MIMO terminal antenna loaded with lumped capacitance

Abstract

The invention discloses an MIMO terminal antenna loaded with lumped capacitance, and belongs to the technical field of wireless communication. The antenna comprises a horizontal dielectric substrate, two vertical dielectric substrates intersecting with the horizontal dielectric substrate, a metal ground and N dual-port coupled feed antenna pairs, 2N + 2 gaps are formed in the long edge of the metal ground, and the metal ground is printed on the upper surface of the horizontal dielectric substrate; the N dual-port coupled feed antenna pairs are arranged on the two vertical dielectric substrates, N / 2 dual-port coupled feed antenna pairs are arranged on the inner side of each vertical dielectric substrate, and each dual-port coupled feed antenna pair comprises a shared radiator, two feed branches, two L-shaped coupled feed branches and a lumped capacitor. Signals are transmitted to the shared radiator in an electromagnetic coupling mode, the lumped capacitance is loaded in the shared radiator, the matching impedance of the antenna structure is changed, signal loss is reduced, the bandwidth is improved, and meanwhile low cross coupling and small radiation interference are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communications, and in particular relates to a MIMO (Multiple Input Multiple Output) terminal antenna loaded with a lumped capacitor. Background Art

[0002] With the rapid development of the 5G information age, mobile terminals have increasing requirements for antenna bandwidth, signal transmission speed and system capacity. As one of the core technologies of 5G communications, MIMO technology enables the antenna system to work efficiently in multiple signal channels at the same time. By utilizing a transceiver system consisting of multiple transmitting antennas and receiving antennas to reduce channel fading, the frequency utilization rate and system capacity are increased exponentially, which has attracted widespread attention in the communications field. However, the space left for antennas inside the terminal is getting smaller and smaller. With the continuous growth of data demand, increasing the bandwidth of the MIMO antenna system while ensuring miniaturization is the key to improving system capacity, transmission rate and spectrum efficiency.

[0003] In order to achieve the problem of MIMO antenna bandwidth expansion, researchers have proposed a variety of methods and technologies.

[0004] Antenna multi-layer design: By using a multi-layer structure in the antenna design, the bandwidth of the antenna can be effectively extended. However, in limited spaces such as mobile terminals, this approach is often limited by size.

[0005] Tuned antennas are also a common method for bandwidth expansion in terminal antenna design. This method is to introduce adjustable elements (such as adjustable capacitors, inductors, switches, etc.) into the tuned antenna so that the antenna can dynamically adjust the operating frequency band as needed, thereby expanding its bandwidth. However, tuned antennas require complex control circuits and feedback systems, which increases the difficulty and cost of design.

[0006] Metamaterial antenna design is also a common method for extending bandwidth in terminal antennas. Materials with artificially designed electromagnetic properties can change the propagation characteristics of electromagnetic waves. By introducing metamaterials or negative refractive index materials, the bandwidth of the antenna can be significantly expanded. Metamaterial antennas usually require higher production costs.

[0007] In recent years, loading lumped elements between antennas has become a new research hotspot. Compared with other methods, this method changes the resonance characteristics, impedance matching, radiation pattern, etc. of the antenna, and can effectively expand the working bandwidth of the antenna. However, in previous studies, adjusting and designing lumped capacitors required high design accuracy and debugging work, which increased the complexity of design and production. Summary of the invention

[0008] The present invention proposes a MIMO terminal antenna loaded with a lumped capacitor to realize an antenna system with a small size, ultra-wideband and shared radiator.

[0009] The technical solution adopted by the present invention is:

[0010] A MIMO terminal antenna loaded with a lumped capacitor, comprising a horizontal dielectric substrate, two vertical dielectric substrates intersecting the horizontal dielectric substrate, a metal ground, and N dual-port coupled feeding antenna pairs, wherein N is an even number greater than 1;

[0011] The bottom sides of the two vertical dielectric substrates are connected to the long sides of the horizontal dielectric substrate, and 2N+2 gaps are opened on the long sides of the metal ground, which is printed on the upper surface of the horizontal dielectric substrate;

[0012] N dual-port coupled feeding antenna pairs are arranged on two vertical dielectric substrates, N / 2 dual-port coupled feeding antenna pairs are arranged on the inner side of each vertical dielectric substrate, and a gap of a metal ground is arranged between two adjacent dual-port coupled feeding antenna pairs on the same vertical dielectric substrate, which is defined as a spacing gap;

