CN111856151A - Material testing device and system for testing dielectric constant of wave-transparent material - Google Patents
Material testing device and system for testing dielectric constant of wave-transparent material Download PDFInfo
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- CN111856151A CN111856151A CN202010835415.6A CN202010835415A CN111856151A CN 111856151 A CN111856151 A CN 111856151A CN 202010835415 A CN202010835415 A CN 202010835415A CN 111856151 A CN111856151 A CN 111856151A
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R27/00—Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
- G01R27/02—Measuring real or complex resistance, reactance, impedance, or other two-pole characteristics derived therefrom, e.g. time constant
- G01R27/26—Measuring inductance or capacitance; Measuring quality factor, e.g. by using the resonance method; Measuring loss factor; Measuring dielectric constants ; Measuring impedance or related variables
- G01R27/2617—Measuring dielectric properties, e.g. constants
- G01R27/2635—Sample holders, electrodes or excitation arrangements, e.g. sensors or measuring cells
- G01R27/2658—Cavities, resonators, free space arrangements, reflexion or interference arrangements
- G01R27/2664—Transmission line, wave guide (closed or open-ended) or strip - or microstrip line arrangements
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R1/00—Details of instruments or arrangements of the types included in groups G01R5/00 - G01R13/00 and G01R31/00
- G01R1/02—General constructional details
- G01R1/18—Screening arrangements against electric or magnetic fields, e.g. against earth's field
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Abstract
The present invention provides a material testing device, comprising: a waveguide mount, a sleeve, a shield cap; the waveguide mounting piece comprises a waveguide cylinder and a cover body; a transmission cavity is arranged in the waveguide cylinder and the cover body; the waveguide cylinders of the two waveguide mounting pieces are respectively inserted into the inner hole of the sleeve from the left end and the right end of the sleeve; an air cavity is reserved in the middle of the sleeve; the cover bodies of the two waveguide mounting pieces are respectively connected with two ends of the sleeve; the two shielding caps are respectively screwed on the sleeve from the left end and the right end of the sleeve; the retracted inner edge of the shield cap contacts the cover of the waveguide mount and presses the cover rim completely within the shield cap. The invention also provides a system for testing the dielectric constant of the wave-transparent material, which comprises the material testing device. The invention can measure the dielectric constant of the wave-transparent material by a comparison test with an air cavity under the same environment.
Description
Technical Field
The invention relates to the technical field of material testing, in particular to a system for testing the dielectric constant of a wave-transparent material.
Background
With the wide application of millimeter wave radar in automatic driving, the test of millimeter wave radar antenna housing material is the leading requirement for researching and developing millimeter wave radar. For the test of the wave-transmitting material of the millimeter wave radar antenna housing, the measurement of the complex dielectric constant is particularly important.
At present, the testing methods which can be used for measuring the complex dielectric constant of the microwave dielectric material at home and abroad are various, and different methods exist according to the parameter range and the testing frequency range of the material to be tested during testing. In the frequency range of microwave and millimeter wave, the method can be divided into two categories, namely a network parameter method and a resonance method according to different testing principles. The two methods in the prior technical scheme have the advantages and the disadvantages respectively, the network parameter method has the greatest advantage of realizing continuous frequency sweep test, theoretically obtaining data of each frequency point in a test frequency range, and simultaneously realizing complex dielectric constant and complex permeability test of a high-loss material, and in addition, the test fixture is relatively simple to process and low in cost, and the defect is that the loss measurement precision of the low-loss material is not high. The resonance method is very suitable for testing the complex dielectric constant of the low-loss material, and the testing result can be very accurate by selecting a proper cavity as long as the quality factor is high enough. But the testing frequency is limited by the resonant frequency of the cavity, if a broadband test is to be realized, a multimode test is selected, and the frequency interval between adjacent resonant modes cannot be too large.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a material testing device and a system for testing the dielectric constant of a wave-transparent material, which can measure the dielectric constant of the wave-transparent material through a comparison test with an air cavity under the same environment.
