CN107091847B - A device and method for measuring electromagnetic parameters of dielectric materials - Google Patents

Abstract

The invention is suitable for the field of dielectric material measurement, and provides a dielectric material electromagnetic parameter measurement device and a measurement method. The dielectric material electromagnetic parameter measurement device includes: a microwave vector network analyzer; a special-shaped coaxial measurement fixture; and the special-shaped coaxial measurement fixtures are connected respectively. The input coaxial cable and the output coaxial cable at both ends of the measuring fixture; a GPIB data acquisition card connected to the microwave vector network analyzer, and a computer connected to the GPIB data acquisition card. The dielectric material electromagnetic parameter measuring device in the embodiment of the present invention takes advantage of the high measurement accuracy and transmission/reflection of the resonant cavity method by setting up a special-shaped coaxial measurement fixture and setting a test box for packaging the measurement sample in the special-shaped coaxial measurement fixture. The advantage of the method is to measure the frequency bandwidth, so that the dielectric material electromagnetic parameter measuring device has high measurement accuracy and a wide measurement frequency band. By setting up a microwave vector network analyzer and a computer to automatically analyze the measurement data, the measurement speed is fast.

Description

A device and method for measuring electromagnetic parameters of dielectric materials

Technical field

The invention belongs to the field of dielectric material measurement, and in particular relates to a dielectric material electromagnetic parameter measurement device and a measurement method.

Background technique

With the wide application of new materials in communications, computers, and defense industries, manufacturers and users have increasingly higher requirements for the measurement accuracy and measurement range of materials. Complex dielectric constant and complex permeability are the characteristics of dielectric materials. Important parameters of electromagnetic properties, how to meet the requirements of manufacturers and users for the measurement accuracy and measurement range of electromagnetic parameters such as complex dielectric constant and complex permeability of new materials under the new situation are new problems faced by microwave testing technology.

In the existing technology, electromagnetic parameters such as complex permittivity and complex permeability are usually measured using only one of the resonant cavity perturbation method, the free space method or the transmission/reflection method. Although the resonant cavity perturbation method has high measurement accuracy, the resonant cavity perturbation method can only measure electromagnetic parameters at one or a limited number of frequencies, and the measurement speed is slow; the free space method has a wide testing range, but its measurement accuracy is limited; transmission/reflection The measurement frequency of this method is wide, but when the sample thickness is an integer multiple of half the waveguide wavelength corresponding to the test frequency, the test method is unstable and prone to thickness resonance.

Therefore, the existing electromagnetic parameter measuring device for dielectric materials cannot simultaneously meet the requirements of fast measurement speed, wide measurement frequency, and high measurement accuracy.

Contents of the invention

The invention provides a device for measuring electromagnetic parameters of dielectric materials, aiming to solve the problem that the existing technology cannot achieve fast measurement speed, wide measurement frequency and high measurement accuracy at the same time.

The invention is implemented in this way. A device for measuring electromagnetic parameters of dielectric materials includes:

A microwave vector network analyzer, which includes a microwave signal output port, a microwave signal input port and a data output port;

Special-shaped coaxial measurement fixture, the special-shaped coaxial measurement fixture includes a first cavity, a middle measured sample cavity and a second cavity that are arranged in sequence and enclose a closed space, the first cavity, the middle measured sample cavity and the second cavity. The sample measuring chamber and the second chamber are coaxially arranged. The special-shaped coaxial measuring fixture also includes a first central column fixed in the first cavity and arranged coaxially with the first cavity. a second central column disposed in the first cavity and coaxial with the second cavity; and a second central column disposed in the intermediate measured sample cavity and located between the first central column and the second central column. test box between;

Input coaxial cable, one end of the input coaxial cable is connected to the microwave signal output port, and the other end is connected to the end of the first cavity away from the middle measured sample cavity and inputs into the first cavity electromagnetic waves;

Output coaxial cable, one end of the output coaxial cable is connected to the microwave signal input port, and the other end is connected to

One end of the second cavity away from the intermediate measured sample cavity outputs the electromagnetic wave in the second cavity;

GPIB data acquisition card, the input end of the GPIB data acquisition card is connected to the data output end;

A computer, which is connected to the output end of the GPIB data acquisition card.

