A digital multi-beamforming method based on multi-domain joint

Abstract

The present invention discloses a digital multi-beam forming method based on multi-domain combination. The multi-domain combined digital multi-beam technology is adopted, and the space-time two-dimensional domain is used for joint anti-interference. A constraint vector pointing to the satellite is formed according to the satellite direction information and array flow, so that the beam formed after anti-interference is aligned with the satellite direction, and a null is formed in the interference direction while protection can be formed in the useful signal direction, so that the signal processing gain brought by the antenna array can be utilized while the interference is suppressed, thereby improving the signal-to-noise ratio of the satellite signal. The broadband correction technology is used for time domain compensation, and the in-band amplitude and phase inconsistency brought by the hardware is corrected, thereby avoiding the influence of the carrier phase difference between different beams brought by the time domain of the space-time multi-beam technology. While improving the anti-interference performance, the positioning accuracy of the multi-beam signal is guaranteed, and the requirement for the hardware in-band consistency is reduced, so that the space-time multi-beam algorithm is simple and feasible in engineering applications.

Description

Technical Field

[0001] The present invention relates to the technical field of signal processing, and in particular to a digital multi-beamforming method based on multi-domain combination. Background Art

[0002] With the increasing demand for anti-interference antennas in the navigation field, the commonly used satellite navigation receiver antennas are adaptive controllable directional pattern antennas, also called adaptive nulling antennas. This technology does not consider the direction of the satellite. While receiving all navigation signals from the air, it also receives all interference signals in the frequency band it covers, and then uses space-time joint array anti-interference technology to suppress interference. The power inversion algorithm is commonly used in engineering. The advantage of this method is that it does not require knowing the direction of the satellite signal or the array current to achieve the purpose of suppressing interference. It is a blind adaptive beamforming method with simple implementation and good compatibility with ordinary receivers. The algorithm can only suppress interference, but cannot make the main lobe of the antenna's directional pattern align with the direction of the satellite signal, that is, it cannot provide the signal processing gain brought by the antenna array. Therefore, the disadvantage of this method is that while suppressing interference, the useful signal may also be suppressed. In severe cases, it will affect the performance of the receiver and make it impossible to locate. In addition, the signal processing gain brought by the antenna array is wasted. The minimum variance distortionless response (MVDR) beamformer is commonly used in engineering, which is generally implemented in a pure air domain, but its anti-interference ability is limited and its time domain performance is not utilized. However, the space-time multi-beam technology has high requirements on hardware performance and needs to maintain sufficiently high amplitude and phase consistency within the entire useful signal bandwidth. It is difficult to meet its requirements in general hardware implementation, thus restricting its application in engineering. Summary of the invention

[0003] The technical problem to be solved by the present invention is that the main lobe of the antenna's directional pattern cannot be aligned with the direction of the satellite signal, the useful signal cannot be located, and the anti-interference ability is limited. The purpose is to provide a digital multi-beam forming method based on multi-domain joint, which performs joint anti-interference in the space-time two-dimensional domain, forms a null in the interference direction, and can also form protection in the useful signal direction, thereby achieving the purpose of suppressing interference while improving the signal-to-noise ratio of the useful signal.

[0004] The present invention is achieved through the following technical solutions:

[0005] A digital multi-beam forming method based on multi-domain joint, characterized by comprising the following steps:

[0006] S1. Acquire a sampling signal, perform an orthogonal transformation on the sampling signal, perform broadband correction on the sampling signal after the orthogonal transformation, and perform space-time conversion on the sampling signal after the broadband correction to obtain a space-time signal;

[0007] S2, calculating the sampling covariance matrix of the space-time signal;

[0008] S3. Calculate the spatial steering vector according to the signal direction information, and perform time domain delay on the spatial steering vector to obtain the space-time constraint vector;

[0009] S4, calculating the weight of the optimal beamformer according to the result of calculating the sampling covariance matrix of the space-time signal and the space-time constraint vector;

[0010] S5, filtering and weighting the space-time two-dimensional domain signal by the weight of the optimal beamformer to obtain an output signal after beamforming;

[0011] S6. Perform automatic gain control on the output signal to obtain the desired signal amplitude.

