Pseudo-code synchronization method and device for multi-level threshold comparison in drone-satellite communication

Abstract

The present application provides a pseudo-code synchronization method and device for multi-level threshold comparison in drone-satellite communication, which relates to the field of communication technologies. The method includes: receiving a direct-sequence spread spectrum signal sent by a transmitting end; performing correlation processing on the direct-sequence spread spectrum signal and a current local pseudo-code to obtain a current correlation peak point; scalar-summing the amplitudes of several adjacent current correlation peak points to obtain a current summation amplitude; comparing the current summation amplitudes obtained continuously for multiple times with the capture thresholds of corresponding levels respectively. If the current summation amplitudes obtained continuously for multiple times are all greater than the capture thresholds of corresponding levels, adjusting the phase of the current local pseudo-code in a fixed direction and with a fixed step size to obtain a coarsely synchronized pseudo-code; and performing tracking processing on the coarsely synchronized pseudo-code to obtain a finely synchronized pseudo-code. It can avoid the situation where a single correlation peak point jumps due to noise and multipath interference and exceeds the threshold detection value, effectively reduce the false alarm probability, and achieve accurate pseudo-code synchronization.

Description

Technical Field

[0001] This application relates to the field of communication technologies, and particularly to a pseudo-code synchronization method and device for multi-level threshold comparison in UAV-satellite communication. Background Art

[0002] The spread spectrum technology is an information transmission and processing technology. By expanding the spectrum of the transmitted signal, the way to achieve spectrum expansion is to multiply a pseudo-code sequence with a very high frequency in the time domain by an information code sequence with a relatively low rate, so that the bandwidth after convolution of the information code that originally occupies a very narrow region in the frequency domain will become the sum of the information code bandwidth and the pseudo-code bandwidth, thus the spectrum is greatly expanded. The theoretical basis of spread spectrum communication is the Shannon theorem channel capacity formula. When the channel capacity remains unchanged, increasing the corresponding signal bandwidth can still maintain reliable communication at a lower signal-to-noise ratio. Therefore, the spread spectrum technology has the characteristics of strong anti-interference, good concealment, easy implementation of code division multiple access, and anti-multipath, making the spread spectrum technology play a significant role in deep space ultra-long-distance communication engineering.

[0003] In a real-time spread spectrum communication system, synchronization has always been the most concerned link. The difficulty of the spread spectrum technology lies in how to determine whether the local pseudo-code is synchronized with the received pseudo-code. Pseudo-code synchronization is to determine the start and end moments of each code element at the receiving end and perform code element decision. Since the digital sequence sent in digital communication is transmitted bit by bit at a certain rate, it is required to receive bit by bit at the same rate at the receiving end, which requires the same bit rate at both the transmitting and receiving ends to recover the original digital sequence.

[0004] The most widely used spread spectrum communication system is the direct sequence spread spectrum (DSSS) system. The DSSS system is a direct sequence spread spectrum communication system that directly multiplies a pseudo-code with an information code. At the receiving end of the DSSS system, pseudo-code synchronization includes two processes: acquisition and tracking. Adjust the code phase of the local pseudo-code so that the difference between the received pseudo-code phase and the local pseudo-code phase is less than one chip, thereby achieving coarse synchronization of the received pseudo-code and the local pseudo-code. Tracking means that on the basis of acquisition, further operations and adjustments are performed on the input signal to further reduce the phase difference between the local reference code and the received code. Usually, a phase-locked loop, a frequency-locked loop, etc. are used to achieve precise synchronization of the code phase, which is called fine synchronization. Pseudo-code acquisition is the premise of pseudo-code tracking. Therefore, in the spread spectrum technology, the fast acquisition of direct spread signals is a key issue.

[0005] In the existing direct sequence spread spectrum (DS - SS) system, to implement the despreading step of the DS - SS signal, it is necessary to reproduce the same code phase and code clock at the receiving end as those at the transmitting end. Therefore, the sliding correlation method is often used to achieve synchronization. The correlation value is obtained by multiplying and integrating the local pseudo - code with the pseudo - code in the DS - SS signal. Through threshold detection, it is compared whether a useful signal is captured. When there is noise and multipath interference, the correlation value obtained by the operation will jump suddenly beyond the threshold detection value, resulting in a high false alarm probability and unable to achieve accurate capture. Since capture is the premise of tracking, subsequent tracking cannot be accurately realized either, making it difficult for the receiving end to accurately achieve pseudo - code synchronization. Summary of the Invention

[0006] This application provides a pseudo - code synchronization method and device for multi - level threshold comparison in UAV - satellite communication. By obtaining the superimposed amplitude obtained by superimposing multiple adjacent correlation peak points and then comparing it with multi - level capture thresholds respectively, it can avoid a single correlation peak point from jumping suddenly beyond the threshold detection value due to noise and multipath interference, reduce the false alarm probability, achieve accurate capture, and then achieve accurate pseudo - code synchronization.

[0007] In a first aspect, this application provides a pseudo - code synchronization method for multi - level threshold comparison in UAV - satellite communication, which is applied to a pseudo - code loop. The method includes:

[0008] Receiving the DS - SS signal sent by the transmitting end;

[0009] Performing correlation processing on the DS - SS signal and the current local pseudo - code to obtain the current correlation peak point;

[0010] Scalar - adding the amplitudes of several adjacent current correlation peak points to obtain the current superimposed amplitude;

[0011] Comparing the current superimposed amplitudes obtained continuously for multiple times with the capture thresholds of the corresponding levels respectively. If the current superimposed amplitudes obtained continuously for multiple times are all greater than the capture thresholds of the corresponding levels, adjust the phase of the current local pseudo - code in a fixed direction and with a fixed step size to obtain a roughly synchronized pseudo - code;

[0012] Performing tracking processing on the roughly synchronized pseudo - code to obtain a finely synchronized pseudo - code.

