High-isolation MIMO slot antenna for 5G / WLAN

Abstract

The invention discloses a high-isolation MIMO slot antenna used for 5G / WLAN, the high-isolation MIMO slot antenna comprises an MIMO antenna array, a dielectric substrate and a metal floor which are stacked in sequence, the MIMO antenna array comprises a plurality of groups of antenna units with the same structure, and each group of antenna units comprises an L-shaped antenna unit and a folding monopole unit; the L-shaped antenna unit comprises an L-shaped antenna and a similar T-shaped groove, the similar T-shaped groove is located in the metal floor, and the L-shaped antenna coincides with the similar T-shaped groove along the projection perpendicular to the metal floor; the folding monopole unit comprises a folding monopole antenna and a rectangular groove, the rectangular groove is located in the metal floor, the folding monopole unit coincides with the rectangular groove along the projection perpendicular to the metal floor, and the multiple sets of antenna units of the same structure are evenly distributed on the two long sides of the dielectric substrate. The antenna has the advantages of being simple in structure, wide in frequency band and high in isolation degree.

Description

Technical Field

[0001] The present invention belongs to the field of 5G mobile communications, and in particular relates to a high-isolation MIMO slot antenna for 5G / WLAN. Background Art

[0002] The fifth generation of mobile communications (5G) has been officially put into commercial use. One of its main features is large-capacity and high-speed information transmission. Multiple-input multiple-output (MIMO) technology can effectively improve channel capacity and spectrum efficiency, and is a promising method to meet the needs of large data rates.

[0003] Currently, different countries and operators use different frequency bands for 5G communications. For example, LTE Band 42 (3.4-3.6 GHz) and LTE Band 43 (3.6-3.8 GHz) have been certified and adopted by the European Union; Japan has authorized 5G bands of 3.6 to 4.2 GHz and 4.2 to 4.9 GHz; and the 5170 ~ 5835 MHz band is divided into 5G WLAN (wireless local area network) operating bands.

[0004] For MIMO array antennas used in mobile phones, mutual coupling between MIMO units is inevitable due to the space limitations of mobile phones. Severe mutual coupling will lead to a decrease in isolation, seriously affecting the channel capacity of the MIMO system. Since 5G mobile communications have determined the 3.5 GHz band (3.4-3.6 GHz) and 5 GHz band (4.8-5 GHz), it is necessary to develop a MIMO antenna system that is suitable for both high-isolation 5G communication bands. Summary of the invention

[0005] To solve the above technical problems, the present invention provides a high-isolation MIMO slot antenna for 5G / WLAN, which supports multiple communication modes and improves channel capacity. It is composed of two different types of antenna units: one is an L-shaped antenna unit, which is composed of an L-shaped metal patch and a T-shaped slot, covering the C band (3.4-3.6GHz) of 5G mobile applications; the other is a folded monopole unit, which is composed of a curved metal patch and a rectangular slot, covering 4.5-5.9 GHz, for 5G and WLAN mobile applications. Every two antenna units form a pair, a total of six pairs, forming a 12×12 MIMO antenna array, and each antenna unit can achieve an isolation greater than 11 dB without the need for an additional decoupling structure.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] A high-isolation MIMO slot antenna for 5G / WLAN, comprising a MIMO antenna array, a dielectric substrate, and a metal floor stacked in sequence, wherein the MIMO antenna array comprises a plurality of groups of antenna units with the same structure, and each group of antenna units comprises an L-shaped antenna unit and a folded monopole unit;

[0008] The L-shaped antenna unit comprises an L-shaped antenna and a T-shaped slot, wherein the T-shaped slot is located on the metal floor, and a projection of the L-shaped antenna perpendicular to the metal floor overlaps with the T-shaped slot;

[0009] The folded monopole unit comprises a folded monopole antenna and a rectangular slot, wherein the rectangular slot is located on the metal floor, and the projection of the folded monopole unit perpendicular to the metal floor overlaps with the rectangular slot;

[0010] The T-shaped slot and the rectangular slot, the L-shaped antenna and the folded monopole antenna are all separated by a first preset distance;

[0011] The multiple groups of antenna units with the same structure are evenly distributed on the two long sides of the dielectric substrate.

[0012] Furthermore, the L-shaped antenna includes an L-shaped patch long side, an L-shaped patch short side connected to each other vertically, and a first protruding metal patch connected to the L-shaped patch long side, and the L-shaped patch long side is provided with an L-shaped antenna feeding point for coupling feeding.

