Method and device for synchronizing modulation index of Multi-h CPM signal

Abstract

The present invention provides a method and device for synchronizing a modulation index of a Multi‑h CPM signal, generating a 1-time symbol clock, an N-time symbol clock and a modulation index corresponding to the 1-time symbol clock for a Multi‑h CPM signal; performing maximum likelihood sequence detection on the 1-time symbol clock, the N-time symbol clock, the Multi‑h CPM signal and the modulation index to obtain first path metrics; delaying each 1-time symbol clock, the N-time symbol clock and the Multi‑h CPM signal by one symbol clock to obtain each 1-time delayed symbol clock, the N-time delayed symbol clock and the Multi‑h CPM delayed signal; performing maximum likelihood sequence detection on the 1-time delayed symbol clock, the N-time delayed symbol clock, the delayed Multi‑h CPM signal and the modulation index to obtain second path metrics; accumulating each path metric element in a first quantity group and a second quantity group to obtain a first accumulated value and a second accumulated value; and determining a modulation index synchronization state based on the first accumulated value and the second accumulated value.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a method and device for synchronizing a Multi-h CPM signal modulation index. Background Art

[0002] The traditional PCM / FM telemetry system can no longer meet the needs of modern telemetry development due to the limitations of spectrum efficiency and power efficiency. Continuous phase modulation (CPM) has high spectrum and power efficiency and is the main signal system of the new generation of telemetry systems. CPM has the advantages of continuous phase, constant envelope, and compact frequency band, so it is widely used in satellite communications and telemetry communications. According to whether the modulation index changes or not, CPM signals can be divided into single-index (Single-h CPM) signals and multi-index (Multi-h CPM) signals. The multiple different indices of the Multi-h CPM signal change cyclically in each symbol period. It not only has the advantages of general CPM signals, but also has higher spectrum utilization and better demodulation bit error rate. Therefore, it has received extensive attention and research in both military and civilian communications.

[0003] Multi-h CPM signal demodulation usually adopts coherent method, but coherent demodulation requires that the modulation parameters need to be estimated before signal demodulation. For example, the symbol period, carrier frequency, carrier phase, modulation index and other parameters need to be estimated through timing synchronization, frequency synchronization, phase synchronization and modulation index synchronization respectively. Only by accurately synchronizing the received signal can excellent demodulation performance be obtained. Among them, the modulation index is a particularly critical parameter. One of the key issues in achieving high-performance demodulation of Multi-h CPM signals is the synchronization of the modulation index.

[0004] Although some existing schemes have made improvements to the synchronization of modulation index, there are still some defects. For example, the method in the paper "Research on Modulation Index Estimation Algorithm for Multi-h CPM Signals" and patent CN114584444A separates the odd and even code elements of the signal into a single modulation index CPM signal, and then estimates each modulation index using high-order cumulants and periodic index estimation methods, thereby realizing the estimation of multiple different indexes. However, the calculation of high-order cumulants involves division operations and inverse trigonometric function operations, which makes it difficult to implement engineering through FPGA. For another example, patent CN118300951A determines whether the modulation index is correct by whether the symbol timing synchronization is successful or not. However, this method needs to meet two conditions: 1) the symbol timing synchronization cannot be locked when the modulation index is wrong; 2) the lock detection of timing synchronization is accurate; it is very complicated, and the synchronization result is not accurate enough. The above problems limit the application of modulation index synchronization of Multi-h CPM signals. Summary of the invention

[0005] The present invention provides a method and device for synchronizing a modulation index of a Multi-h CPM signal, so as to solve the technical problem that the synchronization of the modulation index of a Multi-h CPM signal cannot be simply and efficiently achieved in the prior art.

[0006] In one aspect, the present invention provides a method for synchronizing a modulation index of a Multi-h CPM signal, comprising:

[0007] For each Multi-h CPM signal, a 1x symbol clock and an Nx symbol clock are generated respectively, and at the time of generating each 1x symbol clock, a modulation index corresponding to the 1x symbol clock is generated; wherein N is an integer greater than or equal to 2;

[0008] Performing maximum likelihood sequence detection on each of the 1-time symbol clock, the N-time symbol clock, the Multi-h CPM signal, and the modulation index to obtain each first path metric;

[0009] Delaying each of the 1x symbol clock, the Nx symbol clock, and the Multi-h CPM signal by one symbol clock to obtain each of the 1x delayed symbol clock, the Nx delayed symbol clock, and the Multi-h CPM delayed signal, and performing maximum likelihood sequence detection on each of the 1x delayed symbol clock, the Nx delayed symbol clock, the Multi-h CPM delayed signal, and the modulation index to obtain each second path metric;

[0010] Divide each of the first path metrics into a plurality of first number groups, and divide each of the second path metrics into a plurality of second number groups; wherein each of the first number groups and the second number groups includes N path metric elements;

[0011] For each of the first number group and the second number group, accumulating the path metric elements in the first number group to obtain first accumulated values, and accumulating the path metric elements in the second number group to obtain second accumulated values;

[0012] Based on the magnitude relationship between each of the first accumulated values ​​and each of the second accumulated values, a synchronization state of the modulation index of the Multi-h CPM signal is determined.

