Circularly polarized cross dipole MIMO antenna

Abstract

The invention relates to the technical field of wireless communication, and provides a circularly polarized cross dipole MIMO antenna, which comprises a dielectric substrate and at least two antenna units, and the antenna units are arranged in an array; each antenna unit comprises a first linear dipole, a second linear dipole, a feed coaxial line and a reflection floor; the first linear dipole and the second linear dipole are connected through one end, close to the dielectric substrate, of the feed coaxial line, and one end, far away from the dielectric substrate, of the feed coaxial line is connected to the reflection floor; the first linear dipole comprises a first dipole arm, a second dipole arm and a first quarter phase delay line; the second linear dipole comprises a third dipole arm, a fourth dipole arm and a second quarter phase delay line; the first dipole arm and the third dipole arm are parallel to each other and extend reversely along the same axial direction; and the second dipole arm and the fourth dipole arm are parallel to each other and extend reversely along the same axial direction. According to the invention, the isolation between the antenna units can be improved.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a circularly polarized cross-dipole MIMO antenna. Background Art

[0002] MIMO (Multiple Input Multiple Output) technology is a core technology in modern wireless communication systems and is widely used in fields such as 4G, 5G, Wi-Fi, and radar. Its origins lie in the ever-increasing demand for high data rates, spectral efficiency, and reliability in wireless communications. Traditional single-input single-output (SISO) systems, limited by Shannon's theorem, struggle to meet the requirements of high-speed data transmission. MIMO, by deploying multiple antennas at both the transmitter and receiver, leverages the characteristics of multipath propagation to significantly improve system performance.

[0003] The fundamental principle of MIMO technology is to increase channel capacity by leveraging spatial diversity and spatial multiplexing. In a multipath environment, signals propagate along different paths. A MIMO system uses multiple antennas to transmit and receive data streams in parallel, achieving spatial multiplexing. This multiplies the data rate without increasing bandwidth. MIMO also enhances signal robustness through diversity techniques (such as spatial diversity or beamforming), reducing bit error rates and improving communication quality.

[0004] Research and development of MIMO technology began in the 1990s, with pioneering work at Bell Labs laying the theoretical foundation. After the 2000s, with advances in computing power and array antenna design, MIMO gradually transitioned from theory to practical applications, such as in Wi-Fi (802.11n / ac / ax) and LTE systems. Massive MIMO, a key 5G technology, further improves capacity and energy efficiency by deploying dozens to hundreds of antennas. It also supports multi-user MIMO (MU-MIMO), enabling efficient simultaneous communication among multiple users.

[0005] While MIMO technology offers advantages in flexibility and efficiency, it also faces challenges, such as the complexity of antenna arrays, the high computational demands of signal processing, and limitations on device miniaturization. With the introduction of millimeter waves, artificial intelligence, and new antenna materials, MIMO technology continues to evolve, providing even stronger support for next-generation wireless communication systems. With the rapid development of wireless communication technology, miniaturization and compactness of communication systems have become a new development trend. The contradictions between miniaturization and broadband antenna units, miniaturization and high isolation between MIMO antennas, and high integration and high performance between antennas and other components have become challenges in antenna design.

[0006] However, due to the dual requirements of high speed and large capacity for mobile communication systems, traditional single antennas currently struggle to meet these requirements. Multiple antenna elements are generally required, making MIMO technology the preferred choice. However, using multiple antenna elements increases the antenna size, which conflicts with the miniaturization and compactness of mobile communication systems. Furthermore, the close spacing between MIMO antenna elements results in poor isolation between elements, leading to signal crosstalk. Summary of the Invention

[0007] In view of the above shortcomings of the prior art, the present invention proposes a circularly polarized cross-dipole MIMO antenna to solve the problem that the existing circularly polarized cross-dipole MIMO antenna has poor isolation and easily causes signal crosstalk.

