A method for determining carrier data position using linear frequency modulation header

Abstract

The present invention discloses a method for determining the position of carrier data by using a linear frequency modulation head, and belongs to the field of communication technology. The technical scheme includes the following steps: S1: The system determines the mutual correlation coefficient M in the whole process according to the received signal by using the method of mutual correlation of the previous and next code elements, and finds the position of successful coarse synchronization. S101: Determination of the minimum value of coarse synchronization; S102: Determination of the maximum value of coarse synchronization; S103: Determination of the coarse synchronization completion signal C1. S2: After the coarse synchronization completion signal C1 is valid, fine synchronization detection is started. The present invention determines the position of coarse synchronization and fine synchronization respectively, finds the accurate position of data code elements step by step, and provides support for the synchronous communication interconnection between the sender and the receiver. The synchronization method provided by the present invention can correctly parse data even when the signal-to-noise ratio is extremely low and only one synchronization code element maximum value can be found, thereby improving the reliability of the communication system.

Description

Technical Field

[0001] The present invention relates to the field of communication technology, and in particular to a method for determining a carrier data position by using a linear frequency modulation head. Background Art

[0002] Linear frequency modulation (LFM) is a signal whose instantaneous frequency changes linearly with time. Because the bandwidth it occupies is much larger than the information bandwidth, it can obtain a large system processing gain. It is widely used in radar and sonar technology. This technology can increase the communication distance, improve the average transmission power, and ensure the effective transmission of the signal. Based on this performance, using it as the receiving synchronization head of the carrier signal can increase the probability of the transmission signal being detected, thereby facilitating the detection of the entire signal.

[0003] However, when the signal-to-noise ratio is relatively low, using correlation to detect the synchronization head under linear frequency modulation signals will cause synchronization head offset problems and undetectable problems due to noise. Summary of the invention

[0004] In view of the existing problems, the present invention provides a method for detecting a linear frequency modulation synchronization head, so that a communication system can more accurately detect the starting point of a transmission signal and ensure the success of communication.

[0005] The coarse synchronization and fine synchronization described in the present invention both use the same linear frequency modulation signal. Under the condition of amplitude normalization, the code element can be expressed as follows according to the different phases: K is the linear modulation frequency in Hz / s, and t is the time variable.

[0006] After receiving a plurality of code elements continuously, whether the coarse synchronization and the fine synchronization are successful is determined based on the correlation between the code elements.

[0007] The method of the present invention comprises the following steps:

[0008] S1: The system uses the method of cross-correlation of the previous and next code elements to determine the cross-correlation coefficient M in the whole process according to the received signal, and finds the coarse synchronization success position.

[0009] S101: Determine the minimum value of coarse synchronization;

[0010] If the mutual correlation coefficient M meets the coarse synchronization minimum threshold value Cmin_th, the counter starts counting, and when a certain number requirement is met, it is determined to be the coarse synchronization minimum value Cmin.

[0011] S102: Determine the maximum value of coarse synchronization;

[0012] After the judgment in S101 is completed, the judgment continues. If the mutual correlation coefficient meets the maximum value threshold Cmax_th of the rough synchronization, the counter starts counting. When a certain number requirement is met, it is judged as the maximum value Cmax of the rough synchronization.

[0013] S103: Determination of the coarse synchronization completion signal C1;

[0014] To ensure the correctness of the maximum value of coarse synchronization, based on S102, the code element that meets the maximum value threshold of coarse synchronization Cmax_th is continuously searched in the subsequent code element. Once the counter meets a certain number requirement, it is determined as a coarse synchronization completion signal C1.

[0015] S2: After the coarse synchronization completion signal C1 is valid, fine synchronization detection begins;

[0016] S201: The next code element that enters serially starts to determine fine synchronization from this code element.

[0017] First, the data of the symbol is binarized according to the midline value to obtain b (for example, if the incoming symbol data range is 0 to 16383, the midline value is 8192). Then, the data is accumulated using the formula:

[0018]

[0019] In the formula: F is the data value of fine synchronization, A is the local fixed data, and b is the data after the input code element is binarized. F is the calculated value. Because it is serial data, there will be n F values. The maximum value will be found from F, that is, the detection of fine synchronization code element 1 will be performed.

[0020] Fine synchronization symbol 1 detection: record the maximum value m1 and the maximum value position p1 of F in the symbol;

[0021] S202: According to m1 and p1 in S201, find a value equal to the position of p1 in the current symbol, and set the position C2 where fine synchronization is successful to a high level.