The invention also provides a measurement method using the dielectric material electromagnetic parameter measurement device, which includes the following steps:

Place the measurement sample in the measurement box and seal it;

Connect the input coaxial cable and the output coaxial cable to calibration components respectively, connect the microwave vector network analyzer, the GPIB signal acquisition card and the computer, and perform calibration on the vector network analyzer. error calibration;

Connect the input coaxial cable and the output coaxial cable to the special-shaped coaxial measurement fixture respectively for transmission calibration;

Put the standard sample into the measurement position in the intermediate measured sample cavity, measure the corresponding electromagnetic parameters and input the corresponding electromagnetic parameters of the standard sample;

Take out the standard sample, put the test box containing the measurement sample into the measurement position in the cavity of the intermediate measured sample, and measure the corresponding electromagnetic parameters. The computer automatically calculates and displays the electromagnetic parameters of the measurement sample. parameters and save.

The dielectric material electromagnetic parameter measuring device in the embodiment of the present invention is configured by arranging the special-shaped coaxial measurement fixture to be coaxial and form a first cavity, an intermediate measured sample cavity and a second cavity in a closed space. A coaxial resonant cavity is formed, and a test box for packaging the measurement sample is set in the middle cavity, taking advantage of the high measurement accuracy of the resonant cavity method, thereby achieving high test accuracy; by using the computer to automatically calculate and display the measured electromagnetic Parameters, the measurement speed is fast, thereby making the measurement efficiency high; by setting the microwave vector network analyzer to automatically analyze the scattering parameters of the measurement sample, the advantage of the measurement frequency bandwidth of the transmission/reflection method is utilized, so that the measurement frequency bandwidth is wide. The measurement method using the dielectric material electromagnetic parameter measurement device provided by the embodiment of the present invention combines the advantages of the resonant cavity method and the transmission/reflection method, and has high measurement accuracy, fast measurement speed and wide measurement frequency band.

Description of the drawings

Figure 1 is a structural block diagram of a device for measuring electromagnetic parameters of dielectric materials provided by an embodiment of the present invention;

Figure 2 is a schematic structural diagram of a special-shaped coaxial measurement fixture of a device for measuring electromagnetic parameters of dielectric materials provided by an embodiment of the present invention;

Figure 3 is a schematic structural diagram from another angle of a special-shaped coaxial measurement fixture of a device for measuring electromagnetic parameters of dielectric materials provided by an embodiment of the present invention;

Figure 4 is a schematic structural diagram of the first support member of a device for measuring electromagnetic parameters of dielectric materials provided by an embodiment of the present invention;

FIG. 5 is a flow chart of a measurement method using a dielectric material electromagnetic parameter measurement device provided by an embodiment of the present invention.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention and are not intended to limit the present invention.

The dielectric material electromagnetic parameter measurement device provided by the embodiment of the present invention is configured by arranging the special-shaped coaxial measurement fixture to be coaxial and form a first cavity, an intermediate measured sample cavity, and a second cavity in a closed space. A coaxial resonant cavity is formed, and a test box for packaging the measurement sample is set in the middle cavity. During the measurement process, the test box is in a closed space, which eliminates the interference of the external electromagnetic field, protects the internal magnetic field, and utilizes resonance. The cavity method has the advantage of high measurement accuracy, thus making the measurement accuracy high; by setting the computer to automatically calculate and display the measured electromagnetic parameters, the measurement speed is fast; by setting the microwave vector network analyzer to automatically analyze the scattering parameters of the measured sample, using It takes advantage of the measurement frequency bandwidth of the transmission/reflection method and makes the measurement frequency bandwidth wide.