[0008] In order to solve the above technical problems, the present invention adopts the following technical solutions: An embodiment of the present invention provides a circularly polarized cross-dipole MIMO antenna, comprising a dielectric substrate and at least two antenna units fixed to the dielectric substrate, wherein the antenna units are arranged in an array; Each antenna unit includes a first linear dipole, a second linear dipole, a feed coaxial line, and a reflective floor; the first linear dipole is fixed to the upper surface of the dielectric substrate, the second linear dipole is fixed to the lower surface of the dielectric substrate, the first linear dipole and the second linear dipole are connected by an end of the feed coaxial line close to the dielectric substrate, and the end of the feed coaxial line away from the dielectric substrate is connected to the reflective floor; The first linear dipole includes a first dipole arm, a second dipole arm, and a first quarter-phase delay line; the first dipole arm and the second dipole arm are perpendicular to each other, and ends of the first dipole arm and the second dipole arm that are close to each other are connected by the first quarter-phase delay line; The second linear dipole includes a third dipole arm, a fourth dipole arm, and a second quarter-phase delay line; the third dipole arm and the fourth dipole arm are perpendicular to each other, and ends of the third dipole arm and the fourth dipole arm close to each other are connected by the second quarter-phase delay line; The first dipole arm and the third dipole arm are parallel to each other and extend in opposite directions along the same axis; the second dipole arm and the fourth dipole arm are parallel to each other and extend in opposite directions along the same axis.

[0009] Preferably, the first dipole arm includes a first dipole body and a first feed patch formed by extending from one end of the first dipole body close to the third dipole arm; two ends of the first quarter-phase delay line are respectively connected and fixed to two ends of the first dipole body and the second dipole arm close to each other, extend around the first feed patch, and are spaced apart from the first feed patch; The third dipole arm includes a third dipole body and a second feed patch formed by extending from one end of the third dipole body close to the third dipole arm; two ends of the second quarter-phase delay line are respectively connected and fixed to two ends of the third dipole body and the fourth dipole arm close to each other, extend around the second feed patch, and are spaced apart from the second feed patch; The feeding coaxial line is connected to the first feeding patch and the second feeding patch respectively.

[0010] Preferably, the first quarter phase delay line and the second quarter phase delay line are both semicircular arc structures.

[0011] Preferably, the feeding coaxial line includes a cylindrical feeding coaxial line body, an outer conductor arranged around the outer circumference of the feeding coaxial line body, and an inner conductor arranged in the center of the feeding coaxial line body, wherein one end of the inner conductor extends beyond the corresponding end of the feeding coaxial line body; The dielectric substrate is provided with a first through hole penetrating therethrough; The second feeding patch is provided with a second through hole running through it; One end of the inner conductor extending beyond the feed coaxial line body passes through the second through hole and the first through hole in sequence and is connected to the first feed patch; one end of the outer conductor close to the dielectric substrate is fixed to the second feed patch, and one end of the outer conductor away from the dielectric substrate is fixed to the reflective floor.

[0012] Preferably, the circularly polarized cross-dipole MIMO antenna further includes a short-circuit metal post; two ends of the short-circuit metal post are respectively electrically connected to the feeding coaxial lines of the two antenna units.

[0013] Preferably, the short-circuit metal column includes a first metal column and a second metal column fixed in the middle position of the first metal column; the first metal column and the second metal column are perpendicular to each other, and the second metal column is parallel to the feeding coaxial line; the two ends of the first metal column are respectively connected to the feeding coaxial lines of the two antenna units.

[0014] Preferably, the first linear dipole is formed by printing on the upper surface of the dielectric substrate, and the second linear dipole is formed by printing on the lower surface of the dielectric substrate.

[0015] Preferably, the ratios of the length, width and thickness of the dielectric substrate and the length of the feeding coaxial line are 38:23:4:10 respectively.

[0016] Preferably, the dielectric constant of the dielectric substrate is 3.38 and the loss tangent is 0.0027.

[0017] Preferably, the first dipole arm, the second dipole arm, the third dipole arm and the fourth dipole arm are all rectangular structures.

