CN112415520B - Foundation microwave radiometer system based on variable-temperature source antenna aperture surface calibration and calibration method thereof - Google Patents
Foundation microwave radiometer system based on variable-temperature source antenna aperture surface calibration and calibration method thereof Download PDFInfo
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- CN112415520B CN112415520B CN202011213565.XA CN202011213565A CN112415520B CN 112415520 B CN112415520 B CN 112415520B CN 202011213565 A CN202011213565 A CN 202011213565A CN 112415520 B CN112415520 B CN 112415520B
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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
- G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
- G01S13/88—Radar or analogous systems specially adapted for specific applications
- G01S13/95—Radar or analogous systems specially adapted for specific applications for meteorological use
- G01S13/951—Radar or analogous systems specially adapted for specific applications for meteorological use ground based
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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
- G01S7/4052—Means for monitoring or calibrating by simulation of echoes
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- G—PHYSICS
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- 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
- G01S7/406—Means for monitoring or calibrating by simulation of echoes using internally generated reference signals, e.g. via delay line, via RF or IF signal injection or via integrated reference reflector or transponder
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Abstract
The invention provides a foundation microwave radiometer system based on variable-temperature source antenna aperture calibration and a calibration method thereof, wherein the system comprises the following steps: the antenna comprises an antenna reflecting surface, a variable-temperature calibration source and an intermediate link, and comprises a polarization separation device, a feed source, a multi-channel receiver and a lower computer. Wherein, the variable temperature calibration source is used for providing different temperatures in the calibration process. The system accurately controls the antenna port surface to point to the temperature change source and controls the timely temperature of the temperature change source through the lower computer during calibration, so that voltage data of a receiving channel at least two temperature change points are received, and a corresponding calculation formula is carried out to obtain an applicable calibration equation.
Description
Technical Field
The invention relates to the field of ground microwave remote sensing equipment, in particular to a ground microwave radiometer system based on variable temperature source antenna aperture calibration and a calibration method thereof.
Background
The ground microwave radiometer is ground microwave remote sensing equipment which utilizes microwave signals of atmospheric radiation transmitted from various heights to judge the change of atmospheric temperature and humidity, and has an important detection function on medium and small scale weather phenomena, such as storm, lightning, heavy rainfall, fog, freezing and boundary layer turbulence. The research of temperature, humidity and liquid water of a troposphere section, weather and climate models of a foundation microwave radiometer, satellite tracking (GPS, galileo) wet/dry delay and humidity profiles, near forecast atmospheric stability (disastrous weather detection), temperature inversion detection, fog and air pollution, absolute calibration of a cloud radar and wet/dry delay correction VLBI have important application and become an important detection means outside a sounding balloon and a weather radar. The ground-based microwave radiometer has independent working capacity, can work under almost various environmental conditions, is suitable for an automatic weather station, is commonly used for inverting a complete atmospheric profile, and completely stores inverted data and original data, and can provide a complete custom or global standard algorithm.
The voltage signal telemetered by the foundation microwave radiometer has a certain relation with the target signal thereof, and the corresponding relation can be accurately determined by a proper calibration method. The calibration operation of the ground-based microwave radiometer is a basic method for determining target characteristics and data acquisition so as to obtain a linear relation equation of the target characteristics and the data acquisition.
An external liquid nitrogen cold source is required to be additionally arranged for the conventional antenna aperture surface calibration of a general foundation radiometer, referring to fig. 1, the antenna is enabled to be aligned with the liquid nitrogen cold source and the internal normal temperature source through the rotation of the antenna, two points of received data are obtained, and a calibration equation is obtained through complex temperature transformation. The liquid nitrogen cold source is easy to frost and drop on the surface of the device under a high-humidity environment, so that the calibration precision of the device is affected. In addition, the foundation microwave radiometer is used in the ground environment, an open and high land (such as a hill) is selected, a father observes the ground without shielding, and the ground microwave radiometer is unattended for a long time. Many occasions cannot meet the basic condition of liquid nitrogen.
Disclosure of Invention
The invention aims to provide a foundation microwave radiometer system based on variable-temperature source antenna aperture calibration and a calibration method thereof, and aims to solve the problems that the conventional antenna aperture calibration technology of the existing foundation radiometer needs complicated liquid nitrogen cold source calculation, is easy to generate errors and is difficult to meet basic conditions of liquid nitrogen.
