Dual-frequency circularly polarized antenna based on polarization conversion metasurface

Abstract

The application discloses a dual-frequency circularly polarized antenna based on polarization conversion metasurface and relates to the technical field of antennas, which comprises four-layer dielectric plates and a feed structure; the four-layer dielectric plates comprise a first-layer dielectric plate, a second-layer dielectric plate, a third-layer dielectric plate and a fourth-layer dielectric plate, and the four-layer dielectric plates are all air cavities; a bowtie dipole with a U-shaped groove is arranged on the first-layer dielectric plate; metasurface structures are arranged on the second-layer dielectric plate and the third-layer dielectric plate; the fourth-layer dielectric plate is a metal bottom plate; the feed structure is located at the center of the antenna and penetrates through the four-layer dielectric plates; the radiation unit adopts a dual-frequency bowtie dipole antenna, the unbalanced-to-balanced conversion feed is realized by using a coupling balun, the reflecting surface structure with the dual-frequency polarization twist characteristic is loaded at the same time, the conversion from linear polarization to circular polarization is realized at the 0.9GHz and 2.4GHz frequency bands, and thus the dual-circular polarization operation of the dual-RFID frequency bands is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of antennas, in particular to a dual-frequency circularly polarized antenna based on polarization conversion metasurface, which can be applied to a radio frequency identification system operating at 0.9 GHz and 2.4 GHz as a reader antenna. BACKGROUND

[0002] The statements in this section merely provide background information related to the present disclosure and can not constitute the prior art.

[0003] Radio frequency identification systems play an increasingly important role in Internet of Things applications. Through tracking and intelligent management of each item, real-time global item sharing can be achieved. Meanwhile, 6G will face more diverse application scenario demands and challenges, with a wider coverage range and a wider coverage object. As a key technology in RFID, it plays an important role. According to different application scenarios, RFID reader antennas can be fixed and handheld, and have an important role in the identification ability of wireless identification systems. In addition, tags are placed at will and integrated with antennas with linear polarization. Therefore, far-field reader antennas are often designed to work in circular polarization mode. In order to improve the efficiency of the reader, multi-band operation is also very important, which avoids the need for multiple single-band antenna elements. 0.9 GHz and 2.4 GHz are widely used in RFID due to their high data transmission speed and good far-field performance. Therefore, dual-band antennas are of great significance to RFID systems.

[0004] Dual-frequency circularly polarized antennas are beneficial to system integration, frequency reuse, and transceiver sharing. There are many ways to achieve dual-frequency circular polarization, such as single-feed multi-mode antennas, single-feed multi-layer antennas, multi-feed multi-mode antennas, and multi-feed multi-layer antennas. Research on dual-frequency circularly polarized antennas also includes optimizing slot antennas, combining planar monopole antennas to achieve wideband, and using array antennas to achieve miniaturization. In addition, artificial electromagnetic materials have unique properties that distinguish them from natural materials. They can achieve any dielectric constant and magnetic permeability to achieve the desired performance, and can control the amplitude and phase of electromagnetic waves, which has attracted widespread attention. Although there are many ways to achieve dual-frequency circular polarization, there are still few designs of dual-frequency circularly polarized antennas based on practical applications in radio frequency identification systems. In particular, due to the limitations of wavelength in the UHF frequency band, it is extremely important to design miniaturized metasurface units, which are expected to continuously innovate structures and apply artificial electromagnetic material structures to further improve antenna performance. SUMMARY

[0005] The purpose of the present application is to provide a dual-frequency circularly polarized antenna based on polarization conversion metasurface, which uses a dual-frequency bowtie dipole antenna as the radiation unit and realizes unbalanced-to-balanced conversion feeding through a coupled balun; meanwhile, a reflective surface structure with dual-frequency polarization twisting characteristics is loaded, which can realize linear-to-circular polarization conversion at 0.9GHz and 2.4GHz frequency bands, thereby realizing dual-circular polarization operation at dual-RFID frequency bands.

[0006] The technical scheme of the present application is as follows:

[0007] A dual-frequency circularly polarized antenna based on polarization conversion metasurface, comprising: four layers of dielectric plates and a feeding structure.

