A powder material complex permittivity test system and a calibration method thereof

Abstract

The application discloses a kind of powder material complex permittivity test system and its calibration method: including vector network analyzer, first wave same converter, second wave same converter, first waveguide, second waveguide, waveguide fixture, gasket, waveguide fixture is made of a group of different length waveguide pieces;When testing, two gaskets are respectively embedded in the two ports of the opposite sides of waveguide fixture, and the powder material to be measured is sealed in waveguide fixture;First waveguide and second waveguide are connected with straight-through calibration piece, and Thru calibration is carried out;First waveguide or second waveguide is connected with reflection calibration piece, and gasket and metal sheet are embedded in reflection calibration piece, and Reflect calibration is carried out;First waveguide and second waveguide are connected with transmission line calibration piece, and Line calibration is carried out.The application is equipped with waveguide fixture of different lengths simultaneously, ensures the measurement accuracy of powder material complex permittivity, removes the influence of gasket during calibration test, and the test process is simple and accurate.

Description

Technical Field

[0001] This invention relates to powder material dielectric property testing technology, and more specifically, to a powder material complex dielectric constant testing system and calibration method thereof. Background Technology

[0002] With the development of materials science, powder materials, with their unique microwave properties, are widely used as stealth materials, electronic device materials, biomimetic materials, etc. The dielectric properties of powder materials have become a basic requirement for the property analysis of various composite materials and new materials.

[0003] To obtain the complex permittivity of powder materials in the microwave band, there are currently three main types of measurement methods: single-end reflection method, resonant cavity method, and transmission reflection method. Each of these methods has its own specific application scenarios and advantages and disadvantages.

[0004] The single-ended reflection method is characterized by its online, non-destructive, and convenient nature. The complex permittivity of a powder can be calculated by inserting a single-ended probe into the powder and obtaining its reflection coefficient. However, the accuracy of the single-ended reflection method for measuring the complex permittivity of powder materials is not high. Furthermore, because it requires inserting a single-ended probe into the powder, the powder must be placed in a container of a certain volume and maintained at a specific capacity. This makes it unsuitable for powder materials with high sample preparation costs or rare powder materials.

[0005] The resonant cavity method involves placing the powder material at the point of strongest electric field in a resonant device. The complex permittivity of the material is then calculated by measuring the resonant frequency and loss factor (Q-value) before and after placement. The advantage of the resonant cavity method for powder material measurement is its suitability for low-loss materials; however, this method also has some limitations. Because it uses the resonant frequency and Q-value to calculate the complex permittivity, this method is limited to point-frequency or narrow-band applications. Furthermore, the measurement of powder characteristics using the resonant cavity method requires a sample placement container, increasing the complexity of the measurement and consequently reducing accuracy.

[0006] The transmission-reflection method requires mounting the powder material under test in a waveguide fixture, forming a system with a vector network analyzer and the waveguide fixture. The transmission and reflection coefficients of the powder material are then measured, and the complex permittivity is calculated. However, the transmission-reflection method requires calibrating the vector network analyzer using general-purpose waveguide calibration components, and then employing various embedding and de-embedding methods to remove the fixture's influence to obtain the complex permittivity. This results in numerous influencing factors and significant measurement errors. Furthermore, while the transmission-reflection method offers a wide bandwidth advantage for measuring the complex permittivity of powder materials, it requires installing baffles (shims) within the transmission line fixture to form a closed container. Therefore, special calibration techniques or algorithms are needed to remove the influence of the shims, which is a major challenge in measuring the complex permittivity of powder materials using the transmission-reflection method.

