Synchronization system for DSSS pseudo code signals

Abstract

The invention provides a synchronization system for DSSS pseudo code signals. The synchronization system comprises a capturing module, a pseudo code positioning module and a pseudo code tracking module. The synchronization method comprises the following steps: the capture module captures a pseudo code element in a DSSS signal; the pseudo code positioning module is used for preliminarily positioning a first pseudo code element in the first pseudo code signal; and the pseudo code tracking module obtains a synchronization result of the DSSS pseudo code signal. Three frequency spectrum enhancement modules in the pseudo code tracking module carry out frequency spectrum enhancement on detection results of frequency spectrum data after PMF-FFT operation of the three branches, correction of the maximum value of frequency domain module values of the three branches is achieved, and then related gain scallop loss of the maximum value of the frequency domain module values in the pseudo code tracking process is reduced. The synchronization precision is effectively improved; and meanwhile, the acquisition module does not need to participate in an FFT (Fast Fourier Transform) operation unit when acquiring the pseudo code elements in the DSSS signals, so that the delay of pseudo code acquisition is reduced, and the synchronization efficiency is effectively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communication, and relates to a synchronization system of DSSS pseudo code signals, which can be applied to satellite-to-ground communication in high-mobility scenarios. Background Art

[0002] The DSSS communication system achieves broadband transmission of signals by multiplying low-speed data signals with high-speed spread spectrum codes, where the high-speed spread spectrum codes are called DSSS pseudo-code signals. A complete DSSS communication system receiver includes the synchronization of pseudo-code signals and the despreading and demodulation of pseudo-code signals after synchronization. Pseudo-code signal synchronization refers to the phase of the pseudo-code signal in the received DSSS signal after the phase is aligned with the phase of the local pseudo-code sequence, and then the phase of the pseudo-code signal in the DSSS signal is output. The basic structure of the pseudo-code signal synchronization system includes pseudo-code capture, positioning and tracking. In recent years, the research on DSSS pseudo-code signal capture, positioning and tracking algorithms has mainly revolved around the implementation of the PMF-FFT algorithm. The correlation between the received signal and the local pseudo-code sequence is used to smooth the correlation value, and the peak value of the FFT operation result after filtering is threshold judged to complete pseudo-code signal capture, positioning and tracking.

[0003] For example, the patent document with application publication number CN112910498A and titled "PMF-FFT measurement and control signal capture device and method" discloses a synchronization system for DSSS pseudocode signals, which includes a digital down-conversion module, a PMF module, an FFT module, a peak detection module, a code generation module, a code phase compensation module, a loop control module and a Tang detection module. The invention adopts a fully parallel pipeline to speed up the capture speed, uses the same correlator structure to control different numbers of cycles to achieve the process of coarse capture and fine capture, so as to save hardware resources as much as possible, and uses a variable-order window function FIR filter to smooth the spectrum for different modulation rate data to improve the capture accuracy of Doppler frequency. The same correlator structure is used to adjust the search range of the code phase by controlling the number of cycles, thereby achieving coarse capture and fine capture, reducing the design complexity and improving the adaptation flexibility. However, the FFT operation in the pseudocode capture and tracking process of the invention increases the pseudocode synchronization delay, the synchronization efficiency is low, and there will be a certain correlation gain scallop loss at the maximum value of the spectrum in the pseudocode tracking process, which limits the further improvement of the synchronization accuracy. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and propose a synchronization system of DSSS pseudo code signals to solve the technical problems of low synchronization accuracy and efficiency in the prior art.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A DSSS pseudocode signal synchronization system comprises a cascaded capture module, a pseudocode positioning module and a pseudocode tracking module; the pseudocode tracking module comprises a cascaded pseudocode control unit and a pseudocode positioning output unit, and three composite modules loaded between the two units and arranged in parallel, each composite module comprises a cascaded PMF-FFT module and a peak detection unit; the capture module comprises a cascaded data preprocessing unit, a cross-correlation unit, a sliding window summing unit and a peak detection unit; the pseudocode positioning module comprises a cascaded peak diversity unit, a line segment fitting unit and a pseudocode synchronization point solving unit; the pseudocode tracking module comprises a spectrum enhancement module in cascade connection at the output end of the peak detection unit in each composite module contained therein.

