High-isolation dual-band MIMO antenna based on mode cancellation method

Abstract

The invention relates to the technical field of antennas, and particularly discloses a high-isolation dual-band MIMO antenna based on a mode cancellation method, which comprises a horizontal dielectric substrate and a vertical dielectric substrate placed on one side of the long edge of the horizontal dielectric substrate, and an antenna unit is printed in the middle of the outer side of the vertical dielectric substrate; a first U-shaped gap, a second U-shaped gap and a third U-shaped gap are etched in one side, close to the vertical dielectric substrate, of the metal floor, and the first U-shaped gap and the third U-shaped gap are symmetrically arranged relative to the second U-shaped gap; the first U-shaped gap and the third U-shaped gap are the same in size, and the size of the first U-shaped gap is smaller than that of the second U-shaped gap; a clearance area is arranged on one side, close to the vertical dielectric substrate, of the metal floor. According to the invention, low coupling can be realized in two working frequency bands, the occupied space of the antenna is reduced, and the miniaturization of the antenna is realized.

Description

Technical Field

[0001] This invention relates to the field of antenna technology, and in particular to a high-isolation dual-band MIMO antenna based on a mode cancellation method. Background Technology

[0002] Multiple-input multiple-output (MIMO) technology, as one of the key technologies in 5G communication systems, can significantly improve the spectral efficiency and channel capacity of the system without increasing spectrum resources and transmit power. However, the coupling problem between antenna elements in MIMO antenna systems has become a key bottleneck restricting its performance.

[0003] In MIMO antenna systems, coupling between antenna elements can lead to degraded matching performance, reduced gain, and pattern distortion, thus affecting the overall communication performance of the system. To reduce coupling between antenna elements, researchers have proposed various decoupling methods, mainly including cancellation techniques, blocking techniques, and self-decoupling techniques. Cancellation techniques counteract coupling between antenna elements by introducing additional coupling paths, such as neutralization line techniques and loading decoupling units; blocking techniques block coupling between antenna elements by introducing band-stop structures (such as defective ground structures and electromagnetic bandgap structures); self-decoupling techniques utilize the decoupling characteristics within modes, such as the orthogonality or cancellation characteristics of antenna modes, to achieve decoupling without adding additional decoupling structures. Although the above decoupling methods have achieved some success in single-band MIMO antennas, the complexity and implementation difficulty of decoupling techniques remain high in dual-band (such as N78 and N79 bands) or even multi-band MIMO antennas, requiring further optimization and innovation. Summary of the Invention

[0004] The purpose of this invention is to provide a high-isolation dual-band MIMO antenna based on the mode cancellation method, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the present invention provides a high isolation dual-band MIMO antenna based on the mode cancellation method, comprising a horizontal dielectric substrate and a vertical dielectric substrate, wherein a vertical dielectric substrate is disposed on one side of the long side of the horizontal dielectric substrate, an antenna element is disposed in the middle of the outer side of the vertical dielectric substrate, and a metal ground plane is printed on the lower surface of the horizontal dielectric substrate.

[0006] A second U-shaped slot is etched in the middle of the side of the metal floor closest to the vertical dielectric substrate. A first U-shaped slot and a third U-shaped slot are etched on both sides of the second U-shaped slot, respectively. The first U-shaped slot and the third U-shaped slot are symmetrically arranged with respect to the second U-shaped slot. The first U-shaped slot and the third U-shaped slot have the same size, and the size of the first U-shaped slot and the third U-shaped slot is smaller than the size of the second U-shaped slot.

[0007] A clearance area is provided on the side of the metal floor closest to the vertical dielectric substrate, and the length of the clearance area is equal to the side length of the side of the metal floor where the second U-shaped gap is provided.

[0008] Preferably, the antenna unit includes a first U-shaped metal strip and a second U-shaped metal strip arranged symmetrically, with the U-shaped openings of the first U-shaped metal strip and the second U-shaped metal strip facing away from each other; both the first U-shaped metal strip and the second U-shaped metal strip have metal vias at their ends, and the first U-shaped metal strip and the second U-shaped metal strip are connected to a microstrip feed line through the metal vias.

