Dual-polarization meter-wave array antenna unit and antenna array

Abstract

The invention provides a dual-polarization meter-wave array antenna unit, the antenna unit comprises a metal outer frame and two sub-antenna units with the same size, the metal outer frame and the two sub-antenna units are square, the inner side length of the metal outer frame is twice that of the sub-antenna units, and the inner side length of the metal outer frame is larger than that of the sub-antenna units. The two sub-antenna units are respectively located at the left upper part and the right lower part in the metal outer frame; wherein each sub-antenna unit comprises a square metal wall, a square upper-layer microstrip patch and a square lower-layer microstrip patch; the metal wall is flush with the upper-layer microstrip patch in height, the lower-layer microstrip patch is arranged at the orthographic projection position of the lower portion of the upper-layer microstrip patch in parallel and is arranged in the middle of an area defined by the metal wall, and the included angle between the edge of the upper-layer microstrip patch and the edge of the metal wall and the included angle between the edge of the lower-layer microstrip patch and the edge of the metal wall are 45 degrees. And the lower-layer microstrip patch is loaded by adopting a high-dielectric-constant medium, so that the miniaturization of the antenna is realized. The antenna unit and the carrying platform are designed in an integrated conformal mode, the beam scanning coverage range is increased, and the measurement data rate is increased through dual polarization.

Description

Technical Field

[0001] The present invention relates to the technical field of antennas for wireless communications, and in particular to a dual-polarized meter-wave array antenna unit and an antenna array. Background Art

[0002] Phased array radar is a radar technology based on the Huygens principle. It forms a main beam with different phases by arranging a large number of small antenna elements into an antenna array. Corresponding phase changes can be made in two axes. The electromagnetic waves emitted by each phase shifter of the phased array are enhanced and synthesized into a nearly vertical radar main lobe based on the principle of constructive interference. The side lobes are greatly reduced under destructive interference.

[0003] However, phased array antennas cannot achieve beam coverage of a large range of airspace with the help of servo systems like traditional mechanical scanning antennas. Therefore, expanding the beam scanning range of phased arrays is a hot research issue in this field. The difficulty lies in the fact that the scanning angle of phased array antennas is limited. Traditional planar phased array antennas can usually only maintain good performance within a beam scanning range of ±45°. From the theoretical knowledge of array antennas, we can know that the factors that restrict the scanning angle of phased array antennas are mainly array elements. The directional pattern of array antennas can be obtained by multiplying the unit directional pattern factor and the array factor. The units used in actual phased array antennas are not ideal isotropic radiation sources. The beam width of the array element is limited. When the gain of the array element antenna in a given direction is significantly lower than the maximum value, the gain of the phased array antenna will also be significantly attenuated accordingly. On the other hand, the input impedance of the antenna port is not constant. As the scanning angle increases, the mutual coupling between the array elements becomes stronger, which will affect the input impedance of the antenna port to a certain extent, making the impedance matching effect worse, and also causing the performance of the phased array antenna to deteriorate at large scanning angles.

[0004] In addition, polarization is an important wireless resource. Making full use of polarization resources is conducive to improving the transmission rate and channel capacity of the system, reducing the fading caused by multipath effects, and significantly improving system performance. Within the limited antenna unit size, how to achieve more polarizations and how to choose the polarization method are also factors that need to be considered.

[0005] In addition, the phased array antenna is also limited by the size and shape of the platform, which puts forward requirements for the conformal design capability of the phased array antenna and the platform. At present, the development trend of antenna platforms is miniaturization, modularization, and universalization, which also puts forward higher requirements for the size of the antenna. A common structure of a phased array radar antenna platform is as follows: Figure 1As shown, how to make the antenna unit perform optimally under this platform is also a problem to be solved by the present invention. At the same time, the relative bandwidth of the phased radar, also known as the percentage bandwidth, refers to the ratio of the width of the system's operating frequency range to its center frequency. This indicator can provide a measure of the frequency variation that the system or component can handle, so it is necessary to ensure that the designed antenna has a large relative bandwidth. Summary of the invention

[0006] In view of the problems that the scanning beam scanning range of the phased array radar antenna is small and the antenna size is large, the present invention proposes a dual-polarized meter-wave array antenna unit and an antenna array, which effectively solve the above problems.

