An M110-39T Detection Synchronization Method and System Based on Signal Time-Frequency Characteristics

Abstract

The present invention discloses a detection and synchronization method and system for M110-39T based on signal time-frequency characteristics, belonging to the field of short-wave communication technology. It includes: using a frequency-domain peak template to perform a sliding search on the signal to complete signal presence detection and carrier synchronization, where the frequency-domain peak template is constructed comprehensively based on the first-stage pre-synchronization code and Doppler tone of the M110-39T signal; using a time-domain phase template to perform a sliding search on the signal to complete signal coarse timing synchronization, where the time-domain phase template is constructed based on the second-stage pre-synchronization code of the M110-39T signal; adopting a cyclic prefix sliding correlation method to perform symbol synchronization on the data segment of the M110-39T signal. The present invention effectively utilizes various time-domain and frequency-domain characteristics to capture the pre-synchronization code, realizes accurate detection and synchronization of M110-39T in a short-wave time-varying channel, provides input parameters for signal demodulation, can adapt to the fading and changeable short-wave channel, and can cope with the scenario of large frequency offset, and has good robustness and practicability.

Description

Technical Field

[0001] The present invention belongs to the technical field of short-wave communication, and more specifically, relates to a detection and synchronization method and system for M110-39T based on signal time-frequency characteristics. Background Art

[0002] Short-wave communication has the advantages of long communication distance, simple equipment, strong anti-destruction ability, etc. However, short-wave communication has always had obvious defects such as low transmission rate, poor communication reliability and stability, and being easily interfered. Even when short-wave communication works at the best working frequency, during the signal transmission process, it will inevitably be affected by factors such as multipath effect, fading, Doppler frequency shift, etc., resulting in signal distortion. Therefore, how to improve communication quality and increase data transmission rate has always been the focus of research.

[0003] Currently, the signal systems used for short-wave data communication can be mainly divided into two types: single-tone serial and multi-tone parallel. The former mainly uses modulation methods such as PSK and QAM, and uses a relatively high baud rate for fast data transmission. Since the symbol period is short, it is easily affected by inter-symbol interference, so channel equalization operations need to be performed, consuming a large amount of system resources; the latter is to transmit information in parallel through several single tones (sub-carriers) within the effective bandwidth of the short-wave channel, and evenly distribute the data rate on multiple single tones, which can achieve a longer symbol period and avoid the influence of inter-symbol interference. Signals of both systems are widely used in the field of short-wave communication. Signal types using single-tone serial include M110A, M110B, 3G-ALE, Link-11B, etc., and signal types using multi-tone parallel include CLOVER-2000, M110-39T, Link-11A, CODAN-16T, etc.

[0004] M110-39T is one of the most common multi-tone parallel signals at present. It was first proposed in Appendix B of the MIL-STD-188-110A standard and has been preserved in subsequent updated versions. Its main technical specifications are: 39 data tones, with a frequency interval of 56.25Hz, ranging from 675Hz to 2812.5Hz, for data transmission; a single-frequency unmodulated Doppler tone, with a frequency of 393.75Hz, for correcting frequency deviation; the symbol length is 22.5ms, and the baud rate is 44.44Bd; each data tone is modulated by differential quadrature phase shift keying (DQPSK), and the initial phase is given; there are 6 types in total: 75bit / s, 150bit / s, 300bit / s, 600bit / s, 1200bit / s, 2400bit / s; RS code coding, interleaving, diversity and other technologies are adopted.

[0005] In the process of M110-39T signal processing, signal detection and synchronization are two key steps. The former identifies and verifies signals of specific specifications from the signals automatically detected by the carrier, and the latter synchronizes the frequency and time of the signals verified as M110-39T to determine the demodulation starting point. Since the preamble code of M110-39T has unique frequency domain characteristics, most of the currently proposed detection and synchronization methods are based on the first segment of the preamble code and use a detection method based on the subcarrier energy after FFT, which avoids the operation of using multiple low-pass filters but cannot handle the situation of carrier asynchronization, and the actual use effect is very poor.

[0006] For carrier synchronization, the common method is to estimate the frequency offset using the frequencies of multiple tones, but it is difficult to extract the positions of Doppler tones in the short-wave channel with obvious fading phenomenon.

