An array antenna with high isolation

Abstract

The application discloses an array antenna with high isolation, which comprises a metal base plate, a layer of PCB plate and metal patches, three king-shaped rectangular slots are arranged at the center of the metal base plate, the PCB plate and the metal base plate are supported by nylon columns, the metal patches comprise triangular ring-shaped pair metal patches, stub rectangular patches and rhombic open-loop metal patches, the metal patches are attached to the upper surface of a dielectric substrate, the metal base plate and the PCB plate are connected together through coaxial lines to realize coaxial feeding, and the design of the triangular ring-shaped pair metal patches, the stub rectangular patches and the rhombic open-loop metal patches not only makes the antenna small in size and low in profile, but also has good isolation in the working frequency band, and the structure is simple, the array antenna can be manufactured by using a printed circuit process, and thus mass production is facilitated and production cost is effectively reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of mobile communication base station antennas, and particularly relates to an array antenna with high isolation. BACKGROUND

[0002] In a rich multipath environment, the channel capacity of a wireless communication system can be substantially increased by employing multiple-input multiple-output (MIMO) technology without requiring additional spectrum or power resources. Given these benefits, MIMO technology has attracted considerable attention in both academia and industry, and has been widely implemented in the latest wireless communication systems. However, in a size-constrained terminal or portable device, a closely spaced antenna element arrangement will result in high mutual coupling between the antenna elements. Wireless technology has brought new problems along with its development. It is well known that the close arrangement of two or more co-polarized antennas at the same frequency will result in strong mutual coupling between the antenna elements, thereby reducing the overall performance of the wireless system. In the past few decades, a large amount of research work has been done to improve the antenna isolation.

[0003] To solve the above technical problems, the first decoupling scheme is a decoupling network. It satisfies the dispersion parameters through mathematical operations, and designs a combination of matching networks at the circuit level to achieve decoupling. However, the circuit-level decoupling method cannot provide intuitive understanding of the antenna radiation performance, and may even cause the antenna radiation performance to deteriorate. The second decoupling technology is to block the surface current between the antenna elements through a band-stop structure, such as electromagnetic band gap (EBG), soft surface, etc., to reduce the coupling between the antennas. Although these antennas with the above decoupling structure can provide satisfactory improvement in isolation, they inevitably suffer from some drawbacks, such as complex structure, larger occupied area, and deteriorated radiation performance. The third decoupling method is to eliminate the original coupling by adding additional coupling paths with equal amplitude but different phase. The specific structure of this method has parasitic elements and self-decoupling units. Parasitic elements have the ability to perform coupling suppression between antenna elements through additional decoupling structures. Self-decoupling units reduce mutual coupling by carefully designed antenna units, rather than using additional decoupling structures. It has a clever antenna structure, but lacks systematic design guidelines, and is currently only in the trial stage.

[0004] However, through the above decoupling methods, such as adding EBG structures, soft surfaces between antennas, not only the size of the antenna is increased, but also the antenna structure becomes complex, the manufacturing difficulty is increased, and the production cost is increased, which is not suitable for large-scale production and promotion. SUMMARY

[0005] The present application provides an array antenna with high isolation degree based on microstrip antenna structure and structure design for reducing mutual coupling between antennas, which has good working performance, better isolation degree, simple structure, can be manufactured by printed circuit process, and is convenient for mass production and effectively reduces production cost.

[0006] To solve the above technical problems, the technical scheme of the present application is:

[0007] The array antenna with high isolation degree comprises a metal base plate, a PCB plate and a radiation patch, the radiation patch is attached to the upper surface of the PCB plate, the metal base plate and the PCB plate are connected together by a coaxial line to realize coaxial feeding, the radiation patch comprises a plurality of unit antennas arranged in sequence, each unit antenna comprises left and right radiation patches arranged in a symmetrical structure, the left and right radiation patches are triangular structures, the opposite sides of the left and right radiation patches are connected by two short stub rectangular patches, two symmetrical diamond open-loop metal patches are arranged between adjacent two unit antennas, three king-shaped rectangular slots are arranged at the middle position of the metal base plate and are denoted as gap1, gap2 and gap3 respectively, and the three king-shaped rectangular slots, the short stub rectangular patches and the diamond open-loop metal patches jointly form a decoupling structure.

