A method and system for measuring the relative dielectric constant of dielectric materials based on quasi-optical ellipsoidal mirror

Abstract

The present invention discloses a method and system for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoid mirror. The method comprises: constructing a quasi-optical ellipsoid mirror unit and setting a quasi-optical transmission optical path; performing TRL calibration on the quasi-optical transmission optical path; setting a rotatable dielectric material in the quasi-optical ellipsoid mirror unit so that the quasi-optical transmission optical path passes through the dielectric material; first obtaining S under cavity conditions; and finally obtaining the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoid mirror unit. 21 Curve and phase θ1, and then obtain S under the condition of setting the dielectric material loading cavity 21 The present invention can measure the relative permittivity of various dielectric materials, especially magnetic and anisotropic materials, at incident angles of 0° to 80°, with a relative error of less than 5%.

Description

Technical Field

[0001] The present invention relates to the field of testing the dielectric properties of millimeter wave dielectric materials, and in particular to a method and system for measuring the relative dielectric constant of dielectric materials based on a quasi-optical ellipsoidal mirror. Background Art

[0002] With the continuous advancement of information technology in modern society, the demand for spectrum resources is becoming increasingly urgent. Millimeter and submillimeter waves are attracting widespread attention and are of great significance in fields such as wireless communications, precision guidance, and aviation. As millimeter-wave frequencies increase, the shortcomings of traditional transmission lines, such as high loss, complex processing, and low power handling, become apparent. Quasi-optical technology has emerged to address these shortcomings. Using Gaussian beams, it can achieve lossless spatial focusing, addressing these shortcomings. Testing relative dielectric constants is one application of quasi-optical technology in the millimeter-wave band.

[0003] The relative dielectric constant is an important parameter for characterizing materials, because the speed of electromagnetic wave propagation in the medium, energy loss, reflection coefficient, etc. are related to it. Both the free space method and the traditional open cavity method have been successfully applied to the test of relative dielectric constant. Although the traditional open cavity method has a wide bandwidth and a high quality factor, it is only suitable for the test of the relative dielectric constant of low-loss dielectric materials. The free space method can achieve testing in higher frequency bands, because with the increase of frequency, the quasi-optical propagation tendency increases, which is convenient for testing and easy to tune. It is suitable for the test of electromagnetic parameters of high-loss and low-loss dielectric materials such as antenna covers. However, the free space method is not accurate enough in measuring the loss tangent, and is more suitable for high-loss or medium-loss materials. Therefore, how to achieve accurate measurement of relative dielectric constant in real applications and make the method applicable to various types of materials, especially the measurement of magnetic materials and anisotropic materials, is the problem that this application wants to solve. Summary of the Invention

[0004] Purpose of the invention: In response to the problems mentioned in the above-mentioned prior art and background technology, the present application proposes a method and system for measuring the relative dielectric constant of dielectric materials based on a quasi-optical ellipsoid mirror, which can realize the measurement of various types of materials, especially magnetic materials and anisotropic materials, thereby solving the defect that the current traditional open cavity can only test low-loss, isotropic dielectric materials.

[0005] Technical solution: A method for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoid mirror, comprising the following steps:

[0006] S1. Constructing a quasi-optical ellipsoidal mirror unit, and setting a quasi-optical transmission optical path based on the quasi-optical ellipsoidal mirror unit;

[0007] S2. Performing TRL calibration on the quasi-optical transmission optical path;

[0008] S3. After calibration, if the electric field distribution in the quasi-optical ellipsoidal mirror unit is normal and conforms to the beam waist transformation theory, proceed to step S3; otherwise, return to step S2;

[0009] S4. Obtain S under cavity conditions 21 curve and phase θ1;

[0010] S5. Set a rotatable dielectric material at the beam waist position of the quasi-light ellipsoid mirror so that the quasi-light transmission light path passes through the dielectric material to obtain S under the loading condition. 21 curve and phase θ2;

[0011] S6, calculating the phase difference Δθ between phase θ1 and phase θ2 at the same frequency point;

[0012] S7. Based on the phase θ1, the phase θ2 and the phase difference Δθ, inversely calculate the relative dielectric constant.

