CN118259243B - Phased array weather radar calibration method and calibration system - Google Patents

Abstract

The invention discloses a phased array weather radar calibration method and a calibration system, wherein the method comprises the steps of controlling an unmanned aerial vehicle loaded with a calibration source to fly to a preset space position; the control display terminal sends a calibration control instruction to the unmanned aerial vehicle remote controller, and the unmanned aerial vehicle remote controller transmits the calibration control instruction to the control module of the unmanned aerial vehicle in a wireless communication mode; under the control of the control module, the calibration source calibrates the radar to be tested at a preset space position; the calibration source transmits data in the calibration process to the control display terminal through the unmanned aerial vehicle control module and the unmanned aerial vehicle remote controller in sequence; or the radar to be tested transmits the data in the calibration process to the control display terminal; and the control display terminal processes the received data in the calibration process to obtain a calibration result. The method solves the calibration difficulty of the phased array weather radar, reduces the calibration complexity and improves the calibration accuracy.

Description

Phased Array Weather Radar Calibration Method and Calibration System

Technical Field

The invention belongs to the technical field of radar calibration, and in particular relates to a calibration method and a calibration system for an airborne X (C) band phased array weather radar.

Background technique

Radar calibration is a critical and complex project. Any radar must be calibrated to determine the system parameters, so that the radar detection data is more accurate and reliable. Therefore, radar calibration has always been a research topic that has received much attention. Phased array weather radar is a quantitative detection device that needs to accurately detect the absolute intensity of clouds, so higher requirements are placed on the calibration accuracy of weather radars.

The traditional radar calibration method is to measure relevant parameters with the help of instruments, which is labor-intensive, and the calibration test of weather radar basically stays at the extension calibration. During calibration, it is impossible to calibrate the entire radar detection link, and only calibration tests can be performed on extensions such as transmitters, receivers, antennas, and servo turntables. The extension calibration test can only be performed on testable RF interfaces, and calibration tests on the entire system cannot be performed. The test results are closely related to the operational specifications during the test, and calibration tests cannot be performed on extensions without RF interfaces such as antennas and antenna covers, and the calibration blind area is significant.

In addition, weather radars of many bands are usually installed on iron towers several tens of meters high, and the instruments used for extension calibration must be moved to the iron tower to carry out the calibration work, which is difficult to operate in practice. Among them, X-band radars are densely distributed and the number of radars far exceeds that of traditional weather radars. If each radar adopts the traditional extension calibration method, the workload is unimaginable.

Summary of the invention

The purpose of the present invention is to provide a phased array weather radar calibration method and calibration system to solve the problem that traditional calibration technology uses instruments to test related parameters, resulting in a large workload and difficult actual operation, and the problem that traditional calibration technology cannot calibrate the entire link of radar detection.

The present invention solves the above technical problems through the following technical solutions: a phased array weather radar calibration method, the calibration method comprising the following steps:

Before calibration, the UAV remote controller controls the UAV equipped with the calibration source to fly to a predetermined spatial position by wireless communication; at the predetermined spatial position, the antenna of the calibration source and the antenna of the radar under test meet the far-field condition, and the main beam of the calibration source is aligned with the main beam of the radar under test;

During calibration, the control display terminal sends a calibration control instruction to the drone remote controller, and the drone remote controller transmits the calibration control instruction to the control module of the drone in a wireless communication manner;

Under the control of the control module, the calibration source calibrates the radar under test at a predetermined spatial position;

The calibration source transmits the data in the calibration process to the control and display terminal in sequence through the control module of the drone and the drone remote controller; or the radar under test transmits the data in the calibration process to the control and display terminal;

The control display terminal processes the received data in the calibration process to obtain a calibration result.

Furthermore, the far-field condition is:

R ≥ (2D ² ) / λ;

Where R represents the distance between the calibration source and the radar under test, D represents the effective aperture of the antenna of the radar under test, and λ represents the wavelength of the transmitted signal of the radar under test.

Furthermore, the specific implementation process of aligning the main beam of the calibration source with the main beam of the radar under test is:

The antenna elevation angles of the calibration source and the radar under test are adjusted so that the antenna of the calibration source is parallel to the antenna of the radar under test, so that the main beam of the calibration source is aligned with the main beam of the radar under test.

Furthermore, the calibration source calibrates the radar under test at a predetermined spatial position, specifically including the calibration of the transmit power of the radar under test and the calibration of the receiving performance of the radar under test;

The specific implementation process of the transmit power calibration of the radar under test is:

The antenna of the radar under test transmits signals outward;

The antenna of the calibration source receives the signal transmitted by the radar under test, and the signal processing unit of the calibration source processes the signal received by its antenna to obtain the signal power;

The signal power output by the calibration source is transmitted to the control display terminal via the control module and the UAV remote controller in sequence;

The control display terminal calculates the transmission power of the radar under test according to the signal power output by the calibration source;

The specific implementation process of the receiving performance calibration of the radar under test is:

The signal generating unit of the calibration source generates an interference signal, and the interference signal is radiated outward through the antenna of the calibration source;

The antenna of the radar under test receives the interference signal, and the radar under test generates interference echo data according to the interference signal;

The interference echo data is transmitted to a control and display terminal, and the control and display terminal calculates reflectivity according to the interference echo data to achieve calibration of receiving performance of the radar under test.

Furthermore, the specific calculation formula for calculating the transmit power of the radar under test according to the signal power output by the calibration source is:

10lgP _t1 ＝10lgP _s2 －G _t1 －G _r2 ＋10lgF＋10lgR＋32.4;

Wherein, _Pt1 represents the transmitting power of the radar under test, _Ps2 represents the signal power output by the calibration source, _Gt1 represents the antenna transmitting gain of the radar under test, _Gr2 represents the antenna receiving gain of the calibration source, F represents the signal frequency transmitted by the radar under test, and R represents the distance between the calibration source and the radar under test.

