CN112187315A - Large-scale spread spectrum communication digital array simultaneous multi-user rapid angle estimation method - Google Patents
Large-scale spread spectrum communication digital array simultaneous multi-user rapid angle estimation method Download PDFInfo
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Abstract
The invention provides a method for estimating angles of a large-scale spread spectrum communication digital array and multiple users simultaneously and quickly, which can carry out accurate and quick two-dimensional angle estimation and tracking on X users simultaneously in a large field angle range. The angle estimation and tracking method comprises the following steps: the separation of multi-user angle measurement is realized by using code division multiple access; the time domain coherent accumulation and the fast angle rough estimation in the spatial domain wide angle range are realized through the FFT of three dimensions; angle fine estimation is realized through incoherent accumulation and difference monopulse angle measurement; and realizing angle tracking through a quadratic smoothing regularization algorithm. All X users independently perform angle estimation and tracking. The invention adopts a step-by-step method of rough measurement, accurate measurement and tracking, has small calculated amount, high speed, large angle measurement coverage area and high angle measurement precision, and is suitable for the application fields of satellite communication, ground data link communication and the like.
Description
Technical Field
The invention belongs to the field of communication, and particularly relates to a simultaneous multi-user rapid angle estimation method for a large-scale spread spectrum communication digital array.
Background
The field angle (namely the pitch angle) of a low orbit (LEO) communication satellite to the ground is large, the angular speed of a ground user relative to a satellite antenna is high, the longest continuous communication time of a single satellite to the ground does not exceed 10 minutes, and the field angle change to the ground during communication maximally exceeds 100 degrees. In order to realize the ground communication at any position in a large field angle range, the early satellite-borne antenna adopts a low-gain weak directional antenna or a simple shaped beam antenna, and along with the expansion of the application field of LEO satellite communication and the improvement of the communication quality and speed requirements, the requirement on a high-gain antenna with flexible direction is more and more urgent. The large-scale digital array antenna adopting the digital beam forming technology has the characteristics of high-gain multi-beam forming and airspace self-adaptive anti-interference at the same time, and is the development direction of a satellite communication system. The antenna beam gain is improved along with the increase of the array scale, and meanwhile, the beam width is reduced, so that the accurate beam pointing and user tracking are always ensured in the whole communication process, and therefore, the high-precision user tracking becomes a key technology for the quick user positioning of a large-scale digital array.
Currently, common angle measurement methods based on digital array antennas are mainly classified into two categories: linear spectrum estimation and non-linear spectrum estimation. The linear spectrum estimation method includes: the interferometer method and the amplitude-contrast angle measurement method have the advantages of high angle measurement speed and simple process realization, but the angle measurement precision is not high due to the limitation of Rayleigh limit, the respective accurate positioning of two targets with small angle difference is difficult to realize, and a plurality of targets in one beam width are difficult to accurately position. The nonlinear spectrum estimation method comprises the following steps: the MUSIC algorithm, the ESPRIT algorithm and the like can break through the limitation of Rayleigh limit due to the angle measurement precision of the algorithms, are also called as super-resolution estimation algorithms, but have large computation amount and complex engineering implementation, and meanwhile, various non-ideal factors of a digital array system can greatly influence the estimation performance of the algorithms, such as channel amplitude inconsistency, array element position error, mutual coupling between unit antennas, gain inconsistency and the like.
In addition, a sum difference monopulse angle measurement method for simultaneously forming multiple beams to cover a large field angle two-dimensional space by adopting a digital beam forming technology is also provided, if a narrow beam is used for directly covering an angle measurement range, a large number of beams are needed, and sum difference monopulse angle measurement is carried out on every two adjacent beams, so that the calculation amount is large; if the wide and narrow beams are used for covering the angle measurement range respectively for step-by-step angle estimation, the coarse measurement precision can be obviously reduced due to the low gain of the wide beams, and the performance of the narrow beam fine measurement is influenced; in addition, the directional diagram and the beam number of the wide beam need to be comprehensively optimized according to the requirements of the array structure and the rough measurement precision, and the optimization result is difficult to achieve the optimum. And the adaptability of the method to the array structure is poor, and particularly for large-scale arrays, the optimization process is very complex. Therefore, there is a need for an angle estimation method suitable for large-scale arrays, with a strong adaptability of the array structure, which can significantly simplify the beam optimization process and achieve complex degree while achieving multi-objective, fast and high precision, but there is no related introduction in the prior art.
The invention content is as follows:
the invention aims to provide a quick angle estimation problem for burst communication users at any position.
