CN109357784B - K-waveband sky brightness temperature testing method - Google Patents
K-waveband sky brightness temperature testing method Download PDFInfo
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- CN109357784B CN109357784B CN201811388487.XA CN201811388487A CN109357784B CN 109357784 B CN109357784 B CN 109357784B CN 201811388487 A CN201811388487 A CN 201811388487A CN 109357784 B CN109357784 B CN 109357784B
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- G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
- G01K11/006—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using measurement of the effect of a material on microwaves or longer electromagnetic waves, e.g. measuring temperature via microwaves emitted by the object
Abstract
The invention relates to a K wave band sky brightness temperature test method, the device related by the method is composed of a K wave band receiver, a seat frame, a fixed frame, a rotating shaft, a bearing seat, an angle fixing nut, a first rotating shaft, a second rotating shaft, a first rotating table, a second rotating table, a normal temperature black body, a high temperature black body and a high temperature black body heat preservation cavity, the normal temperature black body and the high temperature black body are alternately introduced into the independent K wave band receiver feed source port surface by the method, the receiver strength and the temperature response ratio are measured and calculated, the normal temperature black body and the high temperature black body are removed, the receiver beam direction faces to the cold air with any elevation angle between 0 and 90 degrees, the current radiation strength is recorded, and the K wave band sky brightness temperature under the current elevation angle can be calculated by combining the receiver strength and the temperature response ratio measured and calculated before. The method is not limited to the clear night sky condition, can independently and quickly realize the K-band sky brightness temperature test under the elevation angle of 0-90 degrees, and provides real-time and accurate sky brightness temperature values for the intensity calibration in K-band observation.
Description
Technical Field
The invention relates to a K-waveband sky brightness temperature test method, in particular to a method for accurately and quickly testing K-waveband sky brightness temperature in receiver intensity calibration, which is specially used for testing K-waveband sky brightness temperature.
Background
Radio astronomy is an important research area in modern astronomy. The purpose of the radio astronomical intensity calibration is to convert the response of any one receiving device to an astronomical observation source into astronomical traffic. A common calibration method is to calculate the noise temperature of the receiver by using two different physical temperature broadband radiation sources (e.g., cold and hot black body loads) placed in front of the receiver first stage amplifier or mixer, respectively, and injecting their radiation into the feed or waveguide. After the noise temperature of the receiver is obtained, a stable second-stage calibration source (a pulse noise diode or a blackbody load) can be calibrated, then the second-stage calibration source is used for testing the system temperature of the receiver during observation, and then the radio source to be observed is observed in a pointing or deviating mode, so that the equivalent antenna temperature of the radio source can be obtained. And finally, converting the temperature of the radio source into an absolute bright temperature, a main beam bright temperature or a flux density according to the difference of the observed radio sources.
In a conventional cold and heat load method test performed in a laboratory or before observation, a black body load in a normal temperature state is generally used as a heat load, the black body load is placed in a foam vessel filled with liquid nitrogen so as to reduce the temperature of the black body to the temperature (77-80K) of the liquid nitrogen, then the cold and heat loads are respectively placed on the face of a feed source, the temperature and the strength output of the load are recorded, and the noise temperature and the noise source temperature of a receiver are calculated. In observation, the equivalent temperature of the radio source is calibrated twice by using the noise source calibrated previously.
The main reason why the cold and hot load method test cannot be performed in the observation process is that the cold load is inconvenient to use in the observation process, so the related test is generally to adjust the elevation angle of the antenna to 90 degrees before the observation, and is specially performed by a receiver engineer, and cannot be performed in the observation process. In addition, due to the fact that microwave devices of different wave band receivers are different in size, the long centimeter wave band feed source is too large in size, and if the diameter of the L wave band receiver feed source of the Nanshan station is 1.05 meters, the cold and heat load method is very difficult to use even before observation, and a sufficiently large cold load is difficult to provide and completely covers the feed source aperture.
