A two-dimensional phased array antenna

Abstract

This invention discloses a two-dimensional phased array antenna, comprising a plurality of antenna elements, wherein the antenna elements are low-profile traveling-wave medium antenna elements, and the plurality of low-profile traveling-wave medium antenna elements are arrayed in an M-row N-column configuration, where 3≤M≤5 and 3≤N≤5; the array spacing is 0.5~0.8λ, where λ is the wavelength of the electromagnetic wave at the operating frequency of the low-profile end-fire antenna element. The array antenna of this invention solves the problems of high-gain antenna array densification and small aperture, resulting in a compact antenna structure with a small lateral area. For the same aperture, the two-dimensional array antenna of this invention has higher radiation gain than traditional array antennas, i.e., higher aperture efficiency. The two-dimensional phased array antenna of this invention can achieve high-gain two-dimensional ±20° beam scanning, and is suitable for platforms requiring miniaturized, high-gain antennas, such as aircraft side-mounted antennas or mobile communication base stations.

Description

[Technical Field]

[0001] This invention relates to microwave antennas, and more particularly to a two-dimensional phased array antenna. [Background Technology]

[0002] Massive MIMO technology has been widely applied with the development of 5G, and it will play a crucial role in future 6G communication systems. Typically, the antenna array at the antenna end of a 5G / 6G base station has at least 64 elements. Such a large number of antenna elements, if not arranged compactly, would result in an excessively large overall size of the antenna array, significantly increasing the cost of base station site selection and installation. However, reducing the spacing between antenna elements would significantly degrade the isolation between ports within the array, thus affecting the overall system capacity of the wireless communication system. This clearly contradicts the original intention of developing 5G / 6G. Therefore, how to reduce the spacing between antenna elements while maintaining port isolation and high array gain is of practical research significance.

[0003] Today, 5G is making rapid progress in commercialization, leading to an increasing demand for large-scale MIMO antenna arrays. Domestically and internationally, the antenna elements chosen for arraying are generally simple microstrip antennas or planar dipole antennas, both of which have an aperture of approximately half a wavelength in diameter. To achieve the three-dimensional beamforming, spatial diversity, and spatial multiplexing characteristics of 5G, these two types of antennas are arrayed together.

[0004] However, to achieve the high speed, low latency, energy efficiency, high capacity, and high reliability of 5G and future 6G communication networks, a large-scale deployment of MIMO antenna arrays is required. Furthermore, 5G antenna elements integrate radiating elements with remote radio units (RRUs) to form active antenna units (AAUs), significantly increasing weight compared to radiating elements alone. This places a heavy burden on base stations with limited space and load-bearing capacity. Existing high-gain antennas are typically large-scale arrays or high-aperture-efficiency arrays. For large-scale arrays, the element spacing is typically 0.7 times the wavelength of the electromagnetic wave at the operating frequency. To achieve high-gain radiation, the array size would need to reach hundreds or thousands of elements, occupying a huge lateral area, making it difficult to apply to platforms with limited space. On the other hand, the gain of the array antenna can be increased without increasing the lateral area by increasing the antenna's aperture efficiency. Existing high-aperture-efficiency antennas typically use artificial metamaterials, lenses, etc., to increase aperture efficiency, but their aperture efficiency is still less than 100%. In addition, large-aperture antenna arrays also have disadvantages such as difficult assembly, poor environmental robustness, and unattractive aesthetics. [Summary of the Invention]

[0005] The technical problem to be solved by the present invention is to provide a two-dimensional phased array antenna with high aperture efficiency.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is a two-dimensional phased array antenna, comprising a plurality of antenna elements, wherein the antenna elements are low-profile traveling wave medium antenna elements, and the plurality of low-profile traveling wave medium antenna elements are arrayed in an M-row N-column manner, where 3≤M≤5 and 3≤N≤5; the array spacing is 0.5~0.8λ, where λ is the wavelength of the electromagnetic wave at the operating frequency of the low-profile end-fire antenna element.

[0007] The two-dimensional phased array antenna described above, with its low-profile traveling-wave dielectric antenna element, includes a long, high-dielectric-constant dielectric substrate, a metal ground plane, an element, and a coaxial connector. The metal ground plane is fixed to the bottom surface of the dielectric substrate, and the element is printed on the top surface of the dielectric substrate, near the rear end of the antenna element along the long axis of the dielectric substrate. The front end of the antenna element along the long axis of the dielectric substrate serves as the transmitting and receiving end. The element includes a plurality of impedance matching bars and a ring-shaped metal element. The plurality of impedance matching bars are arranged at the rearmost end of the antenna element along the long axis of the dielectric substrate, and the ring-shaped metal element is arranged in front of the impedance matching bars. The coaxial connector is arranged below the ring-shaped metal element, with its outer shell connected to the metal ground and its inner core passing through the dielectric substrate and connected to the ring-shaped metal element. The impedance matching bars are connected to the metal ground plane through metal vias in the dielectric substrate.

