CN116151038A - Analysis method of circular polarization MIMO microstrip antenna array self-decoupling technology - Google Patents

Abstract

The invention relates to an analysis method of a circular polarization MIMO microstrip antenna array self-decoupling technology, which comprises the following steps: establishing a circularly polarized MIMO microstrip antenna array to obtain modal significance and characteristic angle curves; observing the mode current and the mode electric field of four basic characteristic modes; selecting a pair of basic characteristic modes with characteristic angles different by 90 degrees and similar modal significance values as orthogonal modes; calculating a zero field region of the coupling patch unit; calculating a weak value area of the excitation patch unit; placing a feed port; and simulating the circularly polarized MIMO microstrip antenna array to obtain the excellent decoupling level of-52 dB. The invention fully adopts the characteristic mode theory as guidance in the design of the whole MIMO antenna feed point, fully exerts the advantages of the theory for multi-mode same-frequency excitation, multi-mode synthesis and the like, and has better guidance function on the design of the type of antenna; the analysis and the determination of the feed position also reduce the volume of the optimization work on the software simulation of the antenna, and have the advantages of intuitiveness and simplicity.

Description

A self-decoupling technique analysis method for circularly polarized MIMO microstrip antenna array

technical field

The invention relates to the technical field of MIMO microstrip antennas, in particular to an analysis method for circularly polarized MIMO microstrip antenna array self-decoupling technology.

Background technique

Multiple-input multiple-output MIMO technology plays a central role in the fifth-generation 5G mobile communication with its high channel capacity and fast transmission speed. However, it is worth noting that the performance of the overall system using MIMO arrays tends to be degraded due to the coupling effects of surface waves and space waves between elements. To alleviate this problem, the mutual coupling between antenna elements has been extensively studied.

With the wide application of decoupling technology, many scholars have done targeted research, among which the more classic methods include using electromagnetic bandgap structure, defect structure, decoupling network method, neutral line decoupling, metamaterial structure decoupling, etc. Such methods require additional decoupling devices for the antenna or require special processing of the antenna itself. Correspondingly, the cost is relatively high, the processing is relatively difficult, and the structure is relatively complicated. Self-decoupling, as a technology that does not require an additional decoupling network and only relies on the characteristics of the antenna itself to achieve the decoupling effect without damaging its own radiation performance, has also attracted widespread attention in recent years. Many schemes have been proposed, such as the use of eigenmode The theory optimizes the excitation position to obtain a specific weak field. It also uses the theory of common and differential modes to cancel each other out and synthesize weak fields. It also uses the theory of eigenmodes to analyze and excite higher-order modes to achieve decoupling effects by dispersing energy. However, many analyzes do not have clear guidance on the position of the feed. The optimal feed position is determined based on a large number of structural optimizations. The eigenmode theory only exists in the mode analysis, or it is used in an abstract manner and is not specific enough.

Contents of the invention

In order to solve the impact of additional decoupling structure on the performance of the antenna and the defect that the feeding position needs to be determined through a large number of optimizations in the self-decoupling technology, the purpose of the present invention is to provide a method that can be analyzed and obtained under the condition of no feeding The feed position with good decoupling performance simplifies the simulation optimization process, has a clear theoretical basis, and is conducive to guiding the analysis method of circularly polarized MIMO microstrip antenna array self-decoupling technology for the same type of self-decoupling antenna design.

In order to achieve the above object, the present invention adopts the following technical scheme: a kind of analytical method of circularly polarized MIMO microstrip antenna array self-decoupling technology, the method comprises the steps of following order:

(1) Establish a circularly polarized MIMO microstrip antenna array including coupled patch units and excitation patch units, and analyze the circularly polarized MIMO microstrip antenna array based on the characteristic mode theory, and obtain the mode significance and characteristic angle curve;

(2) According to the modal significance and the resonance characteristics reflected by the characteristic angle curve, determine the four basic characteristic modes of the circularly polarized MIMO microstrip antenna array, and observe the mode current and mode electric field of the four basic characteristic modes;

(3) Among the four basic eigenmodes, a pair of basic eigenmodes with a difference of 90 degrees in characteristic angles and similar modal significance values are selected as orthogonal modes at the 5.5 GHz frequency point;

