wireless signal.

[0007] According to a modulation identification method for wireless signals provided by the present invention, the target features are time domain features, frequency domain features and time-frequency domain features; wherein the time domain features include the flatness of the signal envelope of the wireless signal; the frequency domain features include the number of peaks and the flatness of the spectrum of the power spectrum of the wireless signal; the time-frequency domain features include the flatness of the instantaneous frequency of the wireless signal; The acquiring the signal type of the wireless signal based on the target feature comprises: When the number of peaks of the power spectrum of different powers of the wireless signal is 1 and the spectrum flatness of different powers is greater than a first threshold, determining that the signal type of the wireless signal includes a constant envelope signal; When the flatness of the signal envelope of the wireless signal is greater than the second threshold, and the flatness of the instantaneous frequency is greater than the third threshold, confirming that the signal type of the wireless signal includes an amplitude modulation signal; When the number of peaks of the 1st power power spectrum of the wireless signal is 0, the 1st power spectrum flatness is less than or equal to the first threshold, the number of peaks of the 4th power spectrum is 1, the 4th power spectrum flatness is greater than the first threshold, the instantaneous frequency flatness is less than or equal to the fourth threshold, and the flatness of the signal envelope is less than the fifth threshold, it is confirmed that the signal type of the wireless signal includes a quaternary offset quadrature phase shift keying signal 4OQPSK signal.

[0008] According to a modulation identification method for wireless signals provided by the present invention, the target features are time domain features and frequency domain features; wherein the time domain features include the modulation depth of the signal envelope of the wireless signal; the frequency domain features include the number of peaks and the spectrum flatness of the power spectrum of the wireless signal; The acquiring the signal type of the wireless signal based on the target feature further comprises: When the number of peaks of the first-power power spectrum of the wireless signal is 2 and the spectrum flatness satisfies a sixth threshold, confirming that the signal type of the wireless signal includes a binary frequency shift keying 2FSK signal and an amplitude modulation AM signal; When the number of peaks of the square power spectrum of the wireless signal is 2 and the square spectrum flatness meets the sixth threshold, confirming that the signal type of the wireless signal includes a binary minimum shift keying 2MSK signal and an AM signal; When the modulation depth is greater than the seventh threshold, the signal type of the wireless signal includes an AM signal; when the modulation depth is less than or equal to the seventh threshold, the signal type of the wireless signal includes a continuous wave CW signal; When the number of peaks of the first-power power spectrum of the wireless signal is 2 and the first-power spectrum flatness satisfies the sixth threshold, it is determined that the signal type of the wireless signal includes a 2FSK signal.

[0009] According to a modulation identification method for wireless signals provided by the present invention, the target features are frequency domain features and time-frequency domain features; wherein the frequency domain features include the number of peaks and the spectrum flatness of the power spectrum of the wireless signal; the time-frequency domain features include the instantaneous frequency flatness of the wireless signal; The acquiring the signal type of the wireless signal based on the target feature further comprises: When the number of peaks of the first-power power spectrum of the wireless signal is 0, the first-power spectrum flatness is less than or equal to the first threshold, and the number of peaks of the second-power power spectrum is 2, and the second-power spectrum flatness meets the eighth threshold, confirming that the signal type of the wireless signal includes a 2MSK or a binary Gaussian minimum shift keying 2GMSK signal; When the number of peaks of the first-power power spectrum of the wireless signal is 0, the first-power spectrum flatness is less than or equal to the first threshold, the number of peaks of the second-power power spectrum is 1 or 3, the second-power spectrum flatness is greater than the first threshold, and the instantaneous frequency flatness is greater than the third threshold, it is confirmed that the signal type of the wireless signal includes a binary phase shift keying 2PSK signal.

[0010] According to a modulation identification method for wireless signals provided by the present invention, the target feature is a frequency domain feature; wherein the frequency domain feature includes the number of peaks and the degree of spectrum flatness of the power spectrum of the wireless signal; The acquiring the signal type of the wireless signal based on the target feature further comprises: When the number of peaks of the 1st power spectrum of the wireless signal is 0, the number of peaks of the 4th power spectrum is 1 or 3, and the number of peaks of the 2nd power spectrum is 1, confirming that the signal type of the wireless signal includes an octal quadrature amplitude modulation 8QAM signal; When the number of peaks of the 1st power spectrum of the wireless signal is 0, the number of peaks of the 4th power spectrum is 1 or 3, and the number of peaks of the 2nd power spectrum is not 1, confirming that the signal type of the wireless signal includes a quaternary phase shift keying 4PSK or 8QAM signal; When the number of peaks of the 1st power spectrum and the 2nd power spectrum of the wireless signal is 0, and the number of peaks of the 4th power spectrum is 1 or 3, confirming that the signal type of the wireless signal includes a 16 / 32 / 64QAM signal; When the number of peaks of the 1st, 2nd, 4th and 8th power spectrums of the wireless signal is 0 and the number of peaks of the 16th power spectrum is 1, confirming that the signal type of the wireless signal includes a hexadecimal amplitude phase modulation 16APSK signal; When the number of peaks of the 1st power spectrum of the wireless signal is 0, the 1st power spectrum flatness is less than or equal to the first threshold, the number of peaks of the 4th power spectrum is 1, the 4th power spectrum flatness is greater than the first threshold, and the number of peaks of the 2nd power spectrum is 2, and the 2nd power spectrum flatness is less than or equal to the ninth threshold, it is confirmed that the signal type of the wireless signal includes a 4OQPSK signal.

[0011] According to a modulation identification method for wireless signals provided by the present invention, the target feature also includes a time domain feature; the time domain feature includes the flatness of the signal envelope of the wireless signal; The acquiring the signal type of the wireless signal based on the target feature further comprises: When the flatness of the signal envelope is less than or equal to a tenth threshold and the wireless signal can be demodulated by a frequency modulation FM signal, confirming that the signal type of the wireless signal includes a 2FSK or MSK modulated signal; When the flatness of the signal envelope is less than or equal to the tenth threshold, the wireless signal cannot be FM demodulated, and the ratio of the sampling rate to the bit rate of the wireless signal is not an integer, it is confirmed that the signal type of the wireless signal includes an FM signal.

