Antenna array decoupling structure based on coupled electromagnetic waves and design method thereof

Abstract

The invention discloses an antenna array decoupling structure based on coupled electromagnetic waves and a design method thereof, and relates to the technical field of antenna decoupling, the antenna array decoupling structure comprises a microwave absorber unit and a radiator unit; the microwave absorber unit is arranged between adjacent antenna units of the antenna array and is used for absorbing coupling electromagnetic waves between the adjacent antenna units; the radiator unit is connected with the microwave absorber unit through the feed network structure, and the coupled electromagnetic waves absorbed by the microwave absorber are radiated out, so that the radiation performance of the antenna array is improved; according to the above structure, the microwave absorber is utilized to absorb coupling electromagnetic waves, coupling between adjacent antenna units of the antenna array is reduced, and meanwhile, secondary radiation can be carried out through the radiator unit so as to enhance the radiation performance of the antenna array.

Description

Technical Field

[0001] The present application relates to the field of antenna decoupling technology, and in particular to an antenna array decoupling structure based on coupled electromagnetic waves and a design method thereof. Background Art

[0002] In antenna array design, achieving a compact layout while maintaining excellent performance is a pressing challenge. To accommodate multiple antenna elements within a limited space, element spacing becomes a key factor in determining the final size. The closer the antenna elements are, the stronger the coupling between them. This coupling can alter the current distribution within the antenna elements, thereby reducing overall antenna performance.

[0003] Currently, there are various technical means for MIMO antenna decoupling, including defective ground structure (DGS), electromagnetic band gap structure (EBG), and array-antenna decoupling surface (ADS). These methods have shown significant results in reducing antenna array coupling, but each method also has its limitations. DGS technology's etching on the backplane may lead to a significant increase in backward radiation, which has a negative impact on antenna performance; EBG structure is generally suitable for microstrip antennas and requires special design for antennas of different structures, which limits its scope of application; although ADS technology performs well in base station antenna decoupling, its design of being directly installed above the antenna unit will significantly increase the antenna cross-section.

[0004] Therefore, how to improve the radiation performance of the antenna array while optimizing the coupling in the antenna array has become a technical challenge that needs to be overcome urgently in this field. Summary of the Invention

[0005] The purpose of this application is to provide an antenna array decoupling structure based on coupled electromagnetic waves and a design method thereof, which can reduce the coupling between adjacent antenna units of the antenna array while enhancing the radiation performance of the antenna array.

[0006] To achieve the above objectives, this application provides the following solutions:

[0007] In a first aspect, the present application provides an antenna array decoupling structure based on coupled electromagnetic waves, comprising: a microwave absorber unit and a radiator unit; the microwave absorber unit is arranged between adjacent antenna units of the antenna array, and the microwave absorber unit is used to absorb the coupled electromagnetic waves between adjacent antenna units, thereby reducing the coupling between adjacent antenna units of the antenna array; the input impedance of the radiator unit is adjustable; the radiator unit is connected to the microwave absorber unit through a feeding network structure, and the radiator unit is used to radiate the coupled electromagnetic waves absorbed by the microwave absorber, thereby improving the radiation performance of the antenna array; the output impedance of the microwave absorber unit is conjugate matched with the input impedance of the radiator unit.

[0008] Optionally, the microwave absorber unit includes: a first dielectric substrate and a periodic resistance structure and a metal backplate respectively arranged on the top and bottom of the first dielectric substrate; the periodic resistance structure includes a plurality of periodically distributed ring loops and a chip resistor arranged on each ring loop; the chip resistor is used to adjust the input impedance of the microwave absorber and provide two output ports for radiation utilization of subsequent radiator units.

[0009] Optionally, the radiator unit includes: a second dielectric substrate and a pair of radiating dipoles, a pair of coupling feeding branches and a pair of input impedance adjustment metal rings arranged on the second dielectric substrate; the two coupling feeding branches are respectively connected to the two output ports on the microwave absorber unit through a feeding network structure to receive coupled electromagnetic waves, the radiating dipoles are used to radiate the received coupled electromagnetic waves, and the input impedance adjustment metal rings are used to adjust the input impedance of the radiator unit.

[0010] Optionally, the feeding network structure includes: a third dielectric substrate and a first feeding branch and a second feeding branch arranged on both sides of the third dielectric substrate; the third dielectric substrate is arranged between the microwave absorber unit and the radiator unit, and the third dielectric substrate is parallel to the first dielectric substrate and perpendicular to the second dielectric substrate; one end of the first feeding branch is connected to an output port on the microwave absorber unit, and the other end of the first feeding branch is connected to a coupling feeding branch on the radiator unit; one end of the second feeding branch is connected to another output port on the microwave absorber unit, and the other end of the second feeding branch is connected to another coupling feeding branch on the radiator unit.

[0011] Optionally, the first feeding branch includes a first metal via and a first metal microstrip; the second feeding branch includes a second metal via and a second metal microstrip; and one surface of the third dielectric substrate and the metal backplane of the first dielectric substrate are mutually extended surfaces.