[0013] According to a method for synchronizing a modulation index of a Multi-h CPM signal provided by the present invention, determining a synchronization state of the modulation index of the Multi-h CPM signal based on a magnitude relationship between each of the first accumulated values ​​and each of the second accumulated values ​​includes:

[0014] According to the corresponding relationship between the first accumulated value and the second accumulated value, comparing the magnitude relationship between the first accumulated value and the second accumulated value;

[0015] Counting is performed based on the size relationship to obtain a counting result;

[0016] A synchronization state of the modulation index is determined based on the counting result.

[0017] According to a method for synchronizing a modulation index of a Multi-h CPM signal provided by the present invention, determining a synchronization state of the modulation index based on the counting result includes:

[0018] Set two different thresholds;

[0019] Comparing the counting result with the two threshold values ​​to obtain a comparison result;

[0020] A synchronization state of the modulation index is determined based on the comparison result.

[0021] According to a method for synchronizing a modulation index of a Multi-h CPM signal provided by the present invention, two different threshold values ​​are a first preset number and a second preset number, and the second preset number is greater than the first preset number, and determining the synchronization state of the modulation index based on the comparison result includes:

[0022] When the comparison result is that the counting result is less than or equal to the first preset number, determining that the synchronization state of the modulation index is an unlocked state;

[0023] When the comparison result is that the counting result is greater than or equal to a second preset number, determining that the synchronization state of the modulation index is a synchronization state;

[0024] A modulation index is synchronized based on the loss-of-lock condition.

[0025] According to a method for synchronizing a modulation index of a Multi-h CPM signal provided by the present invention, the method for synchronizing the modulation index based on the unlocked state includes:

[0026] swapping the modulation index of the unlocked state with the modulation index of the previous generation moment;

[0027] The counting result and the synchronization state are reset.

[0028] According to a synchronization method of a Multi-h CPM signal modulation index provided by the present invention, the counting based on the size relationship includes:

[0029] When the magnitude relationship is that the first accumulated value is greater than or equal to the second accumulated value, the count is increased by 1;

[0030] When the magnitude relationship is that the first accumulated value is smaller than the second accumulated value, the count is reduced by 1.

[0031] A method for synchronizing a modulation index of a Multi-h CPM signal provided by the present invention further includes:

[0032] When the counting result is less than a third preset number, taking the third preset number as the counting result; wherein the third preset number is less than the first preset number;

[0033] When the counting result is greater than a fourth preset number, the fourth preset number is used as the counting result; wherein the fourth preset number is greater than the second preset number.

[0034] According to a method for synchronizing a modulation index of a Multi-h CPM signal provided by the present invention, performing maximum likelihood sequence detection on each of the 1-time symbol clock, the N-time symbol clock, the Multi-h CPM signal and the modulation index to obtain each first path metric includes:

[0035] The metrics of all possible paths are obtained based on the matched filter, and the largest path metric is found as the first path metric.

[0036] According to a method for synchronizing a modulation index of a Multi-h CPM signal provided by the present invention, before respectively generating a 1-time symbol clock and an N-time symbol clock for each Multi-h CPM signal, the method further includes:

[0037] Pre-processing is performed on each of the Multi-h CPM signals.

[0038] On the other hand, 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 program, it implements any of the above-mentioned methods for synchronizing the Multi-hCPM signal modulation index.

[0039] The present invention provides a method and device for synchronizing a modulation index of a Multi-h CPM signal. In this embodiment, maximum likelihood sequence detection is performed on each 1x symbol clock, Nx symbol clock, Multi-h CPM signal and modulation index to obtain each first path metric; each 1x symbol clock, Nx symbol clock and Multi-h CPM signal is delayed by one symbol clock to obtain each 1x delayed symbol clock, Nx delayed symbol clock and Multi-h CPM delayed signal, and maximum likelihood sequence detection is performed on each 1x delayed symbol clock, Nx delayed symbol clock, Multi-h CPM delayed signal and modulation index to obtain each second path metric; for each first number group and second number group, each path metric element in the first number group is accumulated to obtain each first accumulated value, and each path metric element in the second number group is accumulated to obtain each second accumulated value; based on the size relationship between each first accumulated value and each second accumulated value, the synchronization state of the modulation index of the Multi-h CPM signal is determined. The above process innovatively uses the MLSD measurement value to achieve modulation index synchronization. Specifically, the probability of accurate modulation index is measured by the accumulated value of the MLSD measurement values ​​of the signal stream and the modulation index stream, and the probability of modulation index error is measured by the accumulated value of the MLSD measurement values ​​of the signal stream and the modulation index stream after a symbol delay. By comparing the sizes of the two, it is confirmed whether the current modulation index is synchronized. This method inherits the advantages of the MLSD measurement value, has extremely high reliability, is very simple and efficient, and is easy to implement on FPGA. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] 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.

