CN116298535A - Method and system for measuring relative dielectric constant of dielectric material based on quasi-optical ellipsoidal mirror - Google Patents
Method and system for measuring relative dielectric constant of dielectric material based on quasi-optical ellipsoidal mirror Download PDFInfo
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Abstract
The invention discloses a method and a system for measuring relative dielectric constant of a dielectric material based on a quasi-optical ellipsoidal mirror, wherein the method comprises the following steps: constructing a quasi-optical ellipsoidal mirror unit and setting a quasi-optical transmission light path; aligning the light transmission path to perform TRL calibration; a rotatable medium material is arranged in the quasi-optical ellipsoidal mirror unit, so that a quasi-optical transmission light path passes through the medium material; first obtain S under the cavity condition 21 Curve and phase theta 1 Then S under the condition of setting a medium material loading cavity is acquired 21 Curve and phase theta 2 The method comprises the steps of carrying out a first treatment on the surface of the Calculating the phase θ 1 Phase θ 2 The phase difference delta theta at the same frequency point; based on phase theta 1 Phase θ 2 And inverting the relative dielectric constant with the phase difference Δθ. The invention can measure various dielectric materials, especially magnetic materials and anisotropic materials, and simultaneously realize the measurement of the relative dielectric constant of the dielectric materials at the incidence angle of 0-80 degrees, and the relative error of the test result is within 5%.
Description
Technical Field
The invention relates to the field of testing of dielectric properties of millimeter wave dielectric materials, in particular to a method and a system for measuring relative dielectric constants of dielectric materials based on a quasi-optical ellipsoidal mirror.
Background
With the continuous innovation of information technology in modern society, the requirements on spectrum resources are more urgent, millimeter waves and sub-millimeter waves are widely focused, and the method has important significance in the fields of wireless communication, accurate guidance, aviation and the like. Along with the rise of millimeter wave frequency, the defects of large loss, complex processing, small bearing power and the like of the traditional transmission line are revealed, the quasi-optical technology is generated, the Gaussian beam can be transmitted in the space beam without loss, the defect of the traditional transmission line is overcome, and the test of the relative dielectric constant is one of the applications of the quasi-optical technology in the millimeter wave frequency band.
The relative permittivity is an important parameter characterizing a material, as the speed of propagation of electromagnetic waves in a medium, the energy loss, the reflection coefficient, etc. are related thereto. Both free space and traditional open cavity methods have been successfully applied to the test of relative dielectric constants, and traditional open cavity methods, although having a high frequency bandwidth and quality factor, are only suitable for the test of relative dielectric constants of low-loss dielectric materials. The free space method can realize the test of higher frequency band, because the quasi-optical propagation tendency is enhanced along with the increase of frequency, the test is convenient, the tuning is easy, the method is suitable for the test of electromagnetic parameters of low-loss dielectric materials such as high loss and radome, but the free space method is not accurate enough in the aspect of measuring loss tangent, and is more suitable for high-loss or medium-loss materials. Therefore, how to realize accurate measurement of the relative dielectric constant in real application and the method is applicable to various types of materials, especially measurement of magnetic materials and anisotropic materials is a problem to be solved by the application.
Disclosure of Invention
The invention aims to: aiming at the problems in the prior art and the background art, the application provides a method and a system for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoidal mirror, which realize the measurement of various types of materials, especially magnetic materials and anisotropic materials, thereby solving the defect that the traditional open cavity can only test low-loss isotropic dielectric materials.
The technical scheme is as follows: a method for measuring relative dielectric constant of dielectric material based on quasi-optical ellipsoidal mirror includes the following steps:
s1, constructing a quasi-optical ellipsoidal mirror unit, and setting a quasi-optical transmission light path based on the quasi-optical ellipsoidal mirror unit;
s2, performing TRL calibration on the quasi-optical transmission light path;
s3, after calibration, the electric field distribution in the quasi-optical ellipsoidal mirror unit is normal and accords with the beam waist transformation theory, and the step S3 is carried out, otherwise, the step S2 is returned;
s4, under the condition of acquiring cavity S 21 Curve and phase theta 1 ；
S5, arranging a rotatable medium material at the beam waist position of the quasi-optical ellipsoidal mirror to enable the quasi-optical transmission light path to penetrate through the medium material, and acquiring S under the loading condition 21 Curve and phase theta 2 ；
S6, calculating phase theta 1 Phase θ 2 The phase difference delta theta at the same frequency point;
s7, based on the phase theta 1 Phase θ 2 And inverting the phase difference delta theta to obtain the relative dielectric constant.