[0012] According to a modulation identification method for wireless signals provided by the present invention, the target features are frequency domain features and time-frequency domain features; wherein the frequency domain features include the number of peaks and spectrum flatness of the power spectrum of the wireless signal; and the time-frequency domain features include the instantaneous frequency flatness of the wireless signal; The acquiring the signal type of the wireless signal based on the target feature further comprises: When the number of peaks of the 1st power spectrum and the 2nd power spectrum of the wireless signal is 0, the number of peaks of the 4th power spectrum is 2 or 4, the 1st power spectrum flatness satisfies the sixth threshold, and the instantaneous frequency flatness is greater than the eleventh threshold, it is confirmed that the signal type of the wireless signal includes a π / 4QPSK signal; When the number of peaks of the 1st power spectrum of the wireless signal is 0, the number of peaks of the 2nd power spectrum is 1, the number of peaks of the 4th power spectrum is 1 or 2, and the 1st power spectrum flatness is less than the ninth threshold, the 2nd power spectrum flatness and the 4th power spectrum flatness are greater than the first threshold, and the instantaneous frequency flatness is greater than the eleventh threshold, it is confirmed that the signal type of the wireless signal includes a 4π differential quadrature phase shift keying 4π / DQPSK signal; When the number of peaks of the 1st power spectrum, the number of peaks of the 2nd power spectrum and the number of peaks of the 4th power spectrum of the wireless signal are 0, and the instantaneous frequency flatness is greater than the eleventh threshold, it is confirmed that the signal type of the wireless signal includes an 8PSK signal.

[0013] The present invention also provides a modulation identification device for a wireless signal, comprising: A feature extraction module, used to extract a target feature from the wireless signal, wherein the target feature is at least one of a time domain feature, a frequency domain feature, and a time-frequency domain feature; A modulation identification module, which obtains a signal type of the wireless signal based on the target feature, and determines at least one candidate modulation mode according to the signal type; A calculation module, configured to, for each of the candidate modulation modes, use the candidate modulation mode to blindly modulate the wireless signal and calculate the error vector magnitude (EVM) to obtain a plurality of EVM values; The screening module is used to screen out a target EVM value from the multiple EVM values ​​by adopting a synchronization point optimization strategy to obtain a target modulation mode so as to realize demodulation of the wireless signal.

[0014] The present invention also provides a wireless signal blind demodulation system, comprising: A signal receiving module, the signal receiving module is used for the wireless signal; Modulation identification device of the wireless signal; A demodulation module, the demodulation module is used to demodulate the wireless signal according to the target modulation mode output by the modulation identification device of the wireless signal to obtain a demodulation result; wherein the demodulation result includes at least one of the demodulated symbol stream, the modulation mode index, and the EVM value.

[0015] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the modulation identification method of the wireless signal as described in any one of the above is implemented.

[0016] The present invention also provides a non-transitory computer-readable storage medium on which a computer program is stored. When the computer program is executed by a processor, the modulation identification method of the wireless signal as described in any one of the above is implemented.

[0017] The present invention also provides a computer program product, comprising a computer program, wherein when the computer program is executed by a processor, the modulation identification method of the wireless signal as described in any one of the above is implemented.

[0018] The modulation identification method and device of wireless signals and the blind demodulation system of wireless signals provided by the present invention extract target features from wireless signals to obtain the signal type of wireless signals, determine candidate modulation modes according to the signal type, blindly modulate the wireless signals using the candidate modulation modes and calculate the error vector magnitude (EVM), and finally use a synchronization point optimization strategy to screen out a target EVM value from multiple EVM values ​​to obtain a target modulation mode, so as to realize demodulation of wireless signals. The multi-dimensional features of wireless signals are integrated and combined with the error vector magnitude to assist in decision making, thereby enhancing the robustness and accuracy of recognition under low signal-to-noise ratio conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 This is one of the flow charts of the modulation identification method of wireless signals provided by the present invention.

[0021] Figure 2 This is the second flow chart of the modulation identification method of wireless signals provided by the present invention.

[0022] Figure 3 It is a structural schematic diagram of the modulation identification device for wireless signals provided by the present invention.

[0023] Figure 4 It is a structural schematic diagram of the wireless signal blind demodulation system provided by the present invention.

[0024] Figure 5 It is a structural schematic diagram of the electronic device provided by the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Combine the following Figure 1-Figure 4 The present invention describes a wireless signal modulation identification method, device and wireless signal blind demodulation system.

[0027] Figure 1 It is one of the flow charts of the modulation identification method of wireless signal provided by the present invention, such as Figure 1 As shown, the method includes the following: Step 110: extract a target feature from the wireless signal, where the target feature is at least one of a time domain feature, a frequency domain feature, and a time-frequency domain feature.

[0028] In this step, the time domain features include changes in amplitude and phase, such as high-order cumulants and statistical features of instantaneous amplitude.

[0029] In some embodiments, the time domain characteristics specifically include the flatness of the wireless signal envelope, which is used to preliminarily screen the modulation mode; the flatness of the envelope of the input signal IQ data Calculated by the following formula: ; in, is the modulus value of IQ data, evlpR is the characteristic parameter of the flatness of the signal envelope, which is the mean of the square of the envelope divided by the square of the upper envelope mean. The minimum value of evlpR is 1. The smaller the value of R, the flatter the signal envelope distribution is, and the more likely it is a non-amplitude modulated signal. The larger the value of evlpR, the steeper the signal envelope distribution is, and the more likely it is an amplitude modulated signal. is the mean of the square of the envelope, is the square of the envelope mean.

[0030] In this embodiment, the frequency domain features include the number of peaks and the degree of flatness of different power spectra of the signal, which are used to further narrow the range of possible modulation modes; Specifically, the corresponding frequency domain features are calculated through the following steps: After the signal is raised to the power of p = 1, 2, 4, and 8, the linear power spectrum is obtained using FFT and then normalized based on the maximum value. The number of peaks in the normalized power spectrum is calculated, which correspond to the parameters PeakNum(1), PeakNum(2), PeakNum(3), and PeakNum(4), respectively.

[0031] In this embodiment, the time-frequency domain features include the normalized smoothness of the instantaneous frequency, which is used to determine the composite modulation signal and the complex modulation mode.

[0032] Specifically, the corresponding time-frequency domain features are calculated through the following steps: Calculate the instantaneous frequency corresponding to the IQ data ; Originally, the process of solving the instantaneous frequency involved two differential (subtracting the previous from the latter) operations, which can be simplified to one operation when applied to engineering: ; in, ;but , and there are: ; Above That is the instantaneous frequency. Normalize it by dividing it by 0.5 times the sampling rate and then taking the modulus value, we get: ; Finally, Substituting it into the previous calculation method of the smoothness, we can get the instantaneous frequency smoothness, which is recorded as .

[0033] In this embodiment, before extracting the target features, the wireless signal may be subjected to preprocessing operations including but not limited to: signal denoising (such as wavelet threshold denoising), normalization processing, and outlier removal to improve the quality of the wireless signal.

