阅读说明：本技术 一种气体介电常数测试装置 (Gas dielectric constant testing device ) 是由 高冲 李恩 宋鑫 张云鹏 高勇 李亚峰 郑虎 于 2020-07-29 设计创作，主要内容包括：一种气体介电常数测试装置,通过将密封腔侧壁的上表面与密封腔盖板的下表面固定连接形成一个中空的密封腔体；在密封腔体内依次设置非金属固定隔离块和平面谐振结构在密封腔底板上,通过将平面谐振结构的介质基板上表面与密封腔盖板下表面的外侧金属台阶和内侧金属台阶固定连接,在密封腔盖板和平面谐振结构之间且位于外侧金属台阶和内侧金属台阶之间的区域构成气体测试区域；气体测试区域内平面谐振结构的介质基板和平面金属单元以及密封腔盖板下表面的金属面构成倒置微带线谐振电路,对倒置微带线谐振电路中的平面金属单元进行谐振激励和接收,根据不同气体的介电常数不同导致倒置微带等效介电常数变化的原理对气体介电常数进行测试。(A gas dielectric constant testing device forms a hollow sealed cavity by fixedly connecting the upper surface of the side wall of a sealed cavity and the lower surface of a cover plate of the sealed cavity; the method comprises the following steps that a nonmetal fixed isolation block and a planar resonance structure are sequentially arranged in a sealed cavity on a sealed cavity bottom plate, the upper surface of a medium substrate of the planar resonance structure is fixedly connected with an outer side metal step and an inner side metal step of the lower surface of a sealed cavity cover plate, and a gas test area is formed in an area between the sealed cavity cover plate and the planar resonance structure and between the outer side metal step and the inner side metal step; the dielectric substrate and the planar metal unit of the planar resonance structure in the gas test area and the metal surface on the lower surface of the sealing cavity cover plate form an inverted microstrip line resonance circuit, the planar metal unit in the inverted microstrip line resonance circuit is subjected to resonance excitation and receiving, and the gas dielectric constant is tested according to the principle that the equivalent dielectric constant of the inverted microstrip changes due to the difference of the dielectric constants of different gases.)

1. The gas dielectric constant testing device is characterized by comprising a sealing cavity and a sealing cavity cover plate, wherein the sealing cavity comprises a bottom plate and a side wall, and a hollow sealing cavity body is formed by fixedly connecting the upper surface of the side wall of the sealing cavity with the lower surface of the sealing cavity cover plate; a nonmetal fixed isolation block and a plane resonance structure are arranged in the sealed cavity, and the nonmetal fixed isolation block and the plane resonance structure are sequentially arranged on a bottom plate of the sealed cavity;

the lower surface of the sealing cavity cover plate is a metal surface, at least one plane metal unit is printed on the upper surface of the medium substrate of the plane resonance structure, and the lower surface of the medium substrate of the plane resonance structure is not coated with copper; the lower surface of the sealing cavity cover plate is provided with an outer side metal step and an inner side metal step, the upper surface of the dielectric substrate of the planar resonance structure is fixedly connected with the outer side metal step and the inner side metal step of the lower surface of the sealing cavity cover plate, and a region between the sealing cavity cover plate and the planar resonance structure and between the outer side metal step and the inner side metal step is used as a gas testing region; the sealing cavity cover plate is provided with an air inlet hole and an air outlet hole, and gas to be tested enters from the air inlet hole, fills the gas testing area and then is discharged from the air outlet hole;

the planar metal unit is positioned in the gas testing area and is not contacted with the sealing cavity cover plate, and the dielectric substrate, the planar metal unit and the metal surface of the lower surface of the sealing cavity cover plate in the gas testing area form an inverted microstrip line resonant circuit; the gas dielectric constant testing device is also provided with a micro-strip resonance excitation and receiving part which is used for carrying out resonance excitation and receiving on all the plane metal units in the inverted micro-strip line resonance circuit.

2. The gas dielectric constant testing device of claim 1, wherein a plurality of horizontal gas through holes are formed in the outer metal step, and the gas to be tested in the gas testing area is filled in the whole sealed cavity after passing through the horizontal gas through holes.

