A fast and accurate prediction method for near-field power flux density of array antenna

Abstract

The present invention discloses a method for quickly and accurately predicting the near-field power flow density of an array antenna, comprising the following steps: obtaining the feeding information of all units in the antenna array, the gain in each polarization direction in the far field, and the electric field phase information. According to the spatial position of the array near-field observation point, the electric field of the unit in each polarization direction at the observation point is obtained, and the electric field vectors of all units at the observation point are superimposed to obtain the total electric field at the observation point. A transformation matrix is ​​constructed according to the far-field radiation characteristics of the unit, and the magnetic field of the unit in each polarization direction at the observation point is obtained in combination with the coordinate transformation matrix. The magnetic field vectors of all units at the observation point are superimposed to obtain the total magnetic field at the observation point. The power flow density vector at the near-field observation point is obtained using the total electric field and total magnetic field at the observation point.

Description

[Technical field]

[0001] The present invention relates to the technical field of near-field calculation of array antennas, and in particular to a method for quickly and accurately predicting near-field power flow density of array antennas. [Background technology]

[0002] With the rise of wireless energy transmission, radio frequency identification and other fields, the characteristics of array antennas in the radiation near field have attracted much attention. For antennas of limited size, their field division can be divided into the inductive near field, the radiating near field (Fresnel zone) and the far field. The inductive near field is the energy storage area of ​​the antenna, and there is no energy radiation. The radial component of the electric field in the radiation near field decreases, the tangential component of the electric field tends to be in phase with the magnetic field, and some energy propagates radially. The radial component of the electric field in the far field is almost zero, only the tangential component exists, and it is in phase with the magnetic field, and the power flow density vector is radial. For array antennas, conventional methods for calculating parameters such as the electric field power flow density in the radiation near field (Fresnel zone) are complex and have a small scope of application. In fact, there is a certain area in space, which is located in the radiation near field of the entire array and in the far field radiation area of ​​each unit in the array. Therefore, we can start from the unit far field radiation characteristics to achieve a fast and accurate prediction of the electric field and power flow density vector at the position of the array radiation near field area. In summary, studying a fast and accurate prediction method for the near-field power flow density of array antennas has very strong practical significance and application value in the field of near-field computing technology of array antennas.

[0003] In the prior art:

[0004] The Chinese invention patent (CN202211689540.6) proposes an electromagnetic near-field calculation method based on the three-dimensional Taylor series. This method can well calculate the electromagnetic field of the array near field, but the method does not give the calculation result of the near-field power flow density, and the method has high calculation complexity and low engineering application value.

[0005] Ilkyu Kim et al. conducted a related study on the theoretical calculation of power densities in the near-field region of phased array antenna in 2020. They proposed a method based on the integral coupling formula of the far-field mode for the calculation of near-field power flow density. However, this method only obtains the amplitude of the power flow density, and cannot accurately give the amplitude and phase information of the power flow density vector in each direction. [Summary of the invention]

[0006] The main purpose of the present invention is to overcome the above-mentioned problems existing in the field of existing array antenna near-field calculations, and proposes a method for quickly and accurately predicting the near-field power flow density of an array antenna. This method can quickly predict the electric field, magnetic field and power flow density at the near-field observation point in the array antenna, and the results are highly consistent with the results of the electromagnetic simulation software.

[0007] A method for quickly and accurately predicting near-field power flow density of an array antenna of the present invention comprises the following steps:

[0008] Step 1: Obtain the feeding information of all units in the antenna array, the gain in each polarization direction in the far field, and the electric field phase information. The specific operation of step 1 is: obtain the feeding information of the unit, the gain in each polarization direction in the far field, and the electric field phase information through full-wave simulation, representative unit simulation, or microwave darkroom testing.

[0009] Step 2: According to the spatial position of the array near-field observation point, the electric field of each polarization direction of the unit at the observation point is obtained, and the electric field vectors of all units at the observation point are superimposed to obtain the total electric field at the observation point.

