CN113109771B - Calibration device for calibration instrument and true value calibration method for weather radar echo intensity - Google Patents
Calibration device for calibration instrument and true value calibration method for weather radar echo intensity Download PDFInfo
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Abstract
The invention provides a calibration device for a calibration instrument and a true value calibration method for weather radar echo intensity, and relates to the technical field of weather radar calibration. The embodiment of the invention provides a thought for calibrating the true value of the echo intensity of the weather radar by means of calibrating the true value of the simulation target of the calibration instrument, calibrating the true value reference of the simulation target of the calibration instrument by means of the calibration device, and calibrating the simulation target transmitting power of the calibration instrument and the true value reference of the echo intensity of the weather radar by means of the high-precision measuring performance of the calibration device on the power density of the space radiation signal by means of the objective reflection true value characteristics of the metal ball and the angle reflector.
Description
Technical Field
The invention relates to the technical field of weather radar calibration, in particular to a calibration device for a calibration instrument and a true value calibration method for the echo intensity of a weather radar.
Background
The number of the new generation weather radar (CINRAD) nationally networking on-line is 230 or more, and the new generation weather radar (CINRAD) plays an indispensable role in nationally refined weather forecast business and disaster weather monitoring and early warning. The accuracy and consistency of networking radar data directly influence radar application and benefit exertion, and particularly, the development of a digital forecasting mode provides higher requirements for networking radar data assimilation. The accuracy and the reliability of the weather radar detection data are improved, the quality of nationwide networking weather radar observation data is ensured, and the key point is to establish perfect weather radar calibration service, and provide technical specifications and platforms for supporting the calibration service.
Radar intensity measurement, speed measurement, coordinate measurement (distance, azimuth angle, pitch angle), spectral width measurement, differential reflectivity measurement and differential phase shift measurement are main system parameters of the weather radar, and are main marks for measuring radar quality. The system indexes such as the gain of the radar antenna, the transmitting power, the receiving sensitivity, the receiving dynamics, the clutter suppression ratio and the phase noise are the basic guarantee of the system indexes.
Because radar products lack system parameter measurement 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 subsystem parameter test is used for evaluating the radar performance in the production and use stage instead of the system parameter test after the products are shaped, so that the problem that the system parameters exceed standards is continuously found in the use of armies. The weather radar has no target range test link, and the subsystem index and part of the system index are determined through mature model experience to indirectly test the alternative method, so that the problem of exceeding of the system index is also caused in operation and maintenance, and the calibration instrument bears the calibration tasks of the double-polarization weather radar system index and the subsystem index. The calibration instrument itself needs to be calibrated periodically every year to ensure the calibration effect on the weather radar.
The true value calibration of the weather radar echo intensity is the core of the weather radar data quality control, and in the true value calibration process of the weather radar echo intensity, the current calibration instrument does not have a calibration means to the simulation target signal transmitted by the weather radar, only the measurement consistency calibration between the radar can be ensured, and the accuracy of the measurement result cannot be ensured.
Disclosure of Invention
The embodiment of the invention provides a calibration device for a calibrator and a true value calibration method for the echo intensity of a weather radar, wherein the calibration device can calibrate the performances of a receiving channel and a transmitting channel of the calibrator, and construct a range-reflectivity coefficient-simulated target transmitting power parameter table so that the calibrator calibrates the true value of the echo intensity of the weather radar according to the parameter table, thereby solving the problem of true value calibration accuracy of the echo intensity of the weather radar.
In order to solve the above problems, an embodiment of the present invention discloses a calibration device for a calibration instrument, including:
the host machine is respectively connected with the polarized transmitting antenna and the polarized receiving antenna, and the 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 perpendicular 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 one embodiment of the present invention, the host includes:
the system 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 respectively connected with the crystal oscillator, the first phase-locked loop, the second DDS, the H signal processing module and the V signal processing module;
the first phase-locked loop is connected with the transmitter through a first amplifier, a first power divider and a first mixer in sequence, the first mixer is connected with the 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 a 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.
In one 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 sequentially connected;
the second mixer is respectively connected with the vertical polarization receiving antenna 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.
In order to solve the problems, the embodiment of the invention also discloses a strength calibration method of the weather radar comprehensive calibration instrument, which comprises the following steps:
calibrating the gain power product of a transmitting antenna of a transmitting channel of a calibrating device according to the embodiment of the invention, and transmitting a reference signal through the calibrated transmitting channel of the calibrating device so as to calibrate the performance of a receiving channel of a 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 calibrating device; 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 the reflector, the power density measurement dynamic range is used for controlling the transmitting power of the calibration device, and the transmitting power is sent to the standard gain horn so that the standard gain horn can radiate to a receiving antenna of the calibration device for calibration;
Establishing a reflector measuring system, wherein the horn 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 sectional area 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 sectional area-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; the reflectivity coefficient range of the reflector is matched with the weather radar measurement dynamic range;
establishing a simulation target transmitting power calibration system, wherein in the simulation target transmitting power calibration system, the horn mouths of a polarization transmitting antenna and a polarization receiving antenna of the calibration device are aligned to the antenna of a far-field calibrator, wherein the simulation target transmitting power of the calibrator is adjusted according to the distance-reflectivity coefficient-echo power parameter table, so that the echo power corresponding to the simulation target transmitting power received by the calibration device at a specific distance is equal to the echo power of the reflector received by the calibration device at the specific distance at the corresponding reflectivity coefficient, and the simulation target transmitting power is recorded to obtain the distance-reflectivity coefficient-simulation target transmitting power parameter table;
And calibrating the echo intensity true value of the weather radar according to the distance-reflectivity coefficient-simulated target transmitting power parameter table by using the calibration instrument after the transmitting channel and the receiving channel are calibrated.
