CN112904095A - Array antenna near field calibration system and method - Google Patents
Array antenna near field calibration system and method Download PDFInfo
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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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Abstract
The array antenna near-field calibration system comprises an array antenna to be tested, wherein the array antenna comprises 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, each channel of the array antenna is connected with one end of a vector network analyzer, and the other end of one end of the vector network analyzer is connected with the plane wave generator. The plane wave generator generates the quasi-plane wave in the near field of the antenna to be tested, the far field test method obviously reduces the size of a microwave dark room required by the test, avoids errors caused by path loss due to long propagation distance of electromagnetic waves, and the plane wave generator is regarded as an equivalent far field single-probe measurement system, so that the plane wave generator has the characteristics of short measurement time consumption, small occupied space and low cost.
Description
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:
wherein P isM×NIn order to pre-set the phase state matrix,
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:
wherein the matrix P ∈ CM×NThe vector a ∈ CN×1,
S∈CN×1,M∈CN×1And a is the initial excitation,
the excitation distortion caused by the radio frequency link inconsistency, and a, P are preset known parameters, S, M can be obtained by measurement.
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),
solving equation (2) to obtain the amplitude-phase distortion of the radio frequency link
And then calibrating the array antenna to be tested.
It should be noted that, the solution (2) is obtained by the pair
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:
If a quaternary array is required, i.e. two P' s2And (3) constructing a matrix cycle to obtain a phase matrix P:
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)
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. A near field calibration system of an array antenna is characterized in that 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.
2. The array antenna near field calibration system of claim 1, wherein the vector network analyzer is configured to measure an S parameter between the array antenna under test and the plane wave generator, and the power supply is configured to supply power to the array antenna under test to enable the array antenna under test to operate in a transmitting state.
3. The array antenna near field calibration system of claim 1, wherein the array antenna under test changes the phase shift of the N antenna elements simultaneously before each measurement, so that the array antenna under test is in M different phase states known in advance.
4. The test method of the array antenna near field calibration system based on claim 1 is characterized by comprising the following steps;
step 1: designing M different phases of desired configurationA phase state matrix P, which is obtained by solving a linear equation set established according to the relation of the transmitted and received signals during calibration to obtain initial excitation informationM×NNeeds to be as small as possible to reduce the influence of possible errors on the measurement result, and 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:
wherein P isM×NIn order to pre-set the phase state matrix,
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-1M and known
And obtaining the radiation inconsistency among the array antenna units in the radio frequency link through comparison.
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Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114487986A (en) * | 2022-04-18 | 2022-05-13 | 湖南艾科诺维科技有限公司 | Calibration and verification method for interferometer direction-finding array |
| CN114583428A (en) * | 2022-04-29 | 2022-06-03 | 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 |
| 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 |
| US20220404462A1 (en) * | 2021-06-22 | 2022-12-22 | Src, Inc. | Method for calibrating a phased array |
| CN115508626A (en) * | 2022-10-25 | 2022-12-23 | 西安交通大学 | Amplitude-only measurement antenna directional pattern reconstruction method and system in reverberation room |
| 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 |
| 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 |
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Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US20220404462A1 (en) * | 2021-06-22 | 2022-12-22 | Src, Inc. | Method for calibrating a phased array |
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| CN114583428A (en) * | 2022-04-29 | 2022-06-03 | 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 |
| 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 | Amplitude-only measurement antenna directional pattern reconstruction method and system in reverberation room |
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