A dual-polarized meter-wave array antenna unit and antenna array

Abstract

The present invention proposes a dual-polarized meter-wave array antenna unit, comprising a metal outer frame and two equal-sized sub-antenna units. The metal outer frame and the two sub-antenna units are square, with the inner side length of the metal outer frame being twice the side length of the sub-antenna units. The two sub-antenna units are located in the upper left and lower right portions of the metal outer frame, respectively. Each sub-antenna unit comprises a square metal wall, a square upper microstrip patch, and a square lower microstrip patch. The metal wall is flush with the upper microstrip patch, and the lower microstrip patch is arranged parallel to the lower orthographic projection of the upper microstrip patch and centered within the area enclosed by the metal wall. The edges of the upper and lower microstrip patches form a 45° angle with the edges of the metal wall. The lower microstrip patch is loaded with a high-dielectric-constant dielectric, thereby miniaturizing the antenna. The antenna unit is conformally integrated with the carrier platform, increasing the beam scanning coverage range, and dual polarization improves the measurement data rate.

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. By arranging a large number of small antenna elements into an antenna array, a main beam with different phases is formed. Corresponding phase changes can be made in two axes. The electromagnetic waves emitted by each phase shifter in 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 wide-area beam coverage with the servo system of traditional mechanically scanned antennas. Therefore, expanding the beam scanning range of phased arrays is a hot research topic in this field. The difficulty lies in the inherent limitations of the scanning angle of phased array antennas. Traditional planar phased array antennas can typically only maintain good performance within a beam scanning range of ±45°. Array antenna theory shows that the main factor that constrains the scanning angle of a phased array antenna is the array element. The directional pattern of an array antenna can be obtained by multiplying the element pattern factor by the array factor. The elements used in actual phased array antennas are not ideal isotropic radiators, and the beamwidth of the array element is limited. When the gain of the array element antenna in a given direction significantly decreases from its maximum value, the gain of the phased array antenna will also be significantly attenuated. Furthermore, the input impedance of the antenna port is not constant. As the scanning angle increases, the mutual coupling between the array elements increases, which to a certain extent affects the input impedance of the antenna port, deteriorating the impedance matching and leading to deterioration in the performance of the phased array antenna at large scanning angles.

[0004] Polarization is also a crucial wireless resource. Fully utilizing it can improve system transmission rates and channel capacity, mitigate multipath-induced fading, and significantly improve system performance. Within the limited antenna unit size, achieving a greater number of polarizations and selecting the appropriate polarization method are also factors to consider.

[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 optimize the performance of the antenna unit on this platform is also a problem to be solved by this invention. At the same time, the relative bandwidth of a phased array radar, also known as percentage bandwidth, refers to the ratio of the width of the system's operating frequency range to its center frequency. This indicator provides a measure of the frequency variation that a 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] Aiming at the problems of small scanning range of phased array radar antenna scanning beam and large antenna size, the present invention proposes a dual-polarized meter-wave array antenna unit and 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 includes 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 the side length of the sub-antenna unit 102. 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 parallel to 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 a 45° angle 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 meter-wave phased array antenna structure, this invention proposes the use of antenna unit design technology to ensure that the half-power beamwidth of the antenna unit pattern is greater than the required phased array sub-array antenna scanning beam coverage range, and the antenna scanning angle is increased from the original 90° to 120°. Through the rational layout of the distributed phased array antenna system, the flexibility of the antenna array is improved, and the beam space coverage problem that cannot be achieved by a single phased array antenna is solved. The system achieves miniaturization, integration, conformity with the platform, increases the beam scanning coverage range, and dual polarization improves the measurement data rate. 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 following briefly introduces the drawings required for describing the embodiments or the prior art.

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

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

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

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

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

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

[0022] Figure 7 The three-dimensional structure diagram of the placement of the dual-polarized microstrip antenna in the array 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] Figure 9 The VSWR simulation results of the miniaturized dual-polarized microstrip antenna in the array's three structures are shown below.