The technical solution for realizing the invention is as follows: a large-scale spread spectrum communication digital array simultaneous multi-user rapid angle estimation method comprises the following steps:
step 1: using spread spectrum code distributed by each user to receive baseband signal x (t) ═ x of L array elements in digital array1(t),x2(t),…,xL(t)]TPerforming despreading processing, wherein xi(t) the baseband signal received by the ith array element is shown, and X groups of despread array baseband signals y are obtainedx(t)＝[yx1(t),yx2(t),…,yxL(t)]T(x＝1,2,…,X)；
Step 2: for the time period of communication link establishment, the array baseband signal yx(t) (X is 1,2, …, X) FFT in three dimensions to realize coherent accumulation in time domain and fast rough estimation of angle in wide angle range in space domainThe method comprises the following steps: for yx(t) (X is 1,2, …, X) time domain data of each array element is subjected to P-point FFT, and L array element accumulated data z are obtained by selecting FFT processing resultsx(l) (X ═ 1,2, …, X ═ 1,2, …, L); to zx(l) Performing data rearrangement and K-K point two-dimensional FFT, and performing peak search and interpolation processing to obtain user angle rough estimation (u)Coarse,vCoarse)；
And step 3: after entering the communication data transmission stage, the baseband data y after array element level de-spreading is usedx(t) (X is 1,2, …, X) performing sum-difference monopulse angle estimation based on Q-point incoherent accumulation to obtain accurate angle estimation value (u)Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials)；
And 4, step 4: for (u) obtained continuously in step 3Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials) Obtaining an angle tracking result (u) by adopting a quadratic smoothing regularization approximation angle tracking algorithmt,vt) And returning to the step 3 until one communication of the user is finished.
Compared with the prior art, the invention has the following remarkable advantages: (1) the space domain information is converted into a beam domain by utilizing fast Fourier transform, the two-dimensional angle initial range of a user can be quickly determined by utilizing peak search, the full coverage of the space domain angle is observed, the calculation real-time performance is high, the gain of the array antenna is fully utilized, and the angle measurement precision is optimized. (2) The method effectively avoids the limitation of the traditional multi-target angle estimation algorithm on the angle resolution and the limitation of the single-pulse angle estimation algorithm on the multi-target angle estimation. (3) In the formal communication stage, only 1 sum beam and 2 direction difference beams are needed, the accurate angle of the user can be obtained at one time by matching with the angle tracking algorithm with low computation amount, a large number of sum and difference beams are not needed to be generated, and the rapid large-field-angle target angle searching and tracking are realized. (4) The array structure has strong adaptability, and a beam directional diagram and the number of beams do not need to be greatly optimized aiming at the arrays with different array element numbers and array element arrangement structures, so that the complexity of the beam optimization process and the engineering realization is obviously reduced.
The present invention will be described in further detail with reference to the accompanying drawings.
Description of the drawings:
figure 1 is a flow chart of simultaneous multi-user angle estimation of the present invention.
Fig. 2 is a triangular grid array structure employed in the embodiment.
Fig. 3 is a schematic diagram of beam coverage when the two-dimensional FFT angle rough estimate K is 10 in the present invention.
Fig. 4 is a two-dimensional FFT normalized amplitude plot without interpolation when the signal is incident from the wavefront normal, at K10.
Fig. 5 is a three-dimensional amplitude map of a two-dimensional FFT angle rough estimate when K is 10.
Fig. 6 is a simulation curve of interpolation of two-dimensional FFT angle estimation errors at different target angle positions after 100 statistical experiments when the array element level SNR is-13 dB.
Fig. 7 is a sum beam three-dimensional pattern when the target angle information (u, v) is (0,0) when the element antenna is an ideal isotropic omnidirectional antenna.
Fig. 8 is a cross-sectional view of a beam pattern in the V direction when the target angle information (U, V) is (0,0) and U is 0 when the unit antenna is an ideal isotropic omnidirectional antenna.
Fig. 9 is a U-direction difference beam three-dimensional pattern when the target angle information (U, v) is (0,0) when the unit antenna is an ideal isotropic omnidirectional antenna.
Fig. 10 is a V-direction difference beam three-dimensional pattern when the target angle information (u, V) is (0,0) when the element antenna is an ideal isotropic omnidirectional antenna.
Fig. 11 is a graph of U-direction and difference beam angle measurements when the target angle information (U, v) is (0,0) when the unit antenna is an ideal isotropic omni-directional antenna.
Fig. 12 is a graph of V-direction and difference beam angle measurements when the target angle information (u, V) is (0,0) when the unit antenna is an ideal isotropic omni-directional antenna.