In 1973, bell telephone laboratories were first proposed to use chopper wheel technology for millimeter wave calibration. The method is a calibration method for establishing a temperature scale by alternately introducing and removing a normal-temperature wave-absorbing material at the top of a feed source, so that a receiver alternately tests the radiation of the normal-temperature wave-absorbing material and the sky, and the difference between the temperature of the normal-temperature wave-absorbing material and the brightness temperature of the sky. This technique is simple and reliable and is adopted by most millimeter wave radio astronomy calibration systems for some time thereafter. The chopper wheel technique is also applicable to centimeter-band calibration, but most importantly requires knowledge of the bright sky temperature at the current elevation angle of observation for that band.
The research on sky bright temperature started in the last 50 th century, and it occupied a very important position in the microwave radiation characteristic research, such as in the radio astronomical antenna noise temperature test, the antenna system noise temperature includes receiver noise temperature, sky bright temperature, ground noise and antenna ohmic loss noise. Therefore, the method has very important significance for theoretical calculation and actual measurement of sky brightness temperature.
Disclosure of Invention
The invention aims to provide a K wave band sky brightness temperature testing method, which relates to a device consisting of a K wave band receiver, a seat frame, a fixed frame, a rotating shaft, a bearing seat, an angle fixing nut, a first rotating shaft, a second rotating shaft, a first rotating table, a second rotating table, a normal temperature black body, a high temperature black body and a high temperature black body heat preservation cavity, the testing device in the method can alternately introduce a normal temperature black body and a high temperature black body on the feed source face of the independent K-band receiver, so as to calculate the response ratio of the receiver strength and temperature, and then remove the normal temperature black body and the high temperature black body, the wave beam direction of the receiver faces to the cold air with any elevation angle between 0 and 90 degrees, the current radiation intensity is recorded, and the sky brightness temperature of the K wave band under the current elevation angle can be calculated by combining the previously measured response ratio of the receiver intensity and the temperature. The method is not limited to the clear night sky condition, the K-waveband sky brightness temperature test under the elevation angle of 0-90 ℃ can be independently and rapidly realized, the real-time and accurate sky brightness temperature value is provided for the intensity calibration in the K-waveband observation, and the calibration efficiency and precision are obviously improved.
The invention relates to a K wave band sky bright temperature test method, which comprises a K wave band receiver, a seat frame, a fixed frame, a rotating shaft, a bearing seat, an angle fixing nut, a first rotating shaft, a second rotating shaft, a first rotating table, a second rotating table, a normal temperature black body, a high temperature black body and a high temperature black body heat preservation cavity, wherein the lower part of a feed source flange of the K wave band receiver (1) is connected with the fixed frame (3), the rear end of the fixed frame (3) is respectively connected with the bottom ends of the first rotating shaft (7) and the second rotating shaft (8), the top end of the first rotating shaft (7) is connected with the first rotating table (9), the lower side of the first rotating table (9) is connected with the normal temperature black body (11), the top end of the second rotating shaft (8) is connected with the second rotating table (10), the lower side of the second rotating table (10) is connected with the high temperature black body (12), the high temperature black body, mount (3) side is connected with axis of rotation (4) one end, and axis of rotation (4) other end passes bearing frame (5) and is fastened by angle fixing nut (6), and bearing frame (5) are fixed in seat frame (2) side crossbeam top department, and concrete operation is gone on according to following step:
a. determining the elevation angle of sky bright temperature to be tested of the receiver, loosening an angle fixing nut (6), adjusting the beam direction of the fixing frame (3) and the K-waveband receiver (1) connected with the fixing frame to a target elevation angle, and tightening the angle fixing nut (6) to fix the elevation angle;
b. adjusting a first rotating shaft (7) to drive a first rotating table (9) and a normal-temperature black body (11) to rotate, enabling the normal-temperature black body (11) to completely cover the feed source face of the K-band receiver (1), and testing and recording the physical temperature of the normal-temperature black body (11) and the power value corresponding to the output end of the K-band receiver (1);
c. adjusting a first rotating shaft (7) to drive a first rotating table (9) and a normal-temperature black body (11) to rotate, so that the normal-temperature black body (11) is completely removed from a feed source port surface of a K-band receiver (1), adjusting a second rotating shaft (8) to drive a second rotating table (10) and a high-temperature black body (12) to rotate, so that the high-temperature black body (12) is completely covered on the feed source port surface of the K-band receiver (1), and testing and recording the physical temperature of the high-temperature black body (12) and the power value corresponding to the output end of the K-band receiver (1);
d. then adjusting a second rotating shaft (8) to drive a second rotating table (10) and a high-temperature black body (12) to rotate, so that the high-temperature black body (12) is completely moved away from a feed source face of the K-waveband receiver (1), the beam direction of the K-waveband receiver (1) faces cold air at the elevation angle, and the power value of the output end of the K-waveband receiver (1) facing the cold air at the elevation angle is tested and recorded;
e. and (c) directly calculating the sky brightness temperature of the K wave band under the current elevation angle by combining the physical temperature of the normal-temperature blackbody (11) tested in the step (b) and the power value corresponding to the output end of the K wave band receiver (1), the physical temperature of the high-temperature blackbody (12) and the power value corresponding to the output end of the K wave band receiver (1).
