An electromagnetic lens loaded active phased array multi-beam continuous scanning method

Abstract

The application discloses a kind of active phased array array multi-beam continuous scanning method loaded with electromagnetic lens, the method comprises: super material electromagnetic lens is placed in front end of active phased array, and the focusing characteristics of electromagnetic lens are used to make array form high gain beam. Optimal antenna array element weighting coefficient is solved by using convex optimization algorithm with constraint, while ensuring the accuracy of lens array transmitting and receiving beam pattern, the number of used antenna is as low as possible, which greatly reduces cost and power consumption. The method of the application also overcomes the shortcomings that other lens arrays cannot be continuously scanned or are difficult to manufacture, has the advantages of multi-beam continuous scanning, and is easy to implement in engineering.

Description

Technical Field

[0001] This invention belongs to the field of array signal processing, and in particular to a method for multi-beam continuous scanning of an active phased array with electromagnetic lens loading. Background Technology

[0002] With the continuous improvement of informatization, the multi-functional integration of electronic systems has become an inevitable trend. One of the key issues is the realization of integrated radio frequency (RF) systems and corresponding multi-beamforming technologies. Traditional beamforming techniques based on matrix inversion are not suitable for multi-functional systems. Commonly used synthetic RF aperture multi-beamforming methods include the Butler matrix method and the partial aperture method. The Butler matrix method is a lossless gain multi-beamforming method. Each beam can utilize the entire antenna aperture of the array to obtain the antenna gain provided by the entire array, and the beams are orthogonal, meaning that the direction of the maximum value of each beam coincides with the direction of the zero value of other beams, resulting in high beam isolation. However, the beams formed by this method are not independent, and their pointing relationships are fixed. The partial aperture method divides the entire transmitting antenna array into several sub-arrays, each occupying only a portion of the entire transmitting antenna array. These sub-arrays form their own beams. The characteristic of this method is that each transmitted beam is independently controllable, but a significant problem is that each beam cannot utilize the entire array aperture, resulting in significant beam gain loss, and the number of transmitted beams is not flexible enough.

[0003] In recent years, phase-weighted phased array technology has become the most commonly used technique in multi-beamforming for multi-functional systems. It allows for flexible control of beam direction and simultaneous multi-beam formation. However, it is difficult to extend to broadband applications. With the continuous increase in system functionality, the requirements for radar resolution, communication speed, and other functionalities are becoming increasingly stringent. Ultra-wideband multi-beamforming has become a critical challenge that must be addressed, and related research has gradually become a hot topic. Traditional phase-shifting methods cannot compensate for the path difference between frequency components of broadband signals, resulting in beam distortion. Therefore, the true delay method based on broadband delay compensation is currently the most effective ultra-wideband beamforming method. However, traditional true delay methods have high hardware implementation costs and strict requirements for synchronization between digital channels.

[0004] By loading metamaterial electromagnetic lenses at the front end of the antenna array, the path difference between different frequency components of an ultra-wideband signal can be compensated, thereby significantly improving antenna gain and enabling multi-beamforming. High-gain beams can be formed with only a small number of antennas, greatly reducing the power consumption and cost of multifunctional electronic systems. When the antenna is located at different positions on the focal plane of the lens and can move freely, the transmitted beam points in different directions, which is not conducive to engineering implementation and practical applications. When the antenna array is fixed, it is easy to implement in engineering but cannot achieve free beam scanning. Summary of the Invention

[0005] The purpose of this invention is to provide a method for continuous multi-beam scanning of an active phased array loaded with an electromagnetic lens based on beam pattern synthesis, so as to solve the problem that an active phased array loaded with an electromagnetic lens cannot achieve free scanning of multiple beams.

[0006] The technical solution to achieve the objective of this invention is: a multi-beam continuous scanning method for an active phased array with electromagnetic lens loading, the method comprising the following steps:

[0007] Step 1: Construct an active phased array antenna system with electromagnetic lens loading;

[0008] Step 2: In the CST electromagnetic simulation software, continuously change the position of the active phased array antenna to obtain the beam pattern of each radiation direction and use it as a reference beam pattern.

[0009] Step 3: Set the desired transmission and reception direction, use the reference beam pattern as the fitting object, and use the digital T / R component to perform weighted processing on the antenna array elements to achieve continuous multi-beam scanning; wherein, the weighting coefficients are obtained by using the beam pattern synthesis method to minimize the maximum error between the weighted antenna array beam pattern and the reference beam pattern.

[0010] Furthermore, the construction of the electromagnetic lens-loaded active phased array system described in step 1 specifically includes:

[0011] An electromagnetic lens is placed at the front end of a uniform linear array, with the uniform linear array positioned on the focal plane of the electromagnetic lens. The central element of the uniform linear array is located at the central focal point of the electromagnetic lens, and the remaining antenna elements are symmetrically distributed on both sides of the central element.