[0008] Preferably, the distance between the two adjacent unit antennas is 4mm.

[0009] Preferably, the opposite sides of the left and right radiation patches in the unit antenna are provided with triangular notches in a symmetrical structure.

[0010] Preferably, the left and right radiation patches are isosceles right triangles.

[0011] Preferably, the triangular notches and the corresponding left and right radiation patches are similar triangles.

[0012] Preferably, a plurality of first through holes arranged in a line are arranged at the middle position of the PCB plate, a plurality of second through holes arranged in a line are arranged at the middle position of the metal base plate, the first and second through holes correspond to each other in pairs from top to bottom, and the first and second through holes are connected by a coaxial line.

[0013] Preferably, upper opening grooves are arranged at the four corner ends of the PCB plate, lower opening grooves are arranged at the four corner ends of the metal base plate corresponding to the upper opening grooves, nylon columns are arranged between the upper and lower opening grooves, and the PCB plate is fixed above the metal base plate by the nylon columns.

[0014] The present application has the following characteristics and beneficial effects:

[0015] With the technical scheme, first, a unit in the array antenna has a small triangle dug in a large triangle patch, and adopts a symmetrical structure, and the antennas have a certain distance, and the antennas can be well matched by adjusting the distance; the two symmetrical antennas are respectively fed, and coaxial feeding is used to achieve good impedance matching;

[0016] Second, based on the principle of reducing mutual coupling between antennas, a rhombic open-loop metal patch is added between the antennas to effectively suppress the current between the antennas to reduce the mutual coupling between the antennas, the rhombic open-loop metal patch is provided with symmetrical dipole arms, and the working frequency and isolation between the antennas can be adjusted by adjusting the length of the dipole arms, and the working frequency and isolation are well matched;

[0017] Third, a short stub rectangular patch is introduced between the triangular loop symmetrical antennas, which is equivalent to introducing an impedance, which can effectively change the odd and even modes between the antennas, and when the resonant frequencies and quality factors of the two modes become equal, high isolation is achieved. The structure is effective and simple;

[0018] Fourth, a defective floor structure is used to reduce the strong coupling between the antennas and improve the isolation between the antennas. The Wang-shaped rectangular slot can reduce the current flow between the antennas. By adjusting the length of each rectangular ground, the current can be effectively suppressed, and good impedance matching can also be achieved;

[0019] Fifth, the structure of the present application is simple, and is made by printed circuit technology, which is convenient for mass production, easy to assemble and use, and easy to popularize. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0021] Figure 1 The structure schematic diagram of the embodiment of the present application;

[0022] Figure 2 The structure schematic diagram of the PCB board in the embodiment of the present application;

[0023] Figure 3 The structure schematic diagram of the metal bottom plate in the embodiment of the present application;

[0024] Figure 4 The structure schematic diagram of the Wang-shaped rectangular slot in the embodiment of the present application; Figure 3 ​

[0025] Figure 5 for Figure 1 Schematic diagram of the structure of the middle unit antenna;

[0026] Figure 6 This is a side view diagram in an embodiment of the present invention;

[0027] Figure 7 This is a schematic diagram of the radiation patch structure in an embodiment of the present invention;

[0028] Figure 8 The simulation results of the original single antenna return loss (S11) of this invention are shown.

[0029] Figure 9 This is the simulation result of the original single antenna port isolation (S21) of the present invention;

[0030] Figure 10 The simulation results are for the return loss (S11) of adding a stub rectangular patch between individual antennas in this invention;

[0031] Figure 11 The simulation results show the port isolation (S21) of the single antenna with a stub rectangular patch in this invention.