[0022] Because according to actual tests, when the signal-to-noise ratio is very low, sometimes the starting position of the data codeword cannot be found, so the point after C2 is used as the starting position of the data codeword. Because the data codeword has error correction and redundancy design, data processing can be performed correctly through error correction. However, if there is no fine synchronization completion signal, the error correction of the data codeword cannot begin.

[0023] At the same time, the same calculation method as step S201 is also used to serially detect the fine synchronization symbol 2: record the maximum value m2 and the maximum position p2 of F in the symbol;

[0024] S203: Calculate the F average value m_average and the average position p_average of the maximum value according to m1 and m2;

[0025] S204: Fine synchronization symbol 3 detection:

[0026] When the real-time position P of the fine synchronization symbol 3 is less than or equal to p_average, and the value corresponding to the real-time value M is greater than 0.7 times m_average, it means that the precise position of the linear frequency modulation signal is found, and other modules of the system are reset at the same time, because C2 in S202 will start other modules of the system, and reset here, then other modules will work again and reset C3. If the above conditions are not met, repeat step S204 until the conditions are met.

[0027] If the system finds C2 or C3, it considers synchronization successful and the subsequent data is the actual carrier data.

[0028] Furthermore, the method of cross-correlating the symbols before and after step S1 is as follows:

[0029] There are 6 coarse synchronization symbols in the linear frequency modulation synchronization header, and the arrangement order of the coarse synchronization symbols is:

[0030]

[0031] The formula is:

[0032]

[0033] Where M is the mutual correlation coefficient;

[0034]

[0035] Where L is equal to the sampling length of the code element; r i Represents the sampling point at time i.

[0036] Furthermore, there are 3 fine synchronization symbols, and the arrangement order of the synchronization symbols is:

[0037] The beneficial effects of the present invention are as follows: synchronization technology is a very important technology in digital communication systems. The present invention determines the positions of coarse synchronization and fine synchronization respectively, finds the accurate positions of data symbols step by step, and provides support for synchronous communication interconnection between the sender and the receiver. The synchronization method provided by the present invention can correctly parse data even when the signal-to-noise ratio is extremely low and only one synchronization symbol maximum value can be found, thereby improving the reliability of the communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1The figure is a schematic diagram of the structure of the linear frequency modulation synchronization head according to an embodiment of the present invention.

[0039] Figure 2 The present invention is a flowchart of a method for determining a carrier data position by using a linear frequency modulation header according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The specific application of the method of the present invention is described in detail below with reference to the accompanying drawings.

[0041] The coarse synchronization and fine synchronization described in the present invention both use the same linear frequency modulation (LFM) signal. Under the condition of amplitude normalization, the code element can be expressed as follows according to the different phases: K is the linear modulation frequency in Hz / s, and t is the time variable.

[0042] After receiving a plurality of code elements continuously, whether the coarse synchronization and the fine synchronization are successful is determined based on the correlation between the code elements.

[0043] like Figure 1 As shown, the system receives 9 symbols from symbol 1 to symbol 9 in total according to time, and the corresponding linear frequency modulation signal phase is

[0044] like Figure 2 The specific process is as follows:

[0045] S1: The system uses the method of cross-correlation of previous and subsequent code elements to find the coarse synchronization success position based on the received downlink signal.

[0046] S101: Determine the minimum value of coarse synchronization;

[0047] According to the principle of S1, the correlation curve shown by the mutual correlation coefficient M is curve y, and the value range of the correlation value curve y is [-512,512]. If the mutual correlation coefficient M is less than the coarse synchronization minimum threshold Cmin_th: 512-70, the counter starts counting the number of points less than , and when the number of mutual correlation coefficients M less than the minimum threshold is greater than 8000*2, the judgment process of the coarse synchronization minimum is completed.

[0048] Selection of the value 8000: The threshold of coarse synchronization is 0.1367, 70 / 512=0.1367, calculated according to the following formula:

[0049]

[0050] Where L is the length of a code element, and the calculated result of L1 is 15824. In order to prevent false synchronization caused by field noise, the cross-correlation coefficient of coarse synchronization is appropriately extended to 8000*2.

[0051] S102: Determine the maximum value of coarse synchronization;

[0052] After the judgment in S101 is completed, the judgment continues. If the mutual correlation coefficient M is greater than the coarse synchronization maximum value threshold Cmax_th: 512+70, the counter starts counting the number of points greater than it. When the number of mutual correlation coefficients M greater than the maximum value threshold is greater than 8000, the judgment process of the coarse synchronization maximum value is completed, otherwise the judgment continues.

