An arbitrary elliptical polarization reconfigurable cylindrical conformal array focusing beam synthesis method

Abstract

The application discloses a method for synthesizing a focusing beam of a columnar conformal array with arbitrary elliptical polarization reconfigurability. The columnar conformal array antenna is difficult to realize the reconfigurable synthesis of an arbitrary elliptical polarization beam under a single-channel architecture due to inconsistent orientations of units. Existing methods usually rely on double-channel dual-polarized units, which have problems of large equipment quantity and high cost; or are only applicable to linear polarization / circular polarization planar arrays and cannot be extended to the arbitrary elliptical polarization scenario of the columnar conformal array. The application adopts a multi-linear polarization reconfigurable antenna as an array unit, proposes a candidate polarization state screening strategy based on long and short axis projection, a hybrid greedy-local search array element polarization state optimization method, and an excitation phase configuration method for elliptical polarization, and realizes high-purity synthesis of the arbitrary elliptical polarization focusing beam of the columnar conformal array under the architecture of a single antenna unit corresponding to a single radio frequency channel.

Description

Technical Field

[0001] This invention relates to beamforming technology for arbitrary elliptical polarization conformal array antennas in the fields of radar, communication, and electronic countermeasures. Background Technology

[0002] The polarization domain, as an important dimension of antenna research, plays a crucial role in fields such as wireless communication, radar detection, and electronic warfare. Achieving arbitrary polarization beams on conformal arrays can effectively mitigate cross-polarization interference caused by complex electromagnetic environments and polarization mismatch problems caused by rapid changes in platform attitude, thereby improving communication reliability and detection performance.

[0003] The existing method for achieving arbitrary polarization tunability on array antennas usually involves using a dual-channel dual-polarized unit antenna, combined with two sets of independent and controllable amplitude and phase channels to achieve arbitrary polarization tunability of the array antenna (reference [1]). However, this method leads to a doubling of the array equipment, which in turn significantly increases the system cost, limiting its application and promotion in conformal arrays to some extent. Some studies are based on pattern synthesis of dual-polarized conformal arrays (reference [2]), but still face the challenges of increased feed network complexity and implementation cost due to the doubling of RF channels. In terms of polarization reconfigurable antennas, there has been a large amount of research on polarization reconfiguration of unit antennas (references [3]-[7]), which has gradually evolved from discrete polarization switching (such as switching between linear and circular polarization) to multi-polarization states and even arbitrary polarization states. For example, reference [5] uses pixelated patch antennas loaded with PIN diodes to achieve up to 8 linear polarization and dual circular polarization states. Reference [6] uses a reconfigurable metasurface combined with a phase-controllable feed network loaded with variable capacitors and a planar patch array to achieve arbitrary elliptical polarization beam generation. However, the above research mainly focuses on planar arrays. In conformal arrays, the spatial variation of the orientation of each element leads to a more complex mapping relationship between the local polarization state and the far-field polarization, making it difficult to directly extend the existing planar array methods to conformal array scenarios. Reference [8] proposes a planar array arbitrary polarization beam synthesis method based on multi-linear polarization reconfigurable elements. By using the desired elliptical polarization parameter as the constraint condition for the polarization state and excitation phase of the element, it realizes the reconfigurable beam synthesis of linear polarization and circular polarization. However, this method adopts a stochastic optimization strategy, and the optimization results are highly random and have a slow convergence speed. At the same time, this method does not systematically model and solve the complex coordinate transformation and polarization mapping problem caused by the inconsistent orientation of elements in conformal arrays.

[0004] In summary, existing technologies have not yet solved the problem of reconfigurable focused beamforming with arbitrary elliptical polarization on cylindrical conformal arrays, where a single antenna corresponds to a single radio frequency channel.

[0005] References:

[0006] [1]:B. Fuchs and J. J. Fuchs*, Optimal polarization synthesis ofarbitrary arrays with focused power pattern, IEEE Trans. Antennas Propag.,vol. 59, no. 12, pp. 4512-4519, 2011.

[0007] [2]:C. Liu, J. Qian, L. Zhang, and X. Zhang*, Pattern synthesis ofdual-polarised conformal array based on adaptive iterative convexoptimisation, IET Microw. Antenn. Propag., vol. 17, no. 3, pp. 237-246, 2023.

[0008] [3]:W. Tang, X. Gao, C. Ding, C. Zhu, R. Li, B. Tian, X. Bu, and J.An*, A quad-polarization reconfigurable conformal array of wide coveragerange and high gain for unmanned aerial vehicle communications, IEEE Trans.Antennas Propag., vol. 72, no. 4, pp. 3795-3800, 2024.