[0032] Figure 12 The simulation results show the return loss (S11) at each port of the array antenna of this invention.

[0033] Figure 13 This is the simulation result of the isolation (S21) between closely spaced ports in the array antenna of the present invention.

[0034] In the diagram, 1-radiating patch; 2-PCB board; 12-first through hole; 13-second through hole; 3-metal base plate; gap1, gap2, gap3-king-shaped rectangular slots; 7-left radiating patch; 8-right radiating patch; 9-short-cut rectangular patch; 10-diamond-shaped open-loop metal patch; 11-coaxial cable. Detailed Implementation

[0035] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0036] In the description of the present application, it needs to be understood that the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second" and the like are only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second" and the like can be explicitly or implicitly included one or more. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0037] In the description of the present application, it needs to be understood that unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting" should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood through specific circumstances.

[0038] The present application provides an array antenna with high isolation, as shown in Figure 1 The metal base plate 3 is provided with three king-shaped rectangular slots gap1, gap2 and gap3 at the center, the radiation patch 1 includes triangular ring-shaped radiation patch 7, 8, short stub rectangular patch 9 and diamond open-loop metal patch 10, the radiation patch is attached to the upper surface of the PCB board 2, and the metal base plate and the PCB board are connected together through the coaxial line 11 to realize coaxial feeding.

[0039] Further, as shown in Figure 2 And Figure 3 The coaxial line 11 connects the PCB board 2 and the metal base plate 3 through the first through hole 12 opened on the PCB board 2 and the second through hole 13 opened on the metal base plate 3. The nylon column supports the PCB board 2 and the metal base plate 3 by the upper opening groove opened on the four corners of the PCB board 2 and the lower opening groove opened on the four corners of the metal base plate 3.

[0040] Specifically, the diameter of the first and second through holes is 1mm, the coaxial cable inner layer conductive copper wire passes through the through hole, and is connected with the radiating antenna through soldering. The diameter of the lower opening groove on the four corners of the metal bottom plate and the upper opening groove on the PCB plate is 2mm, and the antenna structure is supported by the nylon column.

[0041] In the technical solution, a small triangle is cut out on the right radiation patch 8 and the left radiation patch 7 of each antenna of the array antenna, and the right radiation patch 8 and the left radiation patch 7 are arranged in a symmetrical structure. There is a short stub rectangular patch 9 between the left and right radiation patches. The short stub rectangular patch 9 is not folded and has a simple structure.

[0042] Specifically, the overall length K4 of the left and right radiation patches 7 and 8 is 84mm, the hypotenuse length K3 is 56.6mm, the overall length K8 of the cut-out small triangle structure is 26mm, the hypotenuse length K9 is 16.4mm, the length K1 of the short stub rectangular patch structure is 8mm, and the width K2 is 1mm. It can be understood that the impedance matching and isolation of the antenna can be adjusted by adjusting the width of the rectangular radiation patch.

[0043] It can be conceived that when the array antennas are relatively close, the influence between them is very large. Therefore, it is necessary to reduce the coupling between them. By adding symmetrical diamond open-loop metal sheets between the antennas, the isolation can be improved. Compared with the ordinary open-loop structure, the diamond open-loop metal sheet has a vibrator arm, and by adjusting the length of the vibrator arm, good impedance matching can be achieved, and the isolation of the antenna can be improved. The hypotenuse length K7 is 24mm, and the final vibrator arm length K6 is 11.1mm, and the width K5 is 2.5mm.

[0044] Specifically, the specifications of the PCB substrate 2 and the metal bottom plate 3 are the same, the length is 390mm, and the width is 200mm; the relative dielectric constant of the PCB plate is ε r =4.4, the tangent of the dielectric loss angle is 0.02, and the relative permeability is 1.

