Microstrip MIMO antenna with wide working frequency band and wide decoupling frequency band

Abstract

The invention discloses a microstrip MIMO antenna with a wide working frequency band and a wide decoupling frequency band, particularly relates to the technical field of microwave and millimeter wave communication, and solves the problems that most of the microstrip MIMO antenna mutual decoupling technologies in the prior art cannot be suitable for multimode broadband MIMO antennas; the technical problems that effective multi-mode mutual coupling suppression can be achieved only by additionally introducing a large-size metal structure or a stacked patch structure in a mutual coupling removal technology suitable for a multi-mode broadband MIMO antenna, and a high-integration-level planar broadband compact low-mutual-coupling MIMO antenna design scheme is lacked are solved. According to the technical scheme, on the basis of a single-layer planar microstrip antenna, a parasitic structure is loaded between two antenna units, and an antenna unit self-decoupling scheme is combined for design; the microstrip MIMO antenna is high in integration level and has a wide working frequency band and a wide decoupling frequency band at the same time.

Description

Technical Field

[0001] The invention relates to the field of microwave and millimeter wave communications, and in particular to a microstrip MIMO antenna with a wide operating frequency band and a wide decoupling frequency band. Background Art

[0002] The iterative development of communication technology has led to a continuous increase in the demand for communication capacity. Using MIMO technology to increase channel capacity has become a key measure in the design of communication systems. However, when designing antennas, the spacing between antenna elements often needs to be strictly limited in order to avoid grating lobes, adjust beam shape, and control gain. The limited spacing between elements can easily lead to uncontrollable strong mutual coupling between array elements, resulting in a series of problems such as deterioration of active matching of multi-element antenna arrays, radiation distortion, increased bit error rate of communication systems, and deterioration of channel capacity. Therefore, it is necessary to explore methods to reduce the mutual coupling between MIMO antenna elements.

[0003] Microstrip antennas have several advantages, such as low profile, easy integration, low cost, and mature manufacturing process. However, most of the existing microstrip antenna decoupling technologies are only suitable for narrowband microstrip antennas working in single mode (i.e., the absolute working bandwidth is less than 200MHz). When the antenna mode increases and the working bandwidth is widened to more than 300MHz, the narrowband decoupling solution will face the dilemma that the decoupling bandwidth is difficult to cover the working bandwidth, resulting in only a single frequency point or only a part of the frequency band in the wide working frequency band having a reliable mutual coupling level, which is difficult to apply in practice. There are two main ideas for the decoupling scheme that can be applied to multi-mode broadband antennas. The first is to use a large current blocking structure, such as a high and thick metal wall or block, to directly cut off the coupling induction current of the entire working frequency band, so as to achieve a flat decrease in the intra-band mutual coupling between units. However, this scheme will cause a significant increase in the size of the antenna and is not easy to integrate. The second is to use a multi-resonator structure to achieve multi-mode cancellation, that is, to use a single or multiple parasitic radiation structures to construct anti-phase coupling paths for different radiation modes, and introduce reverse currents on the coupling units at different frequencies. However, the existing feasible solutions under this idea are only applicable to microstrip patch antennas with stacked structures, and will cause one or more problems including reduced in-band gain, increased size, and reduced bandwidth.

[0004] Therefore, most of the existing microstrip MIMO antenna decoupling technologies are not applicable to multi-mode broadband antennas; the decoupling technologies applicable to multi-mode broadband antennas require the additional introduction of large-volume metal structures or stacked patch structures to achieve effective multi-mode mutual coupling suppression, and lack a highly integrated planar broadband compact low-mutual coupling MIMO antenna design solution. Summary of the invention

[0005] Therefore, the present invention solves the technical problems that most of the microstrip antenna decoupling technologies in the prior art are not applicable to multi-mode wide-band antennas; the decoupling technologies applicable to multi-mode wide-band antennas require the additional introduction of large-volume metal structures or stacked patch structures to achieve effective multi-mode mutual coupling suppression, and lack a highly integrated planar broadband compact low-mutual coupling antenna design scheme; the present invention provides a microstrip MIMO antenna with a wide operating frequency band and a wide decoupling frequency band, which is based on a single-layer planar microstrip antenna, and realizes a highly integrated microstrip MIMO antenna with a wide operating frequency band and a wide decoupling frequency band by loading a group of parasitic structures between two antenna units and combining the antenna unit self-decoupling scheme design.