In an embodiment of the present invention, calibrating a gain power product of a transmitting antenna of a transmitting channel of a calibrating device 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 the horn mouth of the polarized transmitting antenna of the calibrating device with the standard gain horn antenna;
the transmitting power of the calibrating device is P j Antenna gain G by the polarized transmitting antenna radiation j The method comprises the steps of carrying out a first treatment on the surface of the The distance between the standard gain horn antenna and the horn mouth of the polarized transmitting antenna is R c The space radiation power density of the standard gain horn antenna is D j The caliber area of the standard gain horn antenna is A c The power meter measures the power P cj ；
The power density of the space radiation signal received by the standard gain horn antenna is as follows:
the power meter measures the power as follows:
the gain power product of the transmitting antenna of the transmitting channel of the calibrating device is as follows:
in one embodiment of the present invention, the calibration device receiving channel is used for calibrating the power density measurement performance of the space radiation signal, and the method comprises the following steps:
Transmitting a signal through the calibration means to the reflector where the spatial power density is:
(4) Wherein: p (P) tj G tj Gain power product of transmitting antenna for transmitting channel of the calibrating device, calibrated; r is R j For the distance between the center of the reflector and the horn mouth of the receiving antenna of the calibrating device, the radiation signal of the calibrating device is received, excited and reflected on the surface of the reflector, part of the reflected signal enters the receiving antenna of the calibrating device, the reflected signal is described by the radar cross-sectional area sigma of the reflector, and the echo power density reflected by the reflector on the horn mouth surface of the receiving antenna of the calibrating device is as follows:
in one embodiment of the invention, a reflector measuring system is established, wherein the horn mouths of the polarized transmitting antenna and the polarized receiving antenna of the calibrating device are aligned with the far-field reflector; the calibration device measures the radar sectional area of the reflector according to a pulse radar equation, and measures the echo power of the reflector under 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 support rods and pull ropes, erecting the horn mouths of a polarized transmitting antenna and a polarized receiving antenna of the calibrating device above, wherein the distance between the horn mouths and a far-field reflector is as follows 
Wherein D is the caliber size of the horn mouth, and lambda is the working wavelength of the radar;
radar cross-sectional area measurement of the reflector is measured according to the pulsed radar equation:
in the above, P r For radar to receive echo power, P t For radar emission peak power, G t For the gain of the radar transmitting antenna, G r Radar transmitting antenna gain, F t For calibrating the pattern factor of the antenna to the target radar of the instrument, F r Receiving antenna pattern factors for target radar to reach a calibration instrument, wherein L is system loss, and L a The radar cross section area of the reflector is denoted by sigma, the radar emission pulse width is denoted by tau, and the distance between the radar and the reflector is denoted by R;
setting a pulse radar constant:
σ＝C p P r R 4 (8)；
after the radar cross-sectional area of the reflector is measured, measuring the distance R from the center of the reflector to the bell mouth by a measuring tool ruler j Measuring the echo power P of the reflector by means of the calibration device rj 。
In an embodiment of the present invention, the calibration device calculates a reflectivity coefficient of the reflector in the weather radar according to a radar cross-sectional area of the reflector, including:
the weather radar equation is:
wherein: k 2 Is constant, Z is the reflectance coefficient; wherein:
wherein m is complex refractive index, cm wave band, temperature is 0-20 ℃, and particle size When the son is in water state, K is 2 In the ice state, 0.93, K 2 ≈0.2；
Where θ is the radar azimuth beam width,
the pitch angle beam width, c is the speed of light;
let weather radar constant:
combining the above, the reflectivity coefficient of the reflector in the weather radar is calculated as follows:
in an embodiment of the present invention, a simulated target transmitting power calibration system is established, in the simulated target transmitting power calibration system, a polarized transmitting antenna and a horn mouth of a polarized receiving antenna of the calibration device are both aligned to an antenna of a far-field calibration device, wherein, according to the distance-reflectivity coefficient-echo power parameter table, the simulated target transmitting power of the calibration device is adjusted so that the simulated target transmitting power received by the calibration device is equal to the echo power of the reflector, and the distance-reflectivity coefficient-simulated target transmitting power parameter table is recorded and obtained, and the method includes the following steps:
selecting a field open space with flat ground, suspending a calibrator antenna by using three struts and stay ropes, erecting the calibrator antenna above horn mouths of a polarized transmitting antenna and a polarized receiving antenna of the calibration device, and connecting the calibrator antenna to a calibrator through a cable;
distance R j Echo power P of reflector received at rj Converted to the distanceR b The echo power of the calibrator received by the calibration device is P, and the simulated target transmitting power of the simulated target signal is adjusted to make the echo power of the calibrator received by the calibration device be P rb Calibrating simulated target transmitting power P corresponding to current radar reflecting sectional area sigma of reflector tb ：
When the erection position of the calibration instrument is different from the position of the reflector, the calibration instrument and the calibration device are mutually aligned, and the calibration instrument is converted by the following formula:
wherein: p (P) rj R is the echo power of the reflector j Is the distance between the reflector and the calibration device;
wherein: p (P) rb For calibrating the echo power of the instrument, R b The distance between the calibration instrument and the calibration device is set;
adjusting the simulated target transmit power P tb ＝K b P rb The echo power received by the calibration device is P rb Recording the simulated target transmitting power P at this time tb ；
On this basis, a range-reflectance coefficient-simulated target transmit power parameter table is established according to the following formula:
the embodiment of the invention has the following advantages:
the calibration device comprises a host machine, wherein a polarized transmitting antenna, a vertical polarized receiving antenna and a horizontal polarized receiving antenna are arranged on the host machine, and the polarized transmitting antenna, the vertical polarized receiving antenna and the horizontal polarized receiving antenna are arranged on the top end face of the host machine side by side, and the polarized 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 equal horizontal polarization and vertical polarization amplitude and 0 degree phase difference can be transmitted to a calibrator, thereby realizing the calibration of the power density measurement performance of space radiation signals of the calibrator polarized receiving dual channels (vertical polarized receiving channel and horizontal polarized receiving channel); the polarization direction of the vertical polarization receiving antenna is perpendicular to the horizontal plane, so that the vertical polarization component in the analog target signal transmitted by the calibration instrument can be effectively received, the polarization direction of the horizontal polarization receiving antenna is parallel to the horizontal plane, the horizontal polarization component in the analog target signal transmitted by the calibration instrument can be effectively received, and further the calibration of the dynamic and the accuracy of the analog target transmitting power of the transmitting channel of the calibration instrument is realized;
The embodiment of the invention provides a thought that the true value calibration of the echo intensity of the weather radar is calibrated by means of the true value of the simulation target of the calibration instrument, the true value reference of the simulation target of the calibration instrument is calibrated by means of the calibration device, the calibration device utilizes the objective reflection true value characteristics of the metal ball and the angle reflector, and the calibration device is used for calibrating the power density high-precision measurement performance of the space radiation signal, the transmission power of the simulation target of the calibration instrument and the true value reference of the echo intensity thereof, and further the true value of the echo intensity of the weather radar is calibrated.