[0010] In step 2, the electric field of each polarization direction of the unit at the observation point is obtained according to the spatial position of the array near-field observation point. The electric field vectors of all units at the observation point are superimposed to obtain the total electric field at the observation point. The specific operation is as follows: First, assume that the observation point m in space is in the near-field position of the array antenna. Here, the near field specifically refers to the Fresnel zone of the array antenna. For an array antenna with N units, a global coordinate system is established with the center of the array as the origin. The local coordinate systems of all units are established with their respective centers as the origin. The coordinates of the observation point m in the local coordinate system of the nth unit are expressed as In this local coordinate system, the electric field of the nth unit at the observation point m is It is expressed as:

[0011]

[0012] in, represents the unit vector in the local coordinate system of the nth unit, They respectively represent the electric field components of each polarization direction in the local coordinate system of the nth unit.

[0013] Secondly, let the rotation matrix when the vector in the nth local coordinate system is converted to the global coordinate system be T n ; The unit vector of the global coordinate system can be expressed as In the global coordinate system, the electric field of the nth unit at the observation point m is It is expressed as:

[0014]

[0015] Among them, E m,nx ,E m,ny ,E m,nz They represent the electric field components in each polarization direction in the global coordinate system, and these electric field components can be expressed by The vector and rotation matrix T n The product of is:

[0016]

[0017] Finally, in the global coordinate system, the electric field vectors of all units at the observation point m are superimposed to obtain the total electric field at the observation point:

[0018]

[0019] Among them, E mx ,E my ,E mz is the component of the total electric field in each polarization direction at the observation point.

[0020] Step 3: Construct a transformation matrix based on the unit's far-field radiation characteristics, and combine the coordinate transformation matrix to obtain the magnetic field of the unit in each polarization direction at the observation point. The magnetic field vectors of all units at the observation point are superimposed to obtain the total magnetic field at the observation point.

[0021] In step 3, the transformation matrix is ​​constructed according to the far-field radiation characteristics of the unit, and the magnetic field of each polarization direction of the unit at the observation point is obtained by combining the coordinate transformation matrix. The magnetic field vectors of all units at the observation point are superimposed to obtain the total magnetic field at the observation point. The specific operation is:

[0022] First, the transformation matrix D and the coordinate transformation matrix A are constructed according to the unit far-field radiation characteristics. n :

[0023]

[0024] In the global coordinate system, the magnetic field of the nth unit at the observation point m is It is expressed as:

[0025]

[0026] Among them, H m,nx ,H m,ny ,H m,nz Respectively represent the electric field components of each polarization direction in the global coordinate system:

[0027]

[0028] Finally, in the global coordinate system, the magnetic field vectors of all units at the observation point m are superimposed to obtain the total magnetic field at the observation point:

[0029]

[0030] Among them, H mx ,H my ,H mz is the component of the total magnetic field in each polarization direction at the observation point.

[0031] Step 4: Use the total electric field and total magnetic field at the observation point to obtain the power flow density vector at the near-field observation point.

[0032] In step 4, the power flow density vector at the near-field observation point is obtained by using the total electric field and the total magnetic field at the observation point. The specific operation is: the power flow density vector at the observation point m can be expressed as:

[0033]

[0034] At the observation point m, consider the average power flow density within a cycle:

[0035]

[0036] The above steps can quickly and accurately predict the power flow density vector.

[0037] The advantages of the present invention are:

[0038] 1. Based on the assumption that the array near-field observation point is in the far field of each unit, the present invention establishes steps for calculating the electric field, magnetic field and power flow density applicable to the array radiation near field.

[0039] 2. The calculation method of the present invention can quickly and accurately predict the value of the near-field power flow density with short time consumption and high accuracy.

Brief Description of the Drawings

[0040] Figure 1 It is a flow chart of a method for quickly and accurately predicting near-field power flow density of an array antenna of the present invention;

[0041] Figure 2 Schematic diagram of the array antenna model structure and near-field sampling position in the simulation example of the present invention;

[0042] Figure 3 It is a comparison diagram of the amplitudes of the near-field observation surface power flow density vector calculated by the method of the present invention and the near-field observation surface power flow density vector obtained by near-field simulation using electromagnetic simulation software in various directions.

[0043] Figure 4 It is a phase comparison diagram in various directions between the near-field observation surface power flow density vector calculated by the method of the present invention and the near-field observation surface power flow density vector obtained by near-field simulation using electromagnetic simulation software. [Specific implementation method]

[0044] The present invention will now be further described with reference to the accompanying drawings.