In order to achieve the above object, the present invention provides a ground-based microwave radiometer system based on variable temperature source antenna aperture calibration, comprising:
the antenna reflecting surface is used for receiving water vapor, oxygen and/or microwave radiation signals of a specific target in the atmosphere above the earth surface;
the temperature changing source is used for providing different temperatures required by the antenna reflecting surface in the calibration process;
the intermediate link and K, V multichannel receiver comprises a polarization separation device and a feed source, wherein the polarization separation device is used for processing the microwave radiation signals to perform frequency division detection to obtain a first wave band signal and a second wave band signal, and the feed source is used for respectively sending the first wave band signal and the second wave band signal to a K multichannel receiver and a V multichannel receiver; and
and the lower computer is used for receiving data received by the K multichannel receiver and the V multichannel receiver, accurately controlling the antenna opening surface of the antenna reflecting surface to point to the temperature changing source and controlling the temperature of the temperature changing source.
Preferably, the device further comprises a driving mechanism for driving the antenna reflecting surface to rotate under the control of the lower computer.
Preferably, the variable temperature calibration source includes: the heating plate is arranged under the sharp cone array, the wave-transmitting window is arranged above the sharp cone array, the sharp cone array is arranged on the heating plate, the metal inner frame is U-shaped and is matched with the wave-transmitting window to cover the sharp cone array and the heating plate, the heat-insulating layer is arranged on the outer side of the metal inner frame, and the metal outer frame is arranged on the outer side of the heat-insulating layer.
Preferably, the pointed cone of the pointed cone array in the variable-temperature calibration source is of a high-thermal-conductivity silicon carbide composite material structure, and the outer surface of the pointed cone array is additionally provided with a wave-transparent protective material.
Preferably, the sensor in the temperature-varying calibration source is arranged in the pointed cone.
Preferably, the multi-band signal comprises a first band signal and a second band signal; the multi-channel receiver comprises a K-channel receiver and a V-channel receiver, and the feed source is used for respectively sending the first wave band signal and the second wave band signal to the K-channel receiver and the V-channel receiver; the lower computer is used for receiving data received by the K channel receiver and the V channel receiver.
The invention also provides a calibration method of the foundation microwave radiometer system based on the calibration of the mouth surface of the variable-temperature source antenna, which is used for calibrating by applying the foundation microwave radiometer system based on the calibration of the mouth surface of the variable-temperature source antenna and comprises the following steps:
step 1: the variable-temperature calibration source performs antenna aperture surface calibration at a first high temperature:
the lower computer controls the antenna reflecting surface to point to the built-in variable temperature calibration source, and the lower computer performs heating control on the variable temperature calibration source to ensure that the variable temperature calibration source is constant at a first high temperature value Th1 and directly reads corresponding detection voltage Vh1 and the first high temperature value Th1 of the multichannel receiver;
step 2: the variable-temperature calibration source performs antenna aperture surface calibration at a second high temperature:
the antenna reflecting surface still points to the built-in variable temperature calibration source, the lower computer performs heating control on the variable temperature calibration source to enable the variable temperature calibration source to be constant at a second Gao Wenzhi Th2, and corresponding multi-channel receiver detection voltage Vh2 and high temperature Th2 are directly read;
and step 3: determining the coefficients of a scaling equation according to the results of the steps 1 and 2:
wherein K is a scaling gain coefficient; g is a full-link brightness temperature voltage conversion coefficient; l is the insertion loss of the intermediate link;
obtaining a scaling equation:
Ta＝K×V+b；
wherein Ta is the target brightness temperature; k is a gain coefficient; b is the equivalent brightness temperature of the receiving system with the intermediate link, and V is the telemetering voltage value;
wherein T0 is normal temperature; trec is the receiver equivalent bright temperature.
The variable temperature source is a key part, adopts a high-thermal-conductivity silicon carbide composite material structure, and is added with a wave-transparent protective material on the outer surface, so that the full-wave-band radiance is over 0.999 while the rapid temperature rise is ensured, and the high-precision built-in temperature measurement sensor fully reflects the temperature of the pointed cone radiator.
Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages and positive effects:
1) The calibration method avoids the calibration complexity of an external liquid nitrogen cold source, and the introduced frosting, water drop influence and equivalent calculation errors.
TC＝TE-0.00825×(1013.25-PE)
( TC: the liquid nitrogen cold source has equivalent temperature; TE: the surface ambient temperature; PE: atmospheric pressure of earth surface )
2) The linearity of the system can also be verified through a calibration test of multiple temperature points.
Drawings
FIG. 1 is an external calibration of the cold and heat sources of the antenna aperture of a conventional ground-based microwave radiometer;
FIG. 2 is a view of the calibration of the variable temperature source antenna aperture of the foundation microwave radiometer according to the present invention;
FIG. 3 is a structure of a variable temperature source, a key component provided by the present invention;
FIG. 4 is a timing setting for a ground-based microwave radiometer according to the present invention;
FIG. 5 is a schematic diagram of a conventional linearity measurement;
FIG. 6 is a timing diagram for linearity measurement of a microwave radiometer based on the present invention.
Detailed Description
While the embodiments of the present invention will be described in detail and fully hereinafter with reference to the accompanying drawings, it is to be understood that the invention is not limited to the details of the embodiments, but may be embodied in various forms without departing from the spirit or scope of the present invention.
For the convenience of understanding the embodiments of the present invention, the following description will be further explained by taking specific embodiments as examples with reference to the drawings, and the embodiments are not to be construed as limiting the embodiments of the present invention.
The present embodiment provides a foundation microwave radiometer system based on calibration of an antenna aperture surface with varying temperature sources and a calibration method thereof, specifically, referring to fig. 2, the system includes:
the antenna reflecting surface is used for receiving water vapor, oxygen and/or microwave radiation signals of a specific target in the atmosphere above the earth surface;
the variable temperature calibration source is used for providing different temperatures required by the antenna reflecting surface in the calibration process;
the middle link comprises a polarization separation device and a feed source, wherein the polarization separation device is used for processing microwave radiation signals to perform frequency division detection to obtain multiband signals with preset waveband numbers and is fed by the feed source;
a multi-channel receiver for receiving a multi-band signal from the feed; and
and the lower computer is used for receiving the data received by the multi-channel receiver, accurately controlling the antenna opening surface of the antenna reflecting surface to point to the variable-temperature calibration source and controlling the temperature of the variable-temperature calibration source.
Therein, referring to fig. 2, the intermediate link part and the receiver part of the system are arranged in a constant temperature receiving system (temperature T0). In addition, the system also comprises a driving mechanism which is used for driving the antenna reflecting surface to rotate under the control of the lower computer, so that the antenna opening surface faces to the required direction.
Referring to fig. 3, the variable temperature calibration source provided in this embodiment includes: wave-transparent window 31, pointed cone array 32, heating plate 33, metal inner frame 34, insulating layer 35 and metal outer frame 36. The heating plate 33 is disposed below the pointed cone array, the wave-transmitting window 31 is disposed above the pointed cone array 32, the pointed cone array 32 is disposed on the heating plate 33, the metal inner frame 34 is in a U-shaped form and is matched with the wave-transmitting window 31 to cover the pointed cone array 32 and the heating plate 33, the heat-insulating layer 35 is disposed on the outer side of the metal inner frame 34, and the metal outer frame 36 is disposed on the outer side of the heat-insulating layer 35. The pointed cone of the pointed cone array 32 in the variable temperature calibration source is of a high-thermal-conductivity silicon carbide composite material structure, and a wave-transparent protective material is additionally arranged on the outer surface of the pointed cone array. The sensors 37 in the variable temperature calibration source are located within the tip cones, where it is noted that a sensor is located within each tip cone. Compared with the conventional normal temperature source (the sensor is of a surface type, namely the sensor is arranged outside the pointed cone, the wave-transmitting material is not arranged on the outer surface of the pointed cone, and the normal temperature source is not provided with a heating plate, a metal inner frame and a heat insulation layer), the embedded sensor has more accurate temperature sensing performance.