[0013] Furthermore, the T-shaped slot includes a U-shaped slot and an I-shaped slot, which is arranged below the L-shaped antenna, one end of the I-shaped slot is connected to the midpoint of the long side of the U-shaped slot, and the other end extends to the edge of the metal floor and is perpendicular to the long side of the metal floor, wherein the length of the I-shaped slot is smaller than the length of the long side of the L-shaped patch, and the projections of the two in the direction perpendicular to the metal floor overlap.

[0014] Furthermore, the folded monopole antenna includes a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, and a second protruding metal patch that are vertically connected in sequence, wherein the first microstrip line, the third microstrip line, and the second protruding metal patch extend along the long side direction close to the metal floor and are respectively perpendicular to the long sides of the metal floor, the second microstrip line extends in a direction close to the L-shaped antenna unit, the fourth microstrip line and the sixth microstrip line extend in a direction away from the L-shaped antenna unit, and the fifth microstrip line extends in a long side direction away from the metal floor.

[0015] Furthermore, the rectangular slot is located below the folded monopole antenna, and except for a portion of the first microstrip line close to the second microstrip line, the projection of the folded monopole antenna along a direction perpendicular to the metal floor falls within the rectangular slot; the feeding point of the folded monopole antenna is located at the portion of the first microstrip line far from the second microstrip line.

[0016] Furthermore, the lower layer of the dielectric substrate is tin-coated according to the structure of the metal floor, and the upper layer of the dielectric substrate is tin-coated according to the structure of the microstrip line.

[0017] The beneficial effects of the present invention are:

[0018] The antenna of the present invention can cover the 3.3-3.6 GHz and 4.5-5.9 GHz frequency bands, with an overall efficiency greater than 75% and an envelope correlation coefficient less than 0.04. It has the advantages of simple structure, wide frequency band, high isolation, and small requirements for antenna clearance area. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a structural diagram of a high-isolation MIMO slot antenna system for 5G / WLAN of the present invention;

[0020] Figure 2 This is a structural diagram of the MIMO array antenna unit of the present invention;

[0021] Figure 3 It is the reflection coefficient simulation result of the MIMO array antenna unit of the present invention;

[0022] Figure 4 The simulation result of the transmission coefficient between the antenna units of the MIMO array antenna of the present invention;

[0023] Figure 5 The radiation pattern of the L-shaped antenna of the MIMO array antenna unit of the present invention when the frequency is equal to 3.5 GHz;

[0024] Figure 6 The radiation pattern of the folded monopole of the MIMO array antenna unit of the present invention when the frequency is equal to 5.0 GHz;

[0025] Figure 7 The radiation efficiency simulation result of the MIMO array antenna system of the present invention;

[0026] Figure 8 Schematic diagram of envelope correlation coefficient of the MIMO array antenna system of the present invention.

[0027] 1. Dielectric substrate; 2. L-shaped antenna; 3. Folded monopole antenna; 4. Metal floor; 5. First protruding metal patch; 6. Long side of L-shaped patch; 7. Short side of L-shaped patch; 8. Feeding point of L-shaped antenna; 9. T-shaped slot; 10. U-shaped slot; 11. I-shaped slot; 12. First microstrip line; 13. Second microstrip line; 14. Third microstrip line; 15. Fourth microstrip line; 16. Fifth microstrip line; 17. Sixth microstrip line; 18. Second protruding metal patch; 19. Feeding point of folded monopole antenna; 20. Rectangular slot. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0029] like Figure 1 As shown, a high isolation MIMO slot antenna for 5G / WLAN includes a dielectric substrate 1, a metal floor 4 is provided at the bottom of the dielectric substrate, and 12 grooves of specific shapes are provided on the surface of the metal floor 4 for carrying 12 antenna units designed by the present invention, including 6 L-shaped antenna units and 6 folded monopole units, 1 L-shaped antenna unit and 1 folded monopole unit as 1 group, a total of 6 groups, and mirror-symmetrical distribution along the long side of the dielectric substrate 1. The length of the entire dielectric substrate 1 is 150 mm, the width is 70 mm, and the height is 0.8 mm. In each group, the L-shaped antenna unit and the folded monopole unit are separated by a preset distance, preferably 8 mm, to form a 12×12 MIMO antenna array.

[0030] The L-shaped antenna unit includes an L-shaped antenna 2 and a T-shaped slot 9; wherein the L-shaped antenna 2 includes an L-shaped patch long side 6, an L-shaped patch short side 7, and a first protruding metal patch 5 connected to the L-shaped patch long side 6, the L-shaped patch long side 6 is provided with an L-shaped antenna feeding point 8 for coupling feeding, and the T-shaped slot 9 is used for impedance matching of the antenna. The T-shaped slot 9 includes a U-shaped slot 10 and an I-shaped slot 11, which are arranged below the L-shaped antenna 2, one end of the I-shaped slot 11 is connected to the midpoint of the long side of the U-shaped slot 10, and the other end extends to the edge of the metal floor 4 and is perpendicular to the long side of the metal floor 4, wherein the length of the I-shaped slot 11 is less than the length of the L-shaped patch long side 6, and the projections of the two along the direction perpendicular to the metal floor 4 overlap.