Drawings
In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a schematic three-dimensional structure of a calibration device of the present invention;
FIG. 2 is a front view of the calibration device of FIG. 1 of the present invention;
FIG. 3 is a side view of the calibration device of FIG. 1 of 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 diagram of the circuitry of the calibration device of the present invention;
FIG. 6 is a flow chart of steps of a method for true value calibration of weather radar echo intensity according to the present invention;
FIG. 7 is a schematic diagram of the present invention for calibrating the gain power product of a polarized transmit antenna of a calibration device;
FIG. 8 is a schematic diagram of the calibration device receiving channel for calibrating the power density measurement performance of the spatial radiation signal according to the present invention;
FIG. 9 is a schematic diagram of a metal sphere 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.
Reference numerals illustrate:
1-a host; a 2-polarized transmitting antenna; 3-a vertically polarized receiving antenna; 4-horizontally polarized receiving antennas; 5-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 following description of the embodiments of the present application will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.
Referring to fig. 1 to 3, there is shown a schematic structural diagram of a calibration device for a calibration instrument according to the present invention, which at least solves the technical problems set forth in the present invention, and the calibration device may include:
the device comprises a host 1, a polarized transmitting antenna 2 and a polarized receiving antenna which are respectively connected with the host 1, wherein the 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 perpendicular to the horizontal plane;
the horizontal polarization receiving antenna 4 is arranged on the host, and the polarization direction of the horizontal polarization receiving antenna 4 is 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 calibrating device are arranged side by side on the top end surface of the host 1, and since the polarization direction of the polarized transmitting antenna 2 is set at an angle of 45 ° relative to the horizontal plane, a reference signal with equal horizontal polarization and vertical polarization amplitude and 0 ° phase difference can be transmitted to the calibrating device, thereby realizing the calibration of the power density measurement performance of the space radiation signal of the polarized receiving dual channels (vertical polarized receiving channel and horizontal polarized receiving channel) of the calibrating device. 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 device further comprises: a horizontal bubble (not shown) is connected to the polarized transmitting antenna 2, which can be used to calibrate whether the polarization direction of the polarized transmitting antenna 2 is arranged at an angle of 45 ° with respect to the horizontal. Regarding how the horizontal bubble is calibrated, reference may be made to the calibration principle of the existing horizontal bubble, and this is not repeated here.
The vertical polarization receiving antenna 3 of the calibration device is arranged in the direction perpendicular to the horizontal plane, so that the vertical polarization component in the analog target signal transmitted by the calibration instrument can be effectively received, the polarization direction of the horizontal polarization receiving antenna 4 is arranged in the direction parallel to the horizontal plane, the horizontal polarization component in the analog target signal transmitted by the calibration instrument can be effectively received, and further the calibration of the dynamic and precision of the analog target transmitting power of the transmitting channel of the calibration instrument is realized. The specific calibration method is referred to the subsequent method and will not be described in detail herein.
As shown in fig. 1, at least three antenna radio frequency interfaces are disposed on the host 1, and the polarized transmitting antenna 2, the vertical polarized receiving antenna 3 and the horizontal polarized receiving antenna 4 are connected to the three antenna radio frequency interfaces 7 one by one through cables, so that the transmitting signal generated in the host 1 can transmit the transmitting signal to the polarized transmitting antenna 2 through one of the cables, and transmit the related receiving signal received through the vertical polarized receiving antenna 3 and the horizontal polarized receiving antenna 4 through the other two cables.
Still further, with continued reference to fig. 1-3, the calibration device further includes: the azimuth rotary table 5 is arranged at the lower end of the host 1 and is connected with the host 1, and the azimuth rotary table 5 is used for rotating 0-360 degrees under the control of the host 1 so as to simulate the azimuth scanning of the radar.
According to the radar calibration system, radar circumferential scanning can be simulated through rotation of the azimuth rotary table 5, main subsystem index testing functions such as a far-field antenna pattern, antenna gain, transmitting power and frequency spectrum of the calibration instrument are tested, the radar subsystem parameter calibration function of the calibration instrument is checked, subsystem parameter calibration performance indexes are calibrated, and technical guarantees are established for data quality of the calibration instrument. Wherein, the scanning directions of the polarized transmitting antenna 2, the vertical polarized receiving antenna 3 and the horizontal polarized receiving antenna 4 face to the same side, so that the signals can be received and transmitted simultaneously under the rotation of the azimuth rotary table 5.
As shown in fig. 1 to 3, the calibration device further includes a base 6, where the base 6 is disposed below the azimuth turntable 5 and is connected to the azimuth turntable 5; the base 6 is internally provided with a power module, and the base 6 is externally provided with a power interface, a switch and a network port.
