A high-precision beamforming method for non-uniform phased array antennas

Abstract

The present invention discloses a high-precision beamforming method for non-uniform phased array antennas. The method can rapidly calculate the feed phase distribution required for beamforming of a non-uniform antenna array based on the main polarization far-field phase distribution of each array element, thereby achieving precise beam pointing of the non-uniform antenna array. The method comprises the following steps: T1: in an n-element antenna array, sequentially exciting each antenna element to measure their respective main polarization far-field phase information #imgabs0#; T2: taking the conjugate #imgabs1# of the main polarization far-field phase information of each antenna element; T3: when the antenna array beam is pointed at #imgabs2#, calculating the feed phase distribution of each antenna element as #imgabs3#; T4: performing constant-amplitude feeding of the antenna array using the feed phase distribution obtained in T3; wherein θ represents the direction of the beam pointing away from the line of sight, and #imgabs4# represents the angle of the beam from the horizon.

Description

Technical Field

[0001] The present invention relates to an antenna shaping method, and in particular to a high-precision beamforming method for a non-uniform phased array antenna. Background Art

[0002] Satellite communications, with their wide coverage, available bandwidth, rapid network deployment, and low cost, have led to widespread application in military, satellite communications, electronic navigation, remote sensing, and telemetry fields. The development of satellite communications has necessitated the use of multi-feed shaped or shaped reflector antennas to meet the effective isotropic radiated power requirements of a specific ground service area, significantly promoting their development. This reduces interference from ground stations outside the coverage area, improves system spectrum utilization and channel capacity, enhances the effective isotropic radiated power (EIRP) and the receiving system's quality factor (G / T), and simplifies and reduces the cost of satellite ground station terminal equipment.

[0003] A phased array antenna is an antenna that changes the shape of its radiation pattern by controlling the feeding phase of the radiating elements in the antenna array. Controlling the phase can change the direction of the maximum value of the antenna radiation pattern to achieve the purpose of beam scanning. There are two feeding methods for phased array antennas: transmission line feeding and space feeding. In the transmission line feeding method, the RF energy is fed to the radiating element through microwave transmission lines such as waveguides, coaxial lines, and microstrip lines (see microstrip lines and quasi-microstrip lines), and the phase shifter is placed in the microwave transmission line. In the space feeding method, the RF energy generated by the transmitter is radiated into free space through the radiating device. After transmitting for a certain distance, it is received by a receiving array. The signal received by each element or group of elements in the receiving array is phase-shifted by the phase shifter and then fed to the transmitting element of the transmitting array and radiated out. The phase shifter is located between the transmitting array and the receiving array.

[0004] Phased array antenna technology enables high-speed scanning and flexible beamforming without mechanical motion. Analytical methods such as Fourier transform, Taylor synthesis, and Chebyshev synthesis offer advantages such as low computational effort, high speed, and good computational stability when calculating simple, regular linear or planar arrays. However, because these methods do not consider coupling between elements or between the array and the carrier, when applied to non-uniform arrays (such as conformal antenna arrays, sparsely spaced antenna arrays, and phased array lens antenna arrays), the resulting beam may differ significantly from the desired beam. Summary of the Invention

[0005] This paper proposes a high-precision beamforming method for non-uniform phased array antennas. Based on the far-field phase distribution of the main polarization of each array element, the method rapidly calculates the feed phase distribution required for beamforming the non-uniform antenna array, thereby achieving precise beam pointing for the non-uniform antenna array. This is achieved through the following technical solutions:

[0006] T1: In an n-element antenna array, each antenna element is excited in turn to measure the main polarization far-field phase information of each element. Where θ represents the distance between the beam pointing and the boresight line of sight. Indicates the angle of the beam from the horizon.

[0007] Antenna measurements can be divided into near-field and far-field testing, depending on the distance from the antenna being measured. Near-field testing studies the amplitude, phase, and spectrum of the antenna's near field, then uses Fourier transform to obtain the far-field amplitude, phase, and pattern, ultimately reconstructing the far-field distribution of the antenna's radiation field. Far-field testing directly measures the far-field data of the antenna under test. Near-field antenna measurements are subject to errors caused by multipath effects and external interference, making far-field testing more reliable.