[0018] Compared with the related art, in an embodiment of the present invention, two antenna units are fixed to a dielectric substrate, and the antenna units are arranged in an array; each antenna unit includes a first linear dipole, a second linear dipole, a feed coaxial line, and a reflective floor; the first linear dipole is fixed to the upper surface of the dielectric substrate, and the second linear dipole is fixed to the lower surface of the dielectric substrate; the first linear dipole and the second linear dipole are connected by an end of the feed coaxial line close to the dielectric substrate, and the end of the feed coaxial line away from the dielectric substrate is connected to the reflective floor; the first linear dipole includes a first dipole arm, a second dipole arm, and a first quarter-phase delay line connecting the first dipole arm and the second dipole arm; the first dipole arm and the second dipole arm are perpendicular to each other; the second linear dipole includes a third dipole arm, a fourth dipole arm, and a second quarter-phase delay line connecting the third dipole arm and the fourth dipole arm; by using a binary array composed of cross-dipole units, circular polarization is achieved, and the isolation between the antenna units is also improved, thereby avoiding signal crosstalk and achieving high reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be described in detail below with reference to the accompanying drawings. The above and other aspects of the present invention will become clearer and easier to understand through the detailed description made with reference to the following drawings. In the accompanying drawings: Figure 1 A top view of a circularly polarized cross-dipole MIMO antenna provided in an embodiment of the present invention; Figure 2 A front view of a circularly polarized cross-dipole MIMO antenna provided in an embodiment of the present invention; Figure 3 A partial structural exploded diagram of a circularly polarized cross-dipole MIMO antenna provided in an embodiment of the present invention; Figure 4 An S11 graph of a circularly polarized cross-dipole MIMO antenna provided in an embodiment of the present invention; Figure 5An S21 graph of a circularly polarized cross-dipole MIMO antenna provided in an embodiment of the present invention; Figure 6 An axial ratio curve diagram of a circularly polarized cross-dipole MIMO antenna provided in an embodiment of the present invention; Figure 7 A front view of a short-circuited metal post of a circularly polarized cross-dipole MIMO antenna provided by an embodiment of the present invention; Figure 8 A partial structural exploded diagram of the short-circuited metal post of the circularly polarized cross-dipole MIMO antenna provided in an embodiment of the present invention; Figure 9 An S11 curve diagram of the short-circuited metal post of the circularly polarized cross-dipole MIMO antenna provided in an embodiment of the present invention; Figure 10 An S21 graph of a short-circuited metal post of a circularly polarized cross-dipole MIMO antenna provided in an embodiment of the present invention; Figure 11 This is a graph showing the axial ratio of the short-circuited metal posts of the circularly polarized cross-dipole MIMO antenna provided by an embodiment of the present invention.

[0020] Among them, 100, circularly polarized cross-dipole MIMO antenna, 10, antenna unit, 20, dielectric substrate, 1, first linear dipole, 11, first dipole arm, 111, first dipole body, 112, first feed patch, 12, second dipole arm, 13, first quarter-phase delay line, 2, second linear dipole, 21, third dipole arm, 211, third dipole body, 212, second feed patch, 22, fourth dipole arm, 23, second quarter-phase delay line, 3, feed coaxial line, 31, feed coaxial line body, 32, outer conductor, 33, inner conductor, 4, reflecting floor, 5, short-circuit metal column, 51, first metal column, 52, second metal column, 6, first through hole, 7, second through hole. DETAILED DESCRIPTION

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of the application are for the purpose of describing specific embodiments only and are not intended to limit this application. The terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned drawings are intended to cover non-exclusive inclusions. The terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects, not to describe a specific order.

[0022] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0024] See also Figure 1-Figure 3 As shown, an embodiment of the present invention provides a circularly polarized cross-dipole MIMO antenna 100. The circularly polarized cross-dipole MIMO antenna 100 includes a dielectric substrate 20 and at least two antenna units 10 fixed to the dielectric substrate 20, with the two antenna units 10 arranged in an array. The antenna 100 has a small overall size and is easy to process. The dielectric substrate 20 is made of Rogers 4003C material. Rogers 4003C is a high-performance laminate material from the RO4000 series. It is a glass cloth-reinforced hydrocarbon ceramic filler that combines the electrical properties of PTFE / glass cloth with the processability of epoxy resin / glass.

[0025] Each antenna unit 10 comprises a first linear dipole 1, a second linear dipole 2, a feed coaxial line 3, and a reflective floor 4. The first linear dipole 1 is fixed to the upper surface of the dielectric substrate 20, and the second linear dipole 2 is fixed to the lower surface of the dielectric substrate 20. The first linear dipole 1 and the second linear dipole 2 are connected by the feed coaxial line 3 at the end closest to the dielectric substrate 20, and the feed coaxial line 3 is connected to the reflective floor 4 at the end away from the dielectric substrate 20. To achieve directional radiation, a reflective floor 4 is introduced at a distance of one-quarter wavelength below the crossed first and second linear dipoles 1 and 2. The quarter-wavelength distance is determined as one-quarter of the wavelength of the center frequency. Furthermore, each circularly polarized cross-dipole MIMO antenna 100 is excited by a central feed coaxial line 3.