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 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 include an activation switch 602 to control the activation of the entire calibration device, and the portal 603 may be connected to an external data display device or to a calibrator. In order to improve the stability of the whole calibration device during operation, 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, a host 1 includes: the system 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.
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 respectively connected with the crystal oscillator, the first phase-locked loop, the second DDS, the H signal processing module and the V signal processing module; the first phase-locked loop is connected with the transmitter sequentially through a first amplifier, a first power divider and a first mixer, the first mixer is connected with the 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; 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 one embodiment of the 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 sequentially connected; 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.
With continued reference to fig. 5, in one embodiment of the invention, the V-receiver includes: 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 sequentially connected; 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 the CPCI motherboard, and can be conveniently plugged and unplugged. When the DDS digital direct frequency synthesizer is realized, the DDS digital direct frequency synthesizer in the frequency synthesizer can generate 960Mhz linear frequency modulation or narrow pulse signals, the signals are mixed with the 1 local oscillation signals generated by the first phase-locked loop to form transmitting radio frequency signals, S-band, C-band and X-band transmitting signals can be formed by changing different local oscillation frequencies, and the power of the transmitter is amplified and then output to the polarized transmitting antenna 2 with the polarization direction being 45 degrees relative to the horizontal plane, so that the reference signals with the phase difference of 0 degree, which are equal to the amplitude of the horizontal polarization and the vertical polarization, can be transmitted to the calibrator. The calibration instrument receives a reference signal transmitted by the calibration device in a far field, generates a simulated target signal, transmits the simulated target signal to the calibration device through a variable polarization transmitting antenna 2 with a polarization direction of 45 degrees, receives the simulated target signal with equal amplitude and 0-degree phase difference by a vertical polarization receiving antenna 3 and a horizontal polarization receiving antenna 4 of the calibration device, mixes, filters and amplifies the vertical polarization component and the horizontal polarization component of the simulated target signal twice, and then correspondingly transmits the signals to an H signal processing module and a 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 transmits the signals to a data processing module for carrying out good-for consistency calibration. Because the horizontal polarization and the vertical polarization of the analog target signal transmitted by the calibration instrument are equal in amplitude and have the phase difference of 0 degrees, 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 calibration device are compared through the data processing module, the amplitude consistency calibration of the vertical polarization receiving channel and the horizontal polarization receiving channel of the calibration device can be realized, and the effect of calibrating the analog target transmitting power of the transmitting channel of the calibration instrument is further ensured.
The mechanical and module composition structure of the calibrating device is described above, and the problem of true value calibration of the echo intensity of the weather radar is solved by calibrating the intensity of the calibrator by using the calibrating device.
Referring to fig. 6, an embodiment of the present invention provides a step flowchart of a weather radar echo intensity true value calibration method, which may include the following steps:
step S601, calibrating the gain power product of the transmitting antenna of the transmitting channel of the calibrating device according to the embodiment of the present invention, and transmitting the reference signal through the calibrated transmitting channel of the calibrating device to calibrate the performance of the receiving channel of the calibrator.
The measurement and calibration of the gain power product of the transmitting antenna of the transmitting channel of the calibrating device is the main basic work of the calibrating device for the measurement and calibration of the receiving channel of the calibrating device, the power density measurement performance of the receiving channel of the calibrating device for the space radiation signal is calibrated by the transmitting reference signal of the calibrating device, and the power of the reference signal is calibrated by the power meter.
The reference signal is radiated to the space through the calibration device polarized transmitting antenna, and the power product P of the calibration device polarized transmitting antenna is presented in the space tj G tj The power density radiated to the distance R is
The calibration instrument receiver receives the reference signal through the antenna, and the received signal amplitude is the caliber area of the receiving antenna multiplied by the space radiation power density.
The power density of the space radiation signal is measured, and the larger the antenna caliber area is, the larger the amplitude of the received signal is. The power density measurement performance calibration 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 calibrating device, and the gain power product of the transmitting antenna of the transmitting channel of the calibrating device is realized by controlling the transmitting power of the reference signal of the calibrating device. Since the spatial measurements cannot alone obtain the transmit power, the transmit channels are calibrated by measuring the transmit antenna gain power product. Therefore, calibrating the gain and power product of the polarized transmitting antenna of the calibrating device is one of the basic works of factory acceptance and annual audit calibration of the calibrating device.
In specific implementation, the principle of calibrating the gain power product of the transmitting antenna of the polarized transmitting antenna 2 of the calibrating device is shown in fig. 7. 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 the horn mouth of the polarized transmitting antenna 2 of the calibrating device with the standard gain horn antenna;
the transmitting power of the calibrating device is P j By radiation from the polarized transmitting antenna 2, antenna gain G j The method comprises the steps of carrying out a first treatment on the surface of the The distance between the standard gain horn antenna and the horn mouth of the polarized transmitting antenna 2 is R c The space radiation power density of the standard gain horn antenna is D j The caliber area of the standard gain horn antenna is A c The power meter measures the power P cj ；
The power density of the space radiation signal received by the standard gain horn antenna is as follows:
the power meter measures the power as follows:
the gain power product of the transmitting antenna of the transmitting channel of the calibrating device is as follows:
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 calibrating device; 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 the reflector, the power density measurement dynamic range is used for controlling the transmitting power of the calibrating device, and the transmitting power is sent to the standard gain horn, so that the standard gain horn radiates to the receiving antenna of the calibrating device for calibration.
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 calibration instrument. The simulation target transmitting power dynamic and the precision of the simulation target signal transmitted by the transmitting channel of the calibration instrument determine whether the radar intensity measuring dynamic can be covered by the calibration instrument for the weather radar calibration dynamic, and whether the radar measuring precision system error calibration can be ensured by the calibration precision.