[0007] For timing synchronization, the existing method uses the time domain characteristics of the second segment of the preamble code and completes symbol synchronization through the method of 128-point sliding FFT peak detection. Although this method is simple to implement, the duration of the second segment of the preamble code is short, which may cause a serious decline in performance in the case of low signal-to-noise ratio or fading.

[0008] Comprehensively analyzing the existing M110-39T signal processing methods, the signal detection and synchronization steps are not closely related and are not resistant to complex fading channels. M110-39T has only one set of preamble codes, and once the entire signal is missed, it cannot be processed. Therefore, more robust and accurate detection and synchronization methods are needed. Summary of the Invention

[0009] Aiming at the defects of the existing technology, the purpose of the present invention is to provide a method and system for M110-39T detection and synchronization based on the time-frequency characteristics of signals, aiming to solve the problems that the signal detection and synchronization steps of the existing M110-39T signal processing methods are not closely related and are not resistant to complex fading channels.

[0010] To achieve the above purpose, in the first aspect, the present invention provides a method for M110-39T detection and synchronization based on the time-frequency characteristics of signals, and the method includes:

[0011] S1. Using a frequency domain peak template, perform a sliding search on the signal to complete signal presence detection and carrier synchronization, and the frequency domain peak template is constructed based on the first segment of the preamble code of the M110-39T signal and Doppler tones;

[0012] S2. Using a time domain phase template, perform a sliding search on the signal to complete rough timing synchronization of the signal, and the time domain phase template is constructed based on the second segment of the preamble code of the M110-39T signal;

[0013] S3. Use the cyclic prefix sliding correlation method to perform symbol synchronization on the data segment of the M110-39T signal.

[0014] Preferably, step S1 specifically includes:

[0015] S11. Input the starting segment of the original IQ complex signal of the M110-39T signal into a three-segment buffer. The three-segment buffer is, from front to back, the first segment, the second segment, and the third segment. The duration of the first segment does not exceed 2 / 3 of the duration of the first pre-synchronization code, the duration of the second segment does not exceed the sum of the duration of the first pre-synchronization code and the duration of the second pre-synchronization code, and the duration of the third segment is not less than 1 s;

[0016] S12. Calculate the spectrum of the data filled into the first segment, and statistically count the frequencies f1, f2, f3, f4 corresponding to the 4 peaks with the highest amplitudes. The adjacent peak frequency intervals need to be greater than a preset threshold, and the preset threshold is close to the average value of the theoretical differences between the four peaks of the first pre-synchronization code of M110-39T;

[0017] S13. Calculate the spectrum of the data filled into the third segment and then filter it to extract the frequency f5 corresponding to the maximum amplitude;

[0018] S14. Complete signal presence detection and carrier synchronization through the values of f1 to f5.

[0019] Preferably, the filtering is median filtering.

[0020] Preferably, step S14 is specifically as follows:

[0021] S141. Sort f1 to f5 and calculate the frequency differences Δf1, Δf2, Δf3, Δf4 between adjacent frequencies;

[0022] S142. Calculate the peak difference S:

[0023] S = |Δf1 + Δf2 + Δf3 + Δf4 - f d - 3f * |

[0024] S143. Compare whether the peak difference is less than the detection threshold. If so, it indicates that the M110-39T signal is detected. Calculate the carrier frequency difference Δf = f5 - f0 and use the carrier frequency difference for carrier synchronization. Otherwise, slide the original IQ complex signal backward by the duration of the first segment, fill the three-segment buffer, and enter S12 to re-detect until the signal is detected or the end of the data is reached and stop;

[0025] Among them, f0 is the theoretical value of the multi-frequency pilot frequency, f d is the theoretical difference between the first frequency peak of the first pre-synchronization code and the frequency of the Doppler tone, f *It is the average of the theoretical differences between four peaks of the first-stage preamble code of M110-39T.

[0026] Preferably, step S2 is specifically as follows:

[0027] Extract the data containing the second-stage preamble code of the M110-39T signal;

[0028] Use a band-pass filter to filter out the 9th, 21st, and 33rd data tones;

[0029] Perform sliding correlation detection using phase time-domain templates respectively. The length of the phase time-domain template is the length of the second-stage preamble code, and the phase flips 180° per symbol;

[0030] Integrate the three detection results to obtain the starting time of the second part of the synchronization preamble.