[0008] T2: Take the conjugate of the main polarization far-field phase information of each array antenna element

[0009] Phase conjugation technology involves performing complex conjugation on the phase of a light wave in both time and space. Mathematically, this is equivalent to performing a complex conjugation operation on the wavefront. A device capable of this function is called a phase conjugation mirror. The complex conjugated wave obtained by the phase conjugation mirror is equivalent to a time-reversed wave and can be returned along the original propagation path. Based on this property, phase conjugation technology can be used to compensate for light field distortion caused by disturbances such as scattering, thereby restoring biological image information. Optical focusing and energy transmission within biological tissue have long been key to bio-optical imaging. However, due to multiple scattering, photons diffuse significantly within biological tissue, limiting the depth of the incident light and the energy transfer, thus restricting imaging depth and quality. Currently, some experiments have combined phase conjugation technology with ultrasonic modulation to compensate for scattering distortion, achieving optical focusing within scattering media. Applying optical phase conjugation technology to antenna array shaping can improve the beamforming accuracy of non-uniform antenna arrays.

[0010] T3: Antenna array beam pointing When , the feeding phase distribution of each array antenna unit is calculated as

[0011] T4: The antenna array is fed using the feeding phase distribution obtained in T3.

[0012] On the basis of the above scheme, further measures are as follows:

[0013] Obtain the main polarization far-field phase information of each antenna element in step T1 by scanning the microwave darkroom measurement system

[0014] On the basis of the above scheme, further measures are as follows:

[0015] After T4 is fed, the antenna array beam pointing is verified through microwave anechoic chamber measurements.

[0016] A microwave anechoic chamber utilizes shielding materials to block external electromagnetic interference, while absorbing materials suppress internal electromagnetic multipath reflection interference. The combination of these two creates a relatively quiet electromagnetic measurement environment. It provides a low-level, constant electromagnetic environment, improving measurement accuracy and reliability. In antenna design, antenna performance significantly impacts wireless communication performance. Antenna testing is a crucial means of determining whether antenna performance indicators meet requirements. Microwave anechoic chamber testing can eliminate clutter interference, improving test accuracy and efficiency for devices under test (DUTs), and is widely used in antenna development and testing.

[0017] On the basis of the above scheme, further measures are as follows:

[0018] In step T1, when each antenna element is excited in sequence, it is excited in phase. The in-phase excitation makes the measured effects of the coupling between the elements of each antenna element and the coupling between the array and the carrier on the main polarization far-field phase information the same or similar, thereby reducing the impact of the system on the feeding phase.

[0019] On the basis of the above scheme, further measures are as follows:

[0020] When the antenna array is fed using the feeding phase distribution obtained in step T3 in step T4, the antenna units of each array are excited with equal amplitude at the same time.

[0021] Based on the above solution, further embodiment is as follows: the antenna array may be a conformal antenna array.

[0022] A conformal antenna array is a type of antenna designed to closely conform to the platform's shape. This design offers excellent adaptability to vibrations and changes in the platform's shape caused by aerodynamic, structural, and thermal factors during operation, thereby reducing radar cross-section. The surface of a conformal antenna array is typically curved, and the array conforms to the surface, maintaining the same shape as the surface. Typically, conformal antenna arrays are cylindrical, spherical, or conical, with components integrated onto a smooth, curved surface. While the shape of a planar array is determined by the antenna's electromagnetic performance (such as beam shape and angular coverage), the shape of a conformal array must consider not only the antenna's electrical performance but also the aerodynamic characteristics of the platform. For conformal antenna arrays, excessively small spacing between antenna elements can lead to significant coupling issues. High coupling between antenna elements can degrade antenna performance, altering its gain, main lobe width, and other parameters. For aircraft, this coupling can even lead to blind spots in the antenna's scanning. Therefore, the coupling suppression of conformal antenna array elements is very important to the antenna performance. The coupling between elements and the coupling between the array and the carrier are factors that cannot be ignored.

[0023] Based on the above solution, further embodiment is as follows: the antenna array may be a phased array lens antenna array.

[0024] Phased array lens antennas are highly directional antennas that convert spherical or cylindrical waves from point or line sources into plane waves, thereby generating pencil-shaped, fan-shaped, or other beam shapes. According to geometric optics theory, spherical waves radiated from a point source at the lens's focal point are refracted and converged by the lens, ultimately forming a plane wave. This is the general concept behind lens antenna design. A lens antenna consists of a lens and an electromagnetic radiator. Electromagnetic waves exhibit wave-particle duality, and when they propagate through non-parallel media, they refract. Installing a lens in front of the radiator concentrates the radiated energy and narrows the beam. Compared to other antennas, under the same conditions, lens antennas offer unique advantages: primarily, they offer a wider angular scanning range and effectively suppress sidelobes and backlobes. They also enhance directivity and achieve a certain gain improvement. Compared to reflectors, lens antennas have a slightly more complex structure, but they are less expensive and easier to manufacture. While simple electromagnetic radiators typically have very weak directivity, adding a lens allows for better control of the radiation beam direction and width.

[0025] Based on the above solution, further embodiment is as follows: the antenna array may be a dipole antenna array.