In specific implementation, step S602 may include the following steps:
transmitting the channel through the calibration device to radiate a signal to a reflector where the spatial power density is:
(4) Wherein: p (P) tj G tj Gain power product of transmitting antenna for transmitting channel of the calibrating device, calibrated; r is R j For the distance between the centre of the reflector and the receiving antenna horn of the calibration device, the calibration device radiates signals which are received, excited and reflected at the reflector surface,and part of the reflected signals enter a receiving antenna of the calibrating device, the reflected signal size of the receiving antenna is described by the radar cross section sigma of the reflector, and the echo power density reflected by the reflector on the horn mouth surface of the receiving antenna of the calibrating device is as follows:
In various embodiments of the present invention, the reflector may be a metal sphere or an angular reflector.
When the reflector is a metal sphere, the radar cross-sectional area of the metal sphere is sigma=pi a 2 The method comprises the steps of carrying out a first treatment on the surface of the In the method, in the process of the invention,
a is the radius of the metal sphere, S is the circumference of the metal sphere, and the circumference is measured by a measuring tool. As shown in fig. 8, a schematic diagram of the calibration of the power density measurement performance of the spatial radiation signal by the calibration device receiving channel when the reflector is a metal sphere is shown.
When the reflector is an angular reflector, the angular reflector has a radar cross-sectional area of
Wherein b is a right angle side length, which is measured by a tape or other length measuring tool.
Step S603, a reflector measuring system is established, wherein the horn mouths of the polarized transmitting antenna 2 and the polarized receiving antenna of the calibrating device are aligned with far-field reflectors; the calibration device measures the radar sectional area 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 range-radar sectional area-echo power parameter table.
In the embodiment of the invention, the calibration device measures the radar cross section of the reflector according to a pulse radar equation, the calibration device measures the radar cross section of the metal ball or the angle reflector, and the reflection of a microwave absorbing material medium in an indoor measurement microwave darkroom is eliminated by a vertical headspace open space erection measurement mode, so that a measurement environment which is cleaner than that of the microwave darkroom is obtained; the isolation degree of the receiving and transmitting antenna is improved, the amplitude of a leakage signal of the receiving and transmitting antenna is smaller than the minimum metal ball echo amplitude of 300mm by 20dB, the isolation influence of the receiving and transmitting antenna is reduced, a receiver can linearly amplify during the pulse transmitting period by designing a proper transmitting pulse interval, a signal processing acquisition interval is set from the front edge of the transmitting pulse to the end of a pulse period, the full-range echo acquisition processing of the beginning of a '0' distance can be performed, the distance measurement blind area of a calibrating device is made to be '0', and the radar cross-sectional area measurement of a reflector erected in a short distance when the far-field distance of the calibrating device is within 1m can be realized; by automatically measuring cancellation and transmission isolation signal components in the measurement system error, the measurement influence of the mutual coupling of the transmission and reception antennas on the metal ball and the angle reflector is ignored.
Wherein establishing the reflector measurement system may comprise the steps of:
selecting a field open space with flat ground, wherein no building exists within 50m, three supporting rods and pull ropes are used for suspending metal balls or angle reflectors with different sizes, the angle reflectors are erected above horn mouths of a polarized transmitting antenna 2 and a polarized receiving antenna of the calibrating device, and the distance between the far field of the antenna of the calibrating device and the reflectors is
Wherein, D is the antenna caliber size of the calibrating device, about 0.12m, lambda is the radar working wavelength, X wave band takes 0.032m, C wave band takes 0.053m, S wave band takes about 0.1m, 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 from the antenna, so that the far field measurement requirement of a X, C, S wave band reflector can be met. The supporting rod is made of wood or plastic materials, the distance from the supporting rod to the calibrating device is 5m, and the pull rope is made of nylon thin wires, so that the supporting rod and the pull rope basically do not reflect electromagnetic waves, and the influence of peripheral reflection on a measuring result is eliminated. When the reflector is a metal sphere, a schematic diagram of the reflector measurement system is shown in fig. 9.
Radar cross-sectional area measurement of the reflector is measured according to the pulsed radar equation:
in the above, P r For radar to receive echo power, P t For radar emission peak power, G t For the gain of the radar transmitting antenna, G r Radar transmitting antenna gain, F t For calibrating the pattern factor of the antenna to the target radar of the instrument, F r Receiving antenna pattern factors for target radar to reach a calibration instrument, wherein L is system loss, and L a The radar cross section area of the reflector is denoted by sigma, the radar emission pulse width is denoted by tau, and the distance between the radar and the reflector is denoted by R;
setting a pulse radar constant:
σ＝C p P r R 4 (8)；
after the radar cross-sectional area of the reflector is measured, measuring the distance R from the center of the reflector to the antenna horn mouth of the calibrating device by using a measuring tool ruler j 。
Finally, according to the radar sectional area formula, measuring the echo power P of the reflector by a calibration device rj And calculating pulse radar constant, and establishing a reflector distance-radar cross-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; the reflectivity coefficient range of the reflector is matched with the weather radar measurement dynamic range.
The weather radar equation may be:
wherein: k 2 Is constant, Z is the reflectance coefficient; wherein:
wherein m is complex refractive index, cm wave band, temperature is 0-20 ℃, and when the particles are in water state, |K|is that 2 In the ice state, 0.93, K 2 ≈0.2；
Where θ is the radar azimuth beam width,
for pitch beamwidth, c is the speed of light.
Let weather radar constant:
combining the above, the reflectivity coefficient of the reflector in the weather radar is calculated as follows:
it should be noted that, in various embodiments of the present invention, the reflectance coefficient is also referred to as intensity, i.e., echo intensity.