3. The gas dielectric constant testing device of claim 1 or 2, wherein the planar metal unit is of an annular structure, and the planar metal unit of the annular structure and the metal surface of the lower surface of the sealing cavity cover plate form an inverted microstrip resonator.

4. The gas dielectric constant testing device according to claim 3, wherein a plurality of sealing cavity coupling holes are formed in the sealing cavity bottom plate, a plurality of fixed block coupling holes concentric with all the sealing cavity coupling holes are formed in the non-metal fixed isolation block, a plurality of coaxial magnetic coupling rings are respectively inserted into the corresponding sealing cavity coupling holes and the corresponding fixed block coupling holes to serve as the microstrip resonance excitation and reception portions, and two coaxial magnetic coupling rings are inserted into the corresponding two sealing cavity coupling holes and two fixed block coupling holes of each annular structure to perform resonance excitation and reception.

5. The gas dielectric constant testing device of claim 4, wherein an electromagnetic shielding groove is arranged between the two fixed block coupling holes of the non-metal fixed isolation block corresponding to one planar metal unit, and the electromagnetic shielding groove is filled with a wave-absorbing material.

Technical Field

The invention belongs to the technical field of microwave and millimeter wave material electromagnetic parameter testing, and relates to a gas dielectric constant testing device.

Background

The research on the characteristics and components of the gas is needed in the fields of remote sensing, atmospheric pollution detection, industrial gas component analysis and the like. The gas component analysis methods mainly include electrochemical methods, infrared optical methods, gas chromatography/mass spectrometry methods, microwave methods and the like, and each method has respective advantages and disadvantages, wherein the microwave method has become an important detection means with the advantages of higher detection sensitivity, low cost, high speed, no harm and the like. The microwave method has the testing principle that the dielectric constants of different gases are different, and the microwave parameters of the sensors are changed when the microwave method is loaded in the microwave testing sensors, so that the dielectric constants and component proportions of the gases can be inverted, and the microwave method is used for testing and analyzing the gases and is still used for essentially accurately testing the dielectric constants of the gases.

At present, the gas dielectric test method mainly includes a capacitance method, a resonant cavity method, a plane transmission line method and the like, wherein the capacitance method is to fill gas to be tested between two electrodes, test the change of capacitance value and reversely calculate the dielectric constant of the gas according to a capacitance calculation formula (Chenwanjin. measuring the dielectric constant of the gas by using a resonant circuit [ J ] metering technology, 1999(08):22-23. Zhang Hao Jing and the like. measuring the relative dielectric constant of the gas [ J ] of university of Yunnan university: Nature edition, 2005(01): 17-19.). This method is typically used for dielectric testing at dc or low frequencies.

The resonant cavity method is generally to fill all gas in the resonant cavity, and calculate the dielectric constant of the gas by testing the variation of the resonant frequency and quality factor (Zhang Yu. high Q microwave resonant cavity design for measuring the refractive index of the gas [ J ]. Mimo, 2008(03): 78-81.). The method has high test sensitivity, and in the on-line test process, the change of the gas temperature and the pressure can cause the tiny change of the size of the resonant cavity, thereby causing test errors, so the method still needs to be further researched and improved in the aspect of improving the stability of the cavity.

In the planar transmission line method, a microstrip structure is mainly designed, a resonant structure such as a ring shape and a defected ground is usually designed, the disturbance of a radiation field by gas is tested, the gas component is detected and analyzed according to the change of the resonant frequency, and the dielectric constant of the gas is tested. The method has low design and processing cost, small sensor size and easy miniaturization and integration, but the detection sensitivity may be limited because the energy distribution of the radiation field is not strong.

Based on the above analysis, the sensor is required to have high sensitivity, low design cost and good stability for the on-line test requirement of the gas dielectric constant, and in the existing microwave sensor structure, the requirements can be rarely met at the same time, so that further research and improvement are needed on the basis of the research of the existing sensor so as to meet the on-line test requirement of the gas dielectric constant.

