Broadband dual-polarized cross-dipole antenna loaded on non-uniform high impedance surface

Abstract

The present invention relates to a broadband dual-polarized cross-dipole antenna loaded with a non-uniform high-impedance surface, and belongs to the field of radio frequency microwave technology. The present invention proposes a non-uniform high-impedance surface structure, which has more degrees of freedom in adjusting the resonant frequency and the reflection phase bandwidth. By loading the non-uniform high-impedance surface structure under the cross-dipole antenna, the broadband and low profile of the antenna are achieved. Therefore, the antenna of the present invention has a wider bandwidth and a lower profile than the traditional dual-polarized cross-dipole antenna. Secondly, by digging a groove inside one of the arms of the cross dipole, the impedance matching of the antenna in the high frequency band is improved. At the same time, by introducing a parasitic patch around the dipole, the impedance matching of the antenna in the entire working frequency band is further improved, and the working bandwidth of the antenna is expanded. Finally, a metal grounding wall is loaded around the antenna to expand the beam width of the antenna. The dual-polarized antenna of the present invention achieves broadband, low profile and high port isolation.

Description

Technical Field

[0001] The invention belongs to the technical field of radio frequency microwaves and relates to a broadband dual-polarization cross-dipole antenna loaded with a non-uniform high-impedance surface. Background Art

[0002] Dual-polarized antenna (DPA) is a new antenna technology that combines two orthogonal polarization directions and works in duplex mode. It is widely used in mobile communication systems due to its polarization diversity. Among various types of dual-polarized antennas, planar cross-dipole antennas are widely used due to their wide bandwidth, simple process, and low processing cost. The reflection phase of the metal reflector of the traditional planar cross-dipole is 180°. Therefore, when the distance between the dipole and the metal reflector is 0.25 wavelengths, the reflected electromagnetic wave and the radiated electromagnetic wave interfere and add, which improves the radiation efficiency. Although good broadband working performance can be achieved, it has a high profile problem, making it difficult to integrate with the carrier platform. High impedance surface (HIS) is a new electromagnetic bandgap structure. Usually within a certain frequency band, the surface of the high impedance surface structure presents high impedance performance and can be regarded as an equivalent magnetic conductor, so that the reflected wave is in phase with the incident wave. It can effectively reduce the distance between the antenna and the metal reflector. By utilizing this property, the new antenna formed by combining the high impedance surface with the traditional antenna has a significant advantage in reducing the antenna profile. However, after replacing the metal floor of the traditional dual-polarized cross-dipole antenna with the traditional square high impedance surface, the input impedance of the antenna is high and changes dramatically with frequency, resulting in poor impedance matching of the antenna and narrow bandwidth. In addition, it is usually necessary to use a complex balun to adjust the impedance matching of the antenna to achieve a wider working bandwidth, which leads to problems such as complex design and processing of the antenna. Summary of the invention

[0003] In view of this, the object of the present invention is to provide a broadband dual-polarized cross-dipole antenna loaded with a non-uniform high-impedance surface. Compared with the classic square high-impedance surface structure, the non-uniform high-impedance surface structure has more degrees of freedom in adjusting its own resonant frequency and reflection phase bandwidth, which also provides more degrees of freedom in adjusting the overall impedance matching when the non-uniform high-impedance surface structure and the cross-dipole antenna are integrated. The antenna of the present invention adopts a cross dipole to achieve orthogonal dual-polarization characteristics. The non-uniform high-impedance surface is used to replace the metal reflector of the traditional cross-dipole antenna to improve the impedance matching of the antenna to increase the bandwidth and reduce the profile of the antenna. By cutting the angle of the dipole arm, the surface current distribution on the dipole arm is changed, the current amplitude of the dipole arm is equal, the linear polarization of the antenna is enhanced, and the coupling between the antenna ports is reduced, so as to achieve the purpose of improving the isolation. At the same time, a pentagonal groove is opened on the dipole arm to improve the impedance matching of the antenna in the high frequency band. The impedance matching and port isolation of the antenna are further improved by introducing parasitic triangular parasitic patches around the dipole arm. Finally, a metal grounding wall is loaded around the dipole to increase the half-power beam width of the antenna radiation pattern. The broadband dual-polarized cross-dipole antenna based on the non-uniform high-impedance surface loaded in the present invention has broadband, low profile, and high isolation.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] A broadband dual-polarized cross-dipole antenna loaded with a non-uniform high-impedance surface, the antenna is composed of a two-layer structure, including a lower dielectric substrate 1 and an upper dielectric substrate 8, the lower dielectric substrate 1 and the upper dielectric substrate 8 are separated by a certain distance and separated by air; the metal part connecting the upper surface and the lower surface of the upper dielectric substrate 8 is an inner conductor through hole 20;

[0006] The upper surface of the lower dielectric substrate 1 is provided with metal, and the metal part of the upper surface includes 16 square patches 2, 24 identical hexagons 3 and 16 isosceles trapezoids 4; the four sides of the lower dielectric substrate 1 are provided with metal grounding walls, and the metal grounding walls include 4 rectangular patches 5; an air medium 6 is provided below the lower dielectric substrate 1, and a metal floor 7 is located below the air medium;