In practice, the intensity and radar cross-sectional area are represented by standard reflectors such as metal balls or corner reflectors, the same reflectors appear as point targets in pulse radar measurement, and echo power represents the radar target cross-sectional area; and appears as a detection unit object in weather radar, which is equivalent to the total cross-sectional area of a water-containing particle filled in the detection unit, and the echo power represents the reflectivity coefficient (object intensity) of the detection unit object. Therefore, reflectors with the same radar cross-sectional area have different reflectivity coefficients under different weather radar single detection units, different beam widths and pulse widths.
The true value of the radar cross-sectional area of the reflectors such as the metal ball or the angle reflector corresponding to the weather radar echo intensity can be calculated through the method, namely the range-radar cross-sectional area-echo power parameter table is converted into the range-reflectivity coefficient-echo power parameter table.
Step S605, a calibration system for the transmission power of the simulation target is established, in the calibration system for the transmission power of the simulation target, the horn mouths of the polarized transmission antenna 2 and the polarized reception antenna of the calibration device are aligned to the antenna of the far-field calibration device, wherein the transmission power of the simulation target of the calibration device is adjusted according to the distance-reflectivity coefficient-echo power parameter table, so that the echo power corresponding to the transmission power of the simulation target received by the calibration device at a specific distance is equal to the echo power of the reflector received by the calibration device at the specific distance at the corresponding reflectivity coefficient, and the transmission power of the simulation target is recorded, thereby obtaining the distance-reflectivity coefficient-simulation target transmission power parameter table.
In the embodiment of the invention, the reflector is used for calibrating the emission power of the simulation target, and a distance-intensity (reflectivity coefficient) -simulation target emission power parameter table is established for calibrating weather radar by the calibrator. Specifically, the present invention relates to a method for manufacturing a semiconductor device. Step S605 may include the steps of:
A field open space with flat ground is selected, three supporting rods and a pulling rope are used for suspending a calibrator antenna, the calibrator antenna is erected above a horn mouth of a polarized transmitting antenna 2 and a polarized receiving antenna of the calibrating device, and the calibrator antenna is connected to a calibrator through a cable. The schematic diagram of the simulation target transmitting power calibration system is shown in fig. 10, the erection method of the simulation target transmitting power calibration system is similar to that of a metal ball (namely similar to that of fig. 9), a calibration instrument antenna is erected at the position where the metal ball is erected, the calibration instrument antenna is connected to a calibration instrument through a cable, and the insertion loss of the calibration instrument antenna is compared with that of the calibration instrument built-in antenna before calibration.
When the calibration device simulates the target transmitting power calibration, the calibration device transmits signals, the calibration device receives detection pulse signals transmitted by the calibration device, generates '0' distance simulation target signals, doppler frequency of the simulation target signals can be set to be more than 150hz, the Doppler frequency of the simulation target signals is far away from '0' Doppler frequency to transmit leakage signals and surrounding environment reflection signals, the '0' Doppler frequency leakage and clutter interference are filtered out by FFT Doppler filtering of the calibration device, the simulation target transmitting power of the simulation target signals is enabled to be more accurate in measurement, the echo power of the simulation target signals received by the calibration device under the simulation target transmitting power under the specific distance is enabled to be equal to the echo power of the reflector received by the calibration device under the specific distance under the corresponding reflectivity coefficient, and the simulation target transmitting power is recorded, wherein the simulation target transmitting power is namely the echo intensity of a metal ball at the corresponding bracket setting point distance.
When executing, will be apart from R j Echo power P of reflector received at rj Converted into a distance R b The echo power of the analog target signal of the calibration instrument received by the position is adjusted to adjust the analog target transmitting power of the analog target signal, so that the echo power of the calibration instrument received by the calibration device is P rb Calibrating simulated target transmitting power P corresponding to current radar reflecting sectional area sigma of reflector tb 。
When the erection position of the calibration instrument is different from the position of the reflector, the calibration instrument and the calibration device are mutually aligned, and the calibration instrument is converted by the following formula:
wherein: p (P) rj R is the echo power of the reflector j Is the distance between the reflector and the calibration device;
wherein: p (P) rb For calibrating the echo power of the instrument, R b The distance between the calibration instrument and the calibration device is the distance;
echo power corresponding to the simulated target transmitting power at the distance of the equivalent calibration instrument of the same reflector:
adjusting the simulated target transmit power P tb ＝K b P rb The echo power received by the calibration device is P rb Recording the simulated target transmitting power P tb The calibration of the reflector to the simulated target transmitting power can be realized;
on this basis, a range-reflectance coefficient-simulated target transmit power parameter table is established according to the following formula:
and step S606, calibrating the echo intensity true value of the weather radar according to the distance-reflectivity coefficient-simulated target transmitting power parameter table by using the calibration instrument after the transmitting channel and the receiving channel are calibrated.
In summary, the embodiment of the invention provides a concept of calibrating the true value calibration of the echo intensity of the weather radar by means of the calibration instrument, wherein the calibration instrument simulates the true value calibration of a target by means of the calibration device, the calibration device utilizes the objective reflection true value characteristics of the metal ball and the angle reflector and the high-precision measurement performance of the power density of the space radiation signal by means of the calibration device, and the method is characterized by objectively and accurately calibrating the transmission power of the simulated target of the calibration instrument and the true value reference of the echo intensity of the simulated target.
The calibration device performs density measurement on reflected power of the metal ball and/or reflectors with different size angles through high-precision measurement performance of power density of a space radiation signal, determines echo intensity truth value references of different reflectors corresponding to the distance through radar cross-sectional areas of different reflectors, matches the echo intensity range of the reflectors with the measurement dynamic range of weather radar echo intensity, and calibrates different intensity simulation target transmitting power through set reflector echo power calibration according to equal interval subareas to form intensity truth values and simulation target transmitting power truth value references of equal interval subareas.