[0012] One end of the first metal via is connected to an output port on the microwave absorber unit. The first metal via extends perpendicularly toward the metal backplate within the first dielectric substrate. When there is a fixed interval between the first metal via and the metal backplate, the other end of the first metal via is connected to one end of a first metal microstrip perpendicular to the first metal via. The fixed interval is the thickness of the third dielectric substrate. The first metal microstrip extends in a direction perpendicular to the second dielectric substrate. The other end of the first metal microstrip is connected to a coupling feed branch on the radiator unit.

[0013] One end of the second metal via is connected to another output port on the microwave absorber unit, the second metal via extends perpendicularly toward the metal backplate within the first dielectric substrate, and the other end of the second metal via passes through the first dielectric substrate and is connected to the metal backplate; one end of the second metal microstrip is connected to the metal backplate, the second metal microstrip extends in a direction perpendicular to the second dielectric substrate, and the other end of the second metal microstrip is connected to another coupling feed branch on the radiator unit.

[0014] Optionally, a single annular loop includes four square loops with missing corners on four corners, and the gaps between two adjacent square loops with missing corners are connected by a chip resistor; after a chip resistor located in the middle of the annular loop in the microwave absorber unit is removed, the free branches of the two adjacent square loops with missing corners form two output ports of the microwave absorber unit.

[0015] In a second aspect, the present application provides a design method for an antenna array decoupling structure based on coupled electromagnetic waves, comprising the following steps:

[0016] Based on the frequency bandwidth of the coupled electromagnetic waves between adjacent antenna units of the antenna array, a microwave absorber unit is designed; the microwave absorber unit is used to absorb the coupled electromagnetic waves between adjacent antenna units of the antenna array, thereby reducing the coupling between adjacent antenna units of the antenna array.

[0017] The antenna array is simulated and analyzed to determine the position of the microwave absorber unit in the antenna array and the output port of the microwave absorber unit; the microwave absorber unit is arranged between adjacent antenna units in the antenna array.

[0018] A radiator unit is designed based on the goal of utilizing the coupled electromagnetic waves absorbed by the microwave absorber unit for secondary radiation to improve the antenna array gain and adjust the input impedance.

[0019] According to the output port of the microwave absorber unit and the goal of impedance conjugate matching, a feeding network structure is designed.

[0020] Based on the feeding network structure, the microwave absorber unit and the radiator unit are connected to obtain an antenna array decoupling structure based on coupled electromagnetic waves; the radiator unit is used to radiate the coupled electromagnetic waves absorbed by the microwave absorber, thereby improving the radiation performance of the antenna array.

[0021] Optionally, the microwave absorber unit includes: a first dielectric substrate and a periodic resistance structure and a metal backplate respectively arranged on the top and bottom of the first dielectric substrate; the periodic resistance structure includes a plurality of periodically distributed ring loops and a chip resistor arranged on each ring loop; the chip resistor is used to adjust the input impedance of the microwave absorber and provide two output ports for radiation utilization of subsequent radiator units.

[0022] Optionally, the radiator unit includes: a second dielectric substrate and a pair of radiating dipoles, a pair of coupling feeding branches and a pair of input impedance adjustment metal rings arranged on the second dielectric substrate; the two coupling feeding branches are respectively connected to the two output ports on the microwave absorber unit through a feeding network structure to receive coupled electromagnetic waves, the radiating dipoles are used to radiate the received coupled electromagnetic waves, and the input impedance adjustment metal rings are used to adjust the input impedance of the radiator unit.

[0023] Optionally, the feeding network structure includes: a third dielectric substrate and a first feeding branch and a second feeding branch arranged on both sides of the third dielectric substrate; the third dielectric substrate is arranged between the microwave absorber unit and the radiator unit, and the third dielectric substrate is parallel to the first dielectric substrate and perpendicular to the second dielectric substrate; one end of the first feeding branch is connected to an output port on the microwave absorber unit, and the other end of the first feeding branch is connected to a coupling feeding branch on the radiator unit; one end of the second feeding branch is connected to another output port on the microwave absorber unit, and the other end of the second feeding branch is connected to another coupling feeding branch on the radiator unit.

[0024] According to the specific embodiments provided in this application, this application discloses the following technical effects:

[0025] The present application provides an antenna array decoupling structure based on coupled electromagnetic waves and a design method thereof, wherein the antenna array decoupling structure includes a microwave absorber unit arranged between adjacent antenna units of the antenna array for absorbing coupled electromagnetic waves between adjacent antenna units and reducing coupling between adjacent antenna units of the antenna array, and a radiator unit connected to the microwave absorber unit through a feeding network structure for radiating the coupled electromagnetic waves absorbed by the microwave absorber to improve the radiation performance of the antenna array. The impedances of the two are conjugate matched to achieve maximum power transmission of the antenna radiator. The above-mentioned decoupling structure of the present application can effectively utilize the coupled electromagnetic waves between adjacent antenna units of the antenna array. While utilizing the microwave absorber to absorb the coupled electromagnetic waves and reduce coupling between adjacent antenna units of the antenna array, the radiator unit also performs secondary radiation based on this to enhance the radiation performance of the antenna array. While improving the isolation performance of the antenna array, it can also improve the radiation performance of the antenna array. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0027] Figure 1 A schematic diagram of an antenna array decoupling structure based on coupled electromagnetic waves provided in one embodiment of the present application.