(4) Based on the requirements of decoupling, calculate the mode electric field sum of the zero field region of the orthogonal mode on the coupling patch unit of the circularly polarized MIMO microstrip antenna array;

(5) Based on the requirement of simultaneous excitation of the orthogonal mode, calculate the weak value area of the mode current difference of the orthogonal mode on the excitation patch unit of the circularly polarized MIMO microstrip antenna array;

(6) The geometric common area between the zero field area of the coupling patch unit and the weak value area of the excitation patch unit is used as the feeding position selection area, and the feeding port is placed;

(7) After determining the position of the feed port, the circularly polarized MIMO microstrip antenna array is simulated, and an excellent decoupling level of -52dB is obtained.

The step (1) specifically refers to: establishing a circularly polarized MIMO microstrip antenna array, the array is composed of two identical rectangular microstrip antennas, and the two rectangular microstrip antennas are respectively used as an excitation patch unit and a coupling patch unit , the length of the rectangular microstrip antenna is 14.93mm, the width is 16.3mm, and the distance is 6.71mm. Two rectangular microstrip antennas are printed side by side on a single-layer dielectric substrate with a thickness of 1.50mm and a dielectric constant of 2.65;

Based on the method of moments and the electric field integral equation, the weighted characteristic equation is derived as follows:

；

;

Among them, R and X represent the real and imaginary parts of the impedance matrix obtained from the relationship between the electric field and the surface current, J _n represents the characteristic current, and λ _n is the corresponding eigenvalue. After integral calculation, the modal significance is defined as :

；

;

Therefore, the modal significance MS is related to the eigenvalue λ _n . When λ _n <0, it is called capacitive mode; when λ _n > 0, it is called inductive mode; when λ _n =0, it is called resonant mode;

When the modal significance MS value is equal to 1, it means that this mode has the most complete radiation. Using CST Studio Suite software, the characteristic mode analysis of the antenna array without excitation is carried out, and the modal significance curve and characteristic angle curve are obtained through simulation.

The step (2) specifically refers to: after the eigenmode analysis, according to the definition of modal significance, the closer the amplitude is to 1, the greater the potential for the mode to be excited. There are four in the 5.2 to 5.8GHz frequency band The patterns showed a high level of significance, and they were named as the first basic characteristic pattern, the second basic characteristic pattern, the third basic characteristic pattern and the fourth basic characteristic pattern.

The step (3) specifically refers to: the definition of the characteristic angle is:

；

;

In the formula, λ _n is the eigenvalue, when β<180°, the eigenmode corresponding to the eigenvalue can store magnetic energy; when β>180°, the eigenmode corresponding to the eigenvalue can store electric energy; when β= At 180°, the eigenmode corresponding to the eigenvalue is in a resonance state;

In order to realize the circularly polarized radiation of the antenna, modes with a phase difference of 90° and the same amplitude are required as orthogonal modes to synthesize the radiation field. At nearly 5.5 GHz, the modes of the first fundamental eigenmode and the fourth fundamental eigenmode are significantly The characteristics are the same, which means that at this frequency point, the first basic eigenmode and the fourth basic eigenmode can produce radiation effects with similar amplitudes under appropriate excitation; at the same time, the first basic eigenmode and the fourth basic eigenmode The characteristic angle difference at the point is 90°, indicating that the two modes are orthogonal to each other, so the first basic characteristic mode and the fourth basic characteristic mode are selected as the orthogonal modes.

The step (4) specifically refers to: after selecting the orthogonal mode, use the field calculator in the CST Studio Suite software to add the electric field of the orthogonal mode to generate on both the excitation patch unit and the coupling patch unit Synthetic zero field area, in order to minimize the coupling effect, when the feed port is installed on the excitation patch unit, the feed port on the coupling patch unit needs to be located in the zero field area of the synthetic field, select the coupling patch unit The region where the upper electric field value is zero, that is, the zero field region, is used as a candidate region for the excitation port.