[0031] The folded monopole unit includes a folded monopole antenna 3 and a rectangular slot 20; wherein the folded monopole antenna 3 includes a first microstrip line 12, a second microstrip line 13, a third microstrip line 14, a fourth microstrip line 15, a fifth microstrip line 16, a sixth microstrip line 17, and a second protruding metal patch 18 which are vertically connected in sequence, wherein the first microstrip line 12, the third microstrip line 14, and the second protruding metal patch 18 extend along the long side direction close to the metal floor 4 and are respectively perpendicular to the long sides of the metal floor 4, and the second microstrip line 13 extends along the long side direction close to the L-shaped The fourth microstrip line 15 and the sixth microstrip line 17 extend in the direction away from the L-shaped antenna unit, and the fifth microstrip line 16 extends in the long side direction away from the metal floor 4; the rectangular slot 20 is located below the folded monopole antenna 3, and except for a portion of the first microstrip line 12 close to the second microstrip line 13, the projection of the folded monopole antenna 3 in the direction perpendicular to the metal floor 4 falls within the rectangular slot 20; the folded monopole antenna feeding point 19 is located at the portion of the first microstrip line 12 away from the second microstrip line 13. The structure is simple, the antenna clearance area requirement is small, and the radiation efficiency is high.

[0032] Preferably, the folded monopole antenna 3 adopts the following parameters: 7×1 mm 2 The first microstrip line 12,5×1mm 2 The second microstrip line 13, 4.4 × 1 mm 2 The third microstrip line 14, 9.5×0.6 mm 2 The fourth microstrip line 15,5×0.5mm 2 The fifth microstrip line 16, 4 × 1 mm 2 The sixth microstrip line 17 and 0.5×0.5 mm 2 The second protruding metal patch 18. The rectangular groove 20 has a length of 17 mm and a width of 6 mm.

[0033] Preferably, the short side 7 of the L-shaped patch is 5.5 mm long and 1.5 mm wide, and is located on the top of the dielectric substrate; the long side 6 of the L-shaped patch is 8 mm long and 2 mm wide; the first protruding metal patch 5 is 0.5×0.5 mm 2 .

[0034] Preferably, the long side of the U-shaped groove 8 is 7.5 mm in length and 1.5 mm in width, and the length and width of the protruding parts on both sides are both 0.5 mm; the length of the I-shaped groove 9 is 4 mm and 1.5 mm in width.

[0035] The interval between the center of the T-shaped slot 9 and the center of the adjacent rectangular slot 20 is 8 mm.

[0036] The dielectric substrate 1 is FR4, with a dielectric constant of 4.4 and a height of 0.8 mm. One side is tinned according to the structure of a microstrip line; the other side is tinned according to the structure of a floor, serving as an infinite ground plane.

[0037] Example

[0038] Using circuit board etching technology, a 0.8 mm thick PCB board is etched on one side. Figure 1 The size of the entire dielectric substrate 1 is 150×75×0.8 mm 3 The positions of the feeding points are formed according to the non-tin-covered punching process. At the same time, the etching technology is also used to etch out the other side of the 0.8 mm thick FR4 substrate according to the above parameters. Figure 2 Microstrip line structure.

[0039] The MIMO system was simulated using the electromagnetic simulation software ANSYS Electronics Desktop 2021, and the simulation results were obtained after debugging. Figure 3The relationship between the simulated reflection coefficient of each antenna unit and the antenna frequency is shown. It can be seen that the reflection coefficient of the L-shaped antenna unit in the working frequency band is -10 dB, while the reflection coefficient of the folded monopole antenna unit in the working frequency band is greater than -6 dB. Since the antenna units are symmetrically distributed on the left and right sides of the substrate, they have the same reflection characteristics and transmission characteristics. Figure 3 and Figure 4 Only the 6 antennas on the left side of the array are shown (e.g. Figure 1 The result is that there are 6 antennas in 3 groups on the left side along the long side of the dielectric substrate 1, which are recorded as Ant1 to Ant6. Figure 4 It can be seen that in the required 5G mobile application frequency band and WLAN frequency band, the isolation of each unit is above 11 dB, indicating that the degree of coupling between antenna units is very small.

