A portable ground-based microwave radiometric calibration cold source

Abstract

The application relates to the field of microwave remote sensing technology, in particular to a portable ground-based microwave radiation calibration cold source, which comprises a top cover, a cylinder, a filling pipeline and a microwave window, wherein: the top cover is fastened above the cylinder and is connected with the cylinder through a sealing flange; the microwave window is fixed on the outer wall of one side of the cylinder and is used for radiating microwave brightness temperature; the filling pipeline is fixed on the top cover and is used for filling medium into the cylinder; and the inside space formed by the top cover and the cylinder is filled with vegetation after the top cover is fastened. The microwave scattering and absorption characteristics of the vegetation are mainly utilized, plant needles or plant branches are adopted as microwave absorption materials for the first time, and the standard temperature provided by liquid nitrogen or an ice-water mixture is combined, so that the standard radiation brightness temperature is provided for ground-based calibration under the premise of high enough microwave emissivity (greater than or equal to 0.99), and the portable ground-based microwave radiation calibration cold source has the advantages of light weight and portability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of microwave remote sensing, in particular to a portable ground-based microwave radiation calibration cold source. BACKGROUND

[0002] Microwave radiometers are widely used in atmospheric, ocean observation, agriculture and forestry detection, mineral resources exploration and military aerospace fields, and are key equipment for microwave remote sensing detection. In order to realize accurate quantitative application of microwave radiometers and ensure the detection accuracy of microwave radiometers, real-time calibration is needed to eliminate the drift of microwave radiometer output with temperature and time.

[0003] With the continuous development of science and technology, the calibration method of microwave radiometer is also developing, including liquid nitrogen calibration method, tilt curve calibration method, incremental reference calibration method, etc., but the essence is all "cold-hot" two-point calibration method, that is, using a calibration cold source and a calibration hot source with accurate known microwave radiation characteristics to simulate an ideal blackbody, and establishing a linear equation of radiometer output voltage and antenna temperature.

[0004] An ideal calibration (cold, hot) source has complete blackbody characteristics, and its microwave radiation brightness temperature is the same as the physical temperature. In order to simulate the blackbody characteristics as much as possible, the current ground-based calibration (cold, hot) source uses a periodic array of corner cube absorber structures based on the surface of a metal corner cube coated with an absorbing material. During ground calibration, the calibration source with a heating function on the back of the radiator is used as the "hot source", and the radiator is immersed in liquid nitrogen as the "cold source". However, due to the large difference in thermal expansion coefficient between metal materials and absorbing coating materials, long-term immersion in liquid nitrogen can easily cause the coating to crack and fall off. In addition, due to the fragility of the coating material, the corner cube is easily damaged and broken during ground use. Moreover, the metal material and the absorbing material have a high density (average density ≥ 4.0 g / cm 3 ), and the entire calibration source is heavy to carry and inconvenient to carry. SUMMARY

[0005] The present application provides a portable ground-based microwave radiation calibration cold source, which is simple in structure, convenient to carry, and ensures a high microwave emissivity to provide a standard radiation brightness temperature for ground calibration.

[0006] In order to achieve the above purpose, the present application provides a portable ground-based microwave radiation calibration cold source, which comprises a top cover, a cylinder, a filling pipe and a microwave window, wherein: the top cover is connected with the cylinder by a sealing flange; the microwave window is fixed on the outer wall of one side of the cylinder and is used for radiating microwave brightness temperature; the filling pipe is fixed on the top cover and is used for filling medium into the cylinder; and the inside space formed by the top cover and the cylinder is filled with vegetation after the top cover is buckled.

[0007] Further, the inner wall of the top cover is bonded with a top cover inner container, and the inner wall of the barrel is bonded with a barrel inner container.

[0008] Further, the sealing flange comprises an upper sealing flange and a lower sealing flange, the upper sealing flange is arranged on the top cover, the lower sealing flange is arranged on the barrel, the upper sealing flange and the lower sealing flange are connected through bolts and sealing rings, and a sealing surface is formed.

[0009] Further, a groove is arranged on the sealing surface of the top cover inner container, a boss is arranged on the sealing surface of the barrel inner container, and secondary sealing is formed between the top cover inner container and the barrel inner container through the cooperation of the groove and the boss.

[0010] Further, the microwave window comprises a gland, a wave-transparent sheet and a sealing strip, the gland is connected with the outer wall of the barrel, the wave-transparent sheet is tightly buckled on the outer wall of the barrel, and the sealing strip is arranged at the connection between the wave-transparent sheet and the outer wall of the barrel.

[0011] Further, a first handle is arranged at the top end of the top cover, a second handle is arranged at the other side of the barrel, and a base is arranged at the bottom of the barrel.