[0008] The four layers of dielectric plates comprise: a first layer of dielectric plate, a second layer of dielectric plate, a third layer of dielectric plate and a fourth layer of dielectric plate, and the four layers of dielectric plates are all air cavities; the first layer of dielectric plate is provided with a bowtie dipole containing a U-shaped slot; the second layer of dielectric plate and the third layer of dielectric plate are provided with metasurface structures; and the fourth layer of dielectric plate is a metal bottom plate.

[0009] The feeding structure is located at the center of the antenna and penetrates through the four layers of dielectric plates.

[0010] Further, the bowtie dipole containing a U-shaped slot comprises: a U-shaped slot engraved dipole arm and a double-arm gap.

[0011] Further, the second layer of dielectric plate is provided with a high-frequency polarization conversion metasurface unit.

[0012] Further, the high-frequency polarization conversion metasurface unit comprises: strip-shaped patches distributed symmetrically along the diagonal.

[0013] Further, the third layer of dielectric plate is provided with a low-frequency polarization conversion metasurface unit.

[0014] Further, the low-frequency polarization conversion metasurface unit comprises: arrow-shaped patches in the diagonal direction and square patches at the other two vertices.

[0015] Further, the first layer of dielectric plate, the second layer of dielectric plate, the third layer of dielectric plate and the fourth layer of dielectric plate are all provided with a through gap in the center for the feeding structure to penetrate.

[0016] Further, the feeding structure is a microstrip tapered balun structure.

[0017] Further, the microstrip tapered balun structure comprises: a dielectric plate, a strip-shaped microstrip line and a tapered microstrip line.

[0018] Compared with the existing technology, the present application has the following advantages:

[0019] 1、The polarization conversion metasurface unit in the application adopts a multi-layer structure, and can independently regulate the polarization twist characteristics of high-frequency bands and low-frequency bands far away, thereby laying a foundation for realizing double-frequency circular polarization at a long distance.

[0020] 2、The application can reduce the influence on the polarization twist characteristics of the reflector by taking the double-frequency linear polarization dipole antenna with a symmetrical structure as a radiation source, and can realize circular polarization radiation at double frequencies by regulating the cross-polarized electromagnetic waves with equal amplitudes and a phase difference of 90° above the antenna through the reflected waves, and superimposing the uplink radiation waves. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1a is the left view of the antenna according to the application;

[0022] Figure 1b is the front view of the antenna according to the application;

[0023] Figure 1c is the top view of the antenna according to the application;

[0024] Figure 2 is the schematic diagram of the bow-tie dipole structure according to the application;

[0025] Figure 3 is the structure diagram of the high-frequency polarization conversion unit according to the application;

[0026] Figure 4 is the structure diagram of the low-frequency polarization conversion unit according to the application;

[0027] Figure 5 is the structure diagram of the microstrip gradual change balun according to the application;

[0028] Figure 6 is the performance simulation result diagram of the polarization conversion metasurface according to the application;

[0029] Figure 7 is the simulation result of the reflection coefficient of the antenna according to the application;

[0030] Figure 8 is the simulation result of the axial ratio of the antenna according to the application;

[0031] Figure 9 is the simulation result of the radiation pattern of the antenna according to the application at 0.9 GHz;

[0032] Figure 10 is the simulation result of the radiation pattern of the antenna according to the application at 2.4 GHz.

[0033] Label: 1 - the first layer of dielectric plate, 2 - the second layer of dielectric plate, 3 - the third layer of dielectric plate, 4 - the fourth layer of dielectric plate, 5 - the feed structure, 6 - the bowtie dipole, 7 - the high-frequency band polarization conversion metasurface unit, 8 - the low-frequency band polarization conversion metasurface unit, 61 - the dipole arm, 62 - the double-arm gap, 71 - the strip patch, 81 - the first square patch, 82 - the arrowhead patch, 83 - the second square patch, 51 - the dielectric plate, 52 - the strip microstrip line, 53 - the tapered microstrip line. DETAILED DESCRIPTION

[0034] It should be noted that the relational terms herein such as first and second and the like are used solely to distinguish one from another entity or action, without necessarily requiring or implying any actual relationship or order between such entities or actions. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by "comprises... a" does not, without more constraints, exclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.

