EBG decoupling structure shape and layout collaborative optimization method of array antenna

Abstract

The application discloses an EBG decoupling structure shape and layout collaborative optimization method of an array antenna, and belongs to the field of wireless communication antennas. The designed non-uniform curve EBG decoupling structure can significantly improve the mutual coupling effect between array antenna elements, is compact in structure, easy to process, and suitable for high-frequency and high miniaturization degree array antennas. The structure form is realized by proposing an EBG decoupling structure shape and layout collaborative optimization design method. By collaboratively optimizing the Bezier curve control point coordinates and the strip spacing of the strip-shaped EBG decoupling structure, the interference of the surface wave can be effectively suppressed, and the isolation between the elements can be improved. The shape and layout collaborative optimization design method provided by the application is suitable for antenna arrays of multiple frequency bands and has strong expandability. By designing the shape and layout parameters of the EBG decoupling structure, the decoupling performance of the array antenna can be greatly improved, and meanwhile, the radiation performance of the array antenna under a specific frequency band is ensured.

Description

TECHNICAL FIELD

[0001] The application discloses a shape and layout collaborative optimization method for an electromagnetic band gap (EBG) decoupling structure of an array antenna, and belongs to the field of wireless communication antennas. BACKGROUND

[0002] With the development of wireless communication technology, multiple input multiple output (MIMO) technology is widely used in array antenna systems to improve the capacity and communication ability of communication systems. However, the space in wireless communication devices is limited, and placing a large array antenna system inevitably leads to a smaller spacing between antenna units, and thus the mutual interference between array elements is strengthened, making it difficult for wireless communication devices to achieve the expected working effect. Therefore, how to reduce the mutual coupling effect between array elements in the MIMO array antenna system and suppress the interference of surface waves has become a key problem to be solved at present.

[0003] To solve the above problems, researchers have proposed different methods to design decoupling structures to improve the isolation between units. The decoupling methods of MIMO array antennas mainly include resonant line / ring structures, defective ground structures (DGS) and electromagnetic band gap (EBG) structures. Among them, the DGS decoupling structure changes the direction of the coupled current to make the array antenna produce a spatial band-stop effect, thereby improving the isolation between array elements. For example, the document“A Novel Slot-Array Defected Ground Structure for Decoupling Microstrip Antenna Array”uses a designed DGS to make the isolation between circularly polarized antenna units about-50dB. However, although DGS has a significant effect on suppressing the mutual coupling of antenna arrays, it will also cause unnecessary back radiation of the array antenna, resulting in problems such as excessive energy of the array antenna back lobe. EBG is a kind of artificial electromagnetic material, and its unique surface wave band gap characteristic can suppress the propagation of surface waves, thereby achieving the purpose of suppressing antenna mutual coupling. For example, the patent (CN110112577A) proposes a mushroom-type EBG decoupling structure for improving the isolation of a compact dual-polarized MIMO antenna. Although EBG structure does not produce back radiation compared with DGS, there are still problems of complex decoupling structure, large size and single design means. Therefore, in order to meet the design requirements of EBG decoupling structure, it is of great significance to design an EBG structure with compact structure and good decoupling performance, and to study an optimization design method suitable for antenna arrays of multiple frequency bands and with strong expandability. SUMMARY

[0004] In order to solve the problems in the prior art, the application provides an EBG decoupling structure shape and layout collaborative optimization method for an array antenna, which obtains a non-uniform curve EBG decoupling structure by collaboratively optimizing the Bezier curve control point coordinates and curve strip spacing, significantly improves the decoupling performance of the array antenna, and ensures the radiation performance of the array antenna in the WLAN frequency band.

[0005] In order to achieve the above-mentioned purpose, the technical means adopted by the application is as follows:

[0006] An EBG decoupling structure shape and layout collaborative optimization method for an array antenna, comprising the following steps:

[0007] Step 1: design a symmetrical straight line EBG decoupling structure: determine the size parameters of the straight line EBG decoupling structure according to the required frequency band and the array antenna configuration, the size parameters including the straight line strip length L d , the width W d and the strip spacing d T ;

[0008] The specific method is: through the parametric analysis method, the size and initial strip spacing of the straight line EBG decoupling structure between the rectangular patch units of the array antenna are specifically designed.

