A signal direction estimation method based on multi-channel vector digital beamforming and amplitude comparison

Abstract

The application discloses a signal direction estimation method based on multi-channel vector digital beam forming and amplitude comparison, and belongs to the technical field of digital signal processing.The application solves the problem that the traditional digital beam forming algorithm cannot be applied to the direction finding of a conformal antenna array.The application specifically comprises the following steps: step one, arranging a conformal antenna array model composed of conformal antenna array elements;step two, performing vector digital beam forming on received polarized signals of the conformal antenna array model to form a plurality of beams with different directions;step three, searching the different direction beams formed in the step two, and searching out the polarized parameters and the incident direction corresponding to the maximum beam;step four, selecting three beams according to the polarized parameters and the incident direction searched out in the step three, and performing amplitude comparison on the selected three beams to obtain the final incident angle estimation result of the incident electromagnetic wave signal.The method can be applied to signal direction estimation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of digital signal processing, and particularly relates to a signal azimuth estimation method based on multi-channel vector digital beam forming and amplitude comparison. BACKGROUND

[0002] In an increasingly complex electromagnetic environment, passive radar seekers need to meet the application requirements of widening the frequency coverage range, having high sensitivity and anti-interference capability, etc., so radar seekers are mostly in the form of dual-mode or multi-mode composite guidance. However, due to the problem of competing for aperture resources among multiple guidance modes in composite guidance, the antenna placement mode of passive direction finding is limited, which requires the passive radar direction finding system to find a more flexible placement mode to provide space for other guidance modes. To solve this problem, a conformal antenna is often used in passive radar guidance. The conformal antenna can work in an ultra-wide frequency band and completely match the shape of the carrier, meeting the needs of passive radar seekers in anti-radiation missiles.

[0003] Although the traditional digital beam forming (DBF) algorithm has the advantages of improving system sensitivity, increasing the action distance, enhancing useful signals, improving the main beam and sidelobe pattern null control, and simultaneously forming multiple low side lobes to suppress interference and noise, and automatically calibrating the mutual coupling of single elements, etc., the conformal antenna is sensitive to polarization information. In addition to receiving angle information, polarization information is also received. The reception of polarization information by the conformal antenna will cause an additional phase difference. Therefore, the traditional digital beam forming algorithm is no longer applicable to the direction finding of conformal antenna arrays. In view of the above, it is an urgent problem to be solved to propose a passive direction finding algorithm applicable to conformal antennas. SUMMARY

[0004] The purpose of the present application is to solve the problem that the traditional digital beam forming algorithm cannot be applied to the direction finding of conformal antenna arrays, and a signal azimuth estimation method based on multi-channel vector digital beam forming and amplitude comparison is proposed.

[0005] The technical solution adopted by the present application to solve the above technical problem is: a signal azimuth estimation method based on multi-channel vector digital beam forming and amplitude comparison, which specifically comprises the following steps:

[0006] Step 1: arranging a conformal antenna array model composed of conformal antenna elements, and constructing a received polarization signal model of the conformal antenna array model;

[0007] Step 2: performing vector digital beam forming on the received polarization signals of the conformal antenna array model to form multiple beams with different directions;

[0008] Step three, search the different directional beams formed in step two, and search out the polarization parameters and the incident direction corresponding to the maximum beam;

[0009] Step four, select three beams according to the polarization parameters and the incident direction searched out in step three, and perform amplitude comparison using the selected three beams to obtain the final incident angle estimation result of the incident electromagnetic wave signal.

[0010] Further, in step one, an antenna array model composed of conformal antenna elements is arranged, specifically:

[0011] In the xoy plane of the global rectangular coordinate system, a uniform circular array composed of M conformal antenna elements is arranged, and each element is tangent to the circumferential surface of the circular array. The positive direction of the conformal antenna is defined as the right side of the opening protrusion of the conformal antenna, and the pointing angle α of the conformal antenna is defined as the included angle between the positive direction of the conformal antenna and the positive half of the x-axis.