Further, the method also comprises the following steps:
and S8, changing the frequency of the Gaussian beam input into the quasi-optical ellipsoidal mirror unit, returning to the step S4, inverting the relative dielectric constant again, comparing the consistency of the relative dielectric constants obtained in the step S7 and the step S8, ending the measurement and outputting a measurement result when the difference is smaller than a preset threshold, and otherwise returning to the step S5.
Further, in step S1, the process of constructing the quasi-optical transmission path includes the following steps:
s9, constructing the quasi-light transmission light path by using at least a vector network analyzer, a Gaussian beam radiation horn, a Gaussian beam receiving horn and a quasi-light ellipsoidal mirror, 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 loudspeaker is used as a feed source, the output end of the Gaussian beam radiation loudspeaker sends Gaussian beams, and the Gaussian beams are reflected to the Gaussian beam receiving loudspeaker after secondary focusing in a quasi-optical ellipsoidal mirror.
Further, in step S9, the gaussian beam radiation horn is a shaped horn, where the shaped hornThe shaping curve of the loudspeaker is a connection combination of at least three curves, and sin is selected as the first section from the input port to the output port of the loudspeaker p The curve, the second section selects polynomial form, the third section selects hyperbolic form, the function expression of the shaping curve is:
wherein r is i To shape the radius of the input port face of the horn, r o The radius of the output port surface of the shaping horn is set; r is (r) a The radius of the shaped horn at the cut-off of the first section of curve is set; r is (r) b The radius of the shaped horn at the cut-off position of the second section of curve is given; l is the total length of the shaped horn; A. p is p 1 、p 2 Is a control parameter; in the direction from the input port to the output port of the shaping horn, the length of the first section of curve is denoted as a, the length of the second section of curve is denoted as (b-a), and the length of the third section of curve is denoted as (L-b);
the beam waist radius of the Gaussian beam radiation horn is set to be larger than the working wavelength of the Gaussian beam radiation horn.
Further, in step S9, the quasi-optical transmission path is a symmetrical structure, and a beam waist radius w of the gaussian beam incident on the quasi-optical ellipsoidal mirror is set 1 An incident distance d in Determining the radius w of the emergent beam waist according to the size of the test beam waist and the test distance required by the quasi-optical transmission light path 2 And exit distance d out The method comprises the steps of carrying out a first treatment on the surface of the Radius of curvature R of the equiphase surface of the incident beam in Radius of curvature R of equiphase surface of outgoing beam out The method comprises the following steps of:
wherein λ is the wavelength;
radius of curvature R of equiphase surface of incident beam in Radius of curvature R of equiphase surface of outgoing beam out Distance R from any point on quasi-optical ellipsoidal mirror to two focuses 1 、R 2 The following relationship exists:
R 1 ＝R in
R 2 ＝R out
r according to quasi-optical ellipsoidal mirror 1 、R 2 The geometric relation of the (2) is used for obtaining the major axis, the minor axis and the focal length value of the (b) so as to obtain the structural parameters of the quasi-optical ellipsoidal mirror.
A system for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoidal mirror, and a method for measuring the relative dielectric constant of the dielectric material based on the quasi-optical ellipsoidal mirror, which is characterized by at least comprising the following steps:
a quasi-optical ellipsoidal mirror;
the Gaussian beam radiation horn and the Gaussian beam receiving horn are respectively and correspondingly arranged above the two quasi-optical ellipsoidal mirrors according to preset positions, so that Gaussian beams are emitted through the Gaussian beam radiation horn, secondarily focused through the quasi-optical ellipsoidal mirrors and reach the Gaussian beam receiving horn;
the medium material is arranged between the two focuses of the quasi-optical ellipsoidal mirror and is positioned at the beam waist position of the quasi-optical ellipsoidal mirror, so that the Gaussian beam passes through the medium material;
the signal output end and the signal input end of the vector network analyzer are respectively connected with a Gaussian beam radiation loudspeaker and a Gaussian beam receiving loudspeaker in a corresponding way;
and the computer is connected with the vector network analyzer.
Further, the device also comprises an angle adjusting structure, wherein the angle adjusting structure is used for installing the dielectric material and can adjust the angle of the dielectric material.
Further, the thickness of the dielectric material is smaller than half 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.
The beneficial effects are that: 1. compared with the traditional waveguide cavity, the cavity size of the transmission cavity formed by the quasi-optical ellipsoidal mirror is larger, so that the requirements on the size and the precision of the selected dielectric material are lower, and the measurement time is saved.