[0012] The present invention adopts a multi-domain combined digital multi-beam technology and utilizes the space-time two-dimensional domain for joint anti-interference. Secondly, a constraint vector pointing to the satellite can be formed according to the satellite direction information and the array flow, so that the beam formed after anti-interference is aligned with the satellite direction, forming a null in the interference direction while also forming protection in the useful signal direction, thereby achieving interference suppression while utilizing the signal processing gain brought by the antenna array, thereby improving the signal-to-noise ratio of the satellite signal, and using broadband correction technology for time domain compensation to correct the in-band amplitude and phase inconsistency brought by hardware, thereby avoiding the influence of the carrier phase difference between different beams brought by the time domain of the space-time multi-beam technology. While improving the anti-interference performance, it also meets the positioning performance of the multi-beam receiver, ensures the positioning accuracy of the multi-beam signal, reduces the requirement for hardware in-band consistency, enhances the practicability of engineering applications, and makes the space-time multi-beam algorithm simple and feasible in engineering applications.

[0013] As a further limitation of the present invention, obtaining the sampling signal specifically includes:

[0014] Set the transmission signal frequency and bandwidth parameters, and set the transmitting antenna and the receiving antenna to be in the same straight line, that is, the transmission signal of the transmitting antenna is normally incident relative to the receiving antenna;

[0015] M AD sampling signals from M antennas are obtained and orthogonally transformed to obtain I and Q signals with phase and amplitude information, where M is a positive integer.

[0016] As a further limitation of the present invention, the transmission signal frequency is set to be consistent with the incident signal center frequency, and the bandwidth parameter is set to be consistent with the useful signal bandwidth parameter.

[0017] As a further limitation of the present invention, the broadband correction of the sampling signal is performed by taking the AD sampling signal of a certain array element as a reference signal and using a matrix inversion algorithm to correct the amplitude and phase differences between channels.

[0018] As a further limitation of the present invention, the space-time conversion of the broadband corrected sampling signal to obtain the space-time signal includes delaying the spatial domain signal in the time domain to obtain the space-time signal formed by the antenna receiving signal.

[0019] As a further limitation of the present invention, the broadband correction specifically includes:

[0020] T1, the reference channel is set to the first AD sampling to obtain the I / Q signal, and the channel signal to be corrected is delayed to obtain the time domain filtering signal;

[0021] T2, calculate the autocorrelation matrix and cross-correlation vector of the time domain filtered signal;

[0022] T3. Calculate the time domain correction filter coefficients according to the autocorrelation matrix and the cross-correlation vector of the time domain filtering signal, and use the correction filter coefficients to filter the signal to obtain a corrected filtering signal.

[0023] As a further limitation of the present invention, after obtaining the correction filter coefficient, the reference channel gives a correction completion valid flag:

[0024] If the calibration completion flag is valid, the calibration coefficient of each channel is W 0 ,W 1 ,W 2 ...W M-1 , where W 0 =[0,0,0,1,0,0,0] T ;

[0025] If the calibration completion flag is invalid, the calibration coefficient W of each channel 0 ,W 1 ,W 2 ...W M-1 All are [0,0,0,1,0,0,0] T .

[0026] As a further limitation of the present invention, the calculating of the corrected filtered signal includes obtaining a time-domain filtered signal with the time-domain correction filter coefficients transposed.

[0027] As a further limitation of the present invention, S3 specifically includes:

[0028] U1. Establish a lookup table according to the incoming direction information to obtain the phase value of each azimuth and elevation angle of M array elements, where M is a positive integer;

[0029] U2. Calculate the spatial steering vector according to the phase value of each array element corresponding to the incoming direction information;

[0030] U3, calculate the time domain delay value;

[0031] U4. Calculate the space-time constraint vector according to the time domain delay value.

[0032] As a further limitation of the present invention, the U4 specifically includes:

[0033] V1, obtain the time domain delay value;

[0034] V2, obtaining a delay vector formed by N tap delay values ​​according to the time domain delay value, where N is a positive integer;

[0035] V3. Calculate the space-time constraint vector based on the delay vector formed by the spatial steering vector and N tap delay values.

[0036] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0037] 1. Obtain an IQ signal with amplitude and phase through orthogonal transformation to provide phase information for subsequent broadband correction and anti-interference algorithms;

[0038] 2. The amplitude and phase differences within the hardware band are corrected through broadband correction. The signal is delayed in the time domain to obtain a time domain tap signal. The signal is filtered using the correction filter coefficient to obtain the corrected signal, thus compensating for the amplitude and phase differences within the hardware band.

[0039] 3. Broadband correction uses the method of directly inverting the sampled data to improve the calculation accuracy while avoiding the algorithm implementation complexity of frequency domain multi-stage filtering.

[0040] 4. The time-domain steering vector delay value and the time-domain tap value are known quantities, so the calculation of the time-domain delay value does not require FPGA to calculate in real time, reducing hardware computing requirements.