[0041] Figure 1 It is one of the flow charts of the synchronization method of the Multi-h CPM signal modulation index provided by an embodiment of the present invention;

[0042] Figure 2 This is a second flow chart of a method for synchronizing a modulation index of a Multi-h CPM signal provided in an embodiment of the present invention;

[0043] Figure 3 is a schematic diagram of the architecture of a method for synchronizing a modulation index of a Multi-h CPM signal provided by an embodiment of the present invention;

[0044] Figure 4 is a schematic diagram of the corresponding relationship between the modulation index and the accumulated value provided by an embodiment of the present invention;

[0045] Figure 5 is a schematic diagram of the robustness of the accumulated value provided by an embodiment of the present invention;

[0046] Figure 6 is a schematic diagram of bit error rate performance after modulation index synchronization provided by an embodiment of the present invention;

[0047] Figure 7 is a schematic diagram of a synchronization device for a Multi-h CPM signal modulation index provided by an embodiment of the present invention;

[0048] Figure 8 It is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0049] 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.

[0050] Figure 1 This is one of the flow diagrams of the synchronization method of the Multi-h CPM signal modulation index provided by the embodiment of the present invention. The Multi-h Continuous Phase Modulation (Multi-h CPM) system is a bandwidth-efficient modulation method that not only has a constant envelope, high spectral efficiency, low out-of-band power, but also has high coding gain, so it has been widely used in the field of aerospace telemetry.

[0051] See also Figure 1 The method for synchronizing the modulation index of a Multi-h CPM signal may include the following steps 101 to 106.

[0052] 101. For each Multi-h CPM signal, generate a 1x symbol clock and an Nx symbol clock respectively, and at the generation time of each 1x symbol clock, generate a modulation index corresponding to the 1x symbol clock.

[0053] In this step, N is an integer greater than or equal to 2. Assuming that the modulation index corresponding to the first 1x symbol clock is modulation index h1, the modulation index corresponding to the second 1x symbol clock is modulation index h2, the modulation index corresponding to the 1x symbol clock at the next moment is modulation index h1, and the modulation index corresponding to the 1x symbol clock at the next moment is modulation index h2, and so on, a modulation index set can be obtained, and the modulation index set includes each modulation index. Each modulation index can also be regarded as a modulation index stream. Each 1x symbol clock, each Nx symbol clock and Multi-h CPM signal can also be regarded as a signal stream.

[0054] The modulation index stream generated in this step can have two states: (1) synchronization state, the modulation index is correct and consistent with the modulation index corresponding to the actual signal stream; (2) unlocked state, the modulation index is wrong and the modulation index corresponding to the actual signal stream is just misaligned. When the modulation index is in the unlocked state, it is necessary to switch the modulation index and swap the current modulation index with the previous modulation index (for example, when the modulation index h2 is in the unlocked state, swap the previous modulation index h1 with the modulation index h2).

[0055] 102. Perform maximum likelihood sequence detection on each 1 times symbol clock, N times symbol clock, Multi-h CPM signal and modulation index to obtain each first path metric.

[0056] In this step, the first path metric is used to measure the probability that the current modulation index is correct. The performing of Maximum Likelihood Sequence Detection (MLSD) on each of the 1x symbol clock, the Nx symbol clock, the Multi-h CPM signal, and the modulation index to obtain each first path metric may include:

[0057] Based on the matched filter, the metrics of all possible paths are obtained, and the largest path metric is found as the first path metric. Specifically, the maximum likelihood sequence detection can be calculated according to the state transition diagram of the Multi-h CPM signal through the matched filter corresponding to each state transition path, to obtain the metrics of all possible paths and find the largest path metric as the first path metric. The advantage of this step is that it can significantly improve the accuracy and reliability of signal detection. For example, by considering all possible signal paths, MLSD can more accurately identify the most likely transmission sequence, thereby reducing the bit error rate.

