CN-121741672-B - Amplitude-phase consistency field calibration method and system for large-scale low-frequency band phased array radar

CN121741672BCN 121741672 BCN121741672 BCN 121741672BCN-121741672-B

Abstract

The invention relates to the technical field of radars, in particular to a field calibration method and a field calibration system for amplitude-phase consistency of a large-scale low-frequency-band phased array radar, wherein the field calibration method is characterized in that a probe antenna is deployed at a position of a near field area in front of an array but meets a single array element far field condition, high-resolution time domain data are obtained by utilizing broadband frequency step scanning, multipath components such as ground reflection are filtered in a digital domain by applying gating processing based on direct wave arrival time to a time impulse response, and a virtual microwave darkroom is equivalently constructed. And then combining the accurate Fries voltage transmission model with a pre-stored antenna pattern database to invert the inherent amplitude-phase characteristics of each array element channel, and finally completing high-precision consistency calibration. The method solves the problems of multipath interference during near field test and insufficient time domain resolution in multipath separation.

Inventors

ZHOU XUHUI
ZHU CHANGAN
LEI YONGHENG
FU YIYUAN
LI ANG

Assignees

长沙气象雷达标校中心

Dates

Publication Date: 20260512
Application Date: 20260228

Claims (10)

1. The method is realized based on a probe antenna arranged in a near field region in front of a phased array wind profile radar array, wherein the distance between the probe antenna and any T/R array element in the radar meets the far field condition of a single array element; For each activated array element, executing frequency step scanning covering a preset calibration bandwidth through a probe antenna to obtain a complex frequency response data set of the array element, wherein the time domain spatial resolution corresponding to the calibration bandwidth is smaller than the path difference of direct waves and ground reflection waves between the probe antenna and a radar array surface; For each array element, performing inverse discrete Fourier transform on a complex frequency response data set to obtain a time domain impulse response, determining the arrival time of a direct wave according to the phase center coordinates of a probe antenna and the phase center coordinates of the array element, applying a time domain gating window function on the time domain impulse response according to the arrival time of the direct wave, extracting the direct wave component of the time domain impulse response, transforming the direct wave component into a frequency domain to obtain an effective transmission coefficient of the array element, and based on a Fries voltage transmission model, combining a pre-established array element pattern database and a probe antenna pattern database, inverting to determine complex intrinsic excitation of the array element according to the effective transmission coefficient of the array element, and calibrating the amplitude and/or phase of all the array element of the radar according to the complex intrinsic excitation of all the array element.
2. The method of in-situ calibration of amplitude phase uniformity for a large low band phased array radar of claim 1, wherein the calibration bandwidth is at least 200MHz.
3. The method for in-situ calibration of amplitude phase consistency of a large low-frequency phased array radar according to claim 1, wherein the frequency point interval of the frequency step scan is less than or equal to 1MHz.
4. The method for calibrating amplitude phase consistency on site of a large low-frequency band phased array radar according to claim 1, wherein the center of a time domain gating window function is aligned with the peak time of a direct wave component in a time domain impulse response, the time domain width of the time domain gating window function is smaller than the time delay difference between a ground reflected wave and a direct wave, and the time domain gating window function is a Tukey window function or a Kaiser window function.
5. The method for in-situ calibration of amplitude phase consistency of a large low-band phased array radar according to claim 1, wherein the fries voltage transmission model is expressed as: ; Wherein: Is radar No Each array element is at the center frequency Complex intrinsic stimuli at; is the first After time domain gating processing is carried out on each array element, the extracted effective transmission coefficient only containing direct wave components is extracted; Is the working center frequency of the radar; is the first Straight line Euclidean distance between the phase center of each array element and the phase center of the probe antenna; For the central frequency A corresponding free space wavelength; is the inverse of the free space voltage transmission loss; in the direction of the probe antenna The complex gain in the direction of each array element, The phase center of the probe antenna is taken as the origin point to the first Local spherical coordinate system angles of the array elements; is the first The array elements consider the complex pattern gain of the embedded units in the array mutual coupling environment, Is according to the first The phase centers of the array elements are used as origins and point to the local spherical coordinate system angle of the probe antenna; For the central frequency The corresponding wave number is calculated as the formula ; Is a compensation factor for the spatial phase delay.
6. The method for on-site calibration of amplitude-phase consistency of a large low-frequency phased array radar according to claim 1, wherein the pre-established array element pattern database is obtained by: Full-wave electromagnetic simulation is carried out on array elements in the phased array wind profile radar, wherein for any target array element, a corresponding simulation calculation model comprises a metal base plate of a radar array surface, an antenna housing, the target array element and at least two adjacent other array elements of the target array element in the array, so as to obtain target array element pattern data for accurately simulating an array mutual coupling effect and an edge truncation effect, and a database comprising array element non-uniformity pattern data at different positions in the array is established based on simulation results of all the array elements.
7. The method for in-situ calibration of amplitude phase consistency of a large low-band phased array radar according to claim 1, wherein calibrating the amplitude and/or phase of all the array elements of the radar according to the complex intrinsic excitation of all the array elements comprises: Selecting an array element as a reference array element, determining a compensation coefficient of the array element to be calibrated according to the complex intrinsic excitation of the array element to be calibrated and the complex intrinsic excitation of the reference array element for each array element to be calibrated except the reference array element, wherein the compensation coefficient of the array element to be calibrated comprises an amplitude compensation coefficient and/or a phase compensation coefficient, and calibrating the corresponding array element according to the compensation coefficient of the array element to be calibrated.
8. The method for in-situ calibration of amplitude phase consistency of a large low-band phased array radar according to claim 1, wherein calibrating the amplitude and/or phase of all the array elements of the radar according to the complex intrinsic excitation of all the array elements comprises: Determining standard deviation of intrinsic amplitude and standard deviation of intrinsic phase according to complex intrinsic excitation of all array elements, comparing the standard deviation of intrinsic amplitude with a preset first threshold value to judge whether the amplitude consistency of all the array elements of the radar meets the standard, comparing the standard deviation of intrinsic phase with a preset second threshold value to judge whether the phase consistency of all the array elements of the radar meets the standard, and selectively calibrating the amplitude and the phase of all the array elements of the radar according to a comparison result.
9. A system for field calibration of amplitude phase consistency for a large low-frequency phased array radar, comprising: The probe antenna is arranged in a near field region in front of the radar array, and the distance between the probe antenna and any T/R array element in the phased array wind profile radar meets the far field condition of a single array element; the broadband transceiver is connected with the beam control unit of the phased array wind profile radar and the probe antenna and is configured to generate frequency step-by-step scanning signals, and receive and measure response signals from each active array element so as to acquire a complex frequency response data set; the positioning device is configured to measure and output three-dimensional coordinates of the phase center of the probe antenna and the phase center of each array element; the signal processing and controlling device is in communication connection with the broadband receiving and transmitting device and the positioning device and is used for controlling the sequential activation of array elements and the scanning process of the probe antenna, determining the arrival time of direct waves according to the three-dimensional coordinates of the phase center of the probe antenna and the phase center of each array element, performing inverse discrete Fourier transform, time domain gating and frequency domain transform on a complex frequency response data set to obtain effective transmission coefficients, performing parameter inversion on the basis of a Fries voltage transmission model, a pre-established array element pattern database and a probe antenna pattern database to obtain complex inherent excitation, generating amplitude and phase compensation coefficients according to the complex inherent excitation of all the array elements, and calibrating the amplitude and/or the phase of all the array elements of the radar.
10. The system of claim 9, wherein the broadband transceiver is integrated with a vector network analysis module for complex parameter measurements at stepped frequency points.