[0009] Preferably, both the first U-shaped metal strip and the second U-shaped metal strip are composed of a first horizontal microstrip structure, a second vertical microstrip structure and a third horizontal microstrip structure connected in sequence, wherein the length of the first horizontal microstrip structure is greater than the length of the third horizontal microstrip structure; and the metal via is disposed at the end of the third horizontal microstrip structure.

[0010] Preferably, the antenna unit is fed by a coaxial cable.

[0011] Preferably, both the first U-shaped gap and the third U-shaped gap are composed of a first vertical gap, a second horizontal gap, and a third vertical gap connected in sequence; the second U-shaped gap is composed of a first vertical gap, a second horizontal gap, and a third vertical gap connected in sequence.

[0012] Preferably, the horizontal dielectric substrate and the vertical dielectric substrate are made of glass fiber epoxy resin, and the relative permittivity of the glass fiber epoxy resin is εr = 4.4.

[0013] Preferably, the horizontal dielectric substrate has a length of 160 mm, a width of 80 mm, and a thickness of 2 mm;

[0014] The thickness of the vertical dielectric substrate is 1 mm, the height of the vertical dielectric substrate is 12 mm, and the distance between the long side of the horizontal dielectric substrate and the long side of the vertical dielectric substrate is 7 mm.

[0015] Preferably, the microstrip feed line has a length of 11 mm and a width of 1 mm.

[0016] Preferably, the distance between the first U-shaped metal strip and the second U-shaped metal strip is 4 mm;

[0017] The length of the first vertical microstrip structure is 27.5 mm and the height is 5 mm;

[0018] The second horizontal microstrip structure has a length of 2 mm and a height of 2 mm;

[0019] The third vertical microstrip structure has a length of 19mm and a height of 4mm.

[0020] Preferably, the width of the clearance area is 4 mm;

[0021] The outer edge length of the first vertical slit is 10.5 mm, the inner edge length is 10 mm, and the distance between the outer edge and the inner edge is 0.75 mm.

[0022] The outer edge length of the second horizontal gap is 7.5mm, the inner edge length is 6mm, and the distance between the outer edge and the inner edge is 0.5mm;

[0023] The outer edge length of the first vertical slit is 14.5 mm, the inner edge length is 14 mm, and the distance between the outer edge and the inner edge is 0.5 mm.

[0024] The outer edge of the second horizontal gap is 7mm, the inner edge is 6mm, and the distance between the outer and inner edges is 0.5mm.

[0025] Compared with the prior art, the present invention has the following advantages and technical effects:

[0026] The high-isolation dual-band MIMO antenna based on mode cancellation method provided by this invention has a simple antenna structure, reducing design and manufacturing complexity, and can effectively operate in the N77 and N79 sub-bands of Sub 6GHz and the UNII-1 and UNII-2A sub-bands of Wi-Fi 6E / 7. Based on mode cancellation technology, this invention adjusts the common-mode and differential-mode impedances by etching specific slot structures to meet the conditions for mode cancellation, thereby achieving low coupling in two operating frequency bands (2.97GHz-4.22GHz and 4.56GHz-5.33GHz). Furthermore, the U-shaped slots etched in this invention do not occupy additional decoupling space, enabling antenna miniaturization. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic diagram of the high isolation dual-band MIMO antenna based on the mode cancellation method of the present invention.

[0029] Figure 2This is a schematic diagram of the structural dimensions of a high-isolation dual-band MIMO antenna based on the mode cancellation method in an embodiment of the present invention;

[0030] Figure 3 The S-parameter diagram of the high-isolation dual-band MIMO antenna based on the mode cancellation method of this invention is shown.

[0031] Figure 4 This is a Smith chart comparing the common-mode reflection coefficient and differential-mode reflection coefficient of the high-isolation dual-band MIMO antenna based on the mode cancellation method of this invention in the 2.97GHz-4.22GHz band.

[0032] Figure 5 This is a Smith chart comparing the common-mode reflection coefficient and differential-mode reflection coefficient of the high-isolation dual-band MIMO antenna based on the mode cancellation method of this invention in the 4.56GHz-5.33GHz band.

