CN114498058A - A Broadband Circularly Polarized Pattern Diversity Antenna Based on Metasurface Elements - Google Patents

Abstract

The invention discloses a broadband circular polarization directional pattern diversity antenna based on a metasurface unit, comprising a top metal layer, an upper medium layer, an intermediate metal layer, a lower medium layer and a bottom metal layer arranged from top to bottom. A metasurface radiation array is arranged on the metal layer; 5 cross-shaped slits are arranged on the middle metal layer; the bottom metal layer contains two feeding networks, of which the feeding network of the first port contains a microstrip line sequential coupling Feeding structure, the feeding network of the second port includes 3 Wilkinson power dividers and 4 microstrip line sequential coupling feeding structure. The present invention utilizes the four characteristic modes of the metasurface array and the sequential coupling feed structure to enable the antenna to radiate circularly polarized waves while achieving pattern diversity, which not only solves the problem of multipath interference in wireless communication systems, but also reduces the antenna profile height and widen the working bandwidth of the antenna.

Description

A Broadband Circularly Polarized Pattern Diversity Antenna Based on Metasurface Elements

technical field

The invention relates to the technical field of pattern diversity antennas, in particular to a broadband circular polarization pattern diversity antenna based on metasurface units.

Background technique

In the research and design of antennas, improving the quality of antenna transmission and reception and enhancing the efficiency of spectrum use have become important research directions. Diversity technology can not only make up for the fading of each signal and reduce the influence of multipath fading by using the incoherent characteristics of the channel, but also improve the reliability and stability of the channel, so it is widely used in communication systems. Antenna diversity technology can be divided into polarization diversity and pattern diversity. Among them, polarization diversity uses the characteristics that electromagnetic waves of different polarizations at the same location are independent of each other and do not affect each other, and the signals of different polarizations are received at the receiving end. Synthesis to make up for the influence of multipath fading, so as to achieve stable signal reception; compared with polarization diversity, pattern diversity is more difficult, because different working modes require different radiation patterns, but different modes Usually there are different operating frequencies, and the combination of multiple antennas will inevitably lead to the complexity of the overall structure and the increase in size. The pattern diversity antenna can use pattern diversity to realize uncorrelated channels, which is a good solution to the radiation in the diversity system. The coupling between the units will seriously increase the correlation of the signal and reduce the problem of radiation efficiency.

In addition, circularly polarized antennas are very effective in combating multipath interference. As far as the current reports are concerned, there are very few antennas with both circular polarization performance and pattern diversity, and they all have multiple layers, relatively complex structures and narrow operating bandwidths. According to investigation and understanding, the existing technologies that have been disclosed are as follows:

In 2014, Chang Jiang Deng, Zhenghe Feng and others published an article entitled "A Circularly Polarized Pattern DiversityAntenna for Hemispherical Coverage" in "IEEE TRANSACTIONS ONANTENNAS AND PROPAGATION", the antenna consists of two parts to achieve circular polarization performance of pattern diversity. . Among them, the bent monopole with co-direction feeding achieves an omnidirectional radiation pattern, while the other achieves broad-side radiation circular polarization performance by exciting an L-shaped monopole. Due to the bending of the microstrip and the double-layer structure of the antenna, the entire structure is relatively complex and the working bandwidth of the antenna is only 6.3%, which is relatively narrow.

In 2018, Wei Lin, Hang Wong et al. published an article entitled "Circularly Polarized Antenna With Reconfigu rableBroadside and Conical Beams Facilitated by a Mode Switchable Feed Network" in "IEEE TRANSACTIONS ON ANTENNASANDPROPAGATION", and proposed a pattern that can be reproduced. Constructed circularly polarized antenna. The antenna is fed through a reconfigurable feed network and coupled with an L-shaped probe to excite the TM11 and TM21 modes of the upper radiating antenna, forming a circularly polarized antenna with reconfigurable broadside and conical patterns. However, the antenna needs to use a reconfigurable DC bias circuit, which makes the structure of the entire antenna relatively complex, and also has a high profile, and the operating bandwidth of the antenna is only 7.8%, which is relatively narrow.