Description

Amplitude-phase consistency field calibration method and system for large-scale low-frequency band phased array radar Technical Field The invention relates to the technical field of radars, in particular to a method and a system for calibrating amplitude-phase consistency on site of a large-scale low-frequency band phased array radar. Background The large low-frequency band phased array wind profile radar is key equipment in the fields of meteorological detection, ionosphere monitoring and the like, and generally has a huge physical caliber and a longer working wavelength, wherein the physical caliber is more than 10 meters by 10 meters, and the working wavelength is about 0.5-1 meter. To ensure beam pointing accuracy, low sidelobe performance and reliability of the detected data, high-accuracy amplitude and phase (amplitude-phase) consistency calibration must be performed on hundreds or thousands of T/R array elements in the array. However, in-situ calibration of such radars presents serious challenges, and conventional approaches all have inherent limitations: First, stringent far field test conditions cannot be achieved in the field. According to the 2D 2/lambda far field criterion in antenna theory, D is the antenna caliber, lambda is the wavelength, and for a typical radar with caliber of 10 meters and wavelength of 0.67 meters, the minimum required far field distance exceeds 300 meters, and the Fresnel area is too large. The engineering cost is extremely high and the feasibility is generally not realized when the large-scale test site and the signal source iron tower with the height of hundreds of meters are deployed on site. Second, when measurements are made at achievable close distances, such as radiating near field or mid field regions, strong multipath interference severely distorts the measurement data. Because of strong diffraction capability of low-frequency electromagnetic waves and wide antenna beam, reflected signals from the ground interfere with direct signals between the probe antenna and the radar array surface on the array surface. The interference causes the amplitude fluctuation of the synthesized signals received by array elements at different spatial positions to be as high as 3-6dB, and the phase deviation exceeds 20 degrees, so that the conventional calibration method based on single-frequency point measurement is completely ineffective. While the prior art attempts to utilize the radar's own operating bandwidth (e.g., 20 MHz) for time domain analysis, intended to rake paths through "time domain gating" techniques, are limited by physical principles, with the inherent time domain resolution of narrowband signals being severely inadequate. The 20MHz bandwidth corresponds to a range resolution of about 15 meters, whereas the path difference between the direct wave and the ground reflected wave in field testing is typically only around 1 meter. Therefore, the two are completely overlapped in the time domain, and cannot be effectively separated, and the time domain gating technology is also ineffective in practical application. For this reason, there is a need for a method and system for amplitude phase consistency field calibration of large low-frequency phased array radars. Disclosure of Invention In view of the above-mentioned shortcomings and disadvantages of the prior art, the invention provides a method and a system for calibrating amplitude-phase consistency on site of a large-scale low-frequency band phased array radar, which solve the problems of multipath interference during near field test and insufficient time domain resolution in multipath separation. In order to achieve the above purpose, the main technical scheme adopted by the invention comprises the following steps: The invention provides a field calibration method for amplitude phase consistency of a large low-frequency band phased array radar, which is realized based on a probe antenna arranged in a near field region in front of a phased array wind profile radar array, wherein the distance between the probe antenna and any T/R array element in the radar meets the far field condition of a single array element; For each activated array element, executing frequency step scanning covering a preset calibration bandwidth through a probe antenna to obtain a complex frequency response data set of the array element, wherein the time domain spatial resolution corresponding to the calibration bandwidth is smaller than the path difference of direct waves and ground reflection waves between the probe antenna and a radar array surface; For each array element, performing inverse discrete Fourier transform on a complex frequency response data set to obtain a time domain impulse response, determining the arrival time of a direct wave according to the phase center coordinates of a probe antenna and the phase center coordinates of the array element, applying a time domain gating window function on the time domain impulse response acc