The step (5) specifically refers to: after selecting the orthogonal mode, use the field calculator in the CST Studio Suite software to subtract the orthogonal mode current, and there is a weak value area near the four corners of the rectangle, which represents The current distribution of the two modes of the orthogonal mode is similar here. If the feed port is installed here, the radiation response of the two modes to the excitation is similar, that is, the two modes are excited to a similar degree, and the current on the excitation patch unit is selected. The weak value area of is used as the candidate area for the excitation port.

The step (6) specifically refers to: After obtaining two candidate areas for decoupling and simultaneous excitation, since the excitation patch unit and the coupling patch unit have the same shape, the zero field of the coupling patch unit In the geometric intersection area corresponding to the area and the weak value area of the excitation patch unit, the feed port is placed as the desired feed position selection area.

The step (7) specifically refers to: use all the coordinates of the feeding position selection area as the coaxial feeding coordinates to use the HFSS simulation software to simulate the circularly polarized MIMO microstrip antenna array and obtain the electromagnetic performance, select the radiation, structure, The position where the circular polarization and decoupling effects are the best, the best decoupling effect reaches -52dB at 5.45GHz, and has very good circular polarization and self-decoupling performance.

It can be seen from the above technical solution that the beneficial effects of the present invention are as follows: First, the present invention is different from other self-decoupling antenna design methods, starting from the structure and electromagnetic properties of the antenna, fully adopting the feature Mode theory is used as a guide, giving full play to the advantages of this theory for multi-mode same-frequency excitation, multi-mode synthesis, etc., explaining the reasons for circular polarization and decoupling effects in principle, and has a good advantage in the design of this type of antenna second, the analysis and determination of the feeding position also reduces the volume of optimization work in the software simulation of the antenna, which has the advantage of being intuitive and simple; The self-decoupling mode of the weak field has an important guiding role, and can be extended to the analysis of more complex structures in the future; fourth, the radiation category that the present invention can be used to analyze antennas can not only be limited to circular polarization, but also to linear polarization, MIMO antennas such as dual polarization are applicable, and the analysis cost is relatively low.

Description of drawings

Fig. 1 is method flowchart of the present invention;

Fig. 2 is the front view of circularly polarized MIMO microstrip antenna array in the present invention;

Fig. 3 is the top view of circularly polarized MIMO microstrip antenna array in the present invention;

Fig. 4 is the modal significance curve figure of the present invention;

Fig. 5 is a characteristic angle graph of the present invention;

Fig. 6 is the electric field distribution diagram of the basic mode of the present invention;

Fig. 7 is the basic mode current distribution diagram of the present invention;

Fig. 8 is the electric field and distribution diagram of the orthogonal mode of the present invention;

Fig. 9 is a distribution diagram of the current difference in the orthogonal mode of the present invention;

Fig. 10 is a schematic diagram of axial ratio and S11, S21 parameter curves of the present invention;

Fig. 11 is the circular polarization pattern of the xoz plane of the present invention at 5.54 GHz;

Fig. 12 is the circular polarization pattern of the yoz plane at 5.54 GHz according to the present invention.

Detailed ways

As shown in Figure 1, a kind of analysis method of self-decoupling technology of circularly polarized MIMO microstrip antenna array, this method comprises the steps of following order:

(1) Establish a circularly polarized MIMO microstrip antenna array including coupling patch unit 2 and excitation patch unit 1, and analyze the circularly polarized MIMO microstrip antenna array based on the eigenmode theory, and obtain the modal significance and characteristic angle curve;

(2) According to the modal significance and the resonance characteristics reflected by the characteristic angle curve, determine the four basic characteristic modes of the circularly polarized MIMO microstrip antenna array, and observe the mode current and mode electric field of the four basic characteristic modes;

(3) Among the four basic eigenmodes, a pair of basic eigenmodes with a difference of 90 degrees in characteristic angles and similar modal significance values are selected as orthogonal modes at the 5.5 GHz frequency point;

(4) Based on the requirement of decoupling, calculate the zero field area of the mode electric field sum of the orthogonal mode on the coupled patch unit 2 of the circularly polarized MIMO microstrip antenna array;

(5) Based on the requirement of simultaneous excitation of the orthogonal mode, calculate the weak value area of the mode current difference of the orthogonal mode on the excitation patch unit 1 of the circularly polarized MIMO microstrip antenna array;

(6) The geometric common area between the zero field area of the coupling patch unit 2 and the weak value area of the excitation patch unit 1 is used as the feeding position selection area, and the feeding port 3 is placed;

(7) After determining the position of the feeding port 3, the circularly polarized MIMO microstrip antenna array is simulated, and an excellent decoupling level of -52dB is obtained.