[0034] Step 120: Acquire the signal type of the wireless signal based on the target feature, and determine at least one candidate modulation mode according to the signal type.

[0035] In this step, the signal type may be determined according to one or more types of target features extracted from the wireless signal.

[0036] In this embodiment, if it is determined based on the above-mentioned target characteristics that the signal type may include one, then the corresponding modulation method can be directly selected for demodulation. However, if the signal type may include two or more, it is necessary to combine multiple candidate modulation methods to demodulate the wireless signals one by one, so as to select a modulation method with the best demodulation effect as the target modulation method.

[0037] In this embodiment, mapping to possible modulation modes according to signal type includes: (1) FSK signal, the corresponding possible modulation modes include: 2-FSK, 4-FSK, MSK (minimum shift keying), GMSK (Gaussian minimum shift keying); (2) PSK signal, corresponding possible modulation modes include: BPSK, QPSK, 8PSK, π / 4-QPSK, π / 4-DQPSK, 4OQPSK, 16APSK; (3) QAM signal, corresponding possible modulation methods include: 16QAM, 32QAM, and 64QAM.

[0038] Step 130: For each candidate modulation mode, blindly modulate the wireless signal using the candidate modulation mode and calculate the error vector magnitude (EVM) to obtain multiple EVM values.

[0039] In this step, blind demodulation is attempted one by one for the selected candidate modulation modes, and the corresponding EVM value is calculated.

[0040] In this embodiment, after the type of the input wireless signal is identified, a plurality of candidate modulation modes can be obtained; the demodulation parameters are set according to the input signal type, including the symbol rate, sampling rate and initial frequency deviation, etc. If the symbol rate and frequency deviation are unknown, it is necessary to perform symbol rate estimation and frequency deviation estimation according to the modulation mode.

[0041] In this embodiment, the signal demodulation step includes: (1) Frequency offset compensation: The frequency offset of the signal is preliminarily estimated through frequency domain analysis method, and the signal frequency domain data is compensated.

[0042] (2) Symbol synchronization: Utilizing the symbol characteristics of a specific modulation method, the symbol rate is obtained through symbol rate estimation, and the optimal synchronization point is obtained through blind synchronization and EVM calculation.

[0043] (3) Constellation recovery: Based on the modulation method, the demodulation result is mapped to a standard constellation shape, such as the grid pattern of QAM or the phase circle of PSK.

[0044] (4) Error calculation: Match the constellation diagram of the received signal with the ideal constellation diagram and calculate the error vector magnitude (EVM) value; try to demodulate each candidate modulation method one by one and record the EVM value of each modulation method.

[0045] Specifically, the above EVM value can be calculated by the following formula: ; in, For the The error vector of the symbol (the complex difference between the demodulated symbol and the ideal constellation point), N is the number of error vectors, is the average power of the ideal symbol.

[0046] Step 140: Use the synchronization point optimization strategy to select a target EVM value from multiple EVM values ​​to obtain a target modulation mode to achieve demodulation of the wireless signal.

[0047] In this step, the EVM value is used as an evaluation standard for demodulation performance. The lower the EVM, the closer the demodulation result is to the ideal constellation. For example, an EVM threshold for successful demodulation is set, and a modulation mode below the threshold is judged to be demodulated successfully, and the modulation mode and its parameters (such as symbol rate, frequency deviation, phase deviation, etc.) that are successfully demodulated are output.

[0048] In this embodiment, the demodulation result obtained according to the target modulation mode includes parameters such as the demodulated symbol stream, the modulation mode index, and the EVM value, which are used to provide input for subsequent signal processing.

[0049] Specifically, the process of blindly synchronizing and demodulating a continuous wireless signal includes: (1) Resample the signal to sps times the symbol rate, where the sps value is the interpolation multiple to ensure that there are integer samples within one symbol. The recommended sps value is 8 or 16; (2) By looping through each possible starting synchronization point (from 1 to sps), for each synchronization point, extract the sampled value of each symbol and use the sampled value to calculate the EVM; (3) Normalize the sampled values ​​to the average value, and then calculate the EVM using the ideal constellation diagram as a reference; (4) In actual operation, the synchronization point corresponding to the minimum EVM can be selected as the synchronization point of the signal, and the best extraction value of the signal can be extracted from this synchronization point as the data for subsequent processing.

[0050] The modulation identification method of wireless signals provided by the embodiment of the present invention extracts target features from the wireless signals to obtain the signal type of the wireless signals, determines candidate modulation modes according to the signal types, and then blindly modulates the wireless signals using the candidate modulation modes and calculates the error vector magnitude (EVM). Finally, a synchronization point optimization strategy is used to screen out the target EVM value from multiple EVM values ​​to obtain the target modulation mode, so as to realize demodulation of the wireless signals. By integrating the multi-dimensional features of the wireless signals and combining the error vector magnitude (EVM) to assist in the decision, the robustness and accuracy of the recognition under low signal-to-noise ratio conditions are enhanced.

[0051] In some embodiments, the target features are time domain features, frequency domain features, and time-frequency domain features; wherein the time domain features include the flatness of the signal envelope of the wireless signal; the frequency domain features include the number of peaks and the flatness of the spectrum of the power spectrum of the wireless signal; the time-frequency domain features include the flatness of the instantaneous frequency of the wireless signal; obtaining the signal type of the wireless signal based on the target features includes: When the number of peaks of the power spectrum of different powers of the wireless signal is 1 and the spectrum flatness of different powers is greater than the first threshold, it is determined that the signal type of the wireless signal includes a constant envelope signal.

[0052] In this embodiment, the first threshold is within the range of 0.2-0.5, for example, the first threshold is 0.3.

[0053] In this embodiment, if condition 1: the number of spectrum peaks of the first power, second power and fourth power of the signal is all 1 (vPeakNum is all 1), condition 2: the spectrum flatness of the first power, second power and fourth power of the signal is all greater than 0.3 (vKur>0.3), if either condition is not met, then continue to determine whether the wireless signal is an AM signal or a CW signal.

[0054] When the flatness of the signal envelope of the wireless signal is greater than the second threshold, and the flatness of the instantaneous frequency is greater than the third threshold, it is determined that the signal type of the wireless signal includes an amplitude modulation signal.

[0055] In this embodiment, the second threshold is within the range of 1-1.8, for example, the first threshold is 1.27; the third threshold is within the range of 1.5-2, for example, the first threshold is 1.8.

[0056] In this embodiment, the amplitude modulation signal includes a 2ASK signal or a 4ASK signal.