[0012] Further, in step one, the received polarization signal model is:

[0013] Step one, assuming that the incident direction vector of the far-field electromagnetic wave signal is The azimuth angle in the incident direction vector is θ, and the elevation angle is φ. The plane on which the electric field vector E of the incident electromagnetic wave signal is located is perpendicular to the incident direction vector . The horizontal direction of the plane on which the electric field vector E is located is denoted as . The vertical direction of the plane on which the electric field vector E is located is denoted as . The component of the electric field vector E along the horizontal direction is e h , and the component of the electric field vector E along the vertical direction is e v . Then the electric field vector E is represented as:

[0014]

[0015] The polarization auxiliary angle γ is the ratio of the horizontal direction amplitude component e h to the vertical direction amplitude component e v of the electric field vector E, and the polarization phase difference η is the difference between the initial phases. The polarization auxiliary angle γ and the polarization phase difference η are used to obtain the representation of the electric field vector E in the global rectangular coordinate system:

[0016]

[0017] wherein e is the base of the natural logarithm, j is the imaginary unit, and Z is the elliptical size of the electric field vector polarization ellipse.

[0018] Step two, according to the representation of the electric field vector E in the global rectangular coordinate system, the polarization-angle steering vector a of the incident electromagnetic wave signal is obtainedp (θ,φ,γ,η):

[0019]

[0020] The receiving polarization signal model of the conformal antenna array model is:

[0021]

[0022] wherein X(t) represents the polarization signal received by the conformal antenna array at time t, S(t) represents the target signal at time t, and n(t) represents the noise signal at time t, represents the spatial domain steering vector.

[0023] Further, the calculation method of the ellipse size Z of the electric field vector polarization ellipse is:

[0024] Taking the major axis and the minor axis of the electric field vector polarization ellipse as two right angle sides of a right triangle, the ellipse size Z is the length of the hypotenuse of the right triangle.

[0025] Further, the specific process of step two is:

[0026] The complex weighting vector of each conformal antenna array element is denoted as w = [w1, w2, …, wM], wherein w1, w2, …, wM represent the complex weighting coefficients of the first, second, …, and Mth conformal antenna array elements respectively, and the signal X(t) is weighted by using the complex weighting vector to obtain a beam y(t): M ],w1,w2,…,w M

[0027] y(t) = w H X(t)

[0028] wherein w H represents the conjugate transpose of the complex weighting vector w.

[0029] Further, the complex weighting vector w is specifically:

[0030]

[0031] wherein, represents the spatial phase factor of the incident electromagnetic wave signal with the direction of located at the first array element, represents the spatial phase factor of the incident electromagnetic wave signal with the direction of located at the Mth array element, B = [b1 T ,b2 T ,…,b M T ], m = 1, 2, …, M, b m = [sin(d​xm / r)cos(d ym / r)], r is the array radius, d xm and d ym are the coordinate positions of the center projection of the m-th array element on the x-axis and y-axis respectively, Θ and Φ are the sets of azimuth angles and elevation angles, respectively; Υ and Ξ are the sets of polarization auxiliary angles and polarization phase differences, respectively. Indicates azimuth Pitch angle Polarization auxiliary angle Polarization phase difference the corresponding polarization-angle steering vector;

[0032]

[0033] Wherein, m=1, 2,…, M, and λ is the wavelength of the incident electromagnetic wave signal.

[0034] Furthermore, the specific process of step three is:

[0035] Establish the objective function:

[0036]

[0037] Solve the objective function and get the estimated value of the incident azimuth and the pitch angle estimate That is, the incident direction corresponding to the maximum beam, the estimated value of the polarization auxiliary angle and polarization phase difference estimate That is the polarization parameter corresponding to the maximum beam.

[0038] Furthermore, the specific process of step 4 is as follows:

[0039] The azimuth angle corresponding to the maximum beam searched in step 3 is recorded as θ i , the pitch angle corresponding to the maximum beam searched in step 3 is recorded as Then the azimuth angle is selected as θ i-1 And the pitch angle is The beam and azimuth angle are θ i+1 And the pitch angle is beam;

[0040] Will The corresponding beam amplitude is recorded as Will The corresponding beam amplitude is recorded as Will The corresponding beam amplitude is recorded as The final incident azimuth and the final incident elevation angle respectively

[0041]

[0042] wherein θ 0.5 is the beam width in azimuth dimension, is the beam width in elevation dimension.

[0043] The beneficial effects of the present application are:

[0044] In view of the problem that the passive radar direction finding system in the radar seeker needs to adapt to both the super wide frequency band and the conformal antenna sensitive to polarization information, and at the same time, provide spatial resources for other mode direction finding systems, the present application provides a multi-channel vector digital beam forming-amplitude comparison algorithm.