In a first aspect, an embodiment of the present invention provides a material testing apparatus, including: two waveguide mounting pieces, a sleeve and two shielding caps;
the waveguide mounting part comprises a waveguide cylinder and a cover body connected to one end of the waveguide cylinder; a transmission cavity is arranged in the waveguide cylinder and the cover body; the waveguide cylinder is matched with the inner hole of the sleeve;
the waveguide cylinders of the two waveguide mounting pieces are respectively inserted into the inner hole of the sleeve from the left end and the right end of the sleeve; an air cavity is reserved in the middle of the sleeve; the cover bodies of the two waveguide mounting pieces are respectively connected with two ends of the sleeve; the radial size of the cover body of the waveguide mounting piece is larger than that of the inner hole of the sleeve;
external threads are arranged on the circumferential surfaces of the two ends of the sleeve; the shielding cap is a cylinder body with an inner shrinkage edge at one end; the other end of the shielding cap, which is far away from the inner shrinkage edge, is provided with an internal thread; the two shielding caps are respectively screwed on the sleeve from the left end and the right end of the sleeve; the inner shrinkage edge of the shielding cap is contacted with the cover body of the waveguide mounting piece, and the edge of the cover body is completely pressed in the shielding cap;
the outer end faces of the cover bodies of the two waveguide mounting pieces are used for being respectively in butt joint with the waveguide end of the spread spectrum transmitting module and the waveguide end of the spread spectrum receiving module.
Furthermore, the inner side of the cover body of the waveguide mounting piece is connected with a positioning pin, and the waveguide mounting piece is positioned through the positioning pin and the sleeve.
Further, the cover body of the waveguide mounting piece is connected with the end face of the sleeve through a set screw, and the thickness of the air cavity can be adjusted through adjusting the set screw.
Further, the waveguide cylinder is constructed integrally with the cover.
Further, the waveguide mounting piece, the sleeve and the shielding cap are all made of metal pieces.
In a second aspect, an embodiment of the present invention provides a system for testing a dielectric constant of a wave-transparent material, including: the device comprises a vector network analyzer, a spread spectrum transmitting module, any one of the material testing devices and a spread spectrum receiving module;
the waveguide end of the spread spectrum transmitting module and the waveguide end of the spread spectrum receiving module are respectively connected with a material testing device; the tail end of the spread spectrum transmitting module and the tail end of the spread spectrum receiving module are respectively connected with the vector network analyzer through coaxial cables.
The invention has the advantages that:
1) and the shielding cavity is adopted, so that unnecessary reflection and diffraction phenomena of other objects around the medium material to be detected are avoided.
2) The dielectric constant of the wave-transparent material is measured by adopting a contrast test with an air cavity, and compared with a traditional network parameter method, the measurement precision is higher while the broadband scanning test capability is achieved.
3) The assembly is simple, the material repeatability test is good, and the processing requirement on the medium material to be tested is simpler.
Drawings
Fig. 1 is a schematic diagram of a system for testing the dielectric constant of a wave-transparent material in an embodiment of the invention.
Fig. 2 is an exploded view of a material testing apparatus in an embodiment of the present invention.
Fig. 3a and 3b are schematic views of waveguide mounting members in embodiments of the invention.
Fig. 4 is a schematic structural diagram of a sleeve according to an embodiment of the present invention.
Fig. 5a and 5b are schematic views of the structure of the shielding cap in the embodiment of the invention.
FIG. 6 is a schematic diagram of a test state of air media in an air chamber according to an embodiment of the present invention.
FIG. 7 is a schematic diagram of a test condition for media material in an air cavity in an embodiment of the invention.