[0045] It can be understood that the metal bottom plate 3 is designed with a metal material. When the antenna is excited, the metal bottom plate 3 can reflect electromagnetic waves and produce radiation, thereby increasing the bandwidth and enhancing the directivity of the antenna.

[0046] Further settings of the application are shown in the following table: Figure 3 The defect floor structure is used to reduce the strong coupling between the antennas and improve the isolation between the antennas. The rectangular slot in the shape of a Chinese character can reduce the current between the antennas. By adjusting the length of each rectangular floor, the current can be effectively suppressed, and good impedance matching can be achieved.

[0047] Specifically, as shown in the following table: Figure 4As shown, the king-shaped rectangular slot is formed by 5 transverse rectangular slots and 1 longitudinal rectangular slot, the longitudinal rectangular slot extends from the middle position of the highest transverse rectangular slot to the middle position of the lowest transverse rectangular slot.

[0048] In the figure, the overall width of the slot is 92mm, the length of the shorter rectangular slot is 30mm, the length of the second longer rectangular slot is 36.6mm, and the length of the longest rectangular slot is 40mm, and the width of the rectangular slot is 4mm.

[0049] It can be understood that the stub structure is similar to an inductor, which can adjust the isolation between antennas by changing the odd mode between antennas, in order to achieve enhanced isolation, the resonant frequencies of the two modes should be first tuned to be equal. Since the two patches are capacitively coupled, an inductive load should be introduced. Therefore, two stubs equivalent to small inductors are loaded between the triangular loop radiation patches. The equivalent inductance of the two strips is determined by their length and width, and the loading effect is related to their position.

[0050] It should be noted that, as Figure 7 As shown, the diamond-shaped open-loop metal patch 10 is in a diamond-shaped frame structure, and it lacks one corner end, and two edges of the diamond-shaped open-loop metal patch 10 are tangent to the edges of the left and right radiation patches of the adjacent two unit antennas.

[0051] It can be understood that through the diamond-shaped open-loop structure, the mutual coupling between the radiation antennas can be effectively reduced, which is designed as a band-stop filter at the antenna resonant frequency. The length of the oscillator arm can be adjusted to achieve good matching.

[0052] It can be understood that designing a defective ground structure on the ground plane between multiple antennas has been widely verified as an effective method to suppress floor surface waves and reduce mutual coupling. By designing a single or periodic slot or groove on the ground plane, i.e. constructing a defective ground structure, a stopband characteristic is achieved in a certain frequency band, thereby effectively suppressing surface currents and reducing coupling. The defective ground structure can be regarded as a band-stop filter for coupling surface currents, which can suppress the flow of coupling currents from the source antenna port to the coupled antenna port in the set frequency band, thereby achieving the effect of reducing the coupling between antenna elements.

[0053] According to the technical solutions described in the above embodiments, the results obtained by the ANSYS HFSS simulation software are comprehensively utilized to further elaborate and illustrate the technical effects of the present application.

[0054] As Figure 8As shown in the figure, the S11 of the original single antenna in this embodiment is less than -10dB in the operating frequency band range of 3.01-3.12GHz.

[0055] As shown in the figure, the S21 of the original single antenna in this embodiment is about -15.7dB to -18dB in the operating frequency band range of 3.01-3.12GHz. Figure 9

[0056] As shown in the figure, the S11 of the single antenna with a short stub rectangular patch in this embodiment is less than -10dB in the operating frequency band range of 3.07-3.14GHz; this indicates that the performance of the antenna with a short stub rectangular metal patch does not change much, and the impedance matching is also good. Figure 10

[0057] As shown in the figure, the S21 of the single antenna with a short stub rectangular patch in this embodiment is about -28dB to -44dB in the operating frequency band range of 3.07-3.14GHz, and the best isolation has reached -44dB, which indicates that adding a short stub rectangular patch between the antennas can effectively reduce the mutual influence between the antennas and improve the isolation. Figure 11