[0013] Through the above technical solutions, the scalar superposition of noise in the correlation peak points will not increase the amplitude value of the current superimposed amplitude, while the superposition of peaks will increase the amplitude value of the current superimposed amplitude. Therefore, superposition can effectively improve the anti - noise performance of the system; since the true correlation peaks increase proportionally, multi - level threshold comparison can reduce the probability of false alarms caused by the sudden jump of the current correlation peak point, thus achieving accurate capture, and then accurate pseudo - code capture can be realized.

[0014] Optionally, the process of tracking the coarse synchronization pseudo-code to obtain the fine synchronization pseudo-code includes:

[0015] Performing correlation processing on the direct-sequence spread signal with the early local pseudo-code and the late local pseudo-code respectively to obtain an early correlation peak point and a late correlation peak point;

[0016] Scalar-summing the amplitudes of several adjacent early correlation peak points to obtain an early superposition amplitude, and scalar-summing the amplitudes of several adjacent late correlation peak points to obtain a late superposition amplitude;

[0017] Calculating the code phase increment between the coarse synchronization pseudo-code and the direct-sequence spread signal according to the early superposition amplitude and the late superposition amplitude;

[0018] Modulating the phase of the coarse synchronization pseudo-code based on the code phase increment until the current local pseudo-code is code-synchronized with the pseudo-code sequence at the transmitting end to obtain the fine synchronization pseudo-code.

[0019] Through the above technical solution, scalar-summing processing is also performed on the early correlation peak point and the late correlation peak point, and the code phase increment between the coarse synchronization pseudo-code and the direct-sequence spread signal is calculated. The phase of the local pseudo-code is adjusted by the code phase increment to achieve code synchronization with the pseudo-code sequence at the transmitting end. It can further track and correct the local pseudo-code after capture, and at the same time perform superposition processing on the early correlation peak and the late correlation peak, making the calculation of the code phase increment more accurate, reducing the number of tracking adjustments, and improving the tracking efficiency.

[0020] Optionally, the capture threshold includes a first-stage capture threshold, a second-stage capture threshold, and a third-stage capture threshold, the first-stage capture threshold is less than the second-stage capture threshold, and the second-stage capture threshold is less than the third-stage capture threshold.

[0021] Through the above calculation scheme, in real-time correlation peak detection, the situation of detecting the correlation peak is from detecting the flat correlation peak point to the prominent correlation peak point. Therefore, the amplitude of the correlation peak point gradually increases during the capture process. Designing a three-stage capture threshold that gradually increases can avoid misjudging the peak value.

[0022] Optionally, before performing correlation processing on the direct-sequence spread signal with the early local pseudo-code and the late local pseudo-code respectively to obtain the early correlation peak point and the late correlation peak point, it further includes:

[0023] Filtering the direct-sequence spread signal transmitted by the transmitting end using a filter;

[0024] If the filter is a root raised cosine filter, determine the number of superimposed leading correlation peak points and the number of superimposed lagging correlation peak points as [IPOINT, 2*IPOINT], where the value of IPOINT is the oversampling multiple of the direct sequence spread spectrum signal;

[0025] If the filter is a low-pass filter, determine the number of superimposed leading correlation peak points and the number of superimposed lagging correlation peak points as [IPOINT / 2, IPOINT], where the value of IPOINT is the oversampling multiple of the direct sequence spread spectrum signal.

[0026] Through the above technical solution, in a direct sequence spread spectrum system, at the receiving end, a root raised cosine filter or a low-pass filter is often used to filter the received direct sequence spread spectrum signal. Since the power distribution of the code correlation peak after low-pass filtering is narrow and high, the number of superimposed correlation peak points is relatively in a small range, while the power distribution of the code correlation peak of the root raised cosine filter is wide and flat, so the number of superimposed correlation peak points can be appropriately more. Select an appropriate number of superimposed correlation peak points to quickly achieve pseudo-code synchronization.

[0027] Optionally, the leading local pseudo-code is obtained by shifting the current local pseudo-code forward by half of the spreading code length, and the lagging local pseudo-code is obtained by delaying the current local pseudo-code by half of the spreading code length; the half of the spreading code length is calculated based on the oversampling multiple of the direct sequence spread spectrum signal.

[0028] Through the above technical solution, every time the current pseudo-code signal is adjusted, the leading pseudo-code signal and the lagging pseudo-code signal need to be adjusted accordingly, and the adjustment length is half of the spreading code length.

[0029] Optionally, calculating the code phase increment between the coarse synchronization pseudo-code and the direct sequence spread spectrum signal according to the leading superposition amplitude and the lagging superposition amplitude includes:

[0030] Keep the current superposition amplitude as the highest amplitude, perform a difference operation and code loop filtering on the leading superposition amplitude and the lagging superposition amplitude to obtain the code phase increment between the coarse synchronization pseudo-code and the direct sequence spread spectrum signal.

[0031] Through the above technical solution, when keeping the current correlation peak point the highest, calculate the code phase increment from the leading superposition amplitude and the lagging superposition amplitude, and make corresponding phase adjustments to the current local pseudo-code according to the code phase increment, which can reduce the number of adjustments during the tracking process.