Difficulty in solving the above technical problems: while realizing pattern diversity, the cross section of the antenna can be kept less than 0.07λ ₀ and the antenna can obtain a wider working bandwidth.

Significance of solving the above-mentioned technical problems: Solving the above-mentioned technical problems is conducive to the realization of pattern diversity and integration in the communication system using the present invention as an antenna, and solves the higher requirement of the circularly polarized bandwidth for wireless communication due to the increase of frequency bands.

SUMMARY OF THE INVENTION

In order to solve the above technical problems, the present invention provides a broadband circularly polarized pattern diversity antenna based on a metasurface unit.

In order to achieve the above object, the present invention is achieved through the following technical solutions:

The present invention is a broadband circular polarization pattern diversity antenna based on metasurface unit, comprising a top metal layer, an upper dielectric layer, an intermediate metal layer, a lower dielectric layer and a bottom metal layer arranged from top to bottom. A metasurface radiation array is arranged in the middle of the layer. The array includes a middle array composed of 3*3 square annular metal units and an outer array composed of four 3*3 square annular metal units, which are symmetrical to the central axis. The center of the metasurface radiation array coincides with the center of the upper dielectric layer;

The middle position of the middle metal layer is provided with a cross-shaped middle slot and four cross-shaped outer slots. coincide;

Two feeding networks are arranged on the bottom metal layer, wherein the feeding network fed by the first port feeds the metasurface radiation array through the intermediate microstrip line sequential coupling structure and the intermediate slot, so that the antenna radiates circular poles chemical wave and a broadside pattern; the feed network fed by the second port is coupled to the supersonic via four outboard microstrip line sequential coupling structures, three Wilkinson power dividers and four outboard slots. The surface radiation array is fed so that the antenna radiates circularly polarized waves and a conical pattern.

A further improvement of the present invention is that: the middle slit and the four outer slits are formed by two horizontal and vertical rectangular slits orthogonal to each other, wherein the two rectangular slits in the middle slit have the same length and the same width, and the outer The width of one of the rectangular slits of the slits is smaller than the width of the rectangular slit of the middle slit, the width of the other rectangular slit is the same as the width of the rectangular slit of the middle slit, and the length of the two rectangular slits of the outer slit is the same as that of the middle slit. The lengths of the intermediate slits are the same.

A further improvement of the present invention is that: both the middle microstrip line sequential coupling structure and the outer microstrip line sequential coupling structure include a 90-degree phase delay structure, a feeding structure and an impedance matching structure, wherein the middle microstrip line sequential coupling structure The length of the 90-degree phase delay structure of the coupling structure and the sequential coupling structure of the outer microstrip line is both 8.13 mm, the length of the feeding structure is both 1.5 mm, and the impedance of the sequential coupling structure of the middle microstrip line is The length of the matching structure is 1.4 mm, and the length of the impedance matching structure of the outer microstrip line sequential coupling structure is 3.4 mm.

A further improvement of the present invention is that the impedances of the two feeding networks, the first port and the second port are all 50 ohms.

A further improvement of the present invention is that: the upper dielectric layer and the lower dielectric layer are made of Rogers 4003C high-frequency plate, the relative dielectric constant is 3.55, and the loss tangent value is 0.0027.

A further improvement of the present invention is that the length of the upper dielectric layer and the lower dielectric layer are both 115 mm and 100 mm, the thickness of the upper dielectric layer is 3.1 mm, and the thickness of the lower dielectric layer is 0.813 mm.

A further improvement of the present invention is that: the distance between the middle array and the outer arrays around it is 0.9mm, the inner side length of the square annular metal unit in each array is 6.7mm, the outer side length is 8.7mm, and the two The distance between the adjacent square annular metal units is 0.9 mm.

The beneficial effects of the present invention are: the present invention applies the cross-shaped metasurface radiation array to the circularly polarized pattern diversity antenna for the first time, and has the following effects: 1. Compared with the linearly polarized pattern diversity antenna, the present invention has the following advantages: The cross-shaped metasurface unit array composed of square ring-shaped metal units realizes that the antenna radiates circularly polarized waves at the same time of pattern diversity, and has a very good effect in anti-multipath interference; 2, the present invention utilizes metasurface units The working bandwidth of the antenna is widened, so that the circularly polarized pattern diversity antenna works between 4.16GHz and 4.76GHz, with a relative bandwidth of 13.4%, which is similar to the existing circularly polarized pattern diversity antenna mentioned in the background art. Compared with the present invention, the working bandwidth of the antenna is increased by about 1 times; 3, the present invention maintains the low profile characteristic of the antenna, and the profile of the antenna is 0.05λ ₀ , which is beneficial to the integration of the antenna.