[0035] The features and characteristics of the present application will be further described with reference to the following examples.

[0036] Example 1

[0037] Please refer to Figure 1a-5 A dual-frequency circularly polarized antenna based on polarization conversion metasurface, comprising: four layers of dielectric plates and a feed structure 5;

[0038] The four layers of dielectric plates include: a first layer of dielectric plate 1, a second layer of dielectric plate 2, a third layer of dielectric plate 3 and a fourth layer of dielectric plate 4, and the four layers of dielectric plates are all air cavities;

[0039] It should be noted that the second layer of dielectric plate 2, the third layer of dielectric plate 3 and the fourth layer of dielectric plate 4 together serve as a reflective plate with polarization conversion characteristics;

[0040] The first layer of dielectric plate 1 is provided with a bowtie dipole containing a U-shaped groove 6;

[0041] The second layer of dielectric plate 2 and the third layer of dielectric plate 3 are provided with metasurface structures;

[0042] The fourth layer of dielectric plate 4 is a metal bottom plate, which ensures total reflection of electromagnetic waves and realizes unidirectional radiation;

[0043] That is, the first layer of medium plate 1 upper surface printed with U-shaped groove tie type dipole 6, the second layer of medium plate 2 and the third layer of medium plate 3 upper surface printed with super surface structure; preferably, the four layers of medium plate between the air cavity height h1, h2, h3 is 7mm, 10mm, 32mm respectively from top to bottom between the adjacent plate;

[0044] The feed structure 5 is located in the center of the antenna, and penetrates the four layers of medium plate.

[0045] In this embodiment, specifically, the U-shaped groove containing tie type dipole 6, including: U-shaped groove dipole arm 61 and double-armed gap 62; that is, the first layer of medium plate 1 upper surface printed with tie type dipole 6, U-shaped groove is engraved in the double-armed, configure multi-resonant structure, realize 0.9GHz and 2.4GHz dual-band operation; At the same time, the antenna has the characteristics of structural symmetry and bidirectional radiation, as a radiation source antenna, the uplink radiation electromagnetic wave superposition has the reflection wave with equal amplitude and 90° phase difference, to realize dual-band circularly polarized radiation.

[0046] In this embodiment, specifically, the second layer of medium plate 2 is provided with high frequency band polarization conversion super surface unit 7, which can realize polarization conversion in 2.4GHz frequency band.

[0047] In this embodiment, specifically, the high frequency band polarization conversion super surface unit 7, including: along the diagonal line symmetric distribution of strip patch 71; That is, the strip patch 71 is printed on the upper surface of the second layer of medium plate 2 along the diagonal line symmetric distribution.

[0048] In this embodiment, specifically, the third layer of medium plate 3 is provided with low frequency band polarization conversion super surface unit 8, which can realize miniaturized reflector unit design, and realize polarization conversion in 0.9GHz frequency band.

[0049] In this embodiment, specifically, the low frequency band polarization conversion super surface unit 8, including: arrow type patch 82 along the diagonal direction and square patch located at the other two vertices.

[0050] In this embodiment, specifically, the first layer of medium plate 1, the second layer of medium plate 2, the third layer of medium plate 3 and the fourth layer of medium plate 4 are provided with through slits in the center for the feed structure 5 to penetrate.

[0051] In this embodiment, specifically, the feed structure 5 is a microstrip tapered balun structure.

[0052] In this embodiment, specifically, the microstrip tapered balun structure includes: a dielectric plate 51, a strip microstrip line 52 and a tapered microstrip line 53; that is, the strip microstrip line 52 and the tapered microstrip line 53 are printed on both sides of the dielectric plate 51, realizing balanced feeding of the dipole, and at the same time, the feeding structure 5 reduces the interference on the surface current of the reflector compared with other feeding structures 5, and is easy to install.

[0053] Embodiment two

[0054] Embodiment two is an application case of a dual-frequency circularly polarized antenna based on a polarization conversion metasurface proposed in embodiment one.