The invention relates to a K-waveband sky brightness temperature testing method, which comprises the following steps:
the K-band receiver (1) consists of a feed source, a transition section, a round-square conversion waveguide, an orthogonal mode coupler, an isolator, a waveguide coaxial converter and a low-noise amplifier, wherein all the components are cascaded in sequence; the lower part of a feed source flange of the K-waveband receiver (1) is fixedly connected with the fixed frame (3) by screws, so that the K-waveband receiver (1) and a wave beam direction thereof are kept in a unified posture when the K-waveband receiver and the wave beam direction thereof are changed;
the seat frame (2) is built by 12 angle irons, the angle irons are fixedly connected by angle pieces and screws, and the seat frame is mainly used for fixedly supporting the K-waveband receiver (1) in space and is also convenient for freely adjusting the wave beam direction of the receiver in the elevation angle range of 0-90 degrees;
the first rotating shaft (7) and the first rotating platform (9) are mainly used for introducing or removing a normal-temperature black body (11) required by testing on a feed source port surface of the K-band receiver (1), wherein the first rotating shaft (7) is a screw rod with a fixed length, the top end of the first rotating shaft is connected with the first rotating platform (9) formed by cutting a hard paperboard, the lower end of the first rotating platform (9) is connected with the normal-temperature black body (11) required by K-band calibration, and the normal-temperature black body (11) is a commercial flat-plate type wave-absorbing material;
the second rotating shaft (8) and the second rotating platform (10) are mainly used for introducing or removing a high-temperature black body (12) required by testing on a feed source port surface of the K-band receiver (1), wherein the second rotating shaft (8) is a screw rod with a fixed length, the top end of the second rotating platform is connected with the second rotating platform (10) formed by cutting a silica gel heating plate, the lower end of the second rotating platform (10) is connected with the high-temperature black body (12) required by K-band calibration, the periphery of the high-temperature black body (12) is wrapped by a high-temperature black body heat-preserving cavity (13) and is subjected to heat preservation, and the high-temperature black body (12;
the rotating shaft (4) is provided with a threaded screw at two ends, one end of the rotating shaft is connected with the side face of the fixing frame (3) and is used for supporting the K-waveband receiver (1) and the fixing frame (3), the other end of the rotating shaft (4) penetrates through the bearing seat (5) and is fastened by the angle fixing nut (6) and is used for fixing and adjusting the beam direction of the receiver, and the bearing seat (5) is a commercial product.
Compared with a method for calculating sky bright temperature by establishing a model theory, the method does not need to observe relevant data such as air pressure, humidity, altitude, water vapor content and the like of a station, only needs to test the intensity output and temperature values of a normal-temperature black body and a high-temperature black body, and calculates the response ratio g (formula 1) of the intensity and the temperature of the receiver:
wherein, the load temperature of the normal temperature black body is Tamb, the load temperature of the hot high temperature black body is Thot, the load strength of the normal temperature black body outputs Vamb, the load strength of the high temperature black body outputs Vhot, and the response ratio of the strength and the temperature of the receiver can be calculated according to the formula 1;
and then outputting Vsky by testing the strength of the receiver pointing to the cold space at the corresponding elevation angle according to the formula 2:
the sky brightness temperature Tsky under the current elevation angle of the K wave band can be calculated.