[0007] For X-band waveguide calibration kits from vector network analyzer manufacturers, such as Keysight (USA) using the X11644A mechanical calibration kit with TRL calibration, where the line thickness is 1 / 4 wavelength, similarly, R&S (Germany), Anritsu (Japan), and CETC (32117) (China) all use waveguide calibration kits, including shorting plates and 1 / 4 wavelength lines. Furthermore, waveguide calibration kit manufacturers can only offer general-purpose products, such as Maury (USA) WR90CK10, WR90CK12, WR90CK30, and WR90CK32, which are configured with SSLT and TRL calibration respectively. Keycom (Japan) can use X-band waveguides based on the transmission reflection method to measure the complex permittivity of high-loss materials such as electromagnetic wave absorbing materials (Model No. DPS08) and MC nylon (Model No. DPS09). Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of the prior art and provide a powder material complex permittivity testing system and its calibration method. This invention's system is equipped with waveguide fixtures of different lengths, further improving calibration efficiency and ensuring the measurement accuracy of the powder material's complex permittivity. During calibration and testing, the system uses embedded shims, directly defining the calibration reference surface on the powder material interface. This eliminates the influence of the shims during calibration. During testing, the complex permittivity of the powder material is directly calculated using the transmission reflection coefficient (S-parameter) through an NRW or four-parameter iterative model, without the need for de-embedding algorithms. The testing process is simple and highly accurate.

[0009] The objective of this invention can be achieved through the following technical solutions.

[0010] The present invention relates to a powder material complex permittivity testing system, comprising a vector network analyzer, a first wave-to-conversion converter, a second wave-to-conversion converter, a first waveguide, a second waveguide, a waveguide fixture, and a gasket. One end of the first waveguide is connected to the first wave-to-conversion converter, and the other end is connected to the waveguide fixture. One end of the second waveguide is connected to the second wave-to-conversion converter, and the other end is connected to the waveguide fixture. The first and second wave-to-conversion converters are respectively connected to port A and port B of the vector network analyzer via cables. The waveguide fixture is composed of a set of waveguide sheets of different lengths. During testing, the waveguide fixture of the corresponding length is selected according to the needs of different powder materials to be tested.

[0011] Two gaskets are provided. During testing, the powder material to be tested is filled inside the waveguide fixture. The two gaskets are respectively embedded in the two ports on opposite sides of the waveguide fixture. The exposed end faces of the two gaskets are flush with the end faces of the waveguide fixture on their respective sides, thus sealing the powder material to be tested inside the waveguide fixture.

[0012] The waveguide fixtures are configured with lengths of 4mm, 6mm, 8mm, 10mm, and 12mm; the 4mm, 8mm, and 12mm waveguide sheets can also be used as straight-through calibration pieces, reflection calibration pieces, and transmission line calibration pieces, respectively, during calibration.

[0013] The first waveguide, the second waveguide, and the waveguide fixture are all hollow structures with the same inner and outer diameters, and are arranged along a coaxial line. Both ends of the first waveguide, the second waveguide, and the waveguide fixture are provided with flange structures, and they are fixedly connected to each other by flanges and bolts. The first waveguide and the second waveguide have the same dimensions, and the radial dimension of the waveguide fixture is the same as the radial dimension of the first waveguide and the second waveguide.

[0014] The gaskets are made of 2mm thick Teflon, PVC, or transparent glass, and both gaskets are coaxial with the first waveguide, the second waveguide, and the waveguide clamp.

[0015] The objective of this invention can also be achieved through the following technical solutions.

[0016] The calibration method of the powder material complex permittivity testing system of the present invention first connects one end of the first wave converter to port A of the vector network analyzer via a cable, and the other end to the first waveguide. Then, one end of the second wave converter is connected to port B of the vector analyzer via a cable, and the other end to the second waveguide. TRL calibration is then performed, and the specific calibration process includes the following steps:

[0017] Step 1: Insert shims into both ends of the through calibration piece, and then connect the through calibration piece directly between the first waveguide and the second waveguide to perform Thru calibration; wherein, the through calibration piece is a hollow waveguide sheet with a length of 4mm, and a 2mm shim is inserted into each end;

[0018] Step 2: The first waveguide is fixedly connected to the reflection calibration component, which contains embedded shims and metal sheets for reflection calibration. The second waveguide is operated in the same way. The reflection calibration component is a hollow waveguide sheet with a length of 8mm, containing two 2mm shims and one 4mm metal sheet.