[0007] The upper surface and the lower surface of the upper dielectric substrate 8 are provided with metals respectively, and the metal part of the upper surface includes a left lower arm 10 of a first dipole 9 located at an orientation of θ=﹢45°, a right lower arm 12 of a second dipole 11 located at an orientation of θ=﹣45°, a long microstrip line 13, a short microstrip line 14 and a narrow microstrip line 15; the metal part of the lower surface includes a right upper arm 16 of the first dipole 9 located at an orientation of θ=﹢45°, a left upper arm 17 of the second dipole 11 located at an orientation of θ=﹣45°, four identical triangular parasitic patches 18 and a wide microstrip line 19; the first dipole 9 located at an orientation of θ=﹢45° is composed of a left lower arm 10 and a right upper arm 16; the second dipole 11 located at an orientation of θ=﹣45° is composed of a right lower arm 12 and a left upper arm 17;

[0008] There are two inner conductor through holes 20, and the hole walls are not copper-plated; one of them is located on the long microstrip line 13, and the other is located on the short microstrip line 14; there are two circular holes 21, and the hole walls are copper-plated; one of them is located on the short microstrip line 14, and connects the short microstrip line 14 with the wide microstrip line 19 on the lower surface of the upper dielectric substrate 8, and the other is located on the narrow microstrip line 15, and connects the narrow microstrip line 15 with the wide microstrip line 19 on the lower surface of the upper dielectric substrate 8;

[0009] The first outer conductor 23 of the first coaxial line 22 at the first port passes through the metal floor 7 and the lower dielectric substrate 1 to connect with the left upper arm 17 of the second dipole 11 at the azimuth of θ=-45°; the second outer conductor 25 of the second coaxial line 24 at the second port passes through the metal floor 7 and the lower dielectric substrate 1 to connect with the right upper arm 16 of the first dipole 9 at the azimuth of θ=+45°;

[0010] The first inner conductor 26 of the first coaxial line 22 located at the first port is connected to the right lower arm 12 of the second dipole 11 located at the azimuth of θ=-45° through the inner conductor through hole 20 on the long microstrip line 13 and the long microstrip line 13, and the second inner conductor 27 of the second coaxial line 24 located at the second port is connected to the left lower arm 10 of the first dipole 9 located at the azimuth of θ=+45° through the inner conductor through hole 20 on the short microstrip line 14, the circular hole 21 on the short microstrip line 14, the wide microstrip line 19, the circular hole 21 on the narrow microstrip line 15, and the narrow microstrip line 15;

[0011] In the lower dielectric substrate 1, there is a non-uniform high impedance surface structure, which is formed by a periodic arrangement of non-uniform high impedance surface units; the non-uniform high impedance surface unit is composed of a square patch 2, an isosceles trapezoid 4, a lower dielectric substrate 1, an air medium 6 and a metal floor 7; when a uniform plane wave is incident on the surface of the high impedance surface structure, it is equivalent to a single-port network, where Z 0 is the wave impedance in free space, Z s is the surface impedance.

[0012] Optionally, in the non-uniform high impedance surface structure, the incident direction of the electromagnetic wave is along the -x axis, the directions of the electric field and the magnetic field are along the +z axis and +y axis respectively, and the surface impedance Z s It is expressed as:

[0013]

[0014] According to electromagnetic field theory, the relationship between the incident wave and the reflected wave is obtained:

[0015]

[0016] Where E i and H i They represent the electric field intensity and magnetic field intensity of the incident wave, E r and H r They represent the electric field intensity and magnetic field intensity of the reflected wave respectively;

[0017] According to transmission line theory, the reflection coefficient of this equivalent network is:

[0018]

[0019] The phase difference φ between the incident wave and the reflected wave is expressed as:

[0020]

[0021] When Z s >>Z 0 When φ=0, the incident wave and the reflected wave are in phase, and the surface impedance Z s Set to be much larger than the wave impedance Z in free space 0 , used to reduce the distance between the antenna and the metal reflector and reduce the profile of the antenna;

[0022] When the high impedance surface structure resonates, its surface impedance is infinite, and the resonant frequency corresponds to a reflection phase φ of 0°. The reflection phase φ between [90°, -90°] is in-phase reflection, and the working bandwidth is defined as the frequency range corresponding to the reflection phase φ between [90°, -90°]. The non-uniform high impedance surface unit is equivalent to a simple circuit model. In the simple circuit model, L 1 The inductance represented by the isosceles trapezoid 4, C 1 It is represented by the gap capacitance introduced between adjacent patches, L g is the inductance in the medium, ω is the angular frequency; the resonant frequency f of the non-uniform high impedance surface unit a It is expressed as:

[0023]

[0024] The resonant frequency of the non-uniform high impedance surface structure is adjusted by adjusting the length of the square patch on the surface of the non-uniform high impedance surface unit, the height of the isosceles trapezoidal patch, the distance between the square patch and the isosceles trapezoidal patch, the thickness of the dielectric substrate, and the distance between the dielectric substrate and the metal floor.