[0012] Furthermore, the method of beam pattern synthesis described in step 3 minimizes the maximum error between the weighted antenna array beam pattern and the reference beam pattern. The specific process includes:

[0013] Step 4-1, construct the weighted array factor of the array antenna with loaded lenses as follows:

[0014]

[0015] In the formula, k represents the number of the antenna array element, n and m represent the numbers of the electromagnetic lens elements on the horizontal and vertical axes, respectively, and A(n,m) and ψ(n,m) represent the amplitude response and phase response of the (n,m)th lens element, respectively. l nLet be the distance from the (n,m)th lens element to the focal point, l1 be the focal length of the lens, and λ be the wavelength of the plane wave; V(n,m,i) represents the incident electric field intensity of the i-th antenna element at the (n,m)th lens element due to free space propagation loss, r(n,m,i) represents the distance from the i-th antenna element to the (n,m)th lens element, and d u The distance between adjacent lens units is θ, where θ represents the azimuth angle of the beam pointing, and af i (θ) represents the array factor of the i-th antenna element operating alone, w i is the weighting coefficient for the i-th antenna element;

[0016] Step 4-2, express the weighting coefficients and matrix factors in matrix form:

[0017] W = [w -k ,…w0,…w k ] T

[0018] F(θ) = [af] -k (θ),…af0(θ),af k (θ)]

[0019] Step 4-3, Establish the optimization model:

[0020]

[0021] In the formula, ||·|| ∞ Let θ represent the infinite norm, Θ represent the range of the set of θ, ||·||1 represent the 1-norm, and d(θ) represent the beam pattern corresponding to the desired transmission / reception direction. If the desired transmission / reception direction is single, then d(θ) is the reference beam pattern corresponding to that direction. If the desired transmission / reception direction is multiple, then d(θ) is the sum of the reference beam patterns corresponding to each transmission / reception direction. σ is a tradeoff factor. σ≥0. A smaller value of σ results in higher accuracy of the optimization result, but requires more antennas, increasing system cost and power consumption. A larger value of σ results in lower accuracy of the optimization result, but requires fewer antennas, reducing system cost and power consumption.

[0022] Step 4-4: Use the convex optimization calculation tool CVX to solve the optimization model and obtain the weighted values ​​of the antenna elements.

[0023] Compared with existing technologies, the significant advantages of this invention are: 1) Compared with traditional phased array antenna arrays, only a few antennas need to operate to achieve high-gain beams, greatly saving hardware costs. 2) Compared with other array antennas with loaded lenses, the method proposed in this invention can achieve continuous beam scanning and is easy to implement in engineering.

[0024] The present invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of an active phased array antenna system with an electromagnetic lens loading in one embodiment.

[0026] Figure 2 Figure (a) shows the schematic diagram and simulation diagram of an electromagnetic lens in one embodiment, and Figure (b) shows the simulation diagram in CST electromagnetic simulation software.

[0027] Figure 3 This is a schematic diagram of a linear array model with loaded lenses in one embodiment.

[0028] Figure 4 This is the far-field radiation pattern corresponding to nine antennas in one embodiment. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0030] In one embodiment, a method for multi-beam continuous scanning of an active phased array loaded with an electromagnetic lens is provided, the method comprising the following steps:

[0031] Step 1: Construct an active phased array antenna system with electromagnetic lens loading;

[0032] Step 2: In the CST electromagnetic simulation software, continuously change the position of the active phased array antenna to obtain the beam pattern of each radiation direction and use it as a reference beam pattern.

[0033] Step 3: Set the desired transmission and reception direction, use the reference beam pattern as the fitting object, and use the digital T / R component to perform weighted processing on the antenna array elements to achieve continuous multi-beam scanning; wherein, the weighting coefficients are obtained by using the beam pattern synthesis method to minimize the maximum error between the weighted antenna array beam pattern and the reference beam pattern.

[0034] Furthermore, in one embodiment, combined with Figure 1 Step 1, which describes the construction of an active phased array system with electromagnetic lens loading, specifically includes:

[0035] An electromagnetic lens is placed at the front end of a uniform linear array, with the uniform linear array positioned on the focal plane of the electromagnetic lens. The central element of the uniform linear array is located at the central focal point of the electromagnetic lens, and the remaining antenna elements are symmetrically distributed on both sides of the central element.