[0007] In a first aspect of the present invention, a dual-polarized meter-wave array antenna unit is provided, the antenna unit comprising a metal outer frame 101, two sub-antenna units 102 of equal size, the metal outer frame 101 and the two sub-antenna units 102 are both square, the inner side length of the metal outer frame 101 is twice that of the sub-antenna unit 102, and the two sub-antenna units 102 are respectively located in the upper left and lower right parts of the metal outer frame 101;

[0008] Among them, each sub-antenna unit includes a square metal wall 111, a square upper microstrip patch 112 and a square lower microstrip patch 113. The height of the metal wall 111 is flush with the upper microstrip patch 112. The lower microstrip patch 113 is arranged in parallel at the lower positive projection position of the upper microstrip patch 112 and is centered in the area surrounded by the metal wall 111. The edges of the upper microstrip patch 112 and the lower microstrip patch 113 form an angle of 45° with the edge of the metal wall 111.

[0009] Preferably, each sub-antenna unit 102 is provided with two ports, and the polarization mode of the sub-antenna unit 102 is controlled by controlling the phase of the input signal of the port.

[0010] Preferably, when the phases of the two ports are both 0°, the antenna unit operates in a horizontal polarization mode.

[0011] Preferably, when the phase of one port is 0° and the phase of the other port is 180°, the antenna unit operates in a vertical polarization mode.

[0012] A second aspect of the present invention provides an antenna array, which is composed of a plurality of the above-mentioned dual-polarized meter-wave array antenna units.

[0013] Preferably, the antenna array is a 3x3 array.

[0014] Based on the integrated design of the structure of the metric-wave phased array antenna, the present invention proposes the use of antenna unit design technology to ensure that the half-power beam width of the antenna unit pattern is greater than the required scanning beam coverage of the phased array sub-array antenna, and the antenna scanning angle is increased from the original 90° to 120°; through the reasonable layout of the distributed phased array antenna system, the flexibility of the antenna array is improved, and the beam airspace coverage problem that cannot be achieved by a single phased array antenna is solved. Miniaturization, integration, conformal with the platform, increased beam scanning coverage, and dual polarization to improve the measurement data rate are achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 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 are briefly introduced below.

[0016] Figure 1 It is a structural schematic diagram of the phased radar antenna platform;

[0017] Figure 2 The simulation results of the directivity pattern of array 1 at the operating frequency f0+30MHz and the scanning angle 60°;

[0018] Figure 3 This is a schematic diagram of the structure of the second array proposed by the present invention;

[0019] Figure 4 The simulation results of the directivity pattern of array 2 at the operating frequency f0+30MHz and the scanning angle 60°;

[0020] Figure 5 This is a schematic diagram of the third structure of the array proposed by the present invention;

[0021] Figure 6 The simulation results of the directivity pattern of array 3 at the operating frequency f0+30MHz and the scanning angle 60°;

[0022] Figure 7 A three-dimensional schematic diagram of the placement of dual-polarized microstrip antennas in the array's three structures;

[0023] Figure 8 The schematic diagram of the three-dimensional structure of the miniaturized dual-polarized microstrip antenna in the array three structures;

[0024] Fig. 9 The simulation results of the standing wave ratio of the miniaturized dual-polarized microstrip antenna in the array three structures are shown;

[0025] Fig.10 This is a schematic diagram of the dual-polarized meter-wave array antenna unit structure proposed by the present invention;

[0026] Fig.11 A schematic diagram of the three-dimensional structure of the sub-antenna unit proposed in the present invention;

[0027] Fig.12 Schematic diagram of two polarization working modes of the antenna array proposed in the present invention;

[0028] Fig.13 This is a schematic diagram of the horizontal polarization synthesis principle of the sub-antenna unit proposed in the present invention;

[0029] Fig.14 This is a schematic diagram of the vertical polarization synthesis principle of the sub-antenna unit proposed in the present invention;

[0030] Fig.15 A schematic structural diagram of an antenna array according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments. Through the description of the embodiments, those skilled in the art can understand the advantages of the present invention in various aspects.