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

[0026] Figure 11 This is a schematic diagram of the three-dimensional structure of the sub-antenna unit proposed in the present invention;

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

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

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

[0030] Figure 15 This is a schematic structural diagram of an embodiment of the antenna array proposed in the present invention. DETAILED DESCRIPTION

[0031] To make the technical problems, technical solutions and advantages of 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 will be able to 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: ±60° horizontally;

[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 antenna size issues, and 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] (1)

[0043] in, is the scanning angle, is the array element spacing, and λ is the antenna operating wavelength.

[0044] From formula (1), we can see that the scanning angle The larger the angle, the more likely grating lobes will appear. At a maximum scan angle of 60°, the element spacing must be no greater than 0.54λ to prevent grating lobes. Therefore, simply adopting the array-one solution will produce larger grating lobes. Furthermore, when the microstrip antenna beam is narrow, the gain at large angles is low. When the array is synthesized, the grating lobe gain will exceed the main lobe gain. Simulation results, which calculate the array pattern by multiplying the element pattern and the array factor, confirm this. Figure 2 The following is the simulated pattern of array solution 1 at an operating frequency of f0 + 30 MHz and a scan angle of 60°. It can be seen that the gain in the main beam direction is approximately 20 dBi, the sidelobe level is -7 dB, and a grating lobe with a gain greater than the main lobe appears near -5°. Further simulation analysis reveals two main reasons for the grating lobes. First, when the array scans to 60°, the array factor produces grating lobes equal in size to the main lobe. Second, the microstrip antenna's beam is not wide, and the unit gain at 60° is less than that at 0°. Therefore, when these two factors are multiplied, a grating lobe larger than the main lobe appears.

[0045] From the above formula (1), it can be seen that the smaller the array element spacing is, the smaller the scanning angle is. Therefore, the present invention proposes to increase the scanning angle by reducing the array element spacing. By placing two units in a metal frame, the spacing between units is reduced to 0.365λ to prevent the occurrence of grating lobes. Figure 3 As shown in the figure (hereinafter referred to as "array 2"), the array element spacing is less than 0.54λ, so no grating lobes appear when the array scans ±60° horizontally. Figure 4 The following is the simulated pattern result for Array 2 at an operating frequency of f0+30MHz and a scan angle of 60°. It shows that the gain of Array 2's main beam pointing direction is approximately 22.8dBi, the sidelobe level is 12dB, and there are no grating lobes. However, Array 2 faced two challenges: first, the antenna size had to be small enough to fit within a limited space. Second, when the element spacing is 0.365λ, the coupling between elements is very strong, which significantly degrades the antenna's standing waves and the isolation between ports.

[0046] In order to solve these two difficulties, the present invention proposes to rotate the antenna in the second array solution by 45 degrees 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"), to eliminate coupling between the two microstrip antennas in the same metal frame, orthogonally polarized feed ports are provided for each of the two microstrip antennas in the metal frame. These two orthogonally polarized ports are fed simultaneously, and phase adjustment is used to achieve both horizontally and vertically polarized radiation. Because the input power to the antenna is independent of its gain, simulation calculations can be simplified to calculating the horizontal and vertical polarization patterns separately. Ideally, the array's radiation patterns are identical when operating in both horizontal and vertical polarization modes, so only the pattern for one operating mode is calculated. Figure 6 The following are the simulation results of the directivity pattern of the third array scheme at the operating frequency f0+30MHz and the scanning angle of 60°. It can be seen that the gain of the main beam pointing direction is about 22.9dBi, the sidelobe level is 12dB, and no grating lobes appear.