[0045] The algorithm of the present application considers the influence of the spatial polarization characteristics of the receiving antenna and can adapt to the super wide frequency band of 0.8GHz-18GHz. BRIEF DESCRIPTION OF DRAWINGS

[0046] Figure 1 is a schematic diagram of the uniform circular array of the present application;

[0047] Figure 2 is a schematic diagram of the spatial rectangular coordinate system of the receiving antenna direction finding in the present application;

[0048] Figure 3 is a schematic diagram of the directional diagram of the three beams with azimuth directions θ i-1 , θ i and θ i+1 in the present application;

[0049] Fig. 4(a) is a 0.8GHz beam directional diagram formed by using the vector digital beam forming technology of the present application;

[0050] Fig. 4(b) is an 18GHz beam directional diagram formed by using the vector digital beam forming technology of the present application;

[0051] Figure 5 is the angle finding error of the VDBF algorithm (vector digital beam forming technology) and the VDBF-AC algorithm (vector digital beam forming technology-amplitude comparison) in the present application under different signal to noise ratios;

[0052] Figure 6 is the angle finding error of the present application under the frequency of 0.8GHz-18GHz. DETAILED DESCRIPTION

[0053] Embodiment 1: The method for signal azimuth estimation based on multi-channel vector digital beam forming and amplitude comparison in the embodiment comprises the following steps:

[0054] Step 1: arranging a conformal antenna array model composed of conformal antenna elements, and constructing a received polarization signal model of the conformal antenna array model;

[0055] Step 2: performing vector digital beam forming (phase shifting) on the received polarization signal of the conformal antenna array model to form a plurality of beams with different directions;

[0056] Step 3: searching the beams with different directions formed in Step 2 to search out the polarization parameters and the incident direction corresponding to the maximum beam (i.e. obtaining the parameter combination corresponding to the maximum beam by traversing and searching each group of parameter combinations);

[0057] Step 4: selecting three beams according to the polarization parameters and the incident direction searched out in Step 3, and performing amplitude comparison on the selected three beams to obtain the final incident angle estimation result of the incident electromagnetic wave signal.

[0058] The present application assumes that the received array receives the main beam of the transmitting antenna, and the measurement result is the main polarization of the transmitting antenna. At the same time, the coordinate system of the receiving array is the same as the global coordinate system.

[0059] Embodiment 2: In combination with Figure 1 The embodiment is described. The embodiment is different from Embodiment 1 in that, in Step 1, the antenna array model composed of conformal antenna elements is arranged, specifically:

[0060] In the xoy plane of the global rectangular coordinate system, a uniform circular array composed of M conformal antenna elements (the value of M in the present application is 8) is arranged, and each element is tangent to the circumferential surface of the circular array. The positive direction of the conformal antenna is defined as the right side of the opening convex of the conformal antenna, and the pointing angle α of the conformal antenna is defined as the included angle between the positive direction of the conformal antenna and the positive half axis of the x axis.

[0061] The other steps and parameters are the same as those in Embodiment 1.

[0062] The uniform circular array in the present application refers to the distance between any two adjacent elements being equal.

[0063] Embodiment 3: In combination with Figure 2 The embodiment is described. The embodiment is different from Embodiment 1 or 2 in that, in Step 1, the received polarization signal model is:

[0064] Step 1-1: assuming that the incident direction vector of the electromagnetic wave signal in the far field is The azimuth angle of the incident direction vector is θ, the pitch angle is φ, and the plane on which the electric field vector E of the incident electromagnetic wave signal is located is perpendicular to the incident direction vector . The horizontal direction of the plane on which the electric field vector E is located is denoted as . The component of the electric field vector E along the horizontal direction h is e . v The component of the electric field vector E along the vertical direction is e h . v The electric field vector E is represented as:

[0065]

[0066] The polarization auxiliary angle γ is the ratio of the horizontal direction amplitude component e h to the vertical direction amplitude component e v of the electric field vector E, and the polarization phase difference η is the difference between the initial phases, where γ ∈ [0, π / 2] and η ∈ [-π, π]; the representation of the electric field vector E in the global rectangular coordinate system is obtained by using the polarization auxiliary angle γ and the polarization phase difference η according to the polarization characteristics of the incident electromagnetic wave signal:

[0067]

[0068] where e is the base of the natural logarithm, j is the imaginary unit, and Z is the ellipse size of the electric field vector polarization ellipse.