[0031] Preferably, the extraction of the data containing the second-stage preamble code of the M110-39T signal is specifically: extract the data of 0.6 s starting from t0, where t0 is the starting moment corresponding to the three-stage buffer when carrier synchronization is completed.

[0032] Preferably, step S3 includes:

[0033] S31. Extract the data segment x of the M110-39T signal N ;

[0034] S32. Calculate the correlation sequence y i :

[0035] y i = [x i , x i+1 , …, x i+C-1 · [x i+L-C , x i+L-C+1 , …, x i+L-1 *

[0036] S33. Segment and sum y i according to L points, and extract the time delay corresponding to the peak point;

[0037] S34. Superimpose the time delay corresponding to the peak point on the starting moment of the data segment extraction as the starting time of the reference tone;

[0038] where i = 1, 2, …, N - L + 1, L is the number of signal sampling points within one symbol period, C is the number of sampling points of the cyclic prefix, N is the total number of sampling points of the data segment of the M110-39T signal extracted, and * represents the conjugate transpose of the matrix.

[0039] Preferably, the data segment of the M110-39T signal is extracted by the following method:

[0040] Determine the moment corresponding to at most 1 / 10 of the code length before the end of the second pre-synchronization code according to the start time of the second part of the synchronization preamble;

[0041] Taking this moment as the starting moment, extract data of a preset code length.

[0042] To achieve the above object, in a second aspect, the present invention provides an M110-39T detection synchronization system based on signal time-frequency characteristics, including a processor and a memory, the memory stores computer instructions, and the processor executes the computer instructions so that the computing device executes the method described in the foregoing first aspect.

[0043] To achieve the above object, in a third aspect, the present invention provides a computer-readable storage medium, the computer-readable storage medium stores computer program code, and when the computer program code is executed by a computing device, the computing device executes the method described in the foregoing first aspect.

[0044] Generally speaking, compared with the prior art through the above technical solutions conceived by the present invention, the following beneficial effects are obtained:

[0045] The present invention discloses an M110-39T detection synchronization method and system based on signal time-frequency characteristics, effectively utilizes the characteristics of M110-39T signals in the time-frequency space, respectively designs a frequency-domain peak template detection and a time-domain phase template, and uses a cyclic prefix sliding correlation method to detect and synchronize signals. This method uses a variety of time-domain and frequency-domain characteristics to capture the pre-synchronization code, realizes the accurate detection and synchronization of M110-39T in a short-wave time-varying channel, and provides input parameters for signal demodulation. It can adapt to the fading and changeable short-wave channel and can cope with the scenario of large frequency offset, and has good robustness and practicability. Description of the Drawings

[0046] Figure 1 It is a flowchart of an M110-39T detection synchronization method based on signal time-frequency characteristics provided by the present invention.

[0047] Figure 2 It is a schematic diagram of the frame structure of the M110-39T signal provided by the present invention.

[0048] Figure 3 It is a schematic diagram of the time-frequency structure characteristics of the M110-39T signal provided by the present invention.

[0049] Figure 4 It is a schematic diagram of the structure of the three-stage buffer D provided by the embodiments of the present invention.

[0050] Figure 5 It is a detection result diagram of the first pre-synchronization code and the Doppler tone sliding frequency spectrum template provided by the embodiments of the present invention.

[0051] Figure 6 This is the sliding detection result graph of the second pre - synchronization code phase template provided by the embodiment of the present invention.

[0052] Figure 7 This is the cyclic prefix sliding correlation symbol synchronization result graph provided by the embodiment of the present invention. Detailed implementation manners

[0053] In order to make the objectives, technical solutions and advantages of the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0054] As Figure 1 shown, the present invention provides an M110 - 39T detection synchronization method based on signal time - frequency characteristics. The method includes:

[0055] S1. Using a frequency - domain peak template to perform sliding search on the signal to complete signal presence detection and carrier synchronization. The frequency - domain peak template is constructed comprehensively based on the first - stage pre - synchronization code of the M110 - 39T signal and the Doppler tone.

