CN113109771A - Calibration device for calibrator and weather radar echo intensity true value calibration method - Google Patents

Calibration device for calibrator and weather radar echo intensity true value calibration method Download PDF

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CN113109771A
CN113109771A CN202110293161.4A CN202110293161A CN113109771A CN 113109771 A CN113109771 A CN 113109771A CN 202110293161 A CN202110293161 A CN 202110293161A CN 113109771 A CN113109771 A CN 113109771A
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power
reflector
antenna
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radar
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CN113109771B (en
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王箫鹏
陈玉宝
刘洁
步志超
韩旭
邵楠
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CMA Meteorological Observation Centre
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4004—Means for monitoring or calibrating of parts of a radar system
    • G01S7/4008—Means for monitoring or calibrating of parts of a radar system of transmitters
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4004—Means for monitoring or calibrating of parts of a radar system
    • G01S7/4021—Means for monitoring or calibrating of parts of a radar system of receivers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/40—Means for monitoring or calibrating
    • G01S7/4052—Means for monitoring or calibrating by simulation of echoes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01W—METEOROLOGY
    • G01W1/00—Meteorology
    • G01W1/18—Testing or calibrating meteorological apparatus
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A90/00—Technologies having an indirect contribution to adaptation to climate change
    • Y02A90/10—Information and communication technologies [ICT] supporting adaptation to climate change, e.g. for weather forecasting or climate simulation

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Abstract

The invention provides a calibration device for a calibration instrument and a method for calibrating a true value of echo intensity of a weather radar, and relates to the technical field of weather radar calibration. Based on the calibration device, the embodiment of the invention provides the idea that the calibration of the echo intensity true value of the weather radar is carried out by depending on the simulated target true value of the calibrator, the simulated target true value reference of the calibrator is calibrated by depending on the calibration device, the calibration device calibrates the simulated target transmitting power and the echo intensity true value reference of the calibrator by using the objective reflection true value characteristics of the metal ball and the corner reflector and depending on the high-precision measurement performance of the calibration device on the power density of the spatial radiation signal, and further calibrates the echo intensity true value of the weather radar.

Description

Calibration device for calibrator and weather radar echo intensity true value calibration method
Technical Field
The invention relates to the technical field of weather radar calibration, in particular to a calibration device for a calibrator and a method for calibrating a true value of echo intensity of a weather radar.
Background
More than 230 weather radars (CINRAD) of the new generation are on-line in the whole country, and play an indispensable role in national fine weather forecast service and disastrous weather monitoring and early warning. Accuracy and consistency of networking radar data directly influence radar application and benefit exertion, and especially development of a digital forecasting mode puts higher requirements on data assimilation of the networking radar. The accuracy and reliability of weather radar detection data are improved, the quality of national networking weather radar observation data is ensured, and the key points are that a perfect weather radar calibration service is established, and a technical specification and a platform for supporting the calibration service are provided.
Radar intensity measurement, speed measurement, coordinate measurement (distance, azimuth angle and pitch angle), spectrum width measurement, differential reflectivity measurement and differential phase shift measurement are main system parameters of the weather radar and are main marks for measuring the quality of the radar. The system indexes of radar antenna gain, transmitting power, receiving sensitivity, receiving dynamic, clutter rejection ratio, phase noise and the like are basic guarantees of the system indexes.
Because radar products lack a system parameter measuring means which can be conveniently implemented, military radars measure and identify radar system parameters and subsystem parameters through a target range test when the products are shaped, and the performance of the radars in the production and use stage is evaluated by replacing the system parameter test with the subsystem parameter test after the products are shaped, so that the problem that the system parameters exceed the standard is continuously found in the use of troops. The weather radar has no target range test link, and a subsystem index and a part of system indexes are determined by mature model experience to indirectly test the alternative method, so that the problem of standard exceeding of the system indexes can also exist in operation and maintenance, and the calibration instrument undertakes the calibration tasks of the dual-polarization weather radar system indexes and the subsystem indexes. But the calibration instrument needs to be calibrated periodically every year to ensure the calibration effect of the weather radar.
The calibration of the echo intensity truth value of the weather radar is the core of data quality control of the weather radar, and in the calibration process of the echo intensity truth value of the weather radar, a current calibration instrument has no calibration means for a simulated target signal transmitted to the weather radar, so that the calibration of the measurement consistency between the radar and the radar can only be ensured, and the accuracy of a measurement result cannot be ensured.
Disclosure of Invention
The embodiment of the invention provides a calibration device for a calibrator and a method for calibrating a true value of echo intensity of a weather radar.
In order to solve the above problem, an embodiment of the present invention discloses a calibration apparatus for a calibration instrument, including:
the polarized transmitting antenna and the polarized receiving antenna are respectively connected with the main machine, and horn mouths of the polarized transmitting antenna and the polarized receiving antenna are positioned on the same horizontal plane;
the polarized receiving antenna comprises a vertical polarized receiving antenna and a horizontal polarized receiving antenna;
the polarized transmitting antenna is arranged on the host, and the polarization direction of the polarized transmitting antenna is arranged at an angle of 45 degrees relative to the horizontal plane;
the vertical polarization receiving antenna is arranged on the host, and the polarization direction of the vertical polarization receiving antenna is vertical to the horizontal plane;
the horizontal polarization receiving antenna is arranged on the host, and the polarization direction of the horizontal polarization receiving antenna is parallel to the horizontal plane.
In an embodiment of the present invention, the host includes:
the device comprises a transmitter, an H receiver, a V receiver, a frequency synthesizer, an H signal processing module, a V signal processing module, a data processing module and a display control terminal;
the transmitter is respectively connected with the frequency synthesizer and the polarized transmitting antenna;
the H receiver is respectively connected with the frequency synthesizer, the vertical polarization receiving antenna and the H signal processing module;
the V receiver is respectively connected with the frequency synthesizer, the horizontal polarization receiving antenna and the V signal processing module;
the data processing module is respectively connected with the H signal processing module, the V signal processing module and the display control terminal.
In an embodiment of the present invention, the frequency synthesizer includes a crystal oscillator, a first power divider, a first phase-locked loop, a second phase-locked loop, a first signal generator DDS, and a second DDS;
the first power divider is connected with the crystal oscillator, the first phase-locked loop, the second DDS, the H signal processing module and the V signal processing module respectively;
the first phase-locked loop is connected with the transmitter sequentially through a first amplifier, a first power divider and a first frequency mixer, the first frequency mixer is connected with the first DDS through a first low-pass filter, and the first power divider is connected with the H receiver and the V receiver respectively;
the second phase-locked loop is connected with the second power divider;
and the second DDS is respectively connected with the H receiver and the V receiver sequentially through a second low-pass filter, a second amplifier and a third power divider.
In an embodiment of the present invention, the H receiver includes:
the second mixer, the third low-pass filter, the third amplifier, the third mixer, the fourth low-pass filter and the first intermediate frequency amplifier are connected in sequence;
the second mixer is connected with the vertical polarization receiving antenna and the first power divider respectively;
the third mixer is connected with the second amplifier;
the first intermediate frequency amplifier is connected with the H signal processing module.