[0069] Step two, the polarization-angle steering vector a p (θ, φ, γ, η) of the incident electromagnetic wave signal is obtained according to the representation of the electric field vector E in the global rectangular coordinate system:

[0070]

[0071] The received polarization signal model of the conformal antenna array model is:

[0072]

[0073] where X(t) represents the polarization signal received by the conformal antenna array at time t, S(t) represents the target signal at time t, n(t) represents the noise signal at time t, and represents the spatial steering vector.

[0074] The other steps and parameters are the same as those in the first or second embodiment.

[0075] The fourth embodiment is different from one of the first to third embodiments in that the calculation method of the ellipse size Z of the electric field vector polarization ellipse is:

[0076] Taking the major axis and minor axis of the electric field vector polarization ellipse as the two right-angled sides of a right triangle, the ellipse size Z is the length of the hypotenuse of the right triangle.

[0077] The other steps and parameters are the same as those in the first to third embodiments.

[0078] Z 2 It represents the power of the incident electromagnetic wave signal.

[0079] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the specific process of step 2 is as follows:

[0080] The complex weight vector of each conformal antenna array element is denoted as w = [w1, w2, ..., w M ],w1,w2,…,w M Denote the complex weighting coefficients of the first, second, …, Mth conformal antenna array elements respectively. The complex weighting vector is used to weight the signal X(t) to obtain the beam y(t). That is, according to the principle of vector digital beamforming, the signal X(t) received by the array element is phase-shifted to obtain the signal matrix after phase shifting:

[0081] y(t)=w H X(t)

[0082] Among them, w H It represents the conjugate transpose of the complex weight vector w. By changing the complex weight coefficient in the complex weight vector w, beams with different directions can be obtained.

[0083] The other steps and parameters are the same as those in the first to fourth embodiments.

[0084] Vector digital beamforming selects appropriate complex weighting vectors to compensate for phase differences between signals received by different array elements and the additional phase differences caused by antenna polarization characteristics, resulting in in-phase addition of the signals in a specific direction and polarization, forming a beam with the specified direction and polarization characteristics. When the phase shift angle matches the direction of the incident signal, and the phase shift polarization tilt and polarization ellipse angle are consistent with the actual signal polarization parameters, the amplitude of the phase shifted and summed signals received by the M array elements reaches its maximum value. Therefore, the approximate range of the incident signal's azimuth, elevation, and polarization parameters can be estimated through a search method.

[0085] Specific embodiment 6: This embodiment differs from any one of specific embodiments 1 to 5 in that the complex weight vector w is specifically:

[0086]

[0087] in, Indicates the direction a spatial phase factor of an incident electromagnetic wave signal at the 1st array element, a direction of a spatial phase factor of an incident electromagnetic wave signal at the Mth array element, B = [b1 T ,b2 T ,…,b M T ], m = 1, 2, …, M, b m = [sin(d xm / r)cos(d ym / r)], r is the array radius, d xm and d ym are the coordinate positions of the center of the mth array element projected on the x-axis and y-axis respectively, Θ and Φ are the sets of azimuth and elevation angles respectively, Υ and Ξ are the sets of polarization auxiliary angle and polarization phase difference respectively, an azimuth angle an elevation angle a polarization auxiliary angle a polarization phase difference a corresponding polarization-angle steering vector.

[0088]

[0089] wherein, m = 1, 2, …, M, λ is the wavelength of the incident electromagnetic wave signal.

[0090] The other steps and parameters are the same as one of the first to fifth embodiments.

