CN112688076B - Planar multi-port multi-band common-ground small-spacing high-isolation MIMO antenna - Google Patents
Planar multi-port multi-band common-ground small-spacing high-isolation MIMO antenna Download PDFInfo
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Abstract
The invention discloses a planar multi-port multi-band common-ground small-spacing high-isolation MIMO antenna, which comprises a dielectric substrate, a first monopole antenna and a second monopole antenna, wherein the front surface of the dielectric substrate is bilaterally symmetrical; a grounding plate on the back of the dielectric substrate, and a first parasitic unit and a second parasitic unit which are symmetrical left and right; in order to reduce mutual coupling between antenna units caused by surface waves of the grounding plate, a defected ground structure is designed in the middle of the grounding plate, slow wave characteristics and band rejection characteristics are obtained by changing the distribution of surface currents of the grounding plate, and port coupling between the antenna units is reduced. Meanwhile, floor branches are loaded in the middle of the grounding plate, and a new coupling path is introduced to offset the original coupling, so that the isolation between the antenna units is further improved. Finally, the novel non-connection neutralizing structure is loaded on the microstrip lines of the two antenna units, so that the influence of space radiation waves on the antenna units is reduced, and the isolation of three frequency bands is improved.
Description
Technical Field
The invention belongs to the technical field of microwave antennas, relates to a multi-band high-isolation MIMO antenna, and particularly relates to a planar multi-port multi-band common-ground small-spacing high-isolation MIMO antenna based on 5G communication.
Background
With the rapid development of social science and technology, the daily data transmission quantity of people is exponentially increased, and the demand of people on the mobile communication speed is increasingly increased. The fifth generation mobile communication (5G for short) with the characteristics of high speed, low power consumption, low time delay and the like becomes a main research and development hotspot of global communication. The realization of 5G will make a plurality of technical fields such as wisdom medical treatment, artificial intelligence, unmanned technique and VR obtain breakthrough progress.
The department of industry and trust in China in 2019 promulgates three 5G communication frequency bands of operators below 6 GHz: the bandwidth of 3400-3500MHz which is 100MHz is obtained in China telecommunication; the 2515 + 2675MHz and 4800 + 4900MHz frequency bands are obtained by China mobile; chinese Unicom obtains 3500MHz-3600 MHz. Compared with other regions in the world, the Chinese 5G technology is in the front of the world, is a key node for the scale construction of the Chinese 5G base station in 2020, plays an extremely important role in national epidemic prevention and disease control work at the beginning of the year, and is recognized consistently in the world. According to statistics, by 2 months in 2020, the number of 5G base stations in China exceeds 16 ten thousand, and by the end of 2020, three operators expect to build more than 55 ten thousand 5G base stations.
The MIMO communication system is a key influencing factor in the 5G technology, the frequency spectrum utilization rate and the channel capacity can be greatly improved by utilizing the multipath characteristic on the premise of not increasing the channel bandwidth and the transmitting power, and the MIMO antenna can directly influence the performance of the MIMO system. With the rapid development of wireless mobile communication terminals, mobile devices are increasingly becoming smaller and smaller, so the space left for antennas is also becoming smaller and smaller. At present, methods for realizing antenna miniaturization at home and abroad are mainly divided into three types: reducing the size of the antenna elements, reducing the number of multiple antennas, and reducing the distance between the antenna elements. The second method is the simplest and most effective method, but is contrary to the principle that MIMO system adopts multiple antennas to improve communication performance, and is not adopted by researchers. The first method has made great progress in both domestic and foreign research to reduce the size of the antenna element, while the second method: how to maintain the high isolation characteristic of the MIMO antenna while reducing the distance between the antenna elements is a research focus of the present MIMO antenna.
In this regard, scholars at home and abroad discuss and study the high isolation method of the MIMO antenna, and the methods are mainly classified into the following methods:
built-in decoupling network: the principle is that a circuit which can generate current opposite to that of the antenna units is loaded among the antenna units to change the path of coupling current and reduce mutual coupling among the antenna units, but the loaded decoupling network is often too complex and is inconvenient to integrate and apply to the mobile terminal.
The surface metamaterial structure and the electromagnetic band gap structure are both formed by periodic unit arrangement, can generate local resonance, have band elimination characteristics in a specific frequency band to inhibit electromagnetic waves on the surface of the grounding plate, and finally improve the isolation of the multi-antenna.
The defected ground structure is relatively simple, namely a groove-shaped structure is etched on a metal grounding plate to change the current distribution on the surface of the grounding plate, so that the slow wave characteristic and the band stop characteristic are obtained to reduce the mutual coupling of the antenna units.
The coupling reduction principle of the parasitic unit and the floor branch is that a new coupling path is introduced to offset the original coupling, and finally the isolation of the antenna unit is improved. Although this method is easy to design, simple in structure, and easy to integrate, the decoupling performance is inferior to the electromagnetic bandgap structure.
