Structure and method for improving antenna isolation in MIMO systems

Abstract

The present invention proposes a structure and method for improving antenna isolation of a MIMO system, comprising: an isolation unit and two etching grooves on both sides of the isolation unit, which are arranged on a metal antenna bottom plate and located between two antennas with a spacing greater than half the antenna working wavelength; the isolation unit is a double-arm inverted L-shaped structure composed of two L arms. It can be applied to the isolation improvement of the current indoor and outdoor small base station omnidirectional antennas, has replicability and a simple and fast design, and significantly improves isolation. Compared with neutral line decoupling and resonator decoupling, there is no need for additional matching design of the input port, and the design is more flexible. Compared with metamaterial decoupling, the design is simpler, the cost is lower, and the structural compatibility is stronger.

Description

Technical Field

[0001] The present invention belongs to the technical field of wireless communications, and in particular relates to a structure and method for improving antenna isolation of a MIMO system. Background Art

[0002] With the development of modern communication technology, the application of MIMO technology has penetrated into all common base stations and terminals. A key indicator in MIMO technology is antenna isolation. When the isolation between antennas is insufficient, the communication capability of the MIMO system will decrease. For the MIMO communication systems in the industry, in general, the antenna isolation requirement is above 20dB, and the higher the better.

[0003] In the early days of MIMO technology application, 2*2 and 4*4 were the mainstream communication systems. At that time, due to the small number of antennas and sufficient spacing between antennas, good isolation between antennas could be achieved through reasonable design and layout. As society develops and progresses, people's demands for the speed and capacity of communication systems are getting higher and higher, so MIMO systems begin to support more antennas. 8*8 or even more antennas will appear in base stations and terminals. However, due to external factors such as appearance, wind resistance and portability, the size of communication equipment will not increase significantly, at least not by multiples. For this reason, the space left for antennas inside the communication system becomes increasingly tight, the spacing between antennas decreases, and the isolation decreases, which will affect the performance of the MIMO system.

[0004] In recent years, more and more research has been conducted on antenna decoupling technology. A good decoupling design can effectively change the isolation between antennas. It is mainly divided into three types: neutral line decoupling, resonator decoupling and metamaterial decoupling technology. The first two technologies are designed near the antenna input port, and the latter technology acts on the near field of antenna radiation. At present, these technologies are mainly used in extremely small indoor base stations and terminals and large outdoor base station antennas.

[0005] For most of the current indoor base station products, due to the increase in the number of MIMO antennas and the unchanged or even reduced volume, the design of MIMO antennas is different from that of very small base stations and terminals. It is necessary to pay attention not only to the efficiency of the antenna and the isolation between antennas, but also to the changes in the directional pattern of each omnidirectional antenna, and try to ensure that the horizontal radiation of the omnidirectional antenna is uniform while the isolation is satisfied. At present, the spacing between antennas in most indoor base station products can still be larger than the near field of omnidirectional antenna radiation. In this case, in order to improve the isolation of the antenna, the general design is to use cross-polarized antennas or rotate the direction of the antenna. The former has a good effect on improving isolation, but the efficiency and coverage of horizontally polarized antennas are not as good as those of vertically polarized antennas, and horizontally polarized antennas need to occupy a large space in the low frequency band, which is a compromise consideration. The latter is to find the zero point of antenna radiation and align the zero point position with the adjacent antenna to improve the isolation between antennas. However, this method is not suitable for antennas with good omnidirectional radiation, and since there are often more than one adjacent antenna, it is often difficult to take both into account. Therefore, this method is relatively blind and is not a system design idea. Summary of the invention

[0006] In view of the defects and shortcomings of the prior art, the present invention aims to provide a structure and method that can improve the antenna isolation of the MIMO system, so as to ensure that the communication performance of the MIMO system can be optimized.

[0007] The main application design scenario of the present invention is the built-in omnidirectional base station antenna indoors and outdoors. The antenna is mainly placed on a metal plate to ensure the design decoupling of the antenna and the circuit, and the spacing between the antennas is more than half a wavelength.