[0055] Please refer to Figure 1a-10 A dual-frequency circularly polarized antenna based on a polarization conversion metasurface, comprising: a four-layer dielectric plate and a feeding structure 5;

[0056] The four-layer dielectric plate includes: a first layer dielectric plate 1, a second layer dielectric plate 2, a third layer dielectric plate 3 and a fourth layer dielectric plate 4, and the four-layer dielectric plate is air cavity; The air cavity height h1, h2, h3 between the adjacent plates from top to bottom is 7mm, 10mm, 32mm respectively;

[0057] The first layer dielectric plate 1 has a bowtie dipole 6 with a U-shaped slot printed on the upper surface;

[0058] The second layer dielectric plate 2 has a high-frequency polarization conversion metasurface unit 7 printed on the upper surface;

[0059] The third layer dielectric plate 3 has a low-frequency polarization conversion metasurface unit 8 printed on the upper surface;

[0060] The fourth layer dielectric plate 4 is a metal bottom plate;

[0061] The feeding structure 5 is located at the center of the antenna and penetrates the four-layer dielectric plate;

[0062] The first layer dielectric plate 1 is an FR-4 rectangular plate with a dielectric constant of 4.4 and a thickness of 3mm;

[0063] The second layer dielectric plate 2 and the third layer dielectric plate 3 are TP-2 rectangular plates with a dielectric constant of 4.5 and thicknesses of 3mm and 8mm respectively;

[0064] The first layer dielectric plate 1, the second layer dielectric plate 2, the third layer dielectric plate 3 and the fourth layer dielectric plate 4 are all provided with a 14mm*7mm slot in the center for the feeding structure 5 to penetrate;

[0065] The feeding structure 5 is an FR-4 rectangular plate with a dielectric constant of 4.4 and a thickness of 1mm.

[0066] Referring to Figure 2 In the embodiment, specifically, the bowtie dipole 6 with a U-shaped groove includes: a dipole arm 61 engraved with a U-shaped groove and a gap 62 between the two arms.

[0067] Wherein, the length L of the first layer of dielectric plate 1 is 120mm, the width W is 76mm; the arm length Dl of the dipole arm 61 engraved with a U-shaped groove is 52mm, the end width Dw is 26mm, wherein the parameters Sw of the U-shaped groove are 14.5mm and Sl is 11.8mm.

[0068] Referring to Figure 3 In the embodiment, specifically, the high-frequency polarization conversion metasurface unit 7 includes: strip patch 71 distributed along the diagonal line;

[0069] Wherein, the side length Ux of the second layer of dielectric plate 2 is 30mm, the length Hl of the strip patch 71 is 26mm, the width Hw is 4.7mm, and the overall structure is arranged in a 5x5 array.

[0070] Referring to Figure 4 In the embodiment, specifically, the low-frequency polarization conversion metasurface unit 8 includes: arrow-shaped patch 82, first square patch 81 and second square patch 83 along the diagonal direction;

[0071] Wherein, the side length Ux of the third layer of dielectric plate 3 is 30mm, the side length S1 of the first square patch 81 and the second square patch 83 is 8.5mm, the parameter S2 of the arrow-shaped patch 82 is 13mm, and Wp is 16mm.

[0072] Referring to Figure 5 In the embodiment, specifically, the feed structure 5 is a microstrip tapered balun structure, and the microstrip tapered balun structure includes: a dielectric plate 51, a strip microstrip line 52 and a tapered microstrip line 53;

[0073] Wherein, the length Lf of the dielectric plate 51 is 60mm, the width Wf is 12mm, and the width a1 of the strip microstrip line 52 is 1.29mm.

[0074] Figure 6 The performance simulation result of the polarization conversion metasurface is shown in the figure, and the phase difference is the phase difference between the reflected wave and the incident wave. It can be seen that the reflection surface can achieve a phase difference of 90° at 0.9GHz and 2.4GHz. In addition, from the polarization conversion rate (PCR) simulation result, it can be seen that the polarization conversion metasurface in the embodiment has a polarization conversion rate (PCR) greater than 90% in the wide frequency band of the dual frequency band (0.9GHz / 2.4GHz), indicating that the polarization conversion metasurface in the embodiment has high polarization conversion capability in the dual frequency band range.