In order to solve the above problem, the embodiment of the present invention further discloses a method for calibrating the strength of a weather radar comprehensive calibrator, wherein the method comprises:
calibrating the gain power product of a transmitting antenna of a transmitting channel of the calibrating device according to the embodiment of the invention, and calibrating the performance of a receiving channel of a calibrator by transmitting a reference signal through the transmitting channel of the calibrating device after calibration;
calibrating the power density measurement performance of the space radiation signal by the receiving channel of the calibrating device so as to calibrate the performance of the transmitting channel of the calibrator; the power density measurement performance comprises a power density measurement reference value and a power density measurement dynamic range, the power density measurement reference value is calibrated based on the standard reflection performance of a reflector, the power density measurement dynamic range controls the emission power of a calibration device, and then the emission power is sent to a standard gain loudspeaker, so that the standard gain loudspeaker radiates to a receiving antenna of the calibration device for calibration;
establishing a reflector measuring system, wherein the bell mouths of a polarized transmitting antenna and a polarized receiving antenna of the calibrating device are aligned to a far-field reflector; the calibration device measures the radar cross section of the reflector according to a pulse radar equation, measures the echo power of the reflector at different distances according to a weather radar equation, and establishes a distance-radar cross section-echo power parameter table;
the calibration device calculates the reflectivity coefficient of the reflector in the weather radar according to the radar sectional area of the reflector, and converts the distance-radar sectional area-echo power parameter table into a distance-reflectivity coefficient-echo power parameter table; wherein the reflectivity coefficient range of the reflector is matched with the weather radar measurement dynamic range;
establishing a simulated target transmitting power calibration system, wherein in the simulated target transmitting power calibration system, the bell mouths of a polarized transmitting antenna and a polarized receiving antenna of the calibration device are both aligned to an antenna of a far-field calibration instrument, wherein the simulated target transmitting power of the calibration instrument is adjusted according to the distance-reflectivity coefficient-echo power parameter table, so that the echo power corresponding to the simulated target transmitting power received by the calibration device under a specific distance is equal to the echo power of the reflector received by the calibration device under the corresponding reflectivity coefficient, and the simulated target transmitting power is recorded to obtain the distance-reflectivity coefficient-simulated target transmitting power parameter table;
and calibrating the true value of the echo intensity of the weather radar by using the calibration instrument after the transmitting channel and the receiving channel are calibrated according to the distance-reflectivity coefficient-simulated target transmitting power parameter table.
In an embodiment of the present invention, calibrating a transmit antenna gain power product of a transmit channel of a calibration apparatus includes the following steps:
setting a standard gain horn antenna and a power meter connected with the standard gain horn antenna in a far field, and aligning a horn mouth of a polarized transmitting antenna of the calibration device with the standard gain horn antenna;
the transmitting power of the calibration device is PjBy said polarized radiation of the antenna, the antenna gain Gj(ii) a The distance between the standard gain horn antenna and the horn mouth of the polarized transmitting antenna is RcThe space radiation power density of the standard gain horn antenna is DjThe aperture area of the standard gain horn antenna is AcThe power meter measures power as Pcj；
The power density of the space radiation signal received by the standard gain horn antenna is as follows:
Figure BDA0002983209270000041
the power meter measures the power as follows:
Figure BDA0002983209270000042
the gain power product of the transmitting antenna of the transmitting channel of the calibration device is as follows:
Figure BDA0002983209270000043
in an embodiment of the present invention, calibrating the power density measurement performance of the spatial radiation signal by using the receiving channel of the calibration apparatus includes the following steps:
radiating a signal to a reflector through a transmitting channel of the calibration device, wherein the spatial power density at the reflector is:
Figure BDA0002983209270000051
(4) in the formula: ptjGtjThe gain power product of the transmitting antenna of the transmitting channel of the calibrating device is calibrated; rjThe distance between the center of a reflector and a receiving antenna bell mouth of the calibration device is defined, the radiation signal of the calibration device is received, excited and reflected on the surface of the reflector, part of the reflected signal enters a receiving antenna of the calibration device, the size of the reflected signal is described by the cross section area sigma of a reflector radar, and the echo power density reflected by the reflector on the bell mouth surface of the receiving antenna of the calibration device is as follows:
Figure BDA0002983209270000052
in an embodiment of the present invention, a reflector measurement system is established, in which the bell mouths of the polarized transmitting antenna and the polarized receiving antenna of the calibration device are both aligned with the far-field reflector; the calibration device measures the radar cross section of the reflector according to a pulse radar equation and measures the echo power of the reflector at different distances according to a weather radar equation, and the calibration device comprises the following steps:
selecting the ground levelA flat open field, three support rods and a pull rope are used for suspending a reflector, the reflector is erected above the bell mouths of a polarized transmitting antenna and a polarized receiving antenna of the calibration device, and the distance between the bell mouth and a far field reflector is
Figure BDA0002983209270000053
D is the caliber size of the bell mouth, and lambda is the radar working wavelength;
the radar cross section of the reflector is measured according to the pulse radar equation:
Figure BDA0002983209270000054
in the above formula, PrReceiving echo power for radar, PtFor radar emission of peak power, GtFor radar transmitting antenna gain, GrGain of radar transmitting antenna, FtFor the calibrator transmitting antenna to target radar pattern factor, FrReceive antenna pattern factor for target radar to calibrator, L is system loss, LaIn order to reduce the atmospheric transmission loss, sigma is the radar sectional area of the reflector, tau is the radar emission pulse width, and R is the distance between the radar and the reflector;
setting a pulse radar constant:
Figure BDA0002983209270000055
σ＝CpPrR4 (8)；
after the radar sectional area of the reflector is measured, the distance R from the center of the reflector to the bell mouth is measured through a measuring tool rulerjMeasuring the echo power P of the reflector by means of said calibration devicerj。
In an embodiment of the present invention, the calculating, by the calibration device, a reflectivity coefficient of the reflector in the weather radar according to a radar cross-sectional area of the reflector includes:
the weather radar equation is:
Figure BDA0002983209270000061
in the formula: | K ∞2Is constant, Z is the reflectance coefficient; wherein:
Figure BDA0002983209270000062
wherein m is complex refractive index, centimeter band, temperature is 0-20 deg.C, when the particles are in water state, | K2Approximately equal to 0.93, | K shadingin ice state2≈0.2；
Figure BDA0002983209270000063
Where theta is the radar azimuth beam width,
Figure BDA0002983209270000066
pitch angle beam width, c is speed of light;
setting weather radar constants:
Figure BDA0002983209270000064
and in combination with the above formula, the reflectivity coefficient of the reflector in the weather radar is calculated as follows:
Figure BDA0002983209270000065
in an embodiment of the present invention, a calibration system for simulated target transmitting power is established, in which bellmouths of a polarized transmitting antenna and a polarized receiving antenna of the calibration device are both aligned to an antenna of a far-field calibration instrument, wherein the simulated target transmitting power of the calibration instrument is adjusted according to the parameter table of distance-reflectance coefficient-echo power, so that the simulated target transmitting power received by the calibration device is equal to the echo power of the reflector, and the parameter table of distance-reflectance coefficient-simulated target transmitting power is recorded and obtained, including the following steps:
selecting a field open space with flat ground, suspending a calibration instrument antenna by using three supporting rods and a pull rope, erecting the calibration instrument antenna above horn mouths of a polarization transmitting antenna and a polarization receiving antenna of the calibration device, and connecting the calibration instrument antenna to a calibration instrument through a cable;
