A self-decoupling broadband MIMO mobile terminal antenna

Abstract

The present invention provides a self-decoupling broadband MIMO mobile terminal antenna, comprising a horizontal dielectric substrate, two vertical dielectric substrates intersecting with the horizontal dielectric substrate, a metal ground arranged on the horizontal dielectric substrate, and N dual-port antenna pairs. The dual-port antenna pairs achieve self-decoupling of the two ports through a dual transmission path cancellation method. The total transmission coefficient between the two ports based on the same antenna pair can be decomposed into the sum of the transmission coefficients of two different transmission paths. By selecting the feeding positions of the two ports, when the transmission coefficients of the two transmission paths can cancel each other, the total transmission coefficient between the two ports is zero, and the decoupling characteristics are achieved without adding any additional decoupling structure. The two transmission paths of the present invention will be excited at the same time. When the energy transmitted by the two paths cancel each other, a high degree of isolation can be achieved between the ports. In addition, the shared radiator shape proposed in the present invention further expands the working bandwidth of the two ports.

Description

Technical Field

[0001] The present invention belongs to MIMO wireless communication technology, and in particular relates to a self-decoupling broadband MIMO mobile terminal antenna. Background Art

[0002] MIMO technology can exponentially increase communication system capacity and spectrum utilization without increasing bandwidth, leading to its widespread adoption in 5G mobile devices. However, as mobile devices become thinner and smaller, MIMO antenna design presents significant challenges. To save space, MIMO antennas must be arranged more compactly, but strong coupling between antennas significantly degrades the channel capacity of MIMO systems. Therefore, reducing strong coupling between antennas has become a pressing issue in MIMO antenna design.

[0003] Over the past few years, researchers have conducted extensive research on the decoupling of MIMO antennas. Loading parasitic elements between antennas is the most commonly used method. Compared to the existing coupling path between the antennas, the parasitic elements introduce an additional coupling path. When the currents excited by the two coupling paths are equal in amplitude and opposite in magnitude, the MIMO antenna can achieve perfect decoupling. Etching defective structures into the floor is also a common method. This method can destroy the existing coupling path between the antennas, thereby achieving decoupling. Finally, loading a decoupling network at the antenna feed end is also widely used. Theoretical calculations show that this method can directly feed a current that cancels the current excited by the coupling. All of the above methods require some additional decoupling structures to achieve decoupling, but their bulky size and complex structure make these methods difficult to apply to mobile terminals with limited space.

[0004] Therefore, self-decoupling antenna pairs that do not require additional decoupling structures have attracted increasing attention. The collaborative design of antenna pairs and decoupling is the core of self-decoupling antenna pairs. Orthogonal modes, common-mode-differential-mode cancellation, and the inherent transmission and radiation characteristics of antenna pairs have all been widely used to achieve self-decoupling. However, these methods struggle to achieve both broadband and compactness. In the design of self-decoupling antenna pairs, achieving broadband decoupling in a compact form factor remains a challenging task. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a compact, broadband, self-decoupling and common radiator MIMO mobile terminal antenna pair structure.

[0006] The technical solution adopted by the present invention to solve the above technical problems is a self-decoupling broadband MIMO mobile terminal antenna, comprising a horizontal dielectric substrate, two vertical dielectric substrates intersecting the horizontal dielectric substrate, a metal ground provided on the horizontal dielectric substrate, and N dual-port antenna pairs; N is an integer greater than 1;

[0007] The bottom edges of the two vertical dielectric substrates are connected to the long edges of the horizontal dielectric substrate; a gap exists between the metal ground and the vertical dielectric substrates;

[0008] The dual-port antenna pair includes a shared radiator, two feed lines, and two metallized through-holes; the shared radiator is arranged outside a vertical dielectric substrate; the metallized through-hole is arranged inside the vertical dielectric substrate for connecting the shared radiator and the feed line; the shared radiator includes a rectangular ring; the first metallized through-hole is arranged in the middle of a vertical side of the rectangular ring, and the second metallized through-hole is arranged in the middle of a bottom horizontal side of the rectangular ring;