FIG. 13 is a graph of angle estimation versus true angle error for non-coherent accumulation points Q varying from 1-128.
Fig. 14 is a simulation curve of the fine estimation error of different target angle positions and difference beam angles after 100 times of statistical experiments when the array element level SNR is-21 dB.
FIG. 15 is a graph of error before and after quadratic smoothing angle tracking filtering versus true angle.
Fig. 16 is a comparison of pitch angle direction quadratic smoothing before and after filtering and the true angle.
FIG. 17 is a graph comparing the pre-and post-azimuth direction quadratic smoothing filter with the true angle.
The specific implementation mode is as follows:
a large-scale spread spectrum communication digital array simultaneous multi-user fast angle estimation method comprises the following steps:
step 1: using spread spectrum code distributed by each user to receive baseband signal x (t) ═ x of L array elements in digital array1(t),x2(t),…,xL(t)]TDe-spread processing is carried out to obtain X groups of de-spread array baseband signals yx(t)＝[yx1(t),yx2(t),…,yxL(t)]T(X ═ 1,2, …, X), where X isi(t) represents the baseband signal received by the ith array element;
step 2: for the time period of communication link establishment, the array baseband signal yx(t) (X ═ 1,2, …, X) three-dimensional FFT to achieve time-domain coherent accumulation and fast coarse angle estimation over a wide angular range in space domain, comprising: for yx(t) (X is 1,2, …, X), performing P-point FFT on the time domain data of each array element, and selecting FFT results to obtain L array element accumulated data zx(l) (X ═ 1,2, …, X ═ 1,2, …, L); to zx(l) (X ═ 1,2, …, X;: L ═ 1,2, …, L) data rearrangement and K × K point two-dimensional FFT are performed, and the user angle rough estimate (u) is obtained by peak search and interpolation processingCoarse,vCoarse) (ii) a The method specifically comprises the following substeps:
step 2.1: for despread array baseband signal yx(t) (X is 1,2, …, X), performing a P-point FFT on the time domain data of each array element, and taking a value P to make the frequency interval of FFT output data
Wherein f issFor signal sampling frequency, fmaxThe maximum Doppler frequency offset residual error of the despread baseband signal is obtained;
step 2.2: recording the frequency point position of the maximum amplitude of the FFT result of each array element, and respectively selecting the FFT output results of L array elements at the position by taking the frequency point with the maximum recording times as a reference to obtain the data z after the time domain accumulation of the L array elementsx(l)(x＝1,2,…,X；l＝1,2,…,L)；
Step 2.3: for z after sorting and zero paddingx(l) Making K X K point two-dimensional FFT, which is equivalent to forming K X K point beams to cover the expected large field angle range to the ground at the same time, wherein K value is required to ensure that the interval alpha between two adjacent beams in the K X K point beams is less than or equal to (r.s), r is the beam width of the point beam 3dB, and s is the interpolation multiple of the amplitude network of the two-dimensional FFT result;
step 2.4: performing s-time interpolation processing on a symmetric space near the maximum coordinate of the amplitude of the two-dimensional FFT result to obtain amplitude information of at most b points,
step 2.5: the coordinates of the amplitude peak value after interpolation are taken, and the coordinates are converted into angle information under (U, V) coordinates according to the relation between a two-dimensional space spectrum and a wave number domain, so that a two-dimensional FFT angle measurement result (U, V) is obtainedCoarse,vCoarse)。
And step 3: after entering the communication data transmission stage, the angle rough estimation result (u) is utilizedCoarse,vCoarse) Or angle tracking results (u)t,vt) Using the despread baseband data y at the array element levelx(t) (X is 1,2, …, X) performing sum-difference monopulse angle estimation based on Q-point incoherent accumulation to obtain accurate angle estimation value (u)Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials) (ii) a The method specifically comprises the following substeps:
step 3.1: using the coarse estimation of the angle (u)Coarse,vCoarse) Or angle tracking result (u)t,vt) As the beam pointing angle, array baseband signals y after despreading by using L array elements in the normal communication stagex(t) (X ═ 1,2, …, X), simultaneously forming a sum beam, a U-direction difference beam, and a V-direction difference beam; the outputs of the three beams are y∑(q)、 yΔU(q) and yΔV(Q), Q is 1,2, …, Q, Q value needs to satisfy
Wherein
For the coarse estimation of the maximum error for the angle,
accumulating minimum gain, and beam weight w for non-coherence∑The difference beam weight w in the U, V direction for the steering vector pointing to the targetΔU、wΔVRespectively, sum beam weight w∑Derivatives to U, V;
step 3.2: and calculating the sum and difference beam single pulse ratios after incoherent accumulation, which are respectively as follows:
wherein Re (-) is the operation of the solid part;
step 3.3: calculating the value k of the angular slope in the U directionUV direction angle slope measurement value kV：
Wherein the content of the first and second substances,
and
are respectively (u)0±Δu,v0)、(u0,v0Vectorial vector at angle of + - Δ v (u)0,v0) For the current sum beam pointing angle, Δ u and Δ v are beam sum difference amplitude approximate linear intervals, and are generally smaller than half of the beam width of the sum beam 3 dB;
step 3.4: calculating to obtain a user angle accurate estimation value (u)Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials)，
And 4, step 4: for (u) obtained continuously in step 3Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials) Obtaining an angle tracking result (u) by adopting a quadratic smoothing regularization approximation angle tracking algorithmt,vt) And returning to the step 3 until one communication of the user is finished. The method specifically comprises the following substeps:
step 4.1: constructing regularization functions
And minimize it to give the current betajWhere j represents the number of filtering times, βjFor the jth filtered output value,
accurately measuring an output value for the jth filtering input, namely the sum and difference wave beams;
representing the constraint that the filter output differs from the filter input,
representing the constraint of the variation speed of the filter output value, J, respectively representing the length of a filter window and a penalty coefficient, and the value is less than 20;
step 4.2 obtaining angle tracking results (u) by respectively adopting the quadratic smoothing regularization approximation algorithm in the direction U, Vt,vt) Separately, U, V th angle estimates are obtained, and the j-th filtered output obtained in the process is used as the j +1 th sum-difference beam angle estimation input (u)0,v0)＝(ut,vt)。
A large-scale spread spectrum communication digital array simultaneous multi-user fast angle estimation system comprises:
the de-spreading module is used for de-spreading the baseband signals received by the array elements in the digital array to obtain de-spread array baseband signals;
the angle rough estimation module is used for realizing time domain coherent accumulation and rapid angle rough estimation in a space domain wide angle range by performing FFT of three dimensions on the despread array baseband signal;
the angle fine estimation module is used for carrying out sum-difference single pulse angle estimation based on Q point incoherent accumulation by using the baseband data subjected to array element-level de-spreading by using an angle coarse estimation result or an angle tracking result after entering a communication data transmission stage to obtain an accurate angle estimation value;
and the angle tracking module is used for obtaining an angle tracking result by adopting a secondary smooth regularization approximation angle tracking algorithm for the fine angle estimation, and the angle tracking result is used as a user angle tracking value and a pointing basis of a next tracking beam until the end of primary communication of the user.
A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, the processor implementing the following steps when executing the computer program:
step 1: using spread spectrum code distributed by each user to receive baseband signal x (t) ═ x of L array elements in digital array1(t),x2(t),…,xL(t)]TPerforming despreading processing, wherein xi(t) the baseband signal received by the ith array element is shown, and X groups of despread array baseband signals y are obtainedx(t)＝[yx1(t),yx2(t),…,yxL(t)]T(x＝1,2,…,X)；
Step 2: for the time period of communication link establishment, the array baseband signal yx(t) (X ═ 1,2, …, X) three-dimensional FFT to achieve time-domain coherent accumulation and fast coarse angle estimation over a wide angular range in space domain, comprising: for yx(t) (X is 1,2, …, X) time domain data of each array element is subjected to P-point FFT, and L array element accumulated data z are obtained by selecting FFT processing resultsx(l) (X ═ 1,2, …, X ═ 1,2, …, L); to zx(l) Performing data rearrangement and K-K point two-dimensional FFT, and performing peak search and interpolation processing to obtain user angle rough estimation (u)Coarse,vCoarse)；
And step 3: after entering the communication data transmission stage, the baseband data y after array element level de-spreading is usedx(t) (X is 1,2, …, X) performing sum-difference monopulse angle estimation based on Q-point incoherent accumulation to obtain accurate angle estimation value (u)Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials)；
And 4, step 4: for (u) obtained continuously in step 3Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials) Obtaining an angle tracking result (u) by adopting a quadratic smoothing regularization approximation angle tracking algorithmt,vt) And returning to the step 3 until one communication of the user is finished.