Furthermore, the reflectivity is calculated according to the interference echo data, and the specific implementation process is as follows:

Obtaining interference echo intensity according to the interference echo data;

The interference signal power received by the radar under test is calculated according to the interference echo intensity. The calculation formula of the interference signal power is:

P _r1 =Ar*P _s1 +Br;

Wherein, P _r1 represents the interference signal power received by the radar under test, P _s1 represents the interference echo intensity received by the radar under test, and Ar and Br represent the coefficients to be determined respectively;

Adjust the distance between the calibration source and the radar under test, and calculate the interference echo intensity and interference signal power at another distance in the same way;

Determine the coefficients Ar and Br according to the interference echo intensity and interference signal power at two distances;

Combining the calculation formula of interference signal power and radar equation, we can get the expression of radar reflectivity factor, which is:

;

Where Z represents the radar reflectivity factor, λ represents the wavelength of the transmitted signal of the radar under test, R represents the distance between the calibration source and the radar under test, _Pt1 represents the transmitted power of the radar under test, and c represents the speed of light. represents the pulse width of the transmitted signal of the radar under test, G _t1 represents the antenna transmission gain of the radar under test, G _r1 represents the antenna receiving gain of the radar under test, θ represents the antenna azimuth beam width of the radar under test, represents the antenna elevation beam width of the radar under test, and K represents the water droplet dielectric constant;

Based on the calculation formula of interference signal power, take 20 times the logarithm on both sides of the equal sign of the expression of radar reflectivity factor to obtain radar reflectivity. The specific formula is:

dBZ＝factor＋20logR＋Ar*P _s1 +Br;

;

Wherein, dBZ represents radar reflectivity and factor represents calibration parameter.

Furthermore, the calibration of the measured radar by the calibration source at a predetermined spatial position also includes a multi-radar intensity detection consistency calibration, and the specific implementation process is as follows:

For the i-th measured radar, the i-th measured radar transmits a signal to the calibration source, the calibration source receives the signal transmitted by the i-th measured radar, calculates the signal power P _s2,i , and saves the signal power P _s2,i and the spatial relative position between the i-th measured radar and the calibration source;

The calibration source transmits an interference signal to the i-th radar under test, the i-th radar under test receives the interference signal transmitted by the calibration source and generates interference echo data, and the control and display terminal calculates the interference echo intensity P _s1,i according to the interference echo data;

For the i+1th measured radar, adjusting the spatial position of the calibration source or the i+1th measured radar so that the spatial relative position between the i+1th measured radar and the calibration source is consistent with the spatial relative position between the i-th measured radar and the calibration source, and the parameter setting of the calibration source remains unchanged;

The i+1th radar under test transmits a signal to the calibration source, the calibration source receives the signal transmitted by the i+1th radar under test, calculates the signal power P _s2,i+1 , and saves the signal power P _s2,i+1 and the spatial relative position between the i+1th radar under test and the calibration source;

The calibration source transmits an interference signal to the i+1th radar under test, the i+1th radar under test receives the interference signal transmitted by the calibration source and generates interference echo data, and the control and display terminal calculates the interference echo intensity P _s1,i+1 according to the interference echo data;

Calculating the intensity detection difference between the i-th measured radar and the i+1-th measured radar according to the signal power P _s2,i , the signal power P _s2,i+1 , the interference echo intensity P _{s1, i} and the interference echo intensity P s1,i+1;

The intensity detection consistency between the i-th measured radar and the (i+1)-th measured radar is determined according to the intensity detection difference.

Furthermore, the specific calculation formula of the intensity detection difference is:

ΔP=(P _s2,i -P _s2,i+1 ) + (P _s1,i -P _s1,i+1 );

Wherein, ΔP represents the intensity detection difference.

Based on the same concept, the present invention also provides a phased array weather radar calibration system, the calibration system comprising a drone, a drone remote controller, a calibration source and a control display terminal, the calibration source is mounted on the drone and connected to the control module of the drone, and the drone remote controller is connected to the control display terminal;

The UAV remote controller is used to control the UAV mounted with the calibration source to fly to a predetermined spatial position by wireless communication, at which the antenna of the calibration source and the antenna of the radar under test meet the far-field condition, and the main beam of the calibration source is aligned with the main beam of the radar under test; and receive the calibration control instruction sent by the control display terminal, and control the calibration source to calibrate the radar under test at the predetermined spatial position through the control module of the UAV by wireless communication according to the calibration control instruction;

The calibration source is used to calibrate the radar under test at a predetermined spatial position under the control of the control module;

The control and display terminal is used to send calibration control instructions to the UAV remote controller; and receive and process the data in the calibration process to obtain the calibration result.

Furthermore, the calibration source includes a signal generating unit, a signal processing unit, a transceiver switching module and an antenna; the signal generating unit and the signal processing unit are connected to the control module of the drone, the signal generating unit and the signal processing unit are also connected to the transceiver switching module, and the transceiver switching module is connected to the antenna;

The signal generating unit is used to generate an interference signal under the control of the control module;

The signal processing unit is used to process the signal received by the antenna to obtain signal power, and transmit the signal power to the control and display terminal through the control module and the drone remote controller in sequence;

The transmitting and receiving switching module is used to switch between the transmitting and receiving modes;

The antenna is used to radiate the interference signal generated by the signal generating unit outwardly; and to receive the signal emitted outwardly by the radar under test.

Furthermore, the calibration source also includes a protective cover, and the signal generating unit, the signal processing unit and the transceiver switching module are arranged in the protective cover.

Furthermore, the control display terminal and the drone remote controller are connected in communication using RS422 communication mode.