[0006] The present invention provides a microstrip MIMO antenna with a wide operating frequency band and a wide decoupling frequency band, comprising a top metal structure, a first dielectric substrate and a metal ground arranged in sequence from top to bottom; the feeding probe vertically passes through the top metal structure, the first dielectric substrate and the metal ground, and is connected to the top metal structure, the first dielectric substrate and the metal ground.

[0007] Furthermore, the first dielectric substrate includes two symmetrically arranged slot-loaded square metal patches, and a central grounded rectangular patch structure group is arranged between the two metal patches.

[0008] Furthermore, a long strip-shaped metal groove is etched on the metal patch.

[0009] Furthermore, each of the two metal patches is connected to the metal ground through a row of grounding metal vias.

[0010] Furthermore, the two metal patches are respectively excited by feeding probes to form two half-mode microstrip patch antenna units.

[0011] Furthermore, the rectangular patch structure group includes eight rectangular patches.

[0012] Furthermore, the eight rectangular patches are respectively provided with grounding through holes connected to the metal ground, forming a mushroom-like shape, and thus can be named a mushroom-shaped structure.

[0013] Furthermore, the grounding through hole is located at the center of the rectangular patch.

[0014] Furthermore, each of the two square metal patches is etched with a long metal groove, one side of each patch is connected to the metal ground through a row of grounding metal vias, and the unit excitation is achieved by feeding probes respectively, forming two half-mode microstrip patch antenna units.

[0015] Furthermore, the length of the rectangular patch in the mushroom shape is 0.25λ g -0.3λ g ,λ gis the wavelength of the waveguide corresponding to the center frequency of the antenna, and its width is 0.08λ g -0.1λ g , the patch spacing is 0.01λ g -0.03λ g , the center ground via diameter is 0.01λ g -0.02λ g ; The length of the long strip metal slot of the top metal patch of the microstrip patch antenna unit is 0.65λ g -0.7λ g , with a width of 0.15λ g -0.2λ g , 0.28λ from the edge of the patch g -0.32λ g .

[0016] Furthermore, for the two-unit antenna structure, when a signal is fed into the port of unit one and an impedance-matched load is connected to the port of unit two, the signal excites the corresponding metal patch in the top metal structure through the feeding probe of unit one, and obtains two resonant modes, forming the radiation of unit one. When unit one radiates, the signal is coupled to unit two through multiple coupling paths controlled by the mushroom-shaped structure group, forming mutual coupling between unit one and unit two. The lower the mutual coupling level, the lower the mutual interference between the two units, that is, the more independent the channels corresponding to the two ports. After swapping the feeding port and the load port, the signal transmission process is similar to the above.

