A quad-polarized high-isolation MIMO array antenna

Abstract

The application provides a quadrupole high-isolation MIMO array antenna, which comprises a dielectric substrate, a metal floor printed on the upper surface of the dielectric substrate and N feed networks on the lower surface, N is greater than or equal to 2, a decoupling baffle fixed on the upper surface of the dielectric substrate and N periodically arranged dual-polarized dipole radiating units, and the feed structure of the dual-polarized dipole radiating unit is connected with the output end of the feed network; the feed network comprises two Wilkinson power dividers, two pi-type attenuators connected with four output ends of each Wilkinson power divider, one Schumann phase shifter and three branch line couplers; when two input ends of one of the branch line couplers and the outer input ends of the other two branch line couplers are simultaneously fed, the linear polarization characteristics of 0°, 90°, -45° and 45° can be simultaneously realized on one dual-polarized dipole radiating unit connected with the output end of the feed network, and the defect of complex antenna structure in the prior art is solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of antennas, and relates to a four-polarization antenna, in particular to a four-polarization high-isolation MIMO array antenna, which can be used in the field of mobile communication. BACKGROUND

[0002] With the wide application of wireless communication technology, the demand for channel capacity is increasing, and the multiple-input-multiple-output (MIMO) antenna can increase the channel capacity and the reliability of signals without increasing the spectrum resources, the MIMO array antenna can maximize the spatial dimension resources to provide wireless communication services for more users, has a stronger spatial signal processing capability, and has the advantages of greatly increasing the channel capacity, improving the efficiency, reducing the time delay and the like. With the continuous development of 5G technology, the demand for multi-functional communication is becoming more and more important, and four-polarization is widely used in multi-functional communication systems due to the advantages of increasing the channel capacity, reducing the cost of the communication system and preventing channel fading.

[0003] Most of the traditional MIMO antennas change the polarization mode of the electromagnetic wave radiated by the antenna by loading adjustable artificial electromagnetic structures on the elements such as dipole, slot antenna and microstrip antenna to realize left and right circular polarization and two linear polarizations, and cannot realize four linear polarizations. In order to overcome this defect, researchers have made different attempts, for example, in the patent application with the application publication number CN102800996 A and the name of "MIMO array antenna with multiple polarization modes", a four-linear polarization MIMO array antenna is disclosed, which comprises one or more four-linear polarization linear arrays, wherein each four-linear polarization linear array comprises a vertical-horizontal dual-polarization linear array and a ±45° dual-polarization linear array arranged side by side, the vertical-horizontal dual-polarization linear array comprises one or more vertical-horizontal dual-polarization dipoles, the ±45° dual-polarization linear array comprises the same number of ±45° dual-polarization dipoles, each vertical-horizontal dual-polarization linear array and ±45° dual-polarization linear array is mounted on a metal reflector plate, and all the metal reflector plates are connected to form a whole, the invention can realize four linear polarizations of 0° / 90° / ±45°, but two columns of vertical-horizontal dual-polarization array antennas and ±45° dual-polarization array antennas are needed to realize four linear polarizations, resulting in a complex structure of the antenna. SUMMARY

[0004] The application aims to overcome the shortcomings of the prior art, and provides a four-polarization high-isolation MIMO array antenna, which simplifies the structure of the four-linear polarization MIMO array antenna under the premise of ensuring high isolation.

[0005] To achieve the above objectives, the technical solution adopted by the present invention includes a dielectric substrate 1, a metal ground plane 2 printed on the upper surface of the dielectric substrate 1, and N feed networks 3 on the lower surface, where N≥2; the upper surface of the dielectric substrate 1 is fixed with a linear radiation array composed of N periodically arranged bipolar dipole radiation units 4, the same number as the feed networks 3, a longitudinal decoupling baffle 5 fixed on both sides of the linear radiation array and distributed along the arrangement direction of the N radiation units 4, and a transverse decoupling baffle 6 disposed on both sides of each radiation unit 4;

[0006] The power supply network 3 includes a first branch line coupler 31 and two parallel second branch line couplers 32. The input terminals of the two second branch line couplers 32 are respectively connected to the two output terminals of the first branch line coupler 31. A Schiffman phase shifter 33 is loaded between one output terminal of the first branch line coupler 31 and the input terminal of the second branch line coupler 32. A U-shaped stub 34 is printed on the inner side of the outer output terminal of the second branch line coupler 32. The outer output terminal of the second branch line coupler 32 is connected to a Wilkinson power divider 35. Each of the four output terminals of the Wilkinson power divider 35 is connected to two π-type attenuators 36.