The neutralizing line is formed by connecting the antenna units by a metal wire, and introduces a neutralizing current which has the same amplitude and opposite phase with the original coupling current between the antenna units, thereby reducing mutual coupling between the antenna units. However, since the neutral line is usually directly connected to the feed line or the radiator of the antenna unit, the radiation performance of the antenna unit itself is often affected, and the design difficulty is increased by considering the overall situation during loading.
Among the studies published at home and abroad, the multi-band common-ground high-isolation MIMO antenna has been studied less. On the basis of the 5G communication frequency band, the high isolation characteristic of the three-frequency-band common-ground antenna is realized by three decoupling modes of the floor branch knot, the novel non-connection neutralization structure and the defect ground structure, and the three-frequency-band common-ground antenna has practical application value and important significance.
Disclosure of Invention
In order to solve the problems, the invention provides a three-band dual-port common-ground monopole antenna with high isolation characteristics based on a 5G mobile communication band. In order to reduce mutual coupling between antenna units caused by electromagnetic waves on the floor surface, a defected ground structure with a relatively simple decoupling structure is selected, slow wave characteristics and band stop characteristics are obtained by changing the distribution of current on the floor surface, and port coupling between the antenna units is reduced. And then, loading floor branches in the middle of the floor, introducing a new coupling path, and offsetting the new coupling path from the original coupling path to further improve the isolation between the antenna units. The space radiation wave can also cause mutual coupling between the antenna units, the radiation performance of the antenna is reduced, and a novel non-connection neutralizing structure is loaded between the antenna units;
the invention discloses a planar multi-port multi-band co-grounding small-space high-isolation MIMO antenna, which comprises a dielectric substrate, a first monopole antenna, a second monopole antenna, a grounding plate, a novel non-connection neutralizing structure, a first feed port, a second feed port, a first parasitic unit, a second parasitic unit and a floor branch.
The first monopole antenna and the second monopole antenna have the same structure and size, are printed in the middle of the left half part and the right half part of the upper surface of the dielectric substrate, and are symmetrical left and right along the longitudinal bisector of the dielectric substrate; the first monopole antenna and the second monopole antenna are composed of circular radiation patches, antenna branches and microstrip lines and are of symmetrical structures. In the first monopole antenna and the second monopole antenna, the bottom of the microstrip line is flush with the bottom edge of the dielectric substrate, and the top of the microstrip line is partially overlapped with the circular radiation patch, so that the left side edge and the right side edge of the microstrip line are connected with the circular radiation patch. The U-shaped antenna branch is loaded on the microstrip line, so that two sides of the antenna branch are parallel to the microstrip line, and the microstrip line vertically bisects the U-shaped antenna branch. The novel non-connection neutralization structure loaded between the microstrip lines of the two monopole antennas comprises a left half part and a right half part, wherein the left half part and the right half part are symmetrical along the longitudinal bisector of the dielectric substrate and are provided with bottom side metal lines and L-shaped branches. In the left half part and the right half part, the bottom side metal wire is parallel to the bottom edge of the dielectric substrate, the opposite end is respectively connected with the microstrip lines of the first monopole antenna and the second monopole antenna, and a certain gap is formed between the opposite end and the longitudinal bisector of the dielectric substrate. In the left half part and the right half part, the long sides of the L-shaped branches are respectively connected with the bottom side metal wires of the left half part and the right half part and are vertical to the bottom side metal wires; the end parts of the short edges are respectively flush with the opposite ends of the bottom side metal wires of the left half part and the right half part, finally a rectangular structure is formed between the left half part and the right half part, and a certain gap is formed between the top edge and the bottom edge of the rectangular structure at the position of a rectangular vertical bisector.
The grounding plate is printed on the lower surface of the dielectric substrate, and the bottom edge and the left and right sides of the grounding plate are respectively aligned with the bottom edge and the left and right sides of the dielectric substrate; the grounding plate is provided with a defected ground structure. The defected ground structure is composed of grooves designed on the left half part and the right half part of the grounding plate, and comprises equal-size grooves etched on the top edges of the left half part and the right half part of the grounding plate at the positions corresponding to the microstrip line of the first monopole antenna and the microstrip line of the second monopole antenna, four rectangular grooves A formed in the middle of the grounding plate and penetrating through the top edge of the grounding plate, and three rectangular grooves B penetrating through the bottom surface of the grounding plate. Two rectangular grooves A are positioned on the left half part of the grounding plate, and the other two rectangular grooves A are positioned on the right half part of the grounding plate; one rectangular groove B is positioned between the two rectangular grooves A on the left half part of the grounding plate; one rectangular groove B is positioned between the two rectangular grooves A on the right half part of the grounding plate; and the other rectangular groove B is positioned in the center of the grounding plate and between the two rectangular grooves A close to the longitudinal bisector of the medium substrate, and the vertical bisector is superposed with the longitudinal bisector of the medium substrate.