[0058] 103. Delay each 1x symbol clock, Nx symbol clock, and Multi-h CPM signal by one symbol clock to obtain each 1x delayed symbol clock, Nx delayed symbol clock, and Multi-h CPM delayed signal; perform maximum likelihood sequence detection on each 1x delayed symbol clock, Nx delayed symbol clock, Multi-h CPM delayed signal, and modulation index to obtain each second path metric.

[0059] In this step, only the 1 times symbol clock, N times symbol clock and Multi-h CPM signal are delayed by one symbol clock, and the modulation index is not delayed. The method for obtaining each second path metric can refer to the method for obtaining the first path metric described above, which will not be repeated here. The second path metric is used to measure the probability that the modulation index after switching is correct.

[0060] 104. Divide each first path metric into a plurality of first number groups, and divide each second path metric into a plurality of second number groups.

[0061] In this step, each of the first number groups and the second number group includes N path metric elements. When each first path metric is divided into a plurality of first number groups, the division may be based on the order of the symbol clocks corresponding to each first path metric, rather than random division. Similarly, the division of the second number group may also be in the same manner.

[0062] 105. For each of the first number group and the second number group, accumulate the path metric elements in the first number group to obtain first accumulated values, and accumulate the path metric elements in the second number group to obtain second accumulated values.

[0063] In this step, the first accumulated value reflects the probability of accurate modulation index more stably than the first path metric. Similarly, the second accumulated value reflects the probability of wrong modulation index (lost-lock state) more stably than the second path metric.

[0064] 106. Determine a synchronization state of a modulation index of the Multi-h CPM signal based on a magnitude relationship between each first accumulated value and each second accumulated value.

[0065] In this step, the synchronization state of the modulation index of the Multi-h CPM signal can be determined based on the size relationship between each first accumulated value and each second accumulated value, which is very simple and efficient, and easy to implement in FPGA. In addition, there is no need to accurately determine whether the symbol synchronization is locked. It only takes a certain period of time to ensure that the symbol synchronization is basically converged. Based on the first accumulated value and the second accumulated value, it is possible to accurately distinguish whether the modulation index is synchronized, which avoids the possible misjudgment of the symbol synchronization lock in a noisy environment and thus interferes with the estimation of the modulation index.

[0066] In this embodiment, maximum likelihood sequence detection is performed on each 1x symbol clock, Nx symbol clock, Multi-h CPM signal and modulation index to obtain each first path metric; each 1x symbol clock, Nx symbol clock and Multi-h CPM signal is delayed by one symbol clock to obtain each 1x delayed symbol clock, Nx delayed symbol clock and Multi-h CPM delayed signal, and maximum likelihood sequence detection is performed on each 1x delayed symbol clock, Nx delayed symbol clock, Multi-h CPM delayed signal and modulation index to obtain each second path metric; for each first number group and second number group, each path metric element in the first number group is accumulated to obtain each first accumulated value, and each path metric element in the second number group is accumulated to obtain each second accumulated value; based on the size relationship between each first accumulated value and each second accumulated value, the synchronization state of the modulation index of the Multi-h CPM signal is determined. The above process innovatively uses the MLSD measurement value to achieve modulation index synchronization. Specifically, the probability of accurate modulation index is measured by the accumulated value of the MLSD measurement values ​​of the signal stream and the modulation index stream, and the probability of modulation index error is measured by the accumulated value of the MLSD measurement values ​​of the signal stream and the modulation index stream after a symbol delay. By comparing the sizes of the two, it is confirmed whether the current modulation index is synchronized. This method inherits the advantages of the MLSD measurement value, has extremely high reliability, is very simple and efficient, and is easy to implement on FPGA.

[0067] In an embodiment of the present specification, determining the synchronization state of the modulation index of the Multi-h CPM signal based on the magnitude relationship between each of the first accumulated values ​​and each of the second accumulated values ​​may include:

[0068] According to the corresponding relationship between the first accumulated value and the second accumulated value, comparing the magnitude relationship between the first accumulated value and the second accumulated value;

[0069] Counting is performed based on the size relationship to obtain a counting result;

[0070] A synchronization state of the modulation index is determined based on the counting result.

[0071] In this embodiment, by comparing the magnitude relationship between the first accumulated value and the second accumulated value, the synchronization state of the modulation index can be accurately determined, and the counting method based on the magnitude relationship simplifies the complexity of the synchronization algorithm and improves the efficiency of the algorithm. The corresponding relationship between the first accumulated value and the second accumulated value can be determined according to the symbol clock.

[0072] In an embodiment of the present specification, the counting based on the size relationship may include:

[0073] When the magnitude relationship is that the first accumulated value is greater than or equal to the second accumulated value, the count is increased by 1;

[0074] When the magnitude relationship is that the first accumulated value is smaller than the second accumulated value, the count is reduced by 1.

