Beam vector superposition method for multi-beam antenna design

Abstract

The invention relates to the technical field of antennas, in particular to a beam vector superposition method for multi-beam antenna design, which comprises the following steps: firstly, acquiring directional diagram information of a feed source antenna, then presetting a longitudinal distance from a lens focal plane to a feed source, the number of plane grids and unit width, then acquiring basic requirements of multiple beams, and according to a target requirement, calculating a multi-beam vector according to the target requirement; dielectric units are designed, S parameters and phase characteristics of the units are evaluated, finally, phase distribution needing to be compensated by the lens is obtained through a phase compensation scheme of a beam vector superposition algorithm, and the dielectric units are reasonably arranged. In addition, the feasibility and effectiveness of the method are verified by manufacturing a test prototype. A simulation experiment verifies that flexible control of the number of multiple beams and free adjustment of sub-beam pointing can be realized, and improvement of gain of each sub-beam, narrowing of beam width, low sidelobe level and deepest null can be realized under the condition that the requirements of the number of the beams, the sub-beam pointing and the like are met.

Description

Technical Field

[0001] The present invention relates to the field of antenna technology, and in particular to a beam vector superposition method for multi-beam antenna design. Background Art

[0002] With the rapid development of the wireless communication industry due to the huge data volume demand, multi-beam antennas (MBAs) have become the key to multi-channel, multi-angle multiplexing and increasing channel capacity in the field of wireless communications. It can effectively reduce co-channel crosstalk and improve spectrum efficiency and transmission rate.

[0003] Phased array antennas (PAAs) are widely used in MBAs because of their flexible and changeable beams. They control the antenna elements separately through the feed link to provide the appropriate amplitude and phase for the elements. This dynamically changes the direction and shape of the antenna beam to achieve rapid scanning and formation of multiple beams. Different beam shapes (for example, high-pointing beams, multi-beams, or flat-top beams) can be flexibly switched according to the application scenario requirements. However, the feed link involves the integration of multiple chips such as power amplifier chips, low-noise amplifier chips, RF switches, phase shifters, and control circuits. This not only increases the complexity of PAAs, but also increases the processing cost and the difficulty of antenna integration.

[0004] In order to reduce the complexity and cost of MBAs, another MBA solution is to improve the spectrum efficiency by adding multiple input ports in the antenna. They are a traditional MBA beamforming network (BFNs). BFNs are mainly divided into passive circuit form and lens form. Passive circuit forms include Butler matrix, coupling matrix, Brass matrix, etc. They are widely used in rectangular waveguides, substrate integrated waveguides (SIW), coupled slot arrays. Lens forms mainly include Rodman lens, cylindrical lens and Luneburg lens, etc. They use multiple feed sources to feed independently or in combination to realize multi-beam. The number of feed sources and the array rules determine the number of beams and the pointing angle of the MBA. MBAs based on BFNs have poor beam flexibility. Large lenses and multiple feed sources make the overall size of the antenna larger and bulky.

[0005] Metasurface antennas (MAs) are widely used to improve antenna gain due to their simple structure, light weight and easy manufacturing. The spherical wave emitted by the feed is converted into a plane wave to achieve the effect of increasing the gain. However, for MBAs, the positions of multiple feeds are different. The metasurface cannot achieve good phase compensation for each feed, resulting in poor beam pointing accuracy and low gain of MBAs. Some new metasurface phase compensation methods have been proposed. Corresponding phase compensation is achieved for feeds at different positions, thereby improving the gain of MBAs. However, they can only perform multi-beam pointing in one dimension, and the working bandwidth of the antenna is narrow. With the continuous development of 3D printing technology, the broadband characteristics, light weight and easy manufacturing advantages of dielectric lens antennas (DLAs) have been highlighted. Since there is no metal structure in DLAs, they exhibit wide bandwidth characteristics. The way to achieve multi-beam is often to move the feed position, multi-feed input or Butler matrix. This increases the complexity of DLAs and the overall size of the antenna. Therefore, it is very critical to use a single feed for feeding to achieve multi-beam pointing. However, in the relevant reports on single-feed multi-beam dielectric lens antennas, there are few principle comparisons of different phase compensation methods and performance comparative analyses of the designed MBAs.