[0032] Optionally, the fixed step size is between 1 / 8 length and 1 / 2 length of one chip.

[0033] Through the above technical solution, the key in the capture stage is to quickly detect the direct-sequence spread spectrum signal. Therefore, the adjustment step size of the current local pseudo-code is relatively large. The 1 / 8 length of one chip is determined by the sampling point rate. At the same time, if the adjusted length exceeds 1 / 2 length of one chip, it will cause the detection of relevant peaks to be missed.

[0034] In a second aspect, the present application provides a pseudo-code synchronization device for multi-level threshold comparison in drone-satellite communication, which is applied to a pseudo-code loop. The device includes:

[0035] A direct-sequence spread spectrum signal receiving module, configured to receive the direct-sequence spread spectrum signal sent by a transmitting end;

[0036] A relevant peak point generating module, configured to perform correlation processing on the direct-sequence spread spectrum signal and the current local pseudo-code to obtain a current relevant peak point;

[0037] A relevant peak point superposition module, configured to scalar-superpose the amplitudes of several adjacent current relevant peak points to obtain a current superposition amplitude;

[0038] A coarse synchronization pseudo-code capture module, configured to compare the current superposition amplitudes obtained continuously for multiple times with the capture thresholds of corresponding levels respectively. If the current superposition amplitudes obtained continuously for multiple times are all greater than the capture thresholds of corresponding levels, adjust the phase of the current local pseudo-code in a fixed direction and with a fixed step size to obtain a coarse synchronization pseudo-code;

[0039] A fine synchronization pseudo-code tracking module, configured to perform tracking processing on the coarse synchronization pseudo-code to obtain a fine synchronization pseudo-code.

[0040] In a third aspect, the present application provides an electronic device, including a processor, a memory, a user interface, and a network interface. The memory is used to store instructions, the user interface and the network interface are used to communicate with other devices, and the processor is used to execute the instructions stored in the memory so that the electronic device executes the above method.

[0041] In a fourth aspect, the present application provides a computer storage medium, which stores multiple instructions, and the instructions are suitable for being loaded and executed by a processor to execute the above method.

[0042] In summary, the beneficial effects brought by the technical solution provided by the present application are as follows:

[0043] By performing correlation processing on the received direct-sequence spread spectrum (DSSS) signal and the current local pseudo-code, multiple real-time correlation peak points are obtained. The amplitudes of adjacent correlation peak points are scalarly superimposed, and then the continuously superimposed amplitudes for multiple times are respectively compared with the capture thresholds at corresponding levels. The phase of the local pseudo-code is adjusted to achieve pseudo-code capture, and the fine-synchronized pseudo-code is obtained through tracking processing. By superimposing multiple correlation peak points, the interference of noise on pseudo-code capture can be effectively reduced, the false alarm probability can be decreased. At the same time, by setting multiple levels of thresholds to judge the continuously superimposed correlation peak points, the jumps of correlation peak points that are relatively close to each other can be identified, the capture interference caused by jumps can be avoided, and the probability of false detection and missed detection during the capture process can be reduced, making the capture more accurate, and thus pseudo-code synchronization can be accurately achieved. Description of the Drawings

[0044] Figure 1 It is a schematic structural diagram of a transceiver model of a DSSS system according to an embodiment of the present application;

[0045] Figure 2 It is a schematic flowchart of a pseudo-code synchronization method with multi-level threshold comparison in UAV-satellite communication according to an embodiment of the present application;

[0046] Figure 3 It is a sampling schematic diagram of the superposition of correlation peak points according to an embodiment of the present application;

[0047] Figure 4 It is a comparison schematic diagram of the multi-point superposition amplitude and the single-point amplitude of correlation peak points under high signal-to-noise ratio according to an embodiment of the present application;

[0048] Figure 5 It is a comparison schematic diagram of the multi-point superposition amplitude and the single-point amplitude of correlation peak points under low signal-to-noise ratio according to an embodiment of the present application;

[0049] Figure 6 It is a schematic structural diagram of a code loop tracking according to an embodiment of the present application;

[0050] Figure 7 It is a schematic structural diagram of a pseudo-code synchronization device with multi-level threshold comparison in UAV-satellite communication according to an embodiment of the present application;

[0051] Figure 8 It is a schematic structural diagram of an electronic device provided by an embodiment of the present application.

[0052] Description of the reference numerals: 100, DSSS signal receiving module; 200, correlation peak point generating module; 300, correlation peak point superposition module; 400, coarse synchronization pseudo-code capture module; 500, fine synchronization pseudo-code tracking module; 1000, electronic device; 1001, processor; 1002, communication bus; 1003, user interface; 1004, network interface; 1005, memory. Detailed implementation manners

[0053] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this specification. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments.

[0054] In the description of the embodiments of this application, words such as "exemplary", "for example" or "for illustration" are used to indicate examples, illustrations or explanations. Any embodiment or design solution described as "exemplary", "for example" or "for illustration" in the embodiments of this application should not be construed as being more preferred or having more advantages than other embodiments or design solutions. Rather, the words "exemplary", "for example" or "for illustration" are used to present relevant concepts in a specific manner.

[0055] In the description of the embodiments of this application, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly indicating the technical features indicated. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. The terms "include", "comprise", "have" and their variants all mean "include but not limited to", unless otherwise specifically emphasized in other ways.