[0007] As an optimization, the PMF-FFT module includes a cascaded cross-correlation unit, a segmented summation unit, a zero-filling unit, and an FFT operation unit; the spectrum enhancement module includes a cascaded correction coefficient calculation unit and a spectrum peak correction unit.

[0008] As an optimization, the FFT operation unit includes a plurality of stacked butterfly operation structures, the butterfly operation structure includes parallel arrangement There are butterfly operation modules, each of which includes a multiplier, an adder and a subtractor, where W represents the number of points input to the FFT operation unit.

[0009] A DSSS pseudo code signal synchronization method comprises the following steps:

[0010] (1) Initialization parameters:

[0011] The initialization DSSS signal includes a total of N composite envelope signals x consisting of a forward noise sequence and a pseudo code signal sequence of length K. The kth pseudo code signal y(k) includes L pseudo code symbols, and the lth pseudo code symbol is p k (l), the nth complex envelope signal is x n , x n =I xn +iQ xn ; Initialize the local pseudo code signal to U m , whose length is L, and the lth local pseudo code signal is u l ,u l =I ul +iQ ul , and U m Stored in the local pseudo code storage unit of the pseudo code tracking module; initialize the first and second detection thresholds to δ and μ respectively; initialize the number of points of the FFT operation unit to W; where N ≥ 9000, K ≥ 1, L ≥ 64, I xn, Q xn Respectively represent x n The real and imaginary parts, I ul , Q ul Respectively represent u l The real and imaginary parts of , i represents the imaginary unit;

[0012] (2) The capture module captures the pseudo code elements in the DSSS signal:

[0013] The capture module captures each complex envelope signal x in the DSSS signal. n Preprocessing is performed, and the two sets of preprocessed frequency-multiplied data are cross-correlated, and then the cross-correlation result is segmented and normalized to obtain a normalized cross-correlation result sequence R, and then R is detected to obtain a pseudo-code symbol sequence of length M, where M = K × L;

[0014] (3) The pseudo-code positioning module performs preliminary positioning of the first pseudo-code symbol in the first pseudo-code signal:

[0015] The pseudo code positioning module locates the first pseudo code symbol p1(1) of the first pseudo code signal y(1) according to the position of the pseudo code symbol sequence in the complex envelope signal sequence x, and obtains the preliminary position t of p1(1) in the complex envelope signal sequence x. tmp ;

[0016] (4) The pseudo code tracking module obtains the synchronization result of the DSSS pseudo code signal:

[0017] The pseudo code tracking module determines the initial position t of the first pseudo code symbol p1(1) of the first pseudo code signal y(1) tmp Adjust to obtain the exact starting position t1 of p1(1) in the complex envelope signal sequence x, and calculate the exact starting position t1 of the first pseudo code symbol of the remaining K-1 pseudo code signals in the complex envelope signal sequence x according to t1. k , 2≤k≤K, t1 and the remaining K-1 precise starting positions are used as the synchronization results of the DSSS pseudo code signal.

[0018] Compared with the prior art, the present invention has the following advantages:

[0019] 1. The three spectrum enhancement modules in the pseudo code tracking module of the present invention perform spectrum enhancement on the detection results of the spectrum data obtained by the PMF-FFT operation of the three branches, thereby realizing the correction of the maximum frequency domain modulus values ​​of the three branches, thereby reducing the related gain scallop loss of the maximum frequency domain modulus value in the pseudo code tracking process, and effectively improving the synchronization accuracy compared with the prior art.

[0020] 2. The capture module of the present invention includes a cascaded data preprocessing unit, a cross-correlation unit, a sliding window summation unit and a peak detection unit. In the process of capturing the pseudo-code code elements in the DSSS signal, the pseudo-code code element sequence can be obtained without the participation of the FFT operation unit, thereby avoiding the influence of the prior art on the pseudo-code synchronization delay caused by the FFT operation during the pseudo-code capture and tracking process, and effectively improving the synchronization efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the capture module of the present invention;

[0022] Figure 2 It is a structural schematic diagram of the pseudo code positioning module of the present invention;

[0023] Figure 3 It is a structural schematic diagram of the pseudo code tracking module of the present invention;

[0024] Figure 4 It is a structural schematic diagram of the PMF-FFT module of the present invention;

[0025] Figure 5 It is a structural schematic diagram of the FFT operation unit of the present invention;