Please refer to Figures 1 to 3 in conjunction. Figure 1 shows a structural block diagram of a dielectric material electromagnetic parameter measurement device provided by an embodiment of the present invention; Figure 2 is a dielectric material electromagnetic parameter measurement device provided by an embodiment of the present invention. A schematic structural diagram of the special-shaped coaxial measurement fixture of the device; FIG. 3 is a schematic structural diagram of the special-shaped coaxial measurement fixture of a dielectric material electromagnetic parameter measurement device provided by an embodiment of the present invention from another angle. As an embodiment of the present invention, the dielectric material electromagnetic parameter measurement device includes:

Microwave vector network analyzer 1. The microwave vector network analyzer 1 includes a microwave signal output port, a microwave signal input port and a data output port;

Special-shaped coaxial measuring fixture 2. The special-shaped coaxial measuring fixture 2 includes a first cavity 21, a middle measured sample cavity 22 and a second cavity 23 that are arranged in sequence and enclose a closed space. The first cavity 21. The intermediate measured sample cavity 22 and the second cavity 23 are coaxially arranged. The special-shaped coaxial measurement fixture 2 also includes a measuring device fixed in the first cavity 21 and connected with the first cavity. The first central column 24 is coaxially arranged with the body 21, the second central column 25 is fixed in the second cavity 23 and is coaxially arranged with the second cavity 23, and is provided in the middle measured sample cavity. A test box 26 within the body 22 and located between the first center column 24 and the second center column 25;

Input coaxial cable 3. One end of the input coaxial cable 3 is connected to the microwave signal output port, and the other end is connected to the end of the first cavity 21 away from the middle measured sample cavity 22 and toward the third cavity. Electromagnetic waves are input into a cavity 21;

Output coaxial cable 4. One end of the output coaxial cable 4 is connected to the microwave signal input port, and the other end is connected to the end of the second cavity 23 away from the middle measured sample cavity 22 and outputs the third Electromagnetic waves in the second cavity 23;

GPIB data acquisition card 5, the input end of the GPIB data acquisition card 5 is connected to the data output end;

Computer 6. The computer 6 is connected to the output end of the GPIB data acquisition card 5.

The device for measuring electromagnetic parameters of dielectric materials provided by the invention has high testing accuracy, fast measurement speed and wide measurement frequency range when testing the electromagnetic parameters of dielectric materials.

In the embodiment of the present invention, the first cavity 21, the intermediate measured sample cavity 22 and the second cavity 23 form a coaxial resonant cavity, and the microwave vector network analyzer 1 generates electromagnetic waves and Electromagnetic waves are input into the first cavity 21 through the input coaxial cable 3. The electromagnetic waves are transmitted into the first cavity 21 through the first center column 24, and enter the first cavity 21 after being transmitted and reflected by the measurement sample. The second cavity 23 is then transmitted to the output coaxial cable 4 through the second central column 25 in the second cavity 23, and the electromagnetic wave is then input to the microwave signal input through the output coaxial cable 4. port, the microwave vector network analyzer 1 automatically analyzes the scattering parameter S of the measured sample, the GPIB data acquisition card 5 collects the data analyzed by the microwave vector network analyzer 1 and outputs it to the computer 6, the computer 6 Automatically calculate and display the electromagnetic parameters of the measured sample. By forming the first cavity 21, the intermediate sample cavity 22 and the second cavity 23 into a coaxial resonant cavity, the resonant cavity measurement method can be fully utilized to measure accurate Advantages: At the same time, by arranging the test box in the second cavity 23, the corresponding electromagnetic parameters are automatically analyzed and calculated after the electromagnetic wave is transmitted and reflected by the measurement sample, the measurement speed is fast, and the transmission/reflection is better utilized. Therefore, the dielectric material electromagnetic parameter measuring device has the advantages of high measurement accuracy, fast measurement speed and wide measurement frequency band.

As a practical application of the present invention, such as measuring complex dielectric constant and complex magnetic permeability parameters. Among them, the calculation principles of complex permittivity and complex permeability are as follows:

First, according to the formulas of complex permeability, complex permittivity and reflection coefficient:

(1)

(2)

Among them, Γ is the reflection coefficient, μr is the complex magnetic permeability, εr is the complex dielectric constant, T is the transmission coefficient, and L is the sample length;

Then according to the relationship between the scattering parameter S, reflection coefficient Γ and transmission coefficient T of the microwave signal output port and microwave signal input port of the microwave vector network analyzer:

(3)

(4)

Among them, S11 is the input reflection coefficient, and S21 is the output reflection coefficient.

Combining formulas (1), (2), (3), and (4), the values of complex permittivity and complex permeability are derived.