[0056] S2. Using a time - domain phase template to perform sliding search on the signal to complete rough timing synchronization of the signal. The time - domain phase template is constructed based on the second - stage pre - synchronization code of the M110 - 39T signal.

[0057] S3. Adopting the cyclic prefix sliding correlation method to perform symbol synchronization on the data segment of the M110 - 39T signal.

[0058] As Figure 2 shown, the preamble of the M110 - 39T signal consists of three parts: The first part occupies 14 signal frame lengths, including 4 data tones. In each frame, only the all - 1 data that is not modulated is transmitted on the four data tone channels of the 3rd, 15th, 27th, and 39th; The second part occupies 8 signal frame lengths, including 3 data. In each frame, only the all - 1 data is transmitted on the three data tone channels of the 9th, 21st, and 33rd, and the signal phases of the front and rear two frames are opposite; The third part occupies one signal frame length, including 39 data tones and one Doppler correction tone, which is used to provide a reference phase for subsequent frames.

[0059] As Figure 3As shown, after the preamble is the data segment of the signal, which consists of block synchronization, data superblock, and asynchronous EOM, and they present conventional OFDM characteristics in the time-frequency structure. Therefore, the special time-frequency characteristics of the M110-39T signal are mainly reflected in the preamble. Among them, the first preamble code has continuous phase and presents significant peaks in the spectrum, so it is suitable for frequency-domain template detection; the second preamble code has discontinuous phase and flips 180° between symbols, so it is suitable for time-domain template detection. The Doppler pilot in the data segment is a single tone with continuous phase, so it is also suitable for spectrum template detection.

[0060] Preferably, step S1 specifically includes:

[0061] S11. Input the starting segment of the original IQ complex signal of the M110-39T signal into a three-section buffer. The three-section buffer is the first section, the second section, and the third section in sequence from front to back. The duration of the first section does not exceed 2 / 3 of the duration of the first preamble code, the duration of the second section does not exceed the sum of the duration of the first preamble code and the duration of the second preamble code, and the duration of the third section is not less than 1 s;

[0062] S12. Calculate the spectrum of the data filled in the first section, and statistically obtain the frequencies f1, f2, f3, f4 corresponding to the 4 peaks with the highest amplitudes. The adjacent peak frequency intervals need to be greater than a preset threshold, and the preset threshold is close to the average value of the theoretical differences between the four peaks of the first preamble code of the M110-39T;

[0063] S13. Filter the spectrum calculated from the data filled in the third section, and extract the frequency f5 corresponding to the maximum amplitude;

[0064] S14. Complete signal presence detection and carrier synchronization through the values of f1 to f5.

[0065] Preferably, the filtering is median filtering.

[0066] Preferably, step S14 is specifically as follows:

[0067] S141. Sort f1 to f5, and calculate the frequency differences Δf1, Δf2, Δf3, Δf4 between adjacent frequencies;

[0068] S142. Calculate the peak difference S:

[0069] S = |Δf1 + Δf2 + Δf3 + Δf4 - f d - 3f * |

[0070] S143. Compare whether the peak difference is less than the detection threshold. If so, it indicates that the M110-39T signal is detected. Calculate the carrier frequency difference Δf = f5 - f0, and use the carrier frequency difference for carrier synchronization. Otherwise, slide the original IQ complex signal backward by the duration of the first segment, fill the three-segment buffer, and enter S12 to re-detect until the signal is detected or the end of the data is reached and then stop.

[0071] Among them, f0 is the theoretical value of the multi-frequency pilot frequency, and f d is the theoretical frequency difference between the first frequency peak of the first segment of the pre-synchronization code and the Doppler tone, and f * is the average value of the theoretical differences between the four peaks of the first segment of the M110-39T pre-synchronization code.

[0072] Preferably, step S2 is specifically as follows: Extract the data containing the second segment of the M110-39T signal pre-synchronization code; Use a band-pass filter to filter out the 9th, 21st, and 33rd data tones; Perform sliding correlation detection using phase time-domain templates respectively. The length of the phase time-domain template is the length of the second segment of the pre-synchronization code, and the phase flips 180° per symbol; Combine the three detection results to obtain the start time of the second part of the synchronization preamble.