Disclosure of Invention

The invention provides a gas dielectric constant testing device for realizing on-line testing of gas dielectric constant, aiming at solving the problem that the existing gas dielectric constant testing structure is difficult to simultaneously meet the requirements of high detection sensitivity, high stability and low cost.

In order to achieve the above purpose, the invention adopts the following technical scheme:

a gas dielectric constant testing device comprises a sealing cavity and a sealing cavity cover plate, wherein the sealing cavity comprises a bottom plate and a side wall, and a hollow sealing cavity body is formed by fixedly connecting the upper surface of the side wall of the sealing cavity with the lower surface of the sealing cavity cover plate; a nonmetal fixed isolation block and a plane resonance structure are arranged in the sealed cavity, and the nonmetal fixed isolation block and the plane resonance structure are sequentially arranged on a bottom plate of the sealed cavity;

the lower surface of the sealing cavity cover plate is a metal surface, at least one plane metal unit is printed on the upper surface of the medium substrate of the plane resonance structure, and the lower surface of the medium substrate of the plane resonance structure is not coated with copper; the lower surface of the sealing cavity cover plate is provided with an outer side metal step and an inner side metal step, the upper surface of the dielectric substrate of the planar resonance structure is fixedly connected with the outer side metal step and the inner side metal step of the lower surface of the sealing cavity cover plate, and a region between the sealing cavity cover plate and the planar resonance structure and between the outer side metal step and the inner side metal step is used as a gas testing region; the sealing cavity cover plate is provided with an air inlet hole and an air outlet hole, and gas to be tested enters from the air inlet hole, fills the gas testing area and then is discharged from the air outlet hole;

the planar metal unit is positioned in the gas testing area and is not contacted with the sealing cavity cover plate, and the dielectric substrate, the planar metal unit and the metal surface of the lower surface of the sealing cavity cover plate in the gas testing area form an inverted microstrip line resonant circuit; the gas dielectric constant testing device is also provided with a micro-strip resonance excitation and receiving part which is used for carrying out resonance excitation and receiving on all the plane metal units in the inverted micro-strip line resonance circuit.

Specifically, a plurality of horizontal gas through holes are formed in the metal step on the outer side, and gas to be tested in the gas testing area passes through the horizontal gas through holes and then is filled in the whole sealing cavity.

Specifically, the planar metal unit is of an annular structure, and the planar metal unit of the annular structure and the metal surface of the lower surface of the sealing cavity cover plate form an inverted microstrip resonator.

Specifically, a plurality of sealed cavity coupling holes are formed in the sealed cavity bottom plate, a plurality of fixed block coupling holes which are concentric with all the sealed cavity coupling holes are formed in the nonmetal fixed isolation block, a plurality of coaxial magnetic coupling rings are inserted into the corresponding sealed cavity coupling holes and the corresponding fixed block coupling holes respectively to serve as microstrip resonance excitation and receiving parts, and two coaxial magnetic coupling rings are inserted into the corresponding sealed cavity coupling holes and the corresponding two fixed block coupling holes to perform resonance excitation and receiving on the planar metal unit of each annular structure.

Specifically, an electromagnetic shielding groove is formed between two fixed block coupling holes corresponding to one planar metal unit on the nonmetal fixed isolation block, and a wave-absorbing material is filled in the electromagnetic shielding groove.

The invention has the beneficial effects that: compared with the traditional microstrip line radiation field test method, the inverted microstrip resonance structure has the advantages that the field energy of a gas test area is stronger, higher test sensitivity can be realized, and the test precision is further improved by adding the electromagnetic shielding groove in the embodiment; in addition, in some embodiments of the invention, horizontal gas through holes are designed around the outer metal step, so that the gas to be tested is filled in the whole sealed cavity, the influence of the pressure change on the resonant structure is transferred to the wall of the sealed cavity, and the influence of the size change of the inverted microstrip resonant structure on the resonant frequency is small, therefore, the invention can realize higher test stability; the plane resonance structure can adopt a metal resonance ring or other forms of resonance structures, can realize multiple resonance units on the dielectric substrate, effectively expands the test frequency range, realizes the miniaturization of the test device, is more beneficial to integration and has lower design cost.