2. The invention has high test precision on the relative dielectric constant of the dielectric material: the measuring system is based on a free space method, and S on the surface of the dielectric plate is obtained by using a vector network analyzer 21 After parameters, the deviation and thickness of the dielectric material position are calibrated, and the measured relative dielectric constant precision is between 1% and 5%.
3. The common waveguide horn generating the basic Gaussian beam is a corrugated horn, but the waveguide horn has the advantages of huge volume, large mass and inconvenient processing.
4. The invention can realize the measurement of the relative dielectric constants of various materials with low loss, high loss and the like, and the energy storage size in the Q value range of the traditional open cavity is relevant, and the small cavity size causes less energy storage when the wavelength is short, so that the invention is more suitable for low-loss materials; the free space method can obtain broadband information of node characteristics, is a traveling wave measurement method, and the measured scattering parameter is insensitive to the tiny loss of the material, so that the method is more suitable for measuring the high-loss material. The invention utilizes the ellipsoidal mirror to form the transmission cavity and completes measurement based on a free space method, thereby being applicable to low-loss materials and high-loss materials. In particular, the measurement of the relative permittivity of anisotropic materials can be achieved by angular adjustment of the dielectric material.
5. The invention can realize the measurement of the relative dielectric constant of the dielectric material under the incident wave with a large range of angles: because the structure of the system avoids that all the original elements are on a horizontal line, the transmission distance is longer, the distance between the quasi-optical ellipsoidal mirrors is longer, the space is larger, and the relative dielectric constants under different angles can be tested by rotating the dielectric materials.
Drawings
FIG. 1 is a flow chart of a measurement method of the present invention.
Fig. 2 is a schematic diagram of the structural principle of the measuring system of the present invention.
FIG. 3 is a schematic view of a transmission chamber structure according to the present invention;
FIG. 4 is a schematic diagram of the present invention for rotating a dielectric material by a predetermined angle about the x-direction.
Fig. 5 is a schematic diagram of the gaussian beam radiation horn and gaussian beam receiving horn according to the present invention.
Fig. 6 is a schematic view of the shape of the inner wall profile of the shaped horn of the present invention.
Fig. 7 is a schematic cross-sectional view of a quasi-optical ellipsoidal mirror of the present invention.
FIG. 8 is a schematic view of one of the structures of the flat panel medium of the present invention.
The labels of fig. 1-8 are: the device comprises a quasi-optical ellipsoidal mirror 1, a Gaussian beam radiation horn 21, a Gaussian beam receiving horn 22, a dielectric material 3, a vector network analyzer 4 and a computer 5.
Detailed Description
The invention is further explained below with reference to the drawings.
Based on the problems mentioned in the background art, the free space method is not accurate enough in terms of measuring loss tangent, is more suitable for actual mining of high-loss or medium-loss materials, and is suitable for various types of materials, how to realize accurate measurement of relative dielectric constants, and the embodiment provides a method for measuring the relative dielectric constants of dielectric materials based on a quasi-optical ellipsoidal mirror, as shown in fig. 1, and the embodiment comprises the following steps:
s1, constructing a quasi-optical ellipsoidal mirror unit, and setting a quasi-optical transmission light path based on the quasi-optical ellipsoidal mirror unit;
s2, aligning the light transmission light path to perform TRL calibration;
s3, after calibration, observing S on the frequency spectrum 21 If the curve is normal, the electric field distribution in the quasi-optical ellipsoidal mirror unit is normal and accords with the beam waist transformation to accord with theory, the step S3 is carried out, otherwise, the step S2 is returned; if the deviation exists, the position and the parallelism can be finely adjusted;
s4, under the condition of acquiring cavity S 21 Curve and phase theta 1 ；
S5, rotatably arranging a dielectric material at the beam waist position of the quasi-optical ellipsoidal mirror 1Material 3, making quasi-light transmission light path pass through medium material 3 to obtain S under loading condition 21 Curve and phase theta 2 。
S6, calculating phase theta 1 Phase θ 2 The phase difference delta theta at the same frequency point, namely the phase difference between input and output;
s7, based on phase θ 1 Phase θ 2 And inverting the phase difference delta theta to obtain a relative dielectric constant, wherein the relative dielectric constant calculation formula of the dielectric material 3 is as follows:
Δθ＝θ 1 -θ 2
wherein delta theta 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 medium material 3 to be measured, c is the light velocity, epsilon r Is the relative dielectric constant of the dielectric material 3 to be measured.