[0056] First, a brief introduction to the application scenario of this application is given. Please refer to Figure 1 , which is a schematic structural diagram of a direct-sequence spread-spectrum (DS) system transceiver model provided by the embodiments of this application. In this implementation environment, the data source after source coding at the transmitter is multiplied by the pseudo-random code sequence generated by a high-speed clock, and the resulting structure is modulated by a carrier and then transmitted by the transmitter. Compared with ordinary signal transmission, the spectrum of the DS signal is greatly expanded, so it can be applied to satellite communication over deep space and ultra-long distances.

[0057] The difficulty in receiving and processing signals at the receiver lies in the fact that a pseudo-random code sequence exactly the same as that at the transmitter must be generated in order to perform corresponding despreading processing on the DS signal. The key point in the despreading process is pseudo-random code synchronization. Pseudo-random code synchronization is divided into two processes: acquisition and tracking, which respectively achieve coarse synchronization and fine synchronization of the pseudo-random code to obtain a pseudo-random code sequence exactly the same as that at the transmitter, so as to complete the subsequent demodulation and recovery of data.

[0058] The technical solution provided by this application lies in the process of achieving pseudo-random code synchronization at the receiver. Therefore, it can be applied to most receivers in the DS system. At the same time, since the technical solution provided by this application only involves the reception and processing of signals, it can also be applied to the processing of most DS signals in the DS system.

[0059] Please refer to Figure 2, which is a schematic flowchart of a pseudo-code synchronization method for multi-level threshold comparison in UAV-satellite communication provided by an embodiment of this application. This method can be implemented relying on a computer program, can be implemented relying on a single-chip microcomputer, or can run on a pseudo-code synchronization device for multi-level threshold comparison in UAV-satellite communication based on the von Neumann architecture. This computer program can be integrated into an application or run as an independent tool-type application. Taking a computer device as an example, an embodiment of this application details the specific steps of the pseudo-code synchronization method for multi-level threshold comparison in UAV-satellite communication.

[0060] S101, Receive the direct-sequence spread spectrum signal sent by the transmitting end.

[0061] The direct-sequence spread spectrum signal is a type of spread spectrum signal in spread spectrum communication, which is directly modulated by a pseudo-code sequence and an information code. The modulation methods of direct-sequence spread spectrum systems usually adopt modulation methods such as BPSK, DPSK, QPSK, and MPSK. Since the direct-sequence spread spectrum signal is spread over a very wide frequency band and the signal power spectral density is very low, the signal will be submerged in white noise. Without knowing the pseudo-code, it is very difficult to intercept useful signals. Therefore, a spread spectrum receiver is needed to receive the direct-sequence spread spectrum signal.

[0062] S102, Perform correlation processing on the direct-sequence spread spectrum signal and the current local pseudo-code to obtain the current correlation peak point.

[0063] The pseudo-code is a binary number sequence with good autocorrelation characteristics. One bit of information stream is transmitted through multiple chips of the pseudo-code. Therefore, the processed bandwidth is wider and it is often used in satellite communication. In the Global Positioning System (GPS), the signal structure is at the second level above the carrier. GPS is fundamentally a spread spectrum communication system based on Code Division Multiple Access (CDMA), where the codes are different pseudo-random codes to distinguish different base stations. Only by using the same pseudo-random code as the transmitting base station can the information code at the transmitting end be restored. The current local pseudo-code is a pre-stored or received pseudo-code sequence synchronized with the local clock.

[0064] Multiply the received direct-sequence spread spectrum signal by the current local pseudo-code and perform integration processing to obtain several current correlation peak points, that is, use Fourier transform to restore the frequency components in the signal and analyze the amplitudes and phases of different frequency components. The amplitudes of several correlation peak points in the time domain represent the correlation between the current local pseudo-code and the direct-sequence spread spectrum signal, that is, the correlation between the current local pseudo-code and the spread spectrum code in the direct-sequence spread spectrum signal. The higher the amplitude of the correlation peak point, the smaller the corresponding phase difference between the current local pseudo-code and the spread spectrum code in the direct-sequence spread spectrum signal.

[0065] S103, Scalar-sum the amplitudes of several adjacent current correlation peak points to obtain the current superimposed amplitude.

[0066] Please refer to Figure 3 , which is a sampling schematic diagram of superimposing relevant peak points provided by an embodiment of the present application.

[0067] Scalar superposition is performed on several current relevant peak points. Superimposing several adjacent current relevant peak points obtains the current superimposed amplitude, and the number of current superimposed amplitudes is also several. For noise, scalar superposition does not increase the amplitude, while for relevant peaks, the amplitude will be significantly increased, which can reduce the influence of noise on the misjudgment of relevant peaks. For example, there are adjacent relevant peak points A, B, C, D, E, F, G, and H, and the number of superimposed points is 4. Therefore, the superimposing methods of relevant peak points can be divided into three groups: ABCD, CDEF, and EFGH, or five groups: ABCD, BCDE, CDEF, DEFG, and EFGH. The first superimposing method has a fast response speed, and the second superimposing method has high superimposing accuracy. At the same time, the number of superimposed points can also be adjusted. Therefore, the number of superimposed adjacent relevant peak points and the superimposing method can be adjusted according to the actual situation to obtain appropriate superimposing parameters of relevant peak points.

[0068] Please refer to Figure 4 , which is a comparison schematic diagram of the multi-point superimposed amplitude and the single-point amplitude of relevant peak points provided by an embodiment of the present application under high signal-to-noise ratio.

[0069] In the figure, compared with the single-point amplitude, the amplitude range of the relevant peak points after multi-point superimposition is significantly smaller, and the fluctuation of the relevant peak points is significantly reduced. When comparing the subsequent relevant peak points with the threshold, the influence of the fluctuation of the relevant peak points on the pseudo-code acquisition can be reduced.