[0057] When the number of peaks of the 1st power power spectrum of the wireless signal is 0, the 1st power spectrum flatness is less than or equal to the first threshold, the number of peaks of the 4th power spectrum is 1, the 4th power spectrum flatness is greater than the first threshold, the instantaneous frequency flatness is less than or equal to the fourth threshold, and the flatness of the signal envelope is less than the fifth threshold, it is confirmed that the signal type of the wireless signal includes a quaternary offset quadrature phase shift keying signal 4OQPSK signal.

[0058] In this embodiment, the fourth threshold is within the range of 0.3-0.8, for example, the third threshold is 0.5; the fifth threshold is within the range of 0.2-0.5, for example, the fifth threshold is 0.35.

[0059] In this embodiment, whether the wireless signal includes a 4OQPSK signal is determined by the following determination conditions: Condition 1: The signal's first-order spectrum has no peak (vPeakNum(1) = 0), and the number of peaks in the fourth-order spectrum is 1 (vPeakNum(3) = 1), the first-order spectrum flatness vKur(1) is less than or equal to 0.3, and the fourth-order spectrum flatness vKur(3) is greater than 0.3.

[0060] Condition 2: The number of peaks in the quadratic spectrum of the signal is 2 (vPeakNum(2) ==2) and its flatness vKur(2) is less than or equal to 0.15; Alternatively, the instantaneous frequency flatness ftAbsKur0 is less than or equal to 0.5 and the envelope flatness evlpKur0 is less than 0.35.

[0061] If both condition 1 and condition 2 are satisfied at the same time, it is determined that the current wireless signal may be a 4OQPSK signal, and the current wireless signal is demodulated using the corresponding candidate modulation method. If the demodulation is successful, the subsequent steps are not performed.

[0062] The modulation identification method of wireless signals provided in the embodiment of the present invention realizes the step-by-step screening and rapid demodulation of constant envelope signals, amplitude modulated signals and 4OQPSK signals by extracting time domain features, frequency domain features and time-frequency domain features from wireless signals, thereby improving the real-time performance of the signal blind demodulation process.

[0063] In some embodiments, the target features are time domain features and frequency domain features; wherein the time domain features include the modulation depth of the signal envelope of the wireless signal; and the frequency domain features include the number of peaks and the spectrum flatness of the power spectrum of the wireless signal.

[0064] In this embodiment, in the process of identifying whether the wireless signal contains an amplitude modulation AM signal, the following processing may be performed to obtain corresponding time domain features and frequency domain features: 1. Perform spectrum analysis, use FFT to extract the signal spectrum, and find the main frequency component position estFcIdx corresponding to the wireless signal; then call the fine frequency estimation module to obtain a more accurate frequency offset estFc.

[0065] 2. Calculate the modulation depth, extract the signal envelope, and calculate the modulation depth (modDepth) as the characteristic parameter of the AM signal.

[0066] 3. Power spectrum characteristic analysis: perform power processing on the signal envelope and calculate the flatness and peak number of the power spectrum. The results are stored in vKurAM and vPeakNumAM.

[0067] The signal types for obtaining wireless signals based on target characteristics also include: Condition 1: when the number of peaks of the first-power power spectrum of the wireless signal is 2 and the spectrum flatness meets the sixth threshold, it is confirmed that the signal type of the wireless signal includes a binary frequency shift keying 2FSK signal and an amplitude modulation AM signal.

[0068] Condition 2: when the number of peaks of the square power spectrum of the wireless signal is 2 and the square spectrum flatness meets the sixth threshold, it is confirmed that the signal type of the wireless signal includes a binary minimum shift keying 2MSK signal and an AM signal.

[0069] When the number of peaks of the first-power power spectrum of the wireless signal is 2 and the first-power spectrum flatness satisfies the sixth threshold, it is determined that the signal type of the wireless signal includes a 2FSK signal.

[0070] In addition, whether the wireless signal is an AM signal can be determined by the calculated modulation depth; specifically: when the modulation depth is greater than the seventh threshold, the signal type of the wireless signal includes an AM signal; when the modulation depth is less than or equal to the seventh threshold, the signal type of the wireless signal includes a continuous wave CW signal.

[0071] In this embodiment, the sixth threshold is within the range of 0.05-0.5, for example, the sixth threshold is 0.1-0.35; the seventh threshold is within the range of 0.05-0.3, for example, the seventh threshold is 0.1.

[0072] The modulation identification method of wireless signals provided in the embodiment of the present invention realizes the gradual screening and rapid demodulation of single-type modulation modes (2FSK, AM, CW) and mixed modulation modes (2FSK+AM, 2MSK+AM) by extracting time domain features and frequency domain features from wireless signals, thereby further improving the real-time performance of the signal blind demodulation process.

[0073] In some embodiments, the target features are frequency domain features and time-frequency domain features; wherein the frequency domain features include the number of peaks and the spectrum flatness of the power spectrum of the wireless signal; and the time-frequency domain features include the instantaneous frequency flatness of the wireless signal.

[0074] The signal types for obtaining wireless signals based on target characteristics also include: (1) When the number of peaks of the first-power power spectrum of the wireless signal is 0, the first-power spectrum flatness is less than or equal to the first threshold, and the number of peaks of the second-power power spectrum is 2, and the second-power spectrum flatness meets the eighth threshold, it is confirmed that the signal type of the wireless signal includes a 2MSK or a binary Gaussian minimum shift keying 2GMSK signal, thereby realizing the determination of the quadratic spectrum characteristic signal.

[0075] (2) When the number of peaks of the first-power power spectrum of the wireless signal is 0, the first-power spectrum flatness is less than or equal to the first threshold, and the number of peaks of the second-power power spectrum is 1 or 3, the second-power spectrum flatness is greater than the first threshold, and the instantaneous frequency flatness is greater than the third threshold, it is confirmed that the signal type of the wireless signal includes a binary phase shift keying 2PSK signal, thereby realizing the determination of single-peak / multi-peak signals of the quadratic spectrum.

[0076] In this embodiment, the eighth threshold is within the range of 0.1-0.5, for example, the sixth threshold is 0.15-0.3.

[0077] The modulation identification method of wireless signals provided by the embodiment of the present invention realizes the step-by-step screening and rapid demodulation of 2MSK, 2GMSK and 2PSK signals by extracting frequency domain features and time-frequency domain features from wireless signals, thereby further improving the real-time performance of the signal blind demodulation process.

[0078] In some embodiments, the target feature is a frequency domain feature; wherein the frequency domain feature includes the number of peaks and the degree of spectrum flatness of the power spectrum of the wireless signal.