[0026] Figure 6 It is a structural schematic diagram of the spectrum enhancement module of the present invention;

[0027] Figure 7 This is a flow chart for implementing the synchronization method of the present invention. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0029] The synchronization system of the present invention comprises a cascaded capture module, a pseudo code positioning module and a pseudo code tracking module;

[0030] Reference Figure 1 The capture module includes a cascaded data preprocessing unit, a cross-correlation unit, a sliding window summing unit, and a peak detection unit; the data preprocessing unit uses a DSSS signal sequence to perform frequency multiplication, and performs leading and trailing 0 operations on the frequency multiplied sequence to obtain delayed frequency multiplication data and original frequency multiplication data; the cross-correlation unit is used to calculate the cross-correlation sequence of the delayed frequency multiplication data and the original frequency multiplication data; the sliding window summing unit is used to perform segmented summation on the cross-correlation sequence, and the peak detection unit is used to perform threshold detection on the correlation peak after the segmented summation to obtain captured pseudo-code code elements.

[0031] Reference Figure 2The pseudo-code positioning module includes a cascaded peak diversity unit, a line segment fitting unit, and a pseudo-code synchronization point solving unit; the peak diversity unit is used to perform threshold judgment on the correlation peak at the corresponding position of each captured pseudo-code code element in the DSSS signal, and construct two groups of dot matrixes with the current position and the correlation peak as the horizontal coordinate and the vertical coordinate respectively; the line segment fitting unit performs line segment fitting on the two groups of dot matrixes respectively; the pseudo-code synchronization point solving unit solves the two line segment equations obtained by fitting simultaneously.

[0032] Reference Figure 3 The pseudo code tracking module includes a cascaded pseudo code control unit and a pseudo code positioning output unit, and three composite modules loaded between the two units and arranged in parallel; wherein the first, second and third composite modules respectively include the cascaded first, second and third PMF-FFT modules, the first, second and third peak detection units and the first, second and third spectrum enhancement modules; wherein the pseudo code control unit is used to obtain a local pseudo code signal sequence, an advanced pseudo code signal sequence, an advanced pseudo code signal sequence and a composite envelope signal continuously taken out from the DSSS signal according to the equation solution point; wherein the first, first and third peak detection units respectively detect the maximum frequency domain modulus value output by the first, first and third PMF-FFT modules and the frequency domain modulus values ​​of the two points on the left and right of the maximum value; the first, first and third spectrum enhancement modules respectively correct the maximum frequency domain modulus values ​​of the three branches; the pseudo code positioning output unit is used to calculate the first code element position of each pseudo code signal and use it as the synchronization result of the DSSS pseudo code signal.

[0033] Reference Figure 4 The PMF-FFT module includes a cascaded cross-correlation unit, a segmented summation unit, a zero-filling unit, and an FFT operation unit; wherein the cross-correlation unit is used to calculate the cross-correlation result of two inputs; wherein the segmented summation unit is used to segment and sum the result output by the cross-correlation unit; wherein the zero-filling unit is used to post-fill zero operation on the result of the segmented summation.

[0034] Reference Figure 5 The FFT operation unit includes a plurality of stacked butterfly operation structures, and the butterfly operation structure includes parallel arrangement There are butterfly operation modules, each of which includes a multiplier, an adder and a subtractor, where W represents the number of points input to the FFT operation unit.

[0035] In this embodiment, the number of butterfly operation structures is 8, and W=256.

[0036] Reference Figure 6The spectrum enhancement module includes a cascaded correction coefficient calculation unit and a spectrum peak correction unit; wherein the correction coefficient calculation unit is used to calculate the correction coefficient of the maximum frequency domain modulus value; wherein the spectrum peak correction unit is used to correct the maximum frequency domain modulus value.