[0070] Please refer to Figure 5 , which is a comparison schematic diagram of the multi-point superimposed amplitude and the single-room amplitude of relevant peak points provided by an embodiment of the present application under low signal-to-noise ratio.

[0071] Low signal-to-noise ratio means that the noise in the direct-sequence spread spectrum signal is large. At this time, the signal quality is low, the signal amplitude fluctuates greatly, and the amplitude fluctuation reflected on the relevant peak points is also relatively large. It can be known from the figure that compared with the single-point amplitude range, the amplitude integration effect after multi-point superimposition is more obvious, and the probability of false alarm caused by the fluctuation of relevant peak points is smaller.

[0072] S104. Compare the currently obtained superimposed amplitudes obtained continuously for multiple times with the capture thresholds of corresponding levels respectively. If the currently obtained superimposed amplitudes obtained continuously for multiple times are all greater than the capture thresholds of corresponding levels, adjust the phase of the current local pseudo-code in a fixed direction and at a fixed step size to obtain a roughly synchronized pseudo-code.

[0073] The acquisition threshold is set based on the amplitude standard of the correlation peak point in the pseudo-code synchronization process. When the current superimposed amplitude reaches the acquisition threshold, it indicates that the current local pseudo-code has a large correlation with the direct-sequence spread-spectrum signal pseudo-code and a high synchronization rate.

[0074] For continuous current superimposed amplitudes, multiple levels of acquisition thresholds are set. When a certain current superimposed amplitude exceeds the acquisition threshold, it is not directly determined that the acquisition is successful. Instead, the next adjacent current superimposed amplitude is continuously compared with another acquisition threshold to avoid the situation where a certain current superimposed amplitude exceeds the acquisition threshold only due to a sudden jump, resulting in false acquisition. Because when the maximum value of the true correlation peak point is captured, the amplitude of the correlation peak point increases in a certain proportion. Therefore, when a certain current superimposed amplitude exceeds the acquisition threshold, on the premise that the next adjacent current superimposed amplitude is greater than the acquisition threshold, it should also have the condition of being greater than the previous superimposed amplitude. For example, in the case where the current superimposed amplitudes are accidentally continuous twice and exceed the acquisition threshold, but do not show an increasing trend of the superimposed amplitude when the maximum value of the correlation peak point is captured, false judgment of pseudo-code acquisition is avoided.

[0075] In a possible implementation manner, the acquisition threshold includes a first-level acquisition threshold, a second-level acquisition threshold, and a third-level acquisition threshold, where the first-level acquisition threshold is less than the second-level acquisition threshold, and the second-level acquisition threshold is less than the third-level acquisition threshold.

[0076] Continuously increasing first-level, second-level, and third-level acquisition thresholds are set for the current superimposed amplitudes for three consecutive times. When the first current superimposed amplitude is greater than the first acquisition threshold, it is judged whether the second current superimposed amplitude is greater than the second acquisition threshold, and then whether the third current superimposed amplitude is greater than the third acquisition threshold, so as to avoid peak misjudgment caused by noise and multipath interference and ensure that the true synchronization point is captured.

[0077] In a possible implementation manner, the fixed step size is between 1 / 8 and 1 / 2 of the length of one chip.

[0078] After the correlation peak point is captured and exceeds the multiple-level acquisition threshold, the current local pseudo-code is adjusted. At this time, the adjustment is a single adjustment. The adjustment direction is determined according to the maximum value of the correlation peak point. The step size of the pseudo-code phase is set to be greater than 1 / 8 of the length of one chip, which can ensure the acquisition speed. The step size is set to be less than 1 / 2 of the length of one chip, which can ensure that the detection of the correlation peak is not missed. After the large-step adjustment of the local pseudo-code, the initial synchronization pseudo-code is obtained.

[0079] S105, perform tracking processing on the coarse synchronization pseudo-code to obtain the fine synchronization pseudo-code.

[0080] Please refer to Figure 6 , which is a schematic structural diagram of a code loop tracking provided by an embodiment of the present application.

[0081] In a possible implementation, the direct-sequence spread spectrum (DSSS) signal is correlated with the early local pseudo-code and the late local pseudo-code respectively to obtain the early correlation peak point and the late correlation peak point; the amplitudes of several adjacent early correlation peak points are scalarly superimposed to obtain the early superimposed amplitude, and the amplitudes of several adjacent late correlation peak points are scalarly superimposed to obtain the late superimposed amplitude; according to the early superimposed amplitude and the late superimposed amplitude, the code phase increment between the coarse synchronization pseudo-code and the DSSS signal is calculated; the phase of the coarse synchronization pseudo-code is modulated based on the code phase increment until the current local pseudo-code is synchronized with the pseudo-code sequence at the transmitting end to obtain the fine synchronization pseudo-code.

[0082] For the captured coarse synchronization pseudo-code, although the phase difference between the phase of the coarse synchronization pseudo-code and the pseudo-code phase in the DSSS signal is relatively small, accurate pseudo-code synchronization has not been achieved yet. Therefore, a pseudo-code tracking loop is still needed to further correct the coarse synchronization pseudo-code.

