A spherical phased array full-space system time delay test and stability monitoring method

Abstract

The present application mainly relates to a kind of spherical phased array full airspace system time delay test and stability monitoring method in radar measurement field.The implementation scheme is: several calibration antennas are evenly installed on the inner wall of hemispherical antenna cover at different heights and different directions, to build the full-direction three-dimensional conformal calibration antenna group of spherical phased array antenna;Multiple measuring columns are erected in the antenna cover, and the coordinate position of calibration antenna is precisely calibrated by total station instrument installed on the measuring column;The calibration antenna group, calibration antenna switching unit, circulator, transmitting filter, receiving filter, frequency synthesizer unit, frequency converter and the like are used to build the time delay calibration loop of spherical array system;Finally, the time delay of each direction of spherical array is measured one by one by using the system time delay calibration loop, and after deducting the time delay of calibration loop and the time delay of signal space transmission, the system time delay of phased array itself is finally obtained.The present application can also realize long-term monitoring of system time delay stability by regular measurement.

Description

Technical Field

[0001] This invention relates to a method for testing the time delay and monitoring the stability of a spherical phased array system across the entire airspace in the field of radar measurement. By constructing a system time delay calibration loop based on an omnidirectional, distributed, three-dimensional conformal calibration antenna group and adopting a multi-element single-channel time delay testing method, it solves the problem of testing and monitoring the system time delay of a spherical phased array in all directions under near-field conditions, and realizes the measurement of the system time delay of a spherical phased array system across the entire airspace. This invention is mainly applicable to the time delay testing of three-dimensional phased array antenna systems. Background Technology

[0002] Distance measurement is an important function of radar measurement equipment. The basic principle is to measure the spatial transmission delay of the signal between the radar antenna aperture and the target. The distance to the target is obtained by multiplying the transmission delay by the speed of light.

[0003] In actual measurement, the delay measurement results include signal space transmission delay, calibration link delay, and system delay itself. Therefore, in order to obtain high-precision distance results, the primary condition is to measure the accurate system delay. The accuracy of the system delay directly affects the accuracy of the system distance measurement.

[0004] Traditional antenna equipment system delay measurement mainly uses two methods: tower calibration and offset feed calibration. Tower calibration involves setting up a calibration tower and test equipment at a far-field distance, pointing the antenna towards the calibration tower, and conducting delay tests. The distance between the antenna and the calibration tower (spatial transmission delay) and the delay of the calibration test equipment on the tower are precisely calibrated beforehand. Finally, the system delay of the equipment is obtained by subtracting the signal spatial transmission delay and the delay of the calibration equipment on the tower from the total measurement result.

[0005] Traditional antenna equipment uses the same antenna and transceiver channel equipment during target tracking, so only tower calibration is required. However, spherical phased array antenna systems use different antenna elements for beamforming in different directions, so the system delay in each direction needs to be calibrated and monitored. Tower calibration can only measure the delay in a fixed direction. If tower calibration is to be used to calibrate the system delay in different directions, multiple calibration towers need to be built. In addition, in order to achieve a certain elevation angle in the far field, the antenna towers must be very tall, which greatly increases the construction cost and the difficulty of daily calibration and testing. Therefore, this solution is not feasible.

[0006] The offset-feed calibration scheme involves installing an offset antenna at an appropriate position on the antenna aperture. A closed-loop RF system is achieved using the offset antenna and a zero-point converter. The system's inherent time delay is obtained by subtracting the transmission distance (signal transmission delay) from the offset antenna to the feed source, the delay of the zero-point converter, and related cables from the total measurement results. However, a spherical phased array antenna consists of numerous independent antenna elements. The distance of the offset antenna to each antenna element in the near field is different. If the beam synthesized from the entire antenna array is used for calibration, the total signal delay will be the result of combining signals with different transmission delays, failing to accurately represent the true system delay. Therefore, this scheme is also not feasible. Summary of the Invention

[0007] The purpose of this invention is to avoid the shortcomings of the above-mentioned background technology and provide a method to meet the system delay testing requirements of spherical phased array in all directions of the entire space, avoiding the problems of high construction cost and high complexity caused by far-field calibration of spherical phased arrays; at the same time, it solves the problem of the inability to calibrate the system delay caused by the inconsistent delay of each array element group under near-field conditions of large spherical phased arrays, and realizes the purpose of time delay calibration testing and stability monitoring of spherical phased array systems.