[0025] The beneficial effects of the present invention are as follows: the present invention proposes a non-uniform high-impedance surface structure, which has more degrees of freedom in adjusting the resonant frequency and the reflection phase bandwidth. By loading the non-uniform high-impedance surface structure under the cross-dipole antenna, the broadband and low profile of the antenna are achieved. Therefore, the dual-polarized cross-dipole antenna designed based on the high-impedance surface structure in the present invention has a wider bandwidth and a lower profile than the traditional dual-polarized cross-dipole antenna. Secondly, by digging a groove inside one of the arms of the cross-dipole, the impedance matching of the antenna in the high frequency band is improved. At the same time, by introducing a parasitic patch around the dipole, the impedance matching of the antenna in the entire working frequency band is further improved, and the working bandwidth of the antenna is expanded. Finally, a metal grounding wall is loaded around the antenna to expand the beam width of the antenna. Therefore, the dual-polarized antenna designed in the present invention achieves broadband, low profile and high port isolation.

[0026] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0028] Figure 1 It is a schematic diagram of the three-dimensional structure of a broadband low-profile dual-polarized cross-dipole antenna based on a non-uniform high-impedance surface loaded according to the present invention;

[0029] Figure 2 A side view of the structure of a broadband low-profile dual-polarization cross dipole loaded with a non-uniform high-impedance surface according to the present invention;

[0030] Figure 3 A schematic diagram of the feeding structure of a broadband low-profile dual-polarization cross dipole loaded with a non-uniform high-impedance surface according to the present invention;

[0031] Figure 4 Schematic diagram of non-uniform high impedance surface structure;

[0032] Figure 5It is a schematic diagram of a uniform plane wave incident on the surface of a high impedance surface structure;

[0033] Figure 6 It is a schematic diagram of the equivalent circuit of a non-uniform high impedance surface unit;

[0034] Figure 7 The unit structure reflection phase curve diagram of the non-uniform high impedance surface and the classic square high impedance surface;

[0035] Figure 8 Reflection phase of non-uniform high impedance surface unit varies with the square patch length parameter l 1 ;

[0036] Fig. 9 The reflection phase of the non-uniform high impedance surface unit varies with the height size parameter w of the isosceles trapezoidal patch 1 ;

[0037] Fig.10 Variation of the reflection phase of the non-uniform high impedance surface unit with the distance parameter g between the square patch and the isosceles trapezoidal patch;

[0038] Fig.11 The reflection phase of the non-uniform high impedance surface unit varies with the distance between the medium and the metal floor. 2 ;

[0039] Fig.12 The input impedance comparison diagram of the dual-polarized antenna loaded with non-uniform high impedance surface and classic square high impedance surface respectively;

[0040] Fig.13 The S parameter comparison diagram of the dual-polarized antenna loaded with non-uniform high impedance surface and classic square high impedance surface respectively;

[0041] Fig.14 A schematic diagram of the structural evolution of a broadband low-profile dual-polarized cross-dipole antenna based on a non-uniform high-impedance surface loaded according to the present invention;

[0042] Fig.15 It is a comparison diagram of S parameter simulation curves of broadband dual-polarization cross-dipole antenna based on loading non-uniform high impedance surface;

[0043] Fig.16 The comparison diagram of input impedance simulation curves of broadband dual-polarized cross-dipole antenna based on loading non-uniform high impedance surface;

[0044] Fig.17 The S-parameter simulation comparison diagram of the broadband dual-polarized cross-dipole antenna based on a non-uniform high-impedance surface before and after the metal ground wall is introduced;

[0045] Fig.18It is the S parameter simulation curve of the broadband dual-polarized cross-dipole antenna based on the non-uniform high impedance surface;

[0046] Fig.19 The E-plane simulated radiation pattern of the broadband dual-polarized cross-dipole antenna based on the non-uniform high-impedance surface structure loaded in the present invention at a frequency of 2.37 GHz;

[0047] Fig. 20 The E-plane simulated radiation pattern of the broadband dual-polarized cross-dipole antenna based on the non-uniform high-impedance surface structure loaded in the present invention at a frequency of 2.9 GHz;

[0048] Fig.21 The E-plane simulated radiation pattern of the broadband dual-polarized cross-dipole antenna based on the non-uniform high-impedance surface structure loaded in the present invention at a frequency of 3.44 GHz;

[0049] Fig. 22 The H-plane simulation radiation pattern of the broadband dual-polarized cross-dipole antenna based on the non-uniform high-impedance surface structure loaded in the present invention at a frequency of 2.37 GHz;

[0050] Fig.23 The H-plane simulation radiation pattern of the broadband dual-polarized cross-dipole antenna based on the non-uniform high-impedance surface structure loaded in the present invention at a frequency of 2.9 GHz;

[0051] Fig.24 The H-plane simulation radiation pattern of the broadband dual-polarized cross-dipole antenna based on the non-uniform high-impedance surface structure loaded in the present invention at a frequency of 2.44 GHz;

[0052] Fig.25 A gain simulation curve diagram of a broadband dual-polarized cross-dipole antenna based on a non-uniform high-impedance surface structure loaded according to the present invention;

[0053] Fig.26 A three-dimensional structural dimensioning diagram of a specific embodiment sample of a broadband dual-polarized cross-dipole antenna based on a non-uniform high-impedance surface loaded according to the present invention;

[0054] Fig. 27 It is a diagram of the top structural dimensions of a specific embodiment sample of a broadband dual-polarized cross-dipole antenna based on a non-uniform high-impedance surface loaded according to the present invention;

[0055] Fig.28 This is a dimensioned diagram of the intermediate layer structure of a specific embodiment sample of the broadband dual-polarization cross-dipole antenna based on a loaded non-uniform high-impedance surface of the present invention.