[0079] The signal types for obtaining wireless signals based on target characteristics also include: (1) When the number of peaks of the 1st power spectrum of the wireless signal is 0, the number of peaks of the 4th power spectrum is 1 or 3, and the number of peaks of the 2nd power spectrum is 1, it is determined that the signal type of the wireless signal includes an octal quadrature amplitude modulation 8QAM signal.

[0080] (2) When the number of peaks of the 1st power spectrum of the wireless signal is 0, the number of peaks of the 4th power spectrum is 1 or 3, and the number of peaks of the 2nd power spectrum is not 1, it is confirmed that the signal type of the wireless signal includes a quaternary phase shift keying 4PSK or 8QAM signal.

[0081] (3) when the number of peaks of the 1st power spectrum and the 2nd power spectrum of the wireless signal is 0, and the number of peaks of the 4th power spectrum is 1 or 3, confirming that the signal type of the wireless signal includes a 16 / 32 / 64QAM signal; (4) When the number of peaks of the 1st, 2nd, 4th, and 8th power spectrums of the wireless signal is 0 and the number of peaks of the 16th power spectrum is 1, it is confirmed that the signal type of the wireless signal includes a hexadecimal amplitude phase modulation 16APSK signal.

[0082] The above four types of recognition methods all recognize 4PSK, 8 / 16 / 32 / 64QAM and 16APSK signals through the number of peaks of the power spectrum in the frequency domain characteristics.

[0083] When the number of peaks of the first-power power spectrum of the wireless signal is 0, the first-power spectrum flatness is less than or equal to the first threshold, the number of peaks of the fourth-power spectrum is 1, the fourth-power spectrum flatness is greater than the first threshold, and the number of peaks of the second-power spectrum is 2, and the second-power spectrum flatness is less than or equal to the ninth threshold, it is confirmed that the signal type of the wireless signal includes a 4OQPSK signal; this method recognizes the 4OQPSK signal through the number of peaks of the power spectrum and the spectrum flatness in the frequency domain features.

[0084] In this embodiment, the ninth threshold is within the range of 0.1-0.3, for example, the sixth threshold is 0.15.

[0085] The modulation identification method of wireless signals provided by the embodiment of the present invention realizes the step-by-step screening and rapid demodulation of 4PSK, 8 / 16 / 32 / 64QAM, 16APSK and 4OQPSK signals by extracting frequency domain features from wireless signals, thereby further improving the real-time performance of the signal blind demodulation process.

[0086] In some embodiments, the target feature also includes a time domain feature; the time domain feature includes the flatness of the signal envelope of the wireless signal.

[0087] In this embodiment, the refinement processing of the FM signal is achieved by the following steps: If the envelope flatness of the signal evlpR is less than or equal to the tenth threshold, the processing flow of the FM composite modulation signal is entered.

[0088] Specifically, obtaining the signal type of the wireless signal based on the target feature also includes: (1) When the flatness of the signal envelope is less than or equal to the tenth threshold and the wireless signal can be demodulated by a frequency modulation (FM) signal, confirm that the signal type of the wireless signal includes a 2FSK or MSK modulated signal; (2) When the flatness of the signal envelope is less than or equal to the tenth threshold, the wireless signal cannot be FM demodulated, and the ratio of the sampling rate to the bit rate of the wireless signal is not an integer, it is determined that the signal type of the wireless signal includes an FM signal.

[0089] In this embodiment, the tenth threshold is within the range of 0.8-1.2, for example, the tenth threshold is 1.13.

[0090] The modulation identification method of wireless signals provided by the embodiment of the present invention realizes the gradual screening and rapid demodulation of 2FSK, MSK and FM signals by extracting time domain features from wireless signals, thereby further improving the real-time performance of the signal blind demodulation process.

[0091] Furthermore, the target features are frequency domain features and time-frequency domain features; wherein the frequency domain features include the number of peaks and spectrum flatness of the power spectrum of the wireless signal; and the time-frequency domain features include the instantaneous frequency flatness of the wireless signal.

[0092] The signal types for obtaining wireless signals based on target characteristics also include: Condition 1: The number of peaks of the first power spectrum and the second power spectrum of the wireless signal is 0, and the number of peaks of the fourth power spectrum is 2 or 4; Condition 2: The 1st power spectrum flatness satisfies the sixth threshold, and the instantaneous frequency flatness is greater than the eleventh threshold.

[0093] If both condition 1 and condition 2 are met at the same time, it is determined that the signal may be a π / 4QPSK signal, and the corresponding candidate modulation method is selected to demodulate the wireless signal. If the demodulation is successful, the subsequent steps are no longer performed.

[0094] Condition 1: The number of peaks of the first power spectrum of the wireless signal is 0, the number of peaks of the second power spectrum is 1, and the number of peaks of the fourth power spectrum is 1 or 2; Condition 2: the 1st power spectrum flatness is less than the ninth threshold, the 2nd power spectrum flatness and the 4th power spectrum flatness are greater than the first threshold, and the instantaneous frequency flatness is greater than the 11th threshold.

[0095] If both conditions 1 and 2 are met at the same time, it is determined that the signal may be a 4π differential quadrature phase shift keying 4π / DQPSK signal, and the corresponding candidate modulation method is selected for wireless signal demodulation. If the demodulation is successful, the subsequent steps are no longer performed.

[0096] When the number of peaks of the 1st power spectrum, the 2nd power spectrum and the 4th power spectrum of the wireless signal is 0 and the instantaneous frequency flatness is greater than the eleventh threshold, it is confirmed that the signal type of the wireless signal includes an 8PSK signal.

[0097] In this embodiment, it is also possible to determine whether the wireless signal contains 2 / 4 / 8FSK according to the instantaneous frequency flatness in the time-frequency domain characteristics.

[0098] Specifically, if the instantaneous frequency flatness (ftNormAbsR) is less than 1.13, it is determined that the wireless signal includes: 2FSK, 4FSK and 8FSK signals, and the corresponding candidate modulation method is selected to demodulate the wireless signal. If the demodulation is successful, the subsequent steps are no longer performed, otherwise it is determined that the input signal cannot be identified and demodulated.

[0099] In this embodiment, the eleventh threshold is within the range of 0.3-0.6, for example, the eleventh threshold is 0.45.

[0100] The modulation identification method of wireless signals provided in the embodiment of the present invention realizes the step-by-step screening and rapid demodulation of π / 4QPSK, 4π / DQPSK, 8PSK and 2 / 4 / 8FSK signals by extracting time domain features and time-frequency domain features from wireless signals, thereby further improving the real-time performance of the signal blind demodulation process.