[0037] Reference Figure 7 The synchronization method of the present invention comprises the following steps:

[0038] Step 1) Initialize parameters:

[0039] The initialization DSSS signal includes a total of N composite envelope signals x consisting of a forward noise sequence and a pseudo code signal sequence of length K. The kth pseudo code signal y(k) includes L pseudo code symbols, and the lth pseudo code symbol is p k (l), the nth complex envelope signal is x n , x n =I xn +iQ xn ; Initialize the local pseudo code signal to U m , whose length is L, and the lth local pseudo code signal is u l ,u l =I ul +iQ ul , and U m Stored in the local pseudo code storage unit of the pseudo code tracking module; initialize the first and second detection thresholds to δ and μ respectively; initialize the number of points of the FFT operation unit to W; where N ≥ 9000, K ≥ 1, L ≥ 64, I xn , Q xn Respectively represent x n The real and imaginary parts, I ul , Q ul Respectively represent u l The real and imaginary parts of , i represents the imaginary unit; in this example, N = 10000, K = 10, L = 512;

[0040] Step 2) The capture module captures the pseudo code elements in the DSSS signal:

[0041] (2a) The data preprocessing unit processes each complex envelope signal x n Perform square multiplication and calculate the square multiplication signal sequence x 2 Perform the 128-bit leading and trailing zero operations respectively, and obtain the delayed frequency-multiplied data d after leading zero-padded and the original frequency-multiplied data g after trailing zero-padded, which are 10128 in length, respectively, that is, d = {0, 0, ..., x1 2 , x2 2 , …, x 10000 2}, g = {x1 2 ,x22 ,…,x 10000 2 , 0, 0, …, 0};

[0042] (2b) The cross-correlation unit performs a cross-correlation operation on each element in d and the element at the corresponding position in g. First, the conjugate of each element in g is taken to obtain g * , then in the pair d and g * Perform multiplication on each element in to obtain a cross-correlation result sequence with a length of 10128;

[0043] (2c) The sliding window summing unit divides the cross-correlation result sequence into N segments, and the segmentation method is as follows: each segment takes n as the starting point, 1≤n≤10000, and 128 cross-correlation results are continuously taken from the starting point of each segment in the cross-correlation result sequence with a length of 10128; and the 128 cross-correlation results in each segment are summed, and then the sum of the modulus values ​​of the cross-correlation results in each segment is normalized to obtain 10000 normalized cross-correlation results R, wherein the nth cross-correlation result is R(n);

[0044] (2d) the peak detection unit detects the cross-correlation results R that are greater than the first detection threshold δ, and uses 5120 complex envelope signals at corresponding positions of the detected 5120 cross-correlation results in the complex envelope signal sequence x as pseudo code symbols of x;

[0045] In the process of capturing pseudo-code symbols in DSSS signals, the capture module of the present invention can obtain the pseudo-code symbol sequence without the participation of the FFT operation unit, thereby avoiding the influence of the FFT operation required in the pseudo-code capture process on the pseudo-code synchronization delay in the prior art, and effectively improving the synchronization efficiency.

[0046] Step 3) The pseudo code positioning module performs preliminary positioning of the first pseudo code symbol in the first pseudo code signal:

[0047] (3a) The peak diversity unit determines whether each cross-correlation result R(n) of the 5120 pseudo-code symbols at the corresponding position in the complex envelope signal sequence x satisfies δ≤R(n)<μ. If so, the current n and R(n) are the horizontal and vertical coordinates p respectively. T1 , γ T1 , construct the ascending interval lattice T1 = {(p T1 (1),γ T1 (1)),(p T1 (2),γ T1 (2)),…,(p T1 (C1),γ T1 (C1)}; otherwise, the current n and R(n) are the horizontal and vertical coordinates p respectively. T2 , γT2 , construct the flat interval lattice T2 = {(p T2 (1),γ T2 (1)),(p T2 (2),γ T2 (2)),…,(p T2 (C2),γ T2 (C2)}, where C1 and C2 represent the total number of samples of T1 and T2 respectively, C1+C2=5120;

[0048] (3b) The line segment fitting unit performs line segment fitting on the ascending interval dot matrix T1 and the flat interval dot matrix T2, respectively, and obtains the linear equation y0=a0x+b0 corresponding to T1 and the constant equation y1=b1 corresponding to T2, where:

[0049]

[0050]

[0051]

[0052] Where a0 and b0 represent the coefficient of the first-order term and the coefficient of the zero-order term of the linear equation y0, respectively; b1 represents the coefficient of the zero-order term of the constant equation y1; h represents the sample index of the rising interval lattice T1, 1≤h≤C1; j represents the sample index of the flat interval lattice T2, 1≤j≤C2; ∑(·) represents the summation operation;

[0053] (3c) The pseudo code synchronization point solving unit solves the linear equation y0=a0x+b0 and the constant equation y1=b1 to obtain the initial position t of p1(1) in the complex envelope signal sequence x. tmp :

[0054]

[0055] Where [·] represents the floor symbol.