[0017] Furthermore, if Figure 3 The port reflection coefficient of the microstrip MIMO antenna proposed in this invention is shown. Under the single-ended excitation condition, each half-mode microstrip patch antenna unit has two resonant modes, namely TM 0，2 Die and TM 3 / 2，0 mode; at the same time, three mutual coupling zeros can be achieved. The first mutual coupling zero is caused by the mushroom-shaped structure group between the two antenna units, which is a high impedance resonant structure. At the corresponding frequency point, the periodic structure does not support any transverse electric and transverse magnetic waves to pass through, and the group is approximately a band-stop filter structure, that is, it constitutes an "electromagnetic band gap". The second mutual coupling zero is due to the two resonant modes (TM) of the planar microstrip patch unit. 0，2 Die and TM 3 / 2，0 The distribution direction of the near-field components of the two modes is orthogonal. After the two-mode radiation signals are transmitted through the path, they are superimposed at the port of the coupled unit and cancel each other out in reverse phase, making the port of the coupling unit located in a "weak field area", that is, the coupling current flowing into the port of the coupling unit is very small, realizing mode cancellation type self-decoupling. The third mutual coupling zero point is due to the fact that the top surface of the mushroom-shaped structure group can be approximated as a half-wavelength resonator in the horizontal direction. At this frequency point, the TM of the planar microstrip antenna 3 / 2，0The signal coupled to another unit through the mushroom-shaped structure group half-wavelength resonator is a direct coupling signal, and the signal coupled to another unit through the mushroom-shaped structure group half-wavelength resonator is an indirect coupling signal. The two signals cancel each other out in the process of path transmission, making the signal transmitted to the coupling unit weak.

[0018] Furthermore, for the microstrip MIMO antenna with a wide operating frequency band and a wide decoupling frequency band, its first resonant mode TM 0，2 The mode can be controlled by adjusting the length of the square metal patch in the vertical direction. The second resonance mode TM 3 / 2，0 The mode can be controlled by adjusting the width of the long metal slot. The first mutual coupling zero point can be controlled by changing the diameter of the grounding through hole in the mushroom-shaped structure group or the horizontal length of the rectangular patch in the top metal structure. The second mutual coupling zero point can be controlled by adjusting the vertical length of the square metal patch or adjusting the width of the long metal slot. The third mutual coupling zero point can be controlled by adjusting the horizontal length of the rectangular patch in the top metal structure.

[0019] In the above technical solution, the technical effects and advantages provided by the present invention are:

[0020] 1. The microstrip MIMO antenna with a wide working frequency band and a wide decoupling frequency band provided by the present invention etches a long metal groove on a traditional half-mode microstrip patch antenna unit and loads a row of mushroom-shaped structure groups between the two units, realizes mutual coupling suppression at different frequency points through structural multiplexing, forms three controllable mutual coupling zero points, and obtains a planar microstrip antenna with a broadband and high decoupling level. Compared with most microstrip antenna decoupling technologies, the present invention can adapt to microstrip antennas under multi-mode broadband conditions to achieve decoupling; compared with the existing decoupling technology applicable to multi-mode antenna units, the present invention has the advantages of small overall size, high integration, low profile, etc.

[0021] 2. The present invention provides a microstrip MIMO antenna with a wide operating frequency band and a wide decoupling frequency band. The mushroom-shaped structure group placed in the center of the antenna suppresses surface wave coupling at a specific frequency band based on its high impedance characteristics, thereby realizing the first mutual coupling zero point in the microwave band. The frequency of occurrence of the mutual coupling zero point can be controlled by adjusting the horizontal size of the mushroom-shaped structure and the diameter of the central via hole.

[0022] 3. The present invention provides a microstrip MIMO antenna with a wide operating frequency band and a wide decoupling frequency band, and each half-mode microstrip patch antenna unit is etched with a long metal groove. After the groove is loaded, the frequency of a high-order mode of the unit is shifted downward, so that the bandwidth is expanded, and the two modes are superimposed in reverse phase at the coupling unit port to obtain the second mutual coupling zero point in the operating frequency band. The frequency of occurrence of the mutual coupling zero point can be controlled by adjusting the size of the long metal groove.