[0041] 5. The space-time MVDR beamformer has higher anti-interference performance than the spatial domain beamformer. It can improve the signal gain after beamforming while ensuring the anti-interference performance.

[0042] 6. The weight calculation of the optimal beamformer eliminates the calculation of an amplitude control value and only requires matrix and steering vector operations, avoiding complex matrix operations and division operations in the FPGA. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be regarded as limiting the scope. For those of ordinary skill in the art, other relevant drawings can be obtained based on these drawings without creative work. In the drawings:

[0044] Figure 1is a flowchart of a digital multi-beamforming method based on multi-domain joint in an embodiment of the present invention;

[0045] Figure 2 This is a broadband correction method in an embodiment of the present invention;

[0046] Figure 3 is a block diagram of a broadband correction process in an embodiment of the present invention;

[0047] Figure 4 This is a flow chart for implementing a space-time multi-beam algorithm in an embodiment of the present invention;

[0048] Figure 5 A graph is generated for converting a spatial domain signal into a space-time signal in an embodiment of the present invention. DETAILED DESCRIPTION

[0049] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with embodiments and drawings. The exemplary embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention.

[0050] Example 1

[0051] like Figure 1 As shown, this embodiment provides a digital multi-beamforming method based on multi-domain joint, characterized in that it includes the following steps:

[0052] S1. Acquire a sampling signal, perform an orthogonal transformation on the sampling signal, perform broadband correction on the sampling signal after the orthogonal transformation, and perform space-time conversion on the sampling signal after the broadband correction to obtain a space-time signal;

[0053] S2, calculating the sampling covariance matrix of the space-time signal;

[0054] S3. Calculate the spatial steering vector according to the signal direction information, and perform time domain delay on the spatial steering vector to obtain the space-time constraint vector;

[0055] S4, calculating the weight of the optimal beamformer according to the result of calculating the sampling covariance matrix of the space-time signal and the space-time constraint vector;

[0056] S5, filtering and weighting the space-time two-dimensional domain signal by the weight of the optimal beamformer to obtain an output signal after beamforming;

[0057] S6. Perform automatic gain control on the output signal to obtain the desired signal amplitude.

[0058] By adopting multi-domain combined digital multi-beam technology, joint anti-interference is performed in the space-time two-dimensional domain. Secondly, a constraint vector pointing to the satellite can be formed according to the satellite's incoming information and array flow, so that the beam formed after anti-interference is aligned with the satellite's incoming direction, forming a null in the interference direction while also forming protection in the direction of useful signals. Thus, the signal processing gain brought by the antenna array can be utilized while suppressing interference, thereby improving the signal-to-noise ratio of the satellite signal. Wideband correction technology is used for time domain compensation to correct the in-band amplitude and phase inconsistency brought by the hardware, thereby avoiding the influence of the carrier phase difference between different beams brought by the time domain of the space-time multi-beam technology. While improving the anti-interference performance, it also meets the positioning performance of the multi-beam receiver, ensures the positioning accuracy of the multi-beam signal, reduces the requirements for hardware in-band consistency, enhances the practicability of engineering applications, and makes the space-time multi-beam algorithm simple and feasible in engineering applications.

[0059] In some possible embodiments, obtaining the sampling signal specifically includes: setting the transmission signal frequency and bandwidth parameters, setting the transmitting antenna and the receiving antenna on the same straight line, that is, the transmission signal of the transmitting antenna is normally incident relative to the receiving antenna; obtaining M AD sampling signals of M antennas for orthogonal transformation, and obtaining I and Q signals with phase and amplitude information, where M is a positive integer. Calculating the corrected filtered signal includes obtaining the time domain filtered signal under the transposition of the time domain correction filter coefficient. The IQ signal with amplitude and phase is obtained by orthogonal transformation, and the phase information is provided for the subsequent broadband correction and anti-interference algorithm; the transmission signal frequency is set to be consistent with the incident signal center frequency, and the bandwidth parameter is set to be consistent with the useful signal bandwidth parameter. The useful signal refers to the signal that transmits the information required by the user, and the sampling signal is subjected to broadband correction by using the AD sampling signal of a certain array element as the reference signal, and using the matrix inversion algorithm to correct the amplitude and phase differences between channels. The space-time conversion of the broadband corrected sampling signal to obtain the space-time signal includes delaying the spatial domain signal in the time domain to obtain the space-time signal formed by the antenna receiving signal.

