A broadband metasurface antenna loaded with parasitic patches

Abstract

The present invention belongs to the field of wireless communication technology, and specifically relates to a broadband metasurface antenna loaded with parasitic patches. In order to solve the problem of small impedance bandwidth of existing antennas, the antenna of the present invention comprises two layers of dielectric plates and three layers of metal layers. The upper metal layer comprises a 3*3 square metal patch array and four parasitic patches to form a metasurface radiation unit. The middle metal layer is etched with elliptical coupling gaps. The lower metal layer is a microstrip line feeding structure. By loading four parasitic patches on the upper layer and changing the size of some square patches, the impedance matching of the antenna is improved, thereby increasing the antenna bandwidth. The antenna operates at 4.41GHz to 7.61GHz, and the relative bandwidth reaches 53.2%. The peak gain reaches 10.2dBi.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communications, and in particular relates to a broadband metasurface antenna loaded with a parasitic patch. Background Art

[0002] With the rapid development of wireless communications, communication systems such as global positioning systems, satellite communications, and personal communications have put forward higher requirements for the broadband of antennas. Broadband antennas can cover multiple frequency bands and reduce the number of antennas required by the communication system, thereby reducing system weight and reducing costs.

[0003] In recent years, many methods have been proposed to broaden the impedance bandwidth of antennas. Loading metasurfaces is an effective way to increase bandwidth, which has the advantages of low profile and multi-mode. For example, a low-profile broadband planar circularly polarized folded transmit array antenna based on metasurface achieves a peak gain of up to 10.1dBi and a 3dB gain bandwidth of 22% (Jin Yang, ShangTong Chen, Mao Chen, Jun Chen Ke, Ming Zheng Chen, Cheng Zhang, Rui Yang, Xin Li, Qiang Cheng, and Tie Jun Cui. Folded Transmitarray Antenna with CircularPolarization Based on Metasurface. IEEE Transactions on Antennas and Propagation, 2021, 69(2): 806). A low-profile broadband pattern diversity antenna based on a metasurface has an isolation better than 38 dB while maintaining an operating bandwidth of 20.24% (Jianfeng Liu, Zibin Weng, Zhi-Qiang Zhang, Yonghui Qiu, Yi-Xuan Zhang, and Yong-Chang Jiao. A Wideband Pattern Diversity Antenna with a Low Profile Based on Metasurface. IEEE Antennas and Wireless Propagation Letters, 2021, 20(3): 303), but the achieved impedance bandwidth is small.

[0004] In view of this, it is necessary to propose a broadband metasurface antenna with a simple structure to meet the development needs of wireless communications. Summary of the invention

[0005] The object of the present invention is to provide a broadband metasurface antenna loaded with a parasitic patch, which has good broadband impedance characteristics, a simple antenna structure and is easy to process.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A broadband metasurface antenna loaded with a parasitic patch comprises an upper metal layer, a first dielectric layer, an intermediate metal layer, a second dielectric layer, and a lower metal layer arranged in sequence from top to bottom;

[0008] The upper metal layer is composed of two groups of square metal patches and a group of parasitic patches. The first group of square metal patches includes five square metal patches distributed in a cross shape. The second group of square metal patches includes four square metal patches. The four square metal patches are respectively located in the gaps of the five square metal patches distributed in a cross shape, and together with the five square metal patches form a 3*3 supersurface unit. The group of parasitic patches includes four parasitic patches, which are respectively located around the 3*3 supersurface unit and adjacent to the first group of square metal patches. An elliptical coupling gap is etched at the center of the middle metal layer, and the lower metal layer is a microstrip feeder.

[0009] Furthermore, the upper metal layer is located at the center of the first dielectric layer.

[0010] Furthermore, the first group of square metal patches and the second group of square metal patches have different sizes.

[0011] Furthermore, the microstrip feed line is a microstrip feed line with a T-shaped structure.

[0012] Compared with the prior art, the present invention has the following advantages:

[0013] By loading four parasitic patches on the upper layer, a new resonant frequency appears near 6 GHz, and this resonant point can be merged with the original resonant point of the antenna by adjusting the parameters. Therefore, the impedance bandwidth of the parasitic patch antenna proposed by the present invention is relatively wide.

[0014] By changing the size of some square patches, the impedance matching of the antenna is improved. The antenna achieves an impedance bandwidth of 53.2% (|S 11 |≤-10dB).