In the embodiment of the present invention, the first cavity 21 and the second cavity 23 are cone-shaped, and the inner diameter of the first cavity 21 gradually increases from one end where electromagnetic waves are input to the direction of the middle cavity 22 . The inner diameter of the second cavity 23 gradually increases from the end of the electromagnetic wave output toward the middle cavity 22 . At the same time, the inner diameter of the first center column 24 increases from the end of the electromagnetic wave input toward the middle cavity 22 . Gradually increases, the inner diameter of the second central column 25 gradually increases from one end of the output electromagnetic wave to the direction of the intermediate cavity 22. Since the cone-shaped structure conforms to the transmission/reflection theory, the measurement of high-order mode pairs can be reduced. influence on the results, thus improving the accuracy of the measurement.

One end of the first center column 24 and the second center column 25 close to the test box 26 is provided with a round head, which facilitates the transmission of electromagnetic fields.

One end of the first cavity 21 for inputting electromagnetic waves and one end of the first center column 25 form a first N-type adapter, and one end of the second cavity 23 for outputting electromagnetic waves and the second end of the second center column 25 One end of also forms a second N-type adapter, the input coaxial cable 3 is connected to the first N-type adapter, and the output coaxial cable 4 is connected to the second N-type adapter. Since The N-type adapter can be directly plugged into the coaxial cable, making the connection between the input coaxial cable 3 and the output coaxial cable 4 and the special-shaped coaxial measurement fixture 2 quick and easy.

As an embodiment of the present invention, the second center column 25 includes a fixed column 251 fixed in the second cavity 23 and a movable column 252 movably connected to the fixed column 251. The cylinder 252 is located on the side close to the test box 26 and can be telescopic along the length direction of the fixed cylinder 251 . By arranging one end of the second central column 25 into a telescopic structure, the length of the second central column 25 can be adjusted according to the length of the measurement sample and the movable column 252 can be pressed against the test box 26. Achieve measurement of samples of different lengths, making the measurement range wide.

As a preferred embodiment of the present invention, the fixed cylinder 251 is provided with a threaded hole, and the movable cylinder 252 includes a movable ball head 2521 that abuts the test box 26 and a movable ball head 2521 connected with the movable ball head 2521 . The threaded column 2522 is connected to the threaded hole through a threaded fit. The fixed column 251 and the movable ball head 2521 are connected to each other through threads. When adjusting the length of the second center column 25, the movable ball head 2521 can be realized by lightly twisting the movable ball head 2521. The length adjustment of the two central columns 25 is simple to operate.

The test box 26 is cylindrical, and has an opening for injecting a measurement sample. The test box 26 can hold solid or liquid measurement samples, and can meet the requirements for measurement of measurement samples in different states.

As an embodiment of the present invention, the special-shaped coaxial measurement fixture 2 further includes a first fixing member 27 fixed on the outer wall of the first cavity 21 and arranged around the first cavity 21. The second fixing members 28 are fixed on the outer walls of the two chambers 23 and are arranged around the second cavity 23, and the second fixing members 28 are respectively fixed on the opposite ends of the middle measured sample cavity 22 and are provided around the middle measured sample cavity 22. The third fixing part 29, the first fixing part 27 and the third fixing part 29 are connected by fasteners, the second fixing part 28 and the third fixing part 29 are connected by fasteners. A coaxial resonant cavity is formed, and the fasteners can be bolts, pins, etc., which are simple to disassemble and install, making it easy to replace different measurement samples, thereby making the test efficient.

As an embodiment of the present invention, the special-shaped coaxial measurement fixture 2 also includes a first support member 30 fixed to the first cavity 21 and used to support the first center column 24 and a second support member 30 fixed to the second central column 24 . The cavity 23 is also used to support the second support member 31 of the second center column 25 . The first supporting member 30 is arranged around the inner wall of the first cavity 21 , and the second supporting member 31 is arranged around the inner wall of the second cavity 23 , wherein the first supporting member 30 and the second supporting member 30 are arranged around the inner wall of the second cavity 23 . The number of supporting members 31 can be set according to actual needs. By arranging the first supporting member 30 and the second supporting member 31, the first center column 24 and the first cavity 21 are spaced apart from each other. The second central column 25 and the second cavity 23 are spaced apart from each other, and the first central column 24 and the first cavity 21 are kept coaxial, which is beneficial to the linear propagation of electromagnetic waves. As a preferred embodiment of the present invention, the first support member 30 and the second support member 31 are each provided in two and are spaced apart from each other. At this time, the first center column 24 and the second center column The column 25 is force-balanced and allows the first cavity 21 to maintain enough space for reflecting electromagnetic waves.