[0056] Step 4) The pseudo code tracking module obtains the synchronization result of the DSSS pseudo code signal:

[0057] (4a) The pseudo code control unit generates a local pseudo code signal sequence U m ={u1,u2,…,u l ,…,u L} Perform left and right circular shift operations by 1 bit respectively to obtain the advanced pseudo code signal U le ={u2,…,u l ,…,u L ,u1} and the delayed pseudo code signal U ri = {u L ,u1,…,u l,…,u (L-1)}, and according to the initial position t of the first pseudo code symbol p1(1) of the first pseudo code signal in the complex envelope signal sequence x tmp Continuously extract 512 complex envelope signals from the complex envelope signal sequence x

[0058] (4b) The three PMF-FFT modules in the three composite modules respectively calculate U le and O, U m and O, U ri Perform PMF-FFT operation on O to obtain the three branch spectrum data F l 、F m 、F r The three peak detection units and spectrum enhancement modules are used to detect F l 、F m 、F r Perform peak detection and spectrum enhancement processing to obtain the maximum value Fl of the three branch corrected frequency domain modulus values cmax 、Fm cmax and Fr. cmax , the specific implementation steps are:

[0059] (4b1) The three cross-correlation units of the three PMF-FFT modules in the three composite modules respectively calculate U le and O, U m and O, U ri Perform cross-correlation operation on the elements at the corresponding positions in O to obtain a cross-correlation result sequence R containing 512 cross-correlation results. ulo , R umo , R uro ; The three segmented summing units respectively ulo , R umo , R uro Each 4-element segment is divided into 128 segments, and the sum of the cross-correlation results in each segment is calculated to obtain a sequence S containing 128 cross-correlation summation results. Rlo , S Rmo , S Rro ; The three zero-filling units respectively perform the summation of the three cross-correlation result sequences S containing 128 elements Rlo , S Rmo , S Rro , respectively, perform 128 zero-filling operations to obtain the zero-filling sequence SC of the cross-correlation summation result containing W elements. Rlo , SC Rmo , SC Rro ; The three FFT operation units perform SC Rlo , SC Rmo , SC RroThe sequence is subjected to W-point FFT operation to obtain three branch spectrum data F containing 256 elements each. l 、F m 、F r ;

[0060] The three FFT operation units perform SC Rlo , SC Rmo , SC Rro The sequence performs 256-point FFT operation, and the implementation steps are:

[0061] The FFT operation unit processes 256 points of data through the first layer of butterfly operation structure. The 128 butterfly operation blocks in each layer perform one multiplication operation, one addition operation and one subtraction operation on each 2 data to form a group of 128 data, and then pass it to the next layer of butterfly operation structure. After eight layers of butterfly operation structure operation, three branch spectrum data F containing 256 elements are obtained. l 、F m 、F r .

[0062] (4b2) The three peak detection units respectively detect the three branch spectrum data F l 、F m 、F r The maximum value of the modulus of the 256 elements of F is detected, and the three maximum modulus values ​​are obtained respectively. l 、F m 、F r The position w in lmax 、w mmax 、w rmax , and then take out the maximum value of the three branch spectrum data modulus and the frequency domain data modulus of the left and right elements |F l (w lmax )|、|F l (w lmax -1)|、|F l (w lmax +1)| and|F m (w mmax )|、|F m (w mmax -1)|、|F m (w mmax +1)| and|F r (w rmax )|、|F r (w rmax -1)|、|F r (w rmax +1)|;

[0063] (4b3) The three correction coefficient calculation units in the three spectrum enhancement modules are connected by |Fl (w lmax -1)|、|F l (w lmax )|、|F l (w lmax +1)| and|F m (w mmax -1)|、|F m (w mmax )|、|F m (w mmax +1)| and|F r (w rmax -1)|、|F r (w rmax )|、|F r (w rmax +1)|, calculate the correction coefficients δ of the three branches l , δ m , δ r ; The three spectrum peak correction units are respectively l , δ m , δ r Calculate the maximum value Fl of the three branch corrected frequency domain modulus cmax 、Fm cmax , Fr cmax :

[0064]

[0065]

[0066] Where π represents the ratio of a circle to a circle, and tan(·) represents the calculated tangent value.