The invention has the advantages that the related device and the testing method are not limited to the clear night sky condition, the sky brightness temperature of the K wave band at an elevation angle of 0-90 ℃ can be independently tested under any weather condition, real-time and accurate sky brightness temperature values are provided for intensity calibration in K wave band observation, and the calibration efficiency and precision are obviously improved.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic diagram of a blackbody for testing a normal temperature when a beam direction of a receiver is 90 degrees according to the present invention;
FIG. 3 is a schematic diagram of the present invention for testing a high temperature blackbody when the beam direction of the receiver is 90 degrees;
FIG. 4 is a schematic diagram of a blackbody for testing a normal temperature when a beam direction of a receiver is 45 degrees according to the present invention;
FIG. 5 is a schematic diagram of the present invention for testing a high temperature blackbody when the beam direction of the receiver is 45 degrees;
FIG. 6 is a diagram illustrating the testing of cold air at a receiver beam direction of 45 degrees according to the present invention;
FIG. 7 is a schematic view of a high temperature black body and related structures according to the present invention.
Detailed Description
Examples
The invention relates to a K wave band sky bright temperature test method, which comprises a K wave band receiver, a seat frame, a fixed frame, a rotating shaft, a bearing seat, an angle fixing nut, a first rotating shaft, a second rotating shaft, a first rotating table, a second rotating table, a normal temperature black body, a high temperature black body and a high temperature black body heat preservation cavity, wherein the lower part of a feed source flange of the K wave band receiver 1 is connected with the fixed frame 3, the rear end of the fixed frame 3 is respectively connected with the bottom ends of the first rotating shaft 7 and the second rotating shaft 8, the top end of the first rotating shaft 7 is connected with the first rotating table 9, the lower side of the first rotating table 9 is connected with the normal temperature black body 11, the top end of the second rotating shaft 8 is connected with the second rotating table 10, the lower side of the second rotating table 10 is connected with the high temperature black body 12, the high temperature black body, the other end of the rotating shaft 4 penetrates through a bearing seat 5 and is fastened by an angle fixing nut 6, the bearing seat 5 is fixed at the top end of a lateral beam of the seat frame 2, and the concrete operation is carried out according to the following steps:
a. determining the elevation angle of the sky brightness temperature to be tested of the receiver (assuming that the elevation angle to be tested is the K wave band sky brightness temperature of 90 degrees), loosening the angle fixing screw cap 6, adjusting the beam direction of the fixing frame 3 and the K wave band receiver 1 connected with the fixing frame to the target elevation angle, and tightening the angle fixing screw cap 6 to fix the elevation angle;
b. adjusting the first rotating shaft 7 to drive the first rotating table 9 and the normal-temperature black body 11 to rotate, so that the normal-temperature black body 11 completely covers a feed source port surface (shown in fig. 2) of the K-band receiver 1, and testing and recording the physical temperature of the normal-temperature black body 11 and the power value corresponding to the output end of the K-band receiver 1;
c. adjusting a first rotating shaft 7 to drive a first rotating table 9 and a normal-temperature black body 11 to rotate, so that the normal-temperature black body 11 is completely removed from a feed source port surface of a K-band receiver 1, adjusting a second rotating shaft 8 to drive a second rotating table 10 and a high-temperature black body 12 at the lower part of the second rotating table to rotate, so that the high-temperature black body 12 is completely covered on the feed source port surface of the K-band receiver 1 (as shown in figure 3), and testing and recording the physical temperature of the high-temperature black body 12 and the power value corresponding to the output end of;
d. then adjusting the second rotating shaft 8 to drive the second rotating table 10 and the high-temperature black body 12 to rotate, so that the high-temperature black body 12 is completely moved away from the feed source aperture surface of the K-band receiver 1, the beam direction of the K-band receiver 1 is opposite to the cold space at the elevation angle (as shown in figure 1), and the power value of the output end of the K-band receiver 1 opposite to the cold space at the elevation angle is tested and recorded;
e. and (c) directly calculating the sky brightness temperature of the K wave band under the current elevation angle by combining the physical temperature of the normal-temperature black body 11 and the power value corresponding to the output end of the K wave band receiver 1 tested in the steps b and c, and the physical temperature of the high-temperature black body 12 and the power value corresponding to the output end of the K wave band receiver 1.