[0073] Preferably, the extraction of the data containing the second segment of the M110-39T signal pre-synchronization code is specifically: Extract the data of 0.6 s starting from t0, where t0 is the starting moment corresponding to the three-segment buffer when carrier synchronization is completed.

[0074] Preferably, step S3 includes:

[0075] S31. Extract the data segment x N ;

[0076] S32. Calculate the correlation sequence y i :

[0077] y i =[x i ,x i+1 ,…,x i+C-1 ·[x i+L-C ,x i+L-C+1 ,…,x i+L-1 *

[0078] S33. Sum y i in segments of L points and extract the time delay corresponding to the peak point;

[0079] S34. Add the time delay corresponding to the peak point to the starting moment of the data segment extraction as the starting time of the reference tone;

[0080] ​Wherein, i = 1, 2, …, N - L + 1, L is the number of signal sampling points within one symbol period, C is the number of sampling points of the cyclic prefix, N is the total number of sampling points of the data segment of the M110 - 39T signal extracted, and * represents the conjugate transpose of the matrix.

[0081] Preferably, the data segment of the M110 - 39T signal is extracted by the following method:

[0082] According to the starting time of the second part of the synchronization preamble, determine the moment corresponding to at most 1 / 10 of the code length before the end of the second - stage pre - synchronization code;

[0083] Taking this moment as the starting moment, extract data of a preset code length.

[0084] Embodiment

[0085] The first step: Construct a three - stage buffer D.

[0086] The structure of the three - stage buffer D constructed in this embodiment is as Figure 4 shown. The durations of the first stage, the second stage, and the third stage are 0.2 s, 0.5 s, and 1 s respectively, and the total length is 1.7 s.

[0087] The second step: Input the first 1.7 s of the original IQ signal into the three - stage buffer D.

[0088] The third step: Calculate the spectrum of the first 0.2 s of data in the buffer D, and statistically obtain the frequencies f1, f2, f3, f4 corresponding to the 4 peaks with the highest amplitudes, and the frequency interval between adjacent peaks needs to be greater than the preset threshold of 670 Hz.

[0089] The fourth step: Calculate the spectrum of the last 1 s of data in the buffer D, perform median filtering, and extract the frequency f5 corresponding to the maximum amplitude.

[0090] After filling the data into D, perform FFT transformation and peak detection on the first 0.2 s and the last 1 s of data respectively. For the first 0.2 s, extract the 4 peaks with the largest amplitudes, and the frequency difference between adjacent peaks needs to be greater than the preset threshold of 670 Hz, and record the frequencies f1, f2, f3, f4 corresponding to the peaks; for the last 1 s, since there are 39 data tones that lift the spectral energy, in order to effectively extract the Doppler tone peak, first perform median filtering, then extract the maximum value, and record the frequency f5 corresponding to the peak.

[0091] The fifth step: Sort f1 to f5, and calculate the frequency differences Δf1, Δf2, Δf3, Δf4 between adjacent frequencies.

[0092] The sixth step: Calculate the peak difference S.

[0093] Since the four tones (f1, f2, f3, f4) of the first - stage pre - synchronization code and the Doppler tone frequency value f5 are both determined, the signal presence detection and carrier synchronization can be completed through the values of f1 to f5. The specific method is as follows:

[0094] First, sort f1 to f5, calculate the frequency differences Δf1, Δf2, Δf3, Δf4 between adjacent frequencies, and calculate the peak difference S according to the following formula:

[0095] S = |Δf1 + Δf2 + Δf3 + Δf4 - f d - 3f * |

[0096] In this implementation, the theoretical frequency difference f d between the first frequency peak of the first - stage pre - synchronization code and the Doppler tone takes a value of 393.75Hz, and the average value f * of the theoretical frequency differences between the four peaks of the M110 - 39T first - stage pre - synchronization code takes a value of 675Hz.