[0101] Figure 2 This is a second flow chart of the modulation identification method of wireless signals provided by the present invention. Figure 2 In the embodiment shown, a modulation identification method for a wireless signal is also implemented by the following steps: step 1, calculation of the time domain characteristics, frequency domain characteristics and time-frequency domain characteristics of the signal; step 2, preliminary judgment of the constant envelope signal; step 3, refinement of the AM signal; step 4, determination of MSK and FSK signals; step 5, AM and CW judgment; step 6, subsequent judgment beyond the constant envelope signal; step 7, determination of the quadratic spectrum characteristic signal; step 8, determination of the quadratic spectrum single-peak / multi-peak signal; step 9, determination of the quartic spectrum characteristic signal; step 10, determination of the 4OQPSK signal; step 11, determination of the π / 4QPSK signal; step 12, determination of the 4π / DQPSK signal; step 13, determination of the 8PSK signal; step 14, determination of the 16 / 32 / 64QAM; step 15, determination of the 16APSK; step 16, refinement of the FM signal; step 17, determination of FSK.

[0102] In summary, combined with the above embodiments of the present application, the following advantages are possessed: (1) It covers the recognition and blind demodulation of linear modulation modes including AM, FM, PSK, QAM, as well as high-order modulation modes (such as 64QAM, 16APSK) and composite modulation modes (such as 2FSK+FM, MSK+AM). Through multi-dimensional feature analysis and judgment, it significantly expands the scope of application of modulation modes; (2) Comprehensively extract time domain features (such as envelope smoothness), frequency domain features (such as the number and flatness of the power spectrum), and time-frequency domain features (such as the degree of instantaneous frequency smoothness) to form a multi-dimensional feature fusion decision system, which improves the robustness and accuracy in complex signals and low signal-to-noise ratio environments; (3) Proposes a method for identifying composite modulated signals. For example, by using the characteristics of the flatness of the second-order spectrum and the number of peaks, it can accurately distinguish composite signals such as 2FSK+FM and MSK+AM, thereby improving the processing capability of complex modulation methods and solving the shortcomings of existing technologies. (4) A blind demodulation strategy with hierarchical decision and gradual optimization is adopted. Through preliminary screening, candidate demodulation attempts, EVM comparison and other steps, the optimal demodulation method is quickly converged, the real-time processing performance is optimized, and the real-time application requirements under dynamic channels are met.

[0103] The modulation identification device for wireless signals provided by the present invention is described below. The modulation identification device for wireless signals described below and the modulation identification method for wireless signals described above can be referred to each other.

[0104] Figure 3 Schematic diagram of the structure of the modulation identification device of the wireless signal provided by the present invention, such as Figure 3 As shown, the modulation identification device 300 for wireless signals includes: a feature extraction module 310 , a modulation identification module 320 , a calculation module 330 and a screening module 340 .

[0105] A feature extraction module 310 is used to extract a target feature from the wireless signal, where the target feature is at least one of a time domain feature, a frequency domain feature, and a time-frequency domain feature; The modulation identification module 320 obtains the signal type of the wireless signal based on the target feature and determines at least one candidate modulation mode according to the signal type; A calculation module 330 is used to blindly modulate the wireless signal using the candidate modulation mode and calculate the error vector magnitude (EVM) for each candidate modulation mode to obtain multiple EVM values; The screening module 340 is used to screen out a target EVM value from multiple EVM values ​​by adopting a synchronization point optimization strategy, and obtain a target modulation mode to achieve demodulation of the wireless signal.

[0106] The modulation identification device for wireless signals provided by the embodiment of the present invention extracts target features from the wireless signals to obtain the signal type of the wireless signals, determines candidate modulation modes according to the signal type, and then blindly modulates the wireless signals using the candidate modulation modes and calculates the error vector magnitude (EVM). Finally, a synchronization point optimization strategy is used to screen out a target EVM value from multiple EVM values ​​to obtain a target modulation mode, so as to realize demodulation of the wireless signals. By integrating the multi-dimensional features of the wireless signals and combining the error vector magnitude (EVM) to assist in decision making, the robustness and accuracy of recognition under low signal-to-noise ratio conditions are enhanced.

[0107] The modulation identification device for wireless signals provided by the present invention is described below. The modulation identification device for wireless signals described below and the modulation identification method for wireless signals described above can be referred to each other.

[0108] Figure 4 Schematic diagram of the structure of the wireless signal blind demodulation system provided by the present invention. Figure 4As shown, the wireless signal blind demodulation system includes: a signal receiving module 410, a wireless signal modulation identification device 300 and a demodulation module 420.

[0109] The signal receiving module 410 is used for wireless signals.

[0110] In this embodiment, the signal receiving module 410 can receive input wireless signal data via wireless signals, and can also receive a candidate list of specific modulation methods; the candidate list is determined by the above steps 110-120, and can also be set according to expert experience or user needs.

[0111] In this embodiment, the modulation identification device 300 of the wireless signal includes: The feature extraction module is used to extract target features from wireless signals, where the target features are at least one of time domain features, frequency domain features, and time-frequency domain features.

[0112] A modulation identification module, which obtains the signal type of the wireless signal based on the target characteristics and determines at least one candidate modulation mode according to the signal type; A calculation module, for blindly modulating the wireless signal using the candidate modulation mode and calculating the error vector magnitude (EVM) for each candidate modulation mode, to obtain multiple EVM values; The screening module is used to screen out a target EVM value from multiple EVM values ​​by adopting a synchronization point optimization strategy to obtain a target modulation mode so as to realize demodulation of the wireless signal.

[0113] In this embodiment, the implementation methods of the corresponding functions of the feature extraction module, the modulation identification module, the calculation module and the screening module are respectively the same as those of the above-mentioned step 110 to step 140 corresponding to the embodiment, and will not be repeated in this embodiment.

[0114] The demodulation module 420 is used to demodulate the wireless signal according to the target modulation mode output by the modulation identification device of the wireless signal to obtain a demodulation result; wherein the demodulation result includes at least one of the demodulated symbol stream, the modulation mode index, and the EVM value.

[0115] In an embodiment, the demodulation module 420 sets demodulation parameters according to the input signal type, including symbol rate, sampling rate, and initial frequency offset. If the symbol rate and frequency offset are unknown, it is necessary to perform symbol rate estimation and frequency offset estimation according to the modulation method. The signal demodulation steps include: (1) frequency offset compensation, (2) symbol synchronization, (3) constellation recovery, and (4) error calculation.

[0116] In this embodiment, the demodulation module 420 sets an EVM threshold for successful demodulation, and a modulation mode below the threshold is determined to be successfully demodulated, and outputs the successfully demodulated modulation mode and its parameters (such as symbol rate, frequency deviation, phase deviation, etc.).

