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CN112904095A - Array antenna near field calibration system and method - Google Patents

Array antenna near field calibration system and method Download PDF

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CN112904095A
CN112904095A CN202110160102.XA CN202110160102A CN112904095A CN 112904095 A CN112904095 A CN 112904095A CN 202110160102 A CN202110160102 A CN 202110160102A CN 112904095 A CN112904095 A CN 112904095A
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array antenna
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plane wave
antenna
wave generator
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陈晓明
陈瑞海
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Xian Jiaotong University
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Abstract

一种阵列天线近场校准系统及方法，包括待测阵列天线，所述阵列天线一共有N个天线单元，每个天线单元配备一个数字移相器进行相位控制，位于在待测阵列天线的近场放置有平面波生成器，所述平面波生成器用于在待测阵列天线处产生准平面波，所述阵列天线的各通道连接矢量网络分析仪一端，矢量网络分析仪一端另一端连接平面波生成器。本发明通过平面波生成器在待测天线近场产生准平面波，较远场测试方法显著减小测试所需微波暗室的大小，避免了电磁波传播距离较长造成的路径损耗引起的误差，将平面波生成器看作等效的远场单探头测量系统，具有测量耗时短、占用空间小、成本低廉的特点。

Figure 202110160102

A near-field calibration system and method for an array antenna, including an array antenna to be tested, the array antenna has a total of N antenna units, each antenna unit is equipped with a digital phase shifter for phase control, and is located near the array antenna to be tested. A plane wave generator is placed in the field. The plane wave generator is used to generate quasi-plane waves at the array antenna to be tested. Each channel of the array antenna is connected to one end of the vector network analyzer, and the other end of the vector network analyzer is connected to the plane wave generator. The invention generates a quasi-plane wave in the near field of the antenna to be tested by the plane wave generator, and the far-field test method significantly reduces the size of the microwave anechoic chamber required for the test, avoids the error caused by the path loss caused by the long propagation distance of the electromagnetic wave, and generates the plane wave. It is regarded as an equivalent far-field single-probe measurement system, which has the characteristics of short measurement time, small footprint and low cost.