[0028] Figure 2 The figure is a schematic diagram of the structure of a simple antenna array consisting of two ±45° crossed dipole antenna units and a metal reflector.

[0029] Figure 3 A schematic structural diagram of a microwave absorber unit in an antenna array decoupling structure based on coupled electromagnetic waves provided in one embodiment of the present application.

[0030] Figure 4 A top view of a microwave absorber unit in an antenna array decoupling structure based on coupled electromagnetic waves provided in one embodiment of the present application.

[0031] Figure 5 Schematic diagram of the effect of placing a 1×5 microwave absorber structure on an antenna array.

[0032] Figure 6 A schematic structural diagram of a radiator unit in an antenna array decoupling structure based on coupled electromagnetic waves provided in one embodiment of the present application.

[0033] Figure 7A top view of a radiator unit in an antenna array decoupling structure based on coupled electromagnetic waves provided in one embodiment of the present application.

[0034] Figure 8 This is a schematic diagram of the effect of an antenna array decoupling structure based on coupled electromagnetic waves provided in one embodiment of the present application being set on an antenna array.

[0035] Figure 9 Schematic diagram of the isolation curve between port 2 and port 4 before and after the antenna array decoupling structure is loaded in one embodiment of the present application.

[0036] Figure 10 FIG. 1 is a schematic diagram of a curve showing the return loss of port 2 after the antenna array decoupling structure is loaded in an embodiment of the present application.

[0037] Figure 11 Schematic diagram of the curve showing the effect of gain in the frequency range of 3 GHz to 5 GHz before and after the antenna array decoupling structure is loaded in one embodiment of the present application.

[0038] Figure 12 This is the achievable gain pattern at 3.5 GHz before and after the antenna array decoupling structure is loaded in one embodiment of the present application.

[0039] Figure 13 This is the achievable gain pattern at 4.9 GHz before and after the antenna array decoupling structure is loaded in one embodiment of the present application.

[0040] Figure 14 Schematic diagram of current distribution on the radiating structure before and after the antenna array decoupling structure is loaded in one embodiment of the present application.

[0041] Figure 15 A flowchart of a design method for an antenna array decoupling structure based on coupled electromagnetic waves provided in one embodiment of the present application.

[0042] Reference numerals:

[0043] 1: Microwave absorber unit; 2: Radiator unit; 3: Feed network structure; 1-1: First dielectric substrate; 1-2, 1-3, 1-4, 1-5: Ring loop; 1-6, 1-7, 1-8, 1-9: Chip resistors; 1-10: Metal backplane; 2-1: Second dielectric substrate; 2-2, 2-3: Radiating dipole; 2-4, 2-5: Coupled feed branches; 2-6, 2-7: Input impedance adjustment metal ring; 2-8: Lumped port used in simulation; 3-1: Third dielectric substrate; 3-2: First metal via; 3-3: Second metal via; 3-4: First metal microstrip; 3-5: Second metal microstrip. DETAILED DESCRIPTION

[0044] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0045] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application is further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0046] The embodiment of the present application provides an antenna array decoupling structure based on coupled electromagnetic waves. In an exemplary embodiment, Figure 1 As shown, the antenna array decoupling structure based on coupled electromagnetic waves includes: a microwave absorber unit and a radiator unit; the microwave absorber unit is arranged between adjacent antenna units of the antenna array, and the microwave absorber unit is used to absorb the coupled electromagnetic waves between adjacent antenna units, thereby reducing the coupling between adjacent antenna units of the antenna array; the input impedance of the radiator unit is adjustable; the radiator unit is connected to the microwave absorber unit through a feeding network structure, and the radiator unit is used to radiate the coupled electromagnetic waves absorbed by the microwave absorber, thereby improving the radiation performance of the antenna array; the output impedance of the microwave absorber unit is conjugate matched with the input impedance of the radiator unit.

[0047] In order to simplify the subsequent verification process, such as Figure 2 The figure shows a simple antenna array consisting of two ±45° crossed dipole antenna units and a metal reflector. The cross dipoles are coaxially fed with a 50-ohm impedance. When ports one and three are fed, the two antennas generate +45° polarized waves. When ports two and four are fed, the two antenna units simultaneously generate -45° polarized waves. The radiating dipole planes of the two antenna units are placed at a height of 18 mm from the metal reflector below. When the antenna units are working, the downward-radiated waves are reflected and returned to be superimposed in phase with the upward-radiated waves to enhance the radiation performance. The metal reflector is a 70 mm × 175 mm aluminum plate with a thickness of 0.8 mm.

[0048] Since the coupling between antenna elements in an antenna array is primarily due to the direct propagation of spatial waves radiated by each element to adjacent antenna elements, the design concept of this embodiment is to utilize this coupled electromagnetic wave. A microwave absorber is used to absorb broadband coupled electromagnetic waves of a specific frequency and dissipate the absorbed energy in other forms. To ensure that the designed microwave absorber can efficiently absorb coupled electromagnetic waves, the first step is to design a periodic resistance structure on the surface of the microwave absorber. To effectively dissipate the absorbed coupled electromagnetic waves, chip resistors can be loaded at appropriate locations on the surface of the microwave absorber. These resistors have two functions: first, they effectively adjust the input impedance of the microwave absorber to match the 377 ohm impedance of free space, achieving excellent absorption performance; second, they provide an output port for the subsequent utilization of the absorbed coupled electromagnetic waves.