[0056] Figure numerals: lower dielectric substrate 1, square patch 2, hexagon 3, isosceles trapezoid 4, rectangular patch 5, air dielectric 6, metal floor 7, upper dielectric substrate 8, first dipole 9, left lower arm 10, second dipole 11, right lower arm 12, long microstrip line 13, short microstrip line 14, narrow microstrip line 15, right upper arm 16, left upper arm 17, triangular parasitic patch 18, wide microstrip line 19, inner conductor through hole 20, circular hole 21, first coaxial line 22, first outer conductor 23, second coaxial line 24, second outer conductor 25, first inner conductor 26, second inner conductor 27. DETAILED DESCRIPTION

[0057] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0058] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0059] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0060] The present invention is based on a broadband low-profile dual-polarized cross-dipole antenna loaded with a non-uniform high-impedance surface, such as Figure 1As shown, the antenna is composed of a two-layer structure. A metal is provided on the upper surface of the lower dielectric substrate 1, and the metal part of the upper surface includes 16 identical square patches 2, 24 identical hexagons 3 and 16 identical isosceles trapezoids 4; a metal grounding wall is provided on the four sides of the lower dielectric substrate 1, and the metal grounding wall includes 4 identical rectangular patches 5; an air medium 6 is provided below the lower dielectric substrate 1, and a metal floor 7 is located below the air medium.

[0061] The upper surface and the lower surface of the upper dielectric substrate 8 are provided with metals, respectively. The metal part of the upper surface includes a left lower arm 10 of the first dipole 9 located at θ=﹢45°, a right lower arm 12 of the second dipole 11 located at θ=﹣45°, a long microstrip line 13, a short microstrip line 14 and a narrow microstrip line 15. The metal part of the lower surface includes a right upper arm 16 of the first dipole 9 located at θ=﹢45°, a left upper arm 17 of the second dipole 11 located at θ=﹣45°, four identical triangular parasitic patches 18 and a wide microstrip line 19. The first dipole 9 located at θ=﹢45° is composed of a left lower arm 10 and a right upper arm 16. The second dipole 11 located at θ=﹣45° is composed of a right lower arm 12 and a left upper arm 17.

[0062] like Figure 1 As shown, there are two inner conductor through holes 20, and the hole walls are not copper-plated. One of them is located on the long microstrip line 13, and the other is located on the short microstrip line 14. There are two circular holes 21, and the hole walls are copper-plated. One of them is located on the short microstrip line 14 and connects the short microstrip line 14 with the wide microstrip line 19 on the lower surface of the upper dielectric substrate 8, and the other is located on the narrow microstrip line 15 and connects the narrow microstrip line 15 with the wide microstrip line 19 on the lower surface of the upper dielectric substrate 8.

[0063] Figure 2 : is a side view of the antenna. The first outer conductor 23 of the first coaxial line 22 at port one passes through the metal floor 7 and the lower dielectric substrate 1 to connect to the left upper arm 17 of the second dipole 11 at the azimuth of θ=﹣45°. The second outer conductor 25 of the second coaxial line 24 at port two passes through the metal floor 7 and the lower dielectric substrate 1 to connect to the right upper arm 16 of the first dipole 9 at the azimuth of θ=﹢45°.

[0064] Figure 3It is a detailed connection diagram of two feeding ports 1 and 2. The first inner conductor 26 of the first coaxial line 22 located at port 1 is connected to the right lower arm 12 of the second dipole 11 located at θ=﹣45° through the inner conductor through hole 20 on the long microstrip line 13 and the long microstrip line 13, and the second inner conductor 27 of the second coaxial line 24 located at port 2 is connected to the left lower arm 10 of the first dipole 9 located at θ=﹢45° through the inner conductor through hole 20 on the short microstrip line 14, the circular hole 21 on the short microstrip line 14, the wide microstrip line 19, the circular hole 21 on the narrow microstrip line 15, and the narrow microstrip line 15.