The step (1) specifically refers to: first establish a circularly polarized MIMO microstrip antenna array as shown in Figures 2 and 3, and set the spatial rectangular coordinate system o-xyz to include: origin o, x-axis, y-axis, and z-axis ; The MIMO array is parallel to the xoy plane of the spatial Cartesian coordinate system. A circularly polarized MIMO microstrip antenna array is established. The array is composed of two identical rectangular microstrip antennas. The two rectangular microstrip antennas are respectively used as the excitation patch unit 1 and the coupling patch unit 2. The length of the rectangular microstrip antenna is 14.93mm, 16.3mm wide, and 6.71mm apart, two rectangular microstrip antennas are printed side by side on a single-layer dielectric substrate with a thickness of 1.50mm and a dielectric constant of 2.65;

Eigenmode theory is a mathematical method for analyzing and designing antenna systems. The theory is based on the vector potential theory of electromagnetic fields. It can be used to predict the radiation and impedance characteristics of antenna systems, and to optimize antenna performance by adjusting geometric shapes. As an important indicator of eigenmode theory, modal salience refers to the contribution of each eigenmode (also called fundamental mode) in the antenna structure to the total electromagnetic field. During the simulation process, it can be adjusted by changing the geometry of the antenna. The weight of each eigenmode to optimize the performance of the antenna, such as increasing radiation efficiency, reducing VSWR, etc.

Based on the method of moments and the electric field integral equation, the weighted characteristic equation is derived as follows:

；

;

Among them, R and X represent the real and imaginary parts of the impedance matrix obtained from the relationship between the electric field and the surface current, J _n represents the characteristic current, and λ _n is the corresponding eigenvalue. After integral calculation, the modal significance is defined as :

；

;

Therefore, the modal significance MS is related to the eigenvalue λ _n . When λ _n <0, it is called capacitive mode; when λ _n > 0, it is called inductive mode; when λ _n =0, it is called resonant mode; When guiding antenna design, favor the resonant modes of the antenna and suppress the inductive and capacitive modes as much as possible. When the modal significance MS value is equal to 1, it means that this mode has the most complete radiation. Using CSTStudio Suite software, the characteristic mode analysis of the antenna array without excitation is carried out, and the modal significance curve and characteristic angle curve are obtained through simulation.

The step (2) specifically refers to: after the eigenmode analysis, according to the definition of modal significance, the closer the amplitude is to 1, the greater the potential for the mode to be excited. There are four in the 5.2 to 5.8GHz frequency band The patterns showed a high level of significance, and they were named as the first basic characteristic pattern, the second basic characteristic pattern, the third basic characteristic pattern and the fourth basic characteristic pattern. After eigenmode analysis, the modal significance MS curve shown in Figure 4 and the characteristic angle curve shown in Figure 5 can be obtained. According to the curves, the values at frequencies of 5.25GHz, 5.31 GHz, 5.68 GHz, and 5.71 GHz can be obtained is close to 1, so the four modes determine the base mode. The mode electric fields and mode currents of the four modes are shown in Fig. 6 and Fig. 7 respectively.

The step (3) specifically refers to: the definition of the characteristic angle is:

；

;

In the formula, λ _n is the eigenvalue, when β<180°, the eigenmode corresponding to the eigenvalue can store magnetic energy; when β>180°, the eigenmode corresponding to the eigenvalue can store electric energy; when β= At 180°, the eigenmode corresponding to the eigenvalue is in a resonance state;

In order to realize the circularly polarized radiation of the antenna, modes with a phase difference of 90° and the same amplitude are required as orthogonal modes to synthesize the radiation field. At nearly 5.5 GHz, the modes of the first fundamental eigenmode and the fourth fundamental eigenmode are significantly The characteristics are the same, which means that at this frequency point, the first basic eigenmode and the fourth basic eigenmode can produce radiation effects with similar amplitudes under appropriate excitation; at the same time, the first basic eigenmode and the fourth basic eigenmode The characteristic angle difference at the point is 90°, indicating that the two modes are orthogonal to each other, so the first basic characteristic mode and the fourth basic characteristic mode are selected as the orthogonal modes.