[0012] Further, the materials of the top cover and the barrel are stainless steel, and the materials of the top cover inner container and the barrel inner container are hard polyisocyanate foam plastic.

[0013] Further, the material of the gland is aluminum alloy material, and the material of the wave-transparent sheet is polyimide or phenolic plate material.

[0014] Further, the medium is liquid nitrogen or ice water mixture.

[0015] Further, the vegetation is plant needles or plant branches, and the internal space formed by the top cover and the barrel is filled with vegetation with a gap rate ≤ 20%.

[0016] The portable ground-based microwave radiation calibration cold source has the following beneficial effects:

[0017] The application mainly utilizes the microwave scattering and absorption characteristics of vegetation, and for the first time uses plant needles or plant branches as microwave absorption materials, and combines the standard temperature provided by liquid nitrogen or ice water mixture to ensure that the standard radiation brightness temperature is provided for ground-based calibration under the premise of high enough microwave emissivity (≥ 0.99), and has the advantages of light weight and portability. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings constituting a part of the present application are used to provide a further understanding of the present application, so that other features, objects and advantages of the present application become more apparent. The illustrative embodiment drawings of the present application and their descriptions are used to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0019] Figure 1 is a structural schematic diagram of a portable ground-based microwave radiation calibration cold source provided by an embodiment of the present application;

[0020] Figure 2 is a structural schematic diagram of a portable ground-based microwave radiation calibration cold source provided by an embodiment of the present application;

[0021] Figure 3 is an enlarged schematic diagram of sealing between a top cover and a cylinder of a portable ground-based microwave radiation calibration cold source provided by an embodiment of the present application;

[0022] Figure 4 is an enlarged schematic diagram of connection between a microwave window and a cylinder of a portable ground-based microwave radiation calibration cold source provided by an embodiment of the present application;

[0023] In the figure: 1-top cover, 11-top cover liner, 12-groove, 13-first handle, 2-cylinder, 21-cylinder liner, 22- boss, 23-second handle, 3-filling pipeline, 4-microwave window, 41- gland, 42-wave-transparent sheet, 43-sealing strip, 5-sealing flange, 51-upper sealing flange, 52-lower sealing flange, 53-bolt, 54-sealing ring, 6-medium, 7- vegetation, 8-base. DETAILED DESCRIPTION

[0024] In order to make the personnel in the technical field better understand the present application scheme, the technical scheme in the present application embodiment will be described clearly and completely in combination with the drawings in the present application embodiment. Obviously, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor should belong to the scope of protection of the present application.

[0025] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily indicate a specific order or a chronological sequence. It should be understood that the data thus used can be interchanged under appropriate circumstances, so that the embodiments of the present application described herein can be implemented. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0026] In the present application, the terms "upper", "lower", "left", "right", "front", "back", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "transverse", "longitudinal" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the present application and its embodiments, and are not intended to limit the indicated devices, elements or components to have a specific orientation, or to be constructed and operated in a specific orientation.

[0027] In addition, in addition to indicating the orientation or positional relationship, the above-mentioned partial terms can also be used to indicate other meanings, for example, the term "upper" can also be used to indicate a certain dependent relationship or connection relationship in some cases. For those skilled in the art, the specific meaning of these terms in the present application can be understood according to the specific situation.

[0028] In addition, the meaning of the term "a plurality of" should be two and more than two.

[0029] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0030] As shown in Figures 1-2 The present application provides a portable ground-based microwave radiation calibration cold source, which comprises a top cover 1, a cylinder body 2, a filling pipe 3 and a microwave window 4, wherein: the top cover 1 is fastened above the cylinder body 2 and connected with the cylinder body 2 through a sealing flange 5; the microwave window 4 is fixed on the outer wall of one side of the cylinder body 2 and used for radiating microwave brightness temperature; the filling pipe 3 is fixed on the top cover 1 and used for filling medium 6 into the cylinder body 2; and the internal space formed by the top cover 1 and the cylinder body 2 is filled with vegetation 7 after the top cover 1 is fastened.

[0031] Specifically, the portable ground-based microwave radiation calibration cold source provided by the embodiments of the present application uses plant needles or branches as microwave absorbing materials, combines with the standard temperature provided by liquid nitrogen or ice water mixture, and ensures that the standard radiation brightness temperature is provided for ground-based calibration under the premise of high enough microwave emissivity (≥0.99). Wherein, the shape of the whole calibration cold source is a cylindrical cylinder body 2 with a top cover 1, the top cover 1 is fastened above the cylinder body 2, and the top cover 1 is sealed and combined with the cylinder body 2 through a sealing flange 5, and forms a cavity space with the cylinder body 2 inside, the cavity space inside is filled with vegetation 7, during work, the medium 6 is filled into the cavity space through the filling pipe 3 above the top cover 1, and the standard radiation brightness temperature is provided to the outside through the microwave window 4 arranged on the side of the cylinder body 2.