As a practical application of the present invention, the first support member 30 and the second support member 31 are both plastic support members, that is, the first support member 30 and the second support member 31 are both made of plastic material. The manufactured support piece can play a very good supporting and fixing role for the special-shaped coaxial measuring fixture 2, and makes the overall mass of the special-shaped coaxial measuring fixture 2 lighter.

Please refer to FIG. 4 , which shows a schematic structural diagram of the first support member of a device for measuring electromagnetic parameters of dielectric materials provided by an embodiment of the present invention. As an embodiment of the present invention, both the first support member 30 and the second support member 31 are provided with a plurality of through holes 302 that are spaced apart from each other and communicate with the middle measured sample cavity 22; In the embodiment, the first support member 30 and the second support member 31 have the same shape and structure, and both the first support member 30 and the second support member 31 are in a plum blossom shape, which can effectively reduce electromagnetic interference. Unnecessary high-order mode resonance is generated during the transmission process, which is beneficial to electromagnetic transmission.

The first support member 30 includes a main body part 301 arranged around the inner wall of the first cavity 21 , the through hole 302 penetrates the main body part 301 , and the first central column 24 penetrates the main body part 301 And it is coaxial with the main body 301, and this axis is colinear with the axis of the special-shaped coaxial measurement fixture 2. A plurality of the through holes 302 are arranged around the central axis of the first support 30, and a plurality of the through holes 302 are arranged around the central axis of the first support member 30. The diameter of the through hole 302 increases sequentially from the central axis of the first support member 30 and the second support member 31 toward the circumferential direction. In practical applications, the size of the through holes 302 can be set according to the internal distribution of the magnetic field. By increasing the diameters of the multiple through holes 302 from the inside to the outside, the error caused by the reflection coefficient and the transmission coefficient can be reduced. influence, thus improving the accuracy of measurement results.

The dielectric material electromagnetic parameter measurement device provided by the embodiment of the present invention is configured by arranging the special-shaped coaxial measurement fixture to be coaxial and form a first cavity, an intermediate measured sample cavity, and a second cavity in a closed space. A coaxial resonant cavity is formed between the three, and a test box for packaging the measurement sample is set up in the middle cavity. During the measurement process, the test box is in a closed space, which eliminates the interference of the external electromagnetic field and protects the internal magnetic field. , taking advantage of the advantages of high test accuracy of the resonant cavity method, so that the test accuracy is high; by setting the computer to automatically calculate and display the measured electromagnetic parameters, the measurement speed is fast, so that the measurement efficiency is high; by setting the microwave vector network analyzer to automatically The measurement sample scattering parameters are analyzed, and the advantages of the transmission/reflection method in the measurement frequency bandwidth are utilized to achieve a measurement bandwidth.

Please refer to FIG. 5 , which shows a flow chart of a method for measuring electromagnetic parameters of dielectric materials provided by an embodiment of the present invention. As an embodiment of the present invention, the method for measuring electromagnetic parameters of dielectric materials includes the following steps:

Step S1, place the measurement sample in the measurement box and seal it;

Step S2, connect the input coaxial cable and the input coaxial cable to calibration components respectively, and connect the microwave vector network analyzer, the GPIB signal acquisition card and the computer, and analyze the vector network The analyzer performs error calibration;

Step S3, connect the input coaxial cable and the output coaxial cable to the special-shaped coaxial measurement fixture respectively for transmission calibration;

Step S4: Place the standard sample into the measurement position in the intermediate measured sample cavity, test the corresponding electromagnetic parameters and input the corresponding electromagnetic parameters of the standard sample;

Step S5, take out the standard sample, put the test box containing the measurement sample into the measurement position in the middle measured sample cavity, and perform the corresponding electromagnetic parameter test. The computer automatically calculates and displays the measurement. Electromagnetic parameters of the sample and saved.

The measurement method provided by the embodiment of the present invention using the dielectric material electromagnetic parameter measurement device has high measurement accuracy, fast measurement speed and wide measurement frequency band.