Further, the processed multiband signal in the embodiment includes a first waveband signal and a second waveband signal; correspondingly, referring to fig. 2 again, the multi-channel receiver includes a K-channel receiver and a V-channel receiver, where the feed source is divided into a K-band feed source and a V-band feed source, and is used to send the first band signal and the second band signal to the K-channel receiver and the V-channel receiver, respectively; the lower computer is used for receiving data received by the K channel receiver and the V channel receiver, forwarding the data to the ground-based radiometer supporting platform, and receiving an operation instruction from the ground-based radiometer supporting platform during calibration operation.
The embodiment also provides a calibration method of the foundation microwave radiometer system based on variable temperature source antenna aperture surface calibration, which is used for calibration by applying the foundation microwave radiometer system based on variable temperature source antenna aperture surface calibration and comprises the following steps:
step 1: the variable-temperature calibration source calibrates the antenna port face with the first high temperature:
the lower computer controls the antenna reflecting surface to point to a built-in variable temperature calibration source, heats and controls the variable temperature calibration source to be constant at a first high temperature value Th1, and directly reads corresponding detection voltage Vh1 and the first high temperature value Th1 of the multi-channel receiver;
step 2: and (3) carrying out second high-temperature antenna aperture surface calibration by the variable-temperature calibration source:
the antenna reflecting surface still points to the built-in variable temperature calibration source, the lower computer performs heating control on the variable temperature calibration source to enable the variable temperature calibration source to be constant at a second Gao Wenzhi Th2, and corresponding multi-channel receiver detection voltage Vh2 and high temperature Th2 are directly read;
and step 3: determining the coefficients of a scaling equation according to the results of the steps 1 and 2:
wherein K is a scaling gain coefficient; g is a full-link brightness temperature voltage conversion coefficient; l is the intermediate link insertion loss;
obtaining a scaling equation:
Ta＝K×V+b；
wherein Ta is the target brightness temperature; k is a gain coefficient; b is the equivalent brightness temperature of the receiving system with the intermediate link, and V is the telemetering voltage value;
wherein T0 is normal temperature; and Trec is the equivalent brightness temperature of the receiver.
The ground-based microwave radiometer system is arranged on the ground surface, is mainly used for receiving water vapor and oxygen of the atmosphere above the ground surface or microwave radiation signals of a specific target, the signals are collected through an antenna port surface, are transferred into passive components such as a feed source, a waveguide structural member and an isolation component, then enter a radiometer microwave receiver system to complete receiving, amplification, frequency division detection and AD data acquisition processes, and finally, the atmosphere temperature and humidity profile or the specific target characteristic is obtained through channel data inversion.
The foundation radiometer is replaced by a variable temperature source at the traditional built-in normal temperature source, the calibration process does not need external cold source cooperation, the calibration process is completed only by accurately controlling the temperature of the variable temperature source and carrying out data acquisition and method operation for multiple times, complex liquid nitrogen cold source calculation is not needed, and unnecessary errors are eliminated. The foundation microwave radiometer thoroughly solves the problem of external field liquid nitrogen calibration of the original radiometer and is suitable for timely calibration of all application occasions.
The calibration operation process of the ground-based microwave radiometer system will be described in detail below with reference to specific application examples.
Application example 1: calibration operation of foundation microwave radiometer
In principle, system calibration is required before starting up when any site of the foundation microwave radiometer moves, and the basic requirement of the system calibration is to determine the corresponding relation of converting 0-level voltage data into 1-level brightness temperature data. In general, radiometer receivers are designed with a linearity requirement of 99.99%, so that two-point external calibration determines the calibration equation: ta = K × V + b.
After the foundation microwave radiometer is started or in the intermediate process of telemetering the foundation microwave radiometer, the constant temperature receiving system stably works for a period of time (normally monitors T) 0 The value fluctuation was less than 0.03 ℃). The foundation radiometer main control computer interface sends an instruction to request the lower computer to guide the foundation microwave radiometer to enter a calibration state, and the foundation radiometer lower computer immediately responds to the instruction request and guides the pitching stepping motor to rotate the antenna port to face downwards to point to the temperature-variable source right below, as shown in fig. 2.
The temperature setting Th1 (more than or equal to the actual remote measuring value of the current temperature-varying source sensor; the default value is the current remote measuring value), th2 (more than Th1; the default value is the highest temperature value of the temperature-varying source) and the maintenance time T of the calibration section of the temperature-varying source corresponding to two points appear on the main control computer interface of the foundation radiometer; as shown in fig. 4.