[0060] In some possible embodiments, the broadband correction specifically includes:

[0061] T1, the reference channel is set to the first AD sampling to obtain the I / Q signal, and the channel signal to be corrected is delayed to obtain the time domain filtering signal;

[0062] T2, calculate the autocorrelation matrix and cross-correlation vector of the time domain filtered signal;

[0063] T3. Calculate the time domain correction filter coefficients according to the autocorrelation matrix and the cross-correlation vector of the time domain filtering signal, and use the correction filter coefficients to filter the signal to obtain a corrected filtering signal.

[0064] The amplitude and phase differences within the hardware band are corrected through broadband correction. The signal is delayed in the time domain to obtain the time domain tap signal. The signal is filtered using the correction filter coefficient to obtain the corrected signal, which makes up for the amplitude and phase differences within the hardware band. Broadband correction uses the method of directly inverting the sampled data to improve the calculation accuracy and avoid the algorithm implementation complexity of frequency domain multi-stage filtering. After obtaining the correction filter coefficient, the reference channel gives a correction completion valid flag: If the correction completion flag is valid, the correction coefficient of each channel is W 0 ,W 1 ,W 2 ...W M-1 , where W 0 =[0,0,0,1,0,0,0] T ; If the calibration completion flag is invalid, the calibration coefficient W of each channel 0 ,W 1 ,W 2 ...W M-1 All are [0,0,0,1,0,0,0] T .

[0065] In some possible embodiments, S3 specifically includes:

[0066] U1. Establish a lookup table based on the incoming direction information to obtain the phase value of each azimuth and elevation angle of M array elements, where M is a positive integer;

[0067] U2. Calculate the spatial steering vector according to the phase value of each array element corresponding to the incoming direction information;

[0068] U3, calculate the time domain delay value;

[0069] U4. Calculate the space-time constraint vector according to the time domain delay value.

[0070] U4 specifically includes:

[0071] V1, obtain the time domain delay value;

[0072] V2, obtaining a delay vector formed by N tap delay values ​​according to the time domain delay value, where N is a positive integer;

[0073] V3. Calculate the space-time constraint vector based on the delay vector formed by the spatial steering vector and N tap delay values.

[0074] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0075] In some possible embodiments, the center frequency of the intermediate frequency, the number of delay points, and the time domain tap value are all known quantities, so the calculation of the time domain delay value does not require the FPGA to calculate in real time, reducing hardware computing requirements.

[0076] In some possible embodiments, the space-time MVDR beamformer has a higher anti-interference performance than the spatial domain beamformer, and can improve the signal gain after beamforming while ensuring the anti-interference performance.

[0077] In some possible embodiments, the weight calculation of the optimal beamformer omits the calculation of an amplitude control value and only requires matrix and steering vector operations, thereby avoiding complex matrix operations and division operations in the FPGA.

[0078] Example 2

[0079] like Figure 2 As shown, the transmission signal frequency is set to the incident signal center frequency, and the signal modulation mode is turned on. You can choose modulation modes such as BPSK or QPSK. The bandwidth parameters are consistent with the useful signal bandwidth parameters. Set the transmitting antenna and the receiving antenna on the same straight line, that is, q = 0°. At this time, the distance of the transmission signal to each array element is the same.

[0080] M array antennas have M AD sampling signals, and all the sampling signals are intermediate frequency sampling. Therefore, it is necessary to perform orthogonal transformation on the AD sampling signals to obtain I and Q signals with phase and amplitude information.

[0081] like Figure 3 As shown, the sampling signal is subjected to broadband correction. The AD sampling data of a certain array element is used as the reference signal, and the amplitude and phase differences between channels are corrected using the matrix inversion algorithm, which specifically includes:

[0082] (1) The reference channel is set to the first AD sampling to obtain the I / Q signal, denoted as S. The signal of the channel to be corrected is delayed to obtain the time domain filtered signal:

[0083] XX=[xx(n) xx(n-1) ... xx(n-p+1)] T

[0084] Where: P is the order of the time domain filter. In this solution, the P value is 7. The P value can be different under different hardware conditions. Where [] T Indicates vector transposition. If the width correction flag is valid, proceed to the next step.

[0085] (2) Calculate the autocorrelation matrix R of its signal X xx and the cross-correlation vector R xs , and its calculation formula is as follows:

[0086] Autocorrelation matrix R xx for:

[0087]

[0088] Cross-correlation vector Rxs for:

[0089] R xs =[xx 11 s * xx 12 s * … xx 1P s * ] T

[0090] Where: ∑ represents signal accumulation; [] H represents the conjugate transpose of a vector; * Indicates that the complex signal takes the conjugate. In this solution, the K value is 256. The K value may be different under different hardware conditions.