[0013] Furthermore, the method further includes the following steps:

[0014] S8. Change the frequency of the Gaussian beam input to the quasi-optical ellipsoidal mirror unit, return to step S4, invert the relative dielectric constant again, compare the consistency of the relative dielectric constants obtained in step S7 and step S8, and end the measurement and output the measurement result when the difference is less than the preset threshold, otherwise return to step S5.

[0015] Furthermore, in step S1, the process of constructing the quasi-optical transmission light path includes the following steps:

[0016] S9. Use at least a vector network analyzer, a Gaussian beam radiation horn, a Gaussian beam receiving horn, and a quasi-optical ellipsoidal mirror to construct the quasi-optical transmission optical path, wherein the Gaussian beam radiation horn and the Gaussian beam receiving horn are simultaneously connected to the vector network analyzer;

[0017] S10, the Gaussian beam radiation horn is used as a feed source, and its output end emits a Gaussian beam, and the Gaussian beam is reflected after secondary focusing in the quasi-optical ellipsoidal mirror to reach the Gaussian beam receiving horn.

[0018] Furthermore, in step S9, the Gaussian beam radiation horn uses a shaped horn, and the shaping curve of the shaped horn is a combination of at least three curves. From the input port to the output port of the horn, the first section uses sin p The second segment is in polynomial form, and the third segment is in hyperbolic form. The function expression of the shaped curve is:

[0019]

[0020] Among them, r i is the radius of the input surface of the shaped horn, r o is the radius of the output port of the shaped horn; ra r is the radius of the shaped horn at the end of the first curve; b is the radius of the shaped horn at the end of the second curve segment; L is the total length of the shaped horn; A, p1, and p2 are control parameters; in the direction from the input to the output of the shaped horn, the length of the first curve segment is denoted as a, the length of the second curve segment is denoted as (ba), and the length of the third curve segment is denoted as (Lb);

[0021] Set the waist radius of the Gaussian beam radiation horn to be larger than its operating wavelength.

[0022] Furthermore, in step S9, the quasi-light transmission optical path is a symmetrical structure, and the waist radius of the Gaussian beam incident on the quasi-light ellipsoidal mirror is set to w1, and the incident distance is d in , determine the exit beam waist radius w2 and exit distance d according to the test beam waist size and test distance required by the quasi-optical transmission optical path out ; Then the curvature radius R of the incident beam isophase surface in , the curvature radius R of the outgoing beam isophase surface out They are:

[0023]

[0024]

[0025] Where λ is the wavelength;

[0026] The curvature radius R of the incident beam isophase surface in , the curvature radius R of the outgoing beam isophase surface out The distances R1 and R2 from any point on the quasi-ellipsoidal mirror to the two focal points have the following relationship:

[0027] R1=R in

[0028] R2=R out

[0029] According to the geometric relationship between R1 and R2 of the quasi-optical ellipsoid, its major axis, minor axis and focal length values ​​are obtained, thereby obtaining the structural parameters of the quasi-optical ellipsoid.

[0030] A system for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoid, based on the method for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoid, is characterized in that the system at least comprises:

[0031] Quasi-optical ellipsoidal mirror;

[0032] The Gaussian beam radiation horn and the Gaussian beam receiving horn are respectively installed above the two quasi-optical ellipsoidal mirrors according to preset positions, so that the Gaussian beam is emitted by the Gaussian beam radiation horn, is secondary focused by the quasi-optical ellipsoidal mirror, and reaches the Gaussian beam receiving horn;

[0033] A dielectric material is provided between the two focal points of the quasi-optical ellipsoidal mirror and at the beam waist position of the quasi-optical ellipsoidal mirror, so that the Gaussian beam passes through the dielectric material;

[0034] A vector network analyzer, wherein the signal output terminal and the signal input terminal of the vector network analyzer are respectively connected to a Gaussian beam radiation horn and a Gaussian beam receiving horn;

[0035] A computer is connected to the vector network analyzer.

[0036] Furthermore, it also includes an angle adjustment structure, which is used to install the dielectric material and adjust the angle of the dielectric material.

[0037] Furthermore, the thickness of the dielectric material is less than half the wavelength corresponding to the center frequency of the frequency band applied by the relative dielectric constant measurement system, and the dielectric material is in the shape of a thin cylinder.