[0040] Taking the results of Ant1 and Ant2 (the first group of antenna elements, Ant1 represents the L-shaped antenna element, and Ant2 represents the folded monopole element) as representatives, the directional patterns (E plane and H plane) of the L-shaped antenna element and the folded monopole antenna element in the proposed 12-element MIMO antenna array measured at two representative frequencies (3.5 GHz in the low frequency band and 5.0 GHz in the high frequency band) are discussed and analyzed respectively. Figure 5 As shown in Figure 1, at 3.5 GHz, Ant1 has higher radiation efficiency between 210° and 330° in the YOZ plane, and basically achieves omnidirectional radiation in the XOZ plane. Similarly, at high frequencies, such as Figure 6 As shown in the figure, Ant2 can achieve directional radiation from 180° to 360° at 5.0 GHz with the gain value unchanged, which indicates that Ant2 has strong directional radiation performance. Figure 7 is the radiation efficiency of the L-shaped antenna unit and the folded monopole unit (taking Ant1 and Ant2 as examples). Obviously, the radiation efficiency of the two units of this antenna model is above 75%.

[0041] Figure 8 The envelope correlation coefficient (ECC) curve of the antenna unit calculated by formula (1) is:

[0042] (1)

[0043] ECC is one of the key indicators used to evaluate the performance of MIMO antenna arrays. The definition of ECC is mainly to quantify the independence of signal transmission between different antenna elements in a MIMO antenna array. The lower the ECC value, the higher the independence of signal transmission between antenna elements in a MIMO antenna array. Figure 8It can be seen that in the entire operating frequency range, the ECC values ​​calculated by the proposed 12-element MIMO antenna are all less than 0.03, thus showing good diversity performance.

[0044] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A high isolation MIMO slot antenna for 5G / WLAN, characterized in that: It includes a MIMO antenna array, a dielectric substrate, and a metal floor stacked in sequence, wherein the MIMO antenna array includes multiple groups of antenna units with the same structure, and each group of antenna units includes an L-shaped antenna unit and a folded monopole unit; The L-shaped antenna unit comprises an L-shaped antenna and a T-shaped slot, wherein the T-shaped slot is located on the metal floor, and a projection of the L-shaped antenna perpendicular to the metal floor overlaps with the T-shaped slot; The folded monopole unit comprises a folded monopole antenna and a rectangular slot, wherein the rectangular slot is located on the metal floor, and the projection of the folded monopole unit perpendicular to the metal floor overlaps with the rectangular slot; The T-shaped slot and the rectangular slot, the L-shaped antenna and the folded monopole antenna are all separated by a first preset distance; The multiple groups of antenna units with the same structure are evenly distributed on the two long sides of the dielectric substrate.

2. A high isolation MIMO slot antenna for 5G / WLAN according to claim 1, characterized in that: The L-shaped antenna includes an L-shaped patch long side, an L-shaped patch short side connected to each other vertically, and a first protruding metal patch connected to the L-shaped patch long side. The L-shaped patch long side is provided with an L-shaped antenna feeding point for coupling feeding.

3. The high isolation MIMO slot antenna for 5G / WLAN according to claim 1, characterized in that: The T-shaped slot includes a U-shaped slot and an I-shaped slot, which are arranged below the L-shaped antenna. One end of the I-shaped slot is connected to the midpoint of the long side of the U-shaped slot, and the other end extends to the edge of the metal floor and is perpendicular to the long side of the metal floor. The length of the I-shaped slot is smaller than the length of the long side of the L-shaped patch, and the projections of the two in the direction perpendicular to the metal floor overlap.

4. The high isolation MIMO slot antenna for 5G / WLAN according to claim 1, characterized in that: The folded monopole antenna includes a first microstrip line, a second microstrip line, a third microstrip line, a fourth microstrip line, a fifth microstrip line, a sixth microstrip line, and a second protruding metal patch, which are vertically connected in sequence, wherein the first microstrip line, the third microstrip line, and the second protruding metal patch extend along the long side direction close to the metal floor and are respectively perpendicular to the long sides of the metal floor, the second microstrip line extends in the direction close to the L-shaped antenna unit, the fourth microstrip line and the sixth microstrip line extend in the direction away from the L-shaped antenna unit, and the fifth microstrip line extends in the long side direction away from the metal floor.

5. The high isolation MIMO slot antenna for 5G / WLAN according to claim 1, characterized in that: The rectangular slot is located below the folded monopole antenna, and except for a portion of the first microstrip line close to the second microstrip line, the projection of the folded monopole antenna in a direction perpendicular to the metal floor falls within the rectangular slot; The feeding point of the folded monopole antenna is located at a portion of the first microstrip line away from the second microstrip line.

6. The high isolation MIMO slot antenna for 5G / WLAN according to claim 1, characterized in that: The lower layer of the dielectric substrate is tin-coated according to the structure of the metal floor, and the upper layer of the dielectric substrate is tin-coated according to the structure of the microstrip line.

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