[0026] The first linear dipole 1 includes a first dipole arm 11, a second dipole arm 12, and a first quarter-phase delay line 13. The first dipole arm 11 and the second dipole arm 12 are perpendicular to each other. The first and second dipole arms 11, 12 are connected at their respective ends by the first quarter-phase delay line 13. The first quarter-phase delay line 13 connects the first and second dipole arms 11, 12, creating a 90-degree phase difference between them, thereby achieving circularly polarized radiation.

[0027] The second linear dipole 2 includes a third dipole arm 21, a fourth dipole arm 22, and a second quarter-phase delay line 23; the third dipole arm 21 and the fourth dipole arm 22 are perpendicular to each other. The ends of the third dipole arm 21 and the fourth dipole arm 22 that are close to each other are connected by the second quarter-phase delay line 23. The first dipole arm 11 and the third dipole arm 21 are parallel to each other and extend in opposite directions along the same axis, and the second dipole arm 12 and the fourth dipole arm 22 are parallel to each other and extend in opposite directions along the same axis. The third dipole arm 21 and the fourth dipole arm 22 are connected by the second quarter-phase delay line 23, so that a 90-degree phase difference is generated between the third dipole arm 21 and the fourth dipole arm 22, thereby achieving circularly polarized radiation. Optionally, the first dipole arm 11 and the third dipole arm 21 are located in the Y-axis direction, the second dipole arm 12 and the fourth dipole arm 22 are located in the X-axis direction, and the thickness direction of the dielectric substrate 20 is the Z-axis direction. The first dipole arm 11 and the third dipole arm 21 are located on the same straight line, and the second dipole arm 12 and the fourth dipole arm 22 are located on the same straight line. The first dipole arm 11, the second dipole arm 12, the third dipole arm 21, and the fourth dipole arm 22 are arranged in correspondence with each other to form a circularly polarized cross dipole.

[0028] Specifically, circular polarization is achieved by adopting a binary array composed of cross-dipole units, and the isolation between the antenna units 10 is also improved, thereby avoiding signal crosstalk and achieving high reliability.

[0029] In this embodiment, the first dipole arm 11 includes a first dipole body 111 and a first feed patch 112 formed by extending from one end of the first dipole body 111 close to the third dipole arm 21. The two ends of the first quarter-phase delay line 13 are respectively connected and fixed to the two ends of the first dipole body 111 and the second dipole arm 12 close to each other, and extend around the first feed patch 112 and are spaced apart from the first feed patch 112. The third dipole arm 21 includes a third dipole body 211 and a second feed patch 212 formed by extending from one end of the third dipole body 211 close to the third dipole arm 21. The two ends of the second quarter-phase delay line 23 are respectively connected and fixed to the two ends of the third dipole body 211 and the fourth dipole arm 22 close to each other, and extend around the second feed patch 212 and are spaced apart from the second feed patch 212. The feeding coaxial line 3 is connected to the first feeding patch 112 and the second feeding patch 212 respectively.

[0030] Optionally, the mutually adjacent ends of the first dipole arm 11 and the second dipole arm 12 and the first quarter-phase delay line 13 collectively surround the first feed patch 112, thereby protecting the first feed patch 112. The mutually adjacent ends of the third dipole arm 21 and the fourth dipole arm 22 and the second quarter-phase delay line 23 collectively surround the second feed patch 212, thereby protecting the second feed patch 212.

[0031] Specifically, in the dipole structure of the MIMO antenna, the first feed patch 112 and the second feed patch 212 are key transition components connecting the feed coaxial line 3 with the first dipole arm 11 and the third dipole arm 21. Their core function is to achieve efficient coupling and transmission of electromagnetic energy from the feed coaxial line 3 (transmission line) to the first dipole arm 11 and the third dipole arm 21 (radiators). At the same time, they cooperate with structures such as the phase delay line to ensure the radiation performance of the antenna.

[0032] The inner conductor 33 of the feeding coaxial line 3 is connected to the first feeding patch 112, and the outer conductor 32 is grounded. When the radio frequency signal is transmitted from the feeding coaxial line 3 to the first feeding patch 112, an alternating electromagnetic field is formed on the patch.