[0038] Beneficial effects: 1. Compared with the traditional waveguide cavity, the transmission cavity composed of the quasi-optical ellipsoidal mirror has a larger cavity size, which has lower requirements on the size and precision of the selected dielectric material, saving measurement time.

[0039] 2. The present invention has high accuracy in testing the relative dielectric constant of dielectric materials: the measurement system is based on the free space method and uses a vector network analyzer to obtain the S constant on the surface of the dielectric plate. 21 After the parameters are determined, the position deviation and thickness of the dielectric material are calibrated, and the accuracy of the measured relative dielectric constant is between 1% and 5%.

[0040] 3. The common waveguide horn that generates a basic Gaussian beam is a corrugated horn, but it is bulky, heavy, and inconvenient to process. The present invention adopts a shaped horn that is easy to process and low in cost, and designs it accordingly so that it can be applied to the present invention, which can effectively save measurement time.

[0041] 4. The present invention can realize the measurement of relative dielectric constant of various types of materials including low-loss and high-loss materials. The Q value domain of the traditional open cavity is related to the size of the internal energy storage. The shorter the wavelength, the smaller the cavity size, resulting in less energy storage, and is therefore more suitable for low-loss materials. The free space method can obtain broadband information of node characteristics and is a traveling wave measurement method. The measured scattering parameters are insensitive to the tiny loss of the material, and is therefore more suitable for the measurement of high-loss materials. The present invention uses an ellipsoidal mirror to form a transmission cavity and completes the measurement based on the free space method, so it is applicable to both low-loss and high-loss materials. In particular, the relative dielectric constant of anisotropic materials can be measured by adjusting the angle of the dielectric material.

[0042] 5. The present invention can measure the relative dielectric constant of dielectric materials under a wide range of incident wave angles: because the structure of the system avoids all components being on a horizontal line, the transmission distance is longer, the distance between the quasi-ellipsoidal mirrors is longer, and the space is larger. By rotating the dielectric material, the relative dielectric constant can be tested at different angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Flow chart of the measurement method of the present invention.

[0044] Figure 2 Schematic diagram of the structural principle of the measurement system of the present invention.

[0045] Figure 3 Schematic diagram of the transmission cavity structure of the present invention;

[0046] Figure 4 This is a theoretical schematic diagram of rotating the dielectric material around the x-direction by a preset angle in the present invention.

[0047] Figure 5 Schematic diagram of the structure of the Gaussian beam radiating horn and the Gaussian beam receiving horn of the present invention.

[0048] Figure 6 Schematic diagram of the inner wall contour of the shaped horn of the present invention.

[0049] Figure 7 Schematic cross-sectional view of the quasi-optical ellipsoidal mirror of the present invention.

[0050] Figure 8 This is a schematic structural diagram of a flat plate medium of the present invention.

[0051] Figures 1 to 8 The labels are: quasi-ellipsoidal mirror 1, Gaussian beam radiation horn 21, Gaussian beam receiving horn 22, dielectric material 3, vector network analyzer 4, computer 5. DETAILED DESCRIPTION

[0052] The present invention will be further explained below with reference to the accompanying drawings.

[0053] Based on the problems mentioned in the background technology, the free space method is not accurate enough in measuring the loss tangent, and is more suitable for the actual mining of high-loss or medium-loss materials. How to achieve accurate measurement of the relative dielectric constant and make the method applicable to various types of materials? This embodiment proposes a method for measuring the relative dielectric constant of dielectric materials based on a quasi-optical ellipsoid, such as Figure 1 As shown, this embodiment includes the following steps:

[0054] S1. Construct a quasi-optical ellipsoidal mirror unit and set a quasi-optical transmission optical path based on the quasi-optical ellipsoidal mirror unit;

[0055] S2. Perform TRL calibration on the optical transmission path;

[0056] S3. After calibration, observe the S 21 Check whether the curve is normal, the electric field distribution in the quasi-optical ellipsoidal mirror unit is normal and conforms to the beam waist transformation theory, and proceed to step S3, otherwise return to step S2; if there is a deviation, the position and parallelism can be fine-tuned;

[0057] S4. Obtain S under cavity conditions 21 curve and phase θ1;

[0058] S5. A dielectric material 3 is rotatably arranged at the beam waist position of the quasi-light ellipsoid mirror 1 so that the quasi-light transmission light path passes through the dielectric material 3 to obtain S under the loading condition. 21 curve and phase θ2.