Fig. 8 is a flowchart of a measurement process in an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
An embodiment of the present invention provides a system for testing a dielectric constant of a wave-transparent material (hereinafter referred to as a test system), as shown in fig. 1, including: the device comprises a vector network analyzer 1, a spread spectrum transmitting module 2, a material testing device 3 and a spread spectrum receiving module 4; the waveguide end 201 of the spread spectrum transmitting module 2 and the waveguide end 401 of the spread spectrum receiving module 4 are respectively connected with the material testing device 3; the tail end of the spread spectrum transmitting module 2 and the tail end of the spread spectrum receiving module 4 are respectively connected with the vector network analyzer 1 through coaxial cables;
the application is mainly characterized in that the structure of the material testing device 3 is adopted, and the vector network analyzer 1, the spread spectrum transmitting module 2 and the spread spectrum receiving module 4 are only briefly introduced;
the vector network analyzer 1 consists of a signal source, a receiver and a display; a signal source sends a single-frequency signal to a material measuring device 3 through a spread spectrum transmitting module 2, a transmitting wave signal passing through the material measuring device 3 is transmitted to a receiver through a spread spectrum receiving module 4, the frequency is tuned to the receiving frequency, and a transmitting wave signal and a reflected wave signal of a medium material are detected (the transmitting wave signal and the reflected wave signal are received from the spread spectrum transmitting module 2 and sent to a receiver of a vector network analyzer 1); according to the measured response, the amplitude and phase data on the frequency can be obtained, the parameters of the complex reflection coefficient and the complex scattering parameter network characteristic are obtained, and then the complex dielectric constant and the complex magnetic permeability of the medium material to be measured are calculated and measured by loading the parameter change of the air cavity before and after the medium material to be measured through the contrast material measuring device 3;
as shown in fig. 2, the material testing apparatus 3 includes two waveguide mounts 302, a sleeve 304, two shielding caps 306; waveguide mount 302 is shown in fig. 3a, 3b, sleeve 304 is shown in fig. 4, and shield cap 306 is shown in fig. 5a, 5 b; the waveguide mounting piece 302, the sleeve 304 and the shielding cap 306 are all made of aluminum parts;
the waveguide mount 302 includes a waveguide cylinder 3021 and a cover 3022 attached to one end of the waveguide cylinder 3021; the waveguide cylinder 3021 and the cover 3022 may be integrally constructed; a transmission cavity 3023 is arranged in the waveguide cylinder 3021 and the cover 3022; waveguide cylinder 3021 fits into inner bore 3041 of sleeve 304;
the waveguide cylinders 3021 of the two waveguide mounts 302 are inserted into the inner holes 3041 of the sleeve 304 from the left and right ends of the sleeve 304, respectively; an air cavity 307 is reserved in the middle of the sleeve 304; the covers 3022 of the two waveguide mounts 302 are connected to the two ends of the sleeve 304, respectively; the body 3022 of the waveguide mount 302 has a radial dimension that is greater than the radial dimension of the bore 3041 of the sleeve 304;
the meaning of "connected" herein includes the direct connection of two objects or the indirect connection of two objects through a third object;
in some embodiments, the waveguide mount 302 has a detent pin 303 attached to the inside of the cover 3022 of the waveguide mount 302, and the waveguide mount 302 is positioned with the sleeve 304 by the detent pin 303;
in some embodiments, the cover 3022 of the waveguide mount 302 is attached to the end face of the sleeve 30 by a set screw 305, and the air cavity 307 thickness can be adjusted by adjusting the set screw 305;
in fig. 3a and 3b, the cover 3022 of the waveguide mount 302 has four holes near the edge, two of which are pin holes and two of which are set screw holes, for the positioning of the cover 3022 and the sleeve 304; four holes close to the port of the middle transmission cavity 3023 are two pin holes and the other two fixing screw holes, and the four holes are used for positioning and fixing the cover 3022 and the waveguide end 201 of the spread spectrum transmission module 2 or the waveguide end 401 of the spread spectrum reception module 4;
external threads are arranged on the circumferential surfaces of the two ends of the sleeve 304; the shield cap 306 is a cylinder with an internal flange 3061 at one end; the other end of the shield cap 306 away from the inner flange 3061 is provided with internal threads; two shielding caps 306 are respectively screwed on the sleeve 304 from the left end and the right end of the sleeve 304; the retracted inner edge 3061 of the shielding cap 306 contacts the cover 3022 of the waveguide mounting member 302 and presses the edge of the cover 3022 completely inside the shielding cap 306, so that the shielding cavity, i.e., the air cavity 307, inside the material testing apparatus 3 is electromagnetically shielded from the outside; when the medium material to be tested is placed in the air cavity 307 and isolated from the outside; the thickness of the air cavity is consistent with that of the medium material to be measured;