[0045] like Figure 1 As shown, a method for quickly and accurately predicting near-field power flow density of an array antenna of the present invention comprises the following steps:

[0046] Step 1: Obtain the feeding information of all units in the antenna array, the gain in each polarization direction in the far field, and the electric field phase information. The specific operation is: obtain the unit feeding information, the gain in each polarization direction in the far field, and the electric field phase information through full-wave simulation, representative unit simulation, or microwave darkroom testing.

[0047] Step 2: According to the spatial position of the array near-field observation point, the electric field of each polarization direction of the unit at the observation point is obtained, and the electric field vectors of all units at the observation point are superimposed to obtain the total electric field at the observation point.

[0048] The specific operation of obtaining the total electric field at the observation point in step 2 is as follows: First, assume that the observation point m in space is in the near field position of the array antenna. Here, the near field specifically refers to the Fresnel zone of the array antenna. For an array antenna with N units, a global coordinate system is established with the center of the array as the origin. The local coordinate systems of all units are established with the centers of each unit as the origin. The coordinates of the observation point m in the local coordinate system of the nth unit are expressed as In this local coordinate system, the electric field of the nth unit at the observation point m is It is expressed as:

[0049]

[0050] in, represents the unit vector in the local coordinate system of the nth unit, They respectively represent the electric field components of each polarization direction in the local coordinate system of the nth unit.

[0051] Secondly, let the rotation matrix when the vector in the nth local coordinate system is converted to the global coordinate system be T n ; The unit vector of the global coordinate system can be expressed as In the global coordinate system, the electric field of the nth unit at the observation point m is It is expressed as:

[0052]

[0053] Among them, E m,nx ,E m,ny ,E m,nz They represent the electric field components in each polarization direction in the global coordinate system, and these electric field components can be expressed by The vector and rotation matrix Tn The product of is:

[0054]

[0055] Finally, in the global coordinate system, the electric field vectors of all units at the observation point m are superimposed to obtain the total electric field at the observation point:

[0056]

[0057] Among them, E mx ,E my ,E mz is the component of the total electric field in each polarization direction at the observation point.

[0058] Step 3: Construct a transformation matrix based on the unit's far-field radiation characteristics, and combine the coordinate transformation matrix to obtain the magnetic field of the unit in each polarization direction at the observation point. The magnetic field vectors of all units at the observation point are superimposed to obtain the total magnetic field at the observation point.

[0059] The total magnetic field at the observation point in step 3 is obtained by: First, construct the transformation matrix D and the coordinate transformation matrix A according to the unit far-field radiation characteristics n :

[0060]

[0061] In the global coordinate system, the magnetic field of the nth unit at the observation point m is It is expressed as:

[0062]

[0063] Among them, H m,nx ,H m,ny ,H m,nz Respectively represent the electric field components of each polarization direction in the global coordinate system:

[0064]

[0065] Finally, in the global coordinate system, the magnetic field vectors of all units at the observation point m are superimposed to obtain the total magnetic field at the observation point:

[0066]

[0067] Among them, H mx ,H my ,H mz is the component of the total magnetic field in each polarization direction at the observation point.

[0068] Step 4: Use the total electric field and total magnetic field at the observation point to obtain the power flow density vector at the near-field observation point.

[0069] The power flow density vector at the near-field observation point is obtained in step 4. The specific operation is: the power flow density vector at the observation point m can be expressed as:

[0070]

[0071] At the observation point m, consider the average power flow density within a cycle:

[0072]

[0073] The above steps can quickly and accurately predict the power flow density vector.

[0074] The method for quickly and accurately predicting the near-field power flow density of an array antenna proposed in the present invention can be further verified and illustrated through the following specific simulation examples.

[0075] Simulation example:

[0076] The array antenna simulation structure and near-field sampling position of this example are as follows Figure 2 As shown in the figure, the antenna array is a 4×4 uniform planar array, and the spacing between adjacent elements is 4 times the wavelength. Both arrays are composed of coaxially fed microstrip patch antennas, which are composed of a metal floor, a dielectric substrate, a rectangular patch, and a coaxial feed line. The dielectric substrate is Rogers 5880 (ε r =2.2), the operating frequency is 5 GHz, and λ is the operating wavelength. The aperture of the array antenna is 6λ, the center of the observation surface is located 10λ vertically above the center of the array plane, the length and width of the observation surface are the same as the array aperture, and the observation surface consists of 201*201 observation points.