will be at a distance RjAt the received echo power P of the reflectorrjConverted to at a distance RbAdjusting the simulated target transmitting power of the simulated target signal to make the echo power of the calibrator PrbCalibrating the simulated target transmitting power P corresponding to the current radar reflection sectional area sigma of the reflectortb：
When the erection position of the calibration instrument is different from the position of the reflector, the calibration instrument and the calibration device are aligned with each other and converted by the following formula:
Figure BDA0002983209270000071
Figure BDA0002983209270000072
in the formula: prjIs the echo power of the reflector, RjIs the distance between the reflector and the calibration device;
Figure BDA0002983209270000073
in the formula: prbFor calibrating the echo power of the instrument, RbThe distance between the calibrator and the calibrating device is obtained;
Figure BDA0002983209270000074
adjusting the simulated target transmit power Ptb＝KbPrbMaking the echo power received by the calibration device be PrbRecording the simulated target transmit power P at that timetb；
On the basis, a distance-reflectivity coefficient-simulated target transmitting power parameter table is established according to the following formula:
Figure BDA0002983209270000075
the embodiment of the invention has the following advantages:
the calibration device comprises a host, wherein a polarized transmitting antenna, a vertical polarized receiving antenna and a horizontal polarized receiving antenna are arranged on the host, and are arranged on the top end surface of the host side by side, and the polarization direction of the polarized transmitting antenna is arranged at an angle of 45 degrees relative to the horizontal plane, so that a reference signal with the horizontal polarization equal to the vertical polarization in amplitude and the phase difference of 0 degree can be transmitted to a calibrator, and the calibration of the power density measurement performance of a space radiation signal by two polarized receiving channels (a vertical polarized receiving channel and a horizontal polarized receiving channel) of the calibrator is realized; the polarization direction of the vertical polarization receiving antenna is perpendicular to the horizontal plane, so that the vertical polarization component in the simulated target signal transmitted by the calibrator can be effectively received, and the polarization direction of the horizontal polarization receiving antenna is parallel to the horizontal plane, so that the horizontal polarization component in the simulated target signal transmitted by the calibrator can be effectively received, and the calibration of the dynamic state and the precision of the simulated target transmitting power of the transmitting channel of the calibrator is further realized;
the embodiment of the invention provides a concept that the calibration of the echo intensity true value of the weather radar is carried out by depending on the simulated target true value of the calibrator, the simulated target true value of the calibrator is calibrated by depending on the calibration device, the calibration device utilizes the objective reflection true value characteristics of the metal ball and the corner reflector and depends on the high-precision measurement performance of the calibration device on the power density of the spatial radiation signal to calibrate the simulated target transmitting power and the echo intensity true value reference of the calibrator and further calibrate the echo intensity true value of the weather radar.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic three-dimensional structure of a calibration device according to the present invention;
FIG. 2 is a front view of the alignment device of FIG. 1 in accordance with the present invention;
FIG. 3 is a side view of the alignment device of FIG. 1 in accordance with the present invention;
FIG. 4 is a block diagram of the system components of the calibration device of the present invention;
FIG. 5 is a schematic block circuit diagram of the calibration apparatus of the present invention;
FIG. 6 is a flowchart illustrating steps of a method for calibrating a true value of a weather radar echo intensity according to the present invention;
FIG. 7 is a schematic diagram illustrating the calibration of the gain-power product of the transmitting antenna of the polarized transmitting antenna of the calibration apparatus according to the present invention;
FIG. 8 is a schematic diagram illustrating the calibration of the power density measurement performance of a spatial radiation signal using the receiver channel of the calibration apparatus according to the present invention;
FIG. 9 is a schematic diagram of the metal ball reflector measurement system of the present invention;
fig. 10 is a schematic diagram of a simulated target transmit power calibration system of the present invention.
Description of reference numerals:
1-a host; 2-polarized transmitting antenna; 3-a vertically polarized receiving antenna; 4-horizontally polarized receiving antenna; 5-an azimuth turntable; 6-a base; 601-a power interface; 602-a switch; 603-a network port; 7-an antenna radio frequency interface; 8-chassis.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Referring to fig. 1 to 3, there are shown schematic structural diagrams of a calibration device for a calibration instrument according to the present invention, which can at least solve the technical problems of the present invention, and the calibration device may include:
the device comprises a main machine 1, a polarized transmitting antenna 2 and a polarized receiving antenna which are respectively connected with the main machine 1, wherein horn mouths of the polarized transmitting antenna 2 and the polarized receiving antenna are positioned on the same horizontal plane;
the polarized receiving antenna comprises a vertical polarized receiving antenna 3 and a horizontal polarized receiving antenna 4;
the polarized transmitting antenna 2 is arranged on the host, and the polarization direction of the polarized transmitting antenna 2 is arranged at an angle of 45 degrees relative to the horizontal plane;
the vertical polarization receiving antenna 3 is arranged on the host, and the polarization direction of the vertical polarization receiving antenna 3 is vertical to the horizontal plane;
the horizontal polarization receiving antenna 4 is arranged on the main machine, and the polarization direction of the horizontal polarization receiving antenna 4 is arranged in parallel to the horizontal plane.
As shown in fig. 1 and fig. 2, the polarized transmitting antenna 2, the vertical polarized receiving antenna 3, and the horizontal polarized receiving antenna 4 of the calibration apparatus of the present invention are arranged side by side on the top end surface of the main unit 1, and since the polarization direction of the polarized transmitting antenna 2 is arranged at an angle of 45 ° with respect to the horizontal plane, the reference signal with the horizontal polarization equal to the vertical polarization in amplitude and the phase difference of 0 ° can be transmitted to the calibrator, so as to calibrate the power density measurement performance of the spatial radiation signal by the dual polarization receiving channels (the vertical polarization receiving channel and the horizontal polarization receiving channel) of the calibrator. In order to ensure that the polarization direction of the polarized transmitting antenna 2 is arranged at an angle of 45 ° with respect to the horizontal plane, in an embodiment of the present invention, the calibration apparatus further includes: a horizontal bubble (not shown) connected to the polarized transmitting antenna 2, which can be used to calibrate whether the polarization direction of the polarized transmitting antenna 2 is set at an angle of 45 ° with respect to the horizontal plane. For how the horizontal bubble is calibrated, reference may be made to the calibration principle of the existing horizontal bubble, which is not described herein in detail.
The polarization direction of the vertical polarization receiving antenna 3 of the calibration device is perpendicular to the horizontal plane, so that the vertical polarization component in the simulated target signal transmitted by the calibrator can be effectively received, and the polarization direction of the horizontal polarization receiving antenna 4 is parallel to the horizontal plane, so that the horizontal polarization component in the simulated target signal transmitted by the calibrator can be effectively received, and the dynamic and precision calibration of the simulated target transmission power of the transmission channel of the calibrator is further realized. The specific calibration method refers to the subsequent method, and is not described herein in detail.
As shown in fig. 1, the main unit 1 is provided with at least three antenna rf interfaces, and the polarized transmitting antenna 2, the vertically polarized receiving antenna 3, and the horizontally polarized receiving antenna 4 are connected to the three antenna rf interfaces 7 one by one through cables, so that a transmitting signal generated in the main unit 1 can transmit a transmitting signal to the polarized transmitting antenna 2 through one of the cables, and transmit a related receiving signal received by the vertically polarized receiving antenna 3 and the horizontally polarized receiving antenna 4 through the other two cables.