[0083] The I and Q signals are correlated with the current (Prompt, P), early (Early, E), and late (Late, L) DSSS signals respectively. The code NCO, code generator, shift register, receiver processor, and integration clear device form a code tracking closed loop. Among them, the code generator, code NCO, and shift register form the reproduced code part. Since there is usually one chip difference between E and L, and P is in the middle, the current reproduced pseudo-code in a DSSS signal can be reproduced through E and L. By comparing and calculating the current reproduced pseudo-code with the coarse synchronization pseudo-code, the code phase increment between the coarse synchronization pseudo-code and the DSSS signal can be obtained. The coarse synchronization pseudo-code is adjusted through the code phase increment until the coarse synchronization pseudo-code is synchronized with the reproduced DSSS signal pseudo-code sequence to obtain a perfectly aligned fine synchronization signal.

[0084] Meanwhile, in a possible implementation, the calculation of the correlation peak points between the current reproduced pseudo-code and the coarse synchronization pseudo-code is also performed by superimposition processing. The DSSS signal transmitted by the transmitting end is filtered by a filter; if the filter is a root-raised cosine filter, the number of superimposed early correlation peak points and the number of superimposed late correlation peak points are determined as [IPOINT, 2*IPOINT], where the value of IPOINT is the oversampling multiple of the DSSS signal; if the filter is a low-pass filter, the number of superimposed early correlation peak points and the number of superimposed late correlation peak points are determined as [IPOINT / 2, IPOINT], where the value of IPOINT is the oversampling multiple of the DSSS signal.

[0085] Due to the different densities of the relevant peak points of different filters, the number of relevant peak points after processing by the root raised cosine filter is relatively dense. Except for the maximum peak value, the other relevant peak points are relatively flat. The number of superimposed points and the low-pass filter need to be selected. For example, if the direct sequence spread spectrum (DS) signal rate is 8 MHz and the sampling signal rate of the automatic data collection (ADC) is 64 MHz, then IPOINT is the oversampling ratio, and the oversampling ratio is 64 / 8 = 8.

[0086] In one embodiment, the early local pseudo-code is obtained by shifting the current local pseudo-code forward by half of the spreading code length, and the late local pseudo-code is obtained by delaying the current local pseudo-code by half of the spreading code length; half of the spreading code length is calculated based on the oversampling ratio of the direct sequence spread spectrum signal. The early local pseudo-code and the late local pseudo-code are respectively separated from the current local pseudo-code by half of the spreading code length. Thus, the pseudo-code sequence of the direct sequence spread spectrum signal can be reproduced and compared with the coarse synchronization pseudo-code to achieve complete synchronization.

[0087] In a possible implementation manner, the current superimposed amplitude is maintained at the highest amplitude, and the difference between the early superimposed amplitude and the late superimposed amplitude is processed and code loop filtering is performed to obtain the code phase increment of the coarse synchronization pseudo-code and the code phase increment of the direct sequence spread spectrum signal.

[0088] For the closed-loop adjustment of the tracking process, the specific benchmark for the code loop adjustment is to save the current superimposed amplitude as the highest value. For the phase adjustment where the current superimposed amplitude is slightly reduced, it indicates that there is a small deviation in the adjustment direction or step size. Saving the current superimposed amplitude as the highest amplitude all the time can ensure that the pseudo-code of the reproduced direct sequence spread spectrum signal and the changing current local pseudo-code always maintain the highest correlation, and the code phase increment is obtained to adjust the coarse synchronization pseudo-code.

[0089] Through the above technical solution, after superimposing the relevant peak points, they are respectively compared with multiple thresholds. The subsequent threshold values of the multiple thresholds are greater than the front threshold values, which can reduce the situation of false capture caused by the sudden jump of the relevant peak points due to noise and multipath interference, resulting in useless signals being despread in the subsequent stage. The signal amplitude of the superimposed multiple relevant peak points is more constant, and there will be no misjudgment of the peak value or omission of the peak value, which can enhance the success rate of the capture of the delay locked loop (DLL).

[0090] Please refer to Figure 7 , which is a schematic structural diagram of a pseudo-code synchronization device for multi-threshold comparison in the communication between an unmanned aerial vehicle and a satellite provided by an embodiment of the present application. This device can be implemented as all or part of the device through software, hardware, or a combination of both. The device includes a direct sequence spread spectrum signal receiving module 100, a relevant peak point generating module 200, a relevant peak point superimposing module 300, a coarse synchronization pseudo-code capturing module 400, and a fine synchronization pseudo-code tracking module 500.

[0091] The direct-sequence spread-spectrum (DSSS) signal receiving module 100 is configured to receive the DSSS signal transmitted by the transmitting end;

[0092] The correlation peak point generation module 200 is configured to perform correlation processing on the DSSS signal and the current local pseudo-code to obtain the current correlation peak point;

[0093] The correlation peak point superposition module 300 is configured to scalar-superpose the amplitudes of several adjacent current correlation peak points to obtain the current superposition amplitude;

[0094] The coarse synchronization pseudo-code acquisition module 400 is configured to compare the current superposition amplitudes obtained continuously for multiple times with the acquisition thresholds of corresponding levels respectively. If the current superposition amplitudes obtained continuously for multiple times are all greater than the acquisition thresholds of corresponding levels, the phase of the current local pseudo-code is adjusted in a fixed direction and at a fixed step size to obtain the coarse synchronization pseudo-code;

[0095] The fine synchronization pseudo-code tracking module 500 is configured to perform tracking processing on the coarse synchronization pseudo-code to obtain the fine synchronization pseudo-code.

[0096] The embodiment of the present application further provides a computer storage medium. The computer storage medium can store multiple instructions, and the instructions are suitable for being loaded and executed by a processor to perform the binding method of the embodiment as described above Figures 1 to 7 For example, storing the signal amplitudes of neighbors in a register and performing intermediate storage data processing for calculating the code phase increment in a receiver processor. The specific execution process can refer to Figures 1 to 7 the specific description of the embodiment as shown. Details are not described herein again.