[0091]

[0092] Considering that the signal incident space domain is limited and the polarization parameter variation range is also limited, the complete angle set Θ and Φ can be obtained by using the exhaustive method, which is composed of possible incident azimuth and elevation angles. Similarly, the sets of polarization auxiliary angle and polarization phase difference Υ and Ξ can be obtained,

[0093] The following describes all possible parameter combinations of the present application:

[0094] In the polarization auxiliary angle variation range, each polarization auxiliary angle value is uniformly selected and recorded as γ1, γ2, …, γ A′ In the polarization auxiliary angle variation range, each polarization auxiliary angle value is uniformly selected and recorded as γ1, γ2, …, γ A′ The polarization auxiliary angle variation range is divided into A′-1 equal intervals, and each polarization phase difference is uniformly selected in the polarization phase difference variation range, and each polarization phase difference value is recorded as η1, η2, …, ηB′ , η1, η2, …, η B′ Divide the polarization phase difference change range into B'-1 equal intervals, uniformly select each azimuth angle in the azimuth angle change range, and record each azimuth angle value as θ1, θ2, …, θ C , θ1, θ2, …, θ C Divide the azimuth angle change range into C-1 equal intervals, uniformly select each elevation angle in the elevation angle change range, and record each elevation angle value as Divide the elevation angle change range into D-1 equal intervals; then

[0095] Take γ1, η1, θ1, and as a parameter combination, take γ1, η1, θ1, and as a parameter combination, …, take γ1, η1, θ1, and as a parameter combination;

[0096] Take γ1, η1, θ2, and as a parameter combination, take γ1, η1, θ2, and as a parameter combination, …, take γ1, η1, θ2, and as a parameter combination;

[0097] …

[0098] Take γ1, η1, θ C , and as a parameter combination, take γ1, η1, θ C , and as a parameter combination, …, take γ1, η1, θ C , and as a parameter combination;

[0099] Take γ1, η2, θ1, and as a parameter combination, take γ1, η2, θ1, and as a parameter combination, …, take γ1, η2, θ1, and as a parameter combination;

[0100] Take γ1, η2, θ2, and as a parameter combination, take γ1, η2, θ2, and as a parameter combination, …, take γ1, η2, θ2, and as a parameter combination;

[0101] …

[0102] Take γ1, η2, θ C , and As a parameter combination, γ1, η2, θ C and As a parameter combination, γ1, η2, θ C and As a parameter combination;

[0103] …

[0104] As a parameter combination, γ1, η B′ , θ1and As a parameter combination, γ1, η B′ , θ1and As a parameter combination, γ1, η B′ , θ1and As a parameter combination;

[0105] As a parameter combination, γ1, η B′ , θ2and As a parameter combination, γ1, η B′ , θ2and As a parameter combination, γ1, η B′ , θ2and As a parameter combination;

[0106] …

[0107] As a parameter combination, γ1, η B′ , θ C and As a parameter combination, γ1, η B′ , θ C and As a parameter combination, γ1, η B′ , θ C and As a parameter combination;

[0108] In this way, for each polarization auxiliary angle value, all the above possible combinations are traversed. According to each parameter combination, vector digital beamforming is performed, and a beam pointing in a direction can be obtained.

[0109] Specific implementation seven: different from one of the specific implementations one to six, the specific process of the step three is:

[0110] The target function is established as follows:

[0111]

[0112] Solving the target function, the incident azimuth angle estimation value and the elevation angle estimation value are obtained, which are the incident direction corresponding to the maximum beam and the polarization auxiliary angle estimation value. and the polarization phase difference estimation value is the polarization parameter corresponding to the maximum beam.

[0113] The other steps and parameters are the same as one of the first to sixth embodiments.

[0114] Embodiment eight: combination Figure 3 This embodiment is described. This embodiment is different from one of the first to seventh embodiments in that the specific process of step four is:

[0115] The azimuth angle corresponding to the maximum beam searched in step three is denoted as θ i The elevation angle corresponding to the maximum beam searched in step three is denoted as The beam with the azimuth angle θ i-1 and the elevation angle and the beam with the azimuth angle θ i+1 and the elevation angle are selected; it should be noted that the selected beams are also selected from the beams corresponding to the polarization auxiliary angle estimation value and the polarization phase difference estimation value

[0116] wherein θ i-1 , θ i and θ i+1 are the i-1th, ith and i+1th azimuth angles in the azimuth angle set; and are the i-1th, ith and i+1th elevation angles in the elevation angle set;

[0117] Definition and are the beam pattern functions corresponding to the first selected beam, the second selected beam and the third selected beam, respectively, and the amplitude of the beam corresponding to is denoted as The amplitude of the beam corresponding to is denoted as The amplitude of the beam corresponding to is denoted as The specific azimuth of the signal is determined by comparing the amplitudes, and the final incident azimuth angle and the final incident elevation angle are respectively:

[0118]

[0119] wherein θ 0.5 is the beam width in the azimuth angle dimension, is the beam width in the elevation angle dimension.​

[0120] Other steps and parameters are the same as one of the first to seventh embodiments.