[0075] Figure 7 The simulation result of the reflection coefficient of the antenna of the application is shown in the figure. It can be seen that the impedance bandwidth of the -10dB of the antenna of the application is 0.86-1GHz and 2.38-2.43GHz in the low frequency band and the high frequency band respectively.

[0076] Figure 8 The simulation result of the axial ratio of the antenna of the application is shown in the figure. It can be seen that the axial ratio bandwidth of the antenna of the application is 0.86-0.91GHz and 2.22-2.43GHz in the low frequency band and the high frequency band respectively.

[0077] Figure 9 The simulation result of the radiation pattern of the antenna of the application at 0.9GHz is shown in the figure. It can be seen that the radiation pattern of the antenna of the application in the xoz plane and the yoz plane is good, and circularly polarized radiation can be achieved, and the right-handed circularly polarized gain is 5.91dB.

[0078] Figure 10 The simulation result of the radiation pattern of the antenna of the application at 2.4GHz is shown in the figure. It can be seen that the radiation pattern of the antenna of the application in the xoz plane and the yoz plane is good, and circularly polarized radiation can be achieved, and the right-handed circularly polarized gain is 7.9dB.

[0079] The above-described embodiments only express the specific implementation of the present application, and the description is more specific and detailed, but it cannot be understood as a limitation on the protection scope of the present application. It should be pointed out that for ordinary skilled in the art, without departing from the technical scheme concept of the present application, a number of modifications and improvements can be made, which are within the protection scope of the present application.

[0080] This Background section is provided for generally presenting the context of the application The work of the present inventors, to the extent it is described in this Background section, and the work of others in the field, to the extent it is described in this Background section and the descriptions of which are not admitted to be prior art merely by virtue of their inclusion in this Background section, are not necessarily considered to be anticipatory art.

Claims

1. A dual-frequency circularly polarized antenna based on polarization conversion metasurface, characterized in that, The utility model relates to a four-layer dielectric plate and feed structure (5) are included: The four-layer dielectric plate includes: first layer dielectric plate (1), second layer dielectric plate (2), third layer dielectric plate (3) and fourth layer dielectric plate (4), and all are air cavity between the four-layer dielectric plate;The first layer dielectric plate (1) is equipped with the bowtie type dipole (6) containing U-shaped groove;Second layer dielectric plate (2) and third layer dielectric plate (3) are equipped with super surface structure;The fourth layer dielectric plate (4) is metal bottom plate; The feed structure (5) is located in the antenna center, and penetrates four-layer dielectric plate; Second layer dielectric plate (2) is equipped with high frequency band polarization conversion super surface unit (7); The high frequency band polarization conversion super surface unit (7) includes: strip patch (71) distribution along the diagonal line symmetry; Third layer dielectric plate (3) is equipped with low frequency band polarization conversion super surface unit (8); The low frequency band polarization conversion super surface unit (8) includes: arrowhead type patch (82) in diagonal direction and square patch in another two apexes. The bowtie type dipole (6) containing U-shaped groove includes: dipole arm (61) engraved with U-shaped groove and double-arm gap (62).

2. The dual-frequency circularly polarized antenna based on polarization conversion metasurface according to claim 1, wherein, The first layer dielectric plate (1), second layer dielectric plate (2), third layer dielectric plate (3) and fourth layer dielectric plate (4) center all open and are equipped with the feed structure (5) and enter the entering gap.

3. The dual-frequency circularly polarized antenna based on polarization conversion metasurface according to claim 1, wherein, The feed structure (5) is microstrip gradually variable balun structure.

4. The dual-frequency circularly polarized antenna based on polarization conversion metasurface according to claim 1, wherein, The microstrip gradually variable balun structure includes: dielectric plate (51), strip microstrip line (52) and gradually variable microstrip line (53).

5. The dual-frequency circularly polarized antenna based on polarization conversion metasurface according to claim 4, characterized in that, ​

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