In practical applications, it may be necessary to test the sky brightness temperature at any elevation angle K band between 0 and 90 degrees, and if the sky brightness temperature at the elevation angle K band of 45 degrees needs to be tested, only the step a (shown in fig. 4), the step b (shown in fig. 5), and the step c (shown in fig. 6) need to be sequentially executed.
Claims (1)
1. A K wave band sky bright temperature test method is characterized in that a device related to the method is composed of a K wave band receiver, a seat frame, a fixing frame, a rotating shaft, a bearing seat, an angle fixing nut, a first rotating shaft, a second rotating shaft, a first rotating table, a second rotating table, a normal temperature black body, a high temperature black body and a high temperature black body heat preservation cavity, the lower portion of a feed source flange of the K wave band receiver (1) is connected with the fixing frame (3), the rear end of the fixing frame (3) is respectively connected with the bottom ends of the first rotating shaft (7) and the second rotating shaft (8), the top end of the first rotating shaft (7) is connected with the first rotating table (9), the lower side of the first rotating table (9) is connected with the normal temperature black body (11), the top end of the second rotating shaft (8) is connected with the second rotating table (10), the lower side of the second rotating table (10) is connected with the high temperature black body (12, mount (3) side is connected with axis of rotation (4) one end, and axis of rotation (4) other end passes bearing frame (5) and is fastened by angle fixing nut (6), and bearing frame (5) are fixed in seat frame (2) side crossbeam top department, and concrete operation is gone on according to following step:
a. determining the elevation angle of the sky bright temperature to be tested of the K-band receiver, loosening an angle fixing nut (6), adjusting the beam direction of a fixing frame (3) and the K-band receiver (1) connected with the fixing frame to a target elevation angle, and tightening the angle fixing nut (6) to fix the elevation angle;
b. adjusting a first rotating shaft (7) to drive a first rotating platform (9) and a normal-temperature black body (11) at the lower part of the first rotating platform to rotate, enabling the normal-temperature black body (11) to completely cover the feed source port surface of the K-band receiver (1), and testing and recording the physical temperature of the normal-temperature black body (11) and the power value corresponding to the output end of the K-band receiver (1);
c. adjusting a first rotating shaft (7) to drive a first rotating table (9) and a normal-temperature black body (11) to rotate, so that the normal-temperature black body (11) is completely removed from a feed source port surface of a K-band receiver (1), adjusting a second rotating shaft (8) to drive a second rotating table (10) and a high-temperature black body (12) to rotate, so that the high-temperature black body (12) is completely covered on the feed source port surface of the K-band receiver (1), and testing and recording the physical temperature of the high-temperature black body (12) and the power value corresponding to the output end of the K-band receiver (1);
d. then adjusting a second rotating shaft (8) to drive a second rotating table (10) and a high-temperature black body (12) to rotate, so that the high-temperature black body (12) is completely moved away from a feed source port face of the K-waveband receiver (1), the beam direction of the K-waveband receiver (1) faces to cold air at the target elevation angle, and the power value of the output end of the K-waveband receiver (1) facing to the cold air at the target elevation angle is tested and recorded;
e. and (c) directly calculating the sky brightness temperature of the K wave band under the current elevation angle by combining the physical temperature of the normal-temperature blackbody (11) tested in the step (b) and the power value corresponding to the output end of the K wave band receiver (1), the physical temperature of the high-temperature blackbody (12) and the power value corresponding to the output end of the K wave band receiver (1).
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| CN113175997B (en) * | 2021-04-30 | 2023-11-24 | 中国科学院新疆天文台 | Method for testing sky brightness temperature by horn antenna |
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| CN206161853U (en) * | 2016-11-09 | 2017-05-10 | 武汉华梦科技有限公司 | Meteorological microwave radiometer system of ground based on dual -frenquency antenna |
| CN107404357A (en) * | 2017-09-22 | 2017-11-28 | 中国科学院新疆天文台 | A kind of Q-band receiver intensity calibration method |
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