[0033] In the figure: 1. Horizontal dielectric substrate; 2. Vertical dielectric substrate; 3. Antenna element; 4. Metal ground plane; 5. Clearance area; 6. First U-shaped slot; 61. First vertical slot; 62. Second horizontal slot; 63. Third vertical slot; 7. Second U-shaped slot; 71. First vertical slot; 72. Second horizontal slot; 73. Third vertical slot; 8. Third U-shaped slot; 9. First U-shaped metal strip; 91. First horizontal microstrip structure; 92. Second vertical microstrip structure; 93. Third horizontal microstrip structure; 10. Second U-shaped metal strip; 11. Metal via; 12. Microstrip feed line. Detailed Implementation

[0034] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other. The described embodiments are merely some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0035] like Figure 1 As shown, the present invention provides a high isolation dual-band MIMO antenna based on mode cancellation method, including a horizontal dielectric substrate 1, a vertical dielectric substrate 2 disposed on one side of the long side of the horizontal dielectric substrate 1, an antenna element 3 disposed in the middle of the outer side of the vertical dielectric substrate 2, and a metal ground plane 4 printed on the lower surface of the horizontal dielectric substrate 1.

[0036] A second U-shaped slot 7 is etched in the middle of the side of the metal floor 4 closest to the vertical dielectric substrate 2. A first U-shaped slot 6 and a third U-shaped slot 8 are etched on both sides of the second U-shaped slot 7, respectively. The first U-shaped slot 6 and the third U-shaped slot 8 are symmetrically arranged with respect to the second U-shaped slot 7. The first U-shaped slot 6 and the third U-shaped slot 8 have the same size, but the size of the first U-shaped slot 6 and the third U-shaped slot 8 is smaller than the size of the second U-shaped slot 7.

[0037] A clearance area 5 is provided on the side of the metal floor 4 near the vertical dielectric substrate 2. The length of the clearance area 5 is equal to the side length of the side of the metal floor 4 where the second U-shaped gap 7 is provided.

[0038] In a further optimized design, antenna unit 3 includes a first U-shaped metal strip 9 and a second U-shaped metal strip 10 arranged symmetrically, with the U-shaped openings of the first U-shaped metal strip 9 and the second U-shaped metal strip 10 facing away from each other; metal vias 11 are provided at the ends of both the first U-shaped metal strip 9 and the second U-shaped metal strip 10, and microstrip feed lines 12 are connected to the first U-shaped metal strip 9 and the second U-shaped metal strip 10 through the metal vias 11.

[0039] In a further optimized design, the first U-shaped metal strip 9 and the second U-shaped metal strip 10 are both composed of a first horizontal microstrip structure 91, a second vertical microstrip structure 92 and a third horizontal microstrip structure 93 connected in sequence. The length of the first horizontal microstrip structure 91 is greater than the length of the third horizontal microstrip structure 93. The metal via 11 is located at the end of the third horizontal microstrip structure 93.

[0040] To further optimize the design, antenna element 3 is fed using a coaxial cable.

[0041] Further optimization of the scheme: the first U-shaped gap 6 and the third U-shaped gap 8 are both composed of the first vertical gap 61, the second horizontal gap 62 and the third vertical gap 63 connected in sequence; the second U-shaped gap 7 is composed of the first vertical gap 71, the second horizontal gap 72 and the third vertical gap 73 connected in sequence.

[0042] Example

[0043] like Figure 2 As shown, the horizontal dielectric substrate 1 and the vertical dielectric substrate 2 are made of glass fiber epoxy resin, and the relative permittivity of the glass fiber epoxy resin is εr = 4.4.

[0044] Further optimization of the scheme: the length Ls of the horizontal dielectric substrate 1 is 160mm, the width Ws is 80mm, and the thickness Hs is 2mm;

[0045] The thickness ts of the vertical dielectric substrate 2 is 1 mm, the distance t1 between the long side of the horizontal dielectric substrate 1 and the long side of the vertical dielectric substrate 2 is 7 mm, and the height Wss of the vertical dielectric substrate 2 is 12 mm.

[0046] The scheme was further optimized so that the length g1 of the microstrip feeder 12 is 11mm and the width tf is 1mm.

[0047] The scheme was further optimized so that the distance dd between the first U-shaped metal strip 9 and the second U-shaped metal strip 10 is 4mm;

[0048] The length Lp1 of the first horizontal microstrip structure 91 is 27.5 mm, and the height Wp1 is 5 mm.

[0049] The length Dis of the second vertical microstrip structure 92 is 2mm, and the height Wp2 is 2mm;

[0050] The length Lp2 of the third horizontal microstrip structure 93 is 19 mm, and the height Wp3 is 4 mm.