[0032] Further, the inner wall of the top cover 1 is bonded with a top cover inner container 11, and the inner wall of the cylinder body 2 is bonded with a cylinder body inner container 21. The top cover inner container 11 is fixedly connected with the inner wall of the top cover 1 by an adhesive, and the cylinder body inner container 21 is fixedly connected with the inner wall of the cylinder body 2 by an adhesive. The top cover inner container 11 and the cylinder body inner container 21 are mainly used for the heat preservation storage of the internal liquid nitrogen.

[0033] Further, as shown in Figure 3 the sealing flange 5 includes an upper sealing flange 51 and a lower sealing flange 52, the upper sealing flange 51 is arranged on the top cover 1, the lower sealing flange 52 is arranged on the cylinder body 2, the upper sealing flange 51 and the lower sealing flange 52 are connected by a bolt 53 and a sealing ring 54, and a sealing surface is formed. The top cover 1 and the cylinder body 2 are sealed by the sealing flange 5, mainly to prevent the leakage of the internal liquid nitrogen, the upper sealing flange 51 and the lower sealing flange 52 are fixedly connected by the bolt 53, the upper sealing flange 51 and the lower sealing flange 52 are provided with the sealing ring 54, and the material of the sealing ring 54 is preferably a silicone rubber sealing ring 54 or a polytetrafluoroethylene sealing ring 54.

[0034] Further, the sealing surface of the top cover inner container 11 is provided with a groove 12, and the sealing surface of the cylinder body inner container 21 is provided with a boss 22, and the top cover inner container 11 and the cylinder body inner container 21 are connected by the groove 12 and the boss 22 to form a secondary seal. The sealing flange 5 is used for the external sealing of the top cover 1 and the cylinder body 2, and the internal sealing of the top cover 1 and the cylinder body 2 is realized by the cooperation of the groove 12 and the boss 22, so that the top cover inner container 11 and the cylinder body inner container 21 form a secondary seal, thereby ensuring the sealing effect.

[0035] Further, as shown in Figure 4 the microwave window 4 includes a gland 41, a wave-transparent sheet 42, and a sealing strip 43, the gland 41 is connected with the outer wall of the cylinder body 2, the wave-transparent sheet 42 is tightly pressed and buckled on the outer wall of the cylinder body 2, and the sealing strip 43 is arranged at the connection between the wave-transparent sheet 42 and the outer wall of the cylinder body 2. The microwave window 4 is mainly used to provide an outlet for microwave radiation, the wave-transparent sheet 42 is tightly pressed on one side of the outer wall of the cylinder body 2 by the gland 41, the sealing strip 43 is arranged at the connection between the wave-transparent sheet 42 and the cylinder body 2, and is mainly used for the sealing of the wave-transparent sheet 42, and the material of the sealing strip 43 is preferably a silicone rubber sealing ring 54 or a polytetrafluoroethylene sealing ring 54.

[0036] Further, the top end of the top cover 1 is provided with a first handle 13, the other side of the cylinder body 2 is provided with a second handle 23, and the bottom of the cylinder body 2 is provided with a base 8. The top cover 1 and the cylinder body 2 are both provided with handles, which are convenient for carrying. The bottom of the cylinder body 2 is provided with the base 8, which mainly plays a fixing role. According to the actual use, the cold source is fixed to the corresponding position by the base 8.

[0037] Further, the materials of the top cover 1 and the cylinder body 2 are stainless steel, and the materials of the top cover liner 11 and the cylinder body liner 21 are hard polyisocyanate foam plastic. The top cover 1 and the cylinder body 2 are made of stainless steel, mainly because the stainless steel material has appropriate strength and rigidity, corrosion resistance, and low cost. The hard polyisocyanate foam plastic is a special liquid nitrogen storage material, which is resistant to low temperature and also has wave transmission performance.

[0038] Further, the material of the gland 41 is aluminum alloy material, and the material of the wave transmission sheet 42 is polyimide or phenolic plate. The gland 41 is made of aluminum alloy material, which is light in weight and easy to process. The wave transmission sheet 42 generally uses polyimide or phenolic plate with wave transmission performance.

[0039] Further, the medium 6 is liquid nitrogen or ice water mixture. The medium 6 mainly provides a relatively stable low-temperature environment. The vegetation 7 is soaked in the low-temperature medium, and in a thermal equilibrium state, the radiation brightness temperature consistent with the physical temperature of the low-temperature medium can be obtained, which is used as a calibration cold source.