[0006] The classic solution for metasurfaces to achieve multi-beam is to use 1-bit phase for encoding and arrangement. By adjusting the phase of the 2π periodic change on the focal plane to -π and π, that is, the phase superposition algorithm (PSA), the function of converting a single beam into a dual beam or a quad beam can be achieved. However, beams always appear in pairs and symmetrically, and the direction of the sub-beams cannot be controlled individually. The quadrant superposition algorithm (QSA) was proposed to achieve multiple and asymmetric beam pointing. This method divides the physical aperture of the transmission array or reflection array into regions. Each sub-region controls the sub-beams in this region. As the number of beams increases, the number of regions where the aperture is divided will also increase. This will cause phase interference at the junction of the sub-regions, resulting in a decrease in the performance of the sub-beams. Summary of the invention

[0007] The purpose of the present invention is to provide a beam vector superposition method for multi-beam antenna design, aiming to achieve flexible control of the number of multi-beams, sub-beam pointing, beam width and gain, and to use 3D printing technology to reduce the manufacturing cost of the multi-beam antenna to better adapt to more scene requirements.

[0008] To achieve the above object, the present invention provides a beam vector superposition method for multi-beam antenna design, comprising the following steps:

[0009] Step 1: Obtain the directional pattern information of the feed antenna;

[0010] Step 2: Preset the longitudinal distance between the focal plane of the lens and the feed source, the number of plane grids, and the unit width;

[0011] Step 3: Obtain the basic requirements of multi-beam;

[0012] Step 4: Design the dielectric unit and evaluate the S parameters and phase characteristics of the unit according to the target requirements;

[0013] Step 5: Obtain the phase distribution required for lens compensation through the phase compensation scheme of the beam vector superposition algorithm, and arrange the dielectric units reasonably;

[0014] Step 6: Make a test prototype to verify feasibility and effectiveness.

[0015] Optionally, in step 1, a horn antenna is selected as the feed antenna, operating in the E band, and the -10 dB beam widths of the E plane, the H plane, and the D plane are screened out through the far-field pattern information of the feed antenna.

[0016] Optionally, the phase difference value at the focal plane in step 2 is recorded as φ h (x,y), the expression is as follows:

[0017]

[0018] Among them, the center of the plane (x 0 ,y 0 ) is set to 0°. As the unit U(x,y) moves away from the origin, φ h (x,y) shows periodic changes.

[0019] Optionally, the phase distribution corresponding to the multi-beam pattern in step 3 is φ bi The calculation formula for (x,y) is as follows:

[0020] φ bi (x,y)=kd(cos(φ i )sin(θ i )+sin(φ i )sin(θ i ))

[0021] Among them, φ bi (x, y) is the required phase distribution of the beam, k is the wave number, d is the distance from any point on the lens to the center, φ i represents the azimuth of the beam, θ i is the elevation angle of the beam.

[0022] Optionally, in step 4, the width of the dielectric unit is half the vacuum wavelength corresponding to 75 GHz, and the relationship between the unit height and the phase and amplitude is obtained by changing the height of the dielectric column.

[0023] Optionally, the phase compensation scheme of the beam vector superposition algorithm in step 5 includes the following steps:

[0024] Step 5.1: Obtain the focal plane field phase distribution corresponding to different pointing beams;

[0025] Step 5.2: Obtain multiple different beam deflection conditions and record their phases as φ bi ;

[0026] Step 5.3: Calculate the required compensation phase difference of the focal plane using the following formula:

[0027] f(θ,φ)=f e (θ,φ)exp(-jΔφ VSA (x,y)

[0028]

[0029] Step 5.4: Obtain the phase difference of different numbers of beams and arrange the dielectric columns in step 4 appropriately.