[0009] [4]:N. Zhu, X.-X. Yang, T. Lou, Q. Cao, and S. Gao*, Broadbandpolarization-reconfigurable slot antenna and array with compact feed network,IEEE Antennas Wireless Propag. Lett., vol. 18, no. 6, pp. 1293-1297, 2019.

[0010] [5]:W. Zheng, Y. Yang, and H. Li*, Design of polarizationreconfigurable pixel antennas with optimized PIN-diode implementation, IEEETrans. Antennas Propag., vol. 73, no. 2, pp. 851-862, 2025.

[0011] [6]:Y. T. Chen, H. L. Wang, Y. K. Wang, S. Zheng, T. Y. Zhang, S.Sun, T. J. Cui, and H. F. Ma*, A reconfigurable metasurface antenna forarbitrarily polarized beam generation and advanced polarization detection,Laser Photonics Rev., vol. 19, no. 5, p. 2401461, 2025.

[0012] [7]:J. Feng, Z. Yan, S. Yang, F. Fan, T. Zhang, X. Liu, X. Zhao, andQ. Chen*, Reflect-transmit-array antenna with independent dual circularlypolarized beam control, IEEE Antennas Wireless Propag. Lett., vol. 22, no. 1,pp. 89-93, 2023.

[0013] [8]: D. Chen, Y. Liu*, Z. Wang, Q. Liu, S. Yang, and J. Hu, Arbitrarypolarization wave radiator with high polarization purity via a multi-linear reconfigurable antenna array, IEEE Trans. Antennas Propag., vol. 74, no. 2, pp. 1535-1550, 2026. Summary of the Invention

[0014] This invention proposes a method for reconfigurable cylindrical conformal array focusing beamforming with arbitrary elliptical polarization. It employs a multi-line polarization reconfigurable antenna as the array element, investigating the projection characteristics of the far-field vector of the array elements in the desired elliptical polarization major and minor axes, candidate polarization state selection strategies, an array element polarization state optimization method based on hybrid greedy-local search, an excitation amplitude and phase configuration method for elliptical polarization synthesis, and a conformal array vector beamforming method. Under a low-cost architecture where a single antenna element corresponds to a single RF channel, high-purity reconfigurable beamforming of arbitrary elliptical polarization focusing beams from a conformal array is achieved. The core idea of ​​this invention is to transform the problem of synthesizing arbitrary elliptical polarization beams from cylindrical conformal arrays into—in the beam pointing direction, to synthesize the major axis component vector of some array elements and the minor axis component vector of others, and to ensure polarization pointing accuracy by optimizing the array polarization state layout so that the ratio of the synthesized major and minor axis vectors approximates the desired ellipticity and minimizes the cross-projection components. The specific technical solution is as follows:

[0015] 1) Candidate polarization state selection strategy based on major and minor axis projection: For the nth element, first calculate its far-field vector in each polarization state along the beam pointing direction. Select two candidate polarization states for synthesizing the major axis component: the first candidate state maximizes the absolute value of the projection of the far-field vector onto the major axis of the principal polarization ellipse; the second candidate state maximizes this projection among all states except the first, and the projections of the far-field vector onto the minor axis of the principal polarization ellipse in the two candidate states must have opposite signs. Construct a set of candidate polarization states for synthesizing the minor axis component in the same way.

[0016] 2) Modeling a nonconvex mixed-integer nonlinear programming problem: In the beam pointing direction, the major and minor axis components of the composite field can be represented as a weighted superposition of the far-field vectors of each effective array element. The polarization state configuration problem is transformed into solving the selection matrix under three constraints. and (a) Each array element selects only one polarization state; (b) The deviation between the ratio of the minor axis to the major axis amplitude of the synthesized field and the desired ellipticity does not exceed the preset tolerance ε; (c) The absolute value of the cross projection component in the major axis synthesis and the minor axis synthesis is minimized.