And the lower computer performs heating control on the variable temperature source to ensure that the variable temperature source is constant at a temperature value Th1, keeps the T time period, directly reads the detection voltage Vh1i of the corresponding receiver, and uploads the detection voltage telemetering signals and the temperature telemetering value to the main control computer of the platform.
After completing the reading of the voltage telemetry data for the T period at the Th1 temperature; and the lower computer automatically heats the variable temperature source according to the maximum heating mode and the automatic constant temperature keeping program to enable the variable temperature source to reach the variable temperature Th2 in the fastest time, and keeps the constant temperature.
And when the constant temperature keeping state is automatically judged, directly keeping the constant temperature keeping state for a time period T, reading the detection voltage Vh2i of the corresponding receiver, and uploading the detection voltage telemetering signal and the temperature telemetering value to a main control computer of the platform.
After the lower computer finishes the operation, the temperature of the variable temperature source is released to keep control before a new main control computer instruction is not provided, so that the temperature of the base is slowly reduced to the outside normal temperature. (considering the complexity of manufacture, the temperature changing source does not add the refrigeration operation of lower temperature changing, thus only performing the calibration operation of upper temperature changing; and the temperature changing source for adding the refrigeration control can realize the calibration operation of lower temperature changing).
Meanwhile, the main control computer determines all the telemetering detection voltage average values in a time period as calibration voltages according to state instructions of the lower computer, and the telemetering average value of the temperature sensor of the temperature source changing the temperature in the corresponding time period is determined as corresponding brightness temperature.
Wherein, N1, N2: measuring voltage telemetering and reading times by a temperature sensor at T time interval and variable temperature Th1 state; n3, N4: t time period, variable temperature Th2 state detection voltage telemetering and temperature sensor telemetering and reading times.
And the main control computer obtains the coefficient K, b of each channel according to the programmed scaling equation coefficient formula and the voltage value and the temperature value of the corresponding channel.
Accordingly, remote sensing level 1 data is formed according to a new scaling equation T = K multiplied by V + b.
Application example 2: linearity measuring operation for foundation microwave radiometer
In general, the radiometer receiver is designed with the requirement of 99.99% of linearity, so that the link design receiving amplification is in a linear back-off state and the detection is in a strict square-law detection within the dynamic range of the radiometer receiver.
But linearity measurement is always difficult and complete machine testing is more difficult. In many application occasions, a high-precision adjustable attenuator is inserted between the input end of a receiver and a low-temperature calibration source for equivalent measurement, as shown in fig. 5, the attenuation of the middle precision adjustable attenuator is changed, namely different additional link insertion loss is added between the receiver and the calibration source, the input signal (radiation brightness temperature) in front of the receiver is equivalently and indirectly changed, and finally the linearity index of the receiver is reflected by the change and comparison of the telemetering detection voltage value of the receiver, so that the linearity of the whole radiometer system in a dynamic range is indirectly reflected. Although this measurement can effectively measure the linearity, it also introduces the attenuator error and inaccuracy problems (such as surface frosting) caused by long-time calibration of the cold source.
When the system needs the foundation radiometer to measure the linearity, no external cooperation is needed, only the main control computer interface of the foundation radiometer sends an instruction, the lower computer is required to guide the foundation microwave radiometer to enter a linearity test state, the lower computer of the foundation radiometer immediately responds to the instruction requirement, and the pitching stepping motor in the driving mechanism is controlled to rotate the antenna port to point downwards to the directly-downward temperature changing source, as shown in figure 2.
Setting Th1 (more than or equal to the actual remote value of the current temperature-changing source sensor; default value is the current remote value), delta Ta (temperature-changing stepping value: the minimum value is 1K, the maximum value is (Thh-Th 1)/2 (equivalent to 3-point measurement), default value is 10K) and calibration section maintenance time T corresponding to the initial value of the temperature-changing source on the main control computer interface of the foundation radiometer; as shown in fig. 6.
And the lower computer performs heating control on the variable temperature source to ensure that the variable temperature source is constant at the initial temperature value Th1, keeps the T time period, directly reads the detection voltage Vh1i of the corresponding receiver, and uploads the detection voltage telemetering signals and the temperature telemetering value to the main control computer of the platform.