[0030] Optionally, the multi-beam test steps in step 6 are as follows:

[0031] Step 6.1: Place the dielectric lens antenna in the far field of the transmitting antenna;

[0032] Step 6.2: Keep the main polarization of transmission and reception consistent;

[0033] Step 6.3: The pitch angle theta of the transmitter is scanned within the range of -180° to 180°;

[0034] Step 6.4: Get the level values ​​at different angles;

[0035] Step 6.5: After completing steps 6.2 to 6.4, the azimuth angles of the transmitter and receiver are increased simultaneously, and the main polarization is kept consistent;

[0036] Step 6.6: Repeat steps 6.2 to 6.5 until the azimuth angle reaches 180°.

[0037] The present invention provides a beam vector superposition method for multi-beam antenna design. First, the directional pattern information of the feed antenna is obtained, and then the longitudinal distance of the lens focal plane from the feed, the number of plane grids and the unit width are preset. Then, the basic requirements of the multi-beam are obtained. According to the target requirements, the dielectric unit is designed and the S parameters and phase characteristics of the unit are evaluated. Finally, the phase distribution required for compensation of the lens is obtained through the phase compensation scheme of the beam vector superposition algorithm, and the dielectric unit is arranged reasonably. In addition, the feasibility and effectiveness of the method are verified by making a test prototype. It has been verified by simulation experiments that the present invention can realize the flexible control of the number of multi-beams and the free adjustment of the sub-beam pointing. Under the requirements of the number of beams and the sub-beam pointing, the gain of each sub-beam can be improved, the beam width can be narrowed, the sidelobe level can be reduced, and the deepest null can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 It is a schematic diagram of a method for determining a feed antenna and a focal plane in a beam vector superposition method for multi-beam antenna design of the present invention.

[0040] Figure 2 It is a schematic diagram of focal plane grid division and phase distribution according to a specific embodiment of the present invention.

[0041] Figure 3 It is a schematic diagram of the structure of a dielectric unit according to a specific embodiment of the present invention.

[0042] Figure 4 It is a schematic diagram of phase change and S parameter analysis of a dielectric unit in a specific embodiment of the present invention.

[0043] Figure 5 It is a schematic diagram of the corresponding relationship between phase change and beam deflection in a specific embodiment of the present invention.

[0044] Figure 6 It is a schematic diagram of multi-beam phase difference distribution in a specific embodiment of the present invention.

[0045] Figure 7 It is a schematic diagram of 5-beam pointing and lens (VSA-5) in a specific embodiment of the present invention.

[0046] Figure 8 It is a schematic diagram of the lens antenna test environment and the actual object in a specific embodiment of the present invention.

[0047] Fig. 9 It is a schematic diagram of the relationship between the gain and S11 curve of the lens antenna in a specific embodiment of the present invention.

[0048] Fig.10 It is a schematic diagram of actual measurement and simulation of the beam of the lens antenna in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0049] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0050] The present invention provides a beam vector superposition method for multi-beam antenna design, comprising the following steps:

[0051] Step 1: Obtain the directional pattern information of the feed antenna;

[0052] Step 2: Preset the longitudinal distance between the focal plane of the lens and the feed source, the number of plane grids, and the unit width;

[0053] Step 3: Obtain the basic requirements of multi-beam;

[0054] Step 4: Design the dielectric unit and evaluate the S parameters and phase characteristics of the unit according to the target requirements;

[0055] Step 5: Obtain the phase distribution required for lens compensation through the phase compensation scheme of the beam vector superposition algorithm, and arrange the dielectric units reasonably;

[0056] Step 6: Make a test prototype to verify feasibility and effectiveness.