[0009] The first feed line includes a first feed branch, a second feed branch, a lumped inductor, and a first solder leg; the first metallized through-hole, the first feed branch, the second feed branch, the lumped inductor, and the first solder leg are connected in sequence; wherein the first feed branch is arranged on the inner side of the vertical dielectric substrate, and the second feed branch, the lumped inductor, and the first solder leg are all arranged on the horizontal dielectric substrate; the first feed branch is vertically connected to the second feed branch;

[0010] The second feed line includes a third feed branch, a lumped capacitor, and a second solder pin; the second metallized through hole is connected to the third feed branch, and the third feed branch, the lumped capacitor, and the second solder pin are sequentially connected on the horizontal dielectric substrate;

[0011] N shared radiators in the N dual-port antenna pairs are evenly distributed on the outer surface of a vertical dielectric substrate; a gap exists between the portion of the first feed line and the second feed line disposed on the horizontal dielectric substrate and the metal ground; the gap between the feed branch and the metal ground forms a coplanar waveguide structure;

[0012] The first feeding port excites the dual-port antenna through the first welding pin, while the second feeding port excites the dual-port antenna through the second welding pin; self-decoupling is achieved by mutual cancellation of transmission coefficients of two transmission paths corresponding to the two feeding ports.

[0013] Specifically, the shared radiator includes a rectangular ring and two identical H-shaped patches, and the two H-shaped patches are evenly distributed inside the rectangular ring and connected to the inner circle of the rectangular ring.

[0014] The self-decoupling working principle of the present invention is: according to the signal flow diagram of the microwave network, the total transmission coefficient between the two ports of the same antenna pair can be decomposed into the sum of the transmission coefficients of two different transmission paths. When the transmission coefficients of the two transmission paths can cancel each other, the total transmission coefficient between the two ports is zero, thereby achieving high isolation between the ports. That is, the decoupling characteristics can be achieved without adding any additional decoupling structure. Therefore, by selecting the feeding positions of the two ports, the two transmission paths will be excited at the same time. When the energy transmitted by the two paths cancels each other, a high degree of isolation can be achieved between the ports. The shared radiator shape proposed by the present invention further expands the working bandwidth of the two ports.

[0015] The present invention achieves self-decoupling between the two ports of an antenna pair composed of a shared radiator through a dual-transmission path cancellation method, thereby realizing a compact, broadband two-port antenna pair. Deploying multiple designed two-port antenna pairs can realize a multi-port MIMO system. The present invention has broad application prospects in various mobile terminals. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a three-dimensional structural diagram of the present invention;

[0017] Figure 2 A top view of the present invention;

[0018] Figure 3 is a three-dimensional diagram of a dual-port antenna pair in the present invention;

[0019] Figure 4 A top view of the dual-port antenna pair of the present invention;

[0020] Figure 5 Schematic diagram of transmission path 1 of a dual-port antenna pair;

[0021] Figure 6 Schematic diagram of transmission path 2 of a dual-port antenna pair;

[0022] Figure 7 are the reflection coefficient and transmission coefficient of the two-port antenna pair;

[0023] Figure 8 is the total efficiency and ECC of the two-port antenna pair;

[0024] Figure 9 is the radiation pattern of the two-port antenna pair. DETAILED DESCRIPTION

[0025] In order to better understand the structure and principle of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0026] When N antenna pairs of the present invention are deployed, a 2N-unit MIMO system can be realized. The antenna system includes a horizontal dielectric substrate, two vertical dielectric substrates, N shared radiators, a metal ground with 2N slots, 3N feed branches, N lumped capacitors, N lumped inductors, 2N solder pins, and 2N metalized through-holes. The bottom edges of the two vertical dielectric substrates are connected to the long edges of the horizontal dielectric substrate. A metal ground with 2N slots is printed on the upper surface of the horizontal dielectric substrate. N radiators are evenly distributed on the outer surface of the vertical dielectric substrate. Each shared radiator consists of a rectangular ring and a pair of "H"-shaped patches. Each pair of "H"-shaped patches is evenly distributed on the inner side of the rectangular ring. Each vertical dielectric substrate 2 is evenly distributed with N / 2 shared radiators.