[0075] In this embodiment, counting can be achieved by a counter, which is very convenient.

[0076] In an embodiment of the present specification, determining the synchronization state of the modulation index based on the counting result may include:

[0077] Set two different thresholds;

[0078] Comparing the counting result with the two threshold values ​​to obtain a comparison result;

[0079] A synchronization state of the modulation index is determined based on the comparison result.

[0080] In this embodiment, a dual threshold decision method is used to determine and track the synchronization state of the current modulation index, which can adaptively and robustly track and determine changes in index synchronization. When phenomena that cause abnormal modulation index estimation errors occur, corrections can be made in a timely manner. In addition, this method is simple to implement, using only counters and comparators, and is easy to implement on FPGA.

[0081] In an embodiment of the present specification, the two different thresholds are a first preset number and a second preset number, and the second preset number is greater than the first preset number, and the determining the synchronization state of the modulation index based on the comparison result may include:

[0082] When the comparison result is that the counting result is less than or equal to the first preset number, determining that the synchronization state of the modulation index is an unlocked state;

[0083] When the comparison result is that the counting result is greater than or equal to a second preset number, determining that the synchronization state of the modulation index is a synchronization state;

[0084] A modulation index is synchronized based on the loss-of-lock condition.

[0085] In this embodiment, when the comparison result is that the counting result is less than or equal to the first preset number, the synchronization state of the modulation index is determined to be an unlocked state, and the modulation index is synchronized based on the unlocked state, which is very simple and convenient.

[0086] In an embodiment of the present specification, the synchronization modulation index based on the lost-lock state may include:

[0087] swapping the modulation index of the unlocked state with the modulation index of the previous generation moment;

[0088] The counting result and the synchronization state are reset.

[0089] In this embodiment, the modulation index of the unlocked state is exchanged with the modulation index of the previous generation time, so as to ensure the synchronization of the modulation index. The counting result and the synchronization state are reset to facilitate resynchronization of the modulation index. The initial state of the modulation index indicates a pending state. When the result is a pending state, there is no need to adjust the current modulation index. After resetting the synchronization state, the state of the modulation index is the initial state.

[0090] In an embodiment of the present specification, the method for synchronizing the modulation index of a Multi-h CPM signal may further include:

[0091] When the counting result is less than a third preset number, taking the third preset number as the counting result; wherein the third preset number is less than the first preset number;

[0092] When the counting result is greater than a fourth preset number, the fourth preset number is used as the counting result; wherein the fourth preset number is greater than the second preset number.

[0093] In this embodiment, when the counting result is less than the third preset number, the third preset number is used as the counting result, and when the counting result is greater than the fourth preset number, the fourth preset number is used as the counting result. That is, the counting result is limited, which is beneficial to eliminate some deviation data caused by interference and improve the accuracy of the judgment result.

[0094] In one embodiment of the present specification, before respectively generating a 1x symbol clock and an Nx symbol clock for each Multi-h CPM signal, the method may further include:

[0095] Pre-processing is performed on each of the Multi-h CPM signals.

[0096] In this embodiment, the pre-processing may include AGC, frequency acquisition, orthogonal down-conversion, channel equalization and other processing, and these signal processing do not need to know the modulation index of the signal.

[0097] Figure 2 FIG2 is a flow chart of the second method for synchronizing the modulation index of a Multi-h CPM signal provided by an embodiment of the present invention. Figure 2 , the synchronization method of the modulation index of Multi-h CPM signal is introduced.

[0098] Figure 2The signal in can represent the signal flow of each 1 times symbol clock, each N times symbol clock and the Multi-h CPM signal corresponding to the symbol clock, and the modulation index can represent the modulation index flow. The signal and the modulation index are input to the first maximum likelihood sequence detection module. After the signal is input to the delay module for delay processing (delayed by one symbol clock), it and the modulation index are input to the second maximum likelihood sequence detection module.

[0099] The first maximum likelihood sequence detection module performs maximum likelihood sequence detection on each 1x symbol clock, Nx symbol clock, Multi-h CPM signal and modulation index to obtain each first path metric. The second maximum likelihood sequence detection module performs maximum likelihood sequence detection on each 1x delayed symbol clock, Nx delayed symbol clock, Multi-h CPM delayed signal and modulation index to obtain each second path metric.

[0100] Each first path metric is input into a first accumulation module. Each second path metric is input into a second accumulation module. The first accumulation module selects N first path metrics as a group, adds the first path metrics of each group, and obtains each first accumulated value. The second accumulation module selects N second path metrics as a group, adds the second path metrics of each group, and obtains each second accumulated value.