[0057] See also Figures 1 to 10 , the following is further described in conjunction with specific embodiments and execution steps:

[0058] The acquisition of feed antenna pattern information in step 1 includes:

[0059] (1) Select a suitable electromagnetic wave working frequency band and establish a feed antenna model in electromagnetic simulation software. The present invention selects a horn antenna as a feed source, which works in the E band.

[0060] (2) Obtain the far-field radiation pattern information, S parameters, and electric field distribution characteristics of the feed antenna.

[0061] (3) The -10 dB beam widths of the E plane, H plane, and D plane are screened out through the far-field pattern information. The -10 dB beam width of the embodiment of the present invention is ±30°.

[0062] (4) Determine the focal plane size using the beam width and the preset focal plane distance. In the embodiment of the present invention, the focal length is selected to be 65 mm, and the focal plane size is 62 mm×62 mm. Figure 1 shown.

[0063] The number of plane grids and the unit width in step 2 are determined by:

[0064] (1) Based on step 1, the focal plane model needs to be meshed. Figure 2 As shown, the embodiment of the present invention divides the plane into 31×31 periods. It can be seen that the phase on the plane presents a periodic distribution.

[0065] (2) The unit width selected in the embodiment of the present invention is half the wavelength of the center frequency of the E band, because this method can effectively realize the ultra-wideband characteristics of the lens antenna.

[0066] (3) The phase difference at the focal plane at F is denoted by φ h (x,y). It can be calculated by formula (1):

[0067]

[0068] Center of plane (x 0 ,y 0 ) is set to 0°. As the unit U(x,y) moves away from the origin, φ h (x,y) shows periodic changes.

[0069] In step 3, the multi-beam pattern information is converted into a vector superposition form, which is further converted into focal plane electric field characteristics including:

[0070] (1) The multi-beam pattern information can be calculated using formula (2):

[0071] φ bi (x,y)=kd(cos(φ i )sin(θ i )+sin(φ i )sin(θ i )) (2)

[0072] In the formula, the phase distribution corresponding to the multi-beam pattern is φ bi (x, y), which contains the azimuth angle and elevation angle information of the directional pattern.

[0073] (2) Based on the feed phase distribution and the phase requirements of the multi-beam, the phase difference that needs to be compensated at the focal plane can be effectively calculated.

[0074] (3) This phase difference needs to be corrected using a lens to convert the spherical wave emitted by the feed source into a multi-beam field distribution to meet specific multi-beam requirements.

[0075] In step 4, the design of the dielectric unit includes:

[0076] (1) Figure 3 As shown in FIG. 1 , the structure of the dielectric unit proposed in the present invention is shown, where h is the height of the dielectric column, w is the width, and w is half the vacuum wavelength corresponding to 75 GHz.

[0077] (2) Adding matching layers at the top and bottom of the dielectric column can effectively improve the matching between the lens and the horn. Their height and radius are d and r respectively. By changing h, the relationship between the unit height and the phase and amplitude is obtained, as shown in Figure 4 shown.

[0078] (3) The unit in the embodiment of the present invention can achieve a phase coverage of 0-360°, and the transmission attenuation S21 is greater than 1 dB, which proves that this structure can change the phase while avoiding excessive dielectric loss.

[0079] (4) Before designing a multi-beam lens antenna, the design of the dielectric unit is crucial. Finally, the number of beams and the sub-beam pointing angle can be controlled through different phase compensation schemes.

[0080] In step 5, the phase compensation scheme of the beam vector superposition algorithm includes:

[0081] (1) Obtain the focal plane field phase distribution corresponding to different pointing beams to ensure that the phase change can effectively control the deflection and control of the beam, such as Figure 5 shown.

[0082] (2) In order to realize the free control of multiple sub-beams, it is also necessary to obtain multiple different beam deflection conditions and record their phases as φ bi The embodiment of the present invention is a four-beam and five-beam lens antenna, so the sub-beam phase distribution is recorded as φ b1 ,φ b2 ,φ b3 and φ b4 .