[0009] Step 2: determine the curve shape of the non-uniform curve EBG decoupling structure;

[0010] The shape of the curve EBG decoupling structure is described by a Bezier curve:

[0011] The specific method is: according to the size and initial strip spacing of the symmetrical straight line EBG decoupling structure in step 1, the shape of the curve EBG decoupling structure is designed by a Bezier curve, and the width of the curve EBG decoupling structure is always W d , the Bezier curve expression for describing the decoupling structure shape is:

[0012]

[0013] Wherein, (x i ,y i ) is the control point coordinates, that is, the control parameters of the Bezier curve, i={0,1,Ln}, t is a time variable, t∈[0,1], n is the order, the number of control points is determined according to the required n, and the value range of the control point (x i ,y i ) is determined according to the design domain S.

[0014] Step 3: introduce a layout parameter;

[0015] The specific method is: according to the Bezier curve expression of the second step, the layout parameter is introduced, and the designed curve EBG decoupling structure is limited in the S area, and the specific form is:

[0016]

[0017] Wherein, d is the layout parameter, indicating the inside distance of the curve strip, according to the range of design domain S and the width W of the curve strip d To determine the value range of d.

[0018] The fourth step is to set the Bezier curve control point coordinates (x i ,y i ) and the layout parameter d, and to establish the shape and layout collaborative optimization design model of the EBG decoupling structure;

[0019] The specific method is: according to the shape and layout parameterization model proposed in the second step and the third step, setting the Bezier curve control point coordinates (x i ,y i ) and the layout parameter d, proposing the optimization problem of non-uniform curve EBG decoupling structure, defining the optimization problem as: through optimizing the curve control point coordinates (x i ,y i ) and the layout parameter d in the array antenna EBG decoupling structure, while ensuring that the array antenna works normally in the required frequency band (i.e. the reflection coefficient S 11 is less than -10dB), the isolation correlation coefficient S 21 of the array antenna is minimized, wherein S 11 represents the radiation performance of the array antenna, and S 21 represents the decoupling performance of the array antenna. Based on the optimization problem, the optimization formula for solving the non-uniform curve EBG decoupling structure design problem is given as:

[0020]

[0021] Wherein, Φ is the fitness function, Z is the characteristic impedance matrix, J is the surface current to be solved, V is the excitation voltage, and α, β are the weight factors of S 11 and S 21 , the value range of the control point horizontal and vertical coordinates is The value range of d is [d min , d max ], thus the shape and layout collaborative optimization design model of the EBG decoupling structure is established.

[0022] The fifth step is to solve the collaborative optimization design model in the fourth step, and obtain the optimal solution of the control point coordinates (x i ,y i ) and the layout parameter d.

[0023] The specific method is: parameterized modeling is carried out by means of High Frequency Structure Simulator (HFSS) electromagnetic simulation software, simulation analysis is completed, each performance index of the array antenna is calculated, the fitness function in the above optimization formula is obtained, the established optimization model is iteratively solved by using a genetic algorithm (Genetic Algorithm), and finally the optimal solution of the control point coordinates (x i ,y i ) and the layout parameter d is obtained, and the performance requirement of the array antenna in the required frequency band is realized.

[0024] The non-uniform curve EBG decoupling structure is arranged between the array antenna elements, is symmetrically distributed about the x axis, and is beneficial to improving the decoupling performance of the array antenna.

[0025] The array antenna designed according to the EBG decoupling structure shape and layout collaborative optimization method comprises: M rectangular patch units in the upper layer, a non-uniform curve EBG decoupling structure, an RO4350B dielectric substrate in the middle layer, a ground plate in the lower layer, M microstrip line feeding ports and M microstrip transmission lines, and the microstrip feeding ports are respectively connected with the ground plate and the microstrip transmission lines at both ends.