After completing the reading of the T period voltage telemetry data at the Th1 temperature; and the lower computer automatically heats the variable temperature source according to the maximum heating mode and the automatic constant temperature keeping program to enable the variable temperature source to reach the variable temperature Th1+ delta Ta (recorded as Th 2) in the fastest time, and keeps the constant temperature.
And when the constant temperature keeping state is automatically judged, directly keeping the constant temperature keeping state for a time period T, reading the detection voltage Vh2i of the corresponding receiver, and uploading the detection voltage telemetering signal and the temperature telemetering value to a main control computer of the platform.
After completing the reading of the voltage telemetry data for a period of time T at the Th2 temperature; and the lower computer automatically heats the variable temperature source according to the maximum heating mode and the automatic constant temperature keeping program to enable the variable temperature source to reach the variable temperature Th1+2 delta Ta (recorded as Th 3) in the fastest time, and keeps the constant temperature.
And when the constant temperature keeping state is automatically judged, directly keeping the constant temperature keeping state for a time period T, reading the detection voltage Vh3i of the corresponding receiver, and uploading the detection voltage telemetering signal and the temperature telemetering value to a main control computer of the platform.
And repeating the steps, the lower computer finishes the detection voltage T time period Vhni sampling of the nth receiver closest to the maximum temperature point Thh of the temperature changing source, and the detection voltage telemetering signal and the temperature telemetering value are uploaded to the main control computer of the platform.
And after finishing all operations, the lower computer releases the control on the temperature of the temperature changing source to slowly reduce the temperature to the external normal temperature before a new main control computer instruction is not provided.
Similarly, the main control computer determines the measured voltage at each temperature point according to the state instruction of the lower computer and the average value of all the telemetering detection voltages in a time period, determines the telemetering average value of the temperature sensor of the corresponding time period variable temperature source as the corresponding bright temperature, and calculates each section gain coefficient Ki according to the telemetering range sequentialization of two adjacent temperature points:
in addition, the main control computer calculates a standard gain coefficient K according to the data of the lower computer in the initial value Th1 state and the data of the lower computer in the final Thn state:
the maximum deviation, denoted as Δ Kmax, is obtained by comparing the difference between K and each of K1, K2, …, K (n-1), and its linearity is:
L＝(1-ΔK max/K)×100％。
the foundation radiometer is replaced by a variable temperature source at the traditional built-in normal temperature source, the calibration process does not need external cold source cooperation, the calibration process is completed only by accurately controlling the temperature of the variable temperature source and carrying out data acquisition and method operation for many times, complicated liquid nitrogen cold source calculation is not needed, and unnecessary errors are eliminated.
In addition, the foundation microwave radiometer is used in the ground environment, an open and high land (such as a hill) is selected, a father observes the ground without shielding, and the ground microwave radiometer is unattended for a long time. The foundation microwave radiometer of the invention thoroughly solves the external field liquid nitrogen calibration problem of the original radiometer and is suitable for the timely calibration of all application occasions.
The above description is only an embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be able to make modifications or substitutions within the technical scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (6)
1. A ground-based microwave radiometer system based on variable temperature source antenna aperture face calibration is characterized by comprising:
the antenna reflecting surface is used for receiving water vapor, oxygen and/or microwave radiation signals of a specific target in the atmosphere above the earth surface;
the variable-temperature calibration source is used for providing different temperatures required by the antenna reflecting surface in the calibration process;
the middle link comprises a polarization separation device and a feed source, wherein the polarization separation device is used for processing the microwave radiation signals to perform frequency division detection to obtain multiband signals with preset waveband numbers and feeding the multiband signals by the feed source;
a multi-channel receiver for receiving a multi-band signal from the feed; and
the lower computer is used for receiving data received by the multi-channel receiver, accurately controlling the antenna opening surface of the antenna reflecting surface to point to the variable-temperature calibration source and controlling the temperature of the variable-temperature calibration source;
the pointed cone of the pointed cone array in the variable temperature calibration source is of a high-thermal-conductivity silicon carbide composite material structure, and a wave-transparent protective material is additionally arranged on the outer surface of the pointed cone array;
when the lower computer performs heating control on the variable-temperature calibration source, the initial temperature is controlled to be Th1, the variable-temperature stepping value is delta Ta, the calibration section maintaining time of each temperature point is T, the highest temperature point Thh corresponds to the nth receiver detection voltage Vhn, wherein n is more than or equal to 2, and each section gain coefficient Ki is calculated according to the telemetering range serialization of two adjacent temperature points:
then the standard gain factor K is updated to be:
comparing the difference between K and K1, K2, …, K (n-1) to obtain the maximum deviation, and recording the maximum deviation as delta Kmax, then updating the linearity as follows:
L＝(1-ΔK max/K)×100％。
2. the variable temperature source antenna aperture-surface calibration-based ground-based microwave radiometer system of claim 1, further comprising a driving mechanism for driving the rotation of the antenna reflecting surface under the control of the lower computer.