[0008] The present invention specifically adopts the following technical solutions:

[0009] A structure for improving antenna isolation of a MIMO system, characterized in that it includes: an isolation unit and two etching grooves located on both sides of the isolation unit, which are arranged on a metal antenna bottom plate and located between two antennas with a spacing greater than half the antenna working wavelength; the isolation unit is a double-arm inverted L-shaped structure composed of two L arms.

[0010] Preferably, the total length of the two L arms is 1 / 4 of the antenna operating wavelength.

[0011] Preferably, the lengths of the two L arms are different.

[0012] Preferably, the length of the etching groove is 1 / 2 of the working wavelength of the antenna.

[0013] Preferably, the distance between the etching groove and the phase center of the working antenna is 1 / 4 of the working wavelength.

[0014] Preferably, the shape of the etching groove is a straight line or an arc with the antenna phase center as the center.

[0015] Preferably, the two antennas are two PIFA antennas arranged in parallel.

[0016] And, a method for improving antenna isolation of a MIMO system, characterized in that: an isolation unit and two etching grooves located on both sides of the isolation unit are set on a metal antenna base plate between two antennas; the isolation unit is a double-arm inverted L-shaped structure composed of two L arms.

[0017] Preferably, the total length of the two L arms is adjusted based on 1 / 4 of the antenna operating wavelength to optimize the isolation and isolation bandwidth.

[0018] Preferably, the length of the etching groove is adjusted based on 1 / 2 of the antenna working wavelength; the phase center distance of the etching groove from the working antenna is adjusted based on 1 / 4 of the antenna working wavelength; so that the isolation and isolation bandwidth are optimized.

[0019] Compared with the prior art, the present invention and its preferred solution can be applied to improving the isolation of the current indoor and outdoor small base station omnidirectional antennas. It is reproducible and has a simple and quick design, with a significant improvement in isolation. Compared with neutral line decoupling and resonator decoupling, there is no need for additional matching design of the input port, and the design is more flexible. Compared with metamaterial decoupling, the design is simpler, the cost is lower, and the structural compatibility is stronger.

[0020] The design of isolation unit + etching groove can improve the isolation between antennas by about 8~10dB. For the design of such built-in antennas, it is sufficient to meet the antenna isolation requirements of the MIMO system while ensuring the antenna efficiency.

[0021] It is possible to obtain similar effects to the present invention by using metamaterials, but in comparison, the design is complex, the design cycle is long, and the design may have a disadvantage of having a greater impact on the horizontal radiation non-circularity of the antenna pattern. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0023] Figure 1 A schematic diagram of an embodiment of the present invention is shown;

[0024] Figure 2 This is a schematic diagram of the isolation performance before and after the use of the embodiment of the present invention;

[0025] Figure 3 A schematic diagram of the circularity of horizontal radiation of front and rear antennas using an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of standing wave performance before and after the use of the embodiment of the present invention;

[0027] In the figure: 1-first antenna; 2-second antenna; 3-isolation unit; 4-first isolation slot; 5-second isolation slot; 6-metal antenna base plate. DETAILED DESCRIPTION

[0028] In order to make the features and advantages of this patent more obvious and easy to understand, the following embodiments are specifically described in detail as follows:

[0029] like Figure 1 As shown, the structure provided in this embodiment that can improve the antenna isolation of the MIMO system includes an isolation unit 3 for influencing the electromagnetic field radiated by the antenna and two etching grooves on both sides of the isolation unit 3 (including a first isolation groove 4 and a second isolation groove 5). Among them, the isolation unit 3 adopts a double-arm inverted L-shaped structure (such as Figure 1 The L arms of L1 and L2).