[0008] The technical solution adopted in this invention is as follows:

[0009] A method for time delay testing and stability monitoring of a spherical phased array full-space system includes the following steps:

[0010] (1) Taking advantage of the conformal characteristics of the spherical phased array antenna and the hemispherical radome, multiple calibration antennas are uniformly installed at different heights and in different directions on the inner wall of the radome.

[0011] (2) Multiple fixed measuring columns of a certain height are set up inside the hemispherical radome, with the center of the sphere around the spherical phased array antenna and distributed at equal angles. All fixed measuring columns can achieve line of sight to the entire calibration antenna group. Precision angle measuring and distance measuring instruments are installed on the measuring columns to calibrate the coordinate position of the calibration antenna in the spherical array coordinate system, obtain the spatial distance between the calibration antenna and the spherical phased array antenna, and obtain the corresponding spatial transmission delay.

[0012] (3) Construct a system delay calibration loop and a spherical phased array system based on a multi-calibration antenna architecture. Select different calibration antennas and their corresponding transceiver antenna elements to be measured in sequence. Use the system delay calibration loop and the spherical phased array system to perform measurements to obtain the total delay including the phased array transceiver link, spatial transmission and system delay calibration loop. Subtract the delay of spatial transmission and the delay of the system delay calibration loop from the total delay value to obtain the delay value of the spherical phased array antenna transceiver link, i.e. the spherical array system delay. Finally, obtain the system delay value of the spherical phased array antenna in different directions in the entire space domain.

[0013] Furthermore, in step (1), the calibration antenna is a linearly polarized calibration antenna, and the normal of each calibration antenna points to the center of the spherical phased array antenna. Its beam covers the local antenna array, and all calibration antennas achieve full-angle and full-array beam coverage of the spherical phased array antenna.

[0014] Furthermore, in step (3), the transceiver antenna element at the intersection of the line connecting the center of the spherical phased array antenna and the calibration antenna with the array surface of the spherical phased array antenna is selected, or any one or more transceiver antenna elements on the beam coverage area of ​​the calibration antenna are selected as the transceiver antenna element to be measured corresponding to the calibration antenna.

[0015] Furthermore, in step (3), the system delay calibration loop includes a calibration antenna group, a calibration antenna switching unit, a circulator, a transmit filter, a receive filter, a frequency synthesizer unit, and a frequency converter; the spherical phased array system includes a baseband, a transmit switch matrix, a receive switch matrix, a transmit beamforming unit, a receive beamforming unit, and an active T / R assembly; the specific process of measurement using the system delay calibration loop and the spherical phased array system is as follows:

[0016] The baseband transmit intermediate frequency uplink measurement signal of the spherical phased array system is processed by the transmit switch matrix, transmit beamforming unit, and active T / R assembly to become an RF uplink measurement signal. This signal is then sent to the transceiver antenna element under test and radiated into space. After being received by the corresponding calibration antenna, the uplink measurement signal is processed in the system time delay calibration loop by a circulator, transmit filter, and frequency converter to convert it into a downlink measurement signal. This downlink signal is then looped back to the calibration antenna via a receive filter and circulator and radiated into space. Finally, it is received by the transceiver antenna element under test. After receiving the signal, the linear array element sequentially sends it to the active T / R component, the receiving beamforming unit, and the switching matrix, converting it into an intermediate frequency downlink measurement signal and sending it to the baseband. The baseband performs time delay calculation on the uplink and downlink measurement signals to obtain the total time delay value, which includes the phased array transceiver link, spatial transmission, and system time delay calibration loop. After deducting the time delay of spatial transmission and the time delay of the system time delay calibration loop from the total time delay, the time delay of the spherical phased array antenna transceiver link in the direction of the corresponding calibration antenna is obtained, which is the spherical array system time delay.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. This invention avoids the problems of high construction costs and high testing difficulty caused by far-field beacons for spherical phased arrays.

[0019] 2. This invention solves the problem of time delay calibration for spherical phased array systems in all directions across the entire spatial domain.

[0020] 3. This invention solves the problem of system time delay calibration under near-field conditions of large spherical phased arrays. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the layout of the all-space, distributed calibration antenna group and measurement column of the present invention.

[0022] Figure 2 This is a schematic diagram of the time delay calibration loop of the system of the present invention.

[0023] Figure 3 This is a schematic diagram of the time delay calibration signal flow of the system of the present invention. Detailed Implementation

[0024] The present invention will be further explained and described below with reference to the accompanying drawings and embodiments.