[0117] The wireless signal blind demodulation system provided by the embodiment of the present invention sets a wireless signal receiving module, extracts target features from the wireless signal through a modulation identification device of the wireless signal to obtain the signal type of the wireless signal, determines a candidate modulation mode according to the signal type, and then adopts the candidate modulation mode to blindly modulate the wireless signal and calculate the error vector magnitude (EVM). Finally, a synchronization point optimization strategy is adopted to screen out a target EVM value from multiple EVM values ​​to obtain a target modulation mode. Finally, a demodulation module is used to demodulate the wireless signal according to the target modulation mode output by the modulation identification device of the wireless signal to obtain a demodulation result. A multi-stage decision process is designed for blind demodulation of wireless signals to screen the modulation modes, thereby avoiding blind demodulation with a large traversal range and a large number of times, reducing the number of times the blind demodulation module is called, and improving the blind demodulation efficiency and accuracy of wireless signals.

[0118] Figure 5 An example of a physical structure diagram of an electronic device is shown in FIG. Figure 5 As shown, the electronic device may include: a processor 510, a communication interface 520, a memory 530 and a communication bus 540, wherein the processor 510, the communication interface 520 and the memory 530 communicate with each other through the communication bus 540. The processor 510 may call the logic instructions in the memory 530 to execute the modulation identification method of the wireless signal, the method comprising: extracting a target feature from the wireless signal, the target feature being at least one of a time domain feature, a frequency domain feature and a time-frequency domain feature; obtaining the signal type of the wireless signal based on the target feature, and determining at least one candidate modulation mode according to the signal type; for each candidate modulation mode, blindly modulating the wireless signal using the candidate modulation mode and calculating the error vector magnitude EVM to obtain multiple EVM values; using the synchronization point optimization strategy to filter out the target EVM value from the multiple EVM values ​​to obtain the target modulation mode to achieve demodulation of the wireless signal.

[0119] In addition, the logic instructions in the above-mentioned memory 530 can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when it is sold or used as an independent product. Based on such an understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0120] On the other hand, the present invention also provides a computer program product, which includes a computer program. The computer program can be stored on a non-transitory computer-readable storage medium. When the computer program is executed by a processor, the computer can execute the modulation identification method of the wireless signal provided by the above methods, and the method includes: extracting a target feature from the wireless signal, the target feature is at least one of a time domain feature, a frequency domain feature, and a time-frequency domain feature; obtaining a signal type of the wireless signal based on the target feature, and determining at least one candidate modulation method according to the signal type; for each candidate modulation method, blindly modulating the wireless signal using the candidate modulation method and calculating the error vector magnitude EVM to obtain multiple EVM values; using a synchronization point optimization strategy to filter out a target EVM value from multiple EVM values ​​to obtain a target modulation method to achieve demodulation of the wireless signal.

[0121] On the other hand, the present invention also provides a non-transitory computer-readable storage medium having a computer program stored thereon, which, when executed by a processor, is implemented to execute the modulation identification method of the wireless signal provided by the above-mentioned methods, the method comprising: extracting a target feature from the wireless signal, the target feature being at least one of a time domain feature, a frequency domain feature, and a time-frequency domain feature; obtaining a signal type of the wireless signal based on the target feature, and determining at least one candidate modulation method according to the signal type; for each candidate modulation method, blindly modulating the wireless signal using the candidate modulation method and calculating the error vector magnitude EVM to obtain multiple EVM values; and using a synchronization point optimization strategy to screen out a target EVM value from multiple EVM values ​​to obtain a target modulation method to achieve demodulation of the wireless signal.

[0122] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0123] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A modulation identification method for a wireless signal, characterized in that: include: Extracting a target feature from the wireless signal, wherein the target feature is at least one of a time domain feature, a frequency domain feature, and a time-frequency domain feature; Acquire a signal type of the wireless signal based on the target feature, and determine at least one candidate modulation mode according to the signal type; For each of the candidate modulation modes, blindly modulate the wireless signal using the candidate modulation mode and calculate the error vector magnitude (EVM) to obtain multiple EVM values; A synchronization point optimization strategy is adopted to screen out a target EVM value from the multiple EVM values, and a target modulation mode is obtained to achieve demodulation of the wireless signal.

2. The method for modulation identification of wireless signals according to claim 1, characterized in that: The target features are time domain features, frequency domain features and time-frequency domain features; wherein the time domain features include the flatness of the signal envelope of the wireless signal; the frequency domain features include the number of peaks and the flatness of the spectrum of the power spectrum of the wireless signal; the time-frequency domain features include the flatness of the instantaneous frequency of the wireless signal; The acquiring the signal type of the wireless signal based on the target feature comprises: When the number of peaks of the power spectrum of different powers of the wireless signal is 1 and the spectrum flatness of different powers is greater than a first threshold, determining that the signal type of the wireless signal includes a constant envelope signal; When the flatness of the signal envelope of the wireless signal is greater than the second threshold, and the flatness of the instantaneous frequency is greater than the third threshold, confirming that the signal type of the wireless signal includes an amplitude modulation signal; When the number of peaks of the 1st power power spectrum of the wireless signal is 0, the 1st power spectrum flatness is less than or equal to the first threshold, the number of peaks of the 4th power spectrum is 1, the 4th power spectrum flatness is greater than the first threshold, the instantaneous frequency flatness is less than or equal to the fourth threshold, and the flatness of the signal envelope is less than the fifth threshold, it is confirmed that the signal type of the wireless signal includes a quaternary offset quadrature phase shift keying signal ‌4OQPSK signal.

3. The method for modulation identification of wireless signals according to claim 1, characterized in that: The target features are time domain features and frequency domain features; wherein the time domain features include the modulation depth of the signal envelope of the wireless signal; the frequency domain features include the number of peaks and the spectrum flatness of the power spectrum of the wireless signal; The acquiring the signal type of the wireless signal based on the target feature further comprises: When the number of peaks of the first-power power spectrum of the wireless signal is 2 and the spectrum flatness satisfies a sixth threshold, confirming that the signal type of the wireless signal includes a binary frequency shift keying 2FSK signal and an amplitude modulation AM signal; When the number of peaks of the square power spectrum of the wireless signal is 2 and the square spectrum flatness meets the sixth threshold, confirming that the signal type of the wireless signal includes a binary minimum shift keying 2MSK signal and an AM signal; When the modulation depth is greater than the seventh threshold, the signal type of the wireless signal includes an AM signal; when the modulation depth is less than or equal to the seventh threshold, the signal type of the wireless signal includes a continuous wave CW signal; When the number of peaks of the first-power power spectrum of the wireless signal is 2 and the first-power spectrum flatness satisfies the sixth threshold, it is determined that the signal type of the wireless signal includes a 2FSK signal.