[0083] (3) Based on the feed phase distribution and multi-beam phase requirements, the required compensation phase difference of the focal plane can be calculated by formula (3) and formula (4):

[0084] f(θ,φ)=f e (θ,φ)exp(-jΔφ VSA (x,y)) (3)

[0085]

[0086] (4) Where Rad{*} indicates the radian value of *. When N=4, φ bi Substitute into (4) to obtain the phase difference Δφ of the four beams VSA-4 ,like Figure 6 (a) When N = 5, the phase difference Δφ of the 5 beams can also be obtained. VSA-5 ,like Figure 6 (b) as shown.

[0087] (5) Figure 7 The one shown is VSA-5.

[0088] The beam pointing (θ, φ) = (5°, 20°), (17°, 70°), (31°, 170°), (37°, 230°) and (41°, 310°). The angles of (θ, φ) are random angles used to verify the flexibility of VSA beam pointing. Figure 6 There is no regularity in the phase distribution in (b), but the lens antenna designed based on VSA can realize the control of any number of beams and sub-beam pointing.

[0089] In step 6, a test prototype is made to verify the feasibility and effectiveness of the method, including:

[0090] (1) Figure 8 As shown in (a), the lens antenna is divided into four parts: lens, connecting column, base and feed. The lens, connecting column and base are integrated into a single piece through the photocuring technology in 3D printing technology. They use the same dielectric material RGD837 (er = 2.9, tan = 0.01). The lens is fed by a linearly polarized horn antenna (LB-12-15-AwithWR12). Figure 8 As shown in (b), the lens antenna is placed in a microwave test environment. The multi-beam test steps are as follows:

[0091] Step 1: Place the dielectric lens antenna in the far field of the transmitting antenna.

[0092] Step 2: Keep the main polarization of transmission and reception consistent.

[0093] Step 3: The pitch angle theta of the transmitter is scanned within the range of -180° to 180°.

[0094] Step 4: Get the level values ​​at different angles.

[0095] Step 5: After completing Step 2-Step 4, the azimuth angles of the transmitter and receiver are increased simultaneously, while keeping the main polarization consistent.

[0096] Step6: Repeat Step2-Step5 until the azimuth angle reaches 180°.

[0097] (2) Fig. 9 As shown in the figure, at 60-90GHz, the matching curve S11 of the VSA-5-Diff lens antenna is lower than -12.5dB. The dielectric lens and the feed horn have good matching performance. The gain of the lens antenna is the maximum gain in different sub-beams at each frequency point. The maximum difference between the measured gain and the simulated gain drop in the full frequency band is 0.76dB, and the lens antenna obtains a measured peak gain of 23.8dBi at 88GHz.

[0098] (3) Fig.10 As shown in Figure 1, at 75 GHz, the multi-beam measurement and simulation results of the lens antenna are obtained. Fig.10 In (a), the number and orientation of the sub-beams are clearly visible with few low-level sidelobes. The energy distribution of the sub-beams is relatively uniform and all show good radiation characteristics. The beams of theta = 37° and theta = 41° are well improved and the energy is distributed relatively evenly. It is proven that the phase utilization of the lens focal plane is improved with increasing frequency. Fig.10 In (b)-(f), the maximum beam pointing of the measured and simulated images is relatively consistent, and the sidelobe level is low. Specifically, (b)-(f) are the simulation and measured comparison diagrams of the sub-beams at (b) theta = 5°, (c) theta = 17°, (d) theta = 31°, (e) theta = 37°, and (f) theta = 41°. Fig.10 In (f), when theta = 41°, phi = 310°, the sub-beam has the lowest sidelobe level of -13dB. For large-angle beam deflection, the measured results of the lens antenna still maintain good consistency.

[0099] In summary, compared with the prior art, the present invention has the following beneficial effects:

[0100] 1. A multi-beam all-dielectric lens antenna is designed, which can realize flexible control of the number of multi-beams and free adjustment of the sub-beam pointing.