[0049] When designing microwave absorbers, the following performance indicators require attention: 1. Absorption rate, which primarily affects decoupling effectiveness. 2. Polarization sensitivity: Given the complex electromagnetic environment near the antenna array, microwave absorbers that are polarization-insensitive can absorb more coupled electromagnetic waves. 3. Incident sensitivity: Given the complex electromagnetic environment near the antenna array, microwave absorbers that are insensitive to the angle of incidence can absorb more coupled electromagnetic waves. 4. Absorption bandwidth: Design requires attention to the antenna array's operating frequency band.

[0050] In a specific embodiment, the microwave absorber unit in the decoupling structure includes: a first dielectric substrate, and a periodic resistor structure and a metal backplate disposed on the top and bottom of the first dielectric substrate, respectively. The periodic resistor structure includes several periodically distributed ring loops and chip resistors disposed on each ring loop. The chip resistors are used to adjust the input impedance of the microwave absorber and provide two output ports for radiation utilization by subsequent radiator units. A single ring loop includes four square loops with missing corners at the four corners, with the gaps between adjacent square loops connected by a chip resistor. After removing a chip resistor from the middle ring loop of the microwave absorber unit, the free branches of the two adjacent square loops with missing corners form the two output ports of the microwave absorber unit.

[0051] like Figure 3 As shown, the top layer of metal loops 1-2, 1-3, 1-4, and 1-5, chip resistors 1-6, 1-7, 1-8, and 1-9, and the bottom layer of metal backplane 1-10 are tightly bonded to the first dielectric substrate 1-1. The first dielectric substrate 1-1 is an FR4 substrate with a relative dielectric constant of 4.4 and dimensions of 13 mm × 13 mm × 7 mm. The resistance of the top layer of chip resistors 1-6, 1-7, 1-8, and 1-9 is 400 ohms. Figure 4This is a top view of the microwave absorber unit, which shows the surface structure of the microwave absorber unit. The microstrip width of the metal ring loops 1-2, 1-3, 1-4, and 1-5 is 0.5 mm. The side length of the four square loops with missing corners at the four corners is 4.5 mm. The length of the middle connecting part connecting the four square loops with missing corners is 3 mm, and the width of the inner corner gap is 1 mm. The size of the chip resistors 1-6, 1-7, 1-8, and 1-9 is 0.5 mm × 1 mm.

[0052] Will Figure 3 The microwave absorber units with a side length of 13mm×13mm and a thickness of 7mm are connected tightly with no gaps on the dielectric side, and the arrangement period is 13mm, thus forming a 1×5 integrated microwave absorber structure with a size of 13mm×65mm and a thickness of 7mm; then it is placed sideways on Figure 2 The middle of the two-element antenna array shown, Figure 5 As shown, the bottom of the 1×5 microwave absorber structure is now tightly fitted with the metal aluminum plate and fixed by hot melt adhesive so that the metal backplane plane of the microwave absorber unit coincides with the vertical plane between the two units, and the center of the 1×5 microwave absorber structure is in a straight line with the center of the two antenna units.

[0053] In order to utilize coupled electromagnetic waves for secondary radiation to increase array gain, a radiator unit capable of radiating energy must be designed. The design of the radiator unit requires attention to the following indicators: Miniaturization. Because the spacing between antenna array elements is generally 0.5 to 1 wavelength, a radiator unit that is too large would not have sufficient space for installation. Return loss should be less than -10dB within the bandwidth, and the bandwidth should be close to the absorption bandwidth of the designed microwave absorber to fully utilize the coupled electromagnetic wave energy. Radiation performance. The radiator unit's polarization, gain, 3dB bandwidth, sidelobe suppression, and other indicators should be as close as possible to the radiation performance of the antenna units in the antenna array used. Otherwise, the radiation performance of the antenna array may be degraded. Input impedance. Because the radiator unit is not fed via a conventional 50-ohm coaxial cable, the designed radiator needs to have a controllable input impedance to match the input source.

[0054] In a specific embodiment, the radiator unit includes: a second dielectric substrate and a pair of radiating dipoles, a pair of coupling feeding branches and a pair of input impedance adjustment metal rings arranged on the second dielectric substrate; the two coupling feeding branches are respectively connected to the two output ports on the microwave absorber unit through a feeding network structure to receive coupled electromagnetic waves, the radiating dipoles are used to radiate the received coupled electromagnetic waves, and the input impedance adjustment metal rings are used to adjust the input impedance of the radiator unit.

[0055] like Figure 6As shown, 2-1 is the second dielectric substrate. The metal parts 2-2 and 2-3 on the top layer are a pair of radiating dipoles, 2-4 and 2-5 are a pair of coupled feed branches, 2-6 and 2-7 are a pair of input impedance adjustment metal rings used to adjust the input impedance of the antenna radiator. In this embodiment, the input impedance adjustment metal rings are rectangular hollow metal rings. 2-8 is the lumped port used in the simulation. The second dielectric substrate 2-1 is an FR4 dielectric board with a relative dielectric constant of 4.4, a thickness of 0.8 mm, and a size of 30 mm × 30 mm. Figure 7 The top view and design parameters of the radiator unit are shown.