[0053] The value of 8000 is selected as follows: L2 = L / 2*(1-0.2734)+L / 2 = 7073. In order to adapt to noise and start position tolerance, it is set to 8000. The position that meets the maximum value is set to L / 2 in the middle of the sixth synchronization head. The remaining three synchronization heads have other functions, so the length is set to 8000 here.

[0054] S103: Determination of the coarse synchronization completion signal C1;

[0055] To ensure the accuracy of the maximum value of coarse synchronization, based on S102, continue to look for points with a cross-correlation value M greater than the coarse synchronization maximum value threshold Cmax_th within the subsequent 1 code point number (8192). If the counter count is still greater than 8000, the data point at the moment with a count value greater than 8000 is judged as the coarse synchronization completion signal C1.

[0056] S2: If the coarse synchronization completion signal C1 is valid in step S103, fine synchronization detection begins. It takes time to calculate the cross-correlation. The result of the coarse synchronization calculation process corresponds to the data code element. Figure 1 , the maximum value of the coarse synchronization is near the position of code element 6, and S103 again determines that the maximum value is greater than 8000, then the C1 completion signal is output in the 7th code element.

[0057] There are 3 fine synchronization symbols, and the order of synchronization symbols is: The corresponding code element numbers are code element 7, code element 8 and code element 9.

[0058] S201: detailed synchronization calculation and judgment;

[0059] First, the data of the symbol is binarized according to the midline value to obtain b (for example, if the incoming symbol data range is 0 to 16383, the midline value is 8192). Then, the data is accumulated using the formula:

[0060]

[0061] Where: F is the data value of fine synchronization, A is the local fixed data, and b is the data after the input codeword is binarized. F is the calculated value. Because it is serial data, there are n F values. The maximum value will be found from F, that is, 8192 points of one codeword between codeword 7 and codeword 8 are detected, and the maximum value m1 and the maximum value position p1 of F in 8192 numbers are recorded;

[0062] S202: Based on the maximum correlation value m1 and the maximum value position p1 in S201, find a value equal to the position p1 in one code element 8192 points between code elements 8 and 9, define this position as the position C2 where fine synchronization is successful, and set it to a high level.

[0063] Because according to actual tests, when the signal-to-noise ratio is very low, sometimes the starting position of the data codeword cannot be found, so the point after C2 is used as the starting position of the data codeword. Because the data codeword has error correction and redundancy, data processing can be performed correctly through error correction. However, if there is no fine synchronization completion signal, the error correction of the data codeword cannot begin.

[0064] At the same time, according to the same calculation method as step S201, the maximum value m2 and the maximum position p2 of F at one code element 8192 between code elements 8 and 9 are recorded;

[0065] S203: Calculate the F average value m_average and the average position p_average of the maximum value according to m1 and m2;

[0066] S204: fine synchronization position detection;

[0067] When the real-time position P1 of symbol 9 is less than or equal to p_average, and the value corresponding to the real-time value M1 is greater than 0.7 times m_average, it means that the precise position of the linear frequency modulation signal is found, and other modules of the system are reset at the same time, because C2 in S202 will start other modules of the system, and reset here, then other modules will work again and reset C3. If the above conditions are not met, repeat step S204 until the conditions are met.

[0068] If the system finds C2 or C3, it considers synchronization successful and the subsequent data is the actual carrier data.

[0069] Furthermore, the method of cross-correlating the symbols before and after step S1 is as follows:

[0070] There are 6 coarse synchronization symbols in the linear frequency modulation synchronization header, and the arrangement order of the coarse synchronization symbols is:

[0071]

[0072] The formula for calculating the mutual correlation coefficient is:

[0073]

[0074] Where M is the mutual correlation coefficient.

[0075]

[0076] Where L is equal to the sampling length of the code element; r i Represents the sampling point at time i.

[0077] The above formula can be understood as: Cn is the value obtained by multiplying the corresponding points of the previous code element and the next code element in terms of time, and then summing the values. Pn is the value obtained by multiplying the corresponding points inside the next code element in terms of time, and then summing the values.

[0078] The first code element can be understood as code element 1, and the second code element can be understood as code element 2. The corresponding points of these two code elements are multiplied and then added to get Cn; the second code element can be understood as code element 2. The corresponding points of this code element are multiplied and then added to get Pn. The rest of the code elements can be deduced in the same way.