[0033] The first and second feed patches 112, 212, connected to the coaxial feed line 3, provide a multifunctional component that performs energy conversion, impedance matching, and structural isolation. Their design directly impacts the antenna's efficiency, bandwidth, and isolation performance for MIMO antennas. In conjunction with a quarter-phase delay line, the phase relationship between the first, second, third, and fourth dipole arms 11, 12, 21, and 22 is further maintained, achieving the desired polarization and radiation characteristics.

[0034] In this embodiment, both the first quarter phase delay line 13 and the second quarter phase delay line 23 are semicircular arc structures.

[0035] In this embodiment, the feeding coaxial line 3 includes a cylindrical feeding coaxial line body 31, an outer conductor 32 arranged around the outer circumference of the feeding coaxial line body 31, and an inner conductor 33 arranged in the center of the feeding coaxial line body 31, and one end of the inner conductor 33 extends beyond the corresponding end of the feeding coaxial line body 31.

[0036] The dielectric substrate 20 is provided with a first through hole 6 penetrating therethrough.

[0037] The second feeding patch 212 is provided with a second through hole 7 penetrating therethrough, wherein both the first through hole 6 and the second through hole 7 are circular hole structures.

[0038] Specifically, the inner conductor 33 of the feeding coaxial line 3 is connected to the first dipole arm 11 on the upper surface of the dielectric substrate 20 , and the outer conductor 32 of the feeding coaxial line 3 is connected to the third dipole arm 21 on the lower surface of the dielectric substrate 20 and the reflective floor 4 .

[0039] The end of the inner conductor 33 extending beyond the feeding coaxial line body 31 passes through the second through hole 7 and the first through hole 6 in sequence and is connected to the first feeding patch 112; the end of the outer conductor 32 close to the dielectric substrate 20 is fixed to the second feeding patch 212, and the end of the outer conductor 32 away from the dielectric substrate 20 is fixed to the reflective floor 4.

[0040] In this embodiment, Figure 4 The high isolation circular polarization cross-dipole MIMO antenna 100 is shown. From the curve, we can see that in the 3.281-4.6 GHz frequency band Less than -10 dB, the design requirement has been achieved in terms of bandwidth.

[0041] like Figure 5 The high isolation circular polarization cross-dipole MIMO antenna 100 is shown. From the curve, we can see that in the 3.2-4.6 GHz frequency band Less than -10 dB. The isolation of the low-frequency part is close to -10 dB, which is close to the isolation of traditional MIMO antennas. Some improvements are still needed in this regard. like Figure 6The figure shows the axial ratio curve of the high-isolation circularly polarized cross-dipole MIMO antenna 100. The axial ratio here refers to the axial ratio when Phi=0° and Theta=0°. It can be seen that the axial ratio is less than 3 in the range of 3.396-3.83 GHz, and a relatively good circular polarization effect is achieved in this range.

[0042] Please see the attached Figure 7-Figure 8 As shown, in this embodiment, the circularly polarized cross-dipole MIMO antenna 100 further includes a short-circuit metal post 5; both ends of the short-circuit metal post 5 are electrically connected to the feed coaxial lines 3 of the two antenna units 10. Optionally, both ends of the short-circuit metal post 5 are electrically connected to the inner conductors 33 of the feed coaxial lines 3 of the two antenna units 10.

[0043] Specifically, since the mutual coupling level between the two antenna units 10 in the above structure is not very ideal in the low-frequency part, an additional short-circuit metal column 5 is introduced in the middle of the floor. The specific structure is as follows Figure 8 As shown. The port isolation between the two antennas is relatively low within the circular polarization passband of the antenna, mainly because both antenna units 10 generate the same left-hand circular polarization radiation within the operating frequency band. However, in the transmission coefficient (S 21 ) A low point can be found at high frequencies outside the passband, where the coupling level between the two antenna elements 10 is low. This is because left-handed circularly polarized radiation is generated on the excitation antenna, while linearly polarized radiation is generated on the coupling antenna. If we can transform the transmission coefficient (S 21 ) is moved into the circularly polarized passband of the antenna, achieving higher port isolation between the two antenna elements 10. Introducing a passband structure can move the high isolation point outside the passband into the frequency band.

[0044] In this embodiment, the short-circuit metal post 5 includes a first metal post 51 and a second metal post 52 fixed in the middle of the first metal post 51. The first metal post 51 and the second metal post 52 are perpendicular to each other, and the second metal post 52 is parallel to the feed coaxial line 3. The two ends of the first metal post 51 are respectively connected to the feed coaxial lines 3 of the two antenna units 10. The feed coaxial lines 3 of the two antenna units 10 connected by the first metal post 51 can be short-circuited to ground, reducing coupling between the antenna units 10.