[0036] Furthermore, in one embodiment, the method of beammap synthesis described in step 3 minimizes the maximum error between the weighted antenna array beammap and the reference beammap. The specific process includes:

[0037] Step 4-1, construct the weighted array factor of the array antenna with loaded lenses as follows:

[0038]

[0039] In the formula, k represents the number of the antenna array element, n and m represent the numbers of the electromagnetic lens elements on the horizontal and vertical axes, respectively, and A(n,m) and ψ(n,m) represent the amplitude response and phase response of the (n,m)th lens element, respectively. l n Let be the distance from the (n,m)th lens element to the focal point, l1 be the focal length of the lens, and λ be the wavelength of the plane wave; V(n,m,i) represents the incident electric field intensity of the i-th antenna element at the (n,m)th lens element due to free space propagation loss, r(n,m,i) represents the distance from the i-th antenna element to the (n,m)th lens element, and d u The distance between adjacent lens units is θ, where θ represents the azimuth angle of the beam pointing, and af i (θ) represents the array factor of the i-th antenna element operating alone, w i is the weighting coefficient for the i-th antenna element;

[0040] Step 4-2, express the weighting coefficients and matrix factors in matrix form:

[0041] W = [w -k ,…w0,…w k ] T

[0042] F(θ) = [af] -k (θ),…af0(θ),af k (θ)]

[0043] Step 4-3, Establish the optimization model:

[0044]

[0045] In the formula, ||·|| ∞Let θ represent the infinite norm, Θ represent the range of the set of θ, ||·||1 represent the 1-norm, and d(θ) represent the beam pattern corresponding to the desired transmission / reception direction. If the desired transmission / reception direction is single, then d(θ) is the reference beam pattern corresponding to that direction. If the desired transmission / reception direction is multiple, then d(θ) is the sum of the reference beam patterns corresponding to each transmission / reception direction. σ is a tradeoff factor. σ≥0. A smaller value of σ results in higher accuracy of the optimization result, but requires more antennas, increasing system cost and power consumption. A larger value of σ results in lower accuracy of the optimization result, but requires fewer antennas, reducing system cost and power consumption.

[0046] Step 4-4: Use the convex optimization calculation tool CVX to solve the optimization model and obtain the weighted values ​​of the antenna elements.

[0047] As a specific example, the invention will be further described in one embodiment. The spherical wave radiated by the omnidirectional antenna, after having its amplitude and phase altered by an electromagnetic lens, forms a high-gain plane wave beam with a gain of 22.3 dB. Correspondingly, a perpendicularly incident plane wave can be focused to the focal point by the lens. The working principle of the lens is as follows... Figure 2 As shown. The electromagnetic lens used in this embodiment is a millimeter-wave planar lens with dimensions of 100mm × 100mm and an operating frequency of 28-32GHz. It consists of various circular lens units with different radii, the diameter of which varies from 1mm to 2.5mm. The amplitude-frequency response of the lens unit is almost 1 within the operating frequency range, while the phase response difference between adjacent units is approximately 30°.

[0048] Taking a uniform linear array with nine elements as an example, with an element spacing of 5mm, a mathematical model is performed on the array with loaded lenses, such as... Figure 3 As shown. Let the central element of the lens be located at the origin of the coordinate system, and the lens be located on the xoy plane. Then the coordinates of each lens element are (n, m, 0), where n represents the element number on the x-axis (-15 ≤ n ≤ 15), and m represents the element number on the y-axis (-15 ≤ m ≤ 15). n and m satisfy the relationship m... 2 +n 2 <266. The distance between adjacent lens units is d. u =3mm, antenna element 0 is located at the focal point of the lens (0,0,-f) d At position ), the remaining array elements are arranged symmetrically about the central array element, with an element spacing of d. e =5mm. Assuming the antenna elements are omnidirectional antennas with no directivity, and the lens is located in the far field of the antenna array, let each of the 9 antennas in the array transmit a linear frequency modulated signal with a center frequency of 30GHz and a bandwidth of 500MHz. Figure 4 The corresponding nine far-field beammaps are displayed. (By...) Figure 4It can be seen that the beam patterns of the nine antennas point to 18.6°, 14°, 9.3°, 4.7°, 0°, -4.7°, -9.3°, -14°, and -18.6°, respectively. To achieve flexible beam scanning of the lens-loaded array, the array antennas can be weighted. Through mathematical derivation, the weighting factor of the lens-loaded array antenna can be obtained as follows:

[0049]

[0050] Define the weighted coefficient matrix and the matrix factor matrix as follows:

[0051] W = [w -k ,…w0,…w k ] T

[0052] F(θ) = [af] -k (θ),…af0(θ),af k (θ)]

[0053] The radiation pattern of an antenna array with a loaded lens depends on the location of the antenna. Taking advantage of this characteristic, the beam angle can be changed by freely moving the antenna. The beam patterns of each radiation direction can be obtained using CST simulation software and recorded as reference beam patterns.