[0077] like Figure 3 The figure shows the amplitude comparison diagram of the near-field observation surface power flow density vector calculated by the method of the present invention and the near-field observation surface power flow density vector obtained by near-field simulation with electromagnetic simulation software in various directions. It can be seen that the amplitude values ​​of the power flow density vector in all directions are highly consistent.

[0078] like Figure 4 Shown is a phase comparison diagram of the near-field observation surface power flow density vector calculated by the method of the present invention and the near-field observation surface power flow density vector obtained by near-field simulation with electromagnetic simulation software in various directions. It can be seen that the phase values ​​of the power flow density vector in all directions are highly consistent.

[0079] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fast and accurate prediction method for near-field power flow density of an array antenna, characterized in that: The steps include: Step 1: Obtain the feeding information of all units in the antenna array, the gain in each polarization direction of the far field, and the electric field phase information; Step 2: According to the spatial position of the array near-field observation point, the electric field of each polarization direction of the unit at the observation point is obtained, and the electric field vectors of all units at the observation point are superimposed to obtain the total electric field at the observation point; Step 3: Construct a transformation matrix based on the unit's far-field radiation characteristics, and combine the coordinate transformation matrix to obtain the magnetic field of the unit in each polarization direction at the observation point. The magnetic field vectors of all units at the observation point are superimposed to obtain the total magnetic field at the observation point. Step 4: Use the total electric field and total magnetic field at the observation point to obtain the power flow density vector at the near-field observation point; In step 2, the electric field of each polarization direction of the unit at the observation point is obtained according to the spatial position of the array near-field observation point, and the total electric field at the observation point is obtained by superposition of the electric field vectors of all units at the observation point, which can be specifically expressed as: (201) Assume that the observation point m in space is in the near field of the array antenna. Here, the near field refers specifically to the Fresnel zone of the array antenna. For an array antenna with N elements, a global coordinate system is established with the center of the array as the origin. A local coordinate system is established with the center of each element as the origin. The coordinates of the observation point m in the local coordinate system of the nth element are expressed as In this local coordinate system, the electric field of the nth unit at the observation point m is It is expressed as: in, represents the unit vector in the local coordinate system of the nth unit, They respectively represent the electric field components of each polarization direction in the local coordinate system of the nth unit, and the electric field components can be calculated from the unit feeding information, gain and electric field phase information obtained in step 1; (202) Let the rotation matrix when the vector in the nth local coordinate system is transformed into the global coordinate system be T n ; The unit vector of the global coordinate system can be expressed as In the global coordinate system, the electric field of the nth unit at the observation point m is It is expressed as: Among them, E m,nx ,E m,ny ,E m,nz Respectively represent the electric field components of each polarization direction in the global coordinate system: (203) In the global coordinate system, the electric field vectors of all units at the observation point m are superimposed to obtain the total electric field at the observation point Among them, E mx ,E my ,E mz is the component of the total electric field in each polarization direction at the observation point; In step 3, a transformation matrix is ​​constructed according to the unit far-field radiation characteristics, and the magnetic field of each polarization direction of the unit at the observation point is obtained by combining the coordinate transformation matrix. The magnetic field vectors of all units at the observation point are superimposed to obtain the total magnetic field at the observation point, which can be specifically expressed as: (301) Construct the transformation matrix D and the coordinate transformation matrix A according to the unit far-field radiation characteristics n : In the global coordinate system, the magnetic field of the nth unit at the observation point m is It is expressed as: Among them, H m,nx ,H m,ny ,H m,nz They represent the magnetic field components of each polarization direction in the global coordinate system and can be calculated by the following formula: (302) In the global coordinate system, the magnetic field vectors of all units at the observation point m are superimposed to obtain the total magnetic field at the observation point: Among them, H mx ,H my ,H mz is the component of the total magnetic field in each polarization direction at the observation point; In step 4, the power flow density vector at the near-field observation point is obtained by using the total electric field and the total magnetic field at the observation point, which can be specifically expressed as: The power flow density vector at the observation point m can be expressed as: At the observation point m, consider the average power flow density within a cycle: The above steps can quickly and accurately predict the power flow density vector.

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