[0019] Step 3: Insert a shim into each end of the transmission line calibration piece, and then connect the transmission line calibration piece directly between the first waveguide and the second waveguide to perform line calibration; wherein, the transmission line calibration piece is a hollow waveguide sheet with a length of 12mm, and a 2mm shim is inserted into each end.

[0020] In the first step, the exposed end faces of the two gaskets are flush with the side end faces of the straight-through calibration component; the first waveguide, the straight-through calibration component, and the second waveguide are connected to each other by flanges and bolts.

[0021] In the second step, the exposed end face of the metal sheet is flush with the side end face of the reflection calibration component. The first waveguide and the reflection calibration component, and the second waveguide and the reflection calibration component are connected by flanges and bolts.

[0022] In the third step, the exposed end faces of the two gaskets are flush with the side end face where the transmission line calibration component is located, and there is an 8mm gap in the middle of the transmission line calibration component; the first waveguide, the transmission line calibration component, and the second waveguide are connected to each other by flanges and bolts.

[0023] Compared with the prior art, the beneficial effects of the technical solution of the present invention are:

[0024] Currently, the method for measuring powder materials using waveguide transmission lines based on transmission reflection is to first perform TRL calibration to obtain the S-parameters of the powder material being measured, which includes a gasket and the material under test. Then, the complex permittivity of the gasket material is known, and the S-parameters of the gasket are calculated. After removing the known S-parameters of the gasket, the S-parameters of the powder material under test are obtained. Finally, the complex permittivity of the powder material under test is calculated using NRW or a four-parameter model.

[0025] This invention directly embeds the gasket within its end face during calibration and testing, ensuring the end face is flush. This directly defines the calibration reference surface as the interface of the powder being tested, eliminating the gasket's influence. The results are identical to those for solid materials, improving the accuracy of powder material measurements. Furthermore, since the gasket's influence is not considered during calibration, the process is simplified, increasing operational convenience, efficiency, and measurement accuracy. During testing, the complex permittivity of the powder being tested is directly calculated using the transmission reflection coefficient through NRW or a four-parameter iterative model. This eliminates the need for de-embedding algorithms to remove the gasket's influence from the sandwich model, and avoids the cumbersome process or low accuracy issues associated with obtaining the powder's S-parameters before calculating the complex permittivity.

[0026] In addition, the present invention is equipped with waveguide fixtures of different lengths of 4mm, 6mm, 8mm, 10mm and 12mm, which can adapt to the measurement of complex permittivity of powder materials under different requirements and ensure the measurement accuracy of complex permittivity of powder materials. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the powder material complex permittivity testing system of the present invention.

[0028] Figure 2 These are schematic diagrams of waveguide clamps of different lengths in this invention.

[0029] Among them, (a) 4mm, (b) 6mm, (c) 8mm, (d) 10mm, and (e) 12mm.

[0030] Figure 3 This is a diagram of Thru calibration.

[0031] Figure 4 This is a schematic diagram of Reflect calibration, where (a) is the first waveguide and (b) is the second waveguide.

[0032] Figure 5 This is a diagram illustrating Line calibration.

[0033] Figure reference numerals: 1-Vector network analyzer, 2-First wave converter, 3-Second wave converter, 4-First waveguide, 5-Second waveguide, 6-Waveguide clamp, 7-Gap, 8-Cable, 9-Reflection calibrator, 10-Transmission line calibrator, 11-Straight-through calibrator, 12-Metal sheet. Detailed Implementation

[0034] The present invention will now be further described with reference to the accompanying drawings.