[0008] The dielectric constant ε of the dielectric substrate in the two-dimensional phased array antenna described above is... r The value is 10 to 10.4; the height of the dielectric substrate H = 0.07 to 0.09λ, the length L = 2 to 2.4λ, and the width W < 0.3λ; the length of the metal floor is equal to the length of the dielectric substrate, and the width is less than 0.5λ.

[0009] The two-dimensional phased array antenna described above has 6 to 10 impedance matching bars, which are arranged separately along the long axis of the dielectric substrate. The length direction of the impedance matching bars is orthogonal to the long axis of the dielectric substrate, and the length of the impedance matching bars is the same as the width of the dielectric substrate. The ring metal vibrator is flat and elongated, and its long axis is orthogonal to the long axis of the dielectric substrate. The length of the ring metal vibrator is the same as the width of the dielectric substrate, and the distance from the feed end of the ring metal vibrator to the rear end of the dielectric substrate is 0.23 to 0.27λ.

[0010] The two-dimensional phased array antenna described above, L = 2.1 ~ 2.3λ.

[0011] The two-dimensional phased array antenna described above has M=3 and N=3; the dielectric constant ε of the dielectric substrate is... r The value is 10.2, the array spacing is 0.5λ; the height of the dielectric substrate is... Length L = 2.34λ; the coaxial cable connector is a 50Ω coaxial cable connector.

[0012] The two-dimensional phased array antenna of the present invention solves the problems of high-gain antenna array densification and small aperture. The antenna structure is compact and occupies a small lateral area. Under the same aperture, the two-dimensional array antenna of the present invention has higher radiation gain than the traditional array antenna, that is, higher aperture efficiency. [Image Description]

[0013] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0014] Figure 1 This is a perspective view of the antenna element of the low-profile traveling wave medium according to an embodiment of the present invention.

[0015] Figure 2 This is a front view of the antenna element of the low-profile traveling wave medium in an embodiment of the present invention.

[0016] Figure 3 This is a top view of the antenna element of the low-profile traveling wave medium according to an embodiment of the present invention.

[0017] Figure 4 This is an exploded view of the antenna element of the low-profile traveling wave medium according to an embodiment of the present invention.

[0018] Figure 5 This is a three-dimensional view of a two-dimensional phased array antenna according to an embodiment of the present invention.

[0019] Figure 6 This is a top view of the two-dimensional phased array antenna according to an embodiment of the present invention.

[0020] Figure 7 This is a return loss diagram of a two-dimensional phased array antenna under different dielectric substrate lengths L according to an embodiment of the present invention.

[0021] Figure 8 This is a trend graph showing the gain of the two-dimensional phased array antenna as a function of the dielectric substrate length L, according to an embodiment of the present invention.

[0022] Figure 9 This is a simulation diagram of the two-dimensional phased array antenna scanning in the azimuth plane according to an embodiment of the present invention.

[0023] Figure 10 This is a simulation diagram of the two-dimensional phased array antenna scanning in the elevation plane according to an embodiment of the present invention. [Detailed Implementation]

[0024] The structure of the antenna element of the low-profile traveling-wave medium in the embodiments of the present invention is as follows: Figures 1 to 4 As shown, it includes a long, high dielectric constant dielectric substrate 1, a metal ground plate 2, an oscillator, and a coaxial connector 6.

[0025] The dielectric substrate 1 is made of Rogers RO3210 with a dielectric constant of 10.2. Its dimensions are L = 117 mm, W = 15 mm, and H = 4 mm. The height of dielectric substrate 1 is... The length L ≈ 2.3λ, and the width W < 0.3λ.

[0026] Metal floor 2 is fixed to the bottom surface of medium board 1. The material of metal floor 2 is aluminum. The length is 117mm, which is equal to L; the width is 24mm, which is less than 0.5λ; and the height is 1mm.

[0027] The oscillator comprises eight impedance matching bars 4 and a ring metal oscillator 5. The impedance matching bars 4 and the ring metal oscillator 5 are printed on the top surface of the dielectric substrate 1, near the rear end of the antenna element along the long axis of the dielectric substrate. The front end of the antenna element along the long axis of the dielectric substrate is the transmitting and receiving end. The eight impedance matching bars 4 are arranged at the rearmost end of the antenna element along the long axis of the dielectric substrate, and the ring metal oscillator 5 is arranged in front of the impedance matching bars 4.