Beneficial Effects

Compared with the prior art, the advantages of the present invention are:

The present invention realizes the calibration of the radar's transmitting power and receiving performance by mutually transmitting and receiving signals between the radar and the calibration source, which well solves the calibration difficulty of the X (C) band phased array weather radar, reduces the calibration complexity, and improves the calibration accuracy; the present invention only needs to control the UAV to make the calibration source enter the predetermined spatial position to complete the automatic calibration and result output, which greatly reduces the requirements of the calibration work on the operator and the calibration error caused by the individual differences of the operators, simplifies the operator's work difficulty and workload, and is of great significance to the operation and maintenance of the X-band phased array weather radar. During the calibration process, there is no need to remove the radar module, connect cables, carry instruments, etc.

The present invention can realize the calibration of the entire radar detection link, reflecting the overall performance of the radar. There is no need to perform calibration tests on extensions without radio frequency interfaces such as antennas, thus avoiding calibration blind spots. The present invention can also realize the consistency calibration of multi-radar detection intensity, thus improving the accuracy and availability of phased array weather radar networking products.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only one embodiment of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a schematic diagram of a phased array weather radar calibration principle according to an embodiment of the present invention;

FIG2 is a calibration radiation link model according to an embodiment of the present invention;

3 is a schematic diagram of the alignment of the main beam of the calibration source and the main beam of the radar under test in an embodiment of the present invention;

FIG4 is a schematic diagram of a multi-radar intensity detection consistency calibration principle according to an embodiment of the present invention;

FIG. 5 is a structural block diagram of a calibration source in an embodiment of the present invention.

Explanation of the reference numerals: 1- tested radar, 11- the i-th tested radar, 12- the i+1-th tested radar, 2- the UAV equipped with the calibration source, 3- the UAV remote controller, 4- the control display terminal, 5- the radar data server, 6- the main beam of the calibration source, 7- the main beam of the tested radar.

Detailed ways

The following is a clear and complete description of the technical solution in the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

The technical solution of the present application is described in detail with specific embodiments below. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described in detail in some embodiments.

Example 1

As shown in Figure 1, the calibration system of the phased array weather radar includes a drone, a drone remote controller 3, a calibration source and a control display terminal 4. The calibration source is mounted on the drone and connected to the control module of the drone. The control module of the drone communicates with the drone remote controller 3 using wireless communication. The drone remote controller 3 is connected to the control display terminal 4, the control display terminal 4 is connected to the radar data server 5, and the radar data server 5 is connected to the radar 1 under test.

The several components of the calibration system are easy to disassemble and assemble, which is convenient for separate packaging and transportation of the calibration system. The calibration source is directly connected to the control module inside the drone, and the drone remote controller 3 is connected to the control display terminal 4. The data in the calibration process and the calibration control instructions are transmitted by means of the communication link between the drone and the drone remote controller 3 on the ground, realizing the real-time transmission of the calibration data in the air and the control display terminal 4 on the ground, and the radar data server 5 is transmitted to the control display terminal 4 through the network TCP/IP protocol.

A phased array weather radar calibration method provided by an embodiment of the present invention comprises the following steps:

Step S1: Before calibration, the UAV remote controller 3 controls the UAV 2 equipped with the calibration source to fly to a predetermined spatial position by wireless communication.

In order to get rid of the dependence of traditional signal source calibration methods on test towers, high-rise buildings, etc., and to carry out calibration of phased array weather radars under various terrain conditions, the present invention uses a drone equipped with a calibration source to fly to a predetermined spatial position. The operator controls the drone remote control 3 to make the drone 2 equipped with the calibration source fly to a predetermined spatial position, or controls the display terminal 4 to calculate the spatial position of the calibration source according to demand, generates a flight trajectory instruction according to the spatial position of the calibration source, and controls the drone to fly to the predetermined spatial position through the drone remote control 3. This method is flexible in operation, the flight trajectory is controllable, the flight attitude is stable, and it can hover in the air for a long time, and the position accuracy during hovering is high.

The radar 1 under test and the drone both have their own positioning modules. According to the positions of the radar 1 under test and the drone, it can be determined whether the antenna of the calibration source and the antenna of the radar 1 under test meet the far-field condition. At the predetermined spatial position, the antenna of the calibration source and the antenna of the radar 1 under test meet the far-field condition. Only when the far-field condition is met can the electromagnetic wave signal be fully formed in the direction of the main beam of the directional antenna and the nominal antenna gain be obtained. In this embodiment, the far-field condition is:

R ≥ (2D ² ) / λ （1）

Wherein, R represents the distance between the calibration source and the radar 1 under test, D represents the effective aperture of the antenna of the radar 1 under test, and λ represents the wavelength of the transmitted signal of the radar 1 under test. Usually, the distance between the calibration source and the radar 1 under test is from several hundred meters to several kilometers, which meets the far-field condition.

On the basis of satisfying the far-field conditions, the main beam of the antenna of the measured radar 1 must be ensured to be coaxial with the main beam radiation direction of the calibration source antenna and the axis is aligned, which is the theoretical calibration radiation link model, as shown in Figure 2. In a specific embodiment of the present invention, the main beam 6 of the calibration source is aligned with the main beam 7 of the measured radar by adjusting the antenna elevation angles of the calibration source and the measured radar 1. As shown in Figure 3, the antenna elevation angle α of the measured radar 1 is known, and the antenna elevation angle β of the calibration source is adjusted to make the antenna elevation angle β of the calibration source equal to the antenna elevation angle α of the measured radar 1, thereby making the antenna of the calibration source parallel to the antenna of the measured radar 1, that is, the main beam 6 of the calibration source is aligned with the main beam 7 of the measured radar 1. The antenna elevation angle of the calibration source can be adjusted manually, and the antenna elevation angle of the calibration source is adjusted to be consistent with the antenna elevation angle of the measured radar 1 before calibration.