The middle part of the grounding plate is provided with a floor branch knot, and the floor branch knot is provided with a left floor branch knot and a right floor branch knot which are respectively composed of a transverse floor branch knot and a longitudinal floor branch knot. In the two floor branches, the bottom ends of the longitudinal floor branches are connected with the upper side of the ground plate and are perpendicular to the upper side of the ground plate, and meanwhile, the opposite side edges are respectively flush with the outer side edges of the two rectangular grooves A close to the longitudinal bisector of the dielectric substrate; the tail ends of the two transverse floor branches are respectively connected with the two longitudinal floor branches and are parallel to the grounding plate.
The first parasitic unit and the second parasitic unit are loaded on the back surface of the dielectric substrate and are bilaterally symmetrical along a longitudinal bisector of the dielectric substrate. The first parasitic unit and the second parasitic unit have the same structure and size and are both composed of transverse parasitic branches and longitudinal parasitic branches. Wherein, the transverse parasitic branch is parallel to the bottom edge of the dielectric substrate; the longitudinal parasitic branch is vertically and equally divided into a transverse parasitic branch and an upper branch and a lower branch; meanwhile, the opposite ends of the upper branch section and the lower branch section are not connected; the top of the upper branch is connected with the transverse parasitic branch. A circular ring is loaded between the upper section branch and the lower section branch, the outer diameter of the circular ring is the same as the size of the circular radiation patch in the monopole antenna on the same side, and the relative positions of the circular ring and the circular radiation patch are respectively connected with the positions of the upper section branch and the lower section branch close to the relative ends; a concentric circle is loaded on the inner side of the circular ring, a rectangular gap is etched on the concentric circle, the gap penetrates through the two opposite sides of the upper portion and the lower portion of the concentric circle, the concentric circle is divided into a left portion and a right portion, the center of the rectangular gap is located on a longitudinal bisector of the longitudinal parasitic branch, and the width of the rectangular gap is larger than the width of the longitudinal parasitic branch.
The first feed port and the second feed port are positioned at the bottom end of the microstrip line in the first monopole antenna and the second monopole antenna.
The invention has the advantages that:
1. the invention discloses a planar multi-port multi-band common-ground small-space high-isolation MIMO antenna, which provides a novel non-connection neutralizing structure for reducing mutual coupling between antenna units, combines two traditional decoupling methods of a defected ground structure and a floor branch, jointly solves the problems that the MIMO antenna has rapid deterioration of antenna performance and cannot normally work due to close-distance mutual influence, obviously improves impedance matching of an antenna working frequency band, reduces the mutual influence between the antenna units, has the advantages of close distance and high isolation, and has wide application prospect in an MIMO system.
2. The planar multi-port multi-band common-ground small-space high-isolation MIMO antenna greatly improves the isolation of three working frequency bands of the MIMO antenna by utilizing the combination of three decoupling methods of a novel non-connection neutralization structure, a defected ground structure and floor branches, and has the advantages of simple and practical decoupling structure, simple manufacture and realization of low-cost and miniaturized multi-band high-isolation MIMO antenna design.
3. The planar multi-port multi-band common-ground small-distance high-isolation MIMO antenna adopts three decoupling methods of a novel non-connection neutralization structure, a defect ground structure and a floor branch to realize high isolation performance of the common-ground multi-band MIMO antenna, so that the same common level can be kept among antenna units on the premise of high isolation performance, and the distance among the antenna units is greatly shortened.
Drawings
Fig. 1 is a schematic diagram of the three-dimensional structure of the planar multi-port multi-band common-ground small-pitch high-isolation MIMO antenna according to the present invention.
Fig. 2 is a schematic diagram of the upper surface structure of the planar multi-port multi-band common-ground small-pitch high-isolation MIMO antenna of the present invention.
Fig. 3 is a schematic diagram of the lower surface structure of the planar multi-port multi-band common-ground small-pitch high-isolation MIMO antenna of the present invention.
Fig. 4 is a comparison diagram of the return loss simulation before and after decoupling of the planar multi-port multi-band common-ground small-pitch high-isolation MIMO antenna designed by the embodiment.
Fig. 5 is a diagram illustrating simulation comparison of transmission coefficients before and after decoupling of a planar multi-port multi-band common-ground small-pitch high-isolation MIMO antenna designed according to an embodiment.
Fig. 6a is a simulation diagram of the radiation direction of the monopole at 2.6GHz after the decoupling of the planar multi-port multi-band common-ground small-pitch high-isolation MIMO antenna designed by the embodiment.
Fig. 6b is a simulation diagram of the radiation direction of the monopole at 3.5GHz after the decoupling of the planar multi-port multi-band co-ground small-pitch high-isolation MIMO antenna designed by the embodiment.