[0026] The M rectangular patches are respectively connected with the M microstrip transmission lines, each group of rectangular patch units and the microstrip transmission lines thereof are symmetrically arranged along the central axis in sequence, and a spacing is arranged between groups.

[0027] The array antenna with the non-uniform curve EBG decoupling structure designed in the application not only can normally work in the WLAN frequency band, has good element isolation, but also effectively reduces the mutual coupling effect of the array antenna and suppresses the interference of the surface wave.

[0028] 1) The array antenna with the non-uniform curve EBG decoupling structure designed in the application not only can normally work in the WLAN frequency band, has good element isolation, but also effectively reduces the mutual coupling effect of the array antenna and suppresses the interference of the surface wave.

[0029] 2) The non-uniform curve EBG decoupling structure designed in the application has a simple, compact and small overall structure, is easy to process and manufacture, and can be placed between two adjacent antennas.

[0030] 3) The EBG decoupling structure shape and layout collaborative optimization method established in the application significantly improves the decoupling performance of the array antenna by collaboratively optimizing the Bezier curve control point coordinates and the strip spacing, while ensuring that the antenna radiation performance is almost unchanged.

[0031] 4) The EBG decoupling structure shape and layout collaborative optimization method of the array antenna established by the application has wide application range, strong practicability and expandability, widens the design field of the EBG decoupling structure, and improves the design capability of the decoupling structure in the field. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a three-dimensional schematic view of the array antenna with the non-uniform curve EBG decoupling structure in the specific embodiment of the application.

[0033] Figure 2 It is a top view and side view of the array antenna with the non-uniform curve EBG decoupling structure in the specific embodiment of the application.

[0034] Figure 3 It is a schematic view of the non-uniform curve EBG decoupling structure in the specific embodiment of the application.

[0035] Figure 4 It is a comparison chart of the S parameters of the array antenna without the decoupling structure and the array antenna with the non-uniform curve EBG decoupling structure in the specific embodiment of the application.

[0036] Figure 5 It is a comparison chart of the envelope correlation coefficient (ECC) of the array antenna without the decoupling structure and the array antenna with the non-uniform curve EBG decoupling structure in the specific embodiment of the application.

[0037] Figure 6 It is a surface current distribution chart of the array antenna without the decoupling structure and the array antenna with the non-uniform curve EBG decoupling structure working at 5.25 GHz in the specific embodiment of the application.

[0038] In the figure: 1, rectangular microstrip patch; 2, curve EBG decoupling structure; 3, RO4350B dielectric substrate; 4, ground plate; 5, microstrip feed port; 6, microstrip transmission line. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the application clearer, the application will be further described in detail below in combination with the drawings and specific embodiments.

[0040] Embodiment 1:

[0041] As Figure 1 , Figure 2 and Figure 3As shown, a MIMO array antenna with a non-uniform curved EBG decoupling structure for WLAN frequency band has an operating frequency band of 5.15 GHz to 5.35 GHz and a microstrip line feeding mode. The MIMO array antenna structure includes: two rectangular microstrip patches 1 on the upper layer, a curved EBG decoupling structure 2, a microstrip transmission line 6, an RO4350B dielectric substrate 3 in the middle layer, a ground plate 4 on the lower layer, and two microstrip feeding ports 5.

[0042] The two ends of the microstrip feeding port 5 are respectively connected to the ground plate 4 and the microstrip transmission line 6. Each rectangular microstrip patch 1 is connected to the microstrip transmission line 6. Each group of rectangular microstrip patch 1 units and their microstrip transmission line 6 are arranged symmetrically along the central axis, and there is a spacing between the groups; the microstrip feeding ports 5 are arranged in sequence, and the excitation voltage is fed through the microstrip feeding port 5.