[0035] like Figure 1As shown, the powder material complex permittivity testing system of the present invention includes a vector network analyzer 1, a first wave-to-conversion converter 2, a second wave-to-conversion converter 3, a first waveguide 4, a second waveguide 5, a waveguide fixture 6, and a gasket 7. During testing, one end of the first waveguide 4 is connected to the first wave-to-conversion converter 2, and the other end is connected to the waveguide fixture 6; one end of the second waveguide 5 is connected to the second wave-to-conversion converter 3, and the other end is connected to the waveguide fixture 6; the first wave-to-conversion converter 2 and the second wave-to-conversion converter 3 are respectively connected to port A and port B of the vector network analyzer 1 via cables 8.

[0036] In the above system, the first waveguide 4, the second waveguide 5, and the waveguide clamp 6 are all hollow structures with the same inner and outer diameters, and are arranged along a coaxial line. The first waveguide 4 and the second waveguide 5 have the same dimensions, and the radial dimension of the waveguide clamp 6 is the same as that of the first waveguide 4 and the second waveguide 5. Each end of the first waveguide 4, the second waveguide 5, and the waveguide clamp 6 is provided with a flange structure, and they are fixedly connected to each other by flanges and bolts. The first waveguide 4 and the first wave-to-converter 2 are also fixedly connected by flanges and bolts, and the second waveguide 5 and the second wave-to-converter 3 are also fixedly connected by flanges and bolts.

[0037] like Figure 2 As shown, the waveguide fixture 6 is composed of a set of waveguide sheets of different lengths. During testing, the waveguide fixture 6 of the appropriate length is selected according to the needs of different powder materials to be tested, in order to meet different testing requirements. Specifically, the waveguide fixture 6 can use a set of waveguide sheets with lengths of 4mm, 6mm, 8mm, 10mm, and 12mm respectively. Among them, the 4mm and 6mm waveguide sheets can be used as micro-powder fixtures with small particle size and low loss, such as glass bead powder and PTFE powder, while the 8mm, 10mm, and 12mm waveguide sheets can be used as powder fixtures with large particle size, high loss, and appropriate quantity. In addition, the 4mm, 8mm, and 12mm waveguide sheets can also be used as straight-through calibration components, reflection calibration components, and transmission line calibration components during calibration, respectively.

[0038] Two gaskets 7 are provided. During testing, the powder material to be tested is filled inside the waveguide fixture 6, and the two gaskets 7 are respectively embedded in the two opposite ports of the waveguide fixture 6. The exposed end faces of the two gaskets 7 are flush with the end faces of the waveguide fixture 6 on their respective sides, sealing the powder material to be tested inside the waveguide fixture 6. The gaskets 7 are made of 2mm thick Teflon, PVC, or other common materials or transparent glass. Both gaskets 7 are coaxial with the first waveguide 4, the second waveguide 5, and the waveguide fixture 6.

[0039] The calibration method of the powder material complex permittivity testing system of the present invention first connects one end of the first wave converter 2 to port A of the vector network analyzer 1 via cable 8, and the other end to the first waveguide 4. Then, one end of the second wave converter 2 is connected to port B of the vector analyzer 1 via cable 8, and the other end to the second waveguide 5. Finally, TRL calibration is performed, and the specific calibration process includes the following steps:

[0040] Step 1: Insert a shim 7 into each end of the through calibration component, then connect the through calibration component directly between the first waveguide 4 and the second waveguide 5 to perform Thru calibration. Figure 3 As shown.

[0041] The straight-through calibration component 11 is a hollow waveguide sheet with a length of 4mm, with a 2mm gasket 7 embedded at each end. The exposed end faces of the two gaskets 7 are flush with the side end faces of the straight-through calibration component. Both ends of the straight-through calibration component 11 are provided with flange structures, and the first waveguide 4, the straight-through calibration component 11, and the second waveguide 5 can be connected to each other by flanges and bolts.