[0040] Further, the vegetation 7 is plant needles or plant branches, and the internal space formed by the top cover 1 and the cylinder body 2 is filled with a gap rate ≤ 20%. The vegetation 7 has the characteristics of microwave scattering and absorption. The vegetation 7 is placed in the internal space formed by the top cover 1 and the cylinder body 2 as a microwave absorbing material. The internal space formed by the top cover 1 and the cylinder body 2 is filled with a gap rate ≤ 20%, and the vegetation 7 needs a certain density, so that the vegetation 7 has good microwave absorption characteristics.

[0041] More specifically, when using the portable ground-based microwave radiation calibration cold source provided by the embodiment of the present application, the vegetation 7 is first filled into the top cover 1 and the cylinder body 2, and the top cover 1 is sealed and fixed on the top of the cylinder body 2 through the sealing flange 5 and the internal groove 12 and the boss 22. Secondly, the top cover 1 and the cylinder body 2 are placed on the workbench through the base 8. The medium 6 is filled into the cylinder body 2 through the filling pipe 3 on the top cover 1. After filling is completed, the filling pipe 3 is closed. The medium 6 and the vegetation 7 in the cylinder body 2 form a calibration cold source. Then, according to the ground use requirement, the calibration cold source is moved to the specified position through the handle, the direction of the microwave window 4 is adjusted, and the microwave window 4 radiates microwave brightness temperature along the specified direction. In the embodiment of the present application, the medium 6 provides a standard low-temperature environment, and the vegetation 7 is a microwave absorber. According to the Kirchhoff thermal radiation law, in a thermal equilibrium state, the energy absorbed by an object is equal to the energy emitted by the object. To make the physical temperature of the radiation source equal to its brightness temperature, it is required that the microwave emissivity is close to 1. Therefore, the vegetation 7 is soaked in the low-temperature medium 6, and in a thermal equilibrium state, the radiation brightness temperature consistent with the physical temperature of the low-temperature medium 6 can be provided, which is used as a calibration cold source.

[0042] The above descriptions are only the preferred embodiments of the present application, and are not intended to limit the present application. The present application can have various modifications and changes for those skilled in the art. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A portable ground-based microwave radiation calibration cold source, characterized in that, Includes top cover, cylinder, filling piping, and microwave window, among which: The top cover is fastened to the top of the cylinder and connected to the cylinder via a sealing flange; The microwave window is fixed on the outer wall of one side of the cylinder and is used to radiate microwave brightness temperature. The filling pipeline is fixed to the top cover and is used to fill the cylinder with a medium; After the top cover is fastened, the internal space formed by the top cover and the cylinder is filled with vegetation; The top of the top cover is provided with a first handle, the other side of the cylinder is provided with a second handle, and the bottom of the cylinder is provided with a base; The medium is liquid nitrogen or an ice-water mixture; The vegetation consists of plant needles or branches, and the gap filling ratio of the internal space formed by the top cover and the cylinder is ≤20%.

2. The portable ground-based microwave radiation calibration cold source according to claim 1, characterized in that, A liner is adhered to the inner wall of the top cover, and a liner is adhered to the inner wall of the cylinder.

3. The portable ground-based microwave radiation calibration cold source according to claim 2, characterized in that, The sealing flange includes an upper sealing flange and a lower sealing flange. The upper sealing flange is disposed on the top cover, and the lower sealing flange is disposed on the cylinder. The upper sealing flange and the lower sealing flange are connected by bolts and sealing rings to form a sealing surface.

4. The portable ground-based microwave radiation calibration cold source according to claim 3, characterized in that, The sealing surface of the top cover inner liner is provided with a groove, and the sealing surface of the inner cylinder liner is provided with a boss. The top cover inner liner and the inner cylinder liner form a secondary seal through the cooperation of the groove and the boss.

5. The portable ground-based microwave radiation calibration cold source according to claim 1, characterized in that, The microwave window includes a cover, a transmissive sheet, and a sealing strip. The cover is connected to the outer wall of the cylinder, pressing the transmissive sheet tightly against the outer wall of the cylinder. The sealing strip is located at the connection between the transmissive sheet and the outer wall of the cylinder.

6. The portable ground-based microwave radiation calibration cold source according to claim 2, characterized in that, Both the top cover and the cylinder are made of stainless steel, and both the inner liner of the top cover and the inner liner of the cylinder are made of rigid polyisocyanurate foam.

7. The portable ground-based microwave radiation calibration cold source according to claim 5, characterized in that, The cover is made of aluminum alloy, and the translucent sheet is made of polyimide or phenolic resin.

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