[0032] The design indicators of the dual-polarized meter-wave array antenna designed by the present invention are:

[0033] 1. Antenna unit:

[0034] 1) Operating frequency: f0-30MHz~f0+30MHz;

[0035] 2) Standing wave ratio: ≤2;

[0036] 2. Antenna array:

[0037] 1) Array gain: ≥20dBi;

[0038] 2) Sidelobe level: ≥5dB;

[0039] 3) Scanning angle: horizontal ±60°;

[0040] First, the design concept of the array structure of the present invention is introduced.

[0041] consider Figure 1 The antenna platform structure, if the array unit is a general broadband microstrip antenna, the calculation result does not consider the coupling between units and the antenna size problem, which is an ideal result. If the horizontal polarization microstrip antenna is simply arranged at 500mm intervals, that is, one antenna unit is placed in each metal frame (hereinafter referred to as "array one"), the array element spacing is about 0.73λ. It is known that the array pattern satisfies the following formula (1)

[0042]

[0043] Among them, θ is the scanning angle, d is the array element spacing, and λ is the antenna operating wavelength.

[0044] It can be seen from formula (1) that the larger the scanning angle θ, the more likely it is that grating lobes will appear, and when the maximum scanning angle is 60°, the unit spacing must be no greater than 0.54λ to prevent grating lobes from appearing. Therefore, simply adopting the array one solution will produce larger grating lobes, and when the microstrip antenna beam is narrow, the gain in the large angle direction is low. When the array is integrated, the grating lobe gain will be greater than the main lobe gain. The simulation results also confirm this by calculating the array pattern by multiplying the unit pattern and the array factor to obtain the array pattern. Figure 2 The following is the simulation result of the radiation pattern of the first array scheme at the operating frequency f0+30MHz and the scanning angle of 60°. It can be seen that the gain in the direction of the main beam is about 20dBi, the side lobe level is -7dB, and a grating lobe with a gain greater than the main lobe appears near -5°. After further simulation analysis, there are two main reasons for the appearance of the grating lobe. One is that when the array scans to 60°, the array factor has a grating lobe as large as the main lobe. On the other hand, the beam of the microstrip antenna is not wide, and the unit gain in the 60° direction is less than that in the 0° direction. Therefore, when the two are multiplied, a grating lobe greater than the main lobe appears.

[0045] It can be seen from the above formula (1) that the smaller the array element spacing is, the larger the range of the scanning angle θ is. Therefore, the present invention proposes to increase the range of the scanning angle θ by reducing the array element spacing, and to reduce the spacing between the elements to 0.365λ by placing two elements in a metal frame to prevent the appearance of grating lobes. Specifically, Figure 3 As shown (hereinafter, this solution is referred to as "array 2" for short). At this time, the array element spacing is less than 0.54λ, so no grating lobe will appear when the array performs ±60° scanning in the horizontal direction. Figure 4 The simulation results of the radiation pattern of the second array scheme at the operating frequency f0+30MHz and the scanning angle of 60° show that the gain of the main beam pointing direction of the second array scheme is about 22.8dBi, the sidelobe level is 12dB, and there is no grating lobe. However, the second array scheme needs to solve two difficulties. On the one hand, the antenna size must be small enough to be placed in a limited space. On the other hand, when the array element spacing is 0.365λ, the coupling between the units is very strong, which makes the standing wave of the antenna and the isolation between the ports deteriorate sharply.

[0046] In order to solve these two difficulties, the present invention proposes to rotate the antenna in the second array solution by 45° and place it diagonally in each metal frame, thereby increasing the size of each microstrip antenna. Figure 5As shown (hereinafter referred to as "array three"). In order to eliminate the coupling between the two microstrip antennas in the same metal frame, orthogonally polarized feeding ports are set for the two microstrip antennas in each metal frame. The two orthogonally polarized ports are fed simultaneously, and the functions of horizontal polarization radiation and vertical polarization radiation are achieved by adjusting the phase. Since the input power of the antenna is independent of its gain, it can be simplified to calculate the horizontal polarization pattern and the vertical polarization pattern separately during the simulation calculation. Ideally, the array has the same pattern when working in the horizontal polarization radiation mode and the vertical polarization mode, so only the pattern of one working mode is calculated. Figure 6 The simulation results of the directivity diagram of the third array scheme at the operating frequency f0+30MHz and the scanning angle of 60° show that the gain of the main beam pointing direction is about 22.9dBi, the side lobe level is 12dB, and no grating lobe appears.