[0027] The shared radiator and feed branches are connected via metalized through-holes, and 2N feed branches are nested in gaps in the metal ground. The ends of the feed branches are connected to corresponding lumped inductors and capacitors. For ease of soldering, solder pins consisting of metal patches are added after the lumped capacitors and inductors. Gaps are left between the sides of the feed branches and the ground to form a coplanar waveguide structure. This coplanar waveguide structure and lumped elements effectively broaden the antenna's operating bandwidth.

[0028] N depends on the number of deployed antenna pairs. In this embodiment, N is taken as 4. The schematic diagram of the 3D structure of the 8-element MIMO array antenna is as follows: Figure 1 As shown, the system comprises a horizontal dielectric substrate 1, two dielectric substrates 2 perpendicular to the substrate 1, four dual-port antenna pairs, and a metal ground plane 4 disposed on the horizontal dielectric substrate 1. The vertical dielectric substrates 2 are arranged on either side of the long sides of the horizontal dielectric substrate 1, with their bottom edges connected to the horizontal dielectric substrate 1. The metal ground plane 4 is printed on the top surface of the horizontal dielectric substrate 1, with a gap between the metal ground plane 4 and the vertical dielectric substrates 2.

[0029] like Figure 2 As shown, a gap is provided between the metal ground 4 and the two feed lines of the dual-port antenna pair disposed on the horizontal dielectric substrate 1. The gap provided in the metal ground 4 at the first feed line is called a first gap 4a, and the gap provided at the second feed line is called a second gap 4b. After printing, a certain gap remains between the first and second feed lines and the metal ground 4. Slots 4a and 4b facilitate feeding of both ports of each dual-port antenna pair.

[0030] like Figure 3As shown, the dual-port antenna pair includes a shared radiator 3 disposed on the outside of a dielectric substrate 2 perpendicular to substrate 1, two feeder lines disposed on the inside of the horizontal dielectric substrate 1 and the vertical dielectric substrate 2, and metallized through-holes (PTHs) 5 and 6, disposed within the vertical dielectric substrate 2, connecting the shared radiator 3 with the two feeder lines. Each shared radiator 3 consists of a rectangular ring and two identical H-shaped patches, evenly distributed within the ring and connected to the inner ring. The first PTH 5 is located in the middle of a side of the rectangular ring parallel to the vertical line of the H-shaped patch, while the second PTH 6 is located in the middle of the bottom side of the rectangular ring parallel to the horizontal line of the H-shaped patch.

[0031] like Figure 4 As shown, the first feed line includes a first feed branch 7, a second feed branch 8, a lumped inductor 10, and a first solder leg 12. The first feed branch 7, the second feed branch 8, the lumped inductor 10, and the first solder leg 12 are connected in sequence, with the first solder leg 12 and the metal ground forming the first feed port. The first feed branch 7 and the second feed branch 8 are vertically connected, forming a vertically bent shape. The first feed branch 7 is disposed inside the vertical dielectric substrate 2, and the second feed branch 8 is disposed on the horizontal dielectric substrate 1. The second feed line includes a third feed branch 9, a lumped capacitor 11, and a second solder leg 13. The third feed branch 9, the lumped capacitor 11, and the second solder leg 13 are connected in sequence, with the second solder leg 13 and the metal ground forming the second feed port.

[0032] like Figure 5 、 6 As shown in the figure, after the dual-port antenna pair is fed, two transmission paths are formed: transmission path 1 passes through most of the shared radiator, while transmission path 2 passes through only a small portion of the shared radiator. Furthermore, the matching area of ​​the two ports is the common part of the two transmission paths. When the energy transmitted by the two paths cancels each other, the port achieves self-decoupling performance.