[0026] The dipole antenna is the earliest, simplest, and most widely used type of antenna in radio communications. It consists of a pair of symmetrically placed conductors, each connected to a feeder at its closest end. When used as a transmitting antenna, the electrical signal is fed into the conductors from the center of the antenna; when used as a receiving antenna, the received signal is also received from the conductors at the center of the antenna. A common dipole antenna consists of two coaxial straight conductors. The radiation field generated by this antenna at a distance is axisymmetric and can be rigorously calculated in theory. Dipole antennas are resonant antennas. Theoretical analysis shows that the current distribution within a slender dipole antenna exhibits a standing wave pattern, with the wavelength of the standing wave being exactly the wavelength of the electromagnetic wave generated or received by the antenna. Therefore, when designing a dipole antenna, the operating wavelength is used to determine the antenna's length. The most common dipole antenna is the half-wave antenna, whose total length is approximately half the operating wavelength. In addition to half-wave antennas constructed with straight conductors, other types of dipole antennas are also used, such as full-wave antennas and short antennas constructed with straight conductors, as well as more complex cage antennas and batwing antennas.

[0027] This application avoids the problems of conventional time reversal algorithms for antenna shaping, such as high difficulty, high resource consumption, and high time consumption. It uses microwave anechoic chamber measurements to obtain the far-field information of the array antenna units, and then uses algorithm calculations to simply, quickly, and efficiently obtain the antenna shaping phase, so that the shaped beam is highly consistent with the desired beam.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] 1. The present invention can quickly calculate the feed phase distribution required for non-uniform antenna array beamforming based on the main polarization far-field phase distribution of each array unit, thereby achieving precise pointing of the non-uniform antenna array beam.

[0030] 2. The present invention utilizes a microwave darkroom test system to sequentially excite individual units to obtain their main polarization far-field information, and then uses an algorithm to process the test data to obtain the phase information of the antenna configuration.

[0031] 3. The algorithm proposed in this invention is efficient, convenient, and takes up few resources. It can be used not only for shaping special antennas such as conformal antennas, phased array lens antennas, and sparsely distributed antenna arrays, but also for shaping conventional arrays such as dipole antenna arrays. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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 examples. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort. In the drawings:

[0033] Figure 1 A schematic diagram of the non-uniform phased array antenna structure in an embodiment;

[0034] Figure 2 is the antenna shaped pattern obtained in the embodiment.

[0035] The numbers and corresponding component names in the drawings are: 1 - first antenna unit, 2 - second antenna unit, 3 - third antenna unit, 4 - fourth antenna unit, 5 - fifth antenna unit, 6 - sixth antenna unit, 7 - seventh antenna unit, 8 - eighth antenna unit, 9 - ninth antenna unit, 10 - tenth antenna unit, 11 - eleventh antenna unit, 12 - twelfth antenna unit, 13 - thirteenth antenna unit, 14 - fourteenth antenna unit.

[0036] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0037] 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 examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0038] In the following description, numerous specific details are set forth to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that these specific details are not necessarily required to practice the present invention. In other embodiments, well-known structures, circuits, materials, or methods are not described in detail to avoid obscuring the present invention.

[0039] Throughout this specification, references to "one embodiment," "an embodiment," "an example," or "an example" mean that a particular feature, structure, or characteristic described in connection with the embodiment or example is included in at least one embodiment of the present invention. Therefore, appearances of the phrases "one embodiment," "an embodiment," "an example," or "an example" in various places throughout this specification are not necessarily all referring to the same embodiment or example. Furthermore, the particular features, structures, or characteristics may be combined in one or more embodiments or examples in any suitable combinations and / or subcombinations. Furthermore, it will be understood by those of ordinary skill in the art that the figures provided herein are for illustrative purposes only and are not necessarily drawn to scale. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0040] In the description of the present invention, the terms "upper" and "between" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the scope of protection of the present invention.

[0041] In an n-element antenna array, n can be any suitable value, such as Figure 1 As shown, in one embodiment of the present invention, n=14, 14 array antenna units are conformally arranged on a curved surface, and the mutual spacing between the array antenna units is randomly generated, forming a dipole conformal sparse antenna array. The array shaping process is as follows:

[0042] The first to fourteenth antenna units are excited in sequence with equal amplitude and phase. The main polarization far-field phase information of the first antenna unit is measured by the microwave darkroom measurement system. The main polarization far-field phase information of the second array antenna element is: ...The main polarization far-field phase information of the fourteenth antenna element is θ represents the distance between the beam pointing and the boresight line, Indicates the angle of the beam from the horizon. Equal-amplitude excitation and in-phase excitation ensure that the coupling between antenna elements and the coupling between the array and the carrier have the same or similar effects on the main polarization far-field phase information, thereby reducing the impact of the system on the feeding phase.