[0007] The first input terminal P1 and the second input terminal P2 of the first branch line coupler 31, and the two external input terminals P3 of the second branch line coupler 32, respectively serve as the input terminals of the feed network 3; the two feed structures of the dual-polarized dipole radiation unit 4 are respectively connected to the two internal output terminals P4 of the second branch line coupler (32) at their corresponding positions.

[0008] By feeding the first input terminal P1 and the second input terminal P2 of the first branch line coupler 31, 0° and 90° polarization characteristics can be achieved; by feeding the external input terminal P3 of the second branch line coupler 32 connected to the Scheffman phase shifter 33, -45° polarization characteristics can be achieved; by feeding the external input terminal P3 of another second branch line coupler 32, 45° polarization characteristics can be achieved; when all four input terminals of the feeding network 3 are fed simultaneously, 0°, 90°, -45° and 45° linear polarization characteristics can be achieved.

[0009] The aforementioned quad-polarized high-isolation MIMO array antenna, wherein the dual-polarized dipole radiating element 4 includes two vertically intersecting radiating dielectric plates 41. Each radiating dielectric plate 41 has a T-shaped dipole radiating arm 42 with isosceles triangular structures at both ends of the transverse arm printed on one plate surface, and an inverted L-shaped microstrip feed line 43 with a feeding structure printed on the other plate surface. The T-shaped dipole radiating arms 42 printed on the two radiating dielectric plates 41 do not contact each other.

[0010] In the aforementioned quad-polarized high-isolation MIMO array antenna, the longitudinal decoupling baffles 5 fixed on both sides of the linear radiating array are symmetrical about the central axis of the linear radiating array, and the longitudinal decoupling baffles 5 are tilted away from the linear radiating array at an angle of 45°.

[0011] The aforementioned quad-polarized high-isolation MIMO array antenna, wherein the lateral decoupling baffle 6 adopts an isosceles trapezoidal structure with two waists that are perpendicularly connected to two longitudinal decoupling baffles 5 respectively.

[0012] The aforementioned quad-polarized high-isolation MIMO array antenna includes a Wilkinson power divider 35 comprising a first 1-to-2 Wilkinson power divider and a second 1-to-2 Wilkinson power divider with the same structure as the first 1-to-2 Wilkinson power divider and connected to each output terminal of the first 1-to-2 Wilkinson power divider; isolation resistors 351, each with a capacity of 100Ω, are applied between the output terminals of the three 1-to-2 Wilkinson power dividers.

[0013] The aforementioned quad-polarized high-isolation MIMO array antenna includes a π-type attenuator 36 comprising a π-type microstrip stub 361 and three patch resistors 362 loaded thereon, as well as a plurality of metallized vias 363 penetrating the dielectric substrate 1 for connecting the π-type microstrip stub 361 to the metal ground plane 2.

[0014] In the aforementioned quad-polarized high-isolation MIMO array antenna, the Schoffman phase shifter 33 adopts a U-shaped microstrip structure with its bottom near the external input terminal P3 of the second branch line coupler 32, and its length is equal to 1 / 4 of the wavelength λ of the MIMO array antenna.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. The feeding network constructed in this invention includes three branch line couplers. The two input terminals of one branch line coupler and the external input terminals of the other two branch line couplers are used as the four input ports of the feeding network. By simultaneously feeding the four input terminals of the feeding network, linear polarization characteristics of 0°, 90°, -45° and 45° can be achieved simultaneously on a dual-polarized dipole radiating element, avoiding the structural complexity caused by the need to use two antenna arrays to achieve four-line polarization in the prior art.