[0059] S6, calculating the phase difference Δθ between phase θ1 and phase θ2 at the same frequency point, that is, the phase difference between input and output;

[0060] S7. Based on the phase θ1, the phase θ2, and the phase difference Δθ, the relative dielectric constant is obtained by inversion. The relative dielectric constant calculation formula of the dielectric material 3 is:

[0061] Δθ=θ1-θ2

[0062]

[0063] Where Δθ is the absolute value of the phase difference between the loading cavity and the cavity, f is the corresponding frequency value, t is the thickness of the dielectric material 3 to be measured, c is the speed of light, ε r is the relative dielectric constant of the dielectric material 3 to be measured.

[0064] In this embodiment, the actual test is based on the simulation test process. Before the actual test, the full-wave simulation software CST is first used to design and verify the transmission cavity parameters, check the S parameters of the quasi-optical ellipsoid mirror 1 and the distribution of the electric field at each cross-section plane, and verify whether the Gaussian transform is consistent with the theory. If the Gaussian beam can achieve its own restoration after passing through two ellipsoids, such as Figure 3 As shown in , the correctness of the transmission cavity can be proved.

[0065] Using S before and after loading the medium 21 The phase difference of the curve can also be used to invert the relative dielectric constant value at different frequencies. Compared with the theoretical value, the error is basically within 5%, which verifies the accuracy of the transmission cavity. The process of the actual test is similar to that of the simulation verification. First, the S 21 The curve is obtained and then the relative dielectric constant is inverted.

[0066] In the above solution, since there is a theoretical error between the measured value and the actual value, in order to reduce the error, this embodiment further includes the following steps:

[0067] S8. Change the output frequency of the Gaussian beam in the quasi-optical ellipsoidal mirror unit, return to step S4, invert the relative dielectric constant again, compare the consistency of the relative dielectric constants obtained in step S7 and step S8, and end the measurement and output the measurement result when the difference is less than the preset threshold value, otherwise return to step S5, the threshold value in this embodiment is 0-0.1; that is, when the consistency meets the threshold value, change the output frequency of the Gaussian beam in the quasi-optical ellipsoidal mirror unit again, calculate the relative dielectric constant, and output the relative dielectric constant, which is used as the relative dielectric constant of the dielectric material 3.

[0068] like Figure 2 As shown, the process of constructing a quasi-optical transmission optical path includes the following steps:

[0069] S9, using at least the vector network analyzer 4, the Gaussian beam radiation horn 21, the Gaussian beam receiving horn 22, and the quasi-light ellipsoid mirror 1 to construct a quasi-light output optical path; the Gaussian beam radiation horn 21 and the Gaussian beam receiving horn 22 are symmetrically arranged above the quasi-light ellipsoid mirror;

[0070] S10, the Gaussian beam radiation horn 21 is used as the feed source, and its output end emits a Gaussian beam. The Gaussian beam is reflected after secondary focusing in the quasi-optical ellipsoid mirror 1 and reaches the Gaussian beam receiving horn 22; the Gaussian beam radiation horn 21 and the Gaussian beam receiving horn 22 are simultaneously connected to the vector network analyzer.

[0071] Based on the above technical solution, the Gaussian beam radiation horn 21 adopts a shaped horn that is easy to process and low in cost, such as Figure 5As shown in the figure, the electromagnetic wave generated by the oscillator is converted into a Gaussian beam with the waist inside the horn antenna. In order to make the Gaussian beam wave propagate stably in free space, the size of the horn should be designed to ensure that the waist radius is larger than the working wavelength. Figure 6 As shown in the figure, the shaping curve of the shaping horn used in the present invention is composed of three curves connected and combined. In the direction from the input to the output of the shaping horn, sin is selected at 0~a. p The curve is in polynomial form at a~b and in hyperbola form at b~L. Its expression is:

[0072]

[0073] r i Enter the radius of the mouth surface for the shaped horn;

[0074] r o is the radius of the output surface of the shaped horn;

[0075] r a is the radius of the first curve cutoff point;

[0076] r b is the radius of the second curve cutoff point;

[0077] L is the total length of the shaped horn;

[0078] A, p1, and p2 are control parameters.