The embodiment of the invention can be used for checking and calibrating the intensity calibration function, the dynamics, the resolution, the precision and the like of the calibration device, is one of the main functions of the calibration device, has the calibration precision which is 3-10 times better than the true value measurement precision of the echo intensity of the weather radar, can meet the basic requirements of the calibration device on the true value calibration of the echo intensity of the weather radar on the large dynamics, the high precision and the long-term stability of parameters, ensures that the calibration device bears the tasks of calibrating and calibrating the systematic error of the true value measurement parameter of the echo intensity of the weather radar when the true value measurement parameter of the echo intensity of the weather radar meets the requirements, bears the alarm task when the fluctuation error of the true value measurement parameter of the echo intensity of the weather radar exceeds the specified requirements, informs a guarantee personnel to check and maintain the weather radar, and calibrates the error of the system error of the true value measurement of the echo intensity of the weather radar after solving the problem of exceeding the fluctuation error, so that the data quality of the dynamic, the resolution, the precision, the long-term stability and the like of the true value measurement parameter of the echo intensity of the weather radar are guaranteed.
It should be noted that, in the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described as different from other embodiments, and identical and similar parts between the embodiments are all enough to 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", etc. indicate orientations or positional relationships based on those shown in the drawings, and are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or elements to be referred to must have a specific orientation, be configured 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" may be 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 order, and without necessarily being construed as indicating or implying any relative importance. Moreover, 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 one … …" does not exclude the presence of other like elements in a process, method, article, or terminal device comprising the element.
The foregoing has outlined rather broadly the more detailed description of the present application, and the detailed description of the principles and embodiments herein may be better understood as being a limitation on the present application. Also, various modifications in the details and application scope may be made by those skilled in the art in light of this disclosure, and all such modifications and variations are not required to be exhaustive or are intended to be within the scope of the disclosure.
Claims (9)
1. A calibration device for a calibration instrument, comprising:
the device comprises a host (1), a polarized transmitting antenna (2) and a polarized receiving antenna which are respectively connected with the host (1), wherein the 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 perpendicular to the horizontal plane;
the horizontal polarization receiving antenna (4) is arranged on the host, and the polarization direction of the horizontal polarization receiving antenna (4) is parallel to the horizontal plane;
the calibration method comprises the following steps: calibrating the gain power product of a transmitting antenna of the transmitting channel of the calibrating device, and transmitting a reference signal through the calibrated transmitting channel of the calibrating device so as to calibrate the performance of a receiving channel of the calibrating device;
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 calibrating device; 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 the reflector, the power density measurement dynamic range is used for controlling the transmitting power of the calibration device, and the transmitting power is sent to the standard gain horn so that the standard gain horn can radiate to a receiving antenna of the calibration device for calibration;
establishing a reflector measuring system in which the horn mouths of the polarized transmitting antenna (2) and the polarized receiving antenna of the calibrating device are both aligned with a far-field reflector; the calibration device measures the radar sectional area 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 sectional area-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; the reflectivity coefficient range of the reflector is matched with the weather radar measurement dynamic range;
establishing a simulation target transmitting power calibration system, wherein in the simulation target transmitting power calibration system, a polarization transmitting antenna (2) and a horn mouth of a polarization receiving antenna of the calibration device are aligned to an antenna of a far-field calibrator, wherein according to the distance-reflectivity coefficient-echo power parameter table, the simulation target transmitting power of the calibrator is adjusted so that the echo power corresponding to the simulation target transmitting power received by the calibration device at a specific distance is equal to the echo power of a reflector received by the calibration device at the specific distance at the corresponding reflectivity coefficient, and the simulation target transmitting power is recorded to obtain the distance-reflectivity coefficient-simulation target transmitting power parameter table;
and calibrating the echo intensity true value of the weather radar according to the distance-reflectivity coefficient-simulated target transmitting power parameter table by using the calibration instrument after the transmitting channel and the receiving channel are calibrated.
2. Calibration device according to claim 1, characterized in that the host (1) comprises:
the system 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 of 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 respectively connected with the crystal oscillator, the first phase-locked loop, the second DDS, the H signal processing module and the V signal processing module;
the first phase-locked loop is connected with the transmitter sequentially through a first amplifier, a first power divider and a first mixer, the first mixer is connected with the first signal generator 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 a 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.