Fig. 6c is a simulation diagram of the radiation direction of the monopole at 4.85GHz after the decoupling of the planar multi-port multi-band co-ground small-pitch high-isolation MIMO antenna designed by the embodiment.
In the figure:
1-dielectric substrate 2-first monopole antenna 3-second monopole antenna
4-novel non-connecting neutralization structure 5-ground plate 6-first feed port
7-second feeding port 8-first parasitic element 9-second parasitic element
10-floor branch a-circular radiation patch b-antenna branch
c-microstrip line d-metal line e-L branch
f-transverse floor branch section g-longitudinal floor branch section 5 a-groove
5B-rectangular groove A5 c-rectangular groove B8 a-transverse parasitic branch knot
8 b-longitudinal parasitic branch 8 c-ring 8 d-concentric circle
8 e-rectangular slit
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The planar multi-port multi-band co-grounding small-space high-isolation MIMO antenna comprises a dielectric substrate 1, a first monopole antenna 2, a second monopole antenna 3, a novel non-connection neutralizing structure 4, a grounding plate 5, a first feeding port 6, a second feeding port 7, a first parasitic unit 8, a second parasitic unit 9 and a floor branch 10, and is manufactured by adopting a printed circuit board technology, as shown in figure 1.
The dielectric substrate 1 is a printed circuit board, and is selected from Rogers RO4350, the relative dielectric constant is 3.66, the transverse length is 66.6mm, the longitudinal width is 30mm, and the thickness is 1.524 mm.
The excitation mode of the first monopole antenna 2 and the second monopole antenna 3 is lumped port excitation, the two antennas are identical in structure and size, printed in the middle of the left half part and the right half part of the upper surface of the dielectric substrate 1 and symmetrical left and right along the longitudinal bisector of the dielectric substrate 1. The first monopole antenna 2 and the second monopole antenna 3 are composed of a circular radiation patch a, an antenna branch b and a microstrip line c, and are in a symmetrical structure. In the first monopole antenna 2 and the second monopole antenna 3, the bottom of the microstrip line c is flush with the bottom edge of the dielectric substrate 1, and the top of the microstrip line c is partially overlapped with the circular radiation patch a, so that the left side edge and the right side edge of the microstrip line c are connected with the circular radiation patch a. The U-shaped antenna stub b is loaded on the microstrip line c, so that both sides of the antenna stub b are parallel to the microstrip line c, and the microstrip line c vertically bisects the U-shaped antenna stub b, as shown in fig. 2. The two sheetsThe distance between the opposite sides of the U-shaped antenna branch b in the pole antenna is 0.185 lambda0Wherein λ is0Is the free space wavelength at a frequency of 2.6 GHz.
The coupling between the antenna units is generally composed of radiation coupling and conduction coupling, and is influenced by space radiation waves through antenna surface current analysis, the coupling current of the non-excitation antenna unit is mainly concentrated on the microstrip line c, and in order to reduce the coupling influence of the space radiation waves on the antenna units, a novel non-connection neutralizing structure 4 is loaded on the microstrip line c of the two monopole antennas. The novel non-connection neutralization structure 4 is loaded between the microstrip lines c of the first monopole antenna 2 and the second monopole antenna 3, has a left half part and a right half part which are symmetrical left and right along the longitudinal bisector of the dielectric substrate 1 and are provided with a bottom side metal wire d and an L-shaped branch e. In the left half part and the right half part, the bottom side metal wire d is parallel to the bottom side of the dielectric substrate, one opposite end is respectively connected with the microstrip lines c of the first monopole antenna 2 and the second monopole antenna 3, and a certain gap is formed between the opposite end and the longitudinal bisector of the dielectric substrate 1. In the left half part and the right half part, the long sides of the L-shaped branch knots are respectively connected with the bottom side metal wires d of the left half part and the right half part and are vertical to the bottom side metal wires d; the end parts of the short edges are respectively flush with the opposite ends of the bottom side metal wires d of the left half part and the right half part, finally a rectangular structure is formed between the left half part and the right half part, and a certain gap is formed between the top edge and the bottom edge of the rectangular structure at the position of a rectangular vertical bisector. When the antenna works, the novel non-connection neutralizing structure 4 is coupled to generate resonance, so that space radiation waves are prevented from being coupled to the non-excitation unit from the excitation unit, and the isolation of three frequency bands of the MIMO antenna is greatly improved.