Further, with continued reference to fig. 1-3, the calibration device further includes: the azimuth turntable 5 is arranged at the lower end of the host 1 and connected with the host 1, and the azimuth turntable 5 is used for rotating by 0-360 degrees under the control of the host 1 so as to simulate azimuth scanning of a radar.
According to the invention, through the rotation of the azimuth turntable 5, the radar periodic scanning can be simulated, the testing functions of main subsystem indexes such as a far-field antenna directional pattern, antenna gain, transmitting power, frequency spectrum and the like of the calibrator are tested, the calibration functions of radar subsystem parameters of the calibrator are checked, the calibration performance indexes of the subsystem parameters are calibrated, and a technical guarantee is established for the data quality of the calibrator. The scanning directions of the polarized transmitting antenna 2, the vertically polarized receiving antenna 3 and the horizontally polarized receiving antenna 4 face to the same side, so that the signals can be simultaneously received and transmitted under the rotation of the azimuth turntable 5.
As shown in fig. 1 to 3, the calibration device further includes a base 6, where the base 6 is disposed below the orientation rotary table 5 and connected to the orientation rotary table 5; a power module is arranged in the base 6, and a power interface, a switch and a network port are arranged outside the base 6.
In the invention, the base 6 is cylindrical, the power supply module in the base 6 is an independent module, can be installed together with a lithium battery and a power supply control system and supplies power to each functional module in the host 1, and the power supply interface 601 on the outer peripheral wall of the base 6 can be connected with an external power supply to supply power to the power supply module; the switch 602 may comprise an activation switch 602, which controls the activation of the whole calibration apparatus, and the network port 603 may be connected to an external data display device or to a calibration instrument. In order to improve the stability of the whole calibration device during working, the bottom of the base is also provided with a chassis 8, and the surface area of the chassis 8 is larger than the lower end surface of the base.
In the present invention, referring to fig. 4, the host 1 includes: the device comprises a transmitter, an H receiver, a V receiver, a frequency synthesizer, an H signal processing module, a V signal processing module, a data processing module and a display control terminal; the transmitter is respectively connected with the frequency synthesis and the polarization transmitting antenna 2; the H receiver is respectively connected with the frequency synthesizer, the vertical polarization receiving antenna 3 and the H signal processing module; the V receiver is respectively connected with the frequency synthesizer, the horizontal polarization receiving antenna 4 and the V signal processing module; the data processing module is respectively connected with the H signal processing module, the V signal processing module and the display control terminal.
In an embodiment of the present invention, referring to fig. 5, the frequency synthesizer includes a crystal oscillator, a first power divider, a first phase-locked loop, a second phase-locked loop, a first signal generator DDS, and a second DDS; the first power divider is connected with the crystal oscillator, the first phase-locked loop, the second DDS, the H signal processing module and the V signal processing module respectively; the first phase-locked loop is connected with the transmitter through a first amplifier, a first power divider and a first frequency mixer in sequence, the first frequency mixer is connected with a first DDS through a first low-pass filter, and the first power divider is respectively connected with the H receiver and the V receiver; the second phase-locked loop is connected with the second power divider; and the second DDS is respectively connected with the H receiver and the V receiver through a second low-pass filter, a second amplifier and a third power divider in sequence.
With continued reference to fig. 5, in an embodiment of the present invention, the H receiver may include: the second mixer, the third low-pass filter, the third amplifier, the third mixer, the fourth low-pass filter and the first intermediate frequency amplifier are connected in sequence; the second frequency mixer is respectively connected with the vertical polarization receiving antenna 3 and the first power divider; the third mixer is connected with the second amplifier; the first intermediate frequency amplifier is connected with the H signal processing module.
With continued reference to fig. 5, in one embodiment of the invention, the V-receiver comprises: the fourth mixer, the fourth low-pass filter, the fourth amplifier, the fifth mixer, the fifth low-pass filter and the second intermediate frequency amplifier are connected in sequence; the fourth mixer is respectively connected with the horizontal polarization receiving antenna 4 and the first power divider; the fifth mixer is connected with the second amplifier; the second intermediate frequency amplifier is connected with the V signal processing module.
Each functional module in the host 1 is installed in a frame through a CPCI motherboard, and can be conveniently plugged and unplugged. When the frequency synthesizer is implemented, a DDS digital direct frequency synthesizer in the frequency synthesizer can generate 960Mhz linear frequency modulation or narrow pulse signals, the signals are mixed with 1 local oscillator signals generated by a first phase-locked loop to form transmitting radio frequency signals, transmitting signals of an S wave band, a C wave band and an X wave band can be formed by changing different local oscillator frequencies, the transmitter power is amplified and then output to a polarization transmitting antenna 2 arranged in a polarization direction at an angle of 45 degrees relative to a horizontal plane, and therefore reference signals with the same phase difference of 0 degree between horizontal polarization and vertical polarization amplitude can be transmitted to a calibration instrument. The calibrator receives a reference signal transmitted by the calibration device in a far field to generate a simulated target signal, the simulated target signal is transmitted to the calibration device through the variable polarization transmitting antenna 2 with the polarization direction of 45 degrees, so that the vertical polarization receiving antenna 3 and the horizontal polarization receiving antenna 4 of the calibration device receive a simulated target signal with equal amplitude and 0-degree phase difference, the vertical polarization component and the horizontal polarization component of the simulated target signal are subjected to frequency mixing, filtering and amplification twice, and then are correspondingly sent to the H signal processing module and the V signal processing module for detection, so that the amplitude and the phase of the vertical polarization receiving channel 3 and the amplitude and the phase of the horizontal polarization receiving channel 4 can be obtained, and then the amplitude and the phase are sent to the data processing module for Focus phase consistency calibration. Because the horizontal polarization and the vertical polarization of the analog target signal transmitted by the calibrator are equal in amplitude and have a phase difference of 0 degree, the invention compares the vertical polarization component and the horizontal polarization component of the same analog target signal output by the H receiver and the V receiver of the calibrating device through the data processing module, can realize amplitude-phase consistency calibration of a vertical polarization receiving channel and a horizontal polarization receiving channel of the calibrating device, and further ensures the effect of calibrating the analog target transmitting power of a transmitting channel of the calibrator.
The above explains the mechanical and modular structure of the calibration device, and then explains how to use the calibration device to calibrate the intensity of the calibrator, so as to solve the calibration problem of the true value of the echo intensity of the weather radar.
Referring to fig. 6, an embodiment of the present invention provides a flow chart of steps of a method for calibrating a true value of a weather radar echo intensity, where the method may include the following steps:
step S601, calibrating a transmit antenna gain power product of a transmit channel of the calibration apparatus according to the embodiment of the present invention, and transmitting a reference signal through the transmit channel of the calibrated calibration apparatus to calibrate performance of a receive channel of a calibrator.
The measurement and calibration of the gain power product of the transmitting antenna of the transmitting channel of the calibration device are the main basic work of the calibration device for the measurement and calibration of the receiving channel of the calibrator, the measurement performance of the receiving channel of the calibrator for the power density of space radiation signals is calibrated by transmitting reference signals through the calibration device, and the power of the reference signals is calibrated through the power meter.