[0067] The three spectrum enhancement modules in the pseudo code tracking module of the present invention calculate the correction coefficients δ of the three branches according to the spectrum data obtained by the PMF-FFT operation of the three branches. l , δ m , δ r ; and the error of the maximum frequency domain modulus value is compensated according to the correction coefficient, thereby reducing the related gain scallop loss of the maximum frequency domain modulus value in the pseudo code tracking process, and effectively improving the synchronization accuracy.

[0068] (4c) The pseudo-code positioning output unit corrects the maximum frequency domain modulus value Fl through three branches cmax 、Fm cmax and Fr. cmax Determine the exact starting position t1 of the first pseudo code symbol p1(1) of the first pseudo code signal y(1) in the complex envelope signal sequence x, and calculate the exact starting position t1 of the first pseudo code symbol of the remaining 9 pseudo code signals in the complex envelope signal sequence x based on t1 k, 2≤k≤9, t1 and the other 9 precise starting positions are used as the synchronization results of the DSSS pseudo code signal, where:

[0069] If Fm cmax >Fl cmax ,Fm cmax >Fr cmax , t1=t tmp ;

[0070] If Fl cmax >Fm cmax ,Fl cmax >Fr cmax , t1=t tmp -1;

[0071] If Fr cmax >Fm cmax ,Fr cmax >Fl cmax , t1=t tmp +1;

[0072] t k =t1+(k-1)*5120, 2≤k≤9.

Claims

1. A DSSS pseudo code signal synchronization system, comprising a cascaded capture module, a pseudo code positioning module and a pseudo code tracking module; the pseudo code tracking module comprises a cascaded pseudo code control unit and a pseudo code positioning output unit, and three composite modules loaded between the two units and arranged in parallel, each composite module comprising a cascaded PMF-FFT module and a peak detection unit; characterized in that, The capture module includes a cascaded data preprocessing unit, a cross-correlation unit, a sliding window summation unit and a peak detection unit; the pseudo-code positioning module includes a cascaded peak diversity unit, a line segment fitting unit and a pseudo-code synchronization point solving unit; the pseudo-code tracking module, the output end of the peak detection unit in each composite module contained in it is also cascaded with a spectrum enhancement module.

2. The system according to claim 1, characterized in that The PMF-FFT module comprises a cascaded cross-correlation unit, a segmented summation unit, a zero-filling unit, and an FFT operation unit.

3. The system according to claim 1, wherein the FFT operation unit comprises a plurality of stacked butterfly operation structures, wherein the butterfly operation structure comprises parallel arranged There are butterfly operation modules, each of which includes a multiplier, an adder and a subtractor, where W represents the number of points input to the FFT operation unit.

4. The method for implementing the system according to claim 1, characterized in that: The steps include: (1) Initialization parameters: The initialization DSSS signal includes a total of N composite envelope signals x consisting of a forward noise sequence and a pseudo code signal sequence of length K. The kth pseudo code signal y(k) includes L pseudo code symbols, and the lth pseudo code symbol is p k (l), the nth complex envelope signal is x n , x n =I xn +iQ xn ; Initialize the local pseudo code signal to U m , whose length is L, and the lth local pseudo code signal is u l , and U m Stored in the local pseudo code storage unit of the pseudo code tracking module; initialize the first and second detection thresholds to δ and μ respectively; initialize the number of points of the FFT operation unit to W; where N ≥ 9000, K ≥ 1, L ≥ 64, I xn , Q xn Respectively represent x n The real and imaginary parts, I ul , Q ul Respectively represent u l The real and imaginary parts of , i represents the imaginary unit; (2) The capture module captures the pseudo code elements in the DSSS signal: The capture module captures each complex envelope signal x in the DSSS signal. n Preprocessing is performed, and the two sets of preprocessed frequency-multiplied data are cross-correlated, and then the cross-correlation result is segmented and normalized to obtain a normalized cross-correlation result sequence R, and then R is detected to obtain a pseudo-code symbol sequence of length M, where M = K × L; (3) The pseudo-code positioning module performs preliminary positioning of the first pseudo-code symbol in the first pseudo-code signal: The pseudo code positioning module locates the first pseudo code symbol p1(1) of the first pseudo code signal y(1) according to the position of the pseudo code symbol sequence in the complex envelope signal sequence x, and obtains the preliminary position t of p1(1) in the complex envelope signal sequence x. tmp ; (4) The pseudo code tracking module obtains the synchronization result of the DSSS pseudo code signal: The pseudo code tracking module determines the initial position t of the first pseudo code symbol p1(1) of the first pseudo code signal y(1) tmp Adjust to obtain the exact starting position t1 of p1(1) in the complex envelope signal sequence x, and calculate the exact starting position t1 of the first pseudo code symbol of the remaining K-1 pseudo code signals in the complex envelope signal sequence x according to t1. k , 2≤k≤K, t1 and the remaining K-1 precise starting positions are used as the synchronization results of the DSSS pseudo code signal.