The step (4) specifically refers to: after selecting the orthogonal mode, use the field calculator in the CST Studio Suite software to add the electric field of the orthogonal mode to the excitation patch unit 1 and the coupling patch unit 2 Both generate a synthetic zero-field area. In order to minimize the coupling effect, when the feed port 3 is installed on the excitation patch unit 1, the feed port 3 on the coupling patch unit 2 needs to be located in the zero-field area of the synthetic field. , select the region where the electric field value on the coupling patch unit 2 is zero, that is, the zero field region, as the candidate region for the excitation port.

The step (5) specifically refers to: after selecting the orthogonal mode, use the field calculator in the CST Studio Suite software to subtract the orthogonal mode current, and there is a weak value area near the four corners of the rectangle, which represents The current distribution of the two modes of the orthogonal mode is similar here. If the feed port 3 is installed here, the radiation response of the two modes to the excitation is similar, that is, the two modes are excited to a similar degree, and the excitation patch unit 1 is selected. The weak value region of the upper current is used as an alternative region for the excitation port.

The step (6) specifically refers to: After obtaining two candidate regions for decoupling and simultaneous excitation, since the excitation patch unit 1 and the coupling patch unit 2 have the same shape, the coupling patch unit 2 In the geometric intersection area corresponding to the zero field area and the weak value area of the excitation patch unit 1 as the desired feeding position selection area, the feeding port 3 is placed.

The step (7) specifically refers to: use all the coordinates of the feeding position selection area as the coaxial feeding coordinates to use the HFSS simulation software to simulate the circularly polarized MIMO microstrip antenna array and obtain the electromagnetic performance, select the radiation, structure, The position where the circular polarization and decoupling effects are the best, the best decoupling effect reaches -52dB at 5.45GHz, and has very good circular polarization and self-decoupling performance.

Add the electric fields of the first fundamental eigenmode and the fourth fundamental eigenmode in the orthogonal mode, and its electric field distribution is shown in Figure 8. On the coupling patch unit 2, a stable weak field with an electric field value of zero is selected. The area, ie the dotted line area, represents that the combined electric fields cancel each other, and there is no influence of the electric field effect, which is used as an alternative area for the feeding position on the coupling patch unit 2 .

The current of the first basic eigenmode and the fourth basic eigenmode in the orthogonal mode is subtracted, and the current distribution is shown in Figure 9. On the excitation patch unit 1, a weak value area with a current value of zero is selected, That is, the dotted line area represents that the currents of the two modes in this place are similar. If the excitation is performed here, the first basic eigenmode and the fourth basic eigenmode can be excited to a similar degree at the same time, as the excitation of the feeding position on the patch unit 1. Alternative area.

According to the obtained feed position, the coaxial mode feed is set, and the simulation software is used for simulation, and a better decoupling effect can be obtained. Under the premise of no feed setting, according to the eigenmode theory, the circularly polarized radiation is excited in the excitation patch unit 1, and at the same time, the feed point is located in the stable weak field area of the coupling patch unit 2, so as to realize the effect of reducing the coupling by itself . After simulation, Figure 10 shows the axial ratio, S ₁₁ , S ₂₁ , and parameter curves of the antenna, Figure 11 shows the polarization pattern of the xoz plane when the antenna is at 5.54GHz, and Figure 12 shows the yoz plane when the antenna is at 5.54GHz The polarization pattern of . S ₁₁ refers to the reflection coefficient and S ₂ refers to the transmission coefficient.