[0028] The impedance matching strip 4 is 15mm long and 1.85mm wide, and is arranged separately along the long axis of the dielectric substrate 1. The length direction of the impedance matching strip 4 is orthogonal to the long axis of the dielectric substrate 1, and the spacing between adjacent impedance matching strips 4 is 2mm (the gap between them is 0.15mm). Each impedance matching strip 4 is connected to the metal ground plane 2 through two metallized through holes 3 in the dielectric substrate 1. The diameter of the metallized through holes 3 is 1mm, and the center distance between the two metallized through holes 3 and the impedance matching strip 4 is 6mm.

[0029] The annular metal oscillator 5 is elongated and flat, with its major axis orthogonal to the major axis of the dielectric substrate 1. The length of the annular metal oscillator 5 is the same as the width of the dielectric substrate 1, which is 15 mm, and its width is 2 mm. The distance from the feed terminal 5-1 of the annular metal oscillator 5 to the rear end of the dielectric substrate 1 is approximately 0.25λ.

[0030] A 50Ω coaxial connector 6 is arranged below the annular metal oscillator 5. The outer shell of the 50Ω coaxial connector 6 is connected to the metal ground plate 2, and the inner core passes through the dielectric plate 1 and is connected to the annular metal oscillator 5.

[0031] The height H of dielectric substrate 1 defines the surface wave propagation mode of electromagnetic waves, and its length L determines the radiation gain of the antenna. The length of the ring dipole, its distance from the rear end of dielectric substrate 1, and its height from the metal ground plate 2 determine the operating frequency of the antenna.

[0032] The structure of the two-dimensional phased array antenna in this embodiment of the invention is as follows: Figure 5 and Figure 6As shown, the antenna includes nine low-profile traveling-wave dielectric antenna elements, which are arrayed in the XY plane in an M-row, N-column configuration, where M=3 and N=3; the dielectric constant ε of the dielectric substrate is... r The value is 10.2, the array spacing is 0.5λ, and λ is the wavelength of the electromagnetic wave at the operating frequency of the low-profile end-fire antenna element. For example... Figure 6 As shown, the distance Du between the array unit and the adjacent unit is 25mm, which is half the electromagnetic wave wavelength λ when the array is operating at a frequency of 6GHz.

[0033] Generally, a traveling-wave end-fire antenna consists of a feed structure and a waveguide structure. The feed structure couples the energy of the input signal to the waveguide structure, where it propagates as a surface wave on the surface of the waveguide structure. When the electromagnetic wave propagates to a discontinuous structure, it generates electromagnetic radiation. Traditional surface wave antennas typically use horn feeding or similar feeding methods. The printed dipole and periodic matching structure feeding in the above embodiments of this invention achieve a low profile height while improving impedance matching between the feed structure and the dielectric substrate 1. The surface wave guide structure uses a regular cuboid dielectric substrate 1 structure, and through the aforementioned dimensional structure, high-gain end-fire radiation can be obtained. The main body of the antenna in this invention is a high-dielectric-constant dielectric substrate 1. Electromagnetic waves propagate in this medium as surface waves and radiate into free space at the terminal, which is the traveling-wave dielectric end-fire method. This invention adopts the traveling-wave dielectric end-fire method, innovatively combining the length component with the traditional aperture principle of antennas, proposing a three-dimensional aperture principle. While ensuring that the antenna aperture area does not increase, the antenna gain is improved by increasing the antenna length, achieving a low-profile, small-aperture, high-gain antenna element.

[0034] This invention provides a traveling-wave end-fire antenna element operating at 6 GHz, consisting of a printed dipole and a periodic impedance matching structure. This achieves a lower profile height and improves impedance matching between the feed structure and the dielectric substrate 1. The surface waveguide structure uses a regular rectangular dielectric substrate 1 structure. Through the aforementioned dimensional structure, high-gain end-fire radiation can be obtained. The antenna structure is as follows: Figure 1 As shown. To form surface waves in the dielectric substrate, the height of dielectric substrate 1 needs to satisfy the following formula:

[0035]

[0036] Where λ is the wavelength of the electromagnetic wave at the antenna's operating frequency, and ε r Let H be the dielectric constant of dielectric substrate 1. It can be seen that the higher the dielectric constant of the dielectric substrate, the lower its height. To achieve the low-profile characteristics of the antenna element, a dielectric constant of 10.2 is chosen here. To obtain the optimal antenna gain, the height H is ultimately optimized as follows:

[0037]

[0038] At an operating frequency of 6 GHz, the calculated antenna height H is 4 mm.