[0017] 2. The feed network constructed in this invention includes two Wilkinson power dividers and two π-type attenuators connected to the four output terminals of each Wilkinson power divider. By utilizing the signal attenuation function of the π-type attenuators, excess power in the feed network can be absorbed, avoiding standing wave degradation caused by signal reflection. At the same time, combined with the decoupling baffles set around the linear radiation array to block radiated electromagnetic waves, the antenna isolation is improved. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of the present invention;

[0019] Figure 2 This is a schematic diagram of the structure of the radiation unit of the present invention;

[0020] Figure 3 This is a schematic diagram of the decoupling baffle of the present invention;

[0021] Figure 4 This is a schematic diagram of the power supply network structure of the present invention;

[0022] Figure 5 This is a schematic diagram of the π-type attenuator of the present invention;

[0023] Figure 6 The graph shows the reflection coefficient curve of the input port in the 1.785-1.805 GHz frequency band, which is a specific embodiment of the present invention.

[0024] Figure 7 This is a graph showing the isolation between input ports in the 1.785-1.805 GHz frequency band, representing a specific embodiment of the present invention.

[0025] Figure 8 This is a diagram of the E-plane main polarization and cross-polarization corresponding to a main polarization of 90° at a frequency of 1.795 GHz, according to a specific embodiment of the present invention.

[0026] Figure 9 This is a diagram of the E-plane main polarization and cross-polarization corresponding to a main polarization of 0° at a frequency of 1.795 GHz, according to a specific embodiment of the present invention.

[0027] Figure 10 The diagram shows the E-plane main polarization and cross-polarization corresponding to a 45° main polarization at a frequency of 1.795 GHz in a specific embodiment of the present invention.

[0028] Figure 11 The diagram shows the E-plane main polarization and cross-polarization corresponding to a main polarization of -45° at a frequency of 1.795 GHz, as shown in a specific embodiment of the present invention. Detailed Implementation

[0029] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0030] Reference Figures 1-3The present invention includes a dielectric substrate 1 with a dielectric constant of 4.4, a length of 260 mm, a width of 160 mm, and a thickness of 1 mm. A metal ground plane 2 is printed on the upper surface of the dielectric substrate 1, and N feed networks 3, where N = 3, are printed on the lower surface of the dielectric substrate 1. A linear radiation array is fixed on the upper surface of the dielectric substrate 1, consisting of N bipolarized dipole radiating units 4 arranged periodically with a period of 86 mm, the same number as the feed networks 3. Each bipolarized dipole radiating unit 4 includes two perpendicularly intersecting radiating dielectrics. The radiating dielectric plate 41 is composed of two mutually perpendicular rectangular dielectric plates with a dielectric constant of 3, a length of 78 mm, a height of 45.5 mm, and a thickness of 0.8 mm. Each rectangular dielectric plate has two dielectric blocks cut from its lower part, each with a length of 22 mm, a height of 25 mm, and a thickness of 0.8 mm. Each radiating dielectric plate 41 has a T-shaped dipole radiating arm 42 printed on one surface, with both ends of the transverse arm being isosceles triangular structures. The transverse arm of the T-shaped dipole radiating arm 42 is cut into an isosceles triangular structure with a side length of 4.2 mm, radiating the radiating unit 4. Arm cutting improves the isolation of the radiating unit 4. After cutting, the height of the T-shaped dipole radiating arm 42 is 44.5 mm and the lateral arm length is 73.4 mm. The T-shaped dipole radiating arms 42 printed on the two radiating dielectric substrates 41 do not contact each other. A feeding structure of an inverted L-shaped microstrip feed line 43 is printed on the other side of each radiating dielectric substrate 41. A longitudinal decoupling baffle 5 is fixed on the upper surface of the dielectric substrate 1, symmetrical about the central axis of the linear radiating array, and distributed along the arrangement direction of the N radiating units 4. The length of the longitudinal decoupling baffle 5 is 26 mm. The antenna has a diameter of 0 mm, a width of 64 mm, a thickness of 0.8 mm, and is tilted away from the linear radiation array at an angle of 45°. A transverse decoupling baffle 6 with a height of 28 mm is also present on both sides of each radiation element 4. This transverse decoupling baffle 6 is an isosceles trapezoidal structure with two sides perpendicularly connected to two longitudinal decoupling baffles 5. The lower side of the isosceles trapezoidal structure is 68 mm long, and the upper side is 108 mm long. The longitudinal decoupling baffles 5 and the transverse decoupling baffles 6 can effectively improve the path of reflected waves, reduce interference between dual-polarized dipole radiation elements, and improve antenna isolation.