the outer end faces of the covers 3022 of the two waveguide mounting pieces 302 are respectively butted with the waveguide end 201 of the spread spectrum transmitting module 2 and the waveguide end 401 of the spread spectrum receiving module 4; the positioning and fixing can be carried out through the positioning pin and the fixing screw;
with the shield cap 306 and waveguide mount 302 removed from one end of the sleeve 304, the dielectric material 301 can be placed in the air cavity 307 in the sleeve; then the material testing device 3 is assembled;
the first and third test states are shown in fig. 6, and the second and fourth test states are shown in fig. 7; the first measurement and the third measurement are air medium measurement, the second measurement and the fourth measurement are medium material measurement, the first measurement air cavity and the second measurement medium material have the same physical size, the dielectric constant and the permeability parameter of the medium material are known, and the third measurement air cavity and the fourth measurement medium material have the same physical size;
the thickness of the media material 301 is consistent with the air cavity thickness; the measurement process is shown in fig. 7;
step S1: assembling a material testing device 3, connecting two ports of a vector network analyzer 1 with a spread spectrum transmitting module 2 and a spread spectrum receiving module 4 respectively, and starting a testing system;
step S2: initializing a vector network analyzer and setting basic parameters including initial frequency, termination frequency, point number and calibration type;
step S3: measuring and calibrating the vector network analyzer, after calibration is completed, respectively connecting the spread spectrum transmitting module and the spread spectrum receiving module to two ends of the material testing device 3, and entering a measuring stage;
step S4: inputting the thickness of a measurement air cavity, and measuring two ports of the air cavity;
step S5: loading a medium material with known measurement parameters, wherein the size thickness of the medium material is the same as the set thickness of the air cavity, and measuring the medium material with the known measurement parameters;
step S6: calculating the measurement results of S4 and S5 of two different medium materials (considered as air medium in S4), and verifying the test system through the two measurements;
step S7: inputting the thickness of a measurement air cavity, and measuring two ports of the air cavity;
step S8: loading a medium material to be measured, wherein the size thickness of the medium material is the same as the set thickness of the air cavity, and measuring the medium material to be measured;
step S9: according to the measurement results of S7 and S8 different medium materials (regarded as air medium in S7), analyzing and calculating the complex dielectric constant and complex permeability of the sample, and judging the accuracy of the calculation result through the check result of S6;
step S10: displaying and outputting the measurement result of S9;
step S11: and confirming whether the measurement of the material under the other frequencies is continued or not, if so, continuing to step S2, otherwise, ending the measurement in step S12.
The principle of measurement: when TEM waves (transverse electromagnetic waves) normally propagate in a free space and are incident on the surface of a dielectric material, because the wave impedance in the dielectric material is not equal to (lower than) the free space impedance, impedance mismatch occurs to generate reflected waves, meanwhile, a part of energy can penetrate through the dielectric material to form transmitted waves, once the waves enter the dielectric material, the wave speed becomes slower than the light speed, and because the dielectric material always generates certain loss, the waves can generate attenuation or insertion loss; the method comprises the steps of loading a medium material with known physical dimensions into a material testing device, regarding the medium material as a dual-port network during testing, measuring the reflection and transmission response changes of two ports, measuring parameters representing the network characteristics such as complex reflection coefficients and complex scattering parameters by using an instrument, and calculating the complex dielectric constant and the complex permeability of the medium material to be tested by using a calculation model of the medium material with the known measurement parameters in the air under the same state and combining an electromagnetic field theory.
Finally, it should be noted that the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, and although the present invention has been described in detail with reference to examples, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, which should be covered by the claims of the present invention.