[0056] In order to connect the microwave absorber unit and the radiator unit and utilize the radiator unit to secondary radiate the coupled electromagnetic waves absorbed by the microwave absorber unit, it is necessary to connect the two through a feeding network structure. In one embodiment, the feeding network structure includes: a third dielectric substrate and a first feeding branch and a second feeding branch arranged on both sides of the third dielectric substrate; the third dielectric substrate is arranged between the microwave absorber unit and the radiator unit, and the third dielectric substrate is parallel to the first dielectric substrate and perpendicular to the second dielectric substrate; one end of the first feeding branch is connected to an output port on the microwave absorber unit, and the other end of the first feeding branch is connected to a coupling feeding branch on the radiator unit; one end of the second feeding branch is connected to another output port on the microwave absorber unit, and the other end of the second feeding branch is connected to another coupling feeding branch on the radiator unit.

[0057] The first feeding branch includes a first metal via and a first metal microstrip; the second feeding branch includes a second metal via and a second metal microstrip; and one surface of the third dielectric substrate and the metal backplane of the first dielectric substrate are mutually extended surfaces.

[0058] One end of the first metal via is connected to an output port on the microwave absorber unit. The first metal via extends perpendicularly toward the metal backplate within the first dielectric substrate. When there is a fixed interval between the first metal via and the metal backplate, the other end of the first metal via is connected to one end of a first metal microstrip perpendicular to the first metal via. The fixed interval is the thickness of the third dielectric substrate. The first metal microstrip extends in a direction perpendicular to the second dielectric substrate. The other end of the first metal microstrip is connected to a coupling feed branch on the radiator unit.

[0059] One end of the second metal via is connected to another output port on the microwave absorber unit, the second metal via extends perpendicularly toward the metal backplate within the first dielectric substrate, and the other end of the second metal via passes through the first dielectric substrate and is connected to the metal backplate; one end of the second metal microstrip is connected to the metal backplate, the second metal microstrip extends in a direction perpendicular to the second dielectric substrate, and the other end of the second metal microstrip is connected to another coupling feed branch on the radiator unit.

[0060] By simulating and observing the surface current of the microwave absorber unit at the highest frequency point of the absorption rate, it can be found that the periodic structure on the surface of the microwave absorber unit and the metal backplane have anti-phase currents. This will generate magnetic resonance in the dielectric, causing dielectric loss of energy. At the same time, it can be observed that the current density on the surface metal structure is much higher than that on the metal backplane, indicating that there is strong electrical resonance in the surface structure. The strong periodic changes in current cause ohmic losses through the loaded chip resistors, which is the coupled wave energy that needs to be utilized. Therefore, the designed microwave absorber unit is placed in the middle of the antenna array for wave absorption. At this time, the feed port is obviously the resistor position where the antenna array layout is most reasonable when the resistor is replaced by the antenna unit. To simplify the verification, a two-unit array is used, and the microwave absorber unit is placed between the two antenna units. The resistor position on the middle microwave absorber unit is the position that needs to be designed as the feed source.

[0061] In a specific embodiment, the top resistor of the middle unit of the microwave absorber structure is removed, and the first metal via 3-2 is used to connect the surface metal loop and the metal backplane on the free branch on the left, and the first metal microstrip 3-4 is connected to the metal backplane. The free branch on the right uses the second metal via 3-3 to extend upward through the second metal microstrip 3-5 at a distance of 1 mm from the metal backplane. The two feeding metal microstrips extend to the two ports of the radiator unit through a 1 mm thick FR4 third dielectric substrate 3-1. The function of the third dielectric plate 3-1 is to support the radiator unit, and the metal microstrip can be printed to connect the port to the antenna port.

[0062] In order to achieve the maximum power transmission of the antenna radiator, the source impedance Z s and the antenna radiator load impedance Z l Conjugate matching, that is where Z s =R+jX is the output impedance we see from the lead-out port. In order to achieve conjugate matching, the input impedance Z of the antenna radiator l =R-jX, R is the real part of the complex impedance, X is the imaginary part of the complex impedance, and j is the imaginary unit.

[0063] like Figure 8 As shown, the antenna array decoupling structure in this embodiment is loaded on Figure 2The schematic diagram of the antenna array shown in the figure excites port two and port four at the same time. The -45° polarized radiation arms of the two antenna units work at the same time, which will radiate electromagnetic waves to the surroundings at the same time. The radiation wave of the antenna dipole at port two will be incident on the surface of the microwave absorber unit through two paths: direct propagation and reflection from the reflector. Since the surface impedance of the microwave absorber unit matches the free space impedance of 377 ohms, the electromagnetic wave will be directly absorbed and generate electromagnetic resonance in the microwave absorber unit, where strong electric resonance occurs on the surface structure of the microwave absorber unit. The periodic current will continuously pass through the surface resistance and the replaced port, and the port connection The radiator unit is connected and the ports are matched, so for the microwave absorber, this place can be regarded as a resistor with resistance, which will not affect the microwave absorber's wave absorbing effect. At the same time, the absorbed coupling wave is transmitted to the radiator unit through the feeding network, and the radiator unit will work. The working frequency is the frequency of the current change in the surface structure of the absorber, and its frequency is the same as the frequency of the electromagnetic wave radiated at the second port, that is, the radiator unit radiates electromagnetic waves with the same frequency as the antenna. In the previous design, the radiation performance of this radiator unit is close to that of the antenna used, so the waves radiated by the radiator unit can be superimposed on the radiation waves of the two antenna units to improve the radiation performance of the antenna array.