[0013] Each dual-port coupled feed antenna pair includes a shared radiator, two feed branches, two "L"-shaped coupled feed branches and a lumped capacitor; wherein the shared radiator includes a "T"-shaped radiation patch, and a lumped capacitor is arranged at the connection between the longitudinal edge and the transverse edge of the "T"-shaped radiation patch; two "L"-shaped coupled feed branches are arranged below the transverse edge of the "T"-shaped radiation patch, and are mirror-symmetrical about the longitudinal edge of the "T"-shaped radiation patch, and each "L"-shaped coupled feed branch is connected to a feed branch at the end where the vertical dielectric substrate and the horizontal dielectric substrate are connected, and the feed branch is arranged in the gap of the metal ground, and only one feed branch is arranged in each gap of the metal ground, and no feed branch is arranged in the interval gap of the metal ground.

[0014] Furthermore, N pairs of dual-port coupled feeding antennas are symmetrically arranged on two vertical dielectric substrates, and the intervals between the pairs of dual-port coupled feeding antennas on the same vertical dielectric substrate are the same.

[0015] Furthermore, the openings of the two "L"-shaped coupling feeding branches of each dual-port coupling feeding antenna pair face the horizontal dielectric substrate, and the sides of the ends connected to the feeding branches are perpendicular to the horizontal dielectric substrate.

[0016] Furthermore, the outer boundary lines of the two “L”-shaped coupling feeding branches of each dual-port coupling feeding antenna pair do not exceed the boundary lines where the lateral sides of the “T”-shaped radiation patch 3 are located.

[0017] Furthermore, the connected feeding branches are connected to the "L"-shaped coupling feeding branches in a vertical manner.

[0018] The technical solution provided by the present invention brings at least the following beneficial effects:

[0019] The present invention transmits the signal to the shared radiator by electromagnetic coupling, and loads a lumped capacitor in the shared radiator to change the matching impedance of the antenna structure, reduce signal loss, adjust the working frequency range of the antenna, and enable the antenna to maintain effective radiation in a wider frequency range, thereby improving the bandwidth. At the same time, the coplanar waveguide structure is applied to maintain a stable matching impedance in a wider frequency range, while achieving lower cross-coupling and smaller radiation interference.

[0020] The design method of coupled feeding and coplanar waveguide used in the present invention can effectively reduce the size of antenna unit while maintaining broadband characteristics. Through reasonable slot design and lumped capacitor optimization on shared radiators to optimize impedance matching and antenna coupling effect, a MIMO system deploying multiple designed dual-wide-mouth antenna pairs can achieve efficient signal transmission and extremely wide bandwidth, which has important application prospects in 5G communications. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 A schematic diagram of the three-dimensional structure of a MIMO terminal antenna loaded with lumped capacitance according to an embodiment of the present invention;

[0023] Figure 2 for Figure 1 A top view of the antenna structure shown;

[0024] Figure 3 is a three-dimensional schematic diagram of a dual-port coupled feeding antenna pair in an embodiment of the present invention;

[0025] Figure 4 is the reflection coefficient and transmission coefficient of the dual-port coupled feeding antenna pair in the embodiment of the present invention;

[0026] Figure 5 is the radiation pattern of the dual-port coupled feed antenna pair in the embodiment of the present invention;

[0027] Among them, 1 is a horizontal dielectric substrate, 2 is a vertical dielectric substrate, 3 is a "T"-shaped radiation patch, 4 is a metal ground, 5 is a first feeding branch, 6 is a second feeding branch, 7 is a first "L"-shaped coupled feeding branch, 8 is a second "L"-shaped coupled feeding branch, 9 is a lumped capacitor, 4a is a first gap, 4b is a second gap, 4c is a third gap, and 4d is a fourth gap. DETAILED DESCRIPTION

[0028] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in detail and completely in conjunction with the drawings in the implementation of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings can be arranged and designed using different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present invention.