Reference signal polarized transmitting antenna through calibration deviceRadiating into space, in space presenting the power product P of the polarized transmitting antenna of the calibration devicetjGtjThe power density radiated to the distance R is
Figure BDA0002983209270000121
The calibrator receiver receives the reference signal through an antenna, and the amplitude of the received signal is the aperture area of the receiving antenna multiplied by the spatial radiation power density.
And measuring the power density of the space radiation signal, wherein the larger the aperture area of the antenna is, the larger the amplitude of the received signal is. The calibration of the power density measurement performance of the receiving channel of the calibrator on the space radiation signal is realized by controlling the gain power product of the transmitting antenna of the transmitting channel of the calibration device, and the gain power product of the transmitting antenna of the transmitting channel of the calibration device is realized by controlling the transmitting power of the reference signal of the calibration device. Since the spatial measurements cannot obtain the transmit power alone, the transmit channel is calibrated by measuring the transmit antenna gain power product. Therefore, calibrating the gain and power product of the polarized transmitting antenna of the calibration device is one of the basic works of factory acceptance and annual audit calibration of the calibration device.
In specific implementation, the gain-power product of the transmitting antenna of the transmitting channel of the calibration device is calibrated by the standard horn antenna and the power meter, and the schematic diagram of the principle for calibrating the gain-power product of the transmitting antenna of the polarized transmitting antenna 2 of the calibration device is shown in fig. 7. Wherein, step S601 may include the following steps:
setting a standard gain horn antenna and a power meter connected with the standard gain horn antenna in a far field, and aligning a horn mouth of a polarized transmitting antenna 2 of the calibration device with the standard gain horn antenna;
the transmitting power of the calibration device is PjRadiated by said polarized transmitting antenna 2, antenna gain Gj(ii) a The distance between the standard gain horn antenna and the horn mouth of the polarized transmitting antenna 2 is RcThe space radiation power density of the standard gain horn antenna is DjThe aperture area of the standard gain horn antenna is AcThe power meter measures power as Pcj；
The power density of the space radiation signal received by the standard gain horn antenna is as follows:
Figure BDA0002983209270000131
the power meter measures the power as follows:
Figure BDA0002983209270000132
the gain power product of the transmitting antenna of the transmitting channel of the calibration device is as follows:
Figure BDA0002983209270000133
step S602, calibrating the power density measurement performance of the space radiation signal by the receiving channel of the calibrating device so as to calibrate the performance of the transmitting channel of the calibrator; the power density measurement performance comprises a power density measurement reference value and a power density measurement dynamic range, the power density measurement reference value is calibrated based on the standard reflection performance of a reflector, the power density measurement dynamic range controls the emission power of a calibration device, and the emission power is sent to a standard gain loudspeaker, so that the standard gain loudspeaker radiates to a receiving antenna of the calibration device to be calibrated.
In the embodiment of the invention, the calibration of the power density measurement performance of the space radiation signal by the receiving channel of the calibration device is the main work of the calibration device for calibrating the simulated target transmitting power of the transmitting channel of the calibrator. The dynamic state and the precision of the simulated target transmitting power of the simulated target signal transmitted by the transmitting channel of the calibration instrument determine whether the weather radar calibration dynamic state can cover the radar intensity measurement dynamic state or not, and whether the calibration precision can ensure the error calibration of a radar measurement precision system or not.
In a specific implementation, step S602 may include the following steps:
radiating a signal to a reflector through a transmitting channel of the calibration device, wherein the spatial power density at the reflector is as follows:
Figure BDA0002983209270000141
(4) in the formula: ptjGtjThe gain power product of the transmitting antenna of the transmitting channel of the calibrating device is calibrated; rjThe distance between the center of a reflector and a receiving antenna bell mouth of the calibration device is defined, the radiation signal of the calibration device is received, excited and reflected on the surface of the reflector, part of the reflected signal enters a receiving antenna of the calibration device, the size of the reflected signal is described by the cross section area sigma of a reflector radar, and the echo power density reflected by the reflector on the bell mouth surface of the receiving antenna of the calibration device is as follows:
Figure BDA0002983209270000142
in various embodiments of the present invention, the reflector may be a metal ball or may be a corner reflector.
When the reflector is a metal ball, the cross-sectional area of the metal ball radar is sigma pi a2(ii) a In the formula (I), the compound is shown in the specification,
Figure BDA0002983209270000143
a is the radius of the metal ball, S is the perimeter of the metal ball, and the perimeter is measured by a measuring tool. Fig. 8 shows a schematic diagram of the principle of calibrating the power density measurement performance of the spatial radiation signal by the receiving channel of the calibration device when the reflector is a metal ball.
When the reflector is a corner reflector, the radar cross-sectional area of the corner reflector is
Figure BDA0002983209270000144
In the formula, b is the length of the right angle, and the length of the right angle is measured by a tape measure or other length measuring tools.
Step S603, establishing a reflector measurement system in which the bell mouths of the polarized transmitting antenna 2 and the polarized receiving antenna of the calibration apparatus are both aligned to a far-field reflector; the calibration device measures the radar cross section of the reflector according to a pulse radar equation, measures the echo power of the reflector at different distances according to a weather radar equation, and establishes a distance-radar cross section-echo power parameter table.
In the embodiment of the invention, the radar sectional area of the reflector is measured by the calibration device according to a pulse radar equation, the reflection of a microwave absorbing material medium in an indoor measurement microwave darkroom is eliminated by erecting a measurement mode in a vertical headspace open space, and a measurement environment which is cleaner than the microwave darkroom is obtained; by improving the isolation degree of a receiving and transmitting antenna, the amplitude of a leakage signal of the receiving and transmitting antenna is smaller than the amplitude of a metal ball echo with the minimum diameter of 300mm by 20dB, the isolation influence of the receiving and transmitting antenna is reduced, the receiver can be linearly amplified during the pulse transmitting period by designing proper gain of a receiver in a pulse transmitting interval, a signal processing and collecting interval is set to the front edge of the transmitted pulse to the end of the pulse period, the full-distance range echo at the start of a distance of '0' can be collected and processed, the distance measurement blind area of a calibration device is made to be '0', and the non-blind area radar cross-sectional area measurement of a reflector erected in a short distance when; the interference cancellation and transmission isolation signal component is automatically measured in the error of the measurement system, so that the measurement influence of mutual coupling of the transmission and transmission antennas on the metal ball and the angle reflector is ignored.
Wherein establishing a reflector measurement system may comprise the steps of:
selecting a field open space with flat ground, suspending a metal ball or angle reflectors with different sizes by using three support rods and pull ropes without buildings within 50m, erecting the metal ball or the angle reflectors above horn mouths of a polarized transmitting antenna 2 and a polarized receiving antenna of the calibration device, wherein the distance between a far field of the antenna of the calibration device and the reflectors is
Figure BDA0002983209270000151
Wherein, D is the calibration device antenna bore size, about 0.12m, and lambda is radar operating wavelength, and 0.032m is got to the X wave band, and 0.053m is got to the C wave band, and about 0.1m is got to the S wave band, and the corresponding far field distance is: the X wave band is about 0.625m, the C wave band is about 0.377m, the S wave band is about 0.2m, and the metal ball is erected at a height of 1.5m away from the antenna, so that the far-field measurement requirement of an X, C, S wave band reflector can be met. The support rod is made of wood or plastic materials, the distance between the support rod and the calibration device is 5m, the pull rope is made of nylon thin wires, the support rod and the pull rope basically do not reflect electromagnetic waves, and the influence of peripheral reflection on a measurement result is eliminated. When the reflector is a metal ball, the principle schematic of the reflector measurement system is shown in fig. 9.