[0079] 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. Ordinary technicians in the relevant field can still modify or make equivalent substitutions to the specific implementation methods of the present invention with reference to the above embodiments. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the scope of protection of the claims of the present invention to be approved.

Claims

1. A method for determining a carrier data position using a linear frequency modulation header, characterized in that: The method comprises the following steps: S1: The system uses the method of cross-correlation of the previous and next code elements to determine the cross-correlation coefficient M in the whole process according to the received signal, and finds the coarse synchronization success position; S101: Determine the minimum value of coarse synchronization; If the mutual correlation coefficient M meets the coarse synchronization minimum threshold Cmin_th, the counter starts counting, and when a certain number requirement is met, it is judged as the coarse synchronization minimum value Cmin; S102: Determine the maximum value of coarse synchronization; After the judgment in S101 is completed, the judgment continues. If the mutual correlation coefficient meets the maximum value threshold Cmax_th of the rough synchronization, the counter starts counting. When a certain number requirement is met, it is judged as the maximum value Cmax of the rough synchronization. S103: Determination of the coarse synchronization completion signal C1; To ensure the correctness of the maximum value of the coarse synchronization, based on S102, the coarse synchronization maximum value threshold Cmax_th is continued to be found in the subsequent 1 code element. Once the counter meets a certain number requirement, it is determined as a coarse synchronization completion signal C1; S2: After the coarse synchronization completion signal C1 is valid, fine synchronization detection begins; S201: the next code element that enters serially, from which fine synchronization is determined; First, the data of the code element is binarized according to the midline value to obtain b, and then the data is accumulated using the formula: Where: F is the data value of fine synchronization, A is the local fixed data, b is the data after the input codeword is binarized, and F is the calculated value. Because it is serial data entering, there will be n F values. The maximum value m1 and the maximum value position p1 of F in the codeword are recorded to complete the detection of fine synchronization codeword 1; S202: According to the maximum F value m1 and the maximum F value position p1 in S201, find a value equal to the position p1 in the current symbol, and set the position C2 where the fine synchronization is successful to a high level; When the signal-to-noise ratio is very low and the starting position of the data symbol cannot be found, the point after C2 is used as the starting position of the data symbol; At the same time, the same calculation method as step S201 is also used to serially detect the fine synchronization symbol 2: record the maximum value m2 and the maximum position p2 of F in the symbol; S203: Calculate the average value m_average of F and the average position p_average of the maximum value of F according to m1 and m2; S204: Fine synchronization symbol 3 detection: When the real-time position P of the fine synchronization symbol 3 is less than or equal to p_average, and the value corresponding to the real-time value M is greater than 0.7 times of m_average, it means that the precise position of the linear frequency modulation signal is found, and other modules of the system are reset at the same time, because C2 in S202 will start other modules of the system, and reset here, then other modules will work again and reset C3; if the above conditions are not met, repeat step S204 until the conditions are met; If the system finds C2 or C3, it considers synchronization successful and the subsequent data is the actual carrier data.

2. The method for determining the carrier data position by using a linear frequency modulation header according to claim 1, characterized in that: The coarse synchronization code element and the fine synchronization code element shown in the figure both use linear frequency modulation signals. The linear frequency modulation signal refers to a signal whose instantaneous frequency changes linearly with time. Under the condition of amplitude normalization, it can be expressed as K is the linear modulation frequency in Hz / s, and t is the time variable.

3. The method for determining the carrier data position by using a linear frequency modulation header according to claim 1, characterized in that: There are 6 coarse synchronization symbols in the linear frequency modulation synchronization header, and the arrangement order of the coarse synchronization symbols is:

4. The method for determining the carrier data position by using a linear frequency modulation header according to claim 1, characterized in that: There are 3 fine synchronization symbols, and the order of synchronization symbols is:

5. The method for determining the carrier data position by using a linear frequency modulation header according to claim 1, characterized in that: The method of cross-correlation of the symbols before and after step S1 is as follows: The formula is: Where M is the mutual correlation coefficient; Where L is equal to the sampling length of the code element; r i Represents the sampling point at time i, and the difference between the two data is L.

6. The method for determining the carrier data position by using a linear frequency modulation header according to claim 1, characterized in that: The linear frequency modulation synchronization header should have 6 coarse synchronization symbols and 3 fine synchronization symbols.

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