In this embodiment, the physical test is based on a simulation test flow, and before the physical test is performed, the full-wave simulation software CST is first used to design and verify the parameters of the transmission cavity, check the S parameter of the quasi-optical ellipsoidal mirror 1, and the distribution of the electric field at each section plane, and verify whether the gaussian transformation accords with the theory, if the gaussian beam passes through two ellipsoids, the self-reduction can be realized, as shown in fig. 3, the correctness of the transmission cavity can be verified.
By S before and after loading the medium 21 The phase difference of the curves can also be used for inverting the values of the relative dielectric constants of different frequency points, and compared with the theoretical value, the error is basically within 5%, so that the accuracy of the transmission cavity is verified. The flow of the physical test is similar to the flow of the simulation verification, and S is carried out under the conditions of cavity and loading 21 And obtaining a curve, and inverting the relative dielectric constant.
In the above scheme, since there is a theoretical error between the measured value and the actual value, in order to reduce the error, the present embodiment further includes the following steps:
s8, changing the Gaussian beam output frequency in the quasi-optical ellipsoidal mirror unit, returning to the step S4, inverting the relative dielectric constant again, comparing the consistency of the relative dielectric constants obtained in the step S7 and the step S8, ending the measurement and outputting a measurement result when the difference value is smaller than a preset threshold value, otherwise returning to the step S5, wherein the threshold value in the embodiment is 0-0.1; namely, under the condition that the consistency meets the threshold value, the Gaussian beam output frequency in the quasi-optical ellipsoidal mirror unit is changed again, the relative dielectric constant is calculated and is output, and the relative dielectric constant is used as the relative dielectric constant of the dielectric material 3.
As shown in fig. 2, the process of constructing the quasi-optical transmission path includes the steps of:
s9, constructing a quasi-light output light path by using at least the vector network analyzer 4, the Gaussian beam radiation horn 21, the Gaussian beam receiving horn 22 and the quasi-light ellipsoidal mirror 1; the Gaussian beam radiation loudspeaker 21 and the Gaussian beam receiving loudspeaker 22 are symmetrically arranged above the quasi-optical ellipsoidal mirror;
s10, a Gaussian beam radiation horn 21 is used as a feed source, the output end of the Gaussian beam radiation horn is used for emitting Gaussian beams, and the Gaussian beams are reflected to a Gaussian beam receiving horn 22 after being focused for 1 time in a quasi-optical ellipsoidal mirror and reach 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.
Based on the above technical scheme, the gaussian beam radiation horn 2l adopts a shaping horn which is easy to process and low in cost, and as shown in fig. 5, electromagnetic waves generated by an oscillator are converted into a gaussian beam form, and the beam waist is arranged inside the horn antenna. In order to make Gaussian beam stably propagate in free space, the beam waist radius is ensured to be larger than the working wavelength when the size of the horn is designed. As shown in FIG. 6, the shaping curves of the shaping horn used in the present invention are formed by connecting and combining three curves, sin is selected from 0 to a in the direction from the input port to the output port of the shaping horn p The curve, a-b, is in a polynomial form, and b-L is in a hyperbolic form, and the expression is:
r i the radius of the input port surface of the shaped loudspeaker is set;
r o the radius of the output port surface of the shaping horn is set;
r a radius at the cut-off of the first section of curve;
r b radius at the cut-off of the second section of curve;
l is the total length of the shaped horn;
A，p 1 ，p 2 is a control parameter.
When the conventional waveguide cavity is used, the shape type of the dielectric material 3 needs to be limited, part of the materials also need to be designed, and the cavity size of the transmission cavity formed by the quasi-optical ellipsoidal mirror 1 is larger, so that the size and precision requirements of the selected dielectric material 3 are lower. The cross-sectional view of the quasi-optical ellipsoidal mirror is shown in FIG. 7, in which the length of the major axis is 2a, the length of the minor axis is 2b, and the two focuses are F 1 And F 2 A focal length of 2c, a path PF from any point on the ellipsoid to a focal point 1 Is of length R 1 Path PF to another focus 2 Is of length R 2 ，∠F 1 PF 2 Is 2 theta in angle i ，∠PF 1 F 2 Is 2 theta in angle p Incident beam along PF 1 Directional incidence, reflected beam along PF 1 The beam is emergent in the direction and is the center point of the quasi-optical ellipsoidal mirror compared with the P point. The quasi-optical ellipsoidal mirror satisfies the equation:
and satisfies the following geometric relationship:
R 1 +R 2 ＝2a
b 2 ＝a 2 -(F 1 F 2 /2) 2
the equivalent focal length f satisfies:
f＝R 1 R 2 /(R 1 +R 2 )
the beam waist radius of a Gaussian beam incident on a quasi-optical ellipsoidal mirror is known as w 1 An incident distance d in The beam waist radius of the Gaussian beam transformed by the reflector is w 2 The emergent distance is d out Theoretical values are:
solutions according to paraxial wave equations are:
w (z) is the beam radius, i.e. the amplitude drops to an on-axis value
w 0 Is the beam waist radius of the beam;
r (z) is the radius of curvature of the gaussian beam wavefront;
z 0 is a confocal parameter;
k is the wave number.