Step S2: During calibration, the control display terminal 4 sends a calibration control instruction to the drone remote controller 3, and the drone remote controller 3 transmits the calibration control instruction to the control module of the drone in a wireless communication manner.

During calibration, the control display terminal 4 sends instructions to the calibration source and the radar 1 under test, and sets the working mode (such as the transmitting mode or the receiving mode) of the calibration source and the radar 1 under test, so as to prepare for the calibration source and the radar 1 to transmit and receive signals to each other and perform calibration.

The transmission path of the calibration control instruction is control display terminal 4->UAV remote controller 3->UAV control module->calibration source. In this embodiment, the calibration control instruction includes a transmit power calibration control instruction, a receiving performance calibration control instruction, and a multi-radar intensity detection consistency calibration control instruction. Different calibrations are performed on the radar 1 under test according to different calibration control instructions.

Step S3: Under the control of the control module, the calibration source calibrates the radar 1 under test at a predetermined spatial position.

Different calibration contents correspond to different calibration processes. In a specific embodiment of the present invention, the calibration of the radar 1 under test by the calibration source at a predetermined spatial position includes the calibration of the transmitting power of the radar 1 under test, the calibration of the receiving performance of the radar 1 under test, and the calibration of the consistency of multi-radar intensity detection.

The transmission power calibration mainly tests the transmission power of the radar 1 under test, that is, the signal power emitted by the radar 1 under test. The specific implementation process of the transmission power calibration of the radar 1 under test is:

Step S3.11: the radar 1 under test operates in a normal service mode, and the antenna of the radar 1 under test transmits signals outward;

Step S3.12: The antenna of the calibration source receives the signal transmitted by the radar 1 under test, and the signal processing unit of the calibration source processes the signal received by the antenna of the calibration source to obtain the signal power;

Step S3.13: the signal power output by the calibration source in step 3.12 is transmitted to the control display terminal 4 via the control module of the drone and the drone remote controller 3 in sequence;

Step S3.14: Control the display terminal 4 to calculate the transmission power of the radar 1 under test according to the signal power output by the calibration source.

In this embodiment, the signal processing unit of the calibration source is a power detection module. The power detection module adopts RF envelope detection technology, that is, it adopts an RF detector and an AD converter. The RF detector detects the signal power analog value from the signal received by the antenna of the calibration source, and the AD converter converts the signal power analog value into a signal power digital value.

According to the electromagnetic wave radiation formula, the transmitting power of the transmitting end can be calculated according to the signal power sampled by the receiving end, and vice versa, the signal power sampled by the receiving end can be calculated according to the transmitting power of the transmitting end. When calibrating the transmitting power, the calibration source is the receiving end and the radar 1 under test is the transmitting end; when calibrating the receiving performance, the calibration source is the transmitting end and the radar 1 under test is the receiving end.

The control display terminal 4 calculates the transmission power of the radar 1 under test according to the signal power output by the calibration source. The specific calculation formula is:

10lgP _t1 ＝10lgP _s2 －G _t1 －G _r2 ＋10lgF＋10lgR＋32.4 (2)

Among them, P _t1 represents the transmission power of the radar 1 under test, a calibration parameter, and the unit is W; P _s2 represents the signal power output by the calibration source, a parameter output by the calibration source (obtained by step S3.12), and the unit is W; G _t1 represents the antenna transmission gain of the radar 1 under test, a known parameter, and the unit is dB; G _r2 represents the antenna receiving gain of the calibration source, a known parameter, and the unit is dB; F represents the signal frequency transmitted by the radar 1 under test, a known parameter, and the unit is Mhz; R represents the distance between the calibration source and the radar 1 under test, a known parameter, and is obtained during the calibration test. Substituting each parameter into formula (2), the transmission power of the radar 1 under test can be obtained, and the transmission performance calibration of the radar 1 under test can be completed.

During the receiving performance calibration, the radar 1 under test needs to turn off the transmitting signal and work in the receiving state. The specific implementation process of the receiving performance calibration of the radar 1 under test is as follows:

Step S3.21: The signal generating unit of the calibration source generates an interference signal, and the interference signal is radiated outward through the antenna of the calibration source;

Step S3.22: The antenna of the radar under test 1 receives the interference signal radiated by the calibration source, and the radar under test 1 generates interference echo data according to the interference signal;

Step S3.23: The interference echo data is transmitted to the control display terminal 4, and the control display terminal 4 calculates the reflectivity according to the interference echo data to achieve the receiving performance calibration of the radar 1 under test.

The interference signal radiated outward by the calibration source can be any signal type that can be recognized by the radar 1 under test, and the calibration source can achieve adaptation by selecting the corresponding signal waveform according to the signal waveform of the radar 1 under test. In this embodiment, the interference signal radiated by the calibration source is a single-frequency continuous signal, which can be received by the X (C) band phased array weather radar. The interference signal can generate interference echo data according to the normal receiving and processing flow of the radar 1 under test, and the characteristics of the interference echo data are used to analyze the receiving performance of the radar, thereby realizing the calibration of the radar receiving performance.

The control display terminal 4 obtains the interference echo data from the radar data server 5 through the network, and the control display terminal 4 parses the interference echo data according to the data storage protocol of the interference echo data. During calibration, the transmitter of the radar 1 under test is turned off, and the radar 1 under test can only receive noise signals, and the interference signal intensity emitted by the calibration source is much greater than the noise signal intensity. Therefore, in the interference echo data, the echo data of the interference signal emitted by the calibration source can be clearly seen only from the signal intensity. The control display terminal 4 extracts the maximum intensity value from the interference echo data to obtain the interference echo intensity. After the control display terminal 4 extracts the interference echo intensity, the interference echo intensity can be used to perform calibration calculations on the receiving performance. The specific principle is as follows:

It is known that the receiving system of the radar 1 under test is a linear system, and the interference echo intensity is linearly related to the signal power received by the antenna array of the radar 1 under test, which is expressed by the following formula:

P _r1 =Ar*P _s1 +Br (3)

Wherein, P _r1 represents the interference signal power received by the radar 1 under test; P _s1 represents the interference echo intensity received by the radar 1 under test, and this parameter can be obtained according to the interference echo data during calibration; Ar and Br respectively represent coefficients to be determined.