[0097] The detection threshold th is set to 20. If S is less than th, it indicates that the M110 - 39T signal is detected. At the same time, the carrier frequency difference Δf = f5 - f0 can be calculated, and carrier synchronization is performed using the carrier frequency difference. f0 is the theoretical value of the multi - frequency pilot frequency, and the starting time t0 of the buffer is recorded at this time. If S is greater than or equal to th, the original data is slid backward by 0.2s, the three - segment buffer D is filled, and the detection is restarted until the signal is detected or the end of the data is reached. Figure 5 is the detection result diagram of the sliding spectrum template for the first - stage pre - synchronization code and the Doppler tone. The upper and lower figures respectively represent the spectra of the first and third segments of the three - segment buffer D. It can be seen that the special time - frequency characteristics of the signal are successfully captured.

[0098] Step 7: Extract the data containing the second - stage pre - synchronization code of the M110 - 39T signal, use a band - pass filter to filter out the ninth, 21st, and 33rd data tones, and perform sliding correlation detection using the phase time - domain template respectively to comprehensively obtain the starting time t1 of the second part of the synchronization preamble.

[0099] Step 8: Using the moment corresponding to at most 1 / 10 of the code length before the end of the second - stage pre - synchronization code as the starting time, extract the data of the preset code length, and perform symbol synchronization using the cyclic prefix sliding correlation method.

[0100] Since the time step of the detection process using the spectrum template is 0.2s, only the presence detection of the M110 - 39T signal can be realized, and accurate signal starting detection cannot be achieved. After the above - mentioned detection steps in this embodiment, the precise timing synchronization is realized by using the second - stage pre - synchronization code phase time - domain template detection and the data - segment cyclic prefix sliding correlation method respectively.

[0101] The specific implementation method of phase time-domain template detection is as follows:

[0102] Extract the data of 0.6 s starting from t0. According to the signal frame structure, the extracted data contains the second preamble code;

[0103] Construct a phase time-domain template with a length of 8 symbols and a 180° phase flip for each symbol;

[0104] Use a band-pass filter to filter out the 9th, 21st, and 33rd data tones;

[0105] Perform sliding correlation detection using the phase time-domain template respectively;

[0106] Comprehensively obtain the starting time t1 of the second part of the synchronization preamble;

[0107] The result of time-domain template detection is as Figure 6 shown. The three subgraphs are the phase change diagrams of the 9th, 21st, and 33rd tone data respectively. The dashed line is the detected phase flip position. Among them, the time corresponding to the first dashed line is t1.

[0108] The specific implementation method of data segment cyclic prefix sliding correlation is as follows:

[0109] Extract the data x N starting from t1 + 0.1785 s for 0.675 s, that is, the length of 30 symbols, and the total number of sampling points is N;

[0110] Assume that the number of signal sampling points within one symbol period is L, and the number of cyclic prefix sampling points is C. Then calculate the correlation sequence y i , where i = 1, 2,..., N - L + 1:

[0111] y i = [x i , x i+1 , …, x i+C-1 · [x i+L-C , x i+L-C+1 , …, x i+L-1 *

[0112] Sum y i by segments of L points, and extract the time delay t d corresponding to the peak point;

[0113] Obtain the starting time t2 of the reference tone according to the following formula: t2 = t1 + 0.1785 + t d .

[0114] Figure 7 ​This is a graph of the symbol synchronization result related to the cyclic prefix sliding. The horizontal axis represents the symbol number, and the vertical axis represents the correlation result. It can be seen that there are obvious correlation peaks with symbol periodicity. Therefore, by synthesizing multiple peak positions, an accurate symbol synchronization result can be obtained.

[0115] It is easy for those skilled in the art to understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention should be included within the protection scope of the present invention.