Use all the coordinates of the feeding position selection area as the coaxial feeding coordinates to use the HFSS simulation software to simulate the antenna array and obtain the electromagnetic performance, select the position with the best radiation, structure, circular polarization and decoupling effect, and its parameters are shown in the figure 10. _The impedance bandwidth (S ₁₁ <-10dB) can _reach 6.80% (5.26-5.63GHz), and the decoupling bandwidth ( S ₂₁ <-20dB) reaches 1.83% (5.40-5.50GHz), circular polarization bandwidth (AR<3dB) reaches 2.0% (5.41-5.52GHz), and the best decoupling effect can reach -52dB at 5.45GHz, so It has good circular polarization and self-decoupling performance. Under the premise of no feed setting and software optimization, according to the eigenmode theory, analyze the optimal feed position in the excitation patch unit 1 and at the same time excite the orthogonal mode to excite circularly polarized radiation, and the position of the feed point is also located at In the stable weak field area of the coupling patch unit 2, the synthesized weak field has little influence on the excitation port, and the modes cancel each other to achieve the effect of reducing the coupling by itself, which provides important information for the design of this type of self-decoupling antenna. theoretical guidance.

To sum up, the present invention is different from other self-decoupling antenna design methods. Starting from the structure and electromagnetic properties of the antenna, the eigenmode theory is completely used as a guide in the design of the feeding point of the entire MIMO antenna, and the theory is fully utilized. Based on the advantages of multi-mode same-frequency excitation and multi-mode synthesis, it explains the reasons for circular polarization and decoupling effects in principle, and has a good guiding role in the design of this type of antenna; the analysis and determination of the feed position It also reduces the volume of optimization work in the software simulation of the antenna, which has the advantage of being intuitive and simple.

Claims (8)

1. an analytical method of circularly polarized MIMO microstrip antenna array self-decoupling technology, is characterized in that: the method comprises the steps of following order: (1) Establish a circularly polarized MIMO microstrip antenna array including coupled patch units and excitation patch units, and analyze the circularly polarized MIMO microstrip antenna array based on the characteristic mode theory, and obtain the mode significance and characteristic angle curve; (2) According to the modal significance and the resonance characteristics reflected by the characteristic angle curve, determine the four basic characteristic modes of the circularly polarized MIMO microstrip antenna array, and observe the mode current and mode electric field of the four basic characteristic modes; (3) Among the four basic eigenmodes, a pair of basic eigenmodes with a difference of 90 degrees in characteristic angles and similar modal significance values are selected as orthogonal modes at the 5.5 GHz frequency point; (4) Based on the requirements of decoupling, calculate the mode electric field sum of the zero field region of the orthogonal mode on the coupling patch unit of the circularly polarized MIMO microstrip antenna array; (5) Based on the requirement of simultaneous excitation of the orthogonal mode, calculate the weak value area of the mode current difference of the orthogonal mode on the excitation patch unit of the circularly polarized MIMO microstrip antenna array; (6) The geometric common area between the zero field area of the coupling patch unit and the weak value area of the excitation patch unit is used as the feeding position selection area, and the feeding port is placed; (7) After determining the position of the feed port, the circularly polarized MIMO microstrip antenna array is simulated, and an excellent decoupling level of -52dB is obtained. 2. The analysis method of circularly polarized MIMO microstrip antenna array self-decoupling technology according to claim 1, characterized in that: said step (1) specifically refers to: establishing a circularly polarized MIMO microstrip antenna array, the The array is composed of two identical rectangular microstrip antennas. The two rectangular microstrip antennas are respectively used as the excitation patch unit and the coupling patch unit. The length of the rectangular microstrip antenna is 14.93mm, the width is 16.3mm, and the distance is 6.71mm. Two rectangular microstrip antennas are printed side by side on a single-layer dielectric substrate with a thickness of 1.50mm and a dielectric constant of 2.65; Based on the method of moments and the electric field integral equation, the weighted characteristic equation is derived as follows:

; Among them, R and X represent the real and imaginary parts of the impedance matrix obtained from the relationship between the electric field and the surface current, J _n represents the characteristic current, and λ _n is the corresponding eigenvalue. After integral calculation, the modal significance is defined as :