A computer-storable medium having stored thereon a computer program which, when executed by a processor, performs the steps of:
step 1: using spread spectrum code distributed by each user to receive baseband signal x (t) ═ x of L array elements in digital array1(t),x2(t),…,xL(t)]TPerforming despreading processing, wherein xi(t) the baseband signal received by the ith array element is shown, and X groups of despread array baseband signals y are obtainedx(t)＝[yx1(t),yx2(t),…,yxL(t)]T(x＝1,2,…,X)；
Step 2: for the time period of communication link establishment, the array baseband signal yx(t) (X ═ 1,2, …, X) three-dimensional FFT to achieve time-domain coherent accumulation and fast coarse angle estimation over a wide angular range in space domain, comprising: for yx(t) (X is 1,2, …, X) time domain data of each array element is subjected to P-point FFT, and L array element accumulated data z are obtained by selecting FFT processing resultsx(l) (X ═ 1,2, …, X ═ 1,2, …, L); to zx(l) Performing data rearrangement and K-K point two-dimensional FFT, and performing peak search and interpolation processing to obtain user angle rough estimation (u)Coarse,vCoarse)；
And step 3: after entering the communication data transmission stage, the baseband data y after array element level de-spreading is usedx(t) (X ═ 1,2, …, X) sum and difference monopulse angles based on Q-point incoherent accumulationEstimating to obtain accurate angle estimation value (u)Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials)；
And 4, step 4: for (u) obtained continuously in step 3Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials) Obtaining an angle tracking result (u) by adopting a quadratic smoothing regularization approximation angle tracking algorithmt,vt) And returning to the step 3 until one communication of the user is finished.
The present invention will be described in detail below with reference to the accompanying drawings and example 1
Examples
The invention is a method for carrying out accurate and rapid two-dimensional angle estimation and tracking on multiple users simultaneously aiming at a large-scale digital array spread spectrum communication system with large airspace coverage field angle, the flow of the method is shown in figure 1, and the method comprises 4 key steps: the separation of multi-user angle measurement is realized by using code division multiple access; the time domain coherent accumulation and the fast angle rough estimation in the spatial domain wide angle range are realized through the FFT of three dimensions; angle fine estimation is realized through incoherent accumulation and difference monopulse angle measurement; and realizing angle tracking through a quadratic smoothing regularization algorithm.
In example 1, a triangular lattice array structure having a radius of 0.57 λ (wavelength) and L of 143 is used, as shown in fig. 2. Assuming that there are 3 users, the step-by-step monopulse angular measurement method includes the steps of:
step 1: baseband signals x (t) ═ x received by 143 array elements in the digital array using spreading codes assigned to 3 users, respectively1(t),x2(t),…,x143(t)]TDe-spread processing is carried out to obtain 3 groups of de-spread array baseband signals yx(t)＝[yx1(t),yx2(t),…,yx143(t)]T(x＝1,2,3)。
Step 2: for the time period of communication link establishment, the array baseband signal yx(t) (x ═ 1,2,3) performing three-dimensional FFT to achieve time-domain coherent accumulation and fast coarse angle estimation in a spatial-wide angular range, comprising the following sub-steps:
step 2.1: for despread array baseband signal yx(t)(x＝1,2,3) performing P-point FFT on the time domain data of each array element, wherein the value P needs to ensure the frequency interval of FFT output data
Wherein f issFor signal sampling frequency, fmaxIn this embodiment, in order to despread the maximum doppler frequency offset residual of the baseband signal, the SNR of the array element level SNR in the time period established by the communication link is-13 dB, a 2DPSK modulation mode is adopted, and the code rate r of the despread baseband signal is the code rate rbMaximum doppler frequency offset residual f of 3Kbpsmax25Hz, the number P of array element-level time domain FFT points in this embodiment is 128;
step 2.2: recording the frequency point position of the maximum amplitude of the FFT result of each array element, and selecting the FFT processing result to obtain 143 array element accumulated data z by taking the frequency point with the maximum recording times as the referencex(l)(x＝1,2,3；l＝1,2,…,143)，
Step 2.3: for z after sorting and zero paddingx(l) Making K X K point two-dimensional FFT, equivalent to forming K X K point beams simultaneously to cover the expected large angle range to the ground, K value should make the interval alpha between two adjacent beams in K X K point beams less than or equal to (r.s), r is the beam width of the point beam 3dB, s is the interpolation multiple of the amplitude network of the two-dimensional FFT result, in this embodiment, the 3dB beam width of the digital array point beam of 143 array elements is about 10 degrees, the interpolation multiple s is 5, the number K of two-dimensional FFT points is 10,
step 2.4: performing s-time interpolation processing on a symmetric space near the maximum coordinate of the amplitude of the two-dimensional FFT result to obtain amplitude information of at most b points,
step 2.5: the coordinates of the amplitude peak value after interpolation are taken, and the coordinates are converted into angle information under (U, V) coordinates according to the relation between a two-dimensional space spectrum and a wave number domain, so that a two-dimensional FFT angle measurement result (U, V) is obtainedCoarse,vCoarse)；
The schematic diagram of beam coverage of the two-dimensional FFT angle rough estimation K-10 is shown in fig. 3, an effective angle measurement space with a pitch angle ± 55 ° is within a red circle, when a signal is incident from the normal direction of a wavefront, a two-dimensional FFT normalized amplitude map without interpolation is shown in fig. 4, a two-dimensional FFT amplitude map after interpolation is shown in fig. 5, and fig. 6 shows a simulation curve of interpolation of two-dimensional FFT angle estimation errors at different target angle positions when an array element level signal-to-noise ratio SNR is-13 dB.