[0101] 2. Under the premise of meeting the requirements of the number of beams and sub-beam pointing, the gain of each sub-beam can be increased, the beam width can be narrowed, the sidelobe level can be lowered, and the deepest null can be achieved.

[0102] A low-cost, easy-to-make, lightweight multi-beam antenna solution is proposed, which can easily realize single-beam to multi-beam conversion.

[0103] What is disclosed above is only one or more preferred embodiments of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of implementing the above embodiments and making equivalent changes according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A beam vector superposition method for multi-beam antenna design, characterized in that: The following steps are involved: Step 1: Obtain the directional pattern information of the feed antenna; Step 2: Preset the longitudinal distance between the focal plane of the lens and the feed source, the number of plane grids, and the unit width; Step 3: Obtain the basic requirements of multi-beam; Step 4: Design the dielectric unit and evaluate the S parameters and phase characteristics of the unit according to the target requirements; Step 5: Obtain the phase distribution required for lens compensation through the phase compensation scheme of the beam vector superposition algorithm, and arrange the dielectric units reasonably; Step 6: Make a test prototype to verify feasibility and effectiveness.

2. The beam vector superposition method for multi-beam antenna design according to claim 1, characterized in that: In step 1, a horn antenna is selected as the feed antenna, which operates in the E band, and the -10 dB beam width of the E, H, and D planes is screened out through the far-field radiation pattern information of the feed antenna.

3. The beam vector superposition method for multi-beam antenna design according to claim 2, characterized in that: The phase difference at the focal plane in step 2 is denoted by φ h (x,y), the expression is as follows: The phase of the plane center (x0, y0) is set to 0°. As the unit U(x, y) moves away from the origin, φ h (x,y) shows periodic changes.

4. The beam vector superposition method for multi-beam antenna design according to claim 3, characterized in that: The phase distribution corresponding to the multi-beam pattern in step 3 is φ bi The calculation formula for (x,y) is as follows: f bi (x,y)=kd(cos(φ i )sin(θ i )+sin(φ i )sin(θ i )) Among them, φ bi (x, y) is the required phase distribution of the beam, k is the wave number, d is the distance from any point on the lens to the center, φ i represents the azimuth of the beam, θ i is the elevation angle of the beam.

5. The beam vector superposition method for multi-beam antenna design according to claim 4, characterized in that: In step 4, the width of the dielectric unit is half the vacuum wavelength corresponding to 75 GHz, and the relationship between the unit height and the phase and amplitude is obtained by changing the height of the dielectric column.

6. The beam vector superposition method for multi-beam antenna design according to claim 5, characterized in that: The phase compensation scheme of the beam vector superposition algorithm in step 5 includes the following steps: Step 5.1: Obtain the focal plane field phase distribution corresponding to different pointing beams; Step 5.2: Obtain multiple different beam deflection conditions and record their phases as φ bi ; Step 5.3: Calculate the required compensation phase difference of the focal plane using the following formula: f(θ,φ)=f e (θ,φ)exp(-jΔφ VSA (x,y)) Step 5.4: Obtain the phase difference of different numbers of beams and arrange the dielectric columns in step 4 appropriately.

7. The beam vector superposition method for multi-beam antenna design according to claim 6, characterized in that: The multi-beam test steps in step 6 are as follows: Step 6.1: Place the dielectric lens antenna in the far field of the transmitting antenna; Step 6.2: Keep the main polarization of transmission and reception consistent; Step 6.3: The pitch angle theta of the transmitter is scanned within the range of -180° to 180°; Step 6.4: Get the level values ​​at different angles; Step 6.5: After completing steps 6.2 to 6.4, the azimuth angles of the transmitter and receiver are increased simultaneously, and the main polarization is kept consistent; Step 6.6: Repeat steps 6.2 to 6.5 until the azimuth angle reaches 180°.

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