[0023] 4. The present invention provides a microstrip MIMO antenna with a wide operating frequency band and a wide decoupling frequency band, wherein the top radiating surface of the mushroom-shaped structure group is approximately a strip-shaped resonator, and the radiation signal of the resonator is inversely offset to the radiation signal of the microwave antenna unit, thereby realizing the third mutual coupling zero point in the frequency band, and the electrical length of the resonator along the horizontal direction can control the frequency of occurrence of the third mutual coupling zero point. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is a schematic diagram of the overall structure of the antenna of the present invention;

[0026] Figure 2 It is a schematic diagram of the structure decomposition of the antenna of the present invention;

[0027] Figure 3 is a port reflection coefficient diagram of the antenna of the present invention;

[0028] Figure 4 It is a simulation diagram of the matching level and mutual coupling level of the antenna of the present invention;

[0029] Figure 5 a is a simulation pattern of the first reflection zero point under the single-port excitation condition of the 1×2 microstrip MIMO antenna with a wide operating frequency band and a wide decoupling frequency band provided by the present invention;

[0030] Figure 5 b is a simulated radiation pattern at the second reflection zero point under single-port excitation conditions of a 1×2 microstrip MIMO antenna with a wide operating frequency band and a wide decoupling frequency band provided by the present invention.

[0031] Description of reference numerals:

[0032] 1. Top metal structure; 1-1. Metal patch; 1-2. Rectangular patch structure group; 1-3. Long strip metal slot; 2. First dielectric substrate; 2-1. Grounding metal via; 2-2. Grounding through hole; 3. Metal ground; 4. Feed probe. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0034] The present invention provides a microstrip MIMO antenna with a wide operating frequency band and a wide decoupling frequency band, wherein the structure of the 1×2 antenna array is as follows: Figure 1As shown. It is mainly composed of a top metal structure 1, a first dielectric substrate 2, a metal ground 3 and a feeding probe 4. Among them, the top metal structure 1 can be roughly divided into two parts along the horizontal direction, one part is two slot-loaded square metal patches 1-1 located on both sides, and the other part is a central grounded rectangular patch structure group 1-2 located in the middle. The two square metal patches 1-1 are each etched with a long strip of metal slot 1-3, and one side of the patch is connected to the metal ground 3 through a row of grounded metal vias 2-1, and the unit excitation is realized by the feeding probe 4 respectively, forming two half-mode microstrip patch antenna units. In the middle of the two antenna units, there are a total of eight rectangular patches, and the center of each rectangular patch has a grounding through hole 2-2 connected to the metal ground 3, forming a mushroom-like shape, so it is named a mushroom-shaped structure.

[0035] In this embodiment, the length of the rectangular patch in the mushroom-shaped structure is 0.25λ g -0.3λ g (λ g is the wavelength of the waveguide corresponding to the center frequency of the antenna), and the width is 0.08λ g -0.1λ g , the patch spacing is 0.01λ g -0.03λ g , the diameter of the center grounding via 2-2 is 0.01λ g -0.02λ g The length of the long strip metal slot 1-3 in the top metal patch 1-1 of the microstrip patch antenna unit is 0.65λ g -0.7λ g , with a width of 0.15λ g -0.2λ g , 0.28λ from the edge of the patch g -0.32λ g .

[0036] The following is a schematic diagram of an antenna design case completed based on the above working mechanism and related design guidance. The schematic diagram of the two-unit microstrip antenna structure with wide working frequency band and wide decoupling frequency band is as follows: Figure 1 The first dielectric substrate 2 used in the design case is F4B, the second dielectric substrate is R04003C, and the center distance between the two antenna units is 0.5λ 0 (λ 0 The simulation results of the matching level and mutual coupling level of the antenna proposed in the present invention are as follows: Figure 4As shown in the figure, in order to clearly demonstrate the performance improvement of the proposed antenna over the traditional antenna, the performance of the traditional 4.9GHz planar inverted F microstrip patch antenna is also shown in the figure. The center frequency of the antenna shown in this case is 4.925GHz, the 10-dB impedance matching bandwidth is 4.08%, the three mutual coupling zero points are located at 4.83GHz, 4.93GHz and 5.03GHz, and the overall mutual coupling level in the matching band is lower than -26.5dB, which is twice as wide as the bandwidth of the traditional half-mode microstrip patch antenna working at 4.9GHz, and the mutual coupling improvement in the full working band exceeds 17dB.