4. The method for modulation identification of wireless signals according to claim 1, characterized in that: The target features are frequency domain features and time-frequency domain features; wherein the frequency domain features include the number of peaks and spectrum flatness of the power spectrum of the wireless signal; the time-frequency domain features include the instantaneous frequency flatness of the wireless signal; The acquiring the signal type of the wireless signal based on the target feature further comprises: When the number of peaks of the first-power power spectrum of the wireless signal is 0, the first-power spectrum flatness is less than or equal to the first threshold, and the number of peaks of the second-power power spectrum is 2, and the second-power spectrum flatness meets the eighth threshold, confirming that the signal type of the wireless signal includes a 2MSK or a binary Gaussian minimum shift keying 2GMSK signal; When the number of peaks of the first-power power spectrum of the wireless signal is 0, the first-power spectrum flatness is less than or equal to the first threshold, the number of peaks of the second-power power spectrum is 1 or 3, the second-power spectrum flatness is greater than the first threshold, and the instantaneous frequency flatness is greater than the third threshold, it is confirmed that the signal type of the wireless signal includes a binary phase shift keying 2PSK signal.

5. The method for modulation identification of wireless signals according to claim 1, characterized in that: The target feature is a frequency domain feature; wherein the frequency domain feature includes the number of peaks and the degree of spectrum flatness of the power spectrum of the wireless signal; The acquiring the signal type of the wireless signal based on the target feature further comprises: When the number of peaks of the 1st power spectrum of the wireless signal is 0, the number of peaks of the 4th power spectrum is 1 or 3, and the number of peaks of the 2nd power spectrum is 1, confirming that the signal type of the wireless signal includes an octal quadrature amplitude modulation 8QAM signal; When the number of peaks of the 1st power spectrum of the wireless signal is 0, the number of peaks of the 4th power spectrum is 1 or 3, and the number of peaks of the 2nd power spectrum is not 1, confirming that the signal type of the wireless signal includes a quaternary phase shift keying 4PSK or 8QAM signal; When the number of peaks of the 1st power spectrum and the 2nd power spectrum of the wireless signal is 0, and the number of peaks of the 4th power spectrum is 1 or 3, confirming that the signal type of the wireless signal includes a 16 / 32 / 64QAM signal; When the number of peaks of the 1st, 2nd, 4th and 8th power spectrums of the wireless signal is 0 and the number of peaks of the 16th power spectrum is 1, confirming that the signal type of the wireless signal includes a hexadecimal amplitude phase modulation 16APSK signal; When the number of peaks of the 1st power spectrum of the wireless signal is 0, the 1st power spectrum flatness is less than or equal to the first threshold, the number of peaks of the 4th power spectrum is 1, the 4th power spectrum flatness is greater than the first threshold, and the number of peaks of the 2nd power spectrum is 2, and the 2nd power spectrum flatness is less than or equal to the ninth threshold, it is confirmed that the signal type of the wireless signal includes a 4OQPSK signal.

6. The method for modulation identification of wireless signals according to claim 5, characterized in that: The target feature also includes a time domain feature; the time domain feature includes the flatness of the signal envelope of the wireless signal; The acquiring the signal type of the wireless signal based on the target feature further comprises: When the flatness of the signal envelope is less than or equal to a tenth threshold and the wireless signal can be demodulated by a frequency modulation FM signal, confirming that the signal type of the wireless signal includes a 2FSK or MSK modulated signal; When the flatness of the signal envelope is less than or equal to the tenth threshold, the wireless signal cannot be FM demodulated, and the ratio of the sampling rate to the bit rate of the wireless signal is not an integer, it is confirmed that the signal type of the wireless signal includes an FM signal.

7. The method for modulation identification of wireless signals according to claim 1, characterized in that: The target features are frequency domain features and time-frequency domain features; wherein the frequency domain features include the number of peaks and spectrum flatness of the power spectrum of the wireless signal; the time-frequency domain features include the instantaneous frequency flatness of the wireless signal; The acquiring the signal type of the wireless signal based on the target feature further comprises: When the number of peaks of the 1st power spectrum and the 2nd power spectrum of the wireless signal is 0, the number of peaks of the 4th power spectrum is 2 or 4, the 1st power spectrum flatness satisfies the sixth threshold, and the instantaneous frequency flatness is greater than the eleventh threshold, it is confirmed that the signal type of the wireless signal includes a π / 4QPSK signal; When the number of peaks of the 1st power spectrum of the wireless signal is 0, the number of peaks of the 2nd power spectrum is 1, the number of peaks of the 4th power spectrum is 1 or 2, the 1st power spectrum flatness is less than a ninth threshold, the 2nd power spectrum flatness and the 4th power spectrum flatness are greater than the first threshold, and the instantaneous frequency flatness is greater than an eleventh threshold, it is confirmed that the signal type of the wireless signal includes a 4π differential quadrature phase shift keying ‌ 4π / DQPSK signal; When the number of peaks of the 1st power spectrum, the number of peaks of the 2nd power spectrum and the number of peaks of the 4th power spectrum of the wireless signal are 0, and the instantaneous frequency flatness is greater than the eleventh threshold, it is confirmed that the signal type of the wireless signal includes an 8PSK signal.

8. A modulation identification device for wireless signals, characterized in that: include: A feature extraction module, used to extract a target feature from the wireless signal, wherein the target feature is at least one of a time domain feature, a frequency domain feature, and a time-frequency domain feature; A modulation identification module, which obtains a signal type of the wireless signal based on the target feature, and determines at least one candidate modulation mode according to the signal type; A calculation module, configured to, for each of the candidate modulation modes, use the candidate modulation mode to blindly modulate the wireless signal and calculate the error vector magnitude (EVM) to obtain a plurality of EVM values; The screening module is used to screen out a target EVM value from the multiple EVM values ​​by adopting a synchronization point optimization strategy to obtain a target modulation mode so as to realize demodulation of the wireless signal.

9. A wireless signal blind demodulation system, characterized in that: include: A signal receiving module, the signal receiving module is used for the wireless signal; The modulation identification device for wireless signals as claimed in claim 8; A demodulation module, the demodulation module is used to demodulate the wireless signal according to the target modulation mode output by the modulation identification device of the wireless signal to obtain a demodulation result; wherein the demodulation result includes at least one of the demodulated symbol stream, the modulation mode index, and the EVM value.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the modulation identification method of the wireless signal according to any one of claims 1 to 6 is implemented.

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