[0065] Non-uniform high impedance surface structures such as Figure 4 As shown in FIG. 1 , the structure is formed by periodically arranging non-uniform high impedance surface units. The non-uniform high impedance surface unit is composed of a square patch 2, an isosceles trapezoid 4, a lower dielectric substrate 1, an air dielectric 6 and a metal floor 7. Figure 5 The model diagram shows a uniform plane wave incident on the surface of a high impedance surface structure. The model can be equivalent to a single-port network, where Z 0 is the wave impedance in free space, Z s Assume that the incident direction of the electromagnetic wave is along the -x axis, the directions of the electric field and magnetic field are along the +z axis and +y axis respectively, and the surface impedance Z s It can be expressed as:

[0066]

[0067] According to electromagnetic field theory, the relationship between the incident wave and the reflected wave can be obtained:

[0068]

[0069] Where E i and H i They represent the electric field intensity and magnetic field intensity of the incident wave, E r and H r They represent the electric field intensity and magnetic field intensity of the reflected wave respectively.

[0070] According to transmission line theory, the reflection coefficient of this equivalent network is:

[0071]

[0072] The phase difference (reflection phase) φ between the incident wave and the reflected wave can be expressed as:

[0073]

[0074] According to the above expression, when Z s >>Z 0When φ=0, the incident wave and the reflected wave are in phase. Using this characteristic, the surface impedance Z s Set to be much larger than the wave impedance Z in free space 0 , which can effectively reduce the distance between the antenna and the metal reflector, thereby reducing the profile of the antenna.

[0075] When the high impedance surface structure resonates, its surface impedance is infinite, and the resonant frequency corresponds to a reflection phase φ of 0°. The reflection phase φ between [90°, -90°] is in-phase reflection, and the working bandwidth is defined as the frequency range (in-phase reflection bandwidth) corresponding to the reflection phase φ between [90°, -90°]. The non-uniform high impedance surface unit can be equivalent to Figure 6 The simple circuit model shown. Where L 1 The inductance represented by the isosceles trapezoid 4, C 1 It is represented by the gap capacitance introduced between adjacent patches, L g is the inductance in the medium, and ω is the angular frequency. The resonant frequency f of the non-uniform high impedance surface unit a It can be expressed as

[0076]

[0077] Therefore, the resonant frequency of the non-uniform high impedance surface structure can be adjusted by adjusting the length of the square patch on the surface of the non-uniform high impedance surface unit, the height of the isosceles trapezoidal patch, the distance between the square patch and the isosceles trapezoidal patch, the thickness of the dielectric substrate, and the distance between the dielectric substrate and the metal floor.

[0078] The reflection phase of the non-uniform high impedance surface unit and the classic square high impedance surface unit of the same size is extracted by the electromagnetic simulation software HFSS. Figure 7 As shown in the figure, the two curves are basically similar, and the in-phase reflection bandwidth is 3.23GHz-4.67GHz. The resonance frequency corresponding to the zero reflection phase of the non-uniform high impedance surface unit is 4GHz. Figure 8 to Figure 11 It is shown that the reflection phase of the non-uniform metasurface unit varies with the length l of the square patch on the surface 1 , the height w of the isosceles trapezoidal patch 1 , the distance g between the surface square patch and the isosceles trapezoidal patch, and the distance h between the dielectric substrate and the metal floor 2 Simulation results of the changes, where the size of the metasurface unit is shown in Figure 26-27 In. By Figure 8 to Figure 11 It can be seen that as the length of the square patch l 1 , the height w of the isosceles trapezoidal patch 1 , and the distance h between the dielectric substrate and the metal floor 2As the distance g between the surface square patch and the isosceles trapezoidal patch increases, the resonant frequency and the reflection phase bandwidth gradually move to low frequencies. As the distance g between the surface square patch and the isosceles trapezoidal patch increases, the resonant frequency and the reflection phase bandwidth gradually move to high frequencies. Therefore, compared with the classic high-impedance surface structure, the non-uniform high-impedance surface structure has more degrees of freedom in adjusting the resonant frequency and reflection phase bandwidth, which also provides more degrees of freedom in adjusting the overall impedance matching when the non-uniform high-impedance surface structure is integrated with the cross-dipole antenna. In order to verify the performance of the designed non-uniform high-impedance surface structure, the non-uniform high-impedance surface structure and the classic square high-impedance surface structure with the same size are simultaneously loaded under the cross-dipole antenna. The input impedance and S parameters of the antenna are shown in Figure 2. Fig.12 and Fig.13 As shown, the antenna input impedance Fig.12 It can be seen that the input resistance of the antenna loaded with the non-uniform high impedance surface structure is closer to 50 ohms in the working frequency band 2.26-3.83 GHz than that of the antenna loaded with the classic high impedance surface square structure, and the input resistance changes relatively smoothly, and the input reactance is also closer to 0 ohms. Therefore, the antenna loaded with the non-uniform high impedance surface structure has a wider impedance bandwidth, such as Fig.13 Medium|S 11 |Parameters are shown. It can also be seen from the figure that the antenna port isolation loaded with the non-uniform high impedance surface structure is greater than 30dB within the working bandwidth.