[0017] 3) Hybrid Greedy-Local Search Optimization Algorithm: The hybrid greedy-local search optimization algorithm developed in this invention is as follows: (a) Input beam parameters and desired elliptic polarization parameters, obtain a candidate state set based on the candidate polarization state screening strategy, and set the ellipticity error tolerance and maximum number of iterations; (b) Construct a selection matrix based on the projection matrix; (c) Adopt a greedy strategy, and under the ellipticity constraint, assign polarization states to the array elements in sequence according to the principle of maximizing the contribution of each effective array element to the main polarization component, to obtain the initial selection matrix; (d) According to the current polarization state distribution, fix the contribution role of each array element, and perform local polarization state switching under the orientation accuracy constraint to improve the orientation accuracy of the synthesized field; (e) Calculate the actual ellipticity of the synthesized field. If the deviation exceeds the tolerance, correct the ellipticity by adjusting the contribution role of some array elements; (f) Repeat steps (d) and (e) until convergence or the maximum number of iterations is reached. 4) Excitation Amplitude and Phase Configuration Method: When the angle between the array element normal and the beam pointing exceeds the angle threshold, the array element is considered an invalid array element, the excitation amplitude is 0, and it does not participate in beamforming. The effective array elements are excited with equal amplitude. The excitation phase consists of two parts: one is the spatial phase compensation term used to achieve beam focusing; the other is the additional phase term used to synthesize elliptic polarization. Array elements assigned to the synthesis of the major axis component do not need additional phase, while array elements assigned to the synthesis of the minor axis component need to be assigned ±π / 2 phase (the sign is determined according to the rotation direction) to ensure that there is an orthogonal phase difference between the synthesized fields of the major and minor axes. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the polarization state distribution of a multi-polarized reconfigurable cylindrical conformal array antenna constructed when the beam direction is normal.

[0019] Figure 2 It is the main polarization pattern of the composite elliptical polarized beam formed by superimposing different beams pointing downwards.

[0020] Figure 3 It is the cross-polarization pattern within the half-power beamwidth of the composite ellipticized beam formed by superimposing different beams pointing downwards.

[0021] Figure 4 These are statistical results of the cross-polarization level within the half-power beamwidth under different desired elliptic polarization parameters. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, specific embodiments are described below, with reference to the appendix. Figures 1-4 The present invention will be further described in detail below.

[0023] Step 1. In this embodiment, the element antenna is a 6-line polarized reconfigurable antenna, and its radiation pattern in each polarization state is a rotating ideal dipole radiation pattern. The element antenna is then... The wavelengths are spaced on a conformal cylindrical surface, with a total of 144 array elements. An angular threshold is set. .

[0024] Step 2. Establish the local and global coordinate systems for each array element. Extract the vector radiation patterns of each linear polarization state of the reference array element in its local coordinate system through full-wave simulation. Since the element antenna has a rotationally symmetric structure, a radiation pattern rotation approximation method can be used to quickly obtain the radiation patterns of other polarization states. Utilize the coordinate transformation matrix from the local coordinate system to the global coordinate system. The vector pattern of each array element in each polarization state is transformed to the global coordinate system.

[0025] Step 3. Based on the user's desired elliptic polarization parameters—in this embodiment, the polarization azimuth angle is used as... ellipticity angle is Taking left-handed polarization as an example. Based on the candidate polarization state selection strategy: for each array element, select the polarization state from the six linear polarization states that makes the far-field vector... and The two candidate states with the largest upward projection are selected, and the cross-projection signs of the two candidate states are ensured to be opposite, thus obtaining the set of candidate polarization states. The beam pointing scanning range is set to... , .

[0026] Step 4. Set the ellipticity error tolerance. and maximum number of iterations Construct the projection matrix , , , and selection matrix , A hybrid greedy-local search algorithm is used for polarization state optimization: first, a greedy strategy is used to sequentially assign polarization states to each effective array element under ellipticity constraints to obtain the initial configuration; then, the orientation accuracy of the synthesized field is improved by switching local polarization states; it is checked whether the synthesized ellipticity meets the tolerance requirements, and if not, it is corrected by adjusting the contribution role of the array elements; the process is iterated until convergence. Figure 1 This indicates the beam direction is The distribution of polarization states of array elements at that time.

[0027] Step 5. For effective array elements that meet the angle threshold condition, determine the excitation amplitude and phase according to their role in the selection matrix: the excitation phase of the major axis component composite array elements is the focusing beam phase, and the excitation phase of the minor axis component composite array elements is supplemented with the phase required for left-handed elliptic polarization. Additional phase. For invalid array elements that exceed the angle threshold, the excitation amplitude is set to zero.