4. The calibration device 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 sequentially connected;
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. The method for calibrating the true value of the echo intensity of the weather radar is characterized by comprising the following steps of:
calibrating the gain power product of a transmitting antenna of a transmitting channel of the calibrating device according to any one of claims 1-4, transmitting a reference signal through the calibrated transmitting channel of the calibrating device to calibrate the performance of a receiving channel of the calibrating device;
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 calibrating device; 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 the reflector, the power density measurement dynamic range is used for controlling the transmitting power of the calibration device, and the transmitting power is sent to the standard gain horn so that the standard gain horn can radiate to a receiving antenna of the calibration device for calibration;
Establishing a reflector measuring system in which the horn mouths of the polarized transmitting antenna (2) and the polarized receiving antenna of the calibrating device are both aligned with a far-field reflector; the calibration device measures the radar sectional area 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 sectional area-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; the reflectivity coefficient range of the reflector is matched with the weather radar measurement dynamic range;
establishing a simulation target transmitting power calibration system, wherein in the simulation target transmitting power calibration system, a polarization transmitting antenna (2) and a horn mouth of a polarization receiving antenna of the calibration device are aligned to an antenna of a far-field calibrator, wherein according to the distance-reflectivity coefficient-echo power parameter table, the simulation target transmitting power of the calibrator is adjusted so that the echo power corresponding to the simulation target transmitting power received by the calibration device at a specific distance is equal to the echo power of a reflector received by the calibration device at the specific distance at the corresponding reflectivity coefficient, and the simulation target transmitting power is recorded to obtain the distance-reflectivity coefficient-simulation target transmitting power parameter table;
Calibrating the echo intensity true value of the weather radar according to the distance-reflectivity coefficient-simulated target transmitting power parameter table by using the calibration instrument after the transmitting channel and the receiving channel are calibrated;
the calibration of the gain power product of the transmitting antenna of the transmitting channel of the calibration device comprises 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 calibrating device with the standard gain horn antenna;
the transmitting power of the calibrating device is P j Through the radiation of the polarized transmitting antenna (2), the antenna gain G j The method comprises the steps of carrying out a first treatment on the surface of the The distance between the standard gain horn antenna and the horn mouth of the polarized transmitting antenna (2) is R c The space radiation power density of the standard gain horn antenna is D j The caliber area of the standard gain horn antenna is A c The power meter measures the power P cj ；
The power density of the space radiation signal received by the standard gain horn antenna is as follows:
the power meter measures the power as follows:
the gain power product of the transmitting antenna of the transmitting channel of the calibrating device is as follows:
6. the method of claim 5, wherein calibrating the power density measurement performance of the spatial radiation signal with the calibration device receiving channel comprises the steps of:
Transmitting a signal through the calibration means to the reflector where the spatial power density is:
(4) Wherein: p (P) tj G tj Gain power product of transmitting antenna for transmitting channel of the calibrating device, calibrated; r is R j For the distance between the center of the reflector and the horn mouth of the receiving antenna of the calibrating device, the radiation signal of the calibrating device is received, excited and reflected on the surface of the reflector, part of the reflected signal enters the receiving antenna of the calibrating device, the reflected signal is described by the radar cross-sectional area sigma of the reflector, and the echo power density reflected by the reflector on the horn mouth surface of the receiving antenna of the calibrating device is as follows:
7. method according to claim 6, characterized in that a reflector measuring system is established in which the horn mouths of the calibrating device polarized transmitting antenna (2) and polarized receiving antenna are both directed towards the far-field reflector; the calibration device measures the radar sectional area of the reflector according to a pulse radar equation, and measures the echo power of the reflector under 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 support rods and pull ropes, erecting the space above horn mouths of a polarized transmitting antenna (2) and a polarized receiving antenna of the calibrating device, wherein the distance between the horn mouths and a far-field reflector is as follows 
Wherein D is the caliber size of the horn mouth, and lambda is the working wavelength of the radar;
radar cross-sectional area measurement of the reflector is measured according to the pulsed radar equation:
in the above, P r For radar to receive echo power, P t For radar emission peak power, G t For the gain of the radar transmitting antenna, G r For radar transmitting antenna gain, F t For calibrating the pattern factor of the antenna to the target radar of the instrument, F r Receiving antenna pattern factors for target radar to reach a calibration instrument, wherein L is system loss, and L a The radar cross section area of the reflector is denoted by sigma, the radar emission pulse width is denoted by tau, and the distance between the radar and the reflector is denoted by R;
setting a pulse radar constant:
σ＝C p P r R 4 L a (8)；
after the radar cross-sectional area of the reflector is measured, measuring the distance R from the center of the reflector to the bell mouth by a measuring tool ruler j Measuring the echo power P of the reflector by means of the calibration device rj 。
8. The method of claim 7, wherein the calibrating means calculates a reflectance coefficient of the reflector in the weather radar based on a radar cross-sectional area of the reflector, comprising:
the weather radar equation is:
wherein: k 2 Is constant, Z is the reflectance coefficient; wherein:
wherein m is complex refractive index, cm wave band, temperature is 0-20 ℃, and when the particles are in water state, |K|is that 2 In the ice state, 0.93, K 2 ≈0.2；
Wherein: θ is the radar azimuth beam width,
the pitch angle beam width, c is the speed of light;
let weather radar constant:
combining the above, the reflectivity coefficient of the reflector in the weather radar is calculated as follows:
9. the method according to claim 8, characterized in that a simulated target transmit power calibration system is established, in which the calibration device polarized transmit antenna (2) and the horn mouth of the polarized receive antenna are both aimed at the antenna of the far field calibrator, wherein the simulated target transmit power of the calibrator is adjusted according to the distance-reflectivity coefficient-echo power parameter table, so that the echo power corresponding to the simulated target transmit power received by the calibration device at a specific distance is equal to the echo power of the reflector received by the calibration device at the specific distance at the corresponding reflectivity coefficient, and the simulated target transmit power is recorded, resulting in a distance-reflectivity coefficient-simulated target transmit power parameter table, comprising the steps of:
a field open space with flat ground is selected, three supporting rods and a pulling rope are used for suspending a calibrator antenna, the calibrator antenna is erected above a horn mouth of a polarized transmitting antenna (2) and a polarized receiving antenna of the calibration device, and the calibrator antenna is connected to a calibrator through a cable;
Distance R j Echo power P of reflector received at rj Converted into a distance R b The echo power of the calibrator received by the calibration device is P, and the simulated target transmitting power of the simulated target signal is adjusted to make the echo power of the calibrator received by the calibration device be P rb Calibrating simulated target transmitting power P corresponding to current radar reflecting sectional area sigma of reflector tb ：
When the erection position of the calibration instrument is different from the position of the reflector, the calibration instrument and the calibration device are mutually aligned, and the calibration instrument is converted by the following formula:
wherein: p (P) rj R is the echo power of the reflector j Is the distance between the reflector and the calibration device;
wherein: p (P) rb For calibrating the echo power of the instrument, R b The distance between the calibration instrument and the calibration device is set;
adjusting the simulated target transmit power P tb ＝K b P rb The echo power received by the calibration device is P rb Recording the simulated target transmitting power P at this time tb A range-reflectivity coefficient-simulated target transmit power parameter table is established according to the following equation:
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