[0079] The broadband low-profile dual-polarization cross-dipole antenna loaded with a non-uniform high-impedance surface designed by the present invention can be evolved from a first antenna to a second antenna, then from the second antenna to a third antenna, and finally from the third antenna. The evolution process is as follows: Fig.14 As shown, in order to compare the impedance bandwidth and S parameters of the four antennas, Fig.15 and Fig.16 The S parameter diagrams and input impedance diagrams of the first antenna, the second antenna, the third antenna and the antenna proposed in this paper are shown respectively. The first antenna comprises two layers, the lower layer comprises a non-uniform high impedance surface, and the upper layer comprises a pair of orthogonal dipoles and a dielectric substrate, and the dipoles are fed by a coaxial line. It can be seen from the simulation results that the first antenna has an S parameter diagram and an input impedance diagram within the working frequency band of 2.65GHz-3.27GHz. 11 | is greater than -10dB, and the port isolation is less than 30dB in the low frequency band 2.25GHz-2.7GHz. Therefore, the impedance matching and port isolation of the first antenna need to be further improved.

[0080] Therefore, in order to improve the impedance matching of the antenna, the second antenna cuts the four arms of the cross dipole based on the first antenna. Fig.15From the S parameters of the second antenna, it can be seen that the angle cutting expands the impedance bandwidth of the second antenna in the low frequency band and improves the port isolation of the antenna in the low frequency band. However, at this time, the |S 11 | is still greater than -10dB, so a hexagonal part is dug out from one of the arms of the cross dipole to obtain the third antenna. Due to the internal grooving of the cross dipole, the surface current distribution of the dipole near 3.45GHz is changed, thereby improving the impedance matching of the second antenna in the high frequency band. However, the third antenna has a |S 11 | is still greater than -10dB. Therefore, on the basis of the third antenna, four triangular parasitic patches are loaded near the cross dipole, and at the same time, four metal ground walls are loaded around the antenna to obtain the antenna proposed by the present invention. In general, when a parasitic patch is introduced around a single dipole, the resonant length of the dipole will increase. This shows that the parasitic patch will reduce the electrical length of the dipole, causing the capacitive reactance part of the input impedance of the dipole to increase or the inductive reactance part to decrease, but introducing a parasitic patch in a broadband dual-polarized antenna will cause the input reactance of the antenna to fluctuate between the capacitive reactance and the inductive reactance. From Fig.16 It can be seen that due to the introduction of the parasitic patch, the inductive part of the input impedance of the second antenna in the higher frequency band is reduced to near zero, and the inductive reactance change becomes relatively gentle in the higher frequency band. At the same time, the parasitic patch also reduces the resistive part of the input impedance in the higher frequency band to near 50 ohms. This improves the impedance matching of the second antenna in the higher frequency band. In addition, loading a metal ground wall around the antenna has the effect of widening the radiation pattern. The half-power beamwidth is used to evaluate the characteristics of the antenna radiation pattern. At the same time, the XZ plane is defined as the horizontal plane (H plane), the YX plane is defined as the vertical plane (E plane), and the two pairs of crossed dipoles are symmetrical about the E plane. Fig.17 The half-power beamwidth of dipole 1 before and after the metal ground wall is loaded is shown. As can be seen from the figure, when the metal ground wall is loaded, the half-power beamwidth of the antenna increases significantly in the low frequency band.

[0081] The broadband low-profile dual-polarized cross-dipole antenna loaded with a non-uniform high-impedance surface designed by the present invention has a wider impedance bandwidth and a lower profile than the traditional dual-polarized cross-dipole antenna. The broadband low-profile dual-polarized cross-dipole antenna loaded with a non-uniform high-impedance surface designed by the present invention adjusts the impedance matching of the antenna by changing the size and position of the parasitic patch and the internal slot of the dipole arm, thereby increasing the impedance bandwidth of the antenna. By changing the size of the dipole arm cut angle, the isolation between the antenna ports is improved and the impedance matching of the antenna is adjusted. By changing the height of the metal ground wall around the dipole, the beam width of the antenna is expanded. The dual-polarized antenna designed in the present invention achieves broadband and low profile while also having high port isolation.

[0082] The broadband low-profile dual-polarized cross-dipole antenna embodiment sample loaded with non-uniform high-impedance surface has an operating center frequency of 3 GHz, and both the upper and lower dielectric substrates are FR4 dielectric substrates with a relative dielectric constant of 4.4. The thicknesses of the lower and upper dielectric substrates are 1.2 mm and 1 mm respectively. The overall size of the antenna is 100 mm×100 mm×14 mm.

[0083] The cross-section of the broadband dual-polarized cross-dipole antenna loaded with a non-uniform high impedance surface in the embodiment is 14 mm, i.e. 0.14λ g , where λ g Indicates the operating wavelength when the operating frequency is 3 GHz. Compared with the traditional planar cross dipole antenna whose height from the metal reflector is usually 0.25 to 0.5 wavelengths, the cross section of this antenna is only 0.14 wavelengths, so this antenna has low profile performance.