Figure 202110160102

Description

Array antenna near field calibration system and method
Technical Field
The invention relates to the technical field of millimeter wave measurement, in particular to an array antenna near field calibration system and method.
Background
With the rapid development of 5G mobile communication technology in recent years, large-scale antenna array technology has gained more and more attention as one of the key technologies. Meanwhile, the array antenna is provided with a plurality of electronic elements with parameters changing with the use time and the temperature, so that amplitude and phase errors among the array antenna units are caused, and the consistency among channels is greatly influenced. Therefore, before the array antenna is used, the radiation phase error between the array antenna units needs to be obtained and compensated through an array antenna channel calibration method so as to ensure the normal operation of the array antenna. Many methods have been proposed for antenna calibration, and can be roughly classified into two categories: a near-field calibration system and a far-field calibration system. The far field single probe test method has a simple system structure, but the probe needs to be ensured to be placed in the far field of the array antenna to be tested. For 5G frequency band application, a microwave dark room capable of meeting the above conditions is expensive in manufacturing cost, and far field measurement also brings large propagation loss to reduce the dynamic range. The near-field single-probe testing method greatly reduces the requirement on the size of a microwave darkroom, but needs to control the position of the probe accurately to enable the probe to be aligned with each array antenna unit to be tested in sequence, and the probe antenna needs to move on a plane with higher precision requirement, so that the measuring time is long, and the high-precision scanning system is expensive in manufacturing cost.
Disclosure of Invention
In order to overcome the technical problems, the invention aims to provide an array antenna near-field calibration system and method, a plane wave generator generates a quasi-plane wave in a near field of an antenna to be tested, the size of a microwave darkroom required by testing is obviously reduced, errors caused by path loss due to long propagation distance of electromagnetic waves are avoided, the plane wave generator is regarded as an equivalent far-field single-probe measurement system, and the system and method have the characteristics of short measurement time consumption, small occupied space and low cost.
In order to achieve the purpose, the invention adopts the technical scheme that:
a near field calibration system of an array antenna is characterized in that the array antenna to be tested is provided with N antenna units, each antenna unit is provided with a digital phase shifter for phase control, a plane wave generator is arranged in the near field of the array antenna to be tested and used for generating quasi-plane waves at the array antenna to be tested, ports of all antenna units of the array antenna to be tested are connected with a port 1 of a vector network analyzer, and a port 2 of the vector network analyzer is connected with the plane wave generator.
The vector network analyzer is used for measuring S parameters between the array antenna to be measured and the plane wave generator, and the power supply is used for supplying power to the array antenna to be measured to enable the array antenna to be measured to work in a transmitting state.
The array antenna to be measured changes the phase shift of the N antenna units before each measurement, so that the array antenna to be measured is in M different phase states known in advance.
A test method of an array antenna near field calibration system comprises the following steps;
step 1: designing M different phase states to be configured, and solving a linear equation set established according to a relation of receiving and transmitting signals to obtain initial excitation information in a calibration process (step 2-5), so that a phase state matrix PM×NNeeds to be as small as possible to reduce the influence of possible errors on the measurement result, so that a recursive method is used to generate a phase matrix P with the smallest possible condition number from a base matrix with known condition numbersM×N；
Step 2: adjusting the array antenna to be tested into a transmitting mode, adjusting the plane wave generator into a receiving mode, and simultaneously ensuring that a quiet area generated by the plane wave generator contains the space of the antenna to be tested;
and step 3: acquisition of scattering parameters S using a vector network analyzerN×1；
And 4, step 4: adjusting the phase shift of the array antenna unit to be measured for M times, measuring and recording the signal M received by the plane wave generatorM×1；
And 5: solving an equation set according to the known data to obtain a measurement result;
signal relationship according to a system of linear equations:
Figure BDA0002936188900000031
wherein P isM×NIn order to pre-set the phase state matrix,
Figure BDA0002936188900000032
hadamard product, a, representing a matrixN×1Representing the initial excitation, S, of the array antenna under testN×1For the measured scattering parameter, MM×1The measurement result at the plane wave generator end is obtained by using a known number of P, a and S, and obtaining X as P by matrix pseudo-inversion-1Comparing M with known a DEG S to obtain the medium array of the radio frequency linkThe radiation disparity between the column antenna elements.
In the step 1, M different phase states required to be configured are designed, and in order to ensure that the measurement has low sensitivity to errors, a recursive method is adopted to generate a phase matrix P with a condition number as small as possible from a base matrix with a known condition numberM×N。