And step 3: after entering the communication data transmission stage, the baseband data y after array element level de-spreading is usedx(t) (x is 1,2,3) performing sum-difference monopulse angle estimation based on Q-point incoherent accumulation to obtain an accurate angle estimation value (u)Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials) The method comprises the following substeps:
step 3.1: using the angle rough estimation result (u) obtained in step 2Coarse,vCoarse) Or the angle tracking result (u) obtained in step 4t,vt) As the beam pointing angle, the array baseband signal y after despreading by using L array elements in the normal communication stagex(t) (x is 1,2,3) simultaneously forming a sum beam, a U-direction difference beam, and a V-direction difference beam, and the outputs of the three beams are y∑(q)、yΔU(q) and yΔV(Q), Q ═ 1,2, …, Q. Q value is required to satisfy
Wherein
For the coarse estimation of the maximum error for the angle,
accumulating minimum gain, and beam weight w for non-coherence∑A difference beam weight w in the direction U, V for a vector of directionality towards the targetΔU、wΔVRespectively, sum beam weight w∑For the derivative of U, V, in this embodiment, the number of incoherent integration points Q is 128,
step 3.2: and calculating the sum and difference beam single pulse ratios after incoherent accumulation, which are respectively as follows:
wherein Re (-) is the operation of the solid part;
step 3.3: calculating the value k of the angular slope in the U directionUV direction angle slope measurement value kV：
Wherein the content of the first and second substances,
and
are respectively (u)0±Δu,v0)、(u0,v0A vector of guidance at an angle of ± Δ v); (u)0,v0) Pointing angles for the current sum beam; the delta u and delta v are approximately linear intervals of the sum and difference amplitudes, and are generally less than half of the beam width of the sum beam 3 dB.
Step 3.4: calculating to obtain a user angle accurate estimation value (u)Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials)，
When the target angle information (U, V) ((0 °,0 °)), the sum beam three-dimensional pattern is as in fig. 7, the cross-sectional views of the sum beam three-dimensional pattern and the beam direction are as in fig. 8, the U-direction and V-direction difference beam three-dimensional patterns are as in fig. 9 and 10, respectively, the U-direction, V-direction and difference beam angle measurement curves are as in fig. 11 and 12, respectively, the angle estimation result when the number of incoherent integration points Q changes from 1 to 128, the true angle error graph is as in fig. 13, and fig. 14 shows a simulation curve of the array element level SNR (signal-to-noise ratio) of-21 dB, the precise estimation error of different target angle positions and difference beam angles.
And 4, step 4: for (u) obtained continuously in step 3Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials) Obtaining an angle tracking result (u) by adopting a quadratic smoothing regularization approximation angle tracking algorithmt,vt) As the basis for the user angle tracking value and the pointing direction of the next tracking beam, then returning to step 3 until one communication of the user is finished, specifically comprising the following substeps:
step 4.1: constructing regularization functions
And minimizing it, wherein, betajFor the jth filtered output value,
accurately measuring an output value for the j filtering input, namely the sum and difference wave beam;
representing the constraint that the filter output differs from the filter input,
representing the constraint on how fast the filter output value changes. J. Respectively representing the length of a filter window and a penalty coefficient, wherein the values of the filter window and the penalty coefficient are less than 20;
step 4.2: respectively adopting the quadratic smoothing regularization approximation algorithm to obtain angle tracking results (u) in the direction U, Vt,vt). Separately, U, V angle estimates are obtained, and the jth filtered output obtained in the process is used as the next and difference beam angle estimate inputs (u)0,v0)＝(ut,vt)。
In this embodiment, the filter window length J is 5, the penalty factor is 20, the duration of the one-time complete communication process is about 7 minutes, the angle estimation update interval is about 1 second, an error graph between the real angle and the error graph before and after the second smoothing filtering is shown in fig. 15, a comparison graph between the real angle and the error graph before and after the second smoothing filtering in the pitch angle direction is shown in fig. 16, and a comparison graph between the real angle and the error graph before and after the second smoothing filtering in the azimuth angle direction is shown in fig. 17.