[0030] In this embodiment, the total length of the L arm is approximately 1 / 4 of the antenna working wavelength. The lengths of the two L arms can be slightly different. The isolation and the corresponding bandwidth can be adjusted by adjusting the lengths of the two arms. Generally, the preferred total length can be 1 / 4 of the antenna working wavelength to achieve the optimal isolation.

[0031] The length of the two etching grooves is about 1 / 2 of the antenna working wavelength, and the distance between the etching groove and the phase center of the working antenna is about 1 / 4 of the working wavelength. The shape of the etching groove can be a straight line or an arc with the antenna phase center as the center. The isolation and the corresponding bandwidth can be adjusted by adjusting the length of the etching groove. Generally, the length of the etching groove is taken as 1 / 2 of the antenna working wavelength, and the distance between the etching groove and the phase center of the working antenna is taken as 1 / 4 of the working wavelength. This can ensure that the impact on the antenna standing wave is small, and at the same time, the isolation and isolation bandwidth between antennas can be further improved.

[0032] Figure 1 This is a specific implementation case of the present embodiment, which is applied to two PIFA antennas (including the first antenna 1 and the second antenna 2) working in 5G N41 (China Mobile allocated frequency band), the material of the metal antenna base plate 6 is aluminum plate, and the distance between the first antenna 1 and the second antenna 2 is more than half a wavelength.

[0033] Figure 2 It is the specific effect of this embodiment, before represents before adopting the scheme of this embodiment, and after represents the simulation result after using the scheme of this embodiment. When using the scheme of this embodiment, under the premise of ensuring that the standing wave and directional pattern performance of antenna 1 and antenna 2 in the N41 frequency band do not change much, the isolation is improved by more than 10dB.

[0034] Figure 3 This is the impact of this embodiment on the horizontal plane gain of the antenna. It can be seen that this embodiment has little impact on the horizontal radiation characteristics of the antenna, and the roundness of the horizontal radiation of the antenna is not deteriorated.

[0035] Figure 4 It is the influence of this embodiment on the standing wave performance of the antenna. It can be seen that before and after the implementation, the standing wave performance of the antenna has not deteriorated within the required bandwidth. In this way, this embodiment only optimizes the isolation of the antenna and does not deteriorate other performances of the antenna.

[0036] This patent is not limited to the above-mentioned optimal implementation mode. Anyone can derive other various forms of structures and methods for improving antenna isolation of MIMO systems under the inspiration of this patent. All equal changes and modifications made according to the scope of the patent application of the present invention should be covered by this patent.

Claims

1. A structure for improving antenna isolation in a MIMO system, characterized in that: include: An isolation unit and two etching grooves located on both sides of the isolation unit are arranged on the metal antenna bottom plate and are located between two antennas whose spacing is greater than half of the antenna working wavelength; The isolation unit is a double-arm inverted L-shaped structure consisting of two L arms; The total length of the two L arms is 1 / 4 of the antenna operating wavelength; The lengths of the two L arms are different; The length of the etching groove is 1 / 2 of the antenna working wavelength; The distance between the etching groove and the phase center of the working antenna is 1 / 4 of the working wavelength.

2. The structure for improving antenna isolation of a MIMO system according to claim 1, characterized in that: The shape of the etching groove is a straight line or an arc with the antenna phase center as the center.

3. The structure for improving antenna isolation of a MIMO system according to claim 1, characterized in that: The two antennas are two PIFA antennas arranged in parallel.

4. A method for improving antenna isolation of a MIMO system, characterized by: An isolation unit and two etching grooves located on both sides of the isolation unit are arranged on the metal antenna bottom plate between the two antennas; the isolation unit is a double-arm inverted L-shaped structure composed of two L arms; Based on 1 / 4 of the antenna operating wavelength, the total length of the two L arms is adjusted to optimize the isolation and isolation bandwidth; Adjust the length of the etching groove based on 1 / 2 of the antenna operating wavelength; Based on 1 / 4 of the antenna working wavelength, the phase center distance between the etching groove and the working antenna is adjusted to optimize the isolation and isolation bandwidth.

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