[0043] According to the design requirements of the frequency band, the basic dimensions of the MIMO array antenna are: the length L of the rectangular microstrip patch 1 is 17.96 mm, the width W is 14.56 mm, the patches on the left and right sides are symmetrically distributed about the x-axis, and the length L of the dielectric substrate 3 is sub 47mm, width W sub The length and width of the ground plate 4 are the same as those of the dielectric substrate 3.

[0044] Example 2:

[0045] In accordance with Embodiment 1 of the present invention, the method for collaboratively optimizing the shape and layout of an EBG decoupling structure includes the following steps:

[0046] 1) Design the basic dimensions of the symmetrical straight line EBG decoupling structure (length L d and width W d ) and the strip spacing d T The specific method is: Figure 3 The dotted line shows the two-dimensional schematic diagram of the linear EBG decoupling structure of the MIMO array antenna for the WLAN frequency band. The length of the linear EBG along the positive direction of the x-axis is L. d 18.72mm, thickness W d is 0.55mm, the strip spacing d T The linear EBG decoupling structure is symmetrically distributed about x.

[0047] 2) Determine the curve shape of the non-uniform curved EBG decoupling structure 2. The shape of the curved EBG decoupling structure 2 is described by a Bezier curve. The specific method is: according to the size of the straight EBG decoupling structure, the shape of the curved EBG decoupling structure 2 is designed by the Bezier curve, and the width of the curved EBG decoupling structure is always W. d , its Bezier curve expression is:

[0048]

[0049] Among them, (x i ,y i ) is the coordinate of the control point, i.e., the control parameter of the Bezier curve, i = {0, 1, Ln}, t is the time variable, t∈[0, 1], n is the order, and the number of control points is determined according to the required n; the control points (x i ,y i ) value range. Figure 3 The figure shows a schematic diagram of the non-uniform curve EBG decoupling structure. According to the design accuracy and actual calculation amount of the embodiment of the present invention, the order of the Bezier curve is determined to be 4, the number of control points is 5, and the coordinates of the control points (x i ,y i ) is calculated in the range of x i ∈[0,18.72], y i ∈[0,5].

[0050] 3) Introducing layout parameters. The specific method is: according to the Bezier curve formula in the second step, the layout parameters are introduced into it, and the designed curve EBG decoupling structure is restricted to the S area. The specific function expression is:

[0051]

[0052] Where d is a layout parameter with a calculation range of [0, 4.8]. This allows the High Frequency Structure Simulator (HFSS) electromagnetic simulation software to implement parametric modeling of a MIMO array antenna with a curved EBG decoupling structure.

[0053] 4) Establish a non-uniform curve EBG decoupling structure shape and layout collaborative optimization design model. The specific method is:

[0054] The optimization problem of non-uniform curve EBG decoupling structure is defined as: by optimizing the coordinates of the curve control points (x i ,y i ) and layout parameters d, while ensuring that the array antenna works normally within the required frequency band (i.e., the reflection coefficient S 11 Less than -10dB), while minimizing the isolation correlation coefficient S of its array antenna 21 , where S 11 Indicates the radiation performance of the array antenna, S 21 represents the decoupling performance of the array antenna. Based on the proposed optimization problem, the optimization formula for solving the non-uniform curve EBG decoupling structure design problem can be given as:

[0055]

[0056] Wherein, the weight factor α, β are all 0.5, the value range of design variable x i , y i , d are given, thus the EBG decoupling structure shape and layout collaborative optimization design model is established.

[0057] 5) The collaborative optimization design model is solved to obtain the optimal solution of control point coordinates (x i , y i ) and layout parameter d, and the specific method is: parameterized modeling is carried out by means of High Frequency Structure Simulator (HFSS) electromagnetic simulation software, and simulation analysis is completed, each performance index of the array antenna is calculated, the fitness function in the above optimization formula is obtained, the optimization model established is iteratively solved by means of Genetic Algorithm (Genetic Algorithm), and finally the optimal control point coordinates are (0, 0), (8.162, 0.786),

[0058] (10.829, -3.958), (13.469, 3.155), (18.720, 0), and the layout parameter is 1.64, and the non-uniform curve EBG decoupling structure calculated therefrom is shown in Figure 3 .