According to the technical scheme, the space domain information is converted into the wave number domain through fast Fourier transform, the two-dimensional angle preliminary range of a user can be rapidly determined by utilizing wave peak search, the space domain angle is observed to be fully covered, the calculation real-time performance is high, the array antenna gain is fully utilized, the angle measurement precision is optimized, the waveform characteristics of a communication link establishing stage and a formal communication stage in a satellite communication system are fully combined, and the rapid large-opening-angle target angle search and tracking are achieved. In the formal communication stage, only 1 sum wave beam and 2 direction difference wave beams are needed, the accurate angle of the user can be obtained at one time by matching with an angle tracking algorithm with low computation amount, a large number of sum and difference wave beams are not needed to be generated, the characteristics of code division multiple access of a spread spectrum communication system are fully utilized, baseband data after despreading of each user array element level are used for angle estimation, and the limitation of the angle resolution of the traditional multi-target angle estimation algorithm and the limitation of the single pulse angle estimation algorithm in realizing multi-target angle estimation are effectively avoided.
Claims (7)
1. A large-scale spread spectrum communication digital array simultaneous multi-user fast angle estimation method is characterized by comprising the following steps:
step 1: using spread spectrum code distributed by each user to receive baseband signal x (t) ═ x of L array elements in digital array1(t),x2(t),…,xL(t)]TDe-spread processing is carried out to obtain X groups of de-spread array baseband signals yx(t)＝[yx1(t),yx2(t),…,yxL(t)]T(X ═ 1,2, …, X), where X isi(t) denotes the baseband signal received by the i-th array element, yxi(t) a despread signal obtained by despreading the signal of the ith array element by using the xth group of spreading codes is shown;
step 2: for the time period of communication link establishment, the array baseband signal yx(t) (X ═ 1,2, …, X) three-dimensional FFT to achieve time-domain coherent accumulation and fast coarse angle estimation over a wide angular range in space domain, comprising: for yx(t) (X is 1,2, …, X), performing P-point FFT on the time domain data of each array element, and selecting FFT results to obtain L array element accumulated data zx(l) (X ═ 1,2,. times, X: 1,2, …, L); to zx(l) (X ═ 1,2, …, X;: L ═ 1,2, …, L) data rearrangement and K × K point two-dimensional FFT are performed, and the user angle rough estimate (u) is obtained by peak search and interpolation processingCoarse,vCoarse)；
And step 3: after entering the communication data transmission stage, the angle rough estimation result (u) is utilizedCoarse,vCoarse) Or angle tracking result (u)t,vt) Using the despread baseband data y at the array element levelx(t) (X is 1,2, …, X) performing sum-difference monopulse angle estimation based on Q-point incoherent accumulation to obtain accurate angle estimation value (u)Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials)；
And 4, step 4: for (u) obtained continuously in step 3Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials) Obtaining an angle tracking result (u) by adopting a quadratic smoothing regularization approximation angle tracking algorithmt,vt) And as the user angle tracking value and the pointing basis of the next tracking beam, returning to the step 3 until one communication of the user is finished.