[0028] Step 6. Perform vector beamforming in a unified global coordinate system and calculate the main polarization pattern and cross-polarization pattern pointing down for each beam. Figure 2 and 3 The diagram illustrates the main polarization and cross-polarization patterns within the half-power beamwidth of the synthesized elliptical polarized beam under different beam directions. At that time, the cross-polarization level within the half-power beamwidth is better than −18.0 dB; beam scan to At that time, the cross-polarization level was still better than −14.0 dB. To further verify the adaptability of this method to different elliptic polarization parameters, the orientation angle was adjusted from... arrive (step) ), Ellipticity angle from arrive (step) Statistical synthesis was performed on various elliptic polarization states, all with left-handed rotation. The cross-polarization electrical average remained better than -14.0 dB within the half-power beamwidth. Figure 4 As shown. It should be noted that when the beam direction is... At that time, because the angle between the normal of all array elements and the beam direction exceeds the angle threshold. No effective array elements participated in beamforming.

Claims

1. A method for focusing beamforming using an arbitrarily elliptical polarization reconfigurable cylindrical conformal array, characterized in that... Includes the following steps: S1: Establish the array model: Construct a multi-polarized reconfigurable cylindrical conformal array and determine relevant parameters, including the number of discrete reconfigurable linear polarizations of the antenna elements. Array configuration, number of array elements Array layout and spatial position and orientation of array elements; S2: Establish global and local coordinate systems, and extract the vector element radiation patterns of each polarization state of the array element in its local coordinate system through full-wave simulation or actual measurement; obtain the vector radiation patterns of each array element in the global coordinate system using coordinate transformation; S3: Based on the user's desired elliptic polarization parameters—including polarization azimuth angle. Ellipticity angle And the rotation direction (left-handed LH / right-handed RH), adopting a candidate polarization state screening strategy based on major and minor axis projection, constructing a set of candidate polarization states for each array element to synthesize the major and minor axis components of elliptic polarization; S4: Using the desired elliptic polarization parameters as constraints, establish a non-convex mixed-integer nonlinear programming model for the polarization state selection matrix. Employ a hybrid greedy-local search optimization algorithm to determine the optimal polarization state for each matrix element from the candidate polarization state set, thus obtaining the polarization state selection matrix. and ; S5: Select the matrix based on the polarization state, combined with the beam pointing direction. Determine the excitation amplitude and phase of each array element: for those satisfying the angle threshold condition The effective array element has an excitation phase determined by the focusing beam phase and the additional phase required for elliptic polarization synthesis, and the excitation amplitude is 0 or 1. S6: The vector patterns of each array element are weighted and superimposed in a unified global coordinate system to synthesize the elliptical polarization focusing beam of the cylindrical array, thus obtaining the array's main polarization pattern. and cross-polarization pattern .

2. The method for focusing beamforming of an arbitrary elliptical polarization reconfigurable cylindrical conformal array according to claim 1, characterized in that: The element antenna in step S1 is a multi-polarized reconfigurable antenna with... The antenna has a discrete selectable linear polarization state and a rotationally symmetric structure. The radiation pattern corresponding to its different polarization states can be approximated by rotation operation.

3. The method for focusing beamforming of an arbitrary elliptical polarization reconfigurable cylindrical conformal array according to claim 1, characterized in that: The specific steps of coordinate transformation in step S2 are as follows: S2.1 Establish a local coordinate system for each array element, with its origin located at the element's own position, and the Z' axis of the local coordinate system aligned with the normal of the array element. Extract the vector pattern of each polarization state of the reference array element in its local coordinate system using full-wave simulation or actual measurement. Let the vector pattern of the local coordinate system of the nth array element in the mth polarization state be denoted as... ; S2.2 Establish the transformation matrix from the local coordinate system to the global coordinate system ; For the nth element, if its position in the global coordinate system is... Its normal direction is the pitch angle. azimuth angle is The coordinate transformation process can be viewed as first rotating around the y-axis of the global coordinate system. Then rotate around the z-axis This yields the transformation matrix from the local coordinate system to the global coordinate system. ; S2.3 Using the transformation matrix Transforming the vector pattern in the local coordinate system to the global coordinate system yields the vector pattern of each array element in the global coordinate system under different polarization states. .

4. The method for focusing beamforming of an arbitrary elliptical polarization reconfigurable cylindrical conformal array according to claim 1, characterized in that: In step S2, if the mutual coupling between array elements is small or the accuracy of the radiation pattern is required, it can be assumed that the radiation patterns of each array element are consistent in their respective local coordinate systems under the same polarization state. Thus, it is only necessary to extract the radiation pattern of a single reference array element under each polarization state, and then obtain the radiation pattern of all array elements in the global coordinate system through coordinate transformation, which greatly reduces the workload of full-wave simulation or actual measurement.