[0045] In this embodiment, the first linear dipole 1 is formed by printing on the upper surface of the dielectric substrate 20, and the second linear dipole 2 is formed by printing on the lower surface of the dielectric substrate 20. Commonly used dipoles are usually fed via microstrip lines or coplanar waveguides. If the feed line and the antenna are on the same surface, they are prone to coupling with the antenna radiation field and causing interference. A layered layout, however, allows the feed line to be designed inside the substrate or on another surface, physically isolating it from the antenna radiation area, reducing feed loss and interference and improving antenna efficiency. Therefore, this layered printing method, through its core functions of "reducing mutual coupling, improving space utilization, supporting diversity technology, and optimizing feeding," ultimately ensures that MIMO antennas achieve high-performance communications, such as high capacity and high reliability, within a limited space.

[0046] In this embodiment, the ratios of the length, width, and thickness of the dielectric substrate 20 and the length of the feeding coaxial line 3 are 38:23:4:10, respectively.

[0047] Specifically, the length, width, and thickness of the dielectric substrate 20 are 76.8 mm, 46.8 mm, and 0.8 mm, respectively; the length of the feed coaxial line 3 is 18.8 mm. Of course, the dimensions of the dielectric substrate 20 and the feed coaxial line 3 may also be other, which will not be described here.

[0048] In this embodiment, the dielectric substrate 20 has a dielectric constant of 3.38 and a loss tangent of 0.0027. A dielectric substrate with a dielectric constant of 3.38 (medium value) and a loss tangent of 0.0027 (low loss) primarily contributes to the MIMO antenna's size reduction, balanced radiation and confinement, optimized impedance matching, and reduced energy loss. This, combined with the layered layout, ensures low mutual coupling and high independence of the multiple dipoles, ultimately improving the communication capacity, efficiency, and reliability of the MIMO system. This makes it particularly suitable for terminal devices requiring high miniaturization and low loss.

[0049] In this embodiment, the first dipole arm 11, the second dipole arm 12, the third dipole arm 21 and the fourth dipole arm 22 are all rectangular structures. The rectangular structure is easy to produce and assemble.

[0050] like Figure 9 A modified version of the high isolation circularly polarized cross-dipole MIMO antenna 100 is shown. From the curve, we can see that in the 3.285-4.6 GHz frequency band Less than -10 dB, the bandwidth is basically unchanged compared to the previous structure.

[0051] like Figure 10 A modified version of the high isolation circularly polarized cross-dipole MIMO antenna 100 is shown. From the curve, we can see that in the 3.2-4.6 GHz frequency band Less than -14dB, the low-frequency isolation has been improved to a certain extent compared with the previous model, and has also reached the design indicators.

[0052] like Figure 11 The figure shows the axial ratio curve of the high-isolation circularly polarized cross-dipole MIMO antenna 100. The axial ratio here refers to the axial ratio when Phi=0° and Theta=0°. It can be seen that the axial ratio is less than 3 in the range of 3.409-3.965 GHz. In this range, a relatively good circular polarization effect is achieved. Compared with the structure before the modification, the axial ratio bandwidth has been expanded to a certain extent.

[0053] In summary, the present invention uses Rogers 4003C as the dielectric substrate 20, with an overall size of 76.8×46.8×18.8 mm, which is miniaturized compared to some traditional MIMO antennas. In addition, the dielectric substrate 20 used is thin, easy to process, and low in cost. While maintaining the circular polarization performance and antenna bandwidth of the antenna, the isolation between the antenna units 10 is improved compared to traditional MIMO antennas.

[0054] It should be noted that the various embodiments described above with reference to the accompanying drawings are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Those skilled in the art should understand that any modifications or equivalent substitutions to the present invention that do not depart from the spirit and scope of the present invention are intended to be encompassed within the scope of the present invention. Furthermore, unless the context otherwise requires, words appearing in the singular include the plural form, and vice versa. Furthermore, unless otherwise specified, all or part of any embodiment may be used in combination with all or part of any other embodiment.