[0033] Two shared radiators 3 are evenly distributed on each vertical dielectric substrate 2. The shared radiator 3 is connected to the first feed branch 7 via a first plated through-hole 5, while the shared radiator 3 is connected to the third feed branch 9 via a second plated through-hole 6. The first feed branch 7 is printed on the inner surface of the vertical dielectric substrate 2, while the second and third feed branches 8 and 9 are printed in the first and second slots 4a and 4b of the horizontal dielectric substrate 1, respectively. A lumped inductor 10 is connected to the end of the second feed branch 8, while a lumped capacitor 11 is connected to the end of the third feed branch 9. For ease of soldering, a first solder leg 12 is connected to the end of the lumped inductor 10, while a second solder leg 13 is connected to the end of the lumped capacitor 11. The first feed port is excited via the first solder leg 12, while the second feed port is excited via the second solder leg 13. This configuration cancels out the transmission coefficients of the two transmission paths corresponding to the two ports of the antenna pair, achieving decoupling characteristics without adding any additional decoupling structures. The gap between the feed branch and the ground forms a coplanar waveguide structure. The H-shaped patch and the introduction of coplanar waveguide feed achieve broadband and compactness. Without compromising self-decoupling performance, this approach effectively expands the operating bandwidth of both ports, meeting the requirements of mobile terminals.

[0034] Specifically, the broadband, compact, self-decoupling 8-element MIMO array antenna in the embodiment is rectangular in shape. The physical dimensions of the horizontal dielectric substrate are 150mm×75mm×1mm, and the physical dimensions of the vertical dielectric substrate are 150mm×7mm×2mm. The dielectric substrate can be made of FR4 material with a relative dielectric constant of 4.4 and a loss tangent of 0.02. The physical dimensions of the metal ground are 150mm×73mm, and the gap from the vertical dielectric substrate is 1mm. The length of the first gap 4a is 7.5mm and the width is 3mm. The length of the second gap 4b is 5.5mm and the width is 3mm. The spacing between the dual-port antenna pairs on the same side is 68mm.

[0035] The shared radiator has physical dimensions of 20 mm × 7 mm, and electrical dimensions of 0.25λ0 × 0.08λ0, where λ0 is the free-space wavelength corresponding to the center frequency. The spacing between each pair of H-shaped patches is 6 mm. The diameter of the metallized through-hole is 0.8 mm, and the length is 2 mm. The length of the first feed branch 7 is 4 mm, the length of the second feed branch 8 is 6 mm, and the length of the third feed branch 9 is 4 mm. The solder gap reserved for the lumped element is 0.5 mm, and the solder leg is 1.5 mm. The width of the shared radiator, feed branches, and solder legs is 1 mm. The lumped capacitor can be 0.35 pF, and the lumped inductor can be 2 nH.

[0036] When the physical dimensions and capacitance and inductance are selected as above, relatively ideal results can be obtained. If the selected values ​​are changed, the performance of the antenna may deteriorate.

[0037] The above embodiment is simulated and tested. Due to the symmetry of the 8-element MIMO array antenna, only one dual-port antenna pair is studied. Figure 7 As shown in the figure, the -6 dB operating band of port 1 is 3.25-4.4 GHz, while the -6 dB operating band of port 2 is 3.2-4.4 GHz. The overlapping -6 dB operating band of the two ports is 3.3-4.4 GHz. The maximum transmission coefficient between the ports is -12 dB, and the minimum transmission coefficient (-49 dB) is achieved at 3.8 GHz.

[0038] Figure 8 The total efficiency and envelope correlation coefficient (ECC) for both ports are shown. Within the operating frequency band, the total efficiency for port 1 ranges from 46% to 77%, and the total efficiency for port 2 ranges from 53% to 76%. The inter-port ECC is below 0.11 within the operating frequency band.

[0039] like Figure 9 As shown, port 1's primary radiation direction is along the outer surface of the vertical dielectric substrate, achieving a gain of 4.34 dBi. Port 2's primary radiation direction is along the long side of the horizontal dielectric substrate, radiating toward both ends, achieving a gain of 4.91 dBi. Because the maximum radiation directions of the two ports are orthogonal, this dual-port antenna pair exhibits excellent spatial diversity.