[0054] Let d(θ) represent the beam pattern corresponding to the desired transmission and reception directions, and establish an optimization model:

[0055]

[0056] In the formula, ||·|| ∞ Θ represents the infinity norm, and Θ represents the range of the set θ. ||·||1 represents the 1-norm, which aims to include as many w as possible. i Setting it to 0 means the antenna doesn't need power supply, reducing system cost and power consumption. σ is a trade-off factor; a smaller σ value results in higher optimization accuracy but requires more antennas, increasing system cost and power consumption. A larger σ value results in lower optimization accuracy but requires fewer antennas, reducing system cost and power consumption. In this embodiment, σ is set to 4, minimizing the number of antennas used while ensuring optimization accuracy. To achieve simultaneous multi-beam scanning, the desired radiation patterns d of each beam are... i By adding (θ) and substituting the overall desired beam pattern d(θ) of the multi-beam array into the optimization model, the corresponding antenna weighting coefficients can be solved, thereby realizing continuous multi-beam scanning of the active phased array array loaded with electromagnetic lenses.

[0057] Compared to traditional phased array antenna arrays, this invention requires only a few antennas to operate to achieve high-gain beams, significantly reducing hardware costs. Furthermore, compared to other lens-loaded array antennas, the method proposed in this invention enables continuous beam scanning and is easier to implement in engineering.

[0058] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for multi-beam continuous scanning of an active phased array with electromagnetic lens loading, characterized in that, The method includes the following steps: Step 1: Construct an active phased array antenna system with electromagnetic lens loading; Step 2: In the CST electromagnetic simulation software, continuously change the position of the active phased array antenna to obtain the beam pattern of each radiation direction and use it as a reference beam pattern. Step 3: Set the desired transmission and reception directions, use the reference beammap as the fitting object, and use a digital T / R component to weight the antenna array elements to achieve continuous multi-beam scanning; wherein, the weighting coefficients are obtained by using beammap synthesis to minimize the maximum error between the weighted antenna array beammap and the reference beammap; the specific process includes: Step 4-1, construct the weighted array factor of the array antenna with loaded lenses as follows: In the formula, k represents the number of the antenna array element, and n and m represent the numbers of the electromagnetic lens elements on the horizontal and vertical axes, respectively. and Let represent the amplitude response and phase response of the (n, m)th lens unit, respectively. , l n Let l be the distance from the (n,m)th lens unit to the focal point, and l1 be the focal length of the lens. The wavelength of a plane wave; This represents the incident electric field intensity of the i-th antenna element at the (n,m)-th lens element due to free-space propagation loss. This represents the distance from the i-th antenna element to the (n, m)-th lens element. This represents the distance between adjacent lens units. Indicates the azimuth angle of the beam direction. This represents the array factor of the i-th antenna element operating alone. is the weighting coefficient for the i-th antenna element; Step 4-2, express the weighting coefficients and matrix factors in matrix form: Step 4-3, Establish the optimization model: In the formula, Represents the infinite norm, represent The range of the set, Represents the 1-norm, This represents the beam pattern corresponding to the desired transmission and reception direction. If the desired transmission and reception direction is single, then... This is the reference beam pattern for that direction. If multiple transmission and reception directions are desired, then... Sum the reference beam patterns for each transmit and receive direction; It is a trade-off factor. , Smaller values ​​result in higher accuracy of the optimization results, but also require more antennas, increasing system cost and power consumption. Larger values ​​result in lower accuracy of the optimization results, but require fewer antennas, reducing system cost and power consumption. Step 4-4: Use the convex optimization calculation tool CVX to solve the optimization model and obtain the weighted values ​​of the antenna elements.

2. The method for multi-beam continuous scanning of an active phased array with electromagnetic lens loading according to claim 1, characterized in that, Step 1, which describes the construction of an active phased array system with electromagnetic lens loading, specifically includes: An electromagnetic lens is placed at the front end of a uniform linear array, with the uniform linear array positioned on the focal plane of the electromagnetic lens. The central element of the uniform linear array is located at the central focal point of the electromagnetic lens, and the remaining antenna elements are symmetrically distributed on both sides of the central element.

3. The method for multi-beam continuous scanning of an active phased array with electromagnetic lens loading according to claim 1, characterized in that, The electromagnetic lens is a millimeter-wave band dual-period metamaterial electromagnetic lens.

4. The method for multi-beam continuous scanning of an active phased array with electromagnetic lens loading according to claim 3, characterized in that, The millimeter-wave band dual-periodic metamaterial electromagnetic lens has a size of It operates at a frequency of 28-32GHz and includes various circular lens units with different radii, the diameter of which varies from 1mm to 2.5mm.

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