Claims (6)
1. A material testing device (3), characterized by comprising: two waveguide mounts (302), a sleeve (304), two shielding caps (306);
the waveguide mounting piece (302) comprises a waveguide cylinder (3021) and a cover body (3022) connected to one end of the waveguide cylinder (3021); a transmission cavity (3023) is arranged in the waveguide cylinder (3021) and the cover body (3022); the waveguide cylinder (3021) is matched with the inner hole (3041) of the sleeve (304);
the waveguide cylinders (3021) of the two waveguide mounting pieces (302) are respectively inserted into the inner holes (3041) of the sleeve (304) from the left end and the right end of the sleeve (304); an air cavity (307) is reserved in the middle of the sleeve (304); the cover bodies (3022) of the two waveguide mounting pieces (302) are respectively connected with two ends of the sleeve (304); the radial dimension of the cover (3022) of the waveguide mount (302) is greater than the radial dimension of the inner bore (3041) of the sleeve (304);
external threads are arranged on the circumferential surfaces of the two ends of the sleeve (304); the shielding cap (306) is a cylinder body with an inner shrinkage edge (3061) at one end; the other end of the shielding cap (306) departing from the inner shrinkage edge (3061) is provided with internal threads; two shielding caps (306) are respectively screwed on the sleeve (304) from the left end and the right end of the sleeve (304); the indented inner edge (3061) of the shield cap (306) contacts the cover (3022) of the waveguide mount (302) and presses the cover (3022) rim completely within the shield cap (306);
the outer end faces of the covers (3022) of the two waveguide mounting pieces (302) are used for being respectively butted with the waveguide end (201) of the spread spectrum transmitting module (2) and the waveguide end (401) of the spread spectrum receiving module (4).
2. Material testing device (3) according to claim 1,
a positioning pin (303) is connected to the inner side of a cover body (3022) of the waveguide mounting piece (302), and the waveguide mounting piece (302) is positioned with the sleeve (304) through the positioning pin (303).
3. Material testing device (3) according to claim 1,
a cover body (3022) of the waveguide mounting piece (302) is connected to the end surface of the sleeve (304) by a set screw (305), and the thickness of the air chamber (307) can be adjusted by adjusting the set screw (305).
4. Material testing device (3) according to claim 1,
the waveguide cylinder (3021) and the lid body (3022) are integrally configured.
5. Material testing device (3) according to claim 1,
the waveguide mounting piece (302), the sleeve (304) and the shielding cap (306) are all made of metal pieces.
6. A system for measuring the dielectric constant of a wave-transparent material, comprising: a vector network analyzer (1), a spread spectrum transmission module (2), a material testing device (3) according to any one of claims 1 to 5, a spread spectrum reception module (4);
the waveguide end (201) of the spread spectrum transmitting module (2) and the waveguide end (401) of the spread spectrum receiving module (4) are respectively connected with the material testing device (3); the tail end of the spread spectrum transmitting module (2) and the tail end of the spread spectrum receiving module (4) are respectively connected with the vector network analyzer (1) through coaxial cables.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010835415.6A CN111856151A (en) | 2020-08-19 | 2020-08-19 | Material testing device and system for testing dielectric constant of wave-transparent material |
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| CN202010835415.6A CN111856151A (en) | 2020-08-19 | 2020-08-19 | Material testing device and system for testing dielectric constant of wave-transparent material |
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| CN111856151A true CN111856151A (en) | 2020-10-30 |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113970670A (en) * | 2021-09-29 | 2022-01-25 | 西安电子科技大学 | Foil strip air-mixed dielectric constant measuring method |
| CN114487618A (en) * | 2022-01-27 | 2022-05-13 | 北京航空航天大学 | Composite material low-frequency electromagnetic parameter equivalent extraction device and method |
-
2020
- 2020-08-19 CN CN202010835415.6A patent/CN111856151A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN113970670A (en) * | 2021-09-29 | 2022-01-25 | 西安电子科技大学 | Foil strip air-mixed dielectric constant measuring method |
| CN113970670B (en) * | 2021-09-29 | 2022-08-09 | 西安电子科技大学 | Foil strip air-mixed dielectric constant measuring method, system, equipment, medium and terminal |
| CN114487618A (en) * | 2022-01-27 | 2022-05-13 | 北京航空航天大学 | Composite material low-frequency electromagnetic parameter equivalent extraction device and method |
| CN114487618B (en) * | 2022-01-27 | 2022-08-23 | 北京航空航天大学 | Composite material low-frequency electromagnetic parameter equivalent extraction device and method |
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