[0051] The plan was further optimized, and the width C1 of the clearance zone 5 was set to 4mm.

[0052] The outer edge length ba1 of the first vertical slit 61 is 10.5mm, the inner edge length ba is 10mm, and the distance pp between the outer edge and the inner edge is 0.75mm.

[0053] The outer edge length aa1 of the second horizontal gap 62 is 7.5mm, the inner edge length aa is 6mm, and the distance pp1 between the outer edge and the inner edge is 0.5mm.

[0054] The outer edge length ba2 of the first vertical gap 71 is 14.5mm, the inner edge length ba3 is 14mm, and the distance between the outer edge and the inner edge qq is 0.5mm.

[0055] The outer edge length aa2 of the second horizontal gap 72 is 7mm, the inner edge length aa3 is 6mm, and the distance between the outer edge and the inner edge qq1 is 0.5mm.

[0056] The high-isolation dual-band MIMO antenna based on the mode cancellation method provided by this invention has antenna elements 3 placed back-to-back. By adjusting the parameters of the first horizontal microstrip structure 91 and the third horizontal microstrip structure 93, the antenna can operate in two frequency bands, namely 2.97GHz-4.22GHz and 4.56GHz-5.33GHz, which can be well applied to 5G communication systems, thereby improving the communication performance and reliability of MIMO systems. Figure 3The S-parameter plot of the antenna is shown. As can be seen from the plot, the antenna covers two frequency bands, and the reflection coefficient is less than -6dB throughout the entire operating frequency band, indicating that the antenna achieves good impedance matching in both frequency bands. Furthermore, according to the mode cancellation theory, when the difference between the common-mode reflection coefficient (Scc11) and the differential-mode reflection coefficient (Sdd11) of a symmetrical and reciprocal two-port antenna system satisfies the formula |Scc11 - Sdd11|... 11 When | < 0.632, decoupling between ports can be achieved. This means that when the distance between the common-mode and differential-mode reflection coefficients on the Smith chart is sufficiently small, the coupling between antenna ports will be significantly suppressed, thereby achieving lower coupling between antenna elements 3. By etching a first U-shaped slot 6 and a third U-shaped slot 8 on the side of the metal ground plane 4 near the vertical dielectric substrate 2, the distance between the common-mode and differential-mode reflection coefficients of the antenna in the 2.97GHz-4.22GHz frequency band is effectively adjusted, achieving higher isolation between antenna elements in this frequency band; at the same time, the introduction of the first U-shaped slot 6 and the third U-shaped slot 8 shifts the common-mode reflection coefficient in the 4.56GHz-5.33GHz frequency band to the upper left half of the inductive region, but the coupling between antenna elements is still relatively large. Based on the above antenna structure, a second U-shaped slot 7 is etched in the middle of the side of the metal ground plane 4 near the vertical dielectric substrate 2, reducing the distance between the common-mode and differential-mode reflection coefficients of the antenna in the 4.56-5.33GHz frequency band, thereby effectively reducing the coupling between antenna elements 3.

[0057] Figure 4 and Figure 5 Smith charts comparing the common-mode reflection coefficient and differential-mode reflection coefficient in the 2.97GHz-4.22GHz and 4.56GHz-5.33GHz frequency bands are presented, respectively. As can be seen from the charts, the distance between the common-mode and differential-mode reflection coefficients is approximately less than 0.632 in both frequency bands, satisfying the decoupling condition of mode cancellation theory. Therefore, this invention exhibits good isolation characteristics in both key frequency bands.

[0058] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-isolation dual-band MIMO antenna based on mode cancellation method, characterized in that, It includes a horizontal dielectric substrate (1) and a vertical dielectric substrate (2). The vertical dielectric substrate (2) is placed on one side of the long side of the horizontal dielectric substrate (1). An antenna unit (3) is printed on the middle of the outer side of the vertical dielectric substrate (2). A metal ground plane (4) is printed on the lower surface of the horizontal dielectric substrate (1). The metal floor (4) has a second U-shaped slot (7) etched in the middle of one side near the vertical dielectric substrate (2). A first U-shaped slot (6) and a third U-shaped slot (8) are etched on both sides of the second U-shaped slot (7). The first U-shaped slot (6) and the third U-shaped slot (8) are symmetrically arranged with respect to the second U-shaped slot (7). The first U-shaped slot (6) and the third U-shaped slot (8) have the same size, and the size of the first U-shaped slot (6) and the third U-shaped slot (8) is smaller than the size of the second U-shaped slot (7). The metal floor (4) has a clearance area (5) on the side close to the vertical dielectric substrate (2), and the length of the clearance area (5) is equal to the side length of the metal floor (4) on the side where the second U-shaped gap (7) is provided.