[0084] The S parameter and input impedance curves corresponding to the structure evolution of the broadband low-profile dual-polarization cross-dipole antenna loaded with a non-uniform high-impedance surface of the present invention are shown in FIG. Fig.15 and Fig.16 As shown in the figure, the simulation software used is the full-wave electromagnetic simulation software HFSS. It can be seen that by cutting the dipole angle, the impedance matching of the antenna in the 2.3GHz-2.8GHz frequency band is improved. By slotting the inside of the dipole, the impedance matching of the antenna in the 3GHz-3.8GHz frequency band is improved. At the same time, the isolation between the antenna ports meets the requirement of greater than 30dB in the entire frequency band. By loading parasitic patches around the dipole, the impedance matching of the antenna in the entire working frequency band is optimized, making the antenna's |S 11 | Less than -10dB in the entire operating frequency band. By loading a metal ground wall around the antenna, the half-power beamwidth of the antenna in the 2.3GHz-3.5GHz frequency band is increased, such as Fig.17 shown.

[0085] Fig.18 This is a simulation curve of the S parameters of the sample of the embodiment of the present invention. When the port 1 and the port 2 are excited, the polarization directions of the antenna are φ=﹢45° and φ=﹣45° respectively. 11 | represents the modulus of the reflection coefficient at the antenna input port, |S 21 | represents the module value of the isolation between antenna port 1 and port 2. According to the simulation results, in the frequency band range of 2.26GHz-3.83GHz, |S 11 | is less than -10dB, and the impedance bandwidth is 51.5%. This shows that the sample antenna of the embodiment has broadband characteristics. 21|<-30dB, that is, the isolation between the ports is greater than 30dB. This shows that the two signal input ports of the sample antenna of this embodiment have high isolation. The sample antenna of the embodiment of the present invention has good performance in the frequency band range of 2.26GHz-3.83GHz, and the relative bandwidth is 51.7%. In this frequency band, |S 11 | are all less than -10dB, |S 21 |Less than -30dB.

[0086] The E-plane and H-plane directional diagrams of the broadband low-profile dual-polarization cross-dipole antenna embodiment sample loaded with a non-uniform high-impedance surface of the present invention are as follows: Figure 19 to Figure 24 As shown, it can be seen that the cross-polarization level of the antenna is less than -30dB in the working frequency band, indicating that the antenna of this embodiment has a good cross-polarization level. The front-to-back ratio is greater than 19dB. Fig.25 The gain simulation curve of the sample of the embodiment of the present invention is shown in FIG. 1. In the working frequency band, the average gain of the antenna is 9.45 dBi, the maximum gain of the antenna occurs at 3.5 GHz, the gain is 10.7 dBi, and the gain fluctuation in the frequency band is 2 dBi.

[0087] The specific dimensions of the embodiment sample of the broadband low-profile dual-polarized cross-dipole antenna based on the non-uniform high-impedance surface loaded according to the present invention are as follows: Figure 26 to Figure 28 As shown in , the dimensions of each part of the specific structure are shown in Table 1.

[0088] Table 1 Dimensions of various parts of the antenna sample of the present invention (unit: mm)

[0089] symbol Numeric symbol Numeric <![CDATA[l 1 ]]> 7.0 <![CDATA[w 1 ]]> 0.7 <![CDATA[l 2 ]]> 16.5 <![CDATA[w 2 ]]> 10.0 <![CDATA[l 3 ]]> 32.2 <![CDATA[w 3 ]]> 80.0 <![CDATA[l 4 ]]> 20.0 <![CDATA[w 4 ]]> 12.5 <![CDATA[l 5 ]]> 80.0 <![CDATA[h 1 ]]> 1.2 <![CDATA[l 6 ]]> 100.0 <![CDATA[h 2 ]]> 4.0 <![CDATA[l 7 ]]> 10.4 <![CDATA[h 3 ]]> 1.0 <![CDATA[l 8 ]]> 9.0 <![CDATA[h 4 ]]> 6.1 <![CDATA[l 9 ]]> 20.0 <![CDATA[h 5 ]]> 11.0 <![CDATA[l 10 ]]> 6.0 <![CDATA[r 1 ]]> 0.5 <![CDATA[l 11 ]]> 5.1 <![CDATA[r 2 ]]> 0.5 <![CDATA[l 12 ]]> 8.3

[0090] The combination of the figure and the above analysis shows that the embodiment sample of the broadband low-profile dual-polarized cross-dipole antenna based on the non-uniform high-impedance surface loaded in the present invention has broadband and low profile, and also has high port isolation.