[0025] A method for time delay testing and stability monitoring of a spherical phased array full-space system includes the following steps:

[0026] (1) As Figure 1 As shown, multiple calibration antennas are deployed at different heights and in different directions on the inner wall of the hemispherical radome of the spherical phased array antenna to establish an omnidirectional wireless calibration environment for the spherical phased array antenna. The calibration antennas selected in this invention are all wide-beam, linearly polarized antennas with a 3dB beamwidth ≥ ±40°. Linearly polarized antennas were chosen primarily to simultaneously meet the testing requirements of both left-hand and right-hand circularly polarized arrays. The calibration antennas are installed on the inner wall of the hemispherical radome. In this embodiment, they are installed in four layers from bottom to top, totaling 28 antennas. Through the following arrangement, the calibration antennas achieve omnidirectional and omni-angle beam coverage of the entire spherical phased array antenna.

[0027] The first layer (bottom layer) consists of 10 calibration antennas, mounted at the same height on the hemispherical radome. The line connecting each calibration antenna to the center of the spherical phased array antenna makes a 20° angle with the horizontal plane. The 10 antennas are evenly distributed at equal angular intervals on the hemispherical radome, with the Z-axis as the central axis. The normal of each antenna points towards the center of the spherical phased array antenna. The second layer consists of 8 calibration antennas, mounted at the same height. The line connecting each antenna to the center of the spherical phased array antenna makes a 40° angle with the horizontal plane. The 8 antennas are evenly distributed at equal angular intervals on the radome, with the Z-axis as the central axis. The normal of each antenna points towards the center of the spherical phased array antenna. The third layer consists of 6... The first layer consists of six calibration antennas, all installed at the same height. The line connecting each calibration antenna to the center of the spherical phased array antenna makes a 60° angle with the horizontal plane. These six calibration antennas are evenly distributed at equal angular intervals on the hemispherical radome, with the Z-axis as the central axis. The normal of each calibration antenna points towards the center of the spherical phased array antenna. The fourth layer (top layer) consists of four calibration antennas, all installed at the same height. The line connecting each calibration antenna to the center of the spherical phased array antenna makes an 80° angle with the horizontal plane. These four calibration antennas are evenly distributed at equal angular intervals on the radome, with the Z-axis as the central axis. The normal of each calibration antenna points towards the center of the spherical phased array antenna. All calibration antennas are connected to the calibration antenna switching unit via cable assemblies.

[0028] (2) Four fixed measuring columns of a certain height are set up inside the hemispherical radome, which are distributed at equal 90° intervals around the center of the spherical array. From the top of each fixed measuring column, it is possible to see some of the 28 calibration antennas, and it is ensured that the four fixed measuring columns can see all the calibration antennas. A precision angle measuring and distance measuring instrument-total station is set up on the fixed measuring columns. The coordinate position of the calibration antenna in the spherical array coordinate system is precisely calibrated by the total station. The spatial distance between the calibration antenna and the spherical phased array antenna can be obtained from this.

[0029] This invention is not limited to installing 28 calibration antennas on the outer hemispherical radome of the spherical phased array antenna, with four layers installed at different heights and angles; nor is it limited to setting up four fixed measuring columns at 90° angles around the center of the spherical array inside the hemispherical radome; the number of calibration antennas, installation height, and position of the fixed measuring columns can be changed.

[0030] (3) Construct a system delay calibration loop and a spherical phased array system based on a multi-calibration antenna architecture, and use the system delay calibration loop and spherical phased array system for measurement; such as Figure 2As shown, the system delay calibration loop of this invention mainly consists of 28 calibration antennas, a calibration antenna switching unit, a circulator, a transmit filter, a receive filter, a frequency synthesizer unit, a frequency converter, and necessary connecting cables. The spherical phased array system mainly consists of a baseband, a transmit switch matrix, a receive switch matrix, a transmit beamforming unit, a receive beamforming unit, an active T / R (transmit / receive) assembly, and a spherical transceiver antenna array. The entire link delay is the system delay to be measured in this invention. The device connection relationships of the system delay calibration loop are as follows:

[0031] The 28 calibration antennas are connected to the branch ports of the calibration antenna switching unit via cable assemblies. These cable assemblies are amplitude- and phase-stable cables, and the time delay and phase of each cable assembly must meet certain consistency requirements to ensure that the time delay of the calibration loop is the same when different calibration antennas are selected. The calibration antenna switching unit is responsible for selecting one calibration antenna and switching it to its common selection port. The common selection port of the calibration antenna switching unit is connected to the common port of the circulator. The circulator's transmit (TX) port is connected to the input port of the transmit filter, and the output port of the transmit filter is connected to the RF input port of the frequency converter. The output of the frequency synthesizer unit is connected to the local oscillator port of the frequency converter to provide the necessary local oscillator signal to the frequency converter. The intermediate frequency output port of the frequency converter is connected to the input port of the receive filter, and the output port of the receive filter is connected to the receive (RX) port of the circulator.