[0064] In order to prove the effect of the solution of this embodiment, the subsequent comparisons are Figure 2 and Figure 8 The effect of the antenna array shown is compared when port 2 and port 4 are fed simultaneously. The difference between the two antenna arrays is only whether the antenna array decoupling structure of this embodiment is loaded or not. Figure 9 This is a schematic diagram of the isolation between port 2 and port 4 before and after the antenna array decoupling structure is loaded. After loading the structure, the isolation is improved by about 10dB; Figure 10 The return loss of port 2 after loading the antenna array decoupling structure is shown. It can be seen that loading this structure does not significantly affect the operating bandwidth. Figure 11 In order to load the gain effect of the antenna array decoupling structure in the frequency range of 3GHz to 5GHz, this embodiment mainly focuses on the two frequencies of 3.5GHz and 4.9GHz. Figure 12 and Figure 13 The achievable gain patterns before and after loading the structure at two frequency points, 3.5 GHz and 4.9 GHz, are shown. It can be seen that the gain is improved at the frequency of interest, and at 4.9 GHz, the gain is increased while the side lobes are reduced, effectively improving the radiation performance of the antenna array.

[0065] Figure 14 The figure shows the plane where the radiating arm is located, and the current distribution on the radiating structure before and after the decoupling structure of the antenna array is loaded. In the physical aperture, due to the additional radiating unit, the in-phase current J3 is generated by the coupled electromagnetic wave. The basic knowledge of antennas can be used to understand the directivity of the antenna. Here, Ω is the solid angle, The maximum radiation power density on a spherical surface in the far field of the antenna, in the polar coordinate system, is the azimuth angle, θ is the elevation angle, Ω A is the antenna’s beam range. At the same time, the antenna’s directivity can also be calculated by the antenna’s radiation aperture. When the wavelength is given, Among them, λ is the given wavelength mentioned above, that is, the wavelength corresponding to the antenna operating frequency, A e is the effective aperture of the antenna, and for an actual antenna, it has an actual physical aperture A p , so that a caliber efficiency can be defined The gain of the antenna is an actual parameter. Due to various losses in reality, it is less than the directivity. It can be seen as G = kD, where k is the efficiency factor. From the above formula, it can be seen that if you want to increase the antenna gain, you need to increase the efficiency factor k. In actual operation, improving the aperture efficiency is one way to improve the efficiency factor. The reason why this method can achieve the increase in antenna array gain is that the added antenna radiator can add an additional in-phase current path in the original array aperture, making the physical aperture A p The radiation power density on the surface is enhanced, which is equivalent to the power density remaining unchanged, and the effective aperture A e The gain is increased by improving the aperture efficiency of the array.

[0066] Based on the same inventive concept, the embodiment of the present application also provides a method for designing the above-mentioned antenna array decoupling structure based on coupled electromagnetic waves. The solution provided by this method is similar to the solution described in the above-mentioned device. In an exemplary embodiment, Figure 15 As shown, a design method for an antenna array decoupling structure based on coupled electromagnetic waves is provided, comprising the following steps:

[0067] S1. Based on the frequency bandwidth of the coupled electromagnetic waves between adjacent antenna units of the antenna array, a microwave absorber unit is designed; the microwave absorber unit is used to absorb the coupled electromagnetic waves between adjacent antenna units of the antenna array, thereby reducing the coupling between adjacent antenna units of the antenna array.

[0068] When designing microwave absorbers, the following performance indicators require attention: 1. Absorption rate, which primarily affects decoupling effectiveness. 2. Polarization sensitivity: Given the complex electromagnetic environment near the antenna array, microwave absorbers that are polarization-insensitive can absorb more coupled electromagnetic waves. 3. Incident sensitivity: Given the complex electromagnetic environment near the antenna array, microwave absorbers that are insensitive to the angle of incidence can absorb more coupled electromagnetic waves. 4. Absorption bandwidth: Design requires attention to the antenna array's operating frequency band.

[0069] S2. Perform simulation analysis on the antenna array to determine the position of the microwave absorber unit in the antenna array and the output port of the microwave absorber unit; the microwave absorber unit is arranged between adjacent antenna units in the antenna array.