[0101] The first accumulated values ​​and the second accumulated values ​​are input into the decision module for decision, and the magnitude relationship between the first accumulated values ​​and the second accumulated values ​​is compared to obtain the modulation index synchronization state.

[0102] Figure 3 Schematic diagram of the architecture of the method for synchronizing the modulation index of a Multi-h CPM signal provided by an embodiment of the present invention. Figure 3, the solid line represents the signal flow, the long dashed line represents the modulation index flow, and the short dashed line represents the synchronization state of the modulation index. The Multi-h CPM signal is input into the pre-processing module for pre-processing. The pre-processing may include processing functions such as AGC, frequency capture, orthogonal down-conversion, and channel equalization. These signal processing functions do not need to know the modulation index of the signal. The Multi-h CPM signal after pre-processing is input into the symbol synchronization module for symbol synchronization processing. Symbol synchronization uses a lead-lag loop. According to simulation, even under the condition of an incorrect modulation index, although the convergence speed of the algorithm will slow down, it can also converge to a more accurate position. The signal after symbol synchronization is input into the subsequent processing module for subsequent processing. Subsequent processing may include phase synchronization, maximum likelihood sequence detection and other processing. These processing require accurate symbol clock and modulation index information, and finally obtain bit information as demodulation output. The above main methods are all mature existing methods in Multi-h CPM signal demodulation. The modulation index synchronization method is the method provided by the present invention, that is, starting from the above step 101, it is the method provided by the present invention. The Multi-h CPM signal in step 101 is a signal after symbol synchronization is performed by a symbol synchronization module.

[0103] The present invention is further introduced through some specific examples. In order to evaluate the performance of the main innovation of the present invention, we conducted a simulation analysis, the signal adopts Multi-h CPM signal modulation, the symbol rate is 10MHz, the sampling rate is 96MHz, the intermediate frequency is 70MHz, the modulation degree is [9 / 16, 10 / 16], and the cumulative number N at each moment is 10000.

[0104] The first accumulated value s1 and the second accumulated value s2 proposed in the present invention are used to measure the performance of the modulation index correct / incorrect probability. The first accumulated value s1 may also be called the metric accumulated value s1, and the second accumulated value s2 may also be called the metric accumulated value s2. Figure 4 Among them, 4a represents the symbol synchronization convergence curve when the modulation index is correct, 4b represents the change curve of the metric accumulated value s1 and the metric accumulated value s2 when the modulation index is correct, 4c represents the symbol synchronization convergence curve when the modulation index is wrong, and 4d represents the change curve of the metric accumulated value s1 and the metric accumulated value s2 when the modulation index is wrong. Figure 4 The time-varying curves of s1 and s2 and the time-varying curves of the integral term of symbol synchronization are given in Fig. Figure 4It can be seen from the figure that: (1) after symbol synchronization converges, s1 and s2 can be clearly distinguished (the result is in line with expectations); (2) if the current modulation index is correct, the symbol synchronization converges faster, and after convergence, s1 is greater than s2 (the result is in line with expectations); (3) if the current modulation index is wrong, the symbol synchronization converges slower and the convergence accuracy is poor, but after convergence, s1 is less than s2 (the result is in line with expectations). The simulation proves that after symbol synchronization converges, it is feasible to determine whether the modulation index of the Multi-h CPM signal is accurate by obtaining the first path metric and the second path metric through two MLSDs.

[0105] Figure 5 5a represents the variation curves of s1 and s2 when Gaussian white noise exists, 5b represents the variation curves of s1 and s2 when Doppler frequency shift exists, 5c represents the variation curves of s1 and s2 when multipath fading exists, and 5d represents the variation curves of s1 and s2 when all interferences exist. Figure 5 The curves of s1 and s2 changing with time (unit: number of symbols) are given in the presence of Gaussian white noise (low signal-to-noise ratio, EbN0=2dB), Doppler frequency shift (100kHz), multipath fading (subpath energy 3dB), all interference (Gaussian white noise, frequency shift, multipath fading) and the correct modulation index. The simulation results show that this method has good resistance to Gaussian white noise, frequency shift and multipath fading.

[0106] The bit error rate performance of the present invention can be found in Figure 6 Through the simulation of a large number of symbol data (the number of simulation symbols is 1e8), the demodulation bit error rate ( Figure 6 The bit error rate of this scheme in the demodulation process), the demodulation bit error rate when the modulation index synchronization is not performed and the modulation index is wrong ( Figure 6 The bit error rate when the modulation index is wrong in the MLSD demodulation bit error rate theoretical value curve ( Figure 6 The comparison results are as follows: Figure 6 In the figure, we can see that: (1) if the modulation index is wrong and the modulation index synchronization is not performed, the demodulation bit error rate is very poor, and the telemetry task cannot be performed normally, which shows the importance of modulation index synchronization; (2) after adopting the modulation index synchronization method, the demodulation bit error rate of the signal is close to the theoretical value, which shows that the estimation of the modulation index by this scheme is correct. The bit error rate simulation results prove that the invention of this technology is meaningful and feasible.