[0032] Considering that the amplitude and phase consistency of all element channels in a phased array system is strictly controlled and screened during development, the time delay of each channel is consistent before phase and time delay weighted compensation. The total time delay of the entire phased array system is the sum of the group delays of individual element channels; therefore, the superimposed group delay is the same as the group delay of a single element channel. Furthermore, regarding spatial transmission distance measurement, the small size of individual elements, relative to the distance to the calibration antenna on the radome, satisfies the far-field condition. Compared to the near-field coupled transmission path, the distance of this transmission path can be accurately measured using the aforementioned total station. Therefore, based on these factors, the time delay of the entire system can be tested using a single-channel calibration method.

[0033] When selecting the calibration array element channel, select the transceiver antenna element at the intersection of the line connecting the center of the spherical phased array antenna and the calibration antenna with the spherical transceiver antenna array surface of the spherical phased array antenna; or select any one or more transceiver antenna elements within the coverage area of ​​the calibration antenna beam as the transceiver antenna element to be measured corresponding to the calibration antenna; for example... Figure 3As shown, in this invention, the array element at the intersection of the line connecting the center of the spherical phased array antenna and the calibration antenna with the spherical transceiver antenna array surface is selected as the transceiver antenna array element to be measured. Each calibration antenna corresponds to one transceiver antenna array element to be measured. A correspondence table of 28 sets of calibration antennas and transceiver antenna array elements to be measured is established. The transceiver antenna array element to be measured is denoted as TAi (i = 1, 2, 3...28), and the calibration antenna is denoted as TBi (i = 1, 2, 3...28). TAi and TBi are in one-to-one correspondence.

[0034] Using a total station, the coordinates of each calibration antenna TBi in the spherical coordinate system can be accurately measured, and the spatial distance ΔL between the calibration antenna TBi and the transceiver element TAi to be measured can be calculated. S ΔL S The corresponding time delay is denoted as ΔT. s Simultaneously, the link delay of the delay calibration loop also needs to be measured and denoted as ΔT. B After completing the delay measurement based on a single transmit / receive channel, the obtained measurement result includes the total delay value of the phased array transmit / receive channel link, spatial distance, and delay calibration loop, denoted as ΔT. The system delay ΔT O Then it is ΔT O =ΔT-ΔT S -ΔT B The system delay calibration tests of 28 sets of calibration antennas were completed sequentially to obtain the system delay values ​​of the spherical array in various directions.

[0035] like Figure 3 As shown, the specific measurement process using the system time delay calibration loop and the spherical phased array system is as follows:

[0036] First, the baseband outputs an uplink intermediate frequency measurement signal, which is sent to the transmit switch matrix. The transmit switch matrix switches the measurement signal and sends it to the beam corresponding to the transmit beamforming unit. Then, the transmit beamforming unit completes the channel switching selection of the signal, transmitting the signal only to the active T / R component channel corresponding to the selected transceiver antenna element TAi under test. The other active T / R component channels have no signal. Then, the signal undergoes upconversion, filtering, and other processing in the active T / R component to become an uplink RF measurement signal. After power amplification, it is sent to the transceiver antenna element TAi under test corresponding to the spherical transceiver antenna array, radiating the signal into space.

[0037] The uplink RF measurement signal is transmitted by the transceiver element TAI under test, transmitted through space, and then received by the calibration antenna TBi corresponding to the transceiver element TAI. After being selected by the calibration antenna switching unit, it is sent to the circulator. After being filtered by the transmit filter through the circulator's transmit (TX) channel, it is transmitted to the inverter. Then, the uplink RF measurement signal is converted into a downlink RF measurement signal in the inverter. After being filtered by the receive filter, it is re-output to the circulator's receive (RX) terminal. The circulator then sends the signal to the calibration antenna switching unit, and finally, the calibration antenna switching unit sends it to the calibration antenna TBi, which then radiates it into space.