[0031] Reference Figure 4 and 5The feed network 3 includes a first branch line coupler 31 and two parallel second branch line couplers 32. The input terminals of the two second branch line couplers 32 are respectively connected to the two output terminals of the first branch line coupler 31. A Schiffman phase shifter 33 is loaded between one output terminal of the first branch line coupler 31 and the input terminal of the second branch line coupler 32. The Schiffman phase shifter 33 adopts a U-shaped microstrip structure with its bottom near the external input terminal P3 of the second branch line coupler 32. Its length is equal to 1 / 4 of the wavelength λ of the MIMO array antenna, and it is used to generate a 90° phase lag. A U-shaped stub 34 is printed on the inner side of the external output terminal of the second branch line coupler 32. The U-shaped stub 34 is used to adjust the signal reflection and improve impedance matching. The external output terminal of the second branch line coupler 32 is connected to a Wilkinson power divider 35. Each of the four output terminals of the Wilkinson power divider 35 is connected to two π-type attenuators 36.

[0032] The first input terminal P1 and the second input terminal P2 of the first branch line coupler 31, and the two external input terminals P3 of the second branch line coupler 32, respectively serve as the input terminals of the feed network 3; the two internal output terminals P4 of the second branch line coupler 32 serve as the output terminals of the feed network 3, and are connected to the feed structure of the inverted L-shaped microstrip feed line 43 of the radiating unit 4.

[0033] The Wilkinson power divider 35 includes a first 1-to-2 Wilkinson power divider, a second 1-to-2 Wilkinson power divider with the same structure as the first 1-to-2 Wilkinson power divider and connected to the external output terminal of the first 1-to-2 Wilkinson power divider, and a second 1-to-2 Wilkinson power divider connected to the internal output terminal of the first 1-to-2 Wilkinson power divider; isolation resistors 351 of 100Ω are applied between the output terminals of the three 1-to-2 Wilkinson power dividers.

[0034] The four output terminals of the Wilkinson power divider 35 are of equal amplitude and in phase. The purpose of using the Wilkinson power divider 35 with four output terminals is to reduce the power loss on each branch so that it does not exceed the rated power of the chip resistor 362 on the π-type attenuator 36, and to avoid damage to the power supply network 3.

[0035] The π-type attenuator 36 includes a π-type microstrip stub 361 and three patch resistors 362 loaded thereon, as well as multiple metallized vias 363 penetrating the dielectric substrate 1 to connect the π-type microstrip stub 361 to the metal ground plane 2. By utilizing the signal attenuation function of the π-type attenuator, excess power in the feed network 3 can be absorbed, avoiding standing wave degradation caused by signal reflection. At the same time, combined with the decoupling baffles set around the linear radiating array to block radiated electromagnetic waves, the antenna isolation is improved.

[0036] The working principle of this invention is as follows: When the input terminal P1 of the first branch line coupler 31 is powered, the output terminal of the first branch line coupler 31 without the Schiffman phase shifter 33 is 90° out of phase compared to the output terminal with the Schiffman phase shifter 33. Since a Schiffman phase shifter 33 is loaded between one output terminal of the first branch line coupler 31 and the internal input terminal of the second branch line coupler 32, and the Schiffman phase shifter 33 produces a 90° phase lag, the two internal input terminals of the second branch line coupler 32 are in phase. Therefore, the internal output terminal P4 of the second branch line coupler 32 is in phase, and the +45° polarized dipole antenna and the -45° polarized dipole antenna of equal amplitude and in phase are combined to form a 0° polarization mode.