[0121] Experimental section

[0122] In order to verify the beneficial effects of the present application, the following simulation test is carried out: a uniform circular array composed of 8 electric dipole antennas, the radius r of the circular array is 300 mm. It is assumed that the relative angle between the electromagnetic wave of the transmitting antenna and the receiving array is the azimuth angle 0° and the elevation angle 0°. In addition, the polarization of the transmitting antenna is vertical polarization (relative to the ground).

[0123] Fig. 4(a) and Fig. 4(b) respectively show the beam pattern formed by the present application using vector digital beam forming technology, with the direction pointing to the azimuth angle 0°, the elevation angle 0°, the polarization being vertical polarization, and the frequency being 0.8 GHz and 18 GHz.

[0124] Figure 5 For the frequency of 6 GHz, the RMSE of the angle information estimated by the algorithm of the present application and the vector digital beam forming technology without amplitude comparison direction finding changes with the signal-to-noise ratio. It is assumed that the angle between the transmitting signal and the receiving array is (14.3°, 3.8°), the polarization parameters (γ, η) of the transmitting antenna are (10°, 0°), and the number of experiments is 100 times.

[0125] Figure 6 For the frequency of 0.8 GHz-18 GHz, the RMSE of the angle information estimated by the algorithm of the present application changes with the signal-to-noise ratio. It is assumed that the angle between the transmitting signal and the receiving array is (14.3°, 3.8°), the polarization parameters (γ, η) of the transmitting antenna are (10°, 0°), and the number of experiments is 100 times.

[0126] From Figure 5 and Figure 6 It can be seen that the algorithm of the present application has good direction finding performance in the wide frequency band of 0.8 GHz-18 GHz, and can adapt to the polarization characteristics of the conformal antenna.

[0127] In summary, the present application discloses an eight-channel vector digital beam forming-amplitude comparison algorithm. The method of the present application proposes a vector digital beam forming technology based on the digital beam forming technology to adapt to the polarization sensitive characteristics of the conformal antenna, forms a beam with specified direction and polarization parameters, and then performs direction finding on the antenna receiving signal. Moreover, it can adapt to the super wide frequency band of 0.8 GHz-18 GHz, and the method of using multiple beam amplitude comparison based on vector digital beam forming improves the direction finding precision. The method of the present application considers the influence of the spatial polarization characteristics of the receiving antenna and the super wide frequency adaptation range, and improves the direction finding precision of the algorithm.

[0128] The above calculation examples of the present application are only used to illustrate the calculation model and calculation process of the present application, and are not used to limit the embodiments of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art, and all the embodiments cannot be exhausted here. Any obvious changes or variations derived from the technical solutions of the present application are still within the protection scope of the present application.

Claims

1. A signal direction estimation method based on multi-channel vector digital beamforming and amplitude comparison, characterized in that: The method specifically comprises the following steps: Step 1: Arrange a conformal antenna array model composed of conformal antenna elements, and construct a received polarization signal model of the conformal antenna array model; Step 2: Perform vector digital beamforming on the received polarized signal of the conformal antenna array model to form multiple beams with different directions; The specific process of step 2 is as follows: The complex weight vector of each conformal antenna array element is denoted as w = [w1, w2, ..., w M ],w1,w2,...,w M Denote the complex weighting coefficients of the first, second, ..., Mth conformal antenna array elements respectively. The complex weighting vector is used to weight the signal X(t) to obtain the beam y(t): y(t)=w H X(t) Among them, w H represents the conjugate transpose of the complex weight vector w; The complex weight vector w is specifically: in, Indicates the direction The spatial phase factor of the incident electromagnetic wave signal located at the first array element, Indicates the direction The spatial phase factor of the incident electromagnetic wave signal at the Mth array element, B=[b1 T ,b2 T ,…,b M T ],m=1,2,…,M,b m =[sin(d xm / r)cos(d ym / r)], r is the array radius, d xm and d ym are the coordinate positions of the center projection of the m-th array element on the x-axis and y-axis respectively, Θ and Φ are the sets of azimuth angles and elevation angles, respectively; Υ and Ξ are the sets of polarization auxiliary angles and polarization phase differences, respectively. Indicates azimuth Pitch angle Polarization auxiliary angle Polarization phase difference the corresponding polarization-angle steering vector; Where m = 1, 2, ..., M, λ is the wavelength of the incident electromagnetic wave signal; Step 3: Search for the different directional beams formed in step 2 to find the polarization parameter and incident direction corresponding to the largest beam; The specific process of step three is: Establish the objective function: Solve the objective function and get the estimated value of the incident azimuth and the pitch angle estimate That is, the incident direction corresponding to the maximum beam, the estimated value of the polarization auxiliary angle and polarization phase difference estimate That is the polarization parameter corresponding to the maximum beam; Step 4: Select three beams based on the polarization parameters and incident direction searched in step 3, and use the three selected beams to perform amplitude comparison to obtain the final incident angle estimation result of the incident electromagnetic wave signal.