Drawings

Fig. 1 is a separated structural diagram of a gas dielectric constant testing device according to the present invention, wherein 1 is a sealing cavity cover plate, 2 is a planar resonant structure, 3 is a non-metallic fixed spacer, and 4 is a sealing cavity.

Fig. 2 is a schematic diagram of a cover plate 1 of a sealed cavity in a gas dielectric constant testing device, wherein 1-1 is an air inlet, 1-2 is an air outlet, 1-3 is an outer metal step, 1-4 is an inner metal step, 1-5 is a horizontal gas through hole, and 1-6 is a metal surface.

Fig. 3 is a schematic diagram of a planar resonant structure 2 in a gas dielectric constant testing device according to the present invention, wherein 2-1 is a dielectric substrate, 2-2 is an inner planar metal unit, and 2-3 is an outer planar metal unit.

FIG. 4 is a schematic view of a non-metallic fixed spacer 3 in a gas dielectric constant testing apparatus according to the present invention, wherein 3-1 is an outer coupling hole of the non-metallic fixed spacer 3 for resonance excitation; 3-2 is another outside coupling hole of the non-metal fixed isolation block 3 for resonance receiving; 3-3 is an inner side coupling hole of the non-metal fixed isolation block 3 for resonance excitation; 3-4 is another inner side coupling hole of the non-metal fixed isolation block 3 for resonance receiving; 3-5 is an electromagnetic shielding slot between two inner side coupling holes 3-3 and 3-4 of the non-metallic fixed separation block 3, and 3-6 is an electromagnetic shielding slot between two outer side coupling holes 3-1 and 3-2 of the non-metallic fixed separation block 3.

FIG. 5 is a schematic diagram of a sealed cavity 4 in a gas dielectric constant testing device according to the present invention, wherein 4-1 is an outer coupling hole of the sealed cavity 4, which is concentric with the outer coupling hole 3-1 of the nonmetal fixed isolation block 3, 4-2 is another outer coupling hole of the sealed cavity 4, which is concentric with the outer coupling hole 3-2 of the nonmetal fixed isolation block 3, 4-3 is an inner coupling hole of the sealed cavity 4, which is concentric with the inner coupling hole 3-3 of the nonmetal fixed isolation block 3, 4-4 is another inner coupling hole of the sealed cavity 4, which is concentric with the inner coupling hole 3-4 of the nonmetal fixed isolation block 3.

FIG. 6 is a schematic diagram of the resonance curves of a gas dielectric constant testing device for testing two different gases (nitrogen N2 and carbon dioxide CO2) according to the present invention.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.

As shown in figure 1, the gas dielectric constant testing device provided by the invention comprises a sealing cavity cover plate 1, a planar resonant structure 2, a non-metal fixed isolation block 3 and a sealing cavity 4, wherein the sealing cavity 4 comprises a bottom plate and a side wall, a hollow sealing cavity is formed by fixedly connecting the upper surface of the side wall of the sealing cavity 4 with the lower surface of the sealing cavity cover plate 1, the non-metal fixed isolation block 3 and the planar resonant structure 2 are arranged in the hollow sealing cavity, the non-metal fixed isolation block 3 and the planar resonant structure 2 are sequentially arranged on the bottom plate of the sealing cavity 1 from bottom to top, the lower surface of the sealing cavity cover plate 1 is provided with outer metal steps 1-3 and inner metal steps 1-4, the planar resonant structure 2 can be connected with the outer metal steps 1-3 and the inner metal steps 1-4 of the sealing cavity cover plate 1 by using the non-metal fixed isolation block 3, thereby fixed plane resonance structure 2 and sealed chamber apron 1 for plane resonance structure 2 back-off is at sealed chamber apron 1 inboard, and guarantees that the one side that has microstrip resonant circuit (being medium base plate upper surface) is close to sealed chamber apron 1 and contactless. The sealing cavity cover plate 1, the plane resonance structure 2, the nonmetal fixing and isolating block 3 and the sealing cavity 4 are concentric and can be fixed through threaded holes in metal steps 1-3 on the outer side in fig. 2, threaded holes in the outermost side of the plane resonance structure 2 in fig. 3 and threaded holes in the outermost side of the nonmetal fixing and isolating block 3 in fig. 4.