[0037] When the input terminal P2 of the first branch line coupler 31 is powered, the output terminal of the first branch line coupler 31 connected to the Schiffman phase shifter 33 lags behind the output terminal without the Schiffman phase shifter 33 by 90°. Since the Schiffman phase shifter 33 is loaded between one output terminal of the first branch line coupler 31 and the internal input terminal of the second branch line coupler 32, and the Schiffman phase shifter 33 produces a phase lag of 90°, the two internal input terminals of the second branch line coupler 32 are 180° out of phase. Therefore, the internal output terminal P4 of the second branch line coupler 32 is 180° out of phase. Thus, the +45° polarized dipole antenna and the -45° polarized dipole antenna, which are of equal amplitude and 180° out of phase, combine to form a 90° polarization mode.

[0038] When the input terminal P3 of the second branch line coupler 32 connected to the Schiffman phase shifter 33 is powered, the output terminal P4 of the second branch line coupler 32 connected to the Schiffman phase shifter 33 is directly connected to the -45° polarized dipole antenna, thus generating a -45° polarization mode.

[0039] When the other input terminal P3 of the second branch line coupler 32 is powered, the other output terminal P4 of the second branch line coupler 32 is directly connected to the 45° polarized dipole antenna, generating a 45° polarization mode.

[0040] When the input terminals P1 and P2 of the first branch line coupler 31 and the input port P3 of the second branch line coupler 32 are simultaneously powered, four polarizations can be simultaneously realized on the dual-polarization radiation unit connected at the inner output terminal P4 of the second branch line coupler 32.

[0041] The technical effects of the present invention will be further explained below with reference to simulation experiments:

[0042] 1. Simulation conditions and content:

[0043] The above embodiments were simulated using HFSS (High Frequency Structure Simulation).

[0044] Simulation 1 simulates the reflection coefficient of a specific embodiment in the 1.75-1.85 GHz range, and the results are as follows. Figure 6 As shown;

[0045] Simulation 2 simulates the port isolation of a specific embodiment at 1.75-1.85 GHz, and the results are as follows. Figure 7 As shown;

[0046] Simulation 3 simulates the E-plane principal polarization and cross-polarization diagrams corresponding to the principal polarizations of 90°, 0°, 45°, and -45° at 1.795 GHz in a specific embodiment. The results are as follows: Figure 8 , 9 As shown in Figures 10 and 11.

[0047] 2. Simulation Result Analysis:

[0048] Reference Figure 6 Figure 1 shows the reflection coefficient curves of the four ports of the array antenna of this invention. The array antenna proposed in this invention has a VSWR of less than 1.3 at the ports within the range of 1.75-1.85 GHz, and a VSWR of less than 1.2 within the operating frequency range of 1.785-1.805 GHz. This indicates that the impedance matching of the antenna ports is good and can meet the requirements of practical applications.

[0049] Reference Figure 7 , where represents the port isolation of the array antenna of this invention. The array antenna proposed in this invention has an isolation of less than -20dB in the 1.75-1.85GHz range, and an isolation of less than -25dB in the operating frequency range of 1.785-1.805GHz, indicating that the antenna has high port isolation.

[0050] See Figures 8-11 The figure shows the antenna radiation pattern at a center frequency of 1.795 GHz. As can be seen from the figure, the cross-polarization ratios corresponding to main polarizations of 0° and 90° are greater than 20 dB, and the main polarization-cross-polarization ratios corresponding to main polarizations of ±45° are greater than 12 dB.

[0051] The above description is merely an example of the embodiments of the present invention and is not intended to limit the scope of protection of the present invention. Any changes made based on the design principles of the present invention, or any non-creative changes made on this basis, shall fall within the scope of protection of the present invention.