[0091] It is emphasized here that the above embodiment is only a better application mode of the present invention and does not limit the protection scope of the present invention. Any modification, replacement and improvement of the present invention are included in the protection scope of the present invention.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A broadband dual-polarized cross-dipole antenna loaded with a non-uniform high impedance surface. Features: The antenna is composed of a two-layer structure, including a lower dielectric substrate (1) and an upper dielectric substrate (8), wherein the lower dielectric substrate (1) and the upper dielectric substrate (8) are separated by a certain distance and air. The metal portion connecting the upper surface and the lower surface of the upper dielectric substrate (8) is an inner conductor through hole (20); The upper surface of the lower dielectric substrate (1) is provided with metal, and the metal portion of the upper surface includes 16 square patches (2), 24 identical hexagons (3) and 16 isosceles trapezoids (4); the four sides of the lower dielectric substrate (1) are provided with metal grounding walls, and the metal grounding walls include 4 rectangular patches (5); an air medium (6) is provided below the lower dielectric substrate (1), and a metal floor (7) is located below the air medium; The upper surface and lower surface of the upper dielectric substrate (8) are provided with metal respectively. The metal portion of the upper surface comprises a left lower arm (10) of a first dipole (9) located at an orientation of θ=﹢45°, a right lower arm (12) of a second dipole (11) located at an orientation of θ=﹣45°, a long microstrip line (13), a short microstrip line (14) and a narrow microstrip line (15); the metal portion of the lower surface comprises a first dipole located at an orientation of θ=﹢45° The first dipole (9) is composed of a right upper arm (16), a left upper arm (17) of a second dipole (11) located at an angle of θ = -45°, four identical triangular parasitic patches (18) and a wide microstrip line (19); the first dipole (9) located at an angle of θ = +45° is composed of a left lower arm (10) and a right upper arm (16); the second dipole (11) located at an angle of θ = -45° is composed of a right lower arm (12) and a left upper arm (17); There are two inner conductor through holes (20), the hole walls are not copper-plated; one of them is located on the long microstrip line (13), and the other is located on the short microstrip line (14); there are two circular holes (21), the hole walls are copper-plated; one of them is located on the short microstrip line (14), and connects the short microstrip line (14) with a wide microstrip line (19) on the lower surface of the upper dielectric substrate (8); the other is located on the narrow microstrip line (15), and connects the narrow microstrip line (15) with the wide microstrip line (19) on the lower surface of the upper dielectric substrate (8); The first outer conductor (23) of the first coaxial line (22) located at port one passes through the metal floor (7) and the lower dielectric substrate (1) to be connected to the left upper arm (17) of the second dipole (11) located at the azimuth of θ=-45°; the second outer conductor (25) of the second coaxial line (24) located at port two passes through the metal floor (7) and the lower dielectric substrate (1) to be connected to the right upper arm (16) of the first dipole (9) located at the azimuth of θ=+45°; The first inner conductor (26) of the first coaxial line (22) located at port one is connected to the right lower arm (12) of the second dipole (11) located at an orientation of θ=-45° through the inner conductor through hole (20) on the long microstrip line (13) and the long microstrip line (13); the second inner conductor (27) of the second coaxial line (24) located at port two is connected to the left lower arm (10) of the first dipole (9) located at an orientation of θ=-45° through the inner conductor through hole (20) on the short microstrip line (14), the circular hole (21) on the short microstrip line (14), the wide microstrip line (19), the circular hole (21) on the narrow microstrip line (15), and the narrow microstrip line (15); In the lower dielectric substrate (1), there is a non-uniform high impedance surface structure, which is formed by a periodic arrangement of non-uniform high impedance surface units; the non-uniform high impedance surface unit is composed of a square patch (2), an isosceles trapezoid (4), a lower dielectric substrate (1), an air medium (6) and a metal floor (7); when a uniform plane wave is incident on the surface of the high impedance surface structure, it is equivalent to a single-port network, wherein Z 0 is the wave impedance in free space, Z s is the surface impedance.

2. The broadband dual-polarized cross-dipole antenna loaded with a non-uniform high impedance surface according to claim 1, Features: In the non-uniform high impedance surface structure, the incident direction of the electromagnetic wave is along the -x axis, the directions of the electric field and the magnetic field are along the +z axis and +y axis respectively, and the surface impedance Z s It is expressed as: According to electromagnetic field theory, the relationship between the incident wave and the reflected wave is obtained: Where E i and H i They represent the electric field intensity and magnetic field intensity of the incident wave, E r and H r They represent the electric field intensity and magnetic field intensity of the reflected wave respectively; According to transmission line theory, the reflection coefficient of this equivalent network is: The phase difference φ between the incident wave and the reflected wave is expressed as: When Z s >>Z 0 When φ=0, the incident wave and the reflected wave are in phase, and the surface impedance Z s Set to be much larger than the wave impedance Z in free space 0 , used to reduce the distance between the antenna and the metal reflector and reduce the profile of the antenna; When the high impedance surface structure resonates, its surface impedance is infinite, and the resonant frequency corresponds to a reflection phase φ of 0°. The reflection phase φ between [90°, -90°] is in-phase reflection, and the working bandwidth is defined as the frequency range corresponding to the reflection phase φ between [90°, -90°]. The non-uniform high impedance surface unit is equivalent to a simple circuit model. In the simple circuit model, L 1 The inductance represented by the isosceles trapezoid (4), C 1 It is represented by the gap capacitance introduced between adjacent patches, L g is the inductance in the medium, ω is the angular frequency; the resonant frequency f of the non-uniform high impedance surface unit a It is expressed as: The resonant frequency of the non-uniform high impedance surface structure is adjusted by adjusting the length of the square patch on the surface of the non-uniform high impedance surface unit, the height of the isosceles trapezoidal patch, the distance between the square patch and the isosceles trapezoidal patch, the thickness of the dielectric substrate, and the distance between the dielectric substrate and the metal floor.

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