The grounding plate 5 is printed on the lower surface of the dielectric substrate 1, and the bottom edge and the left and right sides of the grounding plate 5 are respectively aligned with the bottom edge and the left and right sides of the dielectric substrate 1. The ground plate 5 is divided into a left part and a right part of the ground plate which are symmetrical left and right along a longitudinal bisector of the dielectric substrate 1, and then equal-size grooves 5a are etched in the middle of the top edges of the left part and the right part of the ground plate and are respectively positioned at the positions corresponding to the microstrip line c of the first monopole antenna 2 and the microstrip line c of the second monopole antenna 3 for adjusting the impedance matching of the three frequency bands of the antenna. In order to reduce the conductive coupling caused by the surface current of the grounding plate 5, the invention is provided with four rectangular grooves A5B penetrating through the top edge of the grounding plate 5 and three rectangular grooves B5c penetrating through the bottom surface of the grounding plate 5 in the middle of the grounding plate 5, thereby forming a defected ground structure. Two of the rectangular slots A5b are located on the left portion of the ground plate 5 and the other two rectangular slots A5b are located on the right portion of the ground plate 5. One rectangular groove B5c is positioned between two rectangular grooves A5B at the left part of the grounding plate 5; one rectangular groove B5c is located between two rectangular grooves A5B on the right part of the ground plate 5; another rectangular slot B5c is located in the center of the ground plate 5 and between two rectangular slots A5B near the longitudinal bisector of the dielectric substrate 1, whose vertical bisectors coincide with the longitudinal bisector of the dielectric substrate 1.
Through the design of the rectangular groove A5B and the rectangular groove B5c, the path of the surface current of the grounding plate 5 can be prolonged, and the propagation of the surface wave of the grounding plate 5 is inhibited, but the decoupling effect is not obvious, so the floor branch 10 is loaded in the middle of the grounding plate 5 to introduce a new coupling path, the new coupling path is cancelled with the original coupling, and the mutual coupling between two parasitic units can be effectively reduced. The floor branch 10 has a left floor branch and a right floor branch, which are respectively the "┤" and "constructed" floor branch 10 composed of the transverse floor branch f and the longitudinal floor branch g. In the two floor branches 10, the bottom end of the longitudinal floor branch g is connected with the upper side of the grounding plate 5, is perpendicular to the upper side of the grounding plate 5, and meanwhile, the opposite side edges are respectively flush with the outer side edges of the two rectangular grooves A5b close to the longitudinal bisector of the dielectric substrate 1. The tail ends of the two transverse floor branches f are respectively connected with the two longitudinal floor branches g and are parallel to the grounding plate 5. The influence of the surface wave of the grounding plate 5 on the non-excitation monopole antenna is greatly reduced by the two designs of the defected ground structure and the ground branch 10.
The first feed port 6 and the second feed port 7 are used for inputting signals, are located at the bottom side of the dielectric substrate 1, are located at the bottom end of a microstrip line c in the first monopole antenna 2 and the second monopole antenna 3, are connected with the bottom of the microstrip line c and the ground plate 5, and have input impedance of 50 Ω.
The first monopole antenna 2 and the second monopole antenna 3 are dual-band antennas, in order to load the first parasitic element 8 and the second parasitic element 9 on the back surface of the dielectric substrate 1 on the premise of not increasing the volume of the antenna, a new resonance frequency band is excited by using the mutual coupling effect of the parasitic elements and the circular radiation patch a, and a new resonance is generated at 4.8-4.9GHz by adjusting the size and the position of the parasitic elements. The first parasitic unit 8 and the second parasitic unit 9 are printed on the lower surface of the dielectric substrate 1 and are symmetrical left and right along the longitudinal bisector of the dielectric substrate 1. As shown in fig. 3, the first parasitic unit 8 and the second parasitic unit 9 have the same structure and size, and are each composed of a transverse parasitic branch 8a and a longitudinal parasitic branch 8 b. Wherein, the transverse parasitic branch 8a is parallel to the bottom edge of the dielectric substrate 1; the longitudinal parasitic branch section 8b vertically and equally divides the transverse parasitic branch section into an upper section branch section and a lower section branch section; meanwhile, the opposite ends of the upper branch section and the lower branch section are not connected. The top of the upper branch is connected with the transverse parasitic branch 8 a. A circular ring 8c is loaded between the upper branch and the lower branch, the outer diameter of the circular ring 8c is the same as and concentric with the size of the circular radiation patch a in the monopole antenna 2 on the same side, and meanwhile, the relative position of the circular ring 8c is respectively connected with the position of the upper branch and the lower branch close to the relative end. A concentric circle 8d is loaded on the inner side of the circular ring 8c, a rectangular gap 8e is etched on the concentric circle 8d, the gap 8e penetrates through the upper side and the lower side of the concentric circle 8d, the concentric circle 8d is divided into a left part and a right part, the center of the rectangular gap 8e is positioned on the longitudinal bisector of the longitudinal parasitic branch 8b, and the width of the rectangular gap 8e is larger than the width of the longitudinal parasitic branch 8 b.
