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Four-point calibration method based on waveguide switch

A waveguide switch and four-point calibration technology, which is applied in the field of four-point calibration based on waveguide switches, can solve the problems of real-time calibration difficulties and the inability to realize the standard cold air-external calibration source on the surface of the antenna mouth, and achieve guaranteed The effect of precision

Inactive Publication Date: 2020-08-18
SHANGHAI SPACEFLIGHT INST OF TT&C & TELECOMM
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Compared with the space-based radiometer system, the ground-based radiometer cannot realize the standard cold air-external calibration source at the antenna mouth surface during remote sensing observation, so it is difficult to perform real-time calibration from the antenna mouth surface. End-to-end internal calibration method implementation

Method used

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  • Four-point calibration method based on waveguide switch
  • Four-point calibration method based on waveguide switch
  • Four-point calibration method based on waveguide switch

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0072] Embodiment 1: conventional radiometer calibration operation, such as figure 1 As shown, the waveguide switch is in the working state at this time, the feed source 1, the directional coupler port 2, the load 3, and the directional coupler port 4 are connected; the TTL level of K1 is low, and the noise source is in the low-level off state.

[0073] In principle, the ground-based microwave radiometer needs to be calibrated before any site is moved and started. The basic requirement for system calibration is to determine the corresponding relationship between the conversion from 0-level voltage data to 1-level brightness temperature data. In general, the radiometer receiver has been designed with a linearity requirement of 99.9%, so the calibration equation can be determined by external calibration at two points of cold and hot: T=K×V+b

[0074] Place the attached calibration source (cabinet) accessories together with the stand on the upper end of the radome of the machine ...

Embodiment 2

[0082] Embodiment 2: Internal calibration source calibration operation

[0083] Step 1. Calibration of the noise source surface, such as figure 1 As shown, the waveguide switch is in the working state at this time, and the feed source 1, the directional coupler port 2, the load 3, the directional coupler port 4, and the source TTL level are normally high and are in the open state.

[0084] Consistent with the calibration operation of the above-mentioned conventional radiometer, set the pitch stepper motor of the ground-based microwave radiometer back to the origin, make the antenna face point to the blackbody source inside the machine, read the stable output voltage value Vnh, and read the internal blackbody temperature TH.

[0085] Consistent with the calibration operation of the above-mentioned conventional radiometer, the ground-based microwave radiometer pitch stepper motor rotates 50,000 steps, the antenna face points directly above the random external soaked liquid nitr...

Embodiment 3

[0095] Embodiment 3: Real-time internal calibration operation during zenith atmospheric remote sensing

[0096] When the actual remote sensing works, the antenna face receives the atmospheric radiation signal in the direction of the zenith, the pitch stepper motor of the ground-based microwave radiometer rotates 50,000 steps, and the antenna face points to the zenith directly above, as shown in Figure 5 As shown, the remote sensing data is converted into level 0 voltage data V into level 1 brightness temperature data T according to the scaling equation: T=KxV+b.

[0097] In the remote sensing observation mode, the data change period (that is, the digital integration weighting time) is flexibly set through the interface software, and the corresponding host computer forms a pair of waveguide switches and noise sources and control timing, such as Figure 6 As shown, in this way, a calibration operation is performed before the next level 0 data is formed to form the coefficient f...

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Abstract

The invention provides a four-point calibration method based on a waveguide switch. The four-point calibration method comprises the following steps: step 1, acquiring receiver detection voltage VH andheat source external calibration TH; 2, placing the prepared external calibration source above a ground-based radiometer antenna housing, enabling an internal upper computer to execute a program to guide an antenna pitching motor to point to the position over the ground-based radiometer antenna housing, a main antenna aperture surface wave beam just irradiates a cold calibration source black body, and receiver detection voltage VL is obtained; 3, controlling the noise source to be turned on through a K2 switch, and respectively reading receiver voltage values Vnh and Vnl during external calibration of the cold source and the heat source, so as to determine the aperture equivalent brightness temperature of the external calibration TN of the noise source; step 4, controlling to cut off a signal of an antenna feeder port surface through a K1 switch, so as to eanble connect a broadband waveguide load; and controlling the noise source to be started through K2, and respectively reading thevoltage values Vr and Vnr of the receiver, thereby determining the aperture equivalent brightness temperature of the load source calibration TR.

Description

technical field [0001] The invention relates to the realization of the internal structure of a ground-based microwave radiometer, in particular to a four-point calibration method realized based on a waveguide switch. Background technique [0002] The ground-based microwave radiometer is a ground-based microwave remote sensing device that passively receives microwave signals of atmospheric radiation from various heights to judge changes in atmospheric temperature and humidity. and boundary layer turbulence play an important role in detection. Temperature, humidity and liquid water in tropospheric profiles from ground-based microwave radiometers, weather and climate model studies, satellite tracking (GPS, Galileo) wet / dry delay and humidity profiling, nowcasting atmospheric stability (severe weather detection), temperature Inversion detection, fog, air pollution, absolute calibration cloud radar, wet / dry delay correction VLBI has important applications, and has become an impo...

Claims

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Application Information

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IPC IPC(8): G01J5/00G01W1/18
CPCG01J5/00G01W1/18G01J5/80Y02A90/10
Inventor 苏兴华
Owner SHANGHAI SPACEFLIGHT INST OF TT&C & TELECOMM
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