[0029] The embodiment of the present invention provides a MIMO terminal antenna loaded with a lumped capacitor, see Figure 1 , Figure 2 and Figure 3 The MIMO terminal antenna includes a horizontal dielectric substrate 1, two vertical dielectric substrates 2, N shared radiators, a metal ground 4 with 2N+2 slots, and N dual-port coupled feed antenna pairs; wherein N is an integer greater than 1. The dual-port coupled feed antenna pair includes: a shared radiator, two feed branches, two "L"-shaped coupled feed branches and a lumped capacitor 9, that is, the MIMO terminal antenna includes 2N feed branches, N lumped capacitors 9 and 2N "L"-shaped coupled feed branches. The N dual-port coupled feed antenna pairs are arranged on two vertical dielectric substrates, and N / 2 dual-port coupled feed antenna pairs are arranged on the inner side of each vertical dielectric substrate, and a metal ground slot is arranged between two adjacent dual-port coupled feed antenna pairs on the same vertical dielectric substrate to improve the isolation between different antenna pairs.

[0030] Wherein, N depends on the number of deployed antenna pairs. In this embodiment, N is taken as 4 as an example. Figure 1 What is shown is a schematic diagram of the three-dimensional structure of an 8-unit lumped capacitor loaded MIMO terminal antenna, which includes the following components: a horizontal dielectric substrate 1, a metal ground 4 is printed on its upper surface; two vertical dielectric substrates 2 perpendicular to the horizontal dielectric substrate 1, which are respectively located on the two long sides of the horizontal dielectric substrate 1, and the bottom sides are connected to the horizontal dielectric substrate 1, and four dual-port coupled feeding antenna pairs.

[0031] In this embodiment, the bottom edges of the two vertical dielectric substrates 2 are connected to the long sides of the horizontal dielectric substrate 1, and the metal ground 4 filled with 2N+2 gaps is printed on the upper surface of the horizontal dielectric substrate 1. Figure 2As shown. In this embodiment, gaps are respectively opened between the feeding branches of the dual-port coupled feeding antenna pair arranged on the horizontal dielectric substrate 1 and the metal ground 4. Specifically, the gap opened at the first feeding branch 5 of the metal ground 4 is named the first gap 4a, and the gap opened at the second feeding branch 6 of the metal ground 4 is named the second gap 4b. Such a design ensures that after the feeding branches are printed, a certain gap is maintained between the first feeding branch 5 and the second feeding branch 6 and the metal ground 4. The presence of the first gap 4a and the second gap 4b facilitates the feeding of the two ports of each dual-port antenna pair. In addition, in order to improve the isolation between different antenna pairs, a third gap 4c and a fourth gap 4d are opened in the middle of the metal ground 4.

[0032] N shared radiators and 2N "L"-shaped coupled feeding branches are evenly distributed on the inner surface of two vertical dielectric substrates 2. Each shared radiator includes a "T"-shaped radiation patch 3, and a lumped capacitor 9 is set above the short side of the "T"-shaped radiation patch 3 and connected to the long side. The feeding branches are coupled to feed the two ends of the shared radiator through the "L"-shaped coupled feeding branches, such as Figure 3 As shown. And 2N feeding branches are nested in the gaps on both sides of the metal ground 4, namely, the first gap 4a and the second gap 4b. That is, in this embodiment, the dual-port coupled feeding antenna pair includes a "T"-shaped radiation patch 3 arranged on the inner side of the vertical dielectric substrate 2 of the horizontal dielectric substrate 1, a lumped capacitor 9 nested in the connection part of the "T"-shaped radiation patch 3, and the first "L"-shaped coupling feeding branch 7 and the second "L"-shaped coupling feeding branch 8 located below the short side of the "T"-shaped radiation patch 3 are mirror-symmetrical with respect to the long side of the "T"-shaped radiation patch 3. The lumped capacitor 9 plays a key role in improving the isolation of the two ports.

[0033] Preferably, the opening of the “L”-shaped coupling and feeding branch node faces the horizontal dielectric substrate 1 , such as the short side of the “L”-shaped coupling and feeding branch node is perpendicular to the horizontal dielectric substrate 1 .

[0034] Preferably, the outer boundary lines of the first "L"-shaped coupling feed branch 7 and the second "L"-shaped coupling feed branch 8 do not exceed the short side boundary line of the "T"-shaped radiation patch 3 as much as possible. The first feed branch 5 is vertically connected to the first "L"-shaped coupling feed branch 7, and the first feed branch 5 is arranged in the first slot 4a. The second feed branch 6 is vertically connected to the second "L"-shaped coupling feed branch 8, and the second feed branch 6 is arranged in the second slot 4b.