[0059] In order to characterize the radiation performance and decoupling performance of the MIMO array antenna with the non-uniform curve EBG decoupling structure in the embodiment of the application and verify the effectiveness of the design method, the S parameters of the array antenna without the decoupling structure and the array antenna with the non-uniform curve EBG decoupling structure are calculated, including S 11 and S 21 . As shown in Figure 4 , the S 11 and S 21 performance comparison chart of the array antenna without the decoupling structure and the array antenna with the non-uniform curve EBG decoupling structure, it can be seen from the chart that both meet the design requirements of the WLAN working frequency band (5.15GHz-5.35GHz) and have good radiation performance, and the center frequency point is at 5.25GHz, the S 21 of the MIMO array antenna without the decoupling structure is -13.35dB, which indicates that there is serious mutual coupling between the array antenna elements, and also indicates the necessity of the decoupling structure design. The S 21The minimum is -35.16dB, compared with the array antenna without the decoupling structure, the curve EBG decoupling structure of the array antenna is significantly suppressed by 21.81dB of mutual coupling, effectively verifying the effectiveness of the established non-uniform curve EBG decoupling structure shape and layout collaborative optimization design method in the embodiment of the application.

[0060] As Figure 5 The ECC comparison chart of the MIMO array antenna without the decoupling structure and with the non-uniform curve EBG decoupling structure in the embodiment of the application is shown, from the chart, it can be seen that the correlation between the array antenna elements before and after applying the EBG decoupling structure becomes lower, ensuring the MIMO performance of the array antenna after applying the EBG decoupling structure. Figure 6 The surface current distribution chart of the MIMO array antenna without the decoupling structure and with the non-uniform curve EBG decoupling structure in the embodiment of the application at 5.25GHz is shown, by comparing the surface current distribution before and after applying the EBG decoupling structure, it can be seen that the proposed optimization method can significantly suppress the interference of surface waves and effectively improve the isolation between the array antenna elements.

[0061] The embodiment of the application relates to an EBG decoupling structure shape and layout collaborative optimization method of an array antenna. The MIMO array antenna meets the radiation performance of a WLAN frequency band, array elements are symmetrically distributed about an x axis and have non-uniform curve EBG decoupling structures between the array elements, the structure form is realized by proposing an EBG decoupling structure shape and layout collaborative optimization method, the interference of surface waves is effectively suppressed and the isolation between the array elements is improved by collaboratively optimizing the Bezier curve control point coordinates of the strip-shaped EBG decoupling structure and the strip spacing. The shape and layout parameters of the EBG decoupling structure are designed by the established collaborative design method, so that the radiation performance of the MIMO array antenna is realized and the decoupling performance of the array antenna is improved.

[0062] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A method for collaboratively optimizing the shape and layout of an EBG decoupling structure of an array antenna, characterized in that: The following steps are involved: Step 1: Design a symmetrical linear EBG decoupling structure: Determine the size parameters of the linear EBG decoupling structure based on the required frequency band and array antenna configuration. The size parameters include the linear length L. d , width W d and strip spacing d T ; Step 2: Determine the curve shape of the non-uniform curve EBG decoupling structure (2); The shape of the curved EBG decoupling structure (2) is described by a Bezier curve: The specific method is: according to the size parameters of the symmetrical straight line EBG decoupling structure in the first step, the shape of the curved EBG decoupling structure (2) is designed by the Bezier curve, and the width of the curved EBG decoupling structure is always W. d , the Bezier curve expression describing the shape of the decoupling structure is: Among them, (x i ,y i ) are the coordinates of the control points, i.e., the control parameters of the Bezier curve, i = {0, 1, ... n}, t is the time variable, t∈[0, 1], n is the order, the number of control points is determined according to the required n, and the control points (x i ,y i ) value range; Step 3: Introduce layout parameters; The specific method is: according to the Bezier curve expression in the second step, the layout parameters are introduced into it, and the designed curve EBG decoupling structure is restricted to the S area. The specific form is: Where d is the layout parameter, which represents the inner spacing of the curve bar, and is calculated based on the range of the design domain S and the width W of the curve bar. d To determine the value range of d; Step 4: Set the coordinates of the Bezier curve control points (x i ,y i ) and layout parameter d, and establish a collaborative optimization design model of EBG decoupling structure shape and layout; Step 5: Solve the collaborative optimization design model in step 4 and obtain the coordinates of the control points (x i ,y i ) and the optimal solution of the layout parameter d.