3. The variable temperature source antenna aperture-surface-calibration-based ground-based microwave radiometer system of claim 1, wherein the variable temperature calibration source comprises: wave-transmitting window, sharp awl array, hot plate, metal inner frame, insulating layer and metal frame, the below of sharp awl array is equipped with the hot plate, wave-transmitting window locates the top of sharp awl array, sharp awl array set up in on the hot plate, the metal inner frame is "U" type and cooperation wave-transmitting window cladding sharp awl array and hot plate, the insulating layer set up in the metal inner frame outside, the metal frame is located the insulating layer outside.
4. The variable temperature source antenna aperture-surface-based calibrated ground-based microwave radiometer system of claim 1, wherein the sensor of the variable temperature calibration source is disposed within the tip cone.
5. The variable temperature source antenna aperture-surface calibration based ground-based microwave radiometer system of claim 1, wherein the multi-band signal comprises a first band signal and a second band signal; the multi-channel receiver comprises a K-channel receiver and a V-channel receiver, and the feed source is used for respectively sending the first wave band signal and the second wave band signal to the K-channel receiver and the V-channel receiver; the lower computer is used for receiving data received by the K channel receiver and the V channel receiver.
6. A calibration method of a foundation microwave radiometer system based on variable-temperature source antenna aperture calibration is characterized in that the foundation microwave radiometer system based on variable-temperature source antenna aperture calibration of any one of claims 1 to 5 is applied for calibration, and the calibration method comprises the following steps:
step 1: the variable-temperature calibration source performs antenna aperture surface calibration at a first high temperature:
the lower computer controls the antenna reflecting surface to point to the built-in variable temperature calibration source, and the lower computer performs heating control on the variable temperature calibration source to ensure that the variable temperature calibration source is constant at a first high temperature value Th1 and directly reads corresponding detection voltage Vh1 and the first high temperature value Th1 of the multichannel receiver;
step 2: the variable-temperature calibration source performs antenna aperture surface calibration at a second high temperature:
the antenna reflecting surface still points to the built-in variable temperature calibration source, the lower computer performs heating control on the variable temperature calibration source to enable the variable temperature calibration source to be constant at a second Gao Wenzhi Th2, and corresponding multi-channel receiver detection voltage Vh2 and high temperature Th2 are directly read;
and step 3: determining the coefficients of a scaling equation according to the results of the steps 1 and 2:
wherein K is a scaling gain coefficient; g is a full-link brightness temperature voltage conversion coefficient; l is the intermediate link insertion loss;
obtaining a scaling equation:
Ta＝K×V+b；
wherein Ta is the target brightness temperature; k is a gain coefficient; b is the equivalent brightness temperature of the receiving system with the intermediate link, and V is the telemetering voltage value;
here T 0 Is at normal temperature; trec is the equivalent brightness temperature of the receiver;
when the lower computer performs heating control on the variable-temperature calibration source, the initial temperature is controlled to be Th1, the variable-temperature stepping value is delta Ta, the calibration section maintaining time of each temperature point is T, the highest temperature point Thh corresponds to the nth receiver detection voltage Vhn, wherein n is more than or equal to 2, and each section gain coefficient Ki is calculated according to the telemetering range serialization of two adjacent temperature points:
then the standard gain factor K is updated to be:
comparing the difference between K and K1, K2, …, K (n-1) to obtain the maximum deviation, and marking as delta Kmax, then updating the linearity as:
L＝(1-ΔK max/K)×100％。
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