5. The method according to claim 4, characterized in that The capture module described in step (2) captures the pseudo code elements in the DSSS signal, and the implementation steps are as follows: (2a) The data preprocessing unit processes each complex envelope signal x n Perform square multiplication and calculate the square multiplication signal sequence x 2 Perform S-bit leading zero-filling and trailing zero-filling operations respectively to obtain delayed frequency-multiplied data d after leading zero-filling and original frequency-multiplied data g after trailing zero-filling with a length of N+S, where S≥64; (2b) The cross-correlation unit performs a cross-correlation operation on each element in d and the element at the corresponding position in g to obtain a cross-correlation result sequence with a length of N+S; (2c) The sliding window summing unit divides the cross-correlation result sequence into N segments, and normalizes the sum of the modulus values ​​of the cross-correlation results in each segment to obtain N normalized cross-correlation results R, wherein the nth cross-correlation result is R(n); (2d) The peak detection unit detects the cross-correlation results R that are greater than the first detection threshold δ, and uses the M complex envelope signals at corresponding positions of the detected M cross-correlation results in the complex envelope signal sequence x as pseudo code elements of x.

6. The method according to claim 4, characterized in that The pseudo code positioning module described in step (3) performs preliminary positioning on the first pseudo code symbol in the first pseudo code signal, and the implementation steps are as follows: (3a) The peak diversity unit determines whether each cross-correlation result R(n) of the M pseudo-code symbols at the corresponding position in the complex envelope signal sequence x satisfies δ≤R(n)<μ. If so, the current n and R(n) are the horizontal and vertical coordinates p respectively. T1 , γ T1 , construct the ascending interval lattice T1 = {(p T1 (1),γ T1 (1)),(p T1 (2),γ T1 (2)),…,(p T1 (C1),γ T1 (C1)}; otherwise, the current n and R(n) are the horizontal and vertical coordinates p respectively. T2 , γ T2 , construct the flat interval lattice T2 = {(p T2 (1),γ T2 (1)),(p T2 (2),γ T2 (2)),…,(p T2 (C2),γ T2 (C2)}, where C1 and C2 represent the total number of samples of T1 and T2 respectively, and C1+C2=M; (3b) The line segment fitting unit performs line segment fitting on the ascending interval dot matrix T1 and the flat interval dot matrix T2, respectively, and obtains the linear equation y0=a0x+b0 corresponding to T1 and the constant equation y1=b1 corresponding to T2, where: Where a0 and b0 represent the coefficient of the first-order term and the coefficient of the zero-order term of the linear equation y0, respectively; b1 represents the coefficient of the zero-order term of the constant equation y1; h represents the sample index of the rising interval lattice T1, 1≤h≤C1; j represents the sample index of the flat interval lattice T2, 1≤j≤C2; ∑(·) represents the summation operation; (3c) The pseudo code synchronization point solving unit solves the linear equation y0=a0x+b0 and the constant equation y1=b1 to obtain the initial position t of p1(1) in the complex envelope signal sequence x. tmp : Where [·] represents the floor symbol.