The interference signal power P _r1 received by the radar 1 under test can be calculated by the electromagnetic wave radiation formula, and its principle is similar to formula (2). At this time, the transmitting end is the calibration source and the receiving end is the radar 1 under test. The specific formula is:

10lgP _r1 ＝10lgP _t2 ＋G _t2 －G _r1 －10lgF－10lgR－32.4 (4)

Among them, P _t2 represents the transmission power of the calibration source, which is a known parameter and the unit is W; G _t2 represents the antenna transmission gain of the calibration source, which is a known parameter and the unit is dB; _Gr1 represents the antenna receiving gain of the radar 1 under test, which is a known parameter and the unit is dB.

From formula (4), it can be seen that when the distance R between the calibration source and the radar 1 under test is different, the interference signal power P _r1 received by the radar 1 under test is also different, and the interference echo strength P _s1 corresponding to different interference signal power P _r1 is also different. Therefore, when calibrating the receiving performance, the distance R between the calibration source and the radar 1 under test is changed once, and the interference echo strength and interference signal power at two different distances R can be obtained. Substituting the interference echo strength and interference signal power at two different distances R into formula (3), the coefficients Ar and Br can be determined.

Combining the interference signal power calculation formula (3) with the radar equation, we get the expression of the radar reflectivity factor, which is:

(5)

Wherein, Z represents the radar reflectivity factor; λ represents the wavelength of the transmitted signal of the radar 1 under test, in m, a known parameter; R represents the distance between the calibration source and the radar 1 under test; P _t1 represents the transmitted power of the radar 1 under test, in W, obtained during the calibration of the transmitted power; c represents the speed of light, which is 3e ⁸ m/s; represents the pulse width of the transmitted signal of the radar 1 under test, in s, a known parameter; G _t1 represents the antenna transmission gain of the radar 1 under test, in dB, a known parameter; G _r1 represents the antenna receiving gain of the radar 1 under test, in dB, a known parameter; θ represents the antenna azimuth beam width of the radar 1 under test, in degrees, a known parameter; represents the antenna elevation beam width of the radar 1 under test, in degrees, a known parameter; K represents the water droplet dielectric constant, specifically 0.93.

Substitute equation (3) and various parameters into equation (5), and take 20 times the logarithm of both sides of the equal sign of equation (5) to obtain the radar reflectivity. The specific formula is:

dBZ＝factor＋20logR＋Ar*P _s1 +Br (6)

(7)

Wherein, dBZ represents radar reflectivity and factor represents calibration parameter.

The interference echo intensity Srr calculated by the control and display terminal 4 according to the interference echo data can be converted into radar reflectivity dBZ through the above formula (6). This process is the radar receiving performance calibration.

The calibration system of the present invention can also detect the consistency of the intensity detection of multiple radars. The basic principle of radar operation is that the radar's transmitting system transmits a signal to the target, and then the receiving system receives the signal returned from the target and analyzes it to confirm the intensity of the target. In theory, as long as the outward radiated signal power of the two radars is consistent and the receiving gain of the received return signal is consistent, then the intensity of the two detecting the same target is consistent. Based on this, the present invention proposes to use a calibration system to calibrate the transmission power of the radar transmitting system and the receiving gain of the receiving system to measure the consistency of the intensity detection of the two radars.

The calibration system of the present invention can both receive signals transmitted by radars and transmit signals to radars. The calibration system is used to test the transmitting and receiving systems of multiple radars, thereby calibrating the intensity detection consistency of multiple radars.

As shown in FIG4 , when performing a detection consistency calibration test on two different radars 11/12, it is necessary to ensure that the parameter settings of the calibration system itself remain unchanged when calibrating the two radars 11/12, and at the same time ensure that the spatial relative positions of the calibration source and the two radars 11/12 are consistent. The spatial relative position information includes the azimuth, pitch, and radial distance between the calibration source and the radar, and the calibration system can obtain this information in real time.

In a specific embodiment of the present invention, the specific implementation process of multi-radar intensity detection consistency calibration is:

Step S3.31: When the spatial relative position between the calibration source and the i-th measured radar 11 is determined, the i-th measured radar 11 transmits a signal to the calibration source, the calibration source receives the signal transmitted by the i-th measured radar 11, and calculates the signal power P _s2,i (consistent with the transmit power calibration process, it is not necessary to calculate the transmit power of the i-th measured radar 11), and saves the signal power P _s2,i and the spatial relative position between the i-th measured radar 11 and the calibration source;

Step S3.32: Keeping the spatial position of the calibration source unchanged, the calibration source transmits an interference signal to the i-th radar under test 11, the i-th radar under test 11 receives the interference signal transmitted by the calibration source and generates interference echo data, and controls the display terminal to calculate the interference echo intensity P _s1,i according to the interference echo data (consistent with the receiving performance calibration process);

Step S3.33: ensure that the parameter settings of the calibration system when calibrating the i+1th measured radar 12 are consistent with the parameter settings of the calibration system when calibrating the i-th measured radar 11, and the azimuth, pitch, radial distance between the calibration source and the i+1th measured radar 12 and the calibration source and the i-th measured radar 11 are consistent, that is, the spatial relative position between the i+1th measured radar 12 and the calibration source is consistent with the spatial relative position between the i-th measured radar 11 and the calibration source;

Step S3.34: the i+1th measured radar 12 transmits a signal to the calibration source, the calibration source receives the signal transmitted by the i+1th measured radar 12, and calculates the signal power P _s2,i+1 , and saves the signal power P _s2,i+1 and the spatial relative position between the i+1th measured radar 12 and the calibration source;

Step S3.35: the calibration source transmits an interference signal to the i+1th radar under test 12, the i+1th radar under test 12 receives the interference signal transmitted by the calibration source and generates interference echo data, and controls the display terminal to calculate the interference echo intensity P _s1,i+1 according to the interference echo data;

Step S3.36: Calculate the intensity detection difference between the i-th measured radar 11 and the i+1-th measured radar 12 according to the signal power P _{s2 ,i} , the signal power P _{s2 ,i+1 , the interference echo intensity P s1,} i and the interference echo intensity P s1,i+1;

Step S3.37: Determine the consistency of the intensity detection between the i-th radar 11 and the (i+1)-th radar 12 according to the intensity detection difference.