2. The signal direction estimation method based on multi-channel vector digital beamforming and amplitude comparison according to claim 1, characterized in that: In step 1, an antenna array model consisting of conformal antenna elements is arranged as follows: In the xoy plane of the global rectangular coordinate system, a uniform circular array consisting of M conformal antenna elements is arranged, and each element is tangent to the circumferential surface of the circular array. The positive direction of the conformal antenna is defined as the right side of the conformal antenna opening protrusion, and the pointing angle α of the conformal antenna is defined as the angle between the positive direction of the conformal antenna and the positive semi-axis of the x-axis.

3. The signal direction estimation method based on multi-channel vector digital beamforming and amplitude comparison according to claim 2, characterized in that: In step 1, the received polarization signal model is: Step 1: Assume that the incident direction vector of the far-field electromagnetic wave signal is The azimuth angle of the incident direction vector is θ, the pitch angle is φ, and the plane where the electric field vector E of the incident electromagnetic wave signal is located is the same as the incident direction vector Vertically, the horizontal direction of the plane where the electric field vector E is located is recorded as The vertical direction of the plane where the electric field vector E lies is recorded as The electric field vector E is in the horizontal direction The component is e h , the electric field vector E is in the vertical direction The component is e v , then the electric field vector E is expressed as: Polarization auxiliary angle γ is the horizontal amplitude component e of the electric field vector E h and the vertical amplitude component e v The polarization phase difference η is the difference in the initial phase; the polarization auxiliary angle γ and the polarization phase difference η are used to obtain the representation of the electric field vector E in the global rectangular coordinate system: Where, e is the base of the natural logarithm, j is the imaginary unit, and Z is the elliptical size of the electric field vector polarization ellipse; Step 1 and 2: Based on the representation of the electric field vector E in the global rectangular coordinate system, the polarization-angle steering vector a of the incident electromagnetic wave signal is obtained. p (θ,φ,γ,η): Then the received polarization signal model of the conformal antenna array model is: Where X(t) represents the polarization signal received by the conformal antenna array at time t, S(t) represents the target signal at time t, and n(t) represents the noise signal at time t. Represents the spatial steering vector.

4. The signal direction estimation method based on multi-channel vector digital beamforming and amplitude comparison according to claim 3, characterized in that: The calculation method of the ellipse size Z of the electric field vector polarization ellipse is: Taking the major axis and minor axis of the electric field vector polarization ellipse as the two right-angled sides of a right triangle, the ellipse size Z is the length of the hypotenuse of the right triangle.

5. The signal direction estimation method based on multi-channel vector digital beamforming and amplitude comparison according to claim 4, characterized in that: The specific process of step 4 is as follows: The azimuth angle corresponding to the maximum beam searched in step 3 is recorded as θ i , the pitch angle corresponding to the maximum beam searched in step 3 is recorded as Then the azimuth angle is selected as θ i-1 And the pitch angle is The beam and azimuth angle are θ i+1 And the pitch angle is beam; Will The corresponding beam amplitude is recorded as Will The corresponding beam amplitude is recorded as Will The corresponding beam amplitude is recorded as The final incident azimuth and the final incident pitch angle They are: Among them, θ 0.5 is the beamwidth in the azimuth dimension, is the beamwidth in the elevation dimension.

Images