[0043] When the beam pointing is θ=25°, The main polarization far-field phase distribution of the first to fourteenth antenna units is shown in the following table.

[0044] unit 1 2 3 4 5 6 7 Phase (°) -57.15 -86.58 -156.78 61.25 -54.44 -73.60 119.25 unit 8 9 10 11 12 13 14 Phase (°) -33.17 -63.77 -144.72 56.45 -92.08 -88.97 -135.85

[0045] When the antenna scans to θ=25, When the first antenna unit feed phase is required to be A1(25,0)=A1′(25,0) * , the second antenna unit feed phase is A2(25,0)=A2′(25,0) * , ... the feed phase of the fourteenth antenna unit is A 14 (25,0)=A 14 ′(25,0) * The array feed phase distribution of the first to fourteenth array antenna units is calculated by the algorithm and is shown in the following table.

[0046]

[0047]

[0048] The antenna array uses the feed phase distribution in the table above and excites the array with equal amplitude. The antenna array beam pointing direction is verified by microwave darkroom measurement. Figure 2 As shown, precise pointing is achieved.

[0049] A microwave anechoic chamber utilizes shielding materials to block external electromagnetic interference, while absorbing materials suppress internal electromagnetic multipath reflection interference. The combination of these two creates a relatively quiet electromagnetic measurement environment. It provides a low-level, constant electromagnetic environment, improving measurement accuracy and reliability. In antenna design, antenna performance significantly impacts wireless communication performance. Antenna testing is a crucial means of determining whether antenna performance indicators meet requirements. Microwave anechoic chamber testing can eliminate clutter interference, improving test accuracy and efficiency for devices under test (DUTs), and is widely used in antenna development and testing.

[0050] The technical solution in this embodiment rapidly calculates the feed phase distribution required for beamforming a non-uniform antenna array based on the far-field phase distribution of each array element's main polarization. This avoids the difficulty, resource intensiveness, and time-consuming nature of conventional time-reversal algorithms for antenna beamforming. Far-field information of the array's antenna elements is measured in a microwave anechoic chamber, and algorithmic calculations allow for simple, rapid, and efficient antenna beamforming and phase matching. The proposed algorithm is efficient, convenient, and resource-efficient, and can be used for beamforming special antennas such as conformal antennas and phased array lens antennas, as well as conventional arrays such as dipole antenna arrays.

[0051] The specific implementation methods described above further explain in detail the purpose, technical solutions and beneficial effects of the present invention. 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 equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A high-precision beamforming method for a non-uniform phased array antenna, characterized in that: The steps include: T1: In an n-element antenna array, each antenna element is excited in turn to measure the main polarization far-field phase information of each element. T2: Take the conjugate of the main polarization far-field phase information of each array antenna element T3: Antenna array beam pointing When , the feeding phase distribution of each array antenna unit is calculated as T4: The antenna array is fed using the feeding phase distribution obtained in T3; Where θ represents the distance between the beam pointing and the boresight line of sight. Indicates the angle of the beam from the horizon.

2. The high-precision beamforming method for a non-uniform phased array antenna according to claim 1, characterized in that: The main polarization far-field phase information of each antenna element in step T1 is obtained by scanning the microwave darkroom measurement system.

3. The high-precision beamforming method for a non-uniform phased array antenna according to claim 1, characterized in that: After T4 is fed, the antenna array beam pointing is verified through microwave anechoic chamber measurements.

4. The high-precision beamforming method for a non-uniform phased array antenna according to claim 1, characterized in that: In step T1, when the antenna units of each array are excited in sequence, the excitation is performed in phase.

5. The high-precision beamforming method for a non-uniform phased array antenna according to claim 1, characterized in that: In step T1, when each antenna element is excited in sequence, the excitation is performed with equal amplitude and in phase.

6. The high-precision beamforming method for a non-uniform phased array antenna according to claim 1, characterized in that: When the antenna array is fed using the feeding phase distribution obtained in step T3 in step T4, the antenna units of each array are excited with equal amplitude at the same time.

7. The high-precision beamforming method for a non-uniform phased array antenna according to claim 1, characterized in that: The antenna array is a dipole antenna array.

8. The high-precision beamforming method for a non-uniform phased array antenna according to claim 1, characterized in that: The antenna array is a conformal antenna array.

9. The high-precision beamforming method for a non-uniform phased array antenna according to claim 1, characterized in that: The antenna array is a phased array lens antenna array.

10. The high-precision beamforming method for a non-uniform phased array antenna according to claim 1, characterized in that: The antenna array is a sparsely distributed antenna array.

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