In a specific embodiment of the present invention, the specific calculation formula of the intensity detection difference is:

ΔP＝(P _s2,i -P _s2,i+1 ) + (P _s1,i -P _s1,i+1 ) (8)

Wherein, ΔP represents the intensity detection difference. When the intensity detection difference ΔP is less than or equal to the set threshold, it indicates that the intensity detection of the i-th measured radar 11 and the i+1-th measured radar 12 are consistent. Through this calibration method, the intensity detection difference of multiple radars can be detected, which is of great significance for multi-radar network detection to ensure the consistency of intensity detection of each radar.

Example 2

As shown in Figure 1, a phased array weather radar calibration system provided by an embodiment of the present invention includes a drone, a drone remote controller 3, a calibration source and a control display terminal 4. The calibration source is mounted on the drone and connected to the control module of the drone. The control module of the drone communicates with the drone remote controller 3 using wireless communication. The drone remote controller 3 is connected to the control display terminal 4, the control display terminal 4 is connected to a radar data server 5, and the radar data server 5 is connected to the radar 1 under test.

The human-machine remote controller is used to control the UAV 2 equipped with the calibration source to fly to a predetermined spatial position by wireless communication; and receive the calibration control instructions sent by the control display terminal 4, and control the calibration source to calibrate the radar 1 under test at a predetermined spatial position through the control module of the UAV by wireless communication according to the calibration control instructions.

The operator controls the drone remote controller 3 to make the drone 2 equipped with the calibration source fly to a predetermined spatial position, or controls the display terminal 4 to calculate the spatial position of the calibration source according to the demand, generates a flight trajectory instruction according to the spatial position of the calibration source, and controls the drone to fly to the predetermined spatial position through the drone remote controller 3. This method is flexible to operate, the flight trajectory is controllable, the flight attitude is stable, and it can hover in the air for a long time with high position accuracy during hovering.

The radar 1 under test and the drone both have their own positioning modules. According to the positions of the radar 1 under test and the drone, it can be determined whether the antenna of the calibration source and the antenna of the radar 1 under test meet the far-field condition. At a predetermined spatial position, the antenna of the calibration source and the antenna of the radar 1 under test meet the far-field condition (as shown in formula (1) of embodiment 1); on the basis of meeting the far-field condition, the main beam of the antenna of the radar 1 under test must be ensured to be coaxial with the main beam radiation direction of the calibration source antenna and the axis is aligned, that is, the theoretical calibration radiation link model, as shown in FIG2. In a specific embodiment of the present invention, the main beam 6 of the calibration source is aligned with the main beam 7 of the radar under test by adjusting the antenna elevation angles of the calibration source and the radar 1 under test. As shown in FIG3, the antenna elevation angle α of the radar 1 under test is known, and the antenna elevation angle β of the calibration source is adjusted so that the antenna elevation angle β of the calibration source is equal to the antenna elevation angle α of the radar 1 under test, thereby making the antenna of the calibration source parallel to the antenna of the radar 1 under test, that is, the main beam 6 of the calibration source is aligned with the main beam 7 of the radar under test. The antenna elevation angle of the calibration source can be adjusted manually. Before calibration, the antenna elevation angle of the calibration source is adjusted to be consistent with the antenna elevation angle of the radar 1 under test.

The calibration source is used to calibrate the radar 1 under test at a predetermined spatial position under the control of the control module; the control display terminal 4 is used to send calibration control instructions to the UAV remote controller 3, and receive and process the data during the calibration process to obtain the calibration result.

In a specific embodiment of the present invention, the calibration of the radar 1 under test by the calibration source at a predetermined spatial position includes the calibration of the transmit power of the radar 1 under test, the calibration of the receiving performance of the radar 1 under test, and the calibration of the consistency of the intensity detection of multiple radars. The specific implementation process of calibrating the transmit power of the radar 1 under test by using the calibration system can be referred to steps S3.11 to S3.14 in Example 1; the specific implementation process of calibrating the receiving performance of the radar 1 under test by using the calibration system can be referred to steps S3.21 to S3.23 in Example 1; the specific implementation process of calibrating the consistency of the intensity detection of multiple radars by using the calibration system can be referred to steps S3.31 to S3.37 in Example 1.

In a specific embodiment of the present invention, as shown in Figure 5, the calibration source includes a signal generating unit, a signal processing unit, a transceiver switching module and an antenna; the signal generating unit and the signal processing unit are connected to the control module of the drone, and the signal generating unit and the signal processing unit are also connected to the transceiver switching module, and the transceiver switching module is connected to the antenna.

The signal generating unit is used to generate an interference signal under the control of the control module; the signal processing unit is used to process the signal received by the antenna to obtain the signal power, and transmit the signal power to the control display terminal 4 through the control module and the UAV remote controller 3 in sequence; the transceiver switching module is used to switch the transmission and reception modes; the antenna is used to radiate the interference signal generated by the signal generating unit outward, and receive the signal transmitted outward by the radar 1 under test.