Claims

1. A detection synchronization method for M110-39T based on signal time-frequency characteristics, characterized in that, The method includes: S1. Using a frequency-domain peak template to perform a sliding search on the signal to complete signal presence detection and carrier synchronization. The frequency-domain peak template is constructed comprehensively based on the first preamble code of the M110-39T signal and the Doppler tone. S2. Using a time-domain phase template to perform a sliding search on the signal to complete coarse timing synchronization of the signal. The time-domain phase template is constructed based on the second preamble code of the M110-39T signal. S3. Adopting a cyclic prefix sliding correlation method to perform symbol synchronization on the data segment of the M110-39T signal. Step S1 specifically includes: S11. Input the starting segment of the original IQ complex signal of the M110-39T signal into a three-segment buffer. The three-segment buffer is the first segment, the second segment, and the third segment from front to back. The duration of the first segment does not exceed 2 / 3 of the duration of the first preamble code, the duration of the second segment does not exceed the sum of the duration of the first preamble code and the duration of the second preamble code, and the duration of the third segment is not less than 1 s. S12. Calculate the spectrum of the data filled in the first segment, and statistically obtain the frequencies f1, f2, f3, f4 corresponding to the 4 peaks with the highest amplitudes. The adjacent peak frequency intervals need to be greater than a preset threshold, and the preset threshold is close to the average value of the theoretical differences between the four peaks of the first preamble code of the M110-39T. S13. Calculate the spectrum of the data filled in the third segment and then filter it to extract the frequency f5 corresponding to the maximum amplitude. S14. Complete signal presence detection and carrier synchronization through the values of f1 to f5. Step S14 is specifically as follows: S141. Sort f1 to f5 and calculate the frequency differences Δf1, Δf2, Δf3, Δf4 between adjacent frequencies. S142. Calculate the peak difference S: S = |Δf1 + Δf2 + Δf3 + Δf4 - f d - 3f * | S143. Compare whether the peak difference is less than the detection threshold. If so, it indicates that the M110-39T signal is detected. Calculate the carrier frequency difference Δf = f5 - f0, and use the carrier frequency difference for carrier synchronization. Otherwise, slide the original IQ complex signal backward by the duration of the first segment, fill the three-segment buffer, and enter S12 to re-detect until the signal is detected or the data end is reached and stop. Among them, f0 is the theoretical value of the multi-frequency pilot frequency, and f d is the theoretical frequency difference between the first frequency peak of the first-stage pre-synchronization code and the Doppler tone. f * is the average value of the theoretical differences between the four peaks of the first-stage pre-synchronization code of M110-39T.

2. The method according to claim 1, wherein The filtering is median filtering.

3. The method according to claim 1, characterized in that Step S2 is specifically as follows: Extract the data containing the second preamble code of the M110-39T signal. Use a band-pass filter to filter out the 9th, 21st, and 33rd data tones. Perform sliding correlation detection using the phase time-domain template respectively. The length of the phase time-domain template is the length of the second preamble code, and the phase flips 180° per symbol. Integrate the three detection results to obtain the starting time of the second part of the synchronization preamble.

4. The method according to claim 3, wherein The extraction of the data containing the second preamble code of the M110-39T signal is specifically: extract the data of 0.6 s starting from t0, where t0 is the starting moment corresponding to the three-segment buffer when carrier synchronization is completed.

5. The method according to claim 1, characterized in that, Step S3 includes: S31. Extract the data segment x of the M110-39T signal N ; S32. Calculate the relevant sequence y i : y i = [x i , x i+1 , …, x i+C-1 · [x i+L-C , x i+L-C+1 , …, x i+L-1 * ​ S33. Sum y i Segment and sum according to point L, and extract the time delay corresponding to the peak point; S34. Extract the starting moment of the data segment superimposed with the time delay corresponding to the peak point as the starting time of the reference tone. Among them, i = 1, 2, …, N - L + 1, L is the number of signal sampling points within one symbol period, C is the number of sampling points of the cyclic prefix, N is the total number of sampling points of the data segment of the M110 - 39T signal extracted, and * represents the conjugate transpose of the matrix.

6. The method according to claim 5, wherein The data segment of the M110 - 39T signal is extracted by the following method: According to the starting time of the second part of the synchronization preamble, determine the moment corresponding to at most 1 / 10 of the code length before the end of the second pre - synchronization code; Taking this moment as the starting time, extract the data of the preset code length.

7. A detection synchronization system for M110-39T based on signal time-frequency characteristics, characterized in that, It includes a processor and a memory, The memory stores computer instructions, The processor executes the computer instructions so that the computing device executes the method described in any one of the preceding claims 1 to 6.

8. A computer-readable storage medium, characterized in that, The computer - readable storage medium stores computer program code, and when the computer program code is executed by the computing device, the computing device executes the method described in any one of the preceding claims 1 to 6.

Images