The radar cross section of the reflector is measured according to the pulse radar equation:
Figure BDA0002983209270000152
in the above formula, PrReceiving echo power for radar, PtFor radar emission of peak power, GtFor radar transmitting antenna gain, GrGain of radar transmitting antenna, FtFor the calibrator transmitting antenna to target radar pattern factor, FrReceive antenna pattern factor for target radar to calibrator, L is system loss, LaIn order to reduce the atmospheric transmission loss, sigma is the radar sectional area of the reflector, tau is the radar emission pulse width, and R is the distance between the radar and the reflector;
setting a pulse radar constant:
Figure BDA0002983209270000153
σ＝CpPrR4 (8)；
after the radar sectional area of the reflector is measured, the distance R from the center of the reflector to the antenna bell mouth of the calibration device is measured by the measuring tool rulerj。
Finally, according to a radar sectional area formula, measuring the echo power P of the reflector through a calibration devicerjAnd calculating the constant of the pulse radar, and establishing a reflector distance-radar sectional area-echo power parameter table.
Step S604, the calibration device calculates the reflectivity coefficient of the reflector in the weather radar according to the radar sectional area of the reflector, and converts the range-radar sectional area-echo power parameter table into a range-reflectivity coefficient-echo power parameter table; wherein the reflectivity coefficient range of the reflector is matched with the weather radar measurement dynamic range.
The weather radar equation may be:
Figure BDA0002983209270000161
in the formula: | K ∞2Is constant, Z is the reflectance coefficient; wherein:
Figure BDA0002983209270000162
wherein m is complex refractive index, centimeter band, temperature is 0-20 deg.C, when the particles are in water state, | K2Approximately equal to 0.93, | K shadingin ice state2≈0.2；
Figure BDA0002983209270000163
Where theta is the radar azimuth beam width,
Figure BDA0002983209270000164
for pitch beam width, c is the speed of light.
Setting weather radar constants:
Figure BDA0002983209270000165
and in combination with the above formula, the reflectivity coefficient of the reflector in the weather radar is calculated as follows:
Figure BDA0002983209270000166
it should be noted that, in the embodiments of the present invention, the reflectivity coefficient is also referred to as intensity, i.e., echo intensity.
In practice, the intensity and the radar cross section are represented by standard reflectors such as metal balls or angle reflectors, the same reflectors appear as point targets in pulse radar measurement, and the echo power represents the radar target cross section; and the target appears as a detection unit body target in a weather radar, the total cross section area of a water-containing particle filled in the detection unit is equivalent, and the echo power represents the reflectivity coefficient (target intensity) of the detection unit body target. Therefore, the reflectivity coefficient of the reflector with the same radar cross section is different under different weather radar single detection units and different beam widths and pulse widths.
Figure BDA0002983209270000171
The real value of the radar cross section of the reflectors such as the metal ball or the angle reflector corresponding to the weather radar echo intensity can be calculated through the formula, namely the distance-radar cross section-echo power parameter table is converted into a distance-reflectivity coefficient-echo power parameter table.
Step S605, establishing a simulated target transmitting power calibration system, wherein in the simulated target transmitting power calibration system, the bell mouths of the polarized transmitting antenna 2 and the polarized receiving antenna of the calibration device are both aligned to the antenna of a far-field calibration instrument, wherein the simulated target transmitting power of the calibration instrument is adjusted according to the distance-reflectivity coefficient-echo power parameter table, so that the echo power corresponding to the simulated target transmitting power received by the calibration device under a specific distance is equal to the echo power of the reflector received by the calibration device under the specific distance under the corresponding reflectivity coefficient, and the simulated target transmitting power is recorded, so as to obtain the distance-reflectivity coefficient-simulated target transmitting power parameter table.
In the embodiment of the invention, the reflector is used for calibrating the transmitting power of the simulated target and establishing a distance-intensity (reflectivity coefficient) -simulated target transmitting power parameter table for calibrating the weather radar by a calibrating instrument. Specifically, the method is described. Step S605 may include the steps of:
selecting a field open space with flat ground, suspending the calibration instrument antenna by using three supporting rods and a pull rope, erecting the calibration instrument antenna above horn mouths of a polarization transmitting antenna 2 and a polarization receiving antenna of the calibration device, and connecting the calibration instrument antenna to a calibration instrument through a cable. A schematic diagram of a simulated target transmission power calibration system is shown in fig. 10, an erection method of the simulated target transmission power calibration system is similar to that of a metal ball (i.e., similar to that of fig. 9), a calibration instrument antenna is erected at a place where the metal ball is erected, the calibration instrument antenna is connected to a calibration instrument through a cable, and before calibration, insertion loss of the calibration instrument antenna is calibrated by comparing with an internal antenna of the calibration instrument.
When the calibration instrument simulates the target transmitting power to calibrate, the calibration device transmits a signal, the calibration instrument receives a detection pulse signal transmitted by the calibration device and generates a 0-distance simulated target signal, the Doppler frequency of the simulated target signal can be set to be more than 150hz, a leakage signal and a surrounding environment reflection signal are transmitted far away from the 0-Doppler frequency, the 0-Doppler frequency leakage and clutter interference are filtered by using FFT Doppler filtering of the calibration device, the simulated target transmitting power of the simulated target signal is more accurately measured, the echo power of the simulated target signal received by the calibration device under the simulated target transmitting power at a specific distance is equal to the echo power of a reflector received by the calibration device under the specific distance under the corresponding reflectivity coefficient by adjusting the simulated target transmitting power, and the simulated target transmitting power is recorded, the simulated target transmitting power corresponds to the metal ball echo intensity at the distance of the erection point.
When executed, the distance RjAt the received echo power P of the reflectorrjConverted to at a distance RbThe echo power of the received analog target signal of the calibrator is adjusted to make the calibration device receiveThe echo power of the calibrator is PrbCalibrating the simulated target transmitting power P corresponding to the current radar reflection sectional area sigma of the reflectortb。
When the erection position of the calibration instrument is different from the position of the reflector, the calibration instrument and the calibration device are aligned with each other and converted by the following formula:
Figure BDA0002983209270000181
Figure BDA0002983209270000182
in the formula: prjIs the echo power of the reflector, RjIs the distance between the reflector and the calibration device;
Figure BDA0002983209270000183
in the formula: prbFor calibrating the echo power, R, of the instrumentbThe distance between the calibrator and the calibrating device;
simulating the echo power corresponding to the target transmitting power at the distance of the equivalent calibrator with the same reflector:
Figure BDA0002983209270000184
adjusting the simulated target transmit power Ptb＝KbPrbMaking the echo power received by the calibration device be PrbRecording the simulated target transmission power PtbThe calibration of the reflector to the emission power of the simulation target can be realized;
on the basis, a distance-reflectivity coefficient-simulated target transmitting power parameter table is established according to the following formula:
Figure BDA0002983209270000191
and step S606, calibrating the true value of the echo intensity of the weather radar by using the calibration instrument after the transmitting channel and the receiving channel are calibrated according to the distance-reflectivity coefficient-simulated target transmitting power parameter table.