[0107] In summary, the present invention can produce multiple beneficial effects, as shown below.

[0108] The present invention innovatively determines whether the modulation index of the current Multi-h CPM signal is accurate by using two MLSD measurement values ​​(see Figure 4, the modulation index is judged to be synchronized / unlocked by double threshold judgment. The simulation proves that this method can accurately synchronize the modulation index (see Figure 6 ).

[0109] Practicality. The key modules used in the present invention, such as metric value accumulation and threshold judgment, mainly use addition and comparison operations, which are suitable for FPGA implementation; and the modules such as the lead-lag loop and MLSD commonly used in the Multi-h CPM demodulation system are retained, with only partial modifications; the judgment process only uses one threshold value, which is easy to apply; in summary, the present invention is very practical.

[0110] Timeliness. The present invention estimates the modulation index synchronization in real time, can adaptively track changes in index synchronization, and can promptly correct errors in modulation index estimation caused by data flow interruption and other phenomena.

[0111] Anti-interference. The present invention uses the measurement value output by MLSD to synchronize the modulation index of Multi-h CPM signal, and avoids the influence of Gaussian white noise by accumulating the measurement value (see Figure 5 ); and because the MLSD metric value has good resistance to interference such as Doppler frequency shift and multipath fading, the modulation index synchronization method proposed in the present invention also breaks through the limitation of the above interference (see Figure 5 ).

[0112] Based on the same general inventive concept, the present invention also protects a synchronization device for a Multi-h CPM signal modulation index, such as Figure 7 As shown, Figure 7 Schematic diagram of a synchronization device for a Multi-h CPM signal modulation index provided by an embodiment of the present invention. The following describes a synchronization device for a Multi-h CPM signal modulation index provided by the present invention. The synchronization device for a Multi-h CPM signal modulation index described below and the synchronization method for a Multi-h CPM signal modulation index described above can be referred to each other. The synchronization device includes:

[0113] The symbol clock generating module 701 is used to generate a 1x symbol clock and an Nx symbol clock for each Multi-h CPM signal, and generate a modulation index corresponding to the 1x symbol clock at the time of generating each 1x symbol clock; wherein N is an integer greater than or equal to 2;

[0114] A first maximum likelihood sequence detection module 702, configured to perform maximum likelihood sequence detection on each of the 1-time symbol clock, the N-time symbol clock, the Multi-h CPM signal, and the modulation index to obtain each first path metric;

[0115] The second maximum likelihood sequence detection module 703 is used to delay each 1 times symbol clock, N times symbol clock, and Multi-h CPM signal by one symbol clock to obtain each 1 times delayed symbol clock, N times delayed symbol clock, and Multi-h CPM delayed signal, and perform maximum likelihood sequence detection on each of the 1 times delayed symbol clock, the N times delayed symbol clock, the Multi-h CPM delayed signal, and the modulation index to obtain each second path metric;

[0116] A grouping module 704 is used to divide each of the first path metrics into a plurality of first number groups, and divide each of the second path metrics into a plurality of second number groups; wherein each of the first number groups and the second number groups includes N path metric elements;

[0117] An accumulation module 705 is used for accumulating the path metric elements in the first number group and the second number group to obtain first accumulated values, and accumulating the path metric elements in the second number group to obtain second accumulated values;

[0118] The synchronization module 706 is used to determine the synchronization state of the modulation index of the Multi-h CPM signal based on the size relationship between each of the first accumulated values ​​and each of the second accumulated values.

[0119] Figure 8 It is a schematic diagram of the structure of an electronic device provided by an embodiment of the present invention.

[0120] like Figure 8 As shown, the electronic device may include: a processor 810, a communication interface 820, a memory 830 and a communication bus 840, wherein the processor 810, the communication interface 820 and the memory 830 communicate with each other through the communication bus 840. The processor 810 may call the logic instructions in the memory 830 to execute the synchronization method of the Multi-h CPM signal modulation index.

[0121] In addition, the logic instructions in the above-mentioned memory 830 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 this understanding, the technical solution of the present invention is essentially 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 to enable 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 and other media that can store program codes.

[0122] 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 synchronization method of the Multi-h CPM signal modulation index provided by the above methods.