In this embodiment, the signal processing unit includes a radio frequency detector and a converter. The radio frequency detector detects a signal power analog value from a signal received by an antenna of a calibration source, and the AD converter converts the signal power analog value into a signal power digital value. The signal generating unit includes a DDS (Direct Digital Synthesizer), a frequency synthesizer module, a frequency converter, and an amplifying and filtering module. The DDS and the frequency synthesizer module are connected to the frequency converter, and the frequency converter is connected to the amplifying and filtering module.

In this embodiment, the calibration source further includes a protective cover, and the signal generating unit, the signal processing unit and the transceiver switching module are arranged in the protective cover. The control display terminal 4 and the drone remote controller 3 are connected to each other by RS422 communication.

Considering that the main working mode of the calibration system is to operate in the air and needs to be mounted on a drone, the weight of the calibration system and its overall coordination with the drone are particularly important. It is necessary to consider lightweight, low wind resistance and anti-shake performance design, place the control and display terminal 4 that mainly performs data processing on the ground, reduce the weight of the calibration source, and the weight of the entire calibration source is less than 5kg.

What is disclosed above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of changes or modifications within the technical scope disclosed in the present invention, which should be included in the protection scope of the present invention.

Claims (9)

1. A phased array weather radar calibration method, characterized in that the calibration method comprises the following steps: Before calibration, the UAV remote controller controls the UAV equipped with the calibration source to fly to a predetermined spatial position by wireless communication; at the predetermined spatial position, the antenna of the calibration source and the antenna of the radar under test meet the far-field condition, and the main beam of the calibration source is aligned with the main beam of the radar under test; During calibration, the control display terminal sends a calibration control instruction to the drone remote controller, and the drone remote controller transmits the calibration control instruction to the control module of the drone in a wireless communication manner; Under the control of the control module, the calibration source calibrates the radar under test at a predetermined spatial position; The calibration source transmits the data in the calibration process to the control and display terminal in sequence through the control module of the drone and the drone remote controller; or the radar under test transmits the data in the calibration process to the control and display terminal; The control display terminal processes the received data in the calibration process to obtain a calibration result; The calibration of the radar under test by the calibration source at a predetermined spatial position includes a multi-radar intensity detection consistency calibration, and the specific implementation process is as follows: For the i-th measured radar, the i-th measured radar transmits a signal to the calibration source, the calibration source receives the signal transmitted by the i-th measured radar, calculates the signal power P _s2,i , and saves the signal power P _s2,i and the spatial relative position between the i-th measured radar and the calibration source; The calibration source transmits an interference signal to the i-th radar under test, the i-th radar under test receives the interference signal transmitted by the calibration source and generates interference echo data, and the control and display terminal calculates the interference echo intensity P _s1,i according to the interference echo data; For the i+1th measured radar, adjusting the spatial position of the calibration source or the i+1th measured radar so that the spatial relative position between the i+1th measured radar and the calibration source is consistent with the spatial relative position between the i-th measured radar and the calibration source, and the parameter setting of the calibration source remains unchanged; The i+1th radar under test transmits a signal to the calibration source, the calibration source receives the signal transmitted by the i+1th radar under test, calculates the signal power P _s2,i+1 , and saves the signal power P _s2,i+1 and the spatial relative position between the i+1th radar under test and the calibration source; The calibration source transmits an interference signal to the i+1th radar under test, the i+1th radar under test receives the interference signal transmitted by the calibration source and generates interference echo data, and the control and display terminal calculates the interference echo intensity P _s1,i+1 according to the interference echo data; Calculating the intensity detection difference between the i-th measured radar and the i+1-th measured radar according to the signal power P _s2,i , the signal power P _s2,i+1 , the interference echo intensity P _{s1, i} and the interference echo intensity P s1,i+1; The intensity detection consistency between the i-th measured radar and the (i+1)-th measured radar is determined according to the intensity detection difference. 2. The phased array weather radar calibration method according to claim 1, characterized in that the specific implementation process of aligning the main beam of the calibration source with the main beam of the radar under test is: The antenna elevation angles of the calibration source and the radar under test are adjusted so that the antenna of the calibration source is parallel to the antenna of the radar under test, so that the main beam of the calibration source is aligned with the main beam of the radar under test. 3. The phased array weather radar calibration method according to claim 1, characterized in that the calibration source calibrates the radar under test at a predetermined spatial position, and further comprises the calibration of the transmit power of the radar under test and the calibration of the receiving performance of the radar under test; The specific implementation process of the transmit power calibration of the radar under test is: The antenna of the radar under test transmits signals outward; The antenna of the calibration source receives the signal transmitted by the radar under test, and the signal processing unit of the calibration source processes the signal received by its antenna to obtain the signal power; The signal power output by the calibration source is transmitted to the control display terminal via the control module and the UAV remote controller in sequence; The control display terminal calculates the transmission power of the radar under test according to the signal power output by the calibration source; The specific implementation process of the receiving performance calibration of the radar under test is: The signal generating unit of the calibration source generates an interference signal, and the interference signal is radiated outward through the antenna of the calibration source; The antenna of the radar under test receives the interference signal, and the radar under test generates interference echo data according to the interference signal; The interference echo data is transmitted to a control and display terminal, and the control and display terminal calculates reflectivity according to the interference echo data to achieve calibration of receiving performance of the radar under test. 4. The phased array weather radar calibration method according to claim 3 is characterized in that the specific calculation formula for calculating the transmission power of the measured radar according to the signal power output by the calibration source is: 10lgP _t1 ＝10lgP _s2 －G _t1 －G _r2 ＋10lgF＋10lgR＋32.4; Wherein, _Pt1 represents the transmitting power of the radar under