[0037] Figure 5 The simulated radiation pattern at the reflection zero point under the single-port excitation condition of the 1×2 microstrip MIMO antenna with wide working frequency band and wide decoupling frequency band is shown. In order to clearly show the performance improvement of the proposed antenna compared with the traditional antenna, the figure also shows the radiation pattern of the traditional half-mode microstrip two-MIMO patch antenna at the same frequency point with the same unit spacing. After applying the design method proposed in the present invention, the radiation pattern distortion problem of the two-unit half-mode microstrip patch antenna caused by the mutual coupling of the units is effectively improved, and the spatial coverage of the radiation pattern is greatly improved.

[0038] The above description is only by way of illustration of certain exemplary embodiments of the present invention. It is undoubted that those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the above drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A microstrip MIMO antenna with a wide operating frequency band and a wide decoupling frequency band, characterized in that: The invention comprises a top metal structure (1), a first dielectric substrate (2) and a metal ground (3) which are arranged in sequence from top to bottom; and a feeding probe (4) which vertically passes through the top metal structure (1), the first dielectric substrate (2) and the metal ground (3) and is connected to the top metal structure (1), the first dielectric substrate (2) and the metal ground (3).

2. The microstrip MIMO antenna with wide operating frequency band and wide decoupling frequency band according to claim 1, characterized in that: The first dielectric substrate (2) comprises two symmetrically arranged slot-loaded square metal patches (1-1), and a central grounded rectangular patch structure group (1-2) is arranged between the two metal patches (1-1).

3. The microstrip MIMO antenna with wide operating frequency band and wide decoupling frequency band according to claim 2, characterized in that: Each of the metal patches (1-1) is etched with a long strip metal groove (1-3).

4. The microstrip MIMO antenna with wide operating frequency band and wide decoupling frequency band according to claim 3, characterized in that: The two metal patches (1-1) are each connected to the metal ground (3) through a row of grounding metal vias (2-1).

5. The microstrip MIMO antenna with wide operating frequency band and wide decoupling frequency band according to claim 4, characterized in that: The two metal patches (1-1) are respectively excited by a feeding probe (4) to form two half-mode microstrip patch antenna units.

6. The microstrip MIMO antenna with wide operating frequency band and wide decoupling frequency band according to claim 2, characterized in that: The rectangular patch structure group (1-2) includes eight rectangular patches.

7. The microstrip MIMO antenna with wide operating frequency band and wide decoupling frequency band according to claim 6, characterized in that: The eight rectangular patches are respectively provided with grounding through holes (2-2) connected to the metal ground (3), forming a mushroom-like shape.

8. The microstrip MIMO antenna with wide operating frequency band and wide decoupling frequency band according to claim 7, characterized in that: The grounding through hole (2-2) is located at the center of the rectangular patch.

9. The microstrip MIMO antenna with wide operating frequency band and wide decoupling frequency band according to claim 5, characterized in that: Two square metal patches (1-1) are each etched with a long strip metal groove (1-3), one side of each patch is connected to a metal ground (3) through a row of grounding metal vias (2-1), and unit excitation is achieved by a feeding probe (4) to form two half-mode microstrip patch antenna units.

10. The microstrip MIMO antenna with wide operating frequency band and wide decoupling frequency band according to claim 7, characterized in that: The rectangular patch length in the mushroom shape is 0.25λ g -0.3λ g ,λ g is the wavelength of the waveguide corresponding to the center frequency of the antenna, and its width is 0.08λ g -0.1λ g , the patch spacing is 0.01λ g -0.03λ g , the diameter of the center grounding via (2-2) is 0.01λ g -0.02λ g ; The length of the long strip metal slot (1-3) of the top metal patch (1-1) of the microstrip patch antenna unit is 0.65λ g -0.7λ g , with a width of 0.15λ g -0.2λ g , 0.28λ from the edge of the patch g -0.32λ g .

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