[0070] By simulating and observing the surface current of the microwave absorber unit at the highest frequency point of the absorption rate, it can be found that the periodic structure on the surface of the microwave absorber unit and the metal backplane have anti-phase currents. This will generate magnetic resonance in the dielectric, causing dielectric loss of energy. At the same time, it can be observed that the current density on the surface metal structure is much higher than that on the metal backplane, indicating that there is strong electrical resonance in the surface structure. The strong periodic changes in current cause ohmic losses through the loaded chip resistors, which is the coupled wave energy that needs to be utilized. Therefore, the designed microwave absorber unit is placed in the middle of the antenna array for wave absorption. At this time, the feed port is obviously the resistor position where the antenna array layout is most reasonable when the resistor is replaced by the antenna unit. To simplify the verification, a two-unit array is used, and the microwave absorber unit is placed between the two antenna units. The resistor position on the middle microwave absorber unit is the position that needs to be designed as the feed source.

[0071] S3. Based on the goal of utilizing the coupled electromagnetic waves absorbed by the microwave absorber unit for secondary radiation to improve the antenna array gain and adjust the input impedance, a radiator unit is designed.

[0072] The following indicators should be considered when designing radiator units: Miniaturization. Because the spacing between antenna array elements is generally 0.5 to 1 wavelength, radiator units that are too large would lack installation space. Return loss should be less than -10dB within the bandwidth, and the bandwidth should be close to the absorption bandwidth of the designed microwave absorber to fully utilize the coupled electromagnetic wave energy. Radiation performance. The polarization mode, gain, 3dB bandwidth, sidelobe suppression, and other indicators of the radiator unit should be as close as possible to the radiation performance of the antenna units in the applied antenna array; otherwise, the radiation performance of the antenna array may be degraded. Input impedance. Because the radiator unit is not fed via a conventional 50-ohm coaxial cable, the designed radiator needs to have an adjustable input impedance to match the input source.

[0073] S4. According to the output port of the microwave absorber unit and the impedance conjugate matching goal, a feeding network structure is designed.

[0074] S5. Based on the feeding network structure, the microwave absorber unit and the radiator unit are connected to obtain an antenna array decoupling structure based on coupled electromagnetic waves; the radiator unit is used to radiate the coupled electromagnetic waves absorbed by the microwave absorber to improve the radiation performance of the antenna array.

[0075] The antenna array decoupling structure based on coupled electromagnetic waves obtained by the design method of this embodiment is the same as the antenna array decoupling structure based on coupled electromagnetic waves described in the previous embodiment.

[0076] The final antenna array decoupling structure based on coupled electromagnetic waves designed by the method of this embodiment consists of two parts: a microwave absorber unit and a radiator unit. The microwave absorber unit is composed of a periodic circuit loaded with resistive elements processed on a first dielectric substrate and a metal backplane, while the radiator unit is a structure similar to a dipole. It adjusts the impedance matching by loading a ring structure on the edge of the radiating dipole, so that its input impedance can be effectively adjusted to match the resistive element on the replaced microwave absorber unit to achieve maximum power transmission. The solution of this embodiment utilizes the microwave absorber unit to absorb coupled electromagnetic waves between antenna units to improve isolation, and at the same time uses part of the absorbed energy to radiate through the radiator unit to improve the radiation performance of the antenna array. The design method proposed in this embodiment can be applied to the design of base station antenna arrays, which can improve the antenna radiation performance while improving isolation.

[0077] The technical features of the above embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0078] This document uses specific examples to illustrate the principles and implementation methods of this application. The description of the above examples is only intended to help understand the method and core concept of this application. At the same time, for those skilled in the art, based on the concept of this application, there may be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting this application.

Claims

1. An antenna array decoupling structure based on coupled electromagnetic waves, characterized in that: include: Microwave absorber unit and radiator unit; The microwave absorber unit is arranged between adjacent antenna units of the antenna array, and is used to absorb the coupled electromagnetic waves between adjacent antenna units, thereby reducing the coupling between adjacent antenna units of the antenna array; the input impedance of the radiator unit is adjustable; the radiator unit is connected to the microwave absorber unit through a feeding network structure, and is used to radiate the coupled electromagnetic waves absorbed by the microwave absorber, thereby improving the radiation performance of the antenna array; the output impedance of the microwave absorber unit is conjugate matched with the input impedance of the radiator unit.

2. The antenna array decoupling structure based on coupled electromagnetic waves according to claim 1, characterized in that: The microwave absorber unit comprises a first dielectric substrate, a periodic resistor structure and a metal backplate disposed on the top and bottom of the first dielectric substrate, respectively. The periodic resistor structure comprises a plurality of periodically distributed annular loops and chip resistors disposed on each of the annular loops. The chip resistors are used to adjust the input impedance of the microwave absorber and provide two output ports for subsequent radiation utilization by the radiator unit.

3. The antenna array decoupling structure based on coupled electromagnetic waves according to claim 2, characterized in that: The radiator unit includes: a second dielectric substrate and a pair of radiating dipoles, a pair of coupling feeding branches and a pair of input impedance adjustment metal rings arranged on the second dielectric substrate; the two coupling feeding branches are respectively connected to the two output ports on the microwave absorber unit through a feeding network structure to receive coupled electromagnetic waves, the radiating dipoles are used to radiate the received coupled electromagnetic waves, and the input impedance adjustment metal rings are used to adjust the input impedance of the radiator unit.