[0097] Please refer to Figure 8 which is a schematic structural diagram of an electronic device provided by the embodiment of the present application. As Figure 8 shown, the electronic device 1000 may include: at least one processor 1001, at least one network interface 1004, a user interface 1003, a memory 1005, and at least one communication bus 1002.

[0098] Among them, the communication bus 1002 is used to implement connection communication between these components.

[0099] Among them, the user interface 1003 may include a display screen (Display) and a camera (Camera). Optionally, the user interface 1003 may further include a standard wired interface and a wireless interface.

[0100] Among them, the network interface 1004 may optionally include a standard wired interface and a wireless interface (such as a WI-FI interface).

[0101] Among them, the processor 1001 may include one or more processing cores. The processor 1001 connects various parts within the entire server through various interfaces and lines, and executes various functions of the server and processes data by running or executing instructions, programs, code sets, or instruction sets stored in the memory 1005, and by calling the data stored in the memory 1005. Optionally, the processor 1001 may be implemented in at least one hardware form of digital signal processing (DSP), field-programmable gate array (FPGA), or programmable logic array (PLA). The processor 1001 may integrate a combination of one or several of a central processing unit (CPU), a graphics processing unit (GPU), and a modem, etc. Among them, the CPU mainly processes the operating system, user interface, application programs, etc.; the GPU is responsible for rendering and drawing the content to be displayed on the display screen; the modem is used to process wireless communication. It can be understood that the above-mentioned modem may not be integrated into the processor 1001 and may be implemented separately by a single chip.

[0102] Among them, the memory 1005 may include random access memory (RAM) and may also include read-only memory. Optionally, the memory 1005 includes a non-transitory computer-readable storage medium. The memory 1005 can be used to store instructions, programs, code, code sets, or instruction sets. The memory 1005 may include a program storage area and a data storage area. Among them, the program storage area may store instructions for implementing the operating system, instructions for at least one function (such as touch function, sound playback function, image playback function, etc.), instructions for implementing the above-mentioned various method embodiments, etc.; the data storage area may store the data involved in the above-mentioned various method embodiments. Optionally, the memory 1005 may further be at least one storage device located far from the aforementioned processor 1001. As Figure 8 shown, the memory 1005, as a computer storage medium, may include an operating system, a network communication module, a user interface module, and an application program for the pseudo-code synchronization method of multi-level threshold comparison in the communication between the drone and the satellite.

[0103] In Figure 8In the electronic device 1000 shown, the user interface 1003 is mainly used to provide an interface for the user to input and obtain the data input by the user; and the processor 1001 can be used to call the application program stored in the memory 1005 for a pseudo-code synchronization method for multi-level threshold comparison in the communication between an unmanned aerial vehicle and a satellite. When executed by one or more processors, the electronic device is caused to execute one or more of the methods as described in the above embodiments.

[0104] An electronic device-readable storage medium stores instructions. When executed by one or more processors, the electronic device is caused to execute one or more of the methods as described in the above embodiments.

[0105] It should be noted that, for the foregoing method embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that this application is not limited by the described action sequence, because according to this application, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and modules involved are not necessarily essential to this application.

[0106] In the above embodiments, the descriptions of the various embodiments have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0107] In several embodiments provided by this application, it should be understood that the disclosed device can be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of the units is only a logical function division. In actual implementation, there can be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the displayed or discussed coupling or direct coupling or communication connection to each other can be through some service interfaces. The indirect coupling or communication connection of the device or unit can be in an electrical or other form.

[0108] The units described as separate components may or may not be physically separated. The components displayed as units may or may not be physical units, that is, they can be located in one place, or they can be distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0109] In addition, in each embodiment of the present application, each functional unit may be integrated into one processing unit, may exist physically alone for each unit, or two or more units may be integrated into one unit. The above integrated unit may be implemented in the form of hardware or in the form of a software functional unit.

[0110] If the above integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it may be stored in a computer-readable memory. Based on such an understanding, the technical solution of the present application, in essence, or the part that contributes to the prior art, or all or part of the technical solution, may be embodied in the form of a software product. The computer software product is stored in a memory and includes several instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the methods described in each embodiment of the present application. The aforementioned memory includes various media such as USB flash drives, mobile hard disks, magnetic disks, or optical discs that can store program codes.