[0079] When using a traditional waveguide cavity, the shape type of the dielectric material 3 needs to be restricted, and some materials still need to be designed. The transmission cavity formed by the quasi-optical ellipsoidal mirror 1 has a larger cavity size, and thus has lower requirements on the size and precision of the selected dielectric material 3. In this embodiment, the quasi-optical ellipsoidal mirror 1 is in the shape of a metal ellipsoid. The quasi-optical ellipsoidal mirror 1 converges the Gaussian beam to the focus, and the quasi-optical ellipsoidal mirror 2 emits the beam starting from the focus. The cross-sectional view of the quasi-optical ellipsoidal mirror is shown in FIG. Figure 7 As shown, the major axis length is 2a, the minor axis length is 2b, the two foci are F1 and F2, the focal length is 2c, the length of the path PF1 from any point on the ellipsoid to one focus is R1, the length of the path PF2 to the other focus is R2, and the angle ∠F1PF2 is 2θ i , the angle of ∠PF1F2 is 2θ p , the incident beam is incident along the direction of PF1, and the reflected beam is emitted along the direction of PF1. The beam is compared to point P, which is the center point of the quasi-optical ellipsoid. The quasi-optical ellipsoid satisfies the equation:

[0080]

[0081] And satisfy the following geometric relationship:

[0082] R1+R2=2a

[0083]

[0084] b 2 =a 2 -(F1F2 / 2) 2

[0085] The equivalent focal length f satisfies:

[0086] f=R1R2 / (R1+R2)

[0087] It is known that the waist radius of the Gaussian beam incident on the quasi-optical ellipsoidal mirror is w1 and the incident distance is d in , the waist radius of the Gaussian beam after the reflector transformation is w2, and the emission distance is d out , the theoretical value is:

[0088]

[0089]

[0090] According to the solutions of the paraxial wave equation, we have:

[0091]

[0092]

[0093]

[0094] w(z) is the beam radius, i.e. the amplitude drops to the on-axis value

[0095] w0 is the waist radius of the beam;

[0096] R(z) is the radius of curvature of the Gaussian beam wavefront;

[0097] z0 is the confocal parameter;

[0098] k is the wave number.

[0099] Thus, the curvature radius R of the incident beam isophase surface can be obtained in for:

[0100]

[0101] Determine the exit beam waist radius w2 and exit distance d according to the test beam waist size and test distance required by the quasi-optical transmission optical path out , then the curvature radius R of the outgoing beam isophase surface out They are:

[0102]

[0103] Where λ is the wavelength.

[0104] Radius of curvature of the beam isophase surface R in and the curvature radius R of the phase plane of the outgoing beam out satisfy:

[0105] R1=R in

[0106] R2=R out

[0107] According to the geometric relationship between R1 and R2 of the quasi-optical ellipsoid, its major axis 2a, minor axis 2b and focal length are obtained, thereby obtaining the structural parameters of the quasi-optical ellipsoid, thus completing the design of the quasi-optical ellipsoid.

[0108] In this embodiment, since the system adopts a symmetrical structure, the waist radius of the Gaussian beam after the quasi-optical ellipsoidal mirror transformation is w2=w1, and the emission distance d out =d in .

[0109] Based on the above technical solution, a system for measuring the relative dielectric constant of dielectric material 3 based on quasi-optical ellipsoidal mirror is proposed. Figure 2 As shown, the system at least includes:

[0110] The quasi-optical ellipsoid mirror 1 is installed on a workbench;

[0111] The Gaussian beam radiation horn 21 and the Gaussian beam receiving horn 22 are respectively arranged above the two quasi-optical ellipsoid mirrors 1 and installed according to the preset positions so that the Gaussian beam is emitted by the Gaussian beam radiation horn 21, is secondary focused by the quasi-optical ellipsoid mirror 1, and reaches the Gaussian beam receiving horn 22;

[0112] The dielectric material 3 is arranged between the two focal points of the quasi-optical ellipsoid mirror 1 and located at the beam waist position of the quasi-optical ellipsoid mirror, and the Gaussian beam passes through the dielectric material 3;

[0113] A vector network analyzer 4, wherein the signal output terminal and the signal input terminal of the vector network analyzer 4 are respectively connected to the Gaussian beam radiation horn 21 and the Gaussian beam receiving horn 22;

[0114] The computer 5 is connected to the vector network analyzer 4 .