4. The antenna array decoupling structure based on coupled electromagnetic waves according to claim 3, characterized in that: The feeding network structure includes: a third dielectric substrate and a first feeding branch and a second feeding branch arranged on both sides of the third dielectric substrate; the third dielectric substrate is arranged between the microwave absorber unit and the radiator unit, and the third dielectric substrate is parallel to the first dielectric substrate and perpendicular to the second dielectric substrate; one end of the first feeding branch is connected to an output port on the microwave absorber unit, and the other end of the first feeding branch is connected to one of the coupling feeding branches on the radiator unit; one end of the second feeding branch is connected to another output port on the microwave absorber unit, and the other end of the second feeding branch is connected to another of the coupling feeding branches on the radiator unit.

5. The antenna array decoupling structure based on coupled electromagnetic waves according to claim 4, characterized in that: The first feeding branch includes a first metal via and a first metal microstrip; the second feeding branch includes a second metal via and a second metal microstrip; one surface of the third dielectric substrate and the metal backplane of the first dielectric substrate are mutually extended surfaces; One end of the first metal via is connected to an output port on the microwave absorber unit. The first metal via extends perpendicularly toward the metal backplate within the first dielectric substrate. The other end of the first metal via is connected to one end of a first metal microstrip perpendicular to the first metal via at a fixed interval from the metal backplate. The fixed interval is the thickness of the third dielectric substrate. The first metal microstrip extends in a direction perpendicular to the second dielectric substrate. The other end of the first metal microstrip is connected to one of the coupling feed branches on the radiator unit. One end of the second metal via is connected to another output port on the microwave absorber unit, the second metal via extends perpendicularly toward the metal backplate in the first dielectric substrate, and the other end of the second metal via passes through the first dielectric substrate and is connected to the metal backplate; one end of the second metal microstrip is connected to the metal backplate, the second metal microstrip extends in a direction perpendicular to the second dielectric substrate, and the other end of the second metal microstrip is connected to another coupling feed branch on the radiator unit.

6. The antenna array decoupling structure based on coupled electromagnetic waves according to claim 2, characterized in that: A single annular loop includes four square loops with missing corners at four corners, and the gaps between two adjacent square loops with missing corners are connected by a chip resistor; after one chip resistor located in the middle of the annular loop in the microwave absorber unit is removed, the free branches of the two adjacent square loops with missing corners form two output ports of the microwave absorber unit.

7. A design method for an antenna array decoupling structure based on coupled electromagnetic waves, characterized in that: include: Based on the frequency bandwidth of the coupled electromagnetic waves between adjacent antenna elements of the antenna array, a microwave absorber unit is designed; The microwave absorber unit is used to absorb the coupled electromagnetic waves between adjacent antenna units of the antenna array, thereby reducing the coupling between adjacent antenna units of the antenna array; Performing simulation analysis on the antenna array to determine the position of the microwave absorber unit in the antenna array and the output port of the microwave absorber unit; the microwave absorber unit is arranged between adjacent antenna units in the antenna array; Based on the goal of utilizing the coupled electromagnetic waves absorbed by the microwave absorber unit for secondary radiation to improve the antenna array gain and adjust the input impedance, a radiator unit is designed; According to the output port of the microwave absorber unit and the impedance conjugate matching target, a feeding network structure is designed; Based on the feeding network structure, the microwave absorber unit and the radiator unit are connected to obtain an antenna array decoupling structure based on coupled electromagnetic waves; The radiator unit is used to radiate the coupled electromagnetic waves absorbed by the microwave absorber, thereby improving the radiation performance of the antenna array.

8. The design method of the antenna array decoupling structure based on coupled electromagnetic waves according to claim 7, characterized in that: The microwave absorber unit comprises a first dielectric substrate, a periodic resistor structure and a metal backplate disposed on the top and bottom of the first dielectric substrate, respectively. The periodic resistor structure comprises a plurality of periodically distributed annular loops and chip resistors disposed on each of the annular loops. The chip resistors are used to adjust the input impedance of the microwave absorber and provide two output ports for subsequent radiation utilization by the radiator unit.

9. The design method of the antenna array decoupling structure based on coupled electromagnetic waves according to claim 8, characterized in that: The radiator unit includes: a second dielectric substrate and a pair of radiating dipoles, a pair of coupling feeding branches and a pair of input impedance adjustment metal rings arranged on the second dielectric substrate; the two coupling feeding branches are respectively connected to the two output ports on the microwave absorber unit through a feeding network structure to receive coupled electromagnetic waves, the radiating dipoles are used to radiate the received coupled electromagnetic waves, and the input impedance adjustment metal rings are used to adjust the input impedance of the radiator unit.

10. The design method of the antenna array decoupling structure based on coupled electromagnetic waves according to claim 9, characterized in that: The feeding network structure includes: a third dielectric substrate and a first feeding branch and a second feeding branch arranged on both sides of the third dielectric substrate; the third dielectric substrate is arranged between the microwave absorber unit and the radiator unit, and the third dielectric substrate is parallel to the first dielectric substrate and perpendicular to the second dielectric substrate; one end of the first feeding branch is connected to an output port on the microwave absorber unit, and the other end of the first feeding branch is connected to one of the coupling feeding branches on the radiator unit; one end of the second feeding branch is connected to another output port on the microwave absorber unit, and the other end of the second feeding branch is connected to another of the coupling feeding branches on the radiator unit.

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