Description of drawings

Figure 1 is a schematic diagram of the three-dimensional structure of the present invention.

FIG. 2 is a schematic structural diagram of a metasurface radiation unit of the present invention.

FIG. 3 is a schematic structural diagram of the intermediate metal layer of the present invention.

FIG. 4 is a schematic structural diagram of a feeding network of the present invention.

FIG. 5 is a detailed schematic diagram of the sequential coupling structure of microstrip lines in the feeding network of the present invention.

6 , 7 , 8 , 9 , 10 and 11 are axial ratio simulation graphs when the sequential coupling structure of the microstrip line in the feeding network of the present invention is designed with different dimensions.

FIG. 12 is a graph of an S-parameter simulation result according to an embodiment of the present invention.

FIG. 13 is an axial ratio simulation curve diagram when a broadside radiation pattern (feeding at the first port) is excited according to an embodiment of the present invention.

14 is a simulation graph of the axial ratio at phi=0° and phi=45° at 4.4 GHz when a broadside radiation pattern (feeding at the first port) is excited according to an embodiment of the present invention.

15 is a radiation pattern of phi=0° and phi=45° at 4.4 GHz when a broadside radiation pattern (feeding at the first port) is excited according to an embodiment of the present invention.

FIG. 16 is an axial ratio simulation curve diagram when a conical radiation pattern (second port feeding) is excited according to an embodiment of the present invention.

17 is a simulation graph of the axial ratio at 4.4 GHz phi=0° and phi=45° when the conical radiation pattern (second port feeding) is excited according to an embodiment of the present invention.

18 is a radiation pattern at 4.4 GHz phi=0° and phi=45° when a conical radiation pattern (second port feeding) is excited according to an embodiment of the present invention.

Among them, 1-top metal layer, 2-upper dielectric layer, 3-intermediate metal layer, 4-lower dielectric layer, 5-first port, 6-bottom metal layer, 7-outside microstrip line sequential coupling structure, 8 -outside array, 9-middle array, 10-square ring metal unit, 11-outside slot, 12-second port, 13-Wilkinson power divider, 14-middle slot, 15-middle microstrip line sequential coupling structure.

Detailed ways

In order to illustrate the technical solution of the present invention more clearly, the technical solution of the present invention is further described in detail below in conjunction with the accompanying drawings:

The present invention is a broadband circularly polarized pattern diversity antenna based on a metasurface unit, comprising three metal layers and two dielectric layers, from top to bottom: top metal layer 1, upper dielectric layer 2, middle metal layer Layer 3, lower dielectric layer 4 and bottom metal layer 6, wherein, the upper dielectric layer 2 and the lower dielectric layer 4 are made of Rogers 4003C high-frequency material, the relative dielectric constant is 3.55, and the loss tangent value is 0.0027. The upper dielectric layer 2 and the lower dielectric layer 4 are both 115 mm long and 100 mm wide, but the upper dielectric layer 2 has a thickness of 3.1 mm and the lower dielectric layer 4 has a thickness of 0.813 mm.

In the middle position of the top metal layer 1 on the upper surface of the upper dielectric layer 2, an intermediate array 9 is formed by 9 square annular metal units arranged in an array of 3*3, and the four sides of the intermediate array are arranged at an interval of 0.9 mm. There is an outer array, and each outer array is formed by 9 square annular metal units arranged in a 3*3 array. The inner side length of the square ring-shaped metal unit 10 is 6.7 mm, the outer side length is 8.7 mm, and the distance between two adjacent square ring-shaped metal units 10 is 0.9 mm.