[0040] It can be seen that the 8-element MIMO array antenna of the present invention has broadband, compact and self-decoupling effects.

Claims

1. A self-decoupling broadband MIMO mobile terminal antenna, characterized in that: The invention comprises a horizontal dielectric substrate, two vertical dielectric substrates intersecting the horizontal dielectric substrate, a metal ground provided on the horizontal dielectric substrate, and N dual-port antenna pairs; N is an integer greater than 1; The bottom edges of the two vertical dielectric substrates are connected to the long edges of the horizontal dielectric substrate; a gap exists between the metal ground and the vertical dielectric substrates; The dual-port antenna pair includes a shared radiator, two feed lines, and two metallized through-holes; the shared radiator is arranged on the outside of a vertical dielectric substrate; the metallized through-hole is arranged inside the vertical dielectric substrate to connect the shared radiator and the feed line; the shared radiator includes a rectangular ring and two identical H-shaped patches, and the two H-shaped patches are evenly distributed inside the rectangular ring and connected to the inner circle of the rectangular ring; the first metallized through-hole is arranged in the middle of a vertical side of the rectangular ring, and the second metallized through-hole is arranged in the middle of the bottom horizontal side of the rectangular ring; The first feed line includes a first feed branch, a second feed branch, a lumped inductor, and a first solder leg; the first metallized through-hole, the first feed branch, the second feed branch, the lumped inductor, and the first solder leg are connected in sequence; wherein the first feed branch is arranged on the inner side of the vertical dielectric substrate, and the second feed branch, the lumped inductor, and the first solder leg are all arranged on the horizontal dielectric substrate; the first feed branch is vertically connected to the second feed branch; The second feed line includes a third feed branch, a lumped capacitor, and a second solder pin; the second metallized through hole is connected to the third feed branch, and the third feed branch, the lumped capacitor, and the second solder pin are sequentially connected on the horizontal dielectric substrate; N shared radiators in the N dual-port antenna pairs are evenly distributed on the outer surface of a vertical dielectric substrate; a gap exists between the portion of the first feed line and the second feed line disposed on the horizontal dielectric substrate and the metal ground; the gap between the feed branch and the metal ground forms a coplanar waveguide structure; The first feeding port excites the dual-port antenna through the first welding pin, while the second feeding port excites the dual-port antenna through the second welding pin; self-decoupling is achieved by mutual cancellation of transmission coefficients of two transmission paths corresponding to the two feeding ports.

2. The antenna according to claim 1, wherein: When N is 4, an 8-element MIMO array antenna is formed; The physical dimensions of the horizontal dielectric substrate are 150 mm × 75 mm × 1 mm, the physical dimensions of the vertical dielectric substrate are 150 mm × 7 mm × 2 mm, and the physical dimensions of the metal ground are 150 mm × 73 mm, with a gap of 1 mm from the vertical dielectric substrate. The length of the first slot in the metal ground for arranging the first feeder is 7.5 mm and the width is 3 mm. The length of the second slot in the metal ground for arranging the second feeder is 5.5 mm and the width is 3 mm. The spacing between the dual-port antenna pairs on the same side is 68 mm. The physical dimensions of the shared radiator are 20mm×7mm, and the electrical dimensions are 0.25λ0×0.08λ0, which is the free space wavelength corresponding to the center frequency; the spacing between each pair of H-shaped patches is 6mm; the diameter of the metallized through-hole is 0.8mm and the length is 2mm; the length of the first feed branch node 7 is 4mm, the length of the second feed branch node 8 is 6mm, and the length of the third feed branch node 9 is 4mm; the welding gap reserved for the lumped element is 0.5mm; the welding foot is 1.5mm; the width of the shared radiator, feed branch node and welding foot is 1mm.

3. The antenna according to claim 2, wherein: The horizontal dielectric substrate and the vertical dielectric substrate are made of FR4 board with a relative dielectric constant of 4.4 and a loss tangent of 0.

02.

4. The antenna according to claim 2, wherein: The lumped capacitor is selected as 0.35 pF, and the lumped inductor is selected as 2 nH.

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