[0039] The width of the dielectric substrate has a relatively small impact on antenna performance, and was ultimately optimized to 15mm through software simulation and parameter scanning. Typically, the gain of a surface wave antenna is proportional to its length, i.e., the length of the dielectric substrate, as expressed by the formula:

[0040]

[0041] Where L is the length of the antenna dielectric substrate. This means that increasing the length of dielectric substrate 1 can improve the antenna gain. However, due to the influence of dielectric loss, increasing the length of dielectric substrate 1 will increase dielectric loss and reduce radiation efficiency. At the same time, an excessively long length is not conducive to the miniaturization design of the antenna. Therefore, the length of dielectric substrate 1 should be determined by comprehensively considering the requirements of electrical performance and the installation space of the antenna. The possible value range of L is λ to 2.5λ.

[0042] To achieve low-profile characteristics and impedance matching for the antenna element, this embodiment of the invention designs a ring-shaped printed oscillator and a periodic impedance matching structure. The ring-shaped oscillator 5 has a length of 0.3λ. By etching a flat, elongated rectangular hole in the middle of the printed oscillator, the distance from the feed point through which the current flows to the end point of the oscillator is increased, thereby increasing the equivalent length of the oscillator and enabling the antenna with a lower profile to operate at a lower frequency. Furthermore, a waveguide-like structure is formed by periodically loading metallized vias 3 and impedance matching strips 4, increasing the input impedance of the antenna and allowing the low-profile printed ring-shaped metal oscillator 5 with low radiation impedance to be impedance matched with a 50Ω coaxial connector. Simultaneously, the distance between the feed point of the printed ring-shaped metal oscillator 5 and the rear end of the dielectric substrate 1 is approximately 0.25λ, minimizing the input reactance introduced by the periodic structure. To facilitate antenna arraying, the width of the metal ground plane should be less than 0.5 times the wavelength of the electromagnetic wave at the antenna's operating frequency. In this embodiment, the width of the metal ground plane 2 is 24mm.

[0043] The antenna element is fed by an SMA coaxial connector. The electromagnetic wave is converted into a traveling wave in the dielectric substrate 1 through a printed ring metal oscillator 5. Impedance matching is performed by periodic metal vias 3 and impedance matching strips 4. After being fed in, the electromagnetic wave is converted into a traveling wave in the high dielectric constant dielectric substrate and finally enters free space along the Z-axis at the end of the dielectric substrate 1 and radiates. Figure 7 The graph shows the return loss results of this antenna under different dielectric substrate lengths L. Figure 7 As can be seen, the antenna gain is 9.5 dBi. Figure 8 This demonstrates the trend of the antenna's gain as a function of the substrate length L. From... Figure 8As can be seen, the antenna gain increases with the increase in antenna length, but the rate of increase decreases. Therefore, considering both the need for high antenna gain and the need to minimize antenna size, the final antenna element length (length of dielectric substrate 1) was determined to be 2.34λ.

[0044] The antenna elements with the above structure are arrayed. To facilitate understanding of the ultra-high aperture efficiency of the two-dimensional array composed of the surface wave focusing antennas of this invention, a 3×3 two-dimensional array is used for description. The following formula is the directivity calculation formula for the antenna:

[0045]

[0046] Where θ and These are the elevation and azimuth angles of the antenna radiation, respectively. and These are the array factor and the element factor, respectively. The array factor is related to the number of array elements and the array arrangement, i.e.:

[0047]

[0048] Where M and N are the number of columns and rows of the array, respectively. To achieve an aperture efficiency exceeding 100%, both M and N should not exceed 5, meaning the maximum array size should not exceed 5×5. k is the wave vector of the electromagnetic wave in free space, and Du is the cell spacing between the columns and rows of the array. θ0 and These represent the elevation and azimuth angles of the beam. j is an imaginary number. This can be obtained from the software simulation results. In this embodiment, as... Figure 6 As shown, M = N = 3.

[0049] Furthermore, according to the traditional antenna aperture principle, the directivity D of an antenna is related to the physical aperture area A. p The relationship between them is:

[0050]

[0051] In formula (3), λ is the wavelength of the electromagnetic wave at the working frequency in a vacuum, and η ap This refers to the aperture efficiency of the antenna; different antennas have different aperture efficiencies. Let η be the aperture efficiency. ap Using 100% as the standard, the maximum directivity achievable by a traditional antenna can be calculated. By... and Substituting the directional calculation formula, i.e. formula (1), the actual gain of the array composed of the low-profile traveling wave dielectric antenna elements used in the embodiments of the present invention can be calculated.