The size of the intermediate metal layer 3 is the same as that of the lower surface of the upper dielectric layer 2, with a length of 115 mm and a width of 100 mm. As shown in FIG. 3 , five cross-shaped slits are arranged in the intermediate layer dielectric layer 3 to realize the coupling and feeding of the intermediate array 9 and the outer array 8 , which are the intermediate slit in the middle of the intermediate layer dielectric layer 3 and the The four outer slits on the outside of the middle slit, each of which is composed of two mutually orthogonal rectangular slits, wherein the two rectangular slits of the middle slit have the same length and the same width, and one of the rectangular slits of the outer slit has the same length and width. The width is smaller than the width of the rectangular slot in the middle slot, the width of the other rectangular slot is the same as the width of the rectangular slot in the middle slot, and the lengths of the two rectangular slots in the outer slot are the same as the length of the middle slot . Preferably, the length of the two rectangular slits in the middle slit is both 15mm and the width is 1mm. One of the rectangular slits of each outer slit has a width of 0.4 mm, and the other rectangular slit has a width of 1 mm and a length of 15.5 mm.

As shown in FIG. 4 , the underlying metal layer 6 includes two feeding networks, wherein the feeding network fed by the first port 5 is connected to the metasurface radiation array through the intermediate microstrip line sequential coupling structure 15 and the intermediate slot 14 Feeding is carried out so that the antenna radiates circularly polarized waves and a broadside pattern; the feeding network fed by the second port 12 is sequentially coupled through four outer microstrip lines 7, three Wilkinson power dividers 13 and the four outer slots 11 feed the metasurface radiation array, so that the antenna radiates circularly polarized waves and a conical pattern. The widths of the two feeding networks are both 1.77mm, and the width of the branch line of the Wilkinson power divider 13 is 0.9mm and the length is 10.23mm. As shown in FIG. 5 , the length L1=8.13mm of the 90-degree phase delay structure 151 of the intermediate microstrip line sequential coupling structure 15, the length L2=1.5mm of the feeding structure 152, the length L3=1.4mm of the impedance matching structure 153, The length L4=8.13mm of the 90-degree phase delay structure 71 of the outer microstrip line sequential coupling structure 7, the length L5=1.5mm of the feeding structure 72, and the length L6=3.4mm of the impedance matching structure 73. 6, 7, 8, 9, 10 and 11, the middle microstrip line sequential coupling structure 15 and the outer microstrip line sequential coupling structure 7 designed according to this size provide the metasurface radiation array. Two electric field components with equal amplitudes and a phase difference of 90 degrees are obtained, so that the axial ratio performance of the antenna can be optimized.

The S-parameter simulation result of the preferred embodiment of the present invention in the CST simulation software is shown in FIG. 12 , wherein the first port 5 corresponds to port 1 in the simulation software, and port 12 corresponds to port 2. In the figure |S11| is the curve of the broadside pattern excited by the first port 5, |S22| in the figure is the curve of the conical pattern excited by the second port 12, and |S21| is the first port 5 and the second port 12 isolation between. As can be seen from the figure, the common frequency range where the values of |S11| and |S22| are less than -10dB is 4.12GHz to 4.82GHz, and the isolation band between the two ports is less than -21dB in the operating frequency range.

The simulation diagram of the variation of the axial ratio with frequency when the broadside radiation pattern is excited in the preferred embodiment of the present invention is shown in Figure 13. It can be seen that the axial ratio of the antenna is less than 3dB when the antenna is 4.14GHz to 4.76GHz, and circularly polarized radiation is realized. characteristic. When the antenna is at 4.4GHz, the axial ratio diagram and radiation pattern of phi=0° and phi=45° are shown in Figure 14 and Figure 15, respectively. The antenna radiates the broadside radiation pattern. The highest gain reaches 4.66dBi, and the cross-polarization is greater than 19dB. .