Claims

1. A quad-polarized high-isolation MIMO array antenna, comprising a dielectric substrate (1), a metal ground plane (2) printed on the upper surface of the dielectric substrate (1), and N feed networks (3) on the lower surface, where N ≥ 2; the upper surface of the dielectric substrate (1) is fixed with a linear radiation array composed of N periodically arranged dual-polarized dipole radiation units (4), the same number as the feed networks (3), longitudinal decoupling baffles (5) fixed on both sides of the linear radiation array and distributed along the arrangement direction of the N radiation units (4), and transverse decoupling baffles (6) disposed on both sides of each radiation unit (4); characterized in that: The power supply network (3) includes a first branch line coupler (31) and two parallel second branch line couplers (32). The input terminals of the two second branch line couplers (32) are respectively connected to the two output terminals of the first branch line coupler (31). A Schiffman phase shifter (33) is loaded between one output terminal of the first branch line coupler (31) and the input terminal of the second branch line coupler (32). A U-shaped stub (34) is printed on the inner side of the outer output terminal of the second branch line coupler (32). The outer output terminal of the second branch line coupler (32) is connected to a Wilkinson power divider (35). Each of the four output terminals of the Wilkinson power divider (35) is connected to two π-type attenuators (36). The first input terminal P1 and the second input terminal P2 of the first branch line coupler (31), and the two external input terminals P3 of the second branch line coupler (32) are respectively used as the input terminals of the feed network (3); the two feed structures of the bipolar dipole radiation unit (4) are respectively connected to the two internal output terminals P4 of the second branch line coupler (32) at their corresponding positions; By feeding the first input terminal P1 and the second input terminal P2 of the first branch line coupler (31), 0° and 90° polarization characteristics can be achieved; by feeding the external input terminal P3 of the second branch line coupler (32) connected to the Scheffman phase shifter (33), -45° polarization characteristics can be achieved; by feeding the external input terminal P3 of another second branch line coupler (32), 45° polarization characteristics can be achieved; when all four input terminals of the feeding network (3) are fed simultaneously, 0°, 90°, -45° and 45° polarization characteristics can be achieved.

2. The quad-polarized high-isolation MIMO array antenna according to claim 1, characterized in that, The dual-polarized dipole radiation unit (4) includes two perpendicularly intersecting radiation dielectric plates (41). Each radiation dielectric plate (41) has a T-shaped dipole radiation arm (42) with isosceles triangular structures at both ends printed on one side of the plate, and an inverted L-shaped microstrip feed line (43) feed structure printed on the other side. The T-shaped dipole radiation arms (42) printed on the two radiation dielectric plates (41) do not contact each other.

3. The quad-polarized high-isolation MIMO array antenna according to claim 1, characterized in that, The longitudinal decoupling baffles (5) fixed on both sides of the linear radiation array are symmetrical about the central axis of the linear radiation array, and the longitudinal decoupling baffles (5) are tilted away from the linear radiation array at an angle of 45°.

4. A quad-polarized high-isolation MIMO array antenna according to claim 3, characterized in that, The transverse decoupling baffle (6) adopts an isosceles trapezoidal structure with two waists that are perpendicularly connected to two longitudinal decoupling baffles (5).

5. A quad-polarized high-isolation MIMO array antenna according to claim 1, characterized in that, The Wilkinson power divider (35) includes a first 1-to-2 Wilkinson power divider and a second 1-to-2 Wilkinson power divider with the same structure as the first 1-to-2 Wilkinson power divider and connected to each output terminal of the first 1-to-2 Wilkinson power divider; the isolation resistors (351) between the output terminals of the three 1-to-2 Wilkinson power dividers are all 100Ω.

6. A quad-polarized high-isolation MIMO array antenna according to claim 1, characterized in that, The π-type attenuator (36) includes a π-type microstrip stub (361) and three chip resistors (362) loaded thereon, as well as a plurality of metallized vias (363) through the dielectric substrate (1) for connecting the π-type microstrip stub (361) to the metal ground plane (2).

7. A quad-polarized high-isolation MIMO array antenna according to claim 1, characterized in that, The Schoffman phase shifter (33) adopts a U-shaped microstrip structure with its bottom near the external input terminal P3 of the second branch line coupler (32), and its length is equal to 1 / 4 of the wavelength λ of the MIMO array antenna.

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