[0035] The design principle of the MIMO terminal antenna loaded with lumped capacitors provided in this embodiment is as follows: in order to meet the development needs of terminal antennas, this embodiment uses an 8-unit MIMO array antenna structure composed of four independent antenna pairs (i.e., dual-port coupled feed antenna pairs), adopts a coplanar waveguide structure combined with coupled feed, introduces a slot structure and lumped capacitor design, and optimizes the coupling characteristics and isolation of the signal by adjusting parameters such as the position and size of the coupling point, reduces the mutual coupling and mutual interference between the dual-port coupled feed antenna pairs, improves the performance of the MIMO antenna system, and meets the terminal antenna's requirements for ultra-bandwidth and miniaturization.

[0036] Example

[0037] In one embodiment, a MIMO terminal antenna loaded with lumped capacitance is provided as a broadband, compact self-decoupling 8-unit MIMO terminal antenna, which is rectangular in shape as a whole, and the physical dimensions of the horizontal dielectric substrate 1 are set to 150mm×75mm×1mm, and the physical dimensions of the vertical dielectric substrate 2 are set to 150mm×7.5mm×1mm. Both the horizontal dielectric substrate 1 and the vertical dielectric substrate 2 can be made of a flame-resistant material FR4 plate with a relative dielectric constant of 4.4 and a loss tangent of 0.02. The physical dimensions of the metal ground 4 are set to 150mm×75mm. The lengths of the first slot 4a and the second slot 4b are both set to 6.5mm, and the widths are both set to 3mm. The lengths of the third slot 4c and the fourth slot 4d are both set to 13mm, and the widths are set to 1mm. The spacing between the dual-port coupled feed antenna pairs on the same side is set to 61mm.

[0038] The physical size of the shared radiator is set to 21mm×6.5mm. A part of the dual-port coupled feed antenna pair is composed of a pair of "T"-shaped radiation patches 3 printed on the side frame. The long side of the "T"-shaped radiation patch 3 is 21mm×1mm, the short side is 5mm×1mm, and the top of the short side is connected to a lumped capacitor 9. The "T"-shaped radiation patch 3 is coupled and fed through a pair of "L"-shaped coupling feed branches printed on the inner side of the side frame. The long side of the "L"-shaped coupling feed branch is set to 5mm×1mm, and the short side is set to 4mm×1mm. A rectangular gap with a length of 6.5mm×3mm is set on the horizontal dielectric substrate 1, wherein a feeding branch with a length of 6mm×1mm is set in the center of the rectangular gap. A lumped capacitor 9 is set above the short side of the "T"-shaped radiation patch 3 and at the connection with the long side. The capacitance of the lumped capacitor 9 is selected to be 1pF. In order to suppress mutual interference between the antenna pairs, a third slot 4c and a fourth slot 4d with a size of 13 mm×1 mm are etched on the metal ground 4.

[0039] In order to better illustrate the radiation performance and isolation of the MIMO terminal antenna loaded with lumped capacitors provided in this embodiment, the MIMO terminal antenna loaded with lumped capacitors provided in this embodiment is simulated below. Due to the symmetry of the 8-unit MIMO terminal antenna, only one dual-port coupled feed antenna pair is studied.

[0040] like Figure 4 As shown, the -6 dB operating frequency band of port 1 is 3.22-5.29 GHz, and the -6 dB operating frequency band of port 2 is 3.22-5.46 GHz, so the overlapping -6 dB operating frequency band of the two antenna units is 3.22-5.29 GHz. The maximum transmission coefficient between the ports is -10.62 dB, and the minimum transmission coefficient (-20.21 dB) can be obtained at 3.22 GHz. While reducing the overall complexity of the dual-antenna module and improving the compactness of the antenna unit, high isolation is achieved. The effective bandwidth under this embodiment is 3.22~5.29 GHz, covering the 5G communication frequency band of the terminal device (N78: 3.3~3.8 GHz; N79: 4.4~5 GHz).

[0041] like Figure 5 As shown in the figure, the main radiation direction of port 1 is biased to the left side of the vertical dielectric substrate, and its gain can reach 4dBi. The main radiation direction of port 2 is perpendicular to the left side of the dielectric substrate, and its gain can reach 6.04 dBi. Since the maximum radiation directions of the two ports are orthogonal to each other, the dual-port antenna pair has good spatial diversity.