The invention has the beneficial effects that:
1. compared with the existing single-probe far-field calibration measurement technology, the array antenna near-field calibration measurement system provided by the invention obviously reduces the requirement on the size of a microwave darkroom, can complete all measurement work in a near field, and greatly reduces the related cost of microwave darkroom construction.
2. Compared with the existing single-probe near-field calibration measurement technology, the array antenna near-field calibration measurement system avoids the use of a high-precision probe position control device and a high-flatness plane frame, reduces the related cost and shortens the time consumed by calibration.
3. The array antenna near-field calibration and measurement system disclosed by the invention enables near-field measurement to be equivalent to far-field measurement, and retains the characteristics of simple and efficient data processing work in a far-field single-probe calibration and measurement technology.
Drawings
Fig. 1 is a schematic diagram of an array antenna near field calibration measurement system.
Fig. 2 is a schematic signal relationship diagram of the array antenna near field calibration measurement system.
Fig. 3 is a schematic diagram of the excitation results obtained by the distortion excitation (the distortion of the rf link is known) and the calibration solution of the quad-array antenna according to the embodiment of the present invention.
FIG. 4 is a graphical illustration of the error level of the calibration excitation compared to the distorted excitation for a quad-array antenna in an embodiment of the invention.
Fig. 5 is a comparison of antenna patterns before and after calibration of a quaternary array antenna in an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
As shown in fig. 1 and 2, the array antenna near field calibration system of the present invention includes: the device comprises an array antenna to be tested, a plane wave generator, a vector network analyzer, a matched power supply and the like. The relative distance between the array antenna to be tested and the plane wave generator needs to enable the array antenna to be tested to be located in a quiet area of the plane wave generator.
During measurement, the array antenna to be measured works in a transmitting state, and the plane wave generator works in a receiving state. The array antenna has N antenna units, each antenna unit is connected with a digital phase shifter and an attenuator to perform phase shift and initial excitation setting, and the phase shift of the N antenna units is changed simultaneously before each measurement, so that the system is under M different phase shift settings.
The signal relationship in fig. 1 can be expressed as:
Figure BDA0002936188900000051
wherein the matrix P ∈ CM×NThe vector a ∈ CN×1,
Figure BDA0002936188900000052
S∈CN×1,M∈CN×1And a is the initial excitation,
Figure BDA0002936188900000053
the excitation distortion caused by the radio frequency link inconsistency, and a, P are preset known parameters, S, M can be obtained by measurement.
Figure BDA0002936188900000054
I.e. the amplitude-phase distortion of the radio frequency link that is desired to be solved by the calibration process.
Can be obtained by the formula (1),
Figure BDA0002936188900000055
solving equation (2) to obtain the amplitude-phase distortion of the radio frequency link
Figure BDA0002936188900000056
And then calibrating the array antenna to be tested.
It should be noted that, the solution (2) is obtained by the pair
Figure BDA0002936188900000057
The accuracy of the solution is related to the condition number of the phase shift matrix P, and if the condition number of the matrix P is too large, the small disturbance can cause large change of the solution result. Therefore, in order to ensure the accuracy of the calibration of the array antenna, the P matrix with a smaller condition number needs to be selected for solving. The method for constructing the P matrix with smaller condition number used in the invention comprises the following steps: and circularly constructing from the given basic matrix by a recursive circular method. The known fundamental matrix P2,P3,P5:
Figure BDA0002936188900000058
Figure BDA0002936188900000059
Figure BDA00029361889000000510
If a quaternary array is required, i.e. two P' s2And (3) constructing a matrix cycle to obtain a phase matrix P:
Figure BDA0002936188900000061
for the same reason of array antennas with other sizes, if the corresponding element matrix cannot be constructed circularly, a slightly larger circular phase matrix can be used, and the excitation of the corresponding antenna unit is made to be zero.
In the embodiment of the invention, the quaternary array antenna is selected, the corresponding phase matrix is P, amplitude and phase errors possibly introduced by the phase shifter are considered, and the amplitude error of 1dB at most and the phase error of 3 degrees at most are introduced to the phase matrix. Calculated antenna unitThe excitation amplitude versus phase and error from the actual excitation are shown in fig. 3, 4. It can be seen that a DEG is calculated by the formula (2)
Figure BDA0002936188900000062
The amplitude of the error does not exceed the amplitude and phase error introduced by the phase shifter with respect to the initial excitation a, and this data can be used to calibrate the array antenna. For the antenna array antenna, the front directional diagram and the rear directional diagram are calibrated under the condition of equal-amplitude in-phase feeding, for example, as shown in fig. 5, and the antenna directional diagram after calibration is approximately the same as that under an ideal condition.