[0115] When in use, the following process is included:

[0116] 1. Build a measurement system based on the quasi-optical ellipsoidal mirror 1 and set up the quasi-optical transmission optical path. The quasi-optical ellipsoidal mirror 1 is located directly above the Gaussian beam radiation horn 2l. The entire system is bilaterally symmetrical.

[0117] 2. Check the stability, parallelism and position accuracy of the system, and prepare the dielectric material to be tested. It can be any type including magnetic and anisotropic materials.

[0118] 3. Turn on the vector network analyzer 4 and preheat it for half an hour to stabilize the frequency source. Next, set the frequency band and the number of frequency sweep points. Then, connect the coaxial lines of the two ports of the vector network analyzer 4 to the Gaussian beam radiation horn 21 and the Gaussian beam receiving horn 22, and perform TRL calibration on the system.

[0119] 4. Observe S on the spectrum 21 Check whether the curve is normal, ensuring that the electric field distribution in the cavity is normal and the beam waist transformation conforms to the theoretical value. If there is any deviation, the position and parallelism can be fine-tuned;

[0120] 5. Obtain S under cavity conditions 21 Curve, recording S under cavity conditions 21 The phase of the curve is θ1;

[0121] 6. Place the dielectric material 3 at the center of the system, which is the beam waist position of the collimating ellipsoidal mirror 1, fix it with a clamp with a scale, and rotate the dielectric material 3 to the corresponding angle according to the scale;

[0122] 7. Obtain S under the loading condition of dielectric material 3 at this angle 21 Curve, record S under loading conditions 21 The phase of the curve is θ2;

[0123] 8. Calculate the phase difference Δθ based on the obtained cavity phase θ1 and the phase θ2 after loading the dielectric material 3;

[0124] 9. Complete the inverse calculation of relative dielectric constant based on the inserted phase shift at the same frequency point;

[0125] 10. Change the frequency and perform multiple inversions of the relative dielectric constant to observe the consistency. If the consistency is within 0.1, end the calculation.

[0126] The above technical solution also includes an angle adjustment structure for mounting dielectric material 3 and adjusting its angle according to specified requirements. This angle adjustment structure enables the system to be applied to the measurement of the relative dielectric constant of anisotropic materials. The angle adjustment structure in this embodiment is a conventional structure, which can be configured in a variety of ways. It only needs to ensure that dielectric material 3 rotates at the center of the two quasi-ellipsoidal mirrors 1. Specifically, it can be configured to rotate around the three axes (X, Y, and Z).

[0127] In this application, the type of dielectric material 3 is any type, the shape of dielectric material 3 is any shape, the center of dielectric material 3 is on the same horizontal line as the center of the quasi-optical ellipsoid, and dielectric material 3 is located at the center of the two focal points of the quasi-optical ellipsoid 1. Dielectric material 3 can achieve high-precision measurement of relative dielectric constant at different angles of 0° to 80°.

[0128] The thickness of the dielectric material 3 is less than half the wavelength corresponding to the center frequency, and the dielectric material 3 is preferably in a thin cylindrical shape.

[0129] The above are only preferred embodiments of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoid, characterized in that: The following steps are involved: S1. Constructing a quasi-optical ellipsoidal mirror unit, and setting a quasi-optical transmission optical path based on the quasi-optical ellipsoidal mirror unit; S2. Performing TRL calibration on the quasi-optical transmission optical path; S3. After calibration, if the electric field distribution in the quasi-optical ellipsoidal mirror unit is normal and conforms to the beam waist transformation theory, proceed to step S3; otherwise, return to step S2; S4. Obtain S under cavity conditions 21 curve and phase θ1; S5. Set a rotatable dielectric material at the beam waist position of the quasi-light ellipsoid mirror so that the quasi-light transmission light path passes through the dielectric material to obtain S under the loading condition. 21 curve and phase θ2; S6, calculating the phase difference Δθ between phase θ1 and phase θ2 at the same frequency point; S7. Based on the phase θ1, the phase θ2 and the phase difference Δθ, inversely calculate the relative dielectric constant.