[0058] As shown in the figure, the S11 of the array antenna with closely spaced ports in this embodiment is less than -10dB in the operating frequency band range of 3.06-3.18GHz. Figure 12

[0059] As shown in the figure, after adding a diamond open-loop metal patch and a metal bottom plate slot between the antennas in this embodiment, the isolation between the ports with a distance of 4mm is less than 16dB in the operating frequency band range of 3.06GHz-3.18GHz, and the highest isolation is -26dB, which is improved by nearly 20dB compared with the isolation without adding the decoupling structure. Figure 13

[0060] As shown in the figure, the S11 of the original single antenna in this embodiment is less than -10dB in the operating frequency band range of 3.01-3.12GHz. Figure 8 Figure 12 Figure 9 Figure 11 Figure 13 After adding a short stub rectangular patch and a decoupling structure to the antenna, the operating frequency band of the antenna does not change much, indicating that the impedance matching is good. Moreover, the isolation of the closely spaced ports is obviously improved after adding the decoupling structure. In general, the matching between the ports of the array antenna is good, and the isolation is high.

[0061] ​​​​​​​​​The embodiments of the present application are described in detail above with reference to the accompanying drawings, but the present application is not limited to the described embodiments. Various changes, modifications, replacements, and variations of the embodiments including components can be made by those skilled in the art without departing from the principles and spirit of the present application, and still fall within the scope of the present application.

Claims

1. An array antenna with high isolation, characterized in that, The system includes a metal base plate (3), a PCB board (2), and a radiating patch (1). The radiating patch (1) is attached to the top of the PCB board (2). The metal base plate (3) and the PCB board (2) are connected together via a coaxial cable (11) to achieve coaxial feeding. The radiating patch (1) comprises several unit antennas arranged sequentially. Each unit antenna includes a left radiating patch (7) and a right radiating patch (8) arranged in a symmetrical structure. Both the left radiating patch (7) and the right radiating patch (8) are triangular structures. The opposite sides of the left radiating patch (7) and the right radiating patch (8) are connected via... Two short-stub rectangular patches (9) are connected together. Two rhomboid open-loop metal patches (10) with symmetrical structure are provided between two adjacent unit antennas. The two sides of the rhomboid open-loop metal patch (10) are respectively tangent to the sides of the left radiating patch (7) and the right radiating patch (8) in the two adjacent unit antennas. Three king-shaped rectangular slots are provided in the middle of the metal base plate (3), which are respectively called gap1, gap2 and gap3. The three king-shaped rectangular slots, the short-stub rectangular patches (9) and the rhomboid open-loop metal patches (10) together constitute a decoupling structure.

2. The array antenna with high isolation according to claim 1, characterized in that, The distance between two adjacent unit antennas is 4mm.

3. The array antenna with high isolation according to claim 1, characterized in that, The left radiating patch (7) and right radiating patch (8) of the unit antenna have triangular notches arranged in a symmetrical structure on opposite sides.

4. The array antenna with high isolation according to claim 3, characterized in that, Both the left radiating patch (7) and the right radiating patch (8) are isosceles right triangles.

5. An array antenna with high isolation according to claim 4, characterized in that, The notch in the triangle is similar to the corresponding left and right radiating patches (7 and 8).

6. An array antenna with high isolation according to claim 1, characterized in that, The PCB board (2) has a number of first through holes (12) arranged in a line in the middle position, and the metal base plate (3) has a number of second through holes (13) arranged in a line in the middle position. The first through holes (12) and the second through holes (13) are opposite each other in the upper and lower positions, and the first through holes (12) and the second through holes (13) are connected by a coaxial line (11).

7. An array antenna with high isolation according to claim 6, characterized in that, The PCB board (2) has upper opening slots at its four corners, and the metal base plate (3) has lower opening slots at its four corners corresponding to the upper opening slots. Nylon pillars are provided between the upper and lower opening slots, and the PCB board (2) is fixed above the metal base plate (3) by the nylon pillars.

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