[0015] The elliptical gap is located in the center of the middle metal layer, and plays the role of coupling and feeding for the upper metasurface unit. Compared with the rectangular coupling gap, it can better improve the overall impedance matching of the antenna and thus achieve a wider impedance bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a structural schematic diagram of the present invention;

[0017] In the figure: 1-upper metal layer, 2-first dielectric layer, 3-middle metal layer, 4-second dielectric layer, 5-lower metal layer, 6-first group of square metal patches, 7-second group of square metal patches, 8-parasitic patches, 9-elliptical coupling gaps, 10-microstrip feed lines;

[0018] Figure 2 The broadband antenna of the present invention is 11 |;

[0019] Figure 3 The current distribution of the broadband antenna of the present invention;

[0020] Figure 4 The impedance characteristic of the broadband antenna of the present invention;

[0021] Figure 5 is the width b of the first group of square metal patches of the present invention for antenna|S 11 | and the impact of impedance matching;

[0022] Figure 6 is the width c of the second group of square metal patches of the present invention for antenna|S 11 | and the impact of impedance matching;

[0023] Figure 7 The elliptical coupling slot pair antenna|S of the present invention 11 | and the impact of impedance matching;

[0024] Figure 8 is the gain of the broadband antenna of the present invention;

[0025] Fig. 9 The directional diagrams of the broadband antenna of the present invention at 4.75 GHz, 6.03 GHz and 7.19 GHz; DETAILED DESCRIPTION

[0026] Example 1

[0027] like Figure 1 As shown, a broadband metasurface antenna loaded with a parasitic patch includes an upper metal layer 1, a first dielectric layer 2, an intermediate metal layer 3, a second dielectric layer 4, and a lower metal layer 5 which are sequentially arranged from top to bottom;

[0028] The upper metal layer 1 is composed of two groups of square metal patches and a group of parasitic patches. The first group of square metal patches 6 includes five square metal patches, which are distributed in a cross shape. The second group of square metal patches 7 includes four square metal patches, which are respectively located in the gaps of the five square metal patches distributed in a cross shape, and together with the five square metal patches, they form a 3*3 super surface unit. The group of parasitic patches includes four parasitic patches 8, which are respectively located around the 3*3 super surface unit and adjacent to the first group of square metal patches 6. The upper metal layer 1 is located at the center of the first dielectric layer 2. The middle metal layer 3 is etched with an elliptical coupling gap 9. The lower metal layer 5 is a microstrip feeder 10. The first group of square metal patches 6 and the second group of square metal patches 7 have different sizes. The microstrip feeder 10 is a microstrip feeder with a T-shaped structure.

[0029] In specific implementation, the parameters of the antenna structure are shown in Table 1:

[0030] Table 1 Antenna structural parameters (unit: mm)

[0031] parameter a b c e f h Value 55 8 8.5 0.65 0.85 24 parameter g k l m z w Value 2.3 5 8 1.1 3.454 0.508

[0032] Both dielectric layers of the antenna are made of Rogers RO4003C material with a dielectric constant of 3.55.

[0033] The square metal patch, the parasitic patch and the middle metal layer are all made of copper.

[0034] Figure 2 The broadband metasurface antenna loaded with parasitic patches is shown. 11 |frequency characteristics (curve 2 in the figure), where the horizontal axis represents the frequency variable in GHz and the vertical axis represents the amplitude variable in dB. For the convenience of comparison, the figure also shows the |S of the metasurface antenna without parasitic patches. 11 |(Curve 1 in the figure). It can be seen that for the antenna without parasitic patches, there are three resonant frequencies f1=4.8GHz, f2=6.6GHz, and f3=7.3GHz. The three operating frequency bands are separated from each other to form three separate frequency bands. When the parasitic patch is loaded, the impedance matching of the antenna is improved, and a new resonant frequency appears at 6GHz. Multiple frequency bands are connected together, greatly widening the working frequency band of the antenna. The final working frequency band of the antenna is 4.41GHz~7.61GHz, the absolute bandwidth is 3.2GHz, and the relative bandwidth is 53.2%.

[0035] Figure 3 The electric field distribution of the antenna at 6 GHz is shown. Figure 3In (a), it can be seen that when no parasitic patch is loaded, the electric field is mainly concentrated on both sides of the metasurface units P1 and P2. When the parasitic patch P3 is loaded ( Figure 3 In (b), the electromagnetic waves are distributed around the metasurface units P1 and P2, and most of them are concentrated near P3. At the same time, the electromagnetic waves between P1, P2, and P3 are greatly enhanced. (P1, P2, and P3 represent the first group of square metal patches, the second group of square metal patches, and the parasitic patches, respectively).