In the planar multi-port multi-band common-ground small-spacing high-isolation MIMO antenna with the structure:
the radius of the antenna main radiating circular radiating patch a is 3.8 mm; the width of the microstrip line c is 3.2mm, and the length of the microstrip line c is 17.3 mm; the length of the superposed part of the bottom of the main radiating circular radiating patch a and the top of the microstrip line c is 0.6 mm; the width of the U-shaped antenna branch b is 1.5mm, the length of a transverse branch in the U-shaped antenna branch b is 12mm, and the length of a longitudinal branch is 12.5 mm. The excitation mode of the first monopole antenna 2 and the second monopole antenna 3 is lumped port excitation, the center distance of a main radiating circular patch a in the two monopole antennas is 33.3mm, and the horizontal distance of the opposite edge of a U-shaped antenna branch b is 21.3 mm.
In the novel non-connection neutralizing structure 4, the vertical distance between the metal wire d and the bottom edge of the dielectric substrate 1 is 3mm, and the line width of the novel non-connection neutralizing structure 4 is 0.5mm, wherein the novel non-connection neutralizing structure comprises the metal wire d and an L-shaped branch e; the length of the metal wire d is 30.1mm, the length of the short side of the L-shaped branch section e is 3.5mm, the length of the long side is 8.5mm, and the width of the gap between the left part and the right part is 1 mm.
The grounding plate 5 is a rectangle with the height of 7.8mm and the width of 66.6 mm; a groove 5a formed in the position, corresponding to the monopole antenna microstrip line c, of the grounding plate 5 is a rectangular groove 4.5mm long and 2mm high; the widths of the rectangular groove A5B and the rectangular groove B5c formed in the middle of the grounding plate 5 are both 0.9mm, and the distance between the adjacent rectangular grooves A5B and the rectangular groove B5c is both 0.6 mm. The lengths of the two rectangular grooves A5B and 3 rectangular grooves B5c located on the outer side are both 4mm, and the lengths of the two rectangular grooves A5B located on the inner side are 7 mm.
In the floor branches 10 on the left side and the right side, the width of the longitudinal floor branch g is 0.8mm, the length of the longitudinal floor branch g is 22mm, and the distance between the two longitudinal floor branches g is 3.9 mm; the width of the transverse floor branch f is 1mm, the length of the transverse floor branch f is 11mm, and the transverse floor branch f is connected with the longitudinal floor branch g at a position 4.8mm away from the top of the longitudinal floor branch g.
In the first parasitic unit 8 and the second parasitic unit 9, the length of the transverse parasitic branch 8a is 18mm, the width is 1.5mm, the length of the upper branch in the longitudinal parasitic branch 8b is 4.5mm, the length of the lower branch is 6.5mm, and the width is 0.6 mm; the inner diameter of the circular ring 8c is 2.9 mm; the radius of the concentric circle 8d is 2mm, and the width of the rectangular slit 8e etched in the concentric circle 8d is 1mm and the length is 4 mm.
The planar multi-port multi-band common-ground small-spacing high-isolation MIMO antenna with the structure is subjected to simulation test, as shown in figure 4, the S before and after decoupling is carried out11、S22Comparing the graphs, it can be seen that before the decoupling, the two monopole antennas are interfered by the close distance mutual coupling, so that the impedance matching performance of the antennas is deteriorated, and especially in the high frequency band, the antennas cannot work normally. After the decoupling structure is loaded, the mutual coupling influence among the antenna units is reduced, the impedance matching of the three frequency bands of the monopole antenna is improved, and the three working frequency bands are respectively 2.5-2.7GHz, 3.26-3.83GHz and 4.73-4.97GHz (S)11<-10dB&S21<20dB) completely covering the 5G mobile communication band (sub-6 GHz). As shown in FIG. 5, for decoupling front and rear S12、S21Compared with the figure, in the low frequency band 2515-2675MHz of 5G mobile communication (sub-6GHz), the bandwidth of the antenna is widened, and the isolation is improved from 15dB to more than 27 dB; in the middle frequency band of 3400-3600MHz, the impedance matching of the antenna is improved, and the mutual coupling is reduced to-25.7 dB from-12.7 dB before the decoupling; at 4800-4900MHz band, the isolation of the antenna before decoupling is 8.8dB, the antenna can not effectively radiate electromagnetic wave in the band, after the decoupling structure is loaded, the performance of the antenna is greatly improved, the monopole antenna can normally work in the band, and the isolation of the antenna is-27.8 dB. It can be seen from fig. 5 that the decoupling effect of the decoupling structure in the three operating frequency bands of the antenna is very significant.