The area between the sealing cavity cover plate 1 and the plane resonance structure 2 and between the outer side metal steps 1-3 and the inner side metal steps 1-4 is used as a gas testing area; the sealed cavity cover plate 1 is provided with an air inlet 1-1 and an air outlet 1-2, and gas to be tested enters from the air inlet 1-1 and is discharged from the air outlet 1-2 after filling a gas testing area. In some embodiments, in order to ensure that the planar resonant structure 2 does not deform due to air pressure change during inflation and air exhaust, a plurality of horizontal air through holes 1-5 are designed around the outer metal step 1-3, and as shown in fig. 2, in this embodiment, 8 horizontal air through holes 1-5 (arranged in an equiangular circumference) are designed around the outer metal step 1-3, so that the gas to be tested can penetrate through the outer metal step 1-3 from the gas testing area and be filled in the whole sealed cavity, and therefore, the influence of the air pressure change on the resonant structure is transferred to the wall of the sealed cavity, and the stability of the gas testing area is ensured.

The lower surface of the sealing cavity cover plate 1 is a metal surface 1-6, at least one plane metal unit is printed on the upper surface of a medium substrate 2-1 of the plane resonance structure 2, as shown in fig. 2, two plane metal units 2-2 and 2-3 with annular structures are arranged in the embodiment, 2-2 is an inner plane metal unit, and 2-3 is an outer plane metal unit; the lower surface of the dielectric substrate of the planar resonant structure 2 is not coated with copper. Besides the annular structure, the planar metal unit can be arranged into other resonant structures; one or more planar metal units can be arranged on the same dielectric substrate, for example, in order to implement a test in a wider frequency range and lower design cost in this embodiment, two planar metal units 2-2 and 2-3 with annular structures of different sizes (corresponding to different frequency ranges) are designed on the same dielectric substrate 2-1, and no influence is guaranteed between the planar metal units and the planar metal units, and in order to implement a test in a higher frequency range, more resonant rings can be designed in the center.

The planar metal units 2-2 and 2-3 in this embodiment are two concentric ring structures, with an outer ring having a radius of 42.5mm, an inner ring having a radius of 28.5mm and a width of 2.5 mm. The dielectric substrate adopts Rogers 4350 and has a thickness of 0.762mm, the thickness can affect the energy coupling of the resonant ring, and if the coupling amount is too weak or too strong, the coupling amount can be adjusted by respectively reducing or increasing the thickness of the substrate. The heights of the outer side metal steps 1-3 and the inner side metal steps 1-4 in the sealing cavity cover plate 1 are set to be 1 mm. In addition, the inner diameter of the outer side metal step 1-3 is ensured to be large enough, so that the field distribution of the outer side resonant ring is not influenced; the outer diameter of the inner metal steps 1-4 is small enough not to affect the field distribution of the inner resonance ring, and the inner diameter of the outer metal steps 1-3 and the outer diameter of the inner metal steps 1-4 can be empirically evaluated through simulation results.

Because the sealing cavity cover plate 1 has the outer metal steps 1-3 and the inner metal steps 1-4, when the microstrip line resonance circuit of the planar resonance structure 2 is reversely buckled on the cover plate 1, the dielectric substrate 2-1, the planar metal units 2-2 and 2-3 and the metal surfaces 1-6 on the lower surface of the sealing cavity cover plate 1 in the gas testing area form the inverted microstrip line resonance circuit, and the energy of the field is mainly concentrated in the gas testing area.