[0038] The downlink RF measurement signal is transmitted by the calibration antenna TBi, transmitted through space, and then received by the transceiver antenna element TAi under test. It is then sent to the active T / R module, where it is amplified, filtered, and down-converted into a downlink intermediate frequency measurement signal. This signal is then sent to the receiving beamforming unit, selected by the receiving switch matrix, and finally sent to the baseband. The baseband calculates the time delay difference ΔT between the transmitted uplink and received downlink measurement signals by performing time delay processing. This ΔT includes the total transmission delay of the phased array transceiver link, space transmission, and time delay calibration loop. As mentioned earlier, the delay of the phased array transceiver link is the final system delay ΔT to be measured. O ΔT O =ΔT-ΔT S -ΔT B By selecting different calibration antennas and their corresponding transceiver elements to be measured, and performing time delay tests on all transceiver elements in sequence, the system time delay of the spherical phased array antenna in all directions across the entire airspace can be obtained. Regularly measuring the system time delay of the spherical phased array antenna and comparing it with historical measurement data allows for monitoring of the system time delay stability.

[0039] Furthermore, this method can be automated through software design, enabling one-click automation of the testing process, which can greatly improve the efficiency and accuracy of system latency testing.

Claims

1. A method for time delay testing and stability monitoring of a spherical phased array full-space system, characterized in that, Includes the following steps: (1) Taking advantage of the conformal characteristics of the spherical phased array antenna and the hemispherical radome, multiple calibration antennas are uniformly installed at different heights and in different directions on the inner wall of the radome; (2) Multiple fixed measuring columns of a certain height are set up inside the hemispherical radome, with equal angular intervals around the center of the spherical phased array antenna. All fixed measuring columns can achieve line of sight to the entire calibration antenna group. A precision angle measuring and distance measuring instrument is installed on the measuring columns to calibrate the coordinate position of the calibration antenna in the spherical array coordinate system, so as to obtain the spatial distance between the calibration antenna and the spherical phased array antenna and the corresponding spatial transmission delay. (3) Construct a system delay calibration loop and a spherical phased array system based on a multi-calibration antenna architecture. Select different calibration antennas and their corresponding transceiver antenna elements to be measured in sequence. Use the system delay calibration loop and the spherical phased array system to perform measurements to obtain the total delay including the phased array transceiver link, spatial transmission and system delay calibration loop. Subtract the delay of spatial transmission and the delay of the system delay calibration loop from the total delay value to obtain the delay value of the spherical phased array antenna transceiver link, i.e. the spherical array system delay. Finally, obtain the system delay value of the spherical phased array antenna in different directions in the entire space domain. In step (3), the system time delay calibration loop includes a calibration antenna group, a calibration antenna switching unit, a circulator, a transmit filter, a receive filter, a frequency synthesizer unit, and a frequency converter; the spherical phased array system includes a baseband, a transmit switch matrix, a receive switch matrix, a transmit beamforming unit, a receive beamforming unit, and an active T / R module; the specific process of measurement using the system time delay calibration loop and the spherical phased array system is as follows: The baseband transmit intermediate frequency uplink measurement signal of the spherical phased array system is processed by the transmit switch matrix, transmit beamforming unit, and active T / R assembly to become an RF uplink measurement signal. This signal is then sent to the transceiver antenna element under test and radiated into space. After being received by the corresponding calibration antenna, the uplink measurement signal is processed in the system time delay calibration loop by a circulator, transmit filter, and frequency converter to convert it into a downlink measurement signal. This downlink signal is then looped back to the calibration antenna via a receive filter and circulator and radiated into space. Finally, it is received by the transceiver antenna element under test. After receiving the signal, the linear array element sequentially sends it to the active T / R component, the receiving beamforming unit, and the switching matrix, converting it into an intermediate frequency downlink measurement signal and sending it to the baseband. The baseband performs time delay calculation on the uplink and downlink measurement signals to obtain the total time delay value, which includes the phased array transceiver link, spatial transmission, and system time delay calibration loop. After deducting the time delay of spatial transmission and the time delay of the system time delay calibration loop from the total time delay, the time delay of the spherical phased array antenna transceiver link in the direction of the corresponding calibration antenna is obtained, which is the spherical array system time delay.

2. The method for time delay testing and stability monitoring of a spherical phased array full-space system according to claim 1, characterized in that, In step (1), the calibration antenna is a linearly polarized calibration antenna. The normal of each calibration antenna points to the center of the spherical phased array antenna, and its beam covers a local antenna array. All calibration antennas achieve full-angle and full-array beam coverage of the spherical phased array antenna.

3. The method for time delay testing and stability monitoring of a spherical phased array full-space system according to claim 1, characterized in that, In step (3), select the transceiver antenna element at the intersection of the line connecting the center of the spherical phased array antenna and the calibration antenna with the array surface of the spherical phased array antenna, or select any one or more transceiver antenna elements in the beam coverage area of ​​the calibration antenna as the transceiver antenna element to be measured corresponding to the calibration antenna.

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