[0042] Step 2: After Thru calibration is completed, remove the through calibration component 11; embed the gasket 7 and metal sheet into both ends of the reflection calibration component 9, and then fix the reflection calibration component 9 to the first waveguide 4 for reflection calibration. The operation for the second waveguide 5 is the same. Figure 4 As shown.

[0043] The reflection calibration component 9 is a hollow waveguide sheet with a length of 8mm, incorporating two 2mm gaskets 7 and a 4mm metal sheet 12. The gaskets 7 are located between the metal sheet 12 and the connected first waveguide 4 (or second waveguide 5). The gaskets 7 are flush with the side end face of the reflection calibration component 9, and the exposed end face of the metal sheet is also flush with the side end face of the reflection calibration component 9. The first waveguide 4 and the reflection calibration component 9, and the second waveguide 5 and the reflection calibration component 9 are connected by flanges and bolts.

[0044] Step 3: After the Reflect calibration is completed, remove the Reflection Calibration 9; embed a gasket 7 into each end of the Transmission Line Calibration 10, and then directly connect the entire Transmission Line Calibration 10 between the first waveguide 4 and the second waveguide 5 to perform Line calibration. Figure 5 As shown.

[0045] The transmission line calibration component 10 is a hollow waveguide sheet with a length of 12mm, with a 2mm gasket 7 embedded at each end, and 8mm of air in the middle. The exposed end faces of the two gaskets 7 are flush with the side end face of the transmission line calibration component 10. The first waveguide 4, the transmission line calibration component 10, and the second waveguide 5 are connected to each other by flanges and bolts.

[0046] Unlike previous calibration methods, this invention uses a shim 7 embedded directly on the end face for TRL calibration during the calibration process. This directly defines the calibration reference surface at the interface of the powder material being tested, and the S-parameters of the powder material being tested can be obtained directly in one calibration. This avoids the tedious procedure of removing the calibration piece later and improves the measurement accuracy.

[0047] After completing the above three-step TRL calibration, the powder material to be tested is placed into a waveguide fixture 6 of appropriate size, and then the holes at both ends of the waveguide fixture 6 are sealed with two gaskets 7. The whole assembly is connected to the powder complex permittivity testing system for testing. After obtaining the S-parameters through the vector network analyzer, the complex permittivity of the powder material to be tested is calculated using the NRW or four-parameter iterative model.

[0048] This invention directly embeds the shim within its end face during calibration and testing, ensuring the end face is flush. This eliminates the influence of the shim during calibration and testing, simplifies the process, increases operational convenience, improves efficiency, and enhances the accuracy of powder material measurements. Furthermore, the invention utilizes waveguide fixtures of varying lengths to adapt to different requirements for measuring the complex permittivity of powder materials, ensuring the accuracy of the complex permittivity measurement.

[0049] Although the functions and working processes of the present invention have been described above in conjunction with the accompanying drawings, the present invention is not limited to the specific functions and working processes described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims, and all of these are within the protection scope of the present invention.

Claims

1. A powder material complex permittivity testing system, comprising a vector network analyzer (1), a first wave-to-converter (2), a second wave-to-converter (3), a first waveguide (4), a second waveguide (5), a waveguide fixture (6), and a gasket (7), wherein one end of the first waveguide (4) is connected to the first wave-to-converter (2), and the other end is connected to the waveguide fixture (6); one end of the second waveguide (5) is connected to the second wave-to-converter (3), and the other end is connected to the waveguide fixture (6); the first wave-to-converter (2) and the second wave-to-converter (3) are respectively connected to port A and port B of the vector network analyzer (1) via cables (8), characterized in that, The waveguide fixture (6) consists of a set of waveguide sheets of different lengths. During testing, the waveguide fixture (6) of the corresponding length is selected according to the needs of different powder materials to be tested. Two gaskets (7) are provided. During the test, the powder material to be tested is filled inside the waveguide fixture (6). The two gaskets (7) are respectively embedded in the two ports on opposite sides of the waveguide fixture (6). The exposed end faces of the two gaskets (7) are flush with the end faces of the waveguide fixture (6) on their respective sides, thus sealing the powder material to be tested inside the waveguide fixture (6).