The gas dielectric constant testing device is also provided with a microstrip resonance excitation and receiving part which is used for carrying out resonance excitation and receiving on the planar metal unit in the inverted microstrip resonance circuit. In some embodiments, a coaxial magnetic coupling ring may be used for excitation and reception of microstrip resonance, as shown in fig. 4 and 5, for two planar metal units 2-2 and 2-3 of annular structures provided in this embodiment, two outer coupling holes 3-1 and 3-2 of a non-metallic fixed spacer are provided on a non-metallic fixed spacer 3, two outer coupling holes 4-1 and 4-2 of a sealed cavity concentric with 3-1 and 3-2 are correspondingly provided on a bottom plate of the sealed cavity 4, the coaxial magnetic coupling ring is inserted into 3-1 and 4-1 to excite the outer planar metal unit 2-3 in resonance, and the coaxial magnetic coupling ring is inserted into 3-2 and 4-2 to receive the outer planar metal unit 2-3 in resonance. Similarly, the invention is provided with two inner side coupling holes 3-3 and 3-4 of the nonmetal fixed isolation block on the nonmetal fixed isolation block 3, correspondingly provided with two inner side coupling holes 4-3 and 4-4 of the sealed cavity concentric with the nonmetal fixed isolation block 3-3 and 3-4 on the bottom plate of the sealed cavity 4, inserting the coaxial magnetic coupling rings 3-3 and 4-3 to carry out resonance excitation on the inner side plane metal unit 2-2, and inserting the coaxial magnetic coupling rings 3-4 and 4-4 to carry out resonance receiving on the inner side plane metal unit 2-2.

In order to achieve higher test accuracy, in some embodiments, an electromagnetic shielding groove may be further designed on the non-metal fixed block 3, and a wave-absorbing material is filled in the electromagnetic shielding groove to absorb the electromagnetic wave signals of crosstalk. As shown in FIG. 4, an electromagnetic shielding slot 3-5 is designed between the outer side coupling holes 3-1 and 3-2 of the two non-metal fixed isolation blocks, an electromagnetic shielding slot 3-6 is designed between the inner side coupling holes 3-3 and 3-4 of the two non-metal fixed isolation blocks, a wave-absorbing material is filled or coated in the electromagnetic shielding slot 3-5 to shield crosstalk signals between the outer side coupling holes 3-1 and 3-2 of the two non-metal fixed isolation blocks, and a wave-absorbing material is filled or coated in the electromagnetic shielding slot 3-6 to shield crosstalk signals between the inner side coupling holes 3-3 and 3-4 of the two non-metal fixed isolation blocks.

The metal on the surfaces of the planar metal units 2-2 and 2-3 and the lower surface of the capsule cover plate 1 is typically plated with gold or silver, but silver is easily oxidized and has a lower conductivity than gold, so in some embodiments it is preferable to plate the metal on the surfaces of the planar metal units and the lower surface of the capsule cover plate 1 with gold to improve the quality factor and test sensitivity.

The technical principle of the invention is as follows:

the metal surface 1-6, the dielectric substrate 2-1 and the planar metal units 2-2 and 2-3 on the lower surface of the sealing cavity cover plate 1 form an inverted microstrip line with a gas layer in the middle, and main field energy is concentrated in the gas layer in the middle, namely a gas testing area. When different gases are filled, the equivalent dielectric constant of the inverted microstrip changes due to the difference of the dielectric constants.

The frequency calculation formula of the microstrip line resonant ring is as follows:

where n is the resonant mode, f_nIs the resonant frequency of the nth mode, c is the speed of light, r is the resonant ring radius,_effIs the equivalent dielectric constant of the microstrip line.

From the above equation, it can be seen that the change in the equivalent dielectric constant causes the resonance frequency to change. The resonance frequency of two different gases, nitrogen and carbon dioxide during filling, was verified by simulation using HFSS three-dimensional electromagnetic field simulation software, as shown in fig. 6. From the simulation results, it can be seen that there is a clear difference in resonant frequency between the two gas fills, and the deviation of the resonant frequency is larger as the frequency increases. Any other gas may be filled in addition to the nitrogen gas and the carbon dioxide gas, or when a mixed gas is filled, the gas composition ratio may be measured.

In practical test, gas to be tested is completely filled in a gas test area of the inverted microstrip resonance structure from the gas inlet hole 1-1, two test ports of the vector network analyzer are respectively connected with the coaxial magnetic coupling rings in the coupling holes, and an S21 curve is tested, so that the resonant frequency f corresponding to the working mode is obtained_n. The equivalent dielectric constant of the inverted microstrip line can be calculated according to the following formula, and then the dielectric constant of the gas to be measured can be further deduced according to conformal transformation.

The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.