Fig. 16 shows the simulation diagram of the variation of the axial ratio with frequency when the conical radiation pattern is excited in the preferred embodiment of the present invention, the axial ratio of the antenna is less than 3dB when the antenna is from 4.16GHz to 4.76GHz, and the circularly polarized radiation characteristic is realized. When the antenna is at 4.4GHz, the axial ratio diagram and radiation pattern of phi=0° and phi=45° are shown in Figure 17 and Figure 18, respectively. The antenna radiates the conical radiation pattern, the highest gain reaches 5.95dBi, and the cross-polarization is greater than 20dB. . Finally, the operating frequency range of the antenna is 4.16GHz to 4.76GHz, with a relative bandwidth of 13.4%. The above embodiments are only to illustrate the technical idea of the present invention, and cannot limit the protection scope of the present invention. Any changes made in the technical solution according to the technical idea proposed by the present invention fall into the protection scope of the present invention. Inside.

Claims (7)

1. a broadband circularly polarized pattern diversity antenna based on metasurface unit, comprising top metal layer, upper layer medium layer, middle layer metal layer, lower layer medium layer and bottom layer metal layer set from top to bottom, it is characterized in that: A metasurface radiation array is arranged in the middle of the top metal layer. The array includes a middle array consisting of 3*3 square annular metal units and an outer array consisting of four 3*3 square annular metal units. a central axis-symmetrical cross, the center of the metasurface radiation array coincides with the center of the upper dielectric layer; A cross-shaped middle slot and four cross-shaped outer slots are arranged in the middle position of the middle metal layer, and the middle slot and the outer slot correspond to the center of the middle array and the outer array at the corresponding positions on the top metal layer. coincide; Two feeding networks are provided on the underlying metal layer, wherein the feeding network fed by the first port feeds the metasurface radiation array through the intermediate microstrip line sequential coupling structure and the intermediate slot, so that the antenna radiates circularly polarized waves and a broadside pattern; the feed network fed by the second port is coupled through four outer microstrip line sequential coupling structures, three Wilkinson power dividers, and four said outer slot pairs. The metasurface radiation array is fed so that the antenna radiates circularly polarized waves and a conical pattern. 2. a kind of broadband circularly polarized pattern diversity antenna based on metasurface unit according to claim 1, is characterized in that: described middle slot and four outer slots are mutually positive by horizontal and vertical two rectangular slots. The two rectangular slits of the middle slit have the same length and the same width, the width of one of the rectangular slits of the outer slit is smaller than the width of the rectangular slit of the middle slit, and the width of the other rectangular slit is the same as the width of the middle slit. The rectangular slits of the slits have the same width, and the lengths of the two rectangular slits of the outer slit are the same as the length of the middle slit. 3. a kind of broadband circularly polarized pattern diversity antenna based on metasurface unit according to claim 1, is characterized in that: described middle microstrip line sequential coupling structure and described outer microstrip line sequential coupling structure all comprise 90 Degree phase delay structure, feeding structure and impedance matching structure, wherein the length of the 90-degree phase delay structure of the middle microstrip line sequential coupling structure and the outer microstrip line sequential coupling structure are both 8.13mm, and the feeder structure is 8.13mm. The lengths of the electrical structures are all 1.5 mm, the length of the impedance matching structure of the middle microstrip line sequential coupling structure is 1.4 mm, and the length of the impedance matching structure of the outer microstrip line sequential coupling structure is 3.4 mm. 4 . The broadband circularly polarized pattern diversity antenna based on the metasurface element according to claim 1 , wherein the impedances of the two feeding networks, the first port and the second port are all 50 ohms. 5 . 5. a kind of broadband circularly polarized pattern diversity antenna based on metasurface unit according to claim 1, is characterized in that: described upper dielectric layer and lower dielectric layer all adopt Rogers 4003C high-frequency plate, and the relative permittivity is 3.55, and the loss tangent is 0.0027. 6. A kind of broadband circularly polarized pattern diversity antenna based on metasurface unit according to claim 5, it is characterized in that: the length of described upper dielectric layer and described lower dielectric layer is 115mm, width is 100mm, so The thickness of the upper dielectric layer is 3.1 mm, and the thickness of the lower dielectric layer is 0.813 mm. 7. a kind of broadband circularly polarized pattern diversity antenna based on metasurface unit according to claim 1, is characterized in that: the distance between described middle array and described outer array around it is 0.9mm, in each array The inner side length of the square ring-shaped metal unit is 6.7 mm, the outer side length is 8.7 mm, and the distance between two adjacent square ring-shaped metal units is 0.9 mm.

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