Claims (4)

1.一种阵列天线近场校准系统，待测阵列天线一共有N个天线单元，其特征在于，每个天线单元配备一个数字移相器进行相位控制，在待测阵列天线的近场放置有平面波生成器，所述平面波生成器用于在待测阵列天线处产生准平面波，所述待测阵列天线的各天线单元端口连接矢量网络分析仪端口1，矢量网络分析仪端口2连接平面波生成器。1. an array antenna near-field calibration system, the array antenna to be tested has a total of N antenna units, it is characterized in that, each antenna unit is equipped with a digital phase shifter to carry out phase control, and is placed in the near field of the array antenna to be tested. A plane wave generator. The plane wave generator is used to generate quasi-plane waves at the array antenna to be tested. Each antenna element port of the array antenna to be tested is connected to port 1 of the vector network analyzer, and port 2 of the vector network analyzer is connected to the plane wave generator. 2.根据权利要求1所述的一种阵列天线近场校准系统，其特征在于，所述矢量网络分析仪用于测量待测阵列天线与平面波生成器之间的S参数，电源用于向待测阵列天线供电，使其工作在发射状态。2. The near-field calibration system of an array antenna according to claim 1, wherein the vector network analyzer is used to measure the S-parameter between the array antenna to be measured and the plane wave generator, and the power supply is used to supply the Test the power supply of the array antenna to make it work in the transmitting state. 3.根据权利要求1所述的一种阵列天线近场校准系统，其特征在于，所述待测阵列天线在每次测量之前同时改变N个天线单元的相移，使待测阵列天线处于预先知晓的M种不同的相位状态。3. The near-field calibration system for an array antenna according to claim 1, wherein the array antenna to be measured changes the phase shifts of N antenna elements simultaneously before each measurement, so that the array antenna to be measured is in a pre-measured state. Known M different phase states. 4.基于权利要求1所述的一种阵列天线近场校准系统的测试方法，其特征在于，包括以下步骤；4. the test method based on a kind of array antenna near-field calibration system according to claim 1, is characterized in that, comprises the following steps; 步骤1：设计所需配置的M种不同的相位状态，由于校准过程中需要求解根据收发信号关系建立的线性方程组获得初始激励信息，故此相位状态矩阵PM×N的条件数需要尽可能小，以降低可能存在的误差对测量结果的影响，采用递归的方法由已知条件数的基础矩阵生成条件数尽可能小的相位矩阵PM×N；Step 1: Design M different phase states that need to be configured. Since the linear equation system established according to the relationship between the sending and receiving signals needs to be solved in the calibration process to obtain the initial excitation information, the condition number of the phase state matrix P M×N needs to be as small as possible. , in order to reduce the influence of possible errors on the measurement results, a recursive method is used to generate a phase matrix P M×N with the smallest possible condition number from the fundamental matrix of the known condition number; 步骤2：将待测阵列天线调整为发射模式，平面波生成器调整为接收模式，同时保证平面波生成器产生的静区包含待测天线所在空间；Step 2: Adjust the array antenna to be tested to the transmit mode, and the plane wave generator to the receive mode, while ensuring that the quiet zone generated by the plane wave generator includes the space where the antenna to be tested is located; 步骤3：使用矢量网络分析仪获取散射参数SN×1；Step 3: use a vector network analyzer to obtain the scattering parameter S N×1 ; 步骤4：调节待测阵列天线单元的相移共M次，测量并记录平面波生成器端所接收的信号MM×1；Step 4: adjust the phase shift of the array antenna unit to be tested for a total of M times, measure and record the signal M×1 received by the plane wave generator end; 步骤5：根据已知数据求解方程组获得测量结果；Step 5: Solve the equation system according to the known data to obtain the measurement result; 根据线性方程组的信号关系：
Figure FDA0002936188890000021
The signal relationship according to the system of linear equations:
Figure FDA0002936188890000021
 其中PM×N为预设相位状态矩阵，
Figure FDA0002936188890000022
表示矩阵的Hadamard积，aN×1表示待测阵列天线的初始激励,SN×1为测得的散射参量，MM×1为为平面波生成器端的测量结果，其中P，a，S均为已知数，将由矩阵求伪逆得到的X＝P-1*M与已知的
Figure FDA0002936188890000023
对比即可得到射频链路中阵列天线单元之间的辐相不一致性。where P M×N is the preset phase state matrix,
Figure FDA0002936188890000022
Represents the Hadamard product of the matrix, a N×1 represents the initial excitation of the array antenna to be tested, S N×1 is the measured scattering parameter, M M×1 is the measurement result at the plane wave generator end, where P, a, S are all is a known number, compare X=P -1 *M obtained by the pseudo-inverse of the matrix with the known number
Figure FDA0002936188890000023
The radiation phase inconsistency between the array antenna elements in the radio frequency link can be obtained by comparison.
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CN115118355A (en) * 2022-07-08 2022-09-27 电子科技大学 Array antenna far field detection device and method based on near field power feedback
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CN115508626A (en) * 2022-10-25 2022-12-23 西安交通大学 An antenna pattern reconstruction method and system for amplitude-only measurement in a reverberation chamber
CN115753837A (en) * 2021-10-27 2023-03-07 南京捷希科技有限公司 Plane wave generator and plane wave generator testing system
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US20220404462A1 (en) * 2021-06-22 2022-12-22 Src, Inc. Method for calibrating a phased array
US11982761B2 (en) * 2021-06-22 2024-05-14 Src, Inc. Method for calibrating a phased array
CN115753837A (en) * 2021-10-27 2023-03-07 南京捷希科技有限公司 Plane wave generator and plane wave generator testing system
CN115753837B (en) * 2021-10-27 2024-01-05 南京捷希科技有限公司 Plane wave generator and plane wave generator test system
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CN114583428B (en) * 2022-04-29 2022-07-12 中国电子科技集团公司第三十八研究所 Transmission wave-absorbing structure and antenna in-band characteristic test system
US11828781B2 (en) 2022-04-29 2023-11-28 38Th Research Institute, China Electronics Technology Group Corporation Transmission absorbing structure and antenna in-band characteristics test system
CN115118355A (en) * 2022-07-08 2022-09-27 电子科技大学 Array antenna far field detection device and method based on near field power feedback
CN115118355B (en) * 2022-07-08 2024-02-13 电子科技大学 Array antenna far-field detection device and method based on near-field power feedback
CN115508626A (en) * 2022-10-25 2022-12-23 西安交通大学 An antenna pattern reconstruction method and system for amplitude-only measurement in a reverberation chamber

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Application publication date: 20210604