5. The method for focusing beamforming of an arbitrary elliptical polarization reconfigurable cylindrical conformal array according to claim 1, characterized in that: The candidate polarization state selection strategy in step S3 is based on the major and minor axis directions of the desired elliptic polarization. The specific steps are as follows: S3.1 Based on the desired elliptic polarization parameters given by the user, the direction of the major axis component of the principal polarization vector in the far-field space is determined using Ludwig's third definition. and the direction of the minor axis component And the direction of the cross-polarization vector; the desired elliptic polarization parameters include the polarization azimuth angle. Ellipticity angle And the direction of rotation; S3.2 For the nth element in the array, in its In each discrete polarization state, the far-field vector of the array element in the beam pointing direction is calculated for each polarization state, and the value of this vector in the desired major axis direction is also calculated. Projection size; S3.3 from Candidate states are selected from the polarization states: First, select the states that make the projection... The maximum polarization state is denoted as Then select the exceptions. The external polarization state that maximizes the projection The condition is added: the far-field vector of the array element in the two candidate states is along the minor axis. The projection symbol on is the opposite, that is This leads to the construction of a candidate polarization state set for synthesizing the major axis components of elliptic polarization. and ; S3.4 Select the projection The two largest candidate polarization states and By adding the condition that the signs of their projections along the major axis are opposite, a set of candidate polarization states for synthesizing the minor axis components of elliptic polarization is constructed. and .

6. The method for focusing beamforming of an arbitrary elliptical polarization reconfigurable cylindrical conformal array according to claim 1, characterized in that: The specific steps of modeling the non-convex mixed-integer nonlinear programming problem and using the hybrid greedy-local search optimization algorithm in step S4 are as follows: S4.1 Define the projection matrix , , , ∈ , respectively characterizing the contribution of each array element to the desired major and minor axis directions under the candidate polarization states: where and These represent the candidate states of each array element. and Lower far-field vector along and The projection; and These represent the candidate states of each array element. and Lower far-field vector along and The projection; S4.2 Construct two polarization state selection matrices and ∈ ; S4.3 Establish ellipticity constraints for elliptic polarization synthesis: require the ratio of the minor axis to the major axis components of the synthesized field to approximate the desired ellipticity. S4.4 Establish polarization pointing accuracy constraints: Minimize the cross projection components in both major axis synthesis and minor axis synthesis; S4.5 is solved using a hybrid greedy-local search algorithm. and The process is as follows: (a) Input beam pointing and angle threshold and expected elliptic polarization Based on the candidate polarization state set obtained in step S3, an ellipticity error tolerance is set. and maximum number of iterations (b) Obtain the projection matrix and construct the selection matrix according to step S4.1; (c) Adopt a greedy strategy: under the ellipticity constraint, according to the principle of maximizing the contribution of each effective array element to the principal polarization component, assign polarization state to each effective array element in turn to obtain the initial selection matrix. (d) Based on the current polarization state distribution, fix the role of each array element in the composite major or minor axis component, and perform local polarization state switching on some array elements under the constraint of polarization pointing accuracy; (e) Calculate the actual ellipticity of the composite field. If the ellipticity deviation exceeds the tolerance, it is corrected by adjusting the contribution role of some array elements; (f) Repeat steps (d) and (e) until the error meets the tolerance or the maximum number of iterations is reached. ; (g) Output polarization state selection matrix and .

7. The method for focusing beamforming of an arbitrary elliptical polarization reconfigurable cylindrical conformal array according to claim 1, characterized in that: The method for determining the amplitude and phase of the array element excitation in step S5 is as follows: S5.1 introduces an angle threshold When the angle between the array element normal and the beam pointing direction is greater than At this time, the array element is considered an invalid array element, its excitation amplitude is set to 0, and it does not participate in beamforming; S5.2 For effective array elements, their excitation amplitude is 1, and the excitation phase is determined according to their role in the selection matrix: if the array element is assigned to the composite major axis component, its excitation phase is the focusing beam phase: If an array element is assigned to the synthesized minor axis component, its excitation phase is the sum of the focusing beam phase and the elliptic polarization additional phase: ;in For wave number, For the operating wavelength, σ is the position vector of the nth element in the global coordinate system; σ is the additional phase of the elliptic polarization rotation: when left-handed elliptic polarization is desired. When right-handed elliptic polarization is desired .

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