2. The method for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoid mirror according to claim 1, characterized in that: The following steps are also included: S8. Change the frequency of the Gaussian beam input to the quasi-optical ellipsoidal mirror unit, return to step S4, invert the relative dielectric constant again, compare the consistency of the relative dielectric constants obtained in step S7 and step S8, and end the measurement and output the measurement result when the difference is less than the preset threshold, otherwise return to step S5.

3. The method for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoid mirror according to claim 1, wherein: In step S1, the process of constructing a quasi-optical transmission light path includes the following steps: S9. Use at least a vector network analyzer, a Gaussian beam radiation horn, a Gaussian beam receiving horn, and a quasi-optical ellipsoidal mirror to construct the quasi-optical transmission optical path, wherein the Gaussian beam radiation horn and the Gaussian beam receiving horn are simultaneously connected to the vector network analyzer; S10, the Gaussian beam radiation horn is used as a feed source, and its output end emits a Gaussian beam, and the Gaussian beam is reflected after secondary focusing in the quasi-optical ellipsoidal mirror to reach the Gaussian beam receiving horn.

4. The method for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoid mirror according to claim 3, wherein: In step S9, the Gaussian beam radiation horn uses a shaped horn, and the shaping curve of the shaped horn is a combination of at least three curves. From the input port to the output port of the horn, the first section uses sin p The second segment is in polynomial form, and the third segment is in hyperbolic form. The function expression of the shaped curve is: Among them, r i is the radius of the input surface of the shaped horn, r o is the radius of the output port of the shaped horn; r a r is the radius of the shaped horn at the end of the first curve; b is the radius of the shaped horn at the end of the second curve segment; L is the total length of the shaped horn; A, p1, and p2 are control parameters; in the direction from the input to the output of the shaped horn, the length of the first curve segment is denoted as a, the length of the second curve segment is denoted as (ba), and the length of the third curve segment is denoted as (Lb); Set the waist radius of the Gaussian beam radiation horn to be larger than its operating wavelength.

5. The method for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoid mirror according to claim 3, wherein: In step S9, the quasi-light transmission optical path is a symmetrical structure, and the waist radius of the Gaussian beam incident on the quasi-light ellipsoidal mirror is set to w1, and the incident distance is d in , determine the exit beam waist radius w2 and exit distance d according to the test beam waist size and test distance required by the quasi-optical transmission optical path out ; Then the curvature radius R of the incident beam isophase surface in , the curvature radius R of the outgoing beam isophase surface out They are: Where λ is the wavelength; The curvature radius R of the incident beam isophase surface in , the curvature radius R of the outgoing beam isophase surface out The distances R1 and R2 from any point on the quasi-ellipsoidal mirror to the two focal points have the following relationship: R1=R in R2=R out According to the geometric relationship between R1 and R2 of the quasi-optical ellipsoid, its major axis, minor axis and focal length values ​​are obtained, thereby obtaining the structural parameters of the quasi-optical ellipsoid.

6. A system for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoid, based on the method for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoid as claimed in any one of claims 1 to 5, characterized in that: The system comprises at least: Quasi-optical ellipsoidal mirror; The Gaussian beam radiation horn and the Gaussian beam receiving horn are respectively installed above the two quasi-optical ellipsoidal mirrors according to preset positions, so that the Gaussian beam is emitted by the Gaussian beam radiation horn, is secondary-focused by the quasi-optical ellipsoidal mirror, and reaches the Gaussian beam receiving horn; A dielectric material is provided between the two focal points of the quasi-optical ellipsoidal mirror and at the beam waist position of the quasi-optical ellipsoidal mirror, so that the Gaussian beam passes through the dielectric material; A vector network analyzer, wherein the signal output terminal and the signal input terminal of the vector network analyzer are respectively connected to a Gaussian beam radiation horn and a Gaussian beam receiving horn; A computer is connected to the vector network analyzer.

7. The system for measuring the relative dielectric constant of dielectric materials based on a quasi-optical ellipsoid mirror according to claim 6, characterized in that: The device also includes an angle adjustment structure, which is used to install the dielectric material and adjust the angle of the dielectric material.

8. The system for measuring the relative dielectric constant of dielectric materials based on a quasi-optical ellipsoid mirror according to claim 7, characterized in that: The thickness of the dielectric material is less than half the wavelength corresponding to the center frequency of the frequency band applied by the relative dielectric constant measurement system, and the dielectric material is in a thin cylindrical shape.

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