In step S1, the dielectric material to be measured is made into powder or liquid form and evenly put into the measurement box 26, so that the solid or liquid dielectric material can be measured.

In step S2, a corresponding electronic calibration component can be selected according to the model of the microwave vector network analyzer 1 to perform error calibration on the microwave vector network analyzer 1.

In step S3, before placing the measurement sample, the electromagnetic wave transmission error measurement is performed on the special-shaped coaxial measurement fixture 2 to perform calibration according to the existing error and improve the accuracy of the measurement.

In step S4, a solid cylindrical standard sample of polytetrafluoroethylene is used. When testing, start the test software pre-installed in the computer 6 and select the corresponding test option. For example: when testing the complex dielectric constant, select the "Complex Dielectric Constant Measurement" option, and click the "Standard Measurement" option on the test software, enter the complex dielectric constant of the PTFE standard sample, and complete the complex dielectric constant of the standard sample. Measurement of electrical constants.

When testing the complex magnetic permeability, select the "Complex Magnetic Permeability Measurement" option, click the "Standard Measurement" option on the test software, enter the complex magnetic permeability of the PTFE standard sample, and complete the complex magnetic permeability of the standard sample. rate measurement.

In step S5, the measurement box 26 containing the measurement sample is placed at the measurement position in the intermediate measured sample cavity 22 and the special-shaped coaxial measurement fixture 2 is assembled. The computer 6 is selected to be pre-installed. Select the "Sample Measurement" option in the test software to perform measurement, and the computer 6 automatically calculates and displays the corresponding electromagnetic parameters of the measured sample.

For example: when testing the complex permittivity, if the "complex permittivity measurement" option is selected in step S4, the computer 6 will automatically calculate and display the corresponding complex permittivity of the measurement sample; when testing the complex permeability, When the "complex magnetic permeability measurement" option is selected in step S4, the computer 6 automatically calculates and displays the corresponding complex magnetic permeability of the measurement sample. The computer 6 automatically calculates and displays the measurement results of the measurement sample, with fast calculation speed and high measurement efficiency.

As an embodiment of the present invention, step S5 includes:

When there is only one measurement sample, the computer 6 automatically calculates and displays the electromagnetic parameters of the measurement sample and saves it before choosing to exit;

When there is more than one measurement sample, after measuring the previous measurement sample, change the next measurement sample and choose to enter the measurement of the electromagnetic parameters of the next measurement sample. After all measurement samples are tested, click on the computer 6 to save the document data and quit.

In practical applications, if more than one measurement sample needs to be measured, select the "next sample" option of the test software pre-installed on the computer 6 to test the next measurement sample, and so on, until all measurement samples are tested. When finished, click the computer 6 to save the document data and exit, and then the measurement of the electromagnetic parameters of all the measurement samples can be completed. When there are multiple measurement samples to be measured, there is no need to repeat the measurement steps of the standard sample in step S4, and the next sample can be directly tested, making the testing efficiency high.

The measurement method using the dielectric material electromagnetic parameter measurement device provided by the embodiment of the present invention combines the advantages of the resonant cavity method and the transmission/reflection method, and has high measurement accuracy, fast measurement speed and wide measurement frequency band.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (1)