[0052] The formula for calculating antenna aperture efficiency is as follows:

[0053]

[0054] Where D is the directional coefficient of the two-dimensional phased array.

[0055] Figure 9 and Figure 10 Simulation results of beam scanning for a 3×3 small-aperture, high-gain two-dimensional phased array according to embodiment 3 of the present invention are presented. The aperture efficiency of this example array can be calculated to be approximately 130% using formula (4). Figure 9 and Figure 10 As can be seen, due to the symmetry of the antenna structure in the azimuth plane, the scanning patterns of the antenna array at positive and negative azimuth angles are symmetrical. When the antenna array scans to 20° in the azimuth plane, the scanning gain decreases by 1.27 dB. When the antenna array scans to 20° in the elevation plane, the scanning gain decreases by 2.48 dB, and when it scans to -20° in the elevation plane, the scanning gain decreases by 1.87 dB. It can be seen that the end-fire array not only has the characteristic of high gain but also can achieve beam scanning in both the azimuth and elevation planes.

[0056] The two-dimensional phased array antenna of the present invention, as described above, groups antenna elements with an array spacing of 0.5 times the wavelength of the electromagnetic wave at the operating frequency. This solves the problems of high-gain antenna array densification and small aperture, resulting in a compact antenna structure with a small lateral area. The smaller the array spacing of the two-dimensional phased array antenna, the larger the array scanning angle and the higher the array aperture efficiency, achieving an array aperture efficiency exceeding 100%. At the same aperture, the two-dimensional array antenna of the present invention has higher radiation gain than traditional array antennas, i.e., higher aperture efficiency. The two-dimensional phased array antenna of the present invention, as described above, can achieve high-gain two-dimensional ±20° beam scanning, making it suitable for platforms requiring miniaturized, high-gain antennas, such as aircraft side panels or mobile communication base stations.

Claims

1. A two-dimensional phased array antenna comprising a plurality of antenna elements, characterized in that, The antenna element is a low-profile traveling wave medium antenna element. A plurality of low-profile traveling wave medium antenna elements are arrayed in an M-row N-column configuration, where 3≤M≤5 and 3≤N≤5. The array spacing is 0.5~0.8λ, where λ is the wavelength of the electromagnetic wave at the operating frequency of the low-profile end-fire antenna element. The antenna element of the low-profile traveling-wave dielectric includes a long, high-dielectric-constant dielectric substrate, a metal ground plane, an element, and a coaxial connector. The metal ground plane is fixed to the bottom surface of the dielectric substrate, and the element is printed on the top surface of the dielectric substrate, near the rear end of the antenna element along the long axis of the dielectric substrate. The front end of the antenna element along the long axis of the dielectric substrate is the transmitting and receiving end. The element includes a plurality of impedance matching bars and a ring-shaped metal element. The plurality of impedance matching bars are arranged at the rearmost end of the antenna element along the long axis of the dielectric substrate, and the ring-shaped metal element is arranged in front of the impedance matching bars. The coaxial connector is arranged below the ring-shaped metal element, with its outer shell connected to the metal ground and its inner core passing through the dielectric substrate and connected to the ring-shaped metal element. The impedance matching bars are connected to the metal ground plane through metal vias in the dielectric substrate.

2. The two-dimensional phased array antenna of claim 1, wherein, The dielectric constant ε of the dielectric plate r is 10-10.4; the height H of the dielectric plate is 0.07-0.09λ, the length L is 2-2.4λ, and the width W is <0.3λ; the length of the metallic ground plane is equal to the length of the dielectric plate, and the width is <0.5λ.

3. The two-dimensional phased array antenna of claim 1, wherein, The number of impedance matching strips is 6 to 10, arranged separately along the long axis of the dielectric substrate; the length direction of the impedance matching strip is orthogonal to the long axis of the dielectric substrate, and the length of the impedance matching strip is the same as the width of the dielectric substrate; the ring metal oscillator is flat and elongated, and its long axis is orthogonal to the long axis of the dielectric substrate; the length of the ring metal oscillator is the same as the width of the dielectric substrate, and the distance from the feed end of the ring metal oscillator to the rear end of the dielectric substrate is 0.23 to 0.27λ.

4. The two-dimensional phased array antenna according to claim 2, characterized in that, L = 2.1 - 2.3 λ.

5. The two-dimensional phased array antenna according to claim 2, characterized in that, M = 3, N = 3; dielectric constant of the dielectric plate ε r 10.2, inter-element spacing 0.5λ; height of the dielectric plate h 2.34λ; coaxial connectors are 50Ω coaxial connectors.

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