[0036] Figure 4 The impedance characteristics of the broadband metasurface antenna loaded with parasitic patches are shown and compared with the results without parasitic patches. In the figure, the horizontal axis represents the frequency variable in GHz, and the vertical axis represents the impedance in ohms. When the parasitic patch is not loaded, the impedance matching of the antenna at each resonant frequency is not good. For example, at 7.3GHz, the real part of the impedance can reach 131Ω. After loading the parasitic patch, the real part of the impedance of the antenna reaches around 50Ω in the range of 4.41GHz-7.61GHz, thereby improving the impedance matching in this working range.

[0037] Figure 5 The width b of the first set of square metal patches is shown for antenna |S 11 | and the influence of impedance matching. When b = 7.5mm, the antenna is at 7.4GHz, |S 11 | is -6dB( Figure 5 In (a), it does not drop to -10dB, and the bandwidth is narrow. When b = 8.5mm, the antenna is at 6.9GHz, |S 11 | is -9dB( Figure 5 (a)), the bandwidth is narrow. When b = 8mm, the real part of the antenna impedance reaches around 50Ω within the working frequency band ( Figure 5 In (b), the impedance matching is good, and in the frequency range of 4.41 GHz to 7.61 GHz, |S 11 |<-10dB, the widest absolute bandwidth is obtained ( Figure 5 (a)).

[0038] Figure 6 The width c of the second set of square metal patches has an effect on the antenna |S 11 | and the influence of impedance matching. When c = 8mm, the antenna is at 7.1GHz, |S 11 | is -9dB( Figure 6 In (a), the bandwidth is narrow. When c = 9 mm, the antenna is at 7 GHz, |S 11 | is -6.2dB( Figure 6 (a)), the bandwidth is narrow. When c = 8.5mm, the real part of the antenna impedance reaches around 50Ω within the working frequency band ( Figure 6 (b)), the impedance matching is good, and the widest absolute bandwidth of 4.41GHz-7.61GHz is obtained ( Figure 6 (a)).

[0039] Figure 7 shows the elliptical coupling slot for antenna |S 11 | and the influence of impedance matching. And compared with the results when a rectangular coupling slot is used. When a rectangular slot is used in the middle layer, the impedance matching of the antenna at each resonant frequency is not good. For example, at 7GHz, the real part of the impedance can reach 110Ω ( Figure 7 Therefore, the antenna's operating frequency bands are 4.3 GHz to 5.1 GHz, 5.6 GHz to 6.3 GHz, and 7.08 GHz to 7.4 GHz. Figure 7 After adopting the elliptical coupling slot, the real part of the antenna impedance reaches about 50Ω in the range, thereby improving the impedance matching in the working range, and the impedance bandwidth of the antenna reaches 4.41GHz~7.61GHz( Figure 7 (a)).

[0040] Figure 8 The gain characteristics of the broadband metasurface antenna loaded with parasitic patches are shown. The horizontal axis represents the frequency variable in GHz, and the vertical axis represents the gain in dBi. It can be seen that the maximum gain is 10.2dBi within the frequency range of 4.41GHz to 7.61GHz.

[0041] Fig. 9 The radiation pattern of the broadband metasurface antenna loaded with parasitic patches is shown, where Fig. 9 (a) is the antenna’s radiation pattern at 4.75 GHz. Fig. 9 (b) is the directional diagram at 6.03 GHz. Fig. 9 (c) is the directional pattern at 7.19 GHz. It can be seen that as the frequency increases, the main polarization directional pattern of the antenna is basically not distorted.

Claims

1. A broadband metasurface antenna loaded with a parasitic patch, characterized in that: It includes an upper metal layer, a first dielectric layer, an intermediate metal layer, a second dielectric layer, and a lower metal layer arranged in sequence from top to bottom; The upper metal layer is composed of two groups of square metal patches and a group of parasitic patches. The first group of square metal patches includes five square metal patches distributed in a cross shape. The second group of square metal patches includes four square metal patches. The four square metal patches are respectively located in the gaps of the five square metal patches distributed in a cross shape, and together with the five square metal patches, they constitute a 3*3 supersurface unit. The group of parasitic patches includes four parasitic patches, which are respectively located around the 3*3 supersurface unit and adjacent to the first group of square metal patches. An elliptical coupling gap is etched at the center of the middle metal layer, and the lower metal layer is a microstrip feeder.

2. The broadband metasurface antenna loaded with a parasitic patch according to claim 1, characterized in that: The upper metal layer is located at the center of the first dielectric layer.

3. The broadband metasurface antenna loaded with a parasitic patch according to claim 1, characterized in that: The first group of square metal patches and the second group of square metal patches have different sizes.

4. The broadband metasurface antenna loaded with a parasitic patch according to claim 1, characterized in that: The microstrip feed line is a microstrip feed line with a T-shaped structure.

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