1. A device for measuring electromagnetic parameters of dielectric materials, which is characterized in that it includes: A microwave vector network analyzer, which includes a microwave signal output port, a microwave signal input port and a data output port; Special-shaped coaxial measurement fixture, the special-shaped coaxial measurement fixture includes a first cavity, a middle measured sample cavity and a second cavity that are arranged in sequence and enclose a closed space, the first cavity, the middle measured sample cavity and the second cavity. The sample measuring chamber and the second chamber are coaxially arranged. The special-shaped coaxial measuring fixture also includes a first central column fixed in the first cavity and arranged coaxially with the first cavity. a second central column disposed coaxially with the second cavity and a second central column disposed in the intermediate measured sample cavity between the first central column and the second central column; test box between; Input coaxial cable, one end of the input coaxial cable is connected to the microwave signal output port, and the other end is connected to the end of the first cavity away from the middle measured sample cavity and inputs into the first cavity electromagnetic waves; Output coaxial cable, one end of the output coaxial cable is connected to the microwave signal input port, the other end is connected to the end of the second cavity away from the middle measured sample cavity and outputs the signal in the second cavity electromagnetic waves; GPIB data acquisition card, the input end of the GPIB data acquisition card is connected to the data output end; A computer, the computer is connected to the output end of the GPIB data acquisition card; The first cavity, the intermediate measured sample cavity and the second cavity form a coaxial resonant cavity, and the microwave vector network analyzer generates electromagnetic waves and transmits them to the first through the input coaxial cable. Electromagnetic waves are input into the cavity. The electromagnetic waves are transmitted to the first cavity through the first central column, enter the second cavity after being transmitted and reflected by the measurement sample, and then pass through the second second cavity in the second cavity. The central column is transmitted to the output coaxial cable, and the electromagnetic wave is then input into the microwave signal input port through the output coaxial cable. The microwave vector network analyzer automatically analyzes and measures the scattering parameter S of the sample, and the GPIB data acquisition card Collect the data analyzed by the microwave vector network analyzer and output it to the computer, and the computer automatically calculates and displays the electromagnetic parameters of the measured sample, Among them, the calculation principles of complex permittivity and complex permeability are as follows: First, according to the formulas of complex permeability, complex permittivity and reflection coefficient: (1) (2) Among them, Γ is the reflection coefficient, μr is the complex magnetic permeability, εr is the complex dielectric constant, T is the transmission coefficient, and L is the sample length; Then according to the relationship between the scattering parameter S, reflection coefficient Γ and transmission coefficient T of the microwave signal output port and microwave signal input port of the microwave vector network analyzer: (3) (4) Among them, S11 is the input reflection coefficient, and S21 is the output reflection coefficient; Combining formulas (1), (2), (3), and (4) to derive the values of complex permittivity and complex permeability; The first cavity and the second cavity are cone-shaped, and the inner diameter of the first cavity gradually increases from one end of the input electromagnetic wave toward the middle measured sample cavity, and the second cavity The inner diameter of the first central column gradually increases from the end of the electromagnetic wave output to the direction of the intermediate sample cavity, and at the same time, the inner diameter of the first center column gradually increases from the end of the electromagnetic wave input to the direction of the intermediate sample cavity, The inner diameter of the second center column gradually increases from the end where the electromagnetic wave is output toward the direction of the intermediate measured sample cavity; One end of the first center column and the second center column close to the test box are both configured with round heads; One end of the first cavity for inputting electromagnetic waves and one end of the first central column form a first N-type adapter, and one end of the second cavity for outputting electromagnetic waves is also formed with one end of the second central column. a second N-type adapter, the input coaxial cable is connected to the first N-type adapter, and the output coaxial cable is connected to the second N-type adapter; The second central column includes a fixed column fixed in the second cavity and a movable column movably connected to the fixed column. The movable column is located on one side close to the test box and along all sides. The length direction of the fixed column is telescopic; by setting one end of the second central column into a telescopic structure, the length of the second central column is adjusted according to the length of the measurement sample and the movable column is pressed against the test box; The fixed cylinder is provided with a threaded hole, and the movable cylinder includes a movable ball head that is in contact with the test box and a threaded column connected to the movable ball head. The threaded column is connected to the threaded hole. The fixed cylinder and the movable ball head are connected through a threaded fit; the fixed cylinder and the movable ball head are connected through a threaded fit; The test box is cylindrical, has an opening for injecting a measurement sample, and holds a solid or liquid measurement sample; The special-shaped coaxial measurement fixture also includes a first fixing member fixed on the outer wall of the first cavity and surrounding the first cavity, and a first fixing member fixed on the outer wall of the second cavity and surrounding the second cavity. A second fixing piece is provided and a third fixing piece is respectively fixed at the opposite ends of the intermediate sample cavity and is arranged around the middle sample cavity. The first fixing piece and the third fixing piece are The fixing