; Therefore, the modal significance MS is related to the eigenvalue λ _n . When λ _n <0, it is called capacitive mode; when λ _n > 0, it is called inductive mode; when λ _n =0, it is called resonant mode; When the modal significance MS value is equal to 1, it means that this mode has the most complete radiation. Using CST Studio Suite software, the characteristic mode analysis of the antenna array without excitation is carried out, and the modal significance curve and characteristic angle curve are obtained through simulation. 3. The analysis method of circularly polarized MIMO microstrip antenna array self-decoupling technology according to claim 1, characterized in that: said step (2) specifically refers to: after eigenmode analysis, according to the modal significance The definition of , the closer the amplitude is to 1, the greater the potential of the mode to be excited. In the 5.2 to 5.8GHz frequency band, there are four modes that show a high level of significance, and they are respectively named as the first basic characteristic mode and the second basic characteristic mode. A feature pattern, a third base feature pattern, and a fourth base feature pattern. 4. The analysis method of circularly polarized MIMO microstrip antenna array self-decoupling technology according to claim 1, characterized in that: said step (3) specifically refers to: the definition of said characteristic angle is:

; In the formula, λ _n is the eigenvalue, when β<180°, the eigenmode corresponding to the eigenvalue can store magnetic energy; when β>180°, the eigenmode corresponding to the eigenvalue can store electric energy; when β= At 180°, the eigenmode corresponding to the eigenvalue is in a resonance state; In order to realize the circularly polarized radiation of the antenna, modes with a phase difference of 90° and the same amplitude are required as orthogonal modes to synthesize the radiation field. At nearly 5.5 GHz, the modes of the first fundamental eigenmode and the fourth fundamental eigenmode are significantly The characteristics are the same, which means that at this frequency point, the first basic eigenmode and the fourth basic eigenmode can produce radiation effects with similar amplitudes under appropriate excitation; at the same time, the first basic eigenmode and the fourth basic eigenmode The characteristic angle difference at the point is 90°, indicating that the two modes are orthogonal to each other, so the first basic characteristic mode and the fourth basic characteristic mode are selected as the orthogonal modes. 5. The analysis method of circularly polarized MIMO microstrip antenna array self-decoupling technology according to claim 1, characterized in that: said step (4) specifically refers to: after selecting the orthogonal mode, use CST Studio Suite software In the field calculator in , the orthogonal mode electric fields are summed to generate a synthetic zero field region on both the excitation patch unit and the coupling patch unit. In order to minimize the coupling effect, install When feeding the port, the feeding port on the coupling patch unit needs to be located in the zero field area of the synthetic field, and the area where the electric field value on the coupling patch unit is zero, that is, the zero field area, is selected as an alternative area for the excitation port. 6. The analysis method of circularly polarized MIMO microstrip antenna array self-decoupling technology according to claim 1, characterized in that: said step (5) specifically refers to: after selecting the orthogonal mode, use CST Studio Suite software In the field calculator in , the orthogonal mode current is subtracted, and there is a weak value area near the four corners of the rectangle. This area represents the similar distribution of the two mode currents in the orthogonal mode. If the feeder is installed here Port, the radiation response of the two modes to the excitation is similar, that is, the two modes are excited to a similar degree, and the weak value area of the excitation current on the patch unit is selected as the candidate area for the excitation port. 7. The analysis method of circularly polarized MIMO microstrip antenna array self-decoupling technology according to claim 1, characterized in that: the step (6) specifically refers to: after obtaining the decoupling and simultaneous excitation respectively After the two candidate areas, since the excitation patch unit and the coupling patch unit have the same shape, the geometric intersection area corresponding to the zero field area of the coupling patch unit and the weak value area of the excitation patch unit is used as the expected feed Position selection area, place the feed port. 8. The analysis method of circularly polarized MIMO microstrip antenna array self-decoupling technology according to claim 1, characterized in that: the step (7) specifically refers to: taking all the coordinates of the feeding position selection area as the same The axial feed coordinates use HFSS simulation software to simulate the circularly polarized MIMO microstrip antenna array and obtain the electromagnetic performance, select the position with the best radiation, structure, circular polarization and decoupling effect, and the best decoupling effect is at 5.45GHz Reach -52dB, with good performance of circular polarization and self-decoupling.

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