In summary, the embodiment of the invention provides a thought for calibrating the simulated target transmitting power and the echo intensity truth value reference of a calibrator by calibrating a true value of a simulated target of a weather radar according to a true value of the simulated target of the calibrator by a calibration device, wherein the calibration device calibrates the simulated target transmitting power and the echo intensity truth value reference of the simulated target by utilizing the characteristics of an objective reflection true value of a metal ball and a corner reflector and by means of the high-precision measurement performance of the calibration device on the power density of a spatial radiation signal.
The calibration device measures the density of the reflected power of the metal ball and/or the angle reflectors with different sizes through the high-precision measurement performance of the calibration device on the power density of the space radiation signal, the calibration device is calibrated through the radar cross sections of the different reflectors, the echo intensity truth value basis of the different reflectors corresponding to the distance is determined, the echo intensity range of the reflectors is matched with the measurement dynamic range of the weather radar echo intensity, the echo intensity truth value basis intervals of the different reflectors are partitioned at equal intervals, the different-intensity simulation target transmitting power is calibrated through the set reflector echo power, and the intensity truth value of the partition with equal intervals and the simulation target transmitting power truth value basis are formed.
The embodiment of the invention can be used for checking and calibrating the strength calibration function, the dynamic state, the resolution, the precision and the like of the calibrator, is one of the main functions of the calibration device, the strength check and calibration of the calibrator has the calibration precision which is 3-10 times better than the measurement precision of a true value of the echo strength of the weather radar, can meet the basic requirements of the calibrator on large dynamic state, high precision and long-term stability of parameters for calibrating the true value of the echo strength of the weather radar, ensures that the calibrator undertakes the tasks of system error calibration and calibration for the true value of the echo strength of the weather radar when the fluctuation error of each parameter measured by the true value of the echo strength of the weather radar meets the requirements, undertakes the alarm task when the fluctuation error of the measured parameter of the true value of the echo strength of the weather radar exceeds the specified requirements, informs a guarantee personnel to check and maintain the weather, after the problem that the fluctuation error exceeds the standard is solved, the error of the weather radar echo intensity true value measurement system is calibrated, so that the data quality such as the dynamic, resolution, precision, long-term stability and the like of the weather radar echo intensity true value measurement parameters is guaranteed.
It should be noted that, in the present specification, the embodiments are all described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other.
It should also be noted that, in this document, the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience in describing the present invention and simplifying the description, but do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention. Moreover, relational terms such as "first" and "second" are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions or should not be construed as indicating or implying relative importance. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in the process, method, article, or terminal equipment comprising the element.
The technical solutions provided by the present application are described in detail above, and the principles and embodiments of the present application are described herein by using specific examples, which are only used to help understanding the present application, and the content of the present description should not be construed as limiting the present application. While various modifications of the illustrative embodiments and applications will be apparent to those skilled in the art based upon this disclosure, it is not necessary or necessary to exhaustively enumerate all embodiments, and all obvious variations and modifications can be resorted to, falling within the scope of the disclosure.

Claims (10)

1. A calibration device for a prover comprising:
the polarization receiving antenna comprises a main machine (1), a polarization transmitting antenna (2) and a polarization receiving antenna, wherein the polarization transmitting antenna (2) and the polarization receiving antenna are respectively connected with the main machine (1), and horn mouths of the polarization transmitting antenna (2) and the polarization receiving antenna are positioned on the same horizontal plane;
the polarized receiving antenna comprises a vertical polarized receiving antenna (3) and a horizontal polarized receiving antenna (4);
the polarized transmitting antenna (2) is arranged on the host, and the polarization direction of the polarized transmitting antenna (2) is arranged at an angle of 45 degrees relative to the horizontal plane;
the vertical polarization receiving antenna (3) is arranged on the host, and the polarization direction of the vertical polarization receiving antenna (3) is vertical to the horizontal plane;
the horizontal polarization receiving antenna (4) is arranged on the main machine, and the polarization direction of the horizontal polarization receiving antenna (4) is parallel to the horizontal plane.
2. Calibration device according to claim 1, characterized in that the host (1) comprises:
the device comprises a transmitter, an H receiver, a V receiver, a frequency synthesizer, an H signal processing module, a V signal processing module, a data processing module and a display control terminal;
the transmitter is respectively connected with the frequency synthesizer and the polarized transmitting antenna (2);
the H receiver is respectively connected with the frequency synthesizer, the vertical polarization receiving antenna (3) and the H signal processing module;
the V receiver is respectively connected with the frequency synthesizer, the horizontal polarization receiving antenna (4) and the V signal processing module;
the data processing module is respectively connected with the H signal processing module, the V signal processing module and the display control terminal.
3. The calibration device according to claim 2, wherein the frequency synthesizer comprises a crystal oscillator, a first power divider, a first phase-locked loop, a second phase-locked loop, a first signal generator DDS, and a second DDS;
the first power divider is connected with the crystal oscillator, the first phase-locked loop, the second DDS, the H signal processing module and the V signal processing module respectively;
the first phase-locked loop is connected with the transmitter sequentially through a first amplifier, a first power divider and a first frequency mixer, the first frequency mixer is connected with the first DDS through a first low-pass filter, and the first power divider is connected with the H receiver and the V receiver respectively;
the second phase-locked loop is connected with the second power divider;
and the second DDS is respectively connected with the H receiver and the V receiver sequentially through a second low-pass filter, a second amplifier and a third power divider.
4. The calibration apparatus of claim 2, wherein the H-receiver comprises:
the second mixer, the third low-pass filter, the third amplifier, the third mixer, the fourth low-pass filter and the first intermediate frequency amplifier are connected in sequence;
the second mixer is respectively connected with the vertical polarization receiving antenna (3) and the first power divider;
the third mixer is connected with the second amplifier;
the first intermediate frequency amplifier is connected with the H signal processing module.
5. A method for calibrating a true value of echo intensity of a weather radar is characterized by comprising the following steps:
calibrating the gain-power product of the transmitting antenna of the transmitting channel of the calibrating device according to any one of claims 1 to 4, and transmitting a reference signal through the transmitting channel of the calibrating device after calibration to calibrate the performance of the receiving channel of the calibrator;
calibrating the power density measurement performance of the space radiation signal by the receiving channel of the calibrating device so as to calibrate the performance of the transmitting channel of the calibrator; the power density measurement performance comprises a power density measurement reference value and a power density measurement dynamic range, the power density measurement reference value is calibrated based on the standard reflection performance of a reflector, the power density measurement dynamic range controls the emission power of a calibration device, and then the emission power is sent to a standard gain loudspeaker, so that the standard gain loudspeaker radiates to a receiving antenna of the calibration device for calibration;
establishing a reflector measuring system in which the bell mouths of the polarized transmitting antenna (2) and the polarized receiving antenna of the calibration device are both aligned with a far-field reflector; the calibration device measures the radar cross section of the reflector according to a pulse radar equation, measures the echo power of the reflector at different distances according to a weather radar equation, and establishes a distance-radar cross section-echo power parameter table;
the calibration device calculates the reflectivity coefficient of the reflector in the weather radar according to the radar sectional area of the reflector, and converts the distance-radar sectional area-echo power parameter table into a distance-reflectivity coefficient-echo power parameter table; wherein the reflectivity coefficient range of the reflector is matched with the weather radar measurement dynamic range;
establishing a simulated target transmitting power calibration system, wherein in the simulated target transmitting power calibration system, the bell mouths of the polarized transmitting antenna (2) and the polarized receiving antenna of the calibration device are both aligned to the antenna of a far-field calibration instrument, wherein the simulated target transmitting power of the calibration instrument is adjusted according to the distance-reflectivity coefficient-echo power parameter table, so that the echo power corresponding to the simulated target transmitting power received by the calibration device under a specific distance is equal to the echo power of the reflector received by the calibration device under the specific distance under the corresponding reflectivity coefficient, and the simulated target transmitting power is recorded to obtain a distance-reflectivity coefficient-simulated target transmitting power parameter table;
and calibrating the true value of the echo intensity of the weather radar by using the calibration instrument after the transmitting channel and the receiving channel are calibrated according to the distance-reflectivity coefficient-simulated target transmitting power parameter table.