[0042] It can be seen that the 8-unit lumped capacitor loaded MIMO terminal antenna provided in this embodiment has a small size and an ultra-wideband effect.

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0044] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A MIMO terminal antenna loaded with lumped capacitance, comprising a horizontal dielectric substrate, two vertical dielectric substrates intersecting the horizontal dielectric substrate, and a metal ground, characterized in that: Also included are N dual-port coupled feed antenna pairs, where N is an even number greater than 1; The bottom sides of the two vertical dielectric substrates are connected to the long sides of the horizontal dielectric substrate, and 2N+2 gaps are opened on the long sides of the metal ground, which is printed on the upper surface of the horizontal dielectric substrate; N dual-port coupled feeding antenna pairs are arranged on two vertical dielectric substrates, N / 2 dual-port coupled feeding antenna pairs are arranged on the inner side of each vertical dielectric substrate, and a gap of a metal ground is arranged between two adjacent dual-port coupled feeding antenna pairs on the same vertical dielectric substrate, which is defined as a spacing gap; Each dual-port coupled feed antenna pair includes a shared radiator, two feed branches, two "L"-shaped coupled feed branches and a lumped capacitor; wherein the shared radiator includes a "T"-shaped radiation patch, and a lumped capacitor is arranged at the connection between the longitudinal edge and the transverse edge of the "T"-shaped radiation patch; two "L"-shaped coupled feed branches are arranged below the transverse edge of the "T"-shaped radiation patch, and are mirror-symmetrical about the longitudinal edge of the "T"-shaped radiation patch, and each "L"-shaped coupled feed branch is connected to a feed branch at the end where the vertical dielectric substrate and the horizontal dielectric substrate are connected, and the feed branch is arranged in the gap of the metal ground, and only one feed branch is arranged in each gap of the metal ground, and no feed branch is arranged in the interval gap of the metal ground.

2. A MIMO terminal antenna loaded with lumped capacitance as claimed in claim 1, characterized in that: N pairs of dual-port coupled feeding antennas are symmetrically arranged on two vertical dielectric substrates, and the intervals between the pairs of dual-port coupled feeding antennas on the same vertical dielectric substrate are the same.

3. A MIMO terminal antenna loaded with lumped capacitance as claimed in claim 2, characterized in that: The spacing between two adjacent dual-port coupled feed antenna pairs located on the same vertical dielectric substrate is 61 mm.

4. A MIMO terminal antenna loaded with lumped capacitance as claimed in claim 1, characterized in that: The openings of the two "L"-shaped coupling feeding branches of each dual-port coupling feeding antenna pair face the horizontal dielectric substrate, and the sides of the ends connected to the feeding branches are perpendicular to the horizontal dielectric substrate.

5. A MIMO terminal antenna loaded with lumped capacitance as claimed in claim 1, characterized in that: The outer boundary lines of the two "L"-shaped coupled feed branches of each dual-port coupled feed antenna pair do not exceed the boundary lines where the lateral sides of the "T"-shaped radiation patch are located.

6. A MIMO terminal antenna loaded with lumped capacitance as claimed in claim 1, characterized in that: The connected feeding branches are connected to the "L"-shaped coupling feeding branches in a vertical manner.

7. A MIMO terminal antenna loaded with lumped capacitance as claimed in any one of claims 1 to 6, characterized in that: The value of N is set to 4.

8. A MIMO terminal antenna loaded with lumped capacitance as claimed in any one of claims 1 to 6, characterized in that: The length of the gap of the metal ground for placing the feeding branch is set to 6.5mm, and the width is set to 3mm; the length of the spacing gap of the metal ground is set to 13mm, and the width is set to 1mm.

9. A MIMO terminal antenna loaded with lumped capacitance as claimed in any one of claims 1 to 6, characterized in that: The length of the lateral side of the "T"-shaped radiation patch is set to 21 mm, and the width is set to 1 mm; the length of the longitudinal side of the "T"-shaped radiation patch is set to 5 mm, and the width is set to 1 mm.

10. A MIMO terminal antenna loaded with lumped capacitance as claimed in any one of claims 1 to 6, characterized in that: The long side of the "L"-shaped coupling feed branch is set to 5mm×1mm, and the short side is set to 4mm×1mm.

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