The maximum gains of the monopole antenna at 2.6GHz, 3.5GHz and 4.85GHz are respectively 2.8dBi, 2.65dBi and 3.74dBi, the actual gains of the antennas at the three frequency bands are all more than 2dBi, and the design indexes of the antennas are met. As shown in fig. 6, the antennas are horizontally positioned at the xoy plane for the xoz plane and the yoz plane radiation patterns when the antennas are operating at 2.6GHz, 3.5GHz, and 4.85GHz, respectively. It can be seen from the figure that when the antenna operates at 2.6GHz, the radiation of the antenna at xoz plane theta, 240-300 deg., is relatively weak, and the radiation at yoz plane is nearly omnidirectional; at 3.5GHz, the antenna is approximately omnidirectional radiation at the xoz plane, and mainly radiates outwards towards the direction of 0-180 degrees at the yoz plane; when the working frequency of the antenna is 4.85GHz, the radiation of the antenna at xoz and yoz planes theta, 240-300 degrees, is relatively weak.
All the test results verify that the three working frequency bands of the planar multi-port multi-band common-ground small-spacing high-isolation MIMO antenna have good isolation characteristics, the test results are successful, and the aim of the invention is achieved.
Claims (3)
1. The planar multi-port multi-band co-ground small-space high-isolation MIMO antenna comprises a dielectric substrate, a first monopole antenna, a second monopole antenna, a ground plate, a novel non-connection neutralizing structure, a first feed port, a second feed port, a first parasitic unit, a second parasitic unit and a ground plate branch section;
the first monopole antenna and the second monopole antenna have the same structure and size, are printed in the middle of the left half part and the right half part of the upper surface of the dielectric substrate, and are symmetrical left and right along the longitudinal bisector of the dielectric substrate; the first monopole antenna and the second monopole antenna are respectively composed of a circular radiation patch, an antenna branch and a microstrip line and are in a symmetrical structure; in the first monopole antenna and the second monopole antenna, the bottom of the microstrip line is flush with the bottom edge of the dielectric substrate, and the top of the microstrip line is partially overlapped with the circular radiation patch, so that the left side edge and the right side edge of the microstrip line are connected with the circular radiation patch; the antenna branch of the U-shaped structure is loaded on the microstrip line, so that two side parts of the antenna branch are parallel to the microstrip line, and the microstrip line vertically and equally divides the U-shaped antenna branch;
the grounding plate is printed on the lower surface of the dielectric substrate, and the bottom edge and the left and right sides of the grounding plate are respectively aligned with the bottom edge and the left and right sides of the dielectric substrate; a defected ground structure is designed on the grounding plate; the middle part of the grounding plate is provided with a ground branch knot;
the first feed port and the second feed port are positioned at the bottom end of a microstrip line in the first monopole antenna and the second monopole antenna;
the first parasitic unit and the second parasitic unit are loaded on the back surface of the dielectric substrate and are symmetrical left and right along the longitudinal bisector of the dielectric substrate;
the method is characterized in that:
a novel non-connection neutralization structure is loaded between the microstrip lines of the two monopole antennas, and the monopole antennas are provided with a left half part and a right half part which are bilaterally symmetrical along a longitudinal bisector of the dielectric substrate and are provided with bottom side metal lines and L-shaped branches; in the left half part and the right half part, the bottom side metal wire is parallel to the bottom edge of the dielectric substrate, one reverse end is respectively connected with the microstrip lines of the first monopole antenna and the second monopole antenna, and a certain gap is formed between the opposite end and the longitudinal bisector of the dielectric substrate; in the left half part and the right half part, the long sides of the L-shaped branches are respectively connected with the bottom side metal wires of the left half part and the right half part and are vertical to the bottom side metal wires; the end parts of the short edges are respectively flush with the opposite ends of the bottom side metal wires of the left half part and the right half part, finally a rectangular structure is formed between the left half part and the right half part, and a certain gap is formed between the top edge and the bottom edge of the rectangular structure at the rectangular vertical bisector;
the defected ground structure is formed by grooves designed on the left half part and the right half part of the grounding plate, and comprises equal-size grooves etched at the positions of the vertical projection of the microstrip line of the first monopole antenna and the microstrip line of the second monopole antenna on the top edges of the left half part and the right half part of the grounding plate, four rectangular grooves A penetrating through the top edges of the grounding plate and three rectangular grooves B penetrating through the bottom surface of the grounding plate, wherein the four rectangular grooves A are formed in the middle of the grounding plate; two rectangular grooves A are positioned on the left half part of the grounding plate, and the other two rectangular grooves A are positioned on the right half part of the grounding plate; one rectangular groove B is positioned between the two rectangular grooves A on the left half part of the grounding plate; one rectangular groove B is positioned between the two rectangular grooves A on the right half part of the grounding plate; the other rectangular groove B is positioned in the center of the grounding plate and between the two rectangular grooves A close to the longitudinal bisector of the medium substrate, and the vertical bisector is superposed with the longitudinal bisector of the medium substrate;