6. The method of claim 5, wherein calibrating the transmit antenna gain power product of the transmit channel of the calibration device comprises:
setting a standard gain horn antenna and a power meter connected with the standard gain horn antenna in a far field, and aligning a horn mouth of a polarized transmitting antenna (2) of the calibration device with the standard gain horn antenna;
the transmitting power of the calibration device is PjRadiated by said polarized transmitting antenna (2), antenna gain Gj(ii) a The distance between the standard gain horn antenna and the horn mouth of the polarized transmitting antenna (2) is RcThe space radiation power density of the standard gain horn antenna is DjThe aperture area of the standard gain horn antenna is AcThe power meter measures power as Pcj；
The power density of the space radiation signal received by the standard gain horn antenna is as follows:
Figure FDA0002983209260000031
the power meter measures the power as follows:
Figure FDA0002983209260000032
the gain power product of the transmitting antenna of the transmitting channel of the calibration device is as follows:
Figure FDA0002983209260000033
7. the method of claim 5, wherein calibrating the calibration device receive channel to calibrate power density measurement performance of the spatial radiation signal comprises:
radiating a signal to a reflector through a transmitting channel of the calibration device, wherein the spatial power density at the reflector is:
Figure FDA0002983209260000034
(4) in the formula: ptjGtjThe gain power product of the transmitting antenna of the transmitting channel of the calibrating device is calibrated; rjThe distance between the center of a reflector and a receiving antenna bell mouth of the calibration device is defined, the radiation signal of the calibration device is received, excited and reflected on the surface of the reflector, part of the reflected signal enters a receiving antenna of the calibration device, the size of the reflected signal is described by the cross section area sigma of a reflector radar, and the echo power density reflected by the reflector on the bell mouth surface of the receiving antenna of the calibration device is as follows:
Figure FDA0002983209260000041
8. method according to claim 7, characterized in that a reflector measuring system is established in which the calibration device polarizes the bell mouths of the transmitting antenna (2) and the receiving antenna to be directed towards a far-field reflector; the calibration device measures the radar cross section of the reflector according to a pulse radar equation and measures the echo power of the reflector at different distances according to a weather radar equation, and the calibration device comprises the following steps:
selecting a field open space with flat ground, suspending a reflector by using three supporting rods and a pull rope, and erecting the reflector above the bell mouths of a polarized transmitting antenna (2) and a polarized receiving antenna of the calibration device, wherein the distance between the bell mouth and a far-field reflector is
Figure FDA0002983209260000042
D is the caliber size of the bell mouth, and lambda is the radar working wavelength;
the radar cross section of the reflector is measured according to the pulse radar equation:
Figure FDA0002983209260000043
in the above formula, PrReceiving echo power for radar, PtFor radar emission of peak power, GtFor radar transmitting antenna gain, GrGain of radar transmitting antenna, FtFor the calibrator transmitting antenna to target radar pattern factor, FrReceive antenna pattern factor for target radar to calibrator, L is system loss, LaIn order to reduce the atmospheric transmission loss, sigma is the radar sectional area of the reflector, tau is the radar emission pulse width, and R is the distance between the radar and the reflector;
setting a pulse radar constant:
Figure FDA0002983209260000044
σ＝CpPrR4 (8)；
after the radar sectional area of the reflector is measured, the distance R from the center of the reflector to the bell mouth is measured through a measuring tool rulerjMeasuring the echo power P of the reflector by means of said calibration devicerj。
9. The method of claim 8, wherein the calibration device calculates a reflectivity coefficient of the reflector in the weather radar based on the radar cross-sectional area of the reflector, comprising:
the weather radar equation is:
Figure FDA0002983209260000051
in the formula: | K ∞2Is constant, Z is the reflectance coefficient; wherein:
Figure FDA0002983209260000052
wherein m is complex refractive index, centimeter band, temperature is 0-20 deg.C, when the particles are in water state, | K2Approximately equal to 0.93, | K shadingin ice state2≈0.2；
Figure FDA0002983209260000053
In the formula: theta is the radar azimuth beamwidth,
Figure FDA0002983209260000054
pitch angle beam width, c is speed of light;
setting weather radar constants:
Figure FDA0002983209260000055
and in combination with the above formula, the reflectivity coefficient of the reflector in the weather radar is calculated as follows:
Figure FDA0002983209260000056
10. the method according to claim 9, wherein a calibration system of simulated target transmitting power is established, in which the bell mouths of the polarized transmitting antenna (2) and the polarized receiving antenna of the calibration device are aligned with the antenna of a far-field calibration instrument, wherein the simulated target transmitting power of the calibration instrument is adjusted according to the parameter table of distance-reflectivity coefficient-echo power, so that the simulated target transmitting power received by the calibration device is equal to the echo power of the reflector, and the parameter table of distance-reflectivity coefficient-simulated target transmitting power is recorded, comprising the following steps:
selecting a field open space with flat ground, suspending a calibration instrument antenna by using three supporting rods and a pull rope, and erecting the calibration instrument antenna above horn mouths of a polarization transmitting antenna (2) and a polarization receiving antenna of the calibration device, wherein the calibration instrument antenna is connected to a calibration instrument through a cable;
will be at a distance RjAt the received echo power P of the reflectorrjConverted to at a distance RbAdjusting the simulated target transmitting power of the simulated target signal to make the echo power of the calibrator PrbCalibrating the simulated target transmitting power P corresponding to the current radar reflection sectional area sigma of the reflectortb：
When the erection position of the calibration instrument is different from the position of the reflector, the calibration instrument and the calibration device are aligned with each other and converted by the following formula:
Figure FDA0002983209260000061
Figure FDA0002983209260000062
in the formula: prjIs the echo power of the reflector, RjIs the distance between the reflector and the calibration device;
Figure FDA0002983209260000063
in the formula: prbFor calibrating the echo power of the instrument, RbThe distance between the calibrator and the calibrating device is obtained;
Figure FDA0002983209260000064
adjusting the simulated target transmit power Ptb＝KbPrbMaking the echo power received by the calibration device be PrbRecording the simulated target transmit power P at that timetbEstablishing a distance-reflectivity coefficient-simulated target transmitting power parameter table according to the following formula:
Figure FDA0002983209260000065
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