[0091] (3) Calculate the time domain correction filter coefficient W = [w 11 w 12 ... w 1P ] T , the time domain correction filter coefficient W is

[0092] W=R xx -1 *R xs

[0093] (4) Repeat the above steps to obtain the correction filter coefficient W 1 ,W 2 ...W M-1 , the reference channel gives a calibration completion valid flag, recorded as flag_valid, flag_valid is 1 for valid, and 0 for invalid.

[0094] (5) If flag_valid = 1, the correction coefficient of each channel is W 0 ,W 1 ,W 2 ...W M-1 , where W 0 =[0,0,0,1,0,0,0] T , otherwise W 0 ,W 1 ,W 2 ...W M-1 All are [0,0,0,1,0,0,0] T .

[0095] Calculate the corrected filtered signal, the corrected filtered signal is:

[0096] x i =W i H *XX i

[0097] Among them: XX i =[xx i (n) xx i (n-1) ... xx i (n-p+1)] T Filter the signal in the time domain.

[0098] like Figure 5 As shown, the corrected signal is transformed into space-time, and the spatial signal is delayed in time domain to obtain the space-time signal X formed by the M antenna receiving signals. 1 ,X 2 ,…,X M .

[0099] Where: X i =[x i (n),x i (n-1),...x i (n-N+1)] T , i takes values ​​between 0 and M-1.

[0100] The space-time signal is sampled into the covariance matrix R xx Calculate the sampling covariance matrix R xx for:

[0101]

[0102] Where: K represents the number of sampling points, KK in the scheme is 1024 sampling points, M represents the number of true elements, and N represents the number of time domain filter levels.

[0103] According to the signal information (θ, φ), θ represents the pitch angle and φ represents the azimuth angle. First, the spatial steering vector is calculated, and then the time domain delay is performed to form the space-time steering vector. The spatial steering vector a(θ 0 )The calculation formula is as follows

[0104]

[0105] Where: 0 represents the wavelength corresponding to the center frequency, (x n ,y n ,z n ) represents the coordinate value of array element n,

[0106] exp(j)=cos()+j*sin() is a complex value. Specifically:

[0107] (1) Spatial steering vector a(θ 0) involves complex calculations, which are often difficult to implement in FPGA. Therefore, in order to simplify its implementation complexity, a table lookup method is used to implement it. A lookup table is established based on the heading information (θ, φ). The stepping of the pitch and azimuth angles is 1 degree. Then the table lookup depth is 90*360=32400. The information stored in the table is the phase value of each azimuth and pitch angle. Its values ​​are as follows

[0108]

[0109] There are M array elements, so the phase values ​​of the M array elements need to be calculated according to the formula.

[0110] (2) Calculate the spatial steering vector based on the phase value, find out the phase value of each array element corresponding to the future information (θ, φ), and obtain ψ 1 ,ψ 2 ... M , and then calculate its spatial guidance vector a(θ,φ) according to the formula. The calculation formula is as follows

[0111] a(θ,φ)=[exp(ψ 1 ),exp(ψ 2 )...exp(ψ M )] H

[0112] (3) Calculate the time domain delay value, the calculation formula is as follows

[0113] t_dly=exp(j*2π*F C *(P-1)*t d / F S )

[0114] Among them: F C Indicates the center frequency of the intermediate frequency, F S Indicates the intermediate frequency sampling rate; t d It represents the number of delay points, P is the time domain tap value, and the tap value in this solution ranges from 1 to N. From the above formula, it can be seen that when the solution is determined, its time domain delay value is a fixed value, so it is generated in advance and saved.

[0115] (4) Using the known fixed time domain delay value, calculate the space-time constraint vector SP_avec. The calculation formula is as follows:

[0116] SP_avec=kron(a(θ,φ),T_avec_dly)

[0117] Where: T_avec_dly is the delay vector formed by N tap delay values ​​calculated based on the time domain delay value, recorded as T_avec_dly = [t_dly 1 ,t_dly2 ...t_dly N ] T , expressed as Kronecker multiplication.

[0118] According to the above, the sampling covariance matrix R xx and the space-time constraint vector SP_avec to calculate the optimal beamformer weight w op t, the calculation formula is as follows:

[0119]

[0120] This saves calculation Because this value is a constant, it only affects the magnitude of the weight amplitude but does not affect the zero depth.