[0047] Through the above continuous improvement of the array structure, array scheme three has the best performance, can meet the antenna design indicators within the scanning angle of ±60°, increases the beam scanning coverage range, and is completely conformal to the platform, and is suitable as the final array structure of the antenna array proposed in the present invention.

[0048] Next, the design concept of the unit structure of the present invention is introduced.

[0049] According to the above simulation results, we can see that most array designs have requirements on the size of the microstrip antenna, so the design of the unit focuses on the miniaturization and wide bandwidth characteristics of the antenna. Figure 7 As shown in the figure. Since the two radiating patches are too close to each other, their standing wave ratio and port isolation deteriorate sharply and cannot reach the ideal index. In order to reduce the influence of mutual coupling, the patches are further miniaturized, which can increase the distance between the patches and the distance between the patches and the metal wall. The result is shown in the figure. Figure 8 shown.

[0050] Using this method, after optimization and adjustment, the standing wave ratio has been well optimized and can basically meet the unit design indicators. Fig. 9 As shown. It can be seen that the radiation performance is good within the frequency band and the standing wave has been optimized to a certain extent, but since no decoupling measures are taken between the two units, there is the same problem as the horizontal polarization unit, that is, the isolation of the ports of the same polarization of the two units is relatively poor. The next optimization design is mainly to reduce the mutual coupling between the ports of the same polarization while maintaining the current standing wave and radiation performance.

[0051] To this end, the antenna unit proposed in the present invention is a double-layer microstrip patch antenna with controllable polarization. Fig.10As shown, the present invention proposes a dual-polarized meter-wave array antenna unit, which includes a metal outer frame 101, two sub-antenna units 102 of equal size, the metal outer frame 101 and the two sub-antenna units 102 are both square, the inner side length of the metal outer frame 101 is twice that of the sub-antenna unit 102, and the two sub-antenna units 102 are respectively located in the upper left and lower right parts of the metal outer frame 101.

[0052] The structure of each sub-antenna unit 102 is as follows: Fig.11 As shown. Each sub-antenna unit includes a square metal wall 111, a square upper microstrip patch 112 and a square lower microstrip patch 113. The height of the metal wall 111 is flush with the upper microstrip patch 112. The lower microstrip patch 113 is arranged in parallel at the positive projection position of the lower part of the upper microstrip patch 112 and is arranged in the center of the area surrounded by the metal wall 111. The edges of the upper microstrip patch 112 and the lower microstrip patch 113 are at an angle of 45° to the edges of the metal wall 111. This form of microstrip antenna meets all the design requirements of the antenna unit, and leaves more margins, and it is easier to achieve dual polarization than other methods. At the same time, in order to increase the maximum scanning angle of the array, the unit spacing is further reduced, and the two units are placed in one grid. And by adding a metal wall of a certain thickness around the patch, the problem of antenna standing wave deterioration caused by the close distance between the two patches after placing the two units in one grid is solved.

[0053] At the antenna operating frequency, the sea surface can be regarded as a conductor. The tangential component of the electric field on the surface of an ideal conductor is zero, but the normal component is not zero. For horizontally polarized beams, the sea surface will reflect, causing the beam to tilt upward and increase the gain, which is suitable for detecting long-distance high-altitude targets. For vertically polarized beams, the beam can be closer to the sea surface without tilting upward, so it can cover the low elevation angle area well, allowing the radar to detect low-flying targets close to the sea surface. Dual-polarized microstrip antenna arrays can form Fig.12 Two polarization operating modes are shown.

[0054] Therefore, in Fig.11 Based on the structure of the invention, the polarization mode of the antenna is increased by adding input ports to realize two polarization modes. When the input power of a single port remains unchanged, increasing the number of ports can increase the transmission power. By adjusting the phase of the input signals of the two ports, electromagnetic waves of two polarization directions, vertical polarization and horizontal polarization, can be obtained respectively. Fig.13 It shows the principle of horizontal polarization synthesis of antenna units. Fig.14The vertical polarization synthesis principle of the antenna unit is shown. Each sub-antenna unit 102 is provided with two ports, and the polarization mode of the sub-antenna unit 102 is controlled by controlling the phase of the port input signal. When the phases of the two ports are both 0°, the antenna unit operates in the horizontal polarization mode. When the phase of one port is 0° and the phase of the other port is 180°, the antenna unit operates in the vertical polarization mode.