2. The high-isolation dual-band MIMO antenna based on mode cancellation method according to claim 1, characterized in that, The antenna unit (3) includes a first U-shaped metal strip (9) and a second U-shaped metal strip (10) placed symmetrically, with the U-shaped opening of the first U-shaped metal strip (9) and the U-shaped opening of the second U-shaped metal strip (10) facing away from each other; both the first U-shaped metal strip (9) and the second U-shaped metal strip (10) are provided with metal vias (11), and the first U-shaped metal strip (9) and the second U-shaped metal strip (10) are connected to a microstrip feed line (12) through the metal vias (11).

3. The high-isolation dual-band MIMO antenna based on mode cancellation method according to claim 2, characterized in that, The first U-shaped metal strip (9) and the second U-shaped metal strip (10) are both composed of a first horizontal microstrip structure (91), a second vertical microstrip structure (92) and a third horizontal microstrip structure (93) connected in sequence. The length of the first horizontal microstrip structure (91) is greater than the length of the third horizontal microstrip structure (93). The metal via (11) is disposed at the end of the third horizontal microstrip structure (93).

4. The high-isolation dual-band MIMO antenna based on mode cancellation method according to claim 1, characterized in that, The antenna unit (3) is fed by a coaxial line.

5. The high-isolation dual-band MIMO antenna based on mode cancellation method according to claim 1, characterized in that, The first U-shaped gap (6) and the third U-shaped gap (8) are both composed of a first vertical gap (61), a second horizontal gap (62) and a third vertical gap (63) connected in sequence; the second U-shaped gap (7) is composed of a first vertical gap (71), a second horizontal gap (72) and a third vertical gap (73) connected in sequence.

6. The high-isolation dual-band MIMO antenna based on mode cancellation method according to claim 1, characterized in that, The horizontal dielectric substrate (1) and the vertical dielectric substrate (2) are made of glass fiber epoxy resin, and the relative permittivity of the glass fiber epoxy resin is εr = 4.

4.

7. The high-isolation dual-band MIMO antenna based on mode cancellation method according to claim 6, characterized in that, The horizontal dielectric substrate (1) has a length of 160 mm, a width of 80 mm, and a thickness of 2 mm; The thickness of the vertical dielectric substrate (2) is 1 mm, the height of the vertical dielectric substrate (2) is 12 mm, and the distance between the long side of the horizontal dielectric substrate (1) and the long side of the vertical dielectric substrate (2) is 7 mm.

8. The high-isolation dual-band MIMO antenna based on mode cancellation method according to claim 3, characterized in that, The microstrip feed line (12) has a length of 11 mm and a width of 1 mm.

9. The high-isolation dual-band MIMO antenna based on mode cancellation method according to claim 3, characterized in that, The distance between the first U-shaped metal strip (9) and the second U-shaped metal strip (10) is 4 mm; The first horizontal microstrip structure (91) has a length of 27.5 mm and a height of 5 mm; The second vertical microstrip structure (92) has a length of 2 mm and a height of 2 mm; The third horizontal microstrip structure (93) has a length of 19 mm and a height of 4 mm.

10. The high-isolation dual-band MIMO antenna based on mode cancellation method according to claim 5, characterized in that, The width of the clearance area (5) is 4 mm; The outer edge length of the first vertical slit (61) is 10.5 mm, the inner edge length is 10 mm, and the distance between the outer edge and the inner edge is 0.75 mm. The second horizontal gap (62) has an outer edge length of 7.5 mm, an inner edge length of 6 mm, and a distance of 0.5 mm between the outer and inner edges; The outer edge length of the first vertical slit (71) is 14.5 mm, the inner edge length is 14 mm, and the distance between the outer edge and the inner edge is 0.5 mm; The outer edge length of the second horizontal gap (72) is 7mm, the inner edge length is 6mm, and the distance between the outer edge and the inner edge is 0.5mm.

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