[0121] The optimal beamformer weight w is obtained by opt The two-dimensional space-time domain signal is filtered and weighted to obtain the output signal y_out after beamforming. The calculation formula is as follows:

[0122] y_out=w opt H *Y

[0123] Where: Y = [X 1 ,X 2 ,…,X M ] T , X i To obtain the space-time signal vector in step 4, i takes a value between 1 and M.

[0124] Due to the formula A constant of the weight amplitude is omitted, so the desired amplitude can be obtained by performing automatic gain control (AGC) on the filtered signal.

[0125] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A digital multi-beamforming method based on multi-domain joint, characterized in that: The following steps are involved: S1. Acquire a sampling signal, perform an orthogonal transformation on the sampling signal, perform broadband correction on the sampling signal after the orthogonal transformation, and perform space-time conversion on the sampling signal after the broadband correction to obtain a space-time signal; S2, calculating the sampling covariance matrix of the space-time signal; S3, according to the signal direction information, calculate the spatial steering vector, and perform time domain delay on the spatial steering vector to obtain the space-time constraint vector; the S3 specifically includes: U1, establish a lookup table according to the direction information, obtain the phase value of each azimuth and pitch angle of M array elements, M is a positive integer; U2, calculate the spatial steering vector according to the phase value of each array element corresponding to the direction information; U3, calculate the time domain delay value; U4, calculate the space-time constraint vector according to the time domain delay value; the U4 specifically includes: V1, obtain the time domain delay value; V2, obtain the delay vector formed by N tap delay values ​​according to the time domain delay value; V3, calculate the space-time constraint vector according to the delay vector formed by the spatial steering vector and N tap delay values, N is a positive integer; S4, calculating the weight of the optimal beamformer according to the result of calculating the sampling covariance matrix of the space-time signal and the space-time constraint vector; S5, filtering and weighting the space-time two-dimensional domain signal by the weight of the optimal beamformer to obtain an output signal after beamforming; S6. Perform automatic gain control on the output signal to obtain the desired signal amplitude.

2. The digital multi-beamforming method based on multi-domain joint according to claim 1, characterized in that: The acquiring of the sampling signal specifically comprises: Set the transmission signal frequency and bandwidth parameters, and set the transmitting antenna and the receiving antenna to be in the same straight line, that is, the transmission signal of the transmitting antenna is normally incident relative to the receiving antenna; M AD sampling signals from M antennas are obtained and orthogonally transformed to obtain I and Q signals with phase and amplitude information, where M is a positive integer.

3. The digital multi-beamforming method based on multi-domain joint according to claim 2, characterized in that: The transmission signal frequency is set to be consistent with the incident signal center frequency, and the bandwidth parameter is set to be consistent with the useful signal bandwidth parameter.

4. The digital multi-beamforming method based on multi-domain joint according to claim 1, characterized in that: The broadband correction of the sampling signal is performed by taking the AD sampling signal of a certain array element as a reference signal and using a matrix inversion algorithm to correct the amplitude and phase differences between channels.

5. The digital multi-beamforming method based on multi-domain joint according to claim 1, characterized in that: The space-time conversion of the broadband corrected sampling signal to obtain the space-time signal includes delaying the spatial domain signal in the time domain to obtain the space-time signal formed by the antenna receiving signal.

6. The digital multi-beamforming method based on multi-domain joint according to claim 5, characterized in that: The broadband correction specifically includes: T1, the reference channel is set to the first AD sampling to obtain the I / Q signal, and the channel signal to be corrected is delayed to obtain the time domain filtering signal; T2, calculate the autocorrelation matrix and cross-correlation vector of the time domain filtered signal; T3. Calculate the time domain correction filter coefficients according to the autocorrelation matrix and the cross-correlation vector of the time domain filtering signal, and use the correction filter coefficients to filter the signal to obtain a corrected filtering signal.

7. The digital multi-beamforming method based on multi-domain joint according to claim 6, characterized in that: After obtaining the correction filter coefficient, the reference channel gives a correction completion valid flag: If the calibration completion flag is valid, the calibration coefficients of each channel are W0, W1, W2...W M-1 , where W0=[0,0,0,1,0,0,0] T ; If the calibration completion flag is invalid, the calibration coefficients W0, W1, W2...W of each channel are M-1 All are [0,0,0,1,0,0,0] T .

8. The digital multi-beamforming method based on multi-domain joint according to claim 6, characterized in that: The corrected filtered signal includes a time domain filtered signal obtained by transposing the time domain correction filter coefficients.

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