[0123] In yet another aspect, the present invention further provides a non-transitory computer-readable storage medium having a computer program stored thereon, which is implemented when the computer program is executed by a processor to execute the method for synchronizing the modulation index of a Multi-h CPM signal provided by the above methods.

[0124] 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.

[0125] 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.

[0126] 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 method for synchronizing a modulation index of a Multi-h CPM signal, characterized in that: include: For each Multi-h CPM signal, a 1x symbol clock and an Nx symbol clock are generated respectively, and at the time of generating each 1x symbol clock, a modulation index corresponding to the 1x symbol clock is generated; wherein N is an integer greater than or equal to 2; Performing maximum likelihood sequence detection on each of the 1-time symbol clock, the N-time symbol clock, the Multi-h CPM signal, and the modulation index to obtain each first path metric; Delaying each of the 1x symbol clock, the Nx symbol clock, and the Multi-h CPM signal by one symbol clock to obtain each of the 1x delayed symbol clock, the Nx delayed symbol clock, and the Multi-h CPM delayed signal, and performing maximum likelihood sequence detection on each of the 1x delayed symbol clock, the Nx delayed symbol clock, the Multi-h CPM delayed signal, and the modulation index to obtain each second path metric; Divide each of the first path metrics into a plurality of first number groups, and divide each of the second path metrics into a plurality of second number groups; wherein each of the first number groups and the second number groups includes N path metric elements; For each of the first number group and the second number group, accumulating the path metric elements in the first number group to obtain first accumulated values, and accumulating the path metric elements in the second number group to obtain second accumulated values; Determining a synchronization state of a modulation index of a Multi-h CPM signal based on a magnitude relationship between each of the first accumulated values ​​and each of the second accumulated values; Wherein, determining the synchronization state of the modulation index of the Multi-hCPM signal based on the magnitude relationship between each of the first accumulated values ​​and each of the second accumulated values ​​includes: According to the corresponding relationship between the first accumulated value and the second accumulated value, comparing the magnitude relationship between the first accumulated value and the second accumulated value; Counting is performed based on the size relationship to obtain a counting result; Determining a synchronization state of a modulation index based on the counting result; The determining the synchronization state of the modulation index based on the counting result comprises: Set two different thresholds; Comparing the counting result with the two threshold values ​​to obtain a comparison result; A synchronization state of the modulation index is determined based on the comparison result.

2. The method for synchronizing the modulation index of a Multi-h CPM signal according to claim 1, characterized in that: The two different thresholds are a first preset number and a second preset number, and the second preset number is greater than the first preset number, and the determining the synchronization state of the modulation index based on the comparison result includes: When the comparison result is that the counting result is less than or equal to the first preset number, determining that the synchronization state of the modulation index is an unlocked state; When the comparison result is that the counting result is greater than or equal to a second preset number, determining that the synchronization state of the modulation index is a synchronization state; A modulation index is synchronized based on the loss-of-lock condition.

3. The method for synchronizing the modulation index of a Multi-h CPM signal according to claim 2, characterized in that: The synchronization modulation index based on the unlocked state includes: swapping the modulation index of the unlocked state with the modulation index of the previous generation moment; The counting result and the synchronization state are reset.

4. The method for synchronizing the modulation index of a Multi-h CPM signal according to claim 1, characterized in that: The counting based on the size relationship includes: When the magnitude relationship is that the first accumulated value is greater than or equal to the second accumulated value, the count is increased by 1; When the magnitude relationship is that the first accumulated value is smaller than the second accumulated value, the count is reduced by 1.

5. The method for synchronizing the modulation index of a Multi-h CPM signal according to claim 2, characterized in that: Also includes: When the counting result is less than a third preset number, taking the third preset number as the counting result; wherein the third preset number is less than the first preset number; When the counting result is greater than a fourth preset number, the fourth preset number is used as the counting result; wherein the fourth preset number is greater than the second preset number.

6. The method for synchronizing the modulation index of a Multi-h CPM signal according to claim 1, characterized in that: The performing maximum likelihood sequence detection on each of the 1-time symbol clock, the N-time symbol clock, the Multi-h CPM signal, and the modulation index to obtain each first path metric includes: The metrics of all possible paths are obtained based on the matched filter, and the largest path metric is found as the first path metric.

7. The method for synchronizing the modulation index of a Multi-h CPM signal according to claim 1, characterized in that: Before respectively generating a 1-time symbol clock and an N-time symbol clock for each Multi-h CPM signal, the method further includes: Pre-processing is performed on each of the Multi-h CPM signals.

8. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the program, the method for synchronizing the modulation index of the Multi-h CPM signal as described in any one of claims 1 to 7 is implemented.

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