Claims

1. A circularly polarized cross-dipole MIMO antenna, characterized in that: The circularly polarized cross-dipole MIMO antenna includes a dielectric substrate and at least two antenna units fixed to the dielectric substrate, and the antenna units are arranged in an array; Each antenna unit includes a first linear dipole, a second linear dipole, a feed coaxial line, and a reflective floor; the first linear dipole is fixed to the upper surface of the dielectric substrate, the second linear dipole is fixed to the lower surface of the dielectric substrate, the first linear dipole and the second linear dipole are connected by an end of the feed coaxial line close to the dielectric substrate, and the end of the feed coaxial line away from the dielectric substrate is connected to the reflective floor; The first linear dipole includes a first dipole arm, a second dipole arm, and a first quarter-phase delay line; the first dipole arm and the second dipole arm are perpendicular to each other, and ends of the first dipole arm and the second dipole arm that are close to each other are connected by the first quarter-phase delay line; The second linear dipole includes a third dipole arm, a fourth dipole arm, and a second quarter-phase delay line; the third dipole arm and the fourth dipole arm are perpendicular to each other, and ends of the third dipole arm and the fourth dipole arm close to each other are connected by the second quarter-phase delay line; The first dipole arm and the third dipole arm are parallel to each other and extend in opposite directions along the same axis; The second dipole arm and the fourth dipole arm are parallel to each other and extend in opposite directions along the same axis.

2. The circularly polarized cross-dipole MIMO antenna according to claim 1, wherein: The first dipole arm includes a first dipole body and a first feed patch formed by extending from one end of the first dipole body close to the third dipole arm; two ends of the first quarter-phase delay line are respectively connected and fixed to two ends of the first dipole body and the second dipole arm close to each other, and extend around the first feed patch and are spaced apart from the first feed patch; The third dipole arm includes a third dipole body and a second feed patch formed by extending from one end of the third dipole body close to the third dipole arm; two ends of the second quarter-phase delay line are respectively connected and fixed to two ends of the third dipole body and the fourth dipole arm close to each other, extend around the second feed patch, and are spaced apart from the second feed patch; The feeding coaxial line is connected to the first feeding patch and the second feeding patch respectively.

3. The circularly polarized cross-dipole MIMO antenna according to claim 1, wherein: The first quarter phase delay line and the second quarter phase delay line both have a semicircular arc structure.

4. The circularly polarized cross-dipole MIMO antenna according to claim 2, wherein: The feeding coaxial line comprises a cylindrical feeding coaxial line body, an outer conductor arranged around the outer circumference of the feeding coaxial line body, and an inner conductor arranged in the center of the feeding coaxial line body, wherein one end of the inner conductor extends beyond the corresponding end of the feeding coaxial line body; The dielectric substrate is provided with a first through hole penetrating therethrough; The second feeding patch is provided with a second through hole running through it; One end of the inner conductor extending beyond the feed coaxial line body passes through the second through hole and the first through hole in sequence and is connected to the first feed patch; one end of the outer conductor close to the dielectric substrate is fixed to the second feed patch, and one end of the outer conductor away from the dielectric substrate is fixed to the reflective floor.

5. The circularly polarized cross-dipole MIMO antenna according to claim 1, wherein: The circularly polarized cross-dipole MIMO antenna further includes a short-circuit metal post; two ends of the short-circuit metal post are respectively electrically connected to the feeding coaxial lines of the two antenna units.

6. The circularly polarized cross-dipole MIMO antenna according to claim 5, characterized in that: The short-circuit metal column includes a first metal column and a second metal column fixed in the middle position of the first metal column; the first metal column and the second metal column are perpendicular to each other, and the second metal column is parallel to the feeding coaxial line; the two ends of the first metal column are respectively connected to the feeding coaxial lines of the two antenna units.

7. The circularly polarized cross-dipole MIMO antenna according to claim 1, wherein: The first linear dipole is formed by printing on the upper surface of the dielectric substrate, and the second linear dipole is formed by printing on the lower surface of the dielectric substrate.

8. The circularly polarized cross-dipole MIMO antenna according to claim 1, wherein: The ratios of the length, width and thickness of the dielectric substrate and the length of the feeding coaxial line are 38:23:4:10 respectively.

9. The circularly polarized cross-dipole MIMO antenna according to claim 1, wherein: The dielectric constant of the dielectric substrate is 3.38, and the loss tangent is 0.0027.

10. The circularly polarized cross-dipole MIMO antenna according to claim 1, wherein: The first dipole arm, the second dipole arm, the third dipole arm and the fourth dipole arm are all rectangular structures.

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