2. The method for simultaneous multi-user fast angle estimation of large-scale spread spectrum communication digital array according to claim 1, wherein the implementation of time-domain coherent accumulation and fast angle rough estimation in a space-domain wide angle range by three-dimensional FFT in step 2 specifically comprises the following substeps:
step 2.1: for despread array baseband signal yx(t) (X is 1,2, …, X), performing a P-point FFT on the time domain data of each array element, and taking a value P to make the frequency interval of FFT output data
Wherein f issFor signal sampling frequency, fmaxThe maximum Doppler frequency offset residual error of the despread baseband signal is obtained;
step 2.2: recording the frequency point position of the maximum amplitude of the FFT result of each array element, and respectively selecting the FFT output results of L array elements at the position by taking the frequency point with the maximum recording times as a reference to obtain the data z after the time domain accumulation of the L array elementsx(l)(x＝1,2,…,X；l＝1,2,…,L)；
Step 2.3: for z after sorting and zero paddingx(l) Making K X K point two-dimensional FFT, which is equivalent to forming K X K point beams to cover the expected large field angle range to the ground at the same time, wherein K value is required to ensure that the interval alpha between two adjacent beams in the K X K point beams is less than or equal to (r.s), r is the beam width of the point beam 3dB, and s is the amplitude network interpolation multiple of the two-dimensional FFT result;
step 2.4: performing s-time interpolation processing on a symmetric space near the maximum coordinate of the amplitude of the two-dimensional FFT result to obtain amplitude information of at most b points,
step 2.5: the coordinates of the amplitude peak value after interpolation are taken, and the coordinates are converted into angle information under (U, V) coordinates according to the relation between a two-dimensional space spectrum and a wave number domain, so that a two-dimensional FFT angle measurement result (U, V) is obtainedCoarse,vCoarse)。
3. The method for simultaneous multi-user fast angle estimation of large-scale spread spectrum communication digital array according to claim 1, wherein the step 3 of performing incoherent accumulated sum-difference monopulse angle estimation to obtain an accurate angle estimation value comprises the following sub-steps:
step 3.1: using the coarse estimation of the angle (u)Coarse,vCoarse) Or angle tracking result (u)t,vt) As the beam pointing angle, array baseband signals y after despreading by using L array elements in the normal communication stagex(t) (X ═ 1,2, …, X), simultaneously forming a sum beam, a U-direction difference beam, and a V-direction difference beam; the outputs of the three beams are y∑(q)、yΔU(q) and yΔV(q)，q＝1,2, …, Q and Q values are required to satisfy
Wherein
For the coarse estimation of the maximum error for the angle,
accumulating minimum gain, and beam weight w for non-coherence∑A difference beam weight w in the direction U, V for a vector of directionality towards the targetΔU、wΔVRespectively, sum beam weight w∑Derivatives to U, V;
step 3.2: and calculating the sum and difference beam single pulse ratios after incoherent accumulation, which are respectively as follows:
wherein Re (-) is the operation of the solid part;
step 3.3: calculating the value k of the angular slope in the U directionUV direction angle slope measurement value kV：
Wherein the content of the first and second substances,
and
are respectively (u)0±Δu,v0)、(u0,v0Vectorial vector at angle of + - Δ v (u)0,v0) For the current sum beam pointing angle, Δ u and Δ v are beam sum difference amplitude approximate linear intervals, and are generally smaller than half of the beam width of the sum beam 3 dB;
step 3.4: calculating to obtain a user angle accurate estimation value (u)Extract of Chinese medicinal materials,vExtract of Chinese medicinal materials)，
4. The method for simultaneous multi-user fast angle estimation of a large-scale spread spectrum communication digital array according to claim 1, wherein the angle tracking result is obtained by adopting a quadratic smoothing regularization approximation angle tracking algorithm in the step 4, and the method comprises the following substeps:
step 4.1: constructing regularization functions
And minimize it to give the current betajWhere j is the number of filtering processes, βjFor the jth filtered output value,
accurately measuring an output value for the j filtering input, namely the sum and difference wave beam;
representing the constraint that the filter output differs from the filter input,
representing the constraint of the variation speed of the filter output value, J, respectively representing the length of the filter window and the penalty coefficient, and the value is less than 20;
step 4.2 obtaining angle tracking results (u) by respectively adopting the quadratic smoothing regularization approximation algorithm in the direction U, Vt,vt) Separately, U, V angle estimates are obtained, and the jth filtered output obtained in the process is used as the next and difference beam angle estimate inputs (u)0,v0)＝(ut,vt)。
5. A large-scale spread spectrum communication digital array simultaneous multi-user fast angle estimation system, comprising:
the de-spreading module is used for de-spreading the baseband signals received by the array elements in the digital array to obtain de-spread array baseband signals;
the angle rough estimation module is used for realizing time domain coherent accumulation and rapid angle rough estimation in a space domain wide angle range by performing FFT of three dimensions on the despread array baseband signal;
the angle fine estimation module is used for carrying out sum-difference single pulse angle estimation based on Q point incoherent accumulation by using the baseband data subjected to array element-level de-spreading by using an angle coarse estimation result or an angle tracking result after entering a communication data transmission stage to obtain an accurate angle estimation value;
and the angle tracking module is used for obtaining an angle tracking result by adopting a secondary smooth regularization approximation angle tracking algorithm for the fine angle estimation, and the angle tracking result is used as a user angle tracking value and a pointing basis of a next tracking beam until the end of primary communication of the user.
6. A computer arrangement comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the steps of the method as claimed in any one of claims 1 to 4 are implemented by the processor when executing the computer program.
7. A computer-storable medium having a computer program stored thereon, wherein the computer program is adapted to carry out the steps of the method according to any one of claims 1-4 when executed by a processor.
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