test, _Ps2 represents the signal power output by the calibration source, _Gt1 represents the antenna transmitting gain of the radar under test, _Gr2 represents the antenna receiving gain of the calibration source, F represents the signal frequency transmitted by the radar under test, and R represents the distance between the calibration source and the radar under test. 5. The phased array weather radar calibration method according to claim 3 is characterized in that the reflectivity is calculated according to the interference echo data, and the specific implementation process is: Obtaining interference echo intensity according to the interference echo data; The interference signal power received by the radar under test is calculated according to the interference echo intensity. The calculation formula of the interference signal power is: P _r1 =Ar*P _s1 +Br; Wherein, P _r1 represents the interference signal power received by the radar under test, P _s1 represents the interference echo intensity received by the radar under test, and Ar and Br represent the coefficients to be determined respectively; Adjust the distance between the calibration source and the radar under test, and calculate the interference echo intensity and interference signal power at another distance in the same way; Determine the coefficients Ar and Br according to the interference echo intensity and interference signal power at two distances; Combining the calculation formula of interference signal power and radar equation, we can get the expression of radar reflectivity factor, which is: ; Where Z represents the radar reflectivity factor, λ represents the wavelength of the transmitted signal of the radar under test, R represents the distance between the calibration source and the radar under test, _Pt1 represents the transmitted power of the radar under test, and c represents the speed of light. represents the pulse width of the transmitted signal of the radar under test, G _t1 represents the antenna transmitting gain of the radar under test, G _r1 represents the antenna receiving gain of the radar under test, θ represents the antenna azimuth beamwidth of the radar under test, φ represents the antenna elevation beamwidth of the radar under test, and K represents the water drop dielectric constant; Based on the calculation formula of interference signal power, take 20 times the logarithm on both sides of the equal sign of the expression of radar reflectivity factor to obtain radar reflectivity. The specific formula is: dBZ＝factor＋20logR＋Ar*P _s1 +Br; ; Wherein, dBZ represents radar reflectivity and factor represents calibration parameter. 6. The phased array weather radar calibration method according to claim 1, characterized in that the specific calculation formula of the intensity detection difference is: ΔP=(P _s2,i -P _s2,i+1 ) + (P _s1,i -P _s1,i+1 ); Wherein, ΔP represents the intensity detection difference. 7. A phased array weather radar calibration system, characterized in that: the calibration system comprises an unmanned aerial vehicle, an unmanned aerial vehicle remote controller, a calibration source and a control display terminal, the calibration source is mounted on the unmanned aerial vehicle and connected to a control module of the unmanned aerial vehicle, and the unmanned aerial vehicle remote controller is connected to the control display terminal; The UAV remote controller is used to control the UAV mounted with the calibration source to fly to a predetermined spatial position by wireless communication, at which the antenna of the calibration source and the antenna of the radar under test meet the far-field condition, and the main beam of the calibration source is aligned with the main beam of the radar under test; and receive the calibration control instruction sent by the control display terminal, and control the calibration source to calibrate the radar under test at the predetermined spatial position through the control module of the UAV by wireless communication according to the calibration control instruction; The calibration source is used to calibrate the radar under test at a predetermined spatial position under the control of the control module; The control display terminal is used to send calibration control instructions to the UAV remote controller; and receive and process the data in the calibration process to obtain the calibration result; The calibration of the radar under test by the calibration source at a predetermined spatial position includes a multi-radar intensity detection consistency calibration, and the specific implementation process is as follows: For the i-th measured radar, the i-th measured radar transmits a signal to the calibration source, the calibration source receives the signal transmitted by the i-th measured radar, calculates the signal power P _s2,i , and saves the signal power P _s2,i and the spatial relative position between the i-th measured radar and the calibration source; The calibration source transmits an interference signal to the i-th radar under test, the i-th radar under test receives the interference signal transmitted by the calibration source and generates interference echo data, and the control and display terminal calculates the interference echo intensity P _s1,i according to the interference echo data; For the i+1th measured radar, adjusting the spatial position of the calibration source or the i+1th measured radar so that the spatial relative position between the i+1th measured radar and the calibration source is consistent with the spatial relative position between the i-th measured radar and the calibration source, and the parameter setting of the calibration source remains unchanged; The i+1th radar under test transmits a signal to the calibration source, the calibration source receives the signal transmitted by the i+1th radar under test, calculates the signal power P _s2,i+1 , and saves the signal power P _s2,i+1 and the spatial relative position between the i+1th radar under test and the calibration source; The calibration source transmits an interference signal to the i+1th radar under test, the i+1th radar under test receives the interference signal transmitted by the calibration source and generates interference echo data, and the control and display terminal calculates the interference echo intensity P _s1,i+1 according to the interference echo data; Calculating the intensity detection difference between the i-th measured radar and the i+1-th measured radar according to the signal power P _s2,i , the signal power P _s2,i+1 , the interference echo intensity P _{s1, i} and the interference echo intensity P s1,i+1; The intensity detection consistency between the i-th measured radar and the (i+1)-th measured radar is determined according to the intensity detection difference. 8. The phased array weather radar calibration system according to claim 7, characterized in that: the calibration source comprises a signal generating unit, a signal processing unit, a transceiver switching module and an antenna; the signal generating unit and the signal processing unit are connected to the control module of the UAV, the signal generating unit and the signal processing unit are also connected to the transceiver switching module, and the transceiver switching module is connected to the antenna; The signal generating unit is used to generate an interference signal under the control of the control module; The signal processing unit is used to process the signal received by the antenna to obtain signal power, and transmit the signal power to the control and display terminal through the control module and the drone remote controller in sequence; The transmitting and receiving switching module is used to switch between the transmitting and receiving modes; The antenna is used to radiate the interference signal generated by the signal generating unit outwardly; and to receive the signal emitted outwardly by the radar under test. 9. The phased array weather radar calibration system according to claim 7 or 8, characterized in that the control display terminal and the UAV remote controller are connected in communication using RS422 communication mode.