[0055] Another implementation of the antenna array proposed by the present invention is as follows Fig.14 As shown. In this embodiment, the antenna array is a 3×3 array, which is composed of a plurality of dual-polarized meter-wave array antenna units, wherein the structure of each antenna unit is the same as that in the above embodiment, and each dual-polarized meter-wave array antenna unit includes a metal outer frame and two sub-antenna units of equal size, the metal outer frame and the two sub-antenna units are both square, the inner side length of the metal outer frame is twice that of the sub-antenna unit, and the two sub-antenna units are respectively located in the upper left and lower right parts of the metal outer frame; each sub-antenna unit is provided with two ports for realizing horizontal polarization or vertical polarization of the sub-antenna unit.

[0056] 18 sub-antenna units were tested, and all antennas were numbered (numbered 1 to 18). The standing wave ratios of all 18 antenna units were tested, and 6 antenna units (No. 3 / 6 / 9 / 12 / 15 / 18) were selected for port isolation tests, and 3 antenna units (No. 2 / 8 / 14) were selected for pattern tests. The test results show that the standing wave ratio of each sub-antenna unit is lower than 1.8 in most frequency bands and lower than 2 in the full frequency band; the unit port isolation is lower than -20dB or near within the frequency band; the cross-polarization test value is generally lower than -15dB; the array pattern test results show that the antenna array can achieve good beam scanning within the range of ±60°.

[0057] Based on the integrated design of the structure of the metric-wave phased array antenna, the present invention proposes the use of antenna unit design technology to ensure that the half-power beam width of the antenna unit pattern is greater than the required scanning beam coverage of the phased array sub-array antenna, and the antenna scanning angle is increased from the original 90° to 120°; through the reasonable layout of the distributed phased array antenna system, the flexibility of the antenna array is improved, and the beam airspace coverage problem that cannot be achieved by a single phased array antenna is solved. Miniaturization, integration, conformal with the platform, increased beam scanning coverage, and dual polarization to improve the measurement data rate are achieved.

[0058] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A dual-polarized meter-wave array antenna unit, the antenna unit comprising a metal outer frame (101) and two sub-antenna units (102) of equal size, the metal outer frame (101) and the two sub-antenna units (102) are both square, the inner side length of the metal outer frame (101) is twice that of the sub-antenna unit (102), and the two sub-antenna units (102) are respectively located in the upper left and lower right parts of the metal outer frame (101); wherein, Each sub-antenna unit (102) includes a square metal wall (111), a square upper microstrip patch (112) and a square lower microstrip patch (113); The height of the metal wall (111) is flush with that of the upper microstrip patch (112); the lower microstrip patch (113) is loaded with a high dielectric constant to achieve miniaturization, and is arranged in parallel at the lower positive projection position of the upper microstrip patch (112) and in the center of the enclosed area of ​​the metal wall (111); the edges of the upper microstrip patch (112) and the lower microstrip patch (113) form an angle of 45° with the edge of the metal wall (111).

2. The dual-polarized meter-wave array antenna unit according to claim 1, characterized in that: Each sub-antenna unit (102) is provided with two ports, and the polarization mode of the sub-antenna unit (102) is controlled by controlling the phase of the input signal of the port.

3. The dual-polarized meter-wave array antenna unit according to claim 2, characterized in that: When the phases of the two ports are both 0°, the antenna unit operates in a horizontal polarization mode.

4. The dual-polarized meter-wave array antenna unit according to claim 2, characterized in that: When the phase of one port is 0° and the phase of the other port is 180°, the antenna unit operates in vertical polarization mode.

5. An antenna array, characterized in that: It comprises a plurality of dual-polarized meter-wave array antenna units as described in any one of claims 1 to 4.

6. The antenna array according to claim 5, characterized in that: The antenna array is a 3x3 array.

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