the floor branch section is provided with a left floor branch section and a right floor branch section, and is respectively composed of a transverse floor branch section and a longitudinal floor branch section; in the two floor branches, the bottom ends of the longitudinal floor branches are connected with the upper side of the ground plate and are perpendicular to the upper side of the ground plate, and meanwhile, the opposite side edges are respectively flush with the side edges, far away from the longitudinal bisector of the medium substrate, of the two rectangular grooves A close to the longitudinal bisector of the medium substrate; the tail ends of the two transverse floor branches are respectively connected with the two longitudinal floor branches and are parallel to the ground plate;
the first parasitic unit and the second parasitic unit have the same structure and size and are both composed of a transverse parasitic branch and a longitudinal parasitic branch; wherein, the transverse parasitic branch is parallel to the bottom edge of the dielectric substrate; the longitudinal parasitic branch is vertically and equally divided into a transverse parasitic branch and an upper branch and a lower branch; meanwhile, the opposite ends of the upper branch section and the lower branch section are not connected; the top of the upper branch section is connected with the transverse parasitic branch section; a circular ring is loaded between the upper section branch and the lower section branch, the outer diameter of the circular ring is the same as the size of the circular radiation patch in the monopole antenna on the same side, and the circular radiation patch are concentric; the upper and lower relative positions of the circular ring are respectively connected with the positions of the opposite end parts of the upper branch section and the lower branch section; a concentric circle is loaded on the inner side of the circular ring, a rectangular gap is etched on the concentric circle, the gap penetrates through the two opposite sides of the upper portion and the lower portion of the concentric circle, the concentric circle is divided into a left portion and a right portion, the center of the rectangular gap is located on a longitudinal bisector of the longitudinal parasitic branch, and the width of the rectangular gap is larger than the width of the longitudinal parasitic branch.
2. The planar multi-port multi-band common-ground small-pitch high-isolation MIMO antenna of claim 1, wherein: the transverse length of the dielectric substrate is 66.6mm, the longitudinal width of the dielectric substrate is 30mm, and the thickness of the dielectric substrate is 1.524 mm; the radius of the antenna main radiation circular patch is 3.8 mm; the width of the microstrip line is 3.2mm, and the length of the microstrip line is 17.3 mm; the length of the superposed part of the bottom of the main radiation circular patch and the top of the microstrip line is 0.6 mm; the width of the U-shaped antenna branch is 1.5mm, the length of a transverse branch in the U-shaped antenna branch is 12mm, and the length of a longitudinal branch is 12.5 mm; the distance between the centers of main radiation circular patches in the two monopole antennas is 33.3mm, and the horizontal distance between the opposite edges of U-shaped antenna branches is 21.3 mm;
in the novel non-connection neutralizing structure, the vertical distance between the metal wire and the bottom edge of the dielectric substrate is 3mm, the line width of the novel non-connection neutralizing structure is 0.5mm, and the novel non-connection neutralizing structure comprises the metal wire and L-shaped branches; the length of the metal wire is 30.1mm, the length of the short side of the L-shaped branch is 3.5mm, the length of the long side of the L-shaped branch is 8.5mm, and the gap width of the left part and the right part of the L-shaped branch is 1 mm;
the grounding plate is a rectangle with the height of 7.8mm and the width of 66.6 mm; the groove 5a formed in the position, corresponding to the monopole antenna microstrip line, of the grounding plate is a rectangular groove 4.5mm long and 2mm high; the widths of the rectangular grooves A and the rectangular grooves B formed in the middle of the grounding plate are both 0.9mm, the distance between every two adjacent rectangular grooves A and B is 0.6mm, the lengths of the two rectangular grooves A and the 3 rectangular grooves B positioned on the outer side are both 4mm, and the lengths of the two rectangular grooves A positioned on the inner side are 7 mm; in the floor branches on the left side and the right side, the width of the longitudinal floor branch is 0.8mm, the length of the longitudinal floor branch is 22mm, and the distance between the two longitudinal floor branches is 3.9 mm; the width of the transverse floor branch is 1mm, the length of the transverse floor branch is 11mm, and the transverse floor branch is connected with the longitudinal floor branch at a position 4.8mm away from the top of the longitudinal floor branch;
in the first parasitic unit and the second parasitic unit, the length of the transverse parasitic branch is 18mm, the width of the transverse parasitic branch is 1.5mm, the length of the upper branch in the longitudinal parasitic branch is 4.5mm, the length of the lower branch is 6.5mm, and the width of the upper branch is 0.6 mm; the inner diameter of the circular ring is 2.9 mm; the radius of the concentric circle is 2mm, the width of the etched rectangular gap on the concentric circle is 1mm, and the length of the etched rectangular gap is 4 mm.
3. The planar multi-port multi-band common-ground small-pitch high-isolation MIMO antenna of claim 1, wherein: the dielectric substrate is a printed circuit board, and Rogers RO4350 is selected, and the relative dielectric constant is 3.66.
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