[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°, increase the beam scanning coverage range, and is completely conformal to the platform, making it suitable as the final array structure of the antenna array proposed in this 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 for the size of the microstrip antenna, so the design of the unit focuses on the miniaturization and wide bandwidth characteristics of the antenna. In the above three array schemes, the placement of the two dual-polarized microstrip antennas in the metal frame is enlarged as shown in the figure. 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] By adopting this method, after optimization and adjustment, the standing wave ratio is well optimized and can basically meet the unit design indicators. Figure 9 As shown in the figure, radiation performance is good across the frequency band, and standing wave performance has been optimized to a certain extent. However, due to the lack of any decoupling measures between the two units, the same problem as the horizontally polarized units exists: poor isolation between the ports of the same polarization. The subsequent optimization design will focus on reducing the mutual coupling between 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. Figure 10As shown, the present invention proposes a dual-polarized meter-wave array antenna unit, which includes 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 squares. The inner side length of the metal outer frame 101 is twice the side length of the sub-antenna unit 102. 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: Figure 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 parallel to the lower positive projection 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 a 45° angle with the edges of the metal wall 111. This type of microstrip antenna meets all the design requirements of the antenna unit and leaves a large margin. It is also 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 two units are placed in one grid. A metal wall of a certain thickness is added around the patch to solve the problem of strong mutual coupling caused by the close distance between the two patches when the two units are placed in the same grid. The patch is also too close to the metal wall, which deteriorates the antenna standing wave.

[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, while the normal component is not zero. For horizontally polarized beams, the sea surface will reflect, causing the beam to tilt upward, increasing the gain, and is suitable for detecting long-range high-altitude targets. For vertically polarized beams, the beam can be closer to the sea surface without tilting upward, so it can cover low elevation angle areas well, allowing the radar to detect low-flying targets close to the sea surface. Dual-polarized microstrip antenna arrays can form Figure 12 Two polarization operating modes are shown.

[0054] Therefore, in Figure 11 Based on the existing structure, the present invention increases the number of antenna polarization modes by adding input ports, achieving dual polarization. While the input power of a single port remains constant, increasing the number of ports can increase the transmit power. By adjusting the phase of the input signals at the two ports, electromagnetic waves with vertical and horizontal polarization can be generated. Figure 13 It shows the principle of horizontal polarization synthesis of antenna units. Figure 14This figure illustrates the principle of vertical polarization synthesis for antenna units. Each sub-antenna unit 102 is equipped with two ports. The polarization of the sub-antenna unit 102 is controlled by controlling the phase of the input signal at the ports. When the phase of both ports is 0°, the antenna unit operates in 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 vertical polarization mode.

[0055] Another embodiment of the antenna array proposed by the present invention is as follows Figure 14 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. 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, and the inner side length of the metal outer frame is twice the side length of the sub-antenna unit. 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] Eighteen antenna sub-units were tested, each numbered 1 to 18. The standing wave ratio (SWR) of all 18 antenna units was tested, and port isolation was tested on six antenna units (numbers 3, 6, 9, 12, 15, and 18), and pattern testing was performed on three antenna units (numbers 2, 8, and 14). The test results showed that the SWR of each sub-antenna unit was below 1.8 across most of the frequency band and below 2 across the entire frequency band. Unit port isolation was below or near -20 dB across the frequency band. Cross-polarization test values ​​were generally below -15 dB. Array pattern testing demonstrated that the antenna array was capable of achieving good beam scanning within a ±60° range.

[0057] Based on the integrated design of the meter-wave phased array antenna structure, this invention proposes the use of antenna unit design technology to ensure that the half-power beamwidth of the antenna unit pattern is greater than the required phased array sub-array antenna scanning beam coverage range, and the antenna scanning angle is increased from the original 90° to 120°. Through the rational layout of the distributed phased array antenna system, the flexibility of the antenna array is improved, and the beam space coverage problem that cannot be achieved by a single phased array antenna is solved. The system achieves miniaturization, integration, conformity with the platform, increases the beam scanning coverage range, and dual polarization improves the measurement data rate.

[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 within 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 the side length 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 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 positive projection position of the lower part of the upper microstrip patch (112), and is arranged in the center of the encircled area of ​​the metal wall (111); the edges of the upper microstrip patch (112) and the lower microstrip patch (113) form a 45° angle with the edge of the metal wall (111); 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.

2. The dual-polarized meter-wave array antenna unit according to claim 1, wherein: When the phases of the two ports are both 0°, the antenna unit operates in a horizontal polarization mode.

3. The dual-polarized meter-wave array antenna unit according to claim 2, wherein: 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.

4. 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 3.

5. The antenna array according to claim 4, wherein: The antenna array is a 3x3 array.

Images