7. The method according to claim 4, characterized in that The pseudo code tracking module described in step (4) obtains the synchronization result of the DSSS pseudo code signal, and the implementation steps are as follows: (4a) The pseudo code control unit generates a local pseudo code signal sequence U m ={u1,u2,…,u l ,…,u L } Perform left and right cyclic shift operations by 1 bit respectively to obtain the leading pseudo code signal sequence U le ={u2,…,u l ,…,u L ,u1} and the delayed pseudo code signal sequence U ri = {u L ,u1,…,u l ,…,u (L-1) }, and according to the initial position t of the first pseudo code symbol p1(1) of the first pseudo code signal in the complex envelope signal sequence x tmp Continuously extract L complex envelope signals from the complex envelope signal sequence x (4b) The three PMF-FFT modules in the three composite modules respectively calculate U le and O, U m and O, U ri Perform PMF-FFT operation on O to obtain the three branch spectrum data F l 、F m 、F r The three peak detection units and spectrum enhancement modules are used to detect F l , F m , F r Perform peak detection and spectrum enhancement processing to obtain the maximum value Fl of the three branch corrected frequency domain modulus values cmax 、Fm cmax and Fr. cmax ; (4c) The pseudo-code positioning output unit corrects the maximum frequency domain modulus value Fl through three branches cmax 、Fm cmax and Fr. cmax Determine the exact starting position t1 of the first pseudo code symbol p1(1) of the first pseudo code signal y(1) in the complex envelope signal sequence x, and calculate the exact starting position t1 of the first pseudo code symbol of the remaining K-1 pseudo code signals in the complex envelope signal sequence x based on t1 k , 2≤k≤K, t1 and the remaining K-1 precise starting positions are used as the synchronization results of the DSSS pseudo code signal, where: if Fm cmax >Fl cmax ,Fm cmax >Fr cmax ,t1=t tmp ; If Fl cmax > Fm cmax , Fl cmax > Fr cmax , t1 = t tmp -1; Fr cmax >Fm cmax ,Fr cmax >Fl cmax ,t1=t tmp +1; t k =t1+(k-1)*K*L-1,2≤k≤K.

8. The method according to claim 4, characterized in that The maximum value Fl of the three branch corrected frequency domain modulus values ​​in step (4b) cmax 、Fm cmax and Fr. cmax , the acquisition steps are: (4b1) The three cross-correlation units of the three PMF-FFT modules in the three composite modules respectively calculate U le and O, U m and O, U ri Perform cross-correlation operation on the elements at the corresponding positions in O to obtain a cross-correlation result sequence R containing L cross-correlation results. ulo , R umo , R uro ; The three segmented summing units respectively ulo , R umo , R uro Divide the bits into Z segments, and calculate the sum of the cross-correlation results in each segment, and obtain a sequence S containing Z cross-correlation summation results. Rlo , S Rmo , S Rro ; The three zero-filling units respectively sum the three cross-correlation result sequences S containing Z elements Rlo , S Rmo , S Rro , respectively, perform the post-filling (WZ) zero operations to obtain the zero-filled sequence SC of the cross-correlation summation result containing W elements Rlo , SC Rmo , SC Rro ; The three FFT operation units perform SC Rlo , SC Rmo , SC Rro The sequence is subjected to W-point FFT operation to obtain three branch spectrum data F each containing W elements. l 、F m 、F r ; (4b2) The three peak detection units respectively detect the three branch spectrum data F l 、F m 、F r The maximum value of the modulus of the W elements is detected, and the three maximum modulus values ​​are respectively in F l 、F m 、F r The position w in lmax 、w mmax 、w rmax , and then take out the maximum value of the three branch spectrum data modulus and the frequency domain data modulus of the left and right elements |F l (w lmax )|、|F l (w lmax -1)|、|F l (w lmax +1)| and|F m (w mmax )|、|F m (w mmax -1)|、|F m (w mmax +1)| and|F r (w rmax )|、|F r (w rmax -1)|、|F r (w rmax +1)|; (4b3) The three correction coefficient calculation units in the three spectrum enhancement modules are connected by |F l (w lmax -1)|、|F l (w lmax )|、|F l (w lmax +1)| and|F m (w mmax -1)|、|F m (w mmax )|、|F m (w mmax +1)| and|F r (w rmax -1)|、|F r (w rmax )|、|F r (w rmax +1)|, calculate the correction coefficients δ of the three branches l , δ m , δ r ; The three spectrum peak correction units are respectively l , δ m , δ r Calculate the maximum value Fl of the three branch corrected frequency domain modulus cmax 、Fm cmax , Fr cmax : Where π represents the ratio of a circle to a circle, and tan(·) represents the calculated tangent value.

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