[0111] The foregoing are only exemplary embodiments of the present disclosure and should not be used to limit the scope of the present disclosure. That is, any equivalent changes and modifications made in accordance with the teachings of the present disclosure still fall within the scope covered by the present disclosure. After considering the specification and the disclosure of the practical truth, those skilled in the art will readily think of other implementation manners of the present disclosure. The present application aims to cover any variations, uses, or adaptive changes of the present disclosure, and these variations, uses, or adaptive changes follow the general principles of the present disclosure and include the common general knowledge or conventional technical means in the technical field not recorded in the present disclosure. The specification and the embodiments are only regarded as exemplary, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. A method for pseudo - code synchronization with multi - level threshold comparison in the communication between an unmanned aerial vehicle and a satellite, characterized in that, applied to a pseudo - code loop, the method includes: Receiving the direct - sequence spread - spectrum signal sent by the transmitting end; Performing correlation processing on the direct - sequence spread - spectrum signal and the current local pseudo - code to obtain the current correlation peak point; Scalar - adding the amplitudes of several adjacent current correlation peak points to obtain the current superimposed amplitude; Comparing the current superimposed amplitudes obtained continuously for multiple times with the capture thresholds of corresponding levels respectively. If the current superimposed amplitudes obtained continuously for multiple times are all greater than the capture thresholds of corresponding levels, then adjusting the phase of the current local pseudo - code in a fixed direction and with a fixed step size to obtain a roughly synchronized pseudo - code; Performing tracking processing on the roughly synchronized pseudo - code to obtain a precisely synchronized pseudo - code; The performing tracking processing on the roughly synchronized pseudo - code to obtain a precisely synchronized pseudo - code includes: Performing correlation processing on the direct - sequence spread - spectrum signal with an early local pseudo - code and a late local pseudo - code respectively to obtain an early correlation peak point and a late correlation peak point; Scalar - adding the amplitudes of several adjacent early correlation peak points to obtain an early superimposed amplitude, and scalar - adding the amplitudes of several adjacent late correlation peak points to obtain a late superimposed amplitude; Calculating the code - phase increment between the roughly synchronized pseudo - code and the direct - sequence spread - spectrum signal according to the early superimposed amplitude and the late superimposed amplitude; Modulating the phase of the roughly synchronized pseudo - code based on the code - phase increment until the current local pseudo - code is code - synchronized with the pseudo - code sequence of the transmitting end to obtain a precisely synchronized pseudo - code.

2. The method according to claim 1, characterized in that, The capture thresholds include a first - level capture threshold, a second - level capture threshold, and a third - level capture threshold. The first - level capture threshold is less than the second - level capture threshold, and the second - level capture threshold is less than the third - level capture threshold.

3. The method according to claim 1, characterized in that, Before performing correlation processing on the direct - sequence spread - spectrum signal with an early local pseudo - code and a late local pseudo - code respectively to obtain an early correlation peak point and a late correlation peak point, it further includes: Filtering the direct - sequence spread - spectrum signal sent by the transmitting end using a filter; If the filter is a root - raised - cosine filter, then determining the number of superimposed early correlation peak points and the number of superimposed late correlation peak points as [IPOINT, 2 * IPOINT], where the value of IPOINT is the oversampling multiple of the direct - sequence spread - spectrum signal; If the filter is a low - pass filter, then determining the number of superimposed early correlation peak points and the number of superimposed late correlation peak points as [IPOINT / 2, IPOINT], where the value of IPOINT is the oversampling multiple of the direct - sequence spread - spectrum signal.

4. The method according to claim 1, characterized in that, The early local pseudo - code is obtained by shifting the current local pseudo - code forward by half of the spreading code length, and the late local pseudo - code is obtained by delaying the current local pseudo - code by half of the spreading code length; the half of the spreading code length is calculated based on the oversampling multiple of the direct - sequence spread - spectrum signal.

5. The method according to claim 1, characterized in that, Calculating a code phase increment between the coarse synchronization pseudo-code and the direct spread signal according to the leading superposition amplitude and the lagging superposition amplitude includes: Keeping the current superposition amplitude as the highest amplitude, performing a difference operation and code loop filtering on the leading superposition amplitude and the lagging superposition amplitude to obtain the code phase increment.

6. The method according to claim 1, wherein, the fixed step size is between 1 / 8 length and 1 / 2 length of one chip.

7. A pseudo-code synchronization device for multi-level threshold comparison in UAV-satellite communication, wherein, applied to a pseudo-code loop, the device includes: A direct spread signal receiving module, configured to receive a direct spread signal sent by a transmitting end; A correlation peak point generating module, configured to perform correlation processing on the direct spread signal and a current local pseudo-code to obtain a current correlation peak point; A correlation peak point superposition module, configured to scalar superpose the amplitudes of several adjacent current correlation peak points to obtain a current superposition amplitude; A coarse synchronization pseudo-code acquisition module, configured to respectively compare the current superposition amplitudes obtained continuously for multiple times with capture thresholds of corresponding levels. If the current superposition amplitudes obtained continuously for multiple times are all greater than the capture thresholds of the corresponding levels, adjust the phase of the current local pseudo-code in a fixed direction and at a fixed step size to obtain a coarse synchronization pseudo-code; A fine synchronization pseudo-code tracking module, configured to perform tracking processing on the coarse synchronization pseudo-code to obtain a fine synchronization pseudo-code; the performing tracking processing on the coarse synchronization pseudo-code to obtain a fine synchronization pseudo-code includes: performing correlation processing on the direct spread signal with a leading local pseudo-code and a lagging local pseudo-code respectively to obtain a leading correlation peak point and a lagging correlation peak point; scalar superposing the amplitudes of several adjacent leading correlation peak points to obtain a leading superposition amplitude, scalar superposing the amplitudes of several adjacent lagging correlation peak points to obtain a lagging superposition amplitude; calculating a code phase increment between the coarse synchronization pseudo-code and the direct spread signal according to the leading superposition amplitude and the lagging superposition amplitude; modulating the phase of the coarse synchronization pseudo-code based on the code phase increment until code synchronization is achieved between the current local pseudo-code and the pseudo-code sequence of the transmitting end to obtain a fine synchronization pseudo-code.

8. An electronic device, wherein, including a processor, a memory, a user interface and a network interface, the memory is used to store instructions, the user interface and the network interface are used to communicate with other devices, and the processor is used to execute the instructions stored in the memory so that the electronic device executes the method according to any one of claims 1-6.

9. A computer storage medium, wherein, the computer storage medium stores multiple instructions, and the instructions are suitable for being loaded and executed by a processor to execute the method according to any one of claims 1-6.

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