2. The shape and layout collaborative optimization design method of the EBG decoupling structure according to claim 1, characterized in that: The specific method of the fourth step is: According to the shape and layout parameterized model proposed in the second and third steps, the coordinates of the control points of the Bezier curve (x i ,y i ) and layout parameter d, the non-uniform curve EBG decoupling structure optimization problem is proposed, and the optimization problem is defined as: by optimizing the coordinates of the curve control points (x i ,y i ) and layout parameter d, while ensuring that the array antenna operates normally within the required frequency band, the isolation correlation coefficient S of the array antenna is minimized. 21 , where S 11 Indicates the radiation performance of the array antenna, S 21 represents the decoupling performance of the array antenna; based on the proposed optimization problem, the optimization formula for solving the non-uniform curve EBG decoupling structure design problem can be given as: Among them, Φ is the fitness function, Z is the characteristic impedance matrix, J is the surface current to be calculated, V is the excitation voltage, α, β are the control S 11 and S 21 The weight factor of the control point is The value range of d is [d min ,d max ], and thus establish a collaborative optimization design model of EBG decoupling structure shape and layout.

3. The shape and layout collaborative optimization design method of the EBG decoupling structure according to claim 1 or 2, characterized in that: The specific method of the fifth step is: With the help of High Frequency Structure Simulator (HFSS) electromagnetic simulation software, parametric modeling is carried out, and simulation analysis is completed to calculate the performance indicators of the array antenna. The fitness function in the above optimization formula is obtained, and the established optimization model is iteratively solved using the genetic algorithm to finally obtain the control point coordinates (x i ,y i ) and the optimal solution of the layout parameter d, and achieve the performance requirements of the array antenna within the required frequency band.

4. The shape and layout collaborative optimization design method of the EBG decoupling structure according to claim 2, characterized in that: The normal working condition of the array antenna in the required frequency band is: the reflection coefficient S 11 Less than -10dB.

5. The shape and layout collaborative optimization design method of the EBG decoupling structure according to claim 1, 2 or 4, characterized in that: The non-uniform curved EBG decoupling structure (2) is placed between array antenna elements and is non-uniformly and symmetrically distributed about the x-axis, which is beneficial to improving the decoupling performance of the array antenna.

6. The shape and layout collaborative optimization design method of the EBG decoupling structure according to claim 3, characterized in that: The non-uniform curved EBG decoupling structure (2) is placed between array antenna elements and is non-uniformly and symmetrically distributed about the x-axis, which is beneficial to improving the decoupling performance of the array antenna.

7. The array antenna designed by the EBG decoupling structure shape and layout collaborative optimization design method of the array antenna according to claim 1, characterized in that: include: M rectangular microstrip patch (1) units on the upper layer, a non-uniform curved EBG decoupling structure (2), an RO4350B dielectric substrate (3) on the middle layer, a ground plate (4) on the lower layer, M microstrip feeding ports (5) and M microstrip transmission lines (6), wherein both ends of the microstrip feeding port (5) are connected to the ground plate (4) and the microstrip transmission line (6) respectively; The M rectangular microstrip patches (1) are respectively connected to the M microstrip transmission lines (6); each group of rectangular microstrip patch (1) units and their microstrip transmission lines (6) are arranged in sequence symmetrically along the central axis, with spacing provided between the groups; the M microstrip feeding ports (5) are arranged in sequence, and an excitation voltage is fed through the microstrip feeding ports (5).

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