parts are connected by fasteners, and the second fixing part and the third fixing part are connected by fasteners to form a coaxial resonant cavity, and the fasteners are bolts and pins; The special-shaped coaxial measurement fixture also includes a first support member fixed to the first cavity and used to support the first center column and a support member fixed to the second cavity and used to support the second center column. The second support member; the first support member is arranged around the inner wall of the first cavity, and the second support member is arranged around the inner wall of the second cavity, wherein the first support member and the second support member are arranged around the inner wall of the second cavity. The number of support members is set according to actual needs. By arranging the first support member and the second support member, the first center column and the first cavity are spaced apart from each other. The second center column The second cavity is spaced apart from each other, and the first central column and the first cavity are kept coaxial; The first support member and the second support member are both provided in two and spaced apart from each other; The first support member and the second support member are both plastic support members, that is, the first support member and the second support member are both support members made of plastic material; The first support member and the second support member each have a plurality of through holes spaced apart from each other and connected with the middle measured sample cavity; the first support member and the second support member The shapes and structures are the same, and the first support member and the second support member are both plum blossom-shaped; The first support member includes a main body portion arranged around the inner wall of the first cavity, the through hole penetrates the main body portion, and the first center column penetrates the main body portion and is co-located with the main body portion. The axis is collinear with the axis of the special-shaped coaxial measurement fixture. A plurality of through holes are arranged around the central axis of the first support member. The diameters of the plurality of through holes are respectively from the first support. The central axes of the member and the second support member gradually increase in the circumferential direction; The method for measuring electromagnetic parameters of dielectric materials includes the following steps: Step S1, place the measurement sample in the test box and seal it; Step S2, connect the input coaxial cable and the input coaxial cable to calibration components respectively, and connect the microwave vector network analyzer, the GPIB data acquisition card and the computer, and analyze the vector network The analyzer performs error calibration; Step S3, connect the input coaxial cable and the output coaxial cable to the special-shaped coaxial measurement fixture respectively for transmission calibration; Step S4: Place the standard sample into the measurement position in the intermediate measured sample cavity, test the corresponding electromagnetic parameters and input the corresponding electromagnetic parameters of the standard sample; Step S5, take out the standard sample, put the test box containing the measurement sample into the measurement position in the middle measured sample cavity, and perform the corresponding electromagnetic parameter test. The computer automatically calculates and displays the measurement. Electromagnetic parameters of the sample and save them; In step S1, the dielectric material to be measured is made into powder or liquid form and evenly put into the test box, and the solid or liquid dielectric material is measured; In step S2, select the corresponding electronic calibration component according to the model of the microwave vector network analyzer to perform error calibration on the microwave vector network analyzer; In step S3, before placing the measurement sample, the electromagnetic wave transmission error measurement is performed on the special-shaped coaxial measurement fixture to calibrate according to the existing error; In step S4, a solid cylindrical standard sample of polytetrafluoroethylene is used. When testing, start the test software pre-installed in the computer and select the corresponding test option; when testing the complex dielectric constant, select "Complex dielectric constant" Measure" option, and click the "Standard Measurement" option on the test software, enter the complex dielectric constant of the PTFE standard sample, and complete the measurement of the complex dielectric constant of the standard sample; when testing the complex permeability, select "Complex Permeability" "Permeability Measurement" option, and click the "Standard Measurement" option on the test software, enter the complex magnetic permeability of the PTFE standard sample, and complete the measurement of the complex magnetic permeability of the standard sample; In step S5, place the test box containing the measurement sample at the measurement position in the intermediate measured sample cavity and assemble the special-shaped coaxial measurement fixture. Select the test software pre-installed on the computer. "Sample measurement" option to perform measurement, the computer automatically calculates and displays the corresponding electromagnetic parameters of the measured sample; Step S5 includes: When there is only one measurement sample, the computer automatically calculates and displays the electromagnetic parameters of the measurement sample and saves it before choosing to exit; When there is more than one measurement sample, after measuring the previous measurement sample, change the next measurement sample and choose to enter the measurement of the electromagnetic parameters of the next measurement sample. After all measurement samples are tested, click the computer to save the document data and exit. ; When more than one measurement sample needs to be measured, select the "Next Sample" option of the test software pre-installed on the computer to test the next measurement sample, and so on. After all measurement samples are tested, click on the computer Save the document data and exit to complete the measurement of the electromagnetic parameters of all measurement samples; when there are multiple measurement samples that need to be measured, there is no need to repeat the measurement steps of the standard sample in step S4 and directly proceed to the test of the next sample.