2. The powder material complex permittivity testing system according to claim 1, characterized in that, The waveguide fixture (6) consists of five waveguide pieces with lengths of 4mm, 6mm, 8mm, 10mm and 12mm respectively; among them, the 4mm, 8mm and 12mm waveguide pieces can also be used as straight-through calibration pieces, reflection calibration pieces and transmission line calibration pieces during calibration.

3. The powder material complex permittivity testing system according to claim 1, characterized in that, The first waveguide (4), the second waveguide (5), and the waveguide clamp (6) are all hollow structures with the same inner and outer diameters, and are arranged along the same axis. Both ends of the first waveguide (4), the second waveguide (5), and the waveguide clamp (6) are provided with flange structures, and are fixedly connected to each other by flanges and bolts. The first waveguide (4) and the second waveguide (5) have the same dimensions, and the radial dimension of the waveguide clamp (6) is the same as the radial dimension of the first waveguide (4) and the second waveguide (5).

4. The powder material complex permittivity testing system according to claim 1, characterized in that, The gasket (7) is made of 2mm thick Teflon, PVC or transparent glass, and both gaskets (7) are coaxial with the first waveguide (4), the second waveguide (5) and the waveguide clamp (6).

5. A calibration method for the powder material complex permittivity testing system according to any one of claims 1 to 4, characterized in that, First, connect one end of the first wave converter (2) to port A of the vector network analyzer (1) via cable (8), and the other end to the first waveguide (4). Connect one end of the second wave converter (3) to port B of the vector network analyzer (1) via cable (8), and the other end to the second waveguide (5). Then perform TRL calibration. The specific calibration process includes the following steps: Step 1: Insert gaskets (7) into both ends of the through calibration piece, and then connect the through calibration piece directly between the first waveguide (4) and the second waveguide (5) to perform Thru calibration; wherein, the through calibration piece is a hollow waveguide sheet with a length of 4mm, and inserts a 2mm gasket (7) into both ends. Step 2: The first waveguide (4) is fixedly connected to the reflection calibration piece (9). The reflection calibration piece (9) has embedded gaskets (7) and metal sheets for reflection calibration. The second waveguide (5) is operated in the same way. The reflection calibration piece (9) is a hollow waveguide sheet with a length of 8mm, with two 2mm gaskets and one 4mm metal sheet embedded inside. Step 3: Insert a gasket (7) into each end of the transmission line calibration piece (10), and then connect the transmission line calibration piece (10) directly between the first waveguide (4) and the second waveguide (5) to perform line calibration; wherein, the transmission line calibration piece (10) is a hollow waveguide sheet with a length of 12mm, and a 2mm gasket (7) is inserted into each end.

6. The calibration method for the powder material complex permittivity testing system according to claim 5, characterized in that, In the first step, the exposed end faces of the two gaskets (7) are flush with the side end faces of the straight-through calibration component; the first waveguide (4), the straight-through calibration component, and the second waveguide (5) are connected to each other by flanges and bolts.

7. The calibration method for the powder material complex permittivity testing system according to claim 5, characterized in that, In the second step, the exposed end face of the metal sheet is flush with the side end face of the reflection calibration component (9). The first waveguide (4) and the reflection calibration component (9) are connected by flanges and bolts, and the second waveguide (5) and the reflection calibration component (9) are connected by flanges and bolts.

8. The calibration method for the powder material complex permittivity testing system according to claim 5, characterized in that, In the third step, the exposed end faces of the two gaskets (7) are flush with the side end face of the transmission line calibration component (10), and there is 8mm of air in the middle of the transmission line calibration component (10); the first waveguide (4), the transmission line calibration component (10), and the second waveguide (5) are connected to each other by flanges and bolts.

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