Thereby obtaining the radius of curvature R of the equiphase surface of the incident beam in The method comprises the following steps:
determining the radius w of the emergent beam waist according to the size of the test beam waist and the test distance required by the quasi-optical transmission light path 2 And exit distance d out Radius of curvature R of the equiphase surface of the outgoing beam out The method comprises the following steps of:
where λ is the wavelength.
Radius of curvature R of beam equiphase surface in Radius of curvature R of the equiphase surface of outgoing beam out The method meets the following conditions:
R 1 ＝R in
R 2 ＝R out
r according to quasi-optical ellipsoidal mirror 1 、R 2 The geometric relationship of the lens is obtained to obtain the long axis 2a, the short axis 2b and the focal length value, so that the structural parameters of the quasi-optical ellipsoidal mirror are obtained, and the design of the quasi-optical ellipsoidal mirror is completed.
In this embodiment, since a symmetrical structure is adopted in the system, the beam waist radius w of the gaussian beam after being transformed by the quasi-optical ellipsoidal mirror 2 ＝w 1 Distance d of emergence out ＝d in 。
Based on the above technical solution, a system for measuring the relative dielectric constant of a dielectric material 3 based on a quasi-optical ellipsoidal mirror is provided, as shown in fig. 2, the system at least includes:
a quasi-optical ellipsoidal mirror 1, wherein the quasi-optical ellipsoidal mirror 1 is arranged on a workbench;
the Gaussian beam radiation horn 21 and the Gaussian beam receiving horn 22 are respectively and correspondingly arranged above the two quasi-optical ellipsoidal mirrors 1, and are arranged according to preset positions, so that Gaussian beams are emitted through the Gaussian beam radiation horn 21, secondarily focused through the quasi-optical ellipsoidal mirrors 1 and reach the Gaussian beam receiving horn 22;
the dielectric material 3 is arranged between two focuses of the quasi-optical ellipsoidal mirror 1 and positioned at the beam waist position of the quasi-optical ellipsoidal mirror, and Gaussian beams pass through the dielectric material 3;
the signal output end and the signal input end of the vector network analyzer 4 are respectively connected with a Gaussian beam radiation horn 21 and a Gaussian beam receiving horn 22 correspondingly;
and a computer 5 connected to the vector network analyzer 4.
When in use, the method comprises the following steps:
1. setting up a measuring system based on a quasi-optical ellipsoidal mirror 1, setting a quasi-optical transmission light path, wherein the quasi-optical ellipsoidal mirror 1 is positioned right above a Gaussian beam radiation loudspeaker 2l, and the whole system is bilaterally symmetrical;
2. checking the stability, parallelism and position accuracy of the system, and accurately measuring the dielectric material 3 to be measured, which can be any type including magnetic and anisotropic materials;
3. the vector network analyzer 4 is opened to preheat for half an hour to stabilize a frequency source, then frequency band and sweep frequency point number are set, then coaxial lines of two ports of the vector network analyzer 4 are connected to the Gaussian beam radiation horn 21 and the Gaussian beam receiving horn 22, and TRL calibration is carried out on the system;
4. observing S on the frequency spectrum 21 Whether the curve is normal or not ensures that the electric field distribution in the cavity is normal and the beam waist transformation accords with a theoretical value, if the deviation exists, the position and the parallelism can be finely adjusted;
5. acquisition of S under Cavity conditions 21 Curve, record S under cavity condition 21 The phase of the curve is theta 1 ；
6. Placing a dielectric material 3 in the center of the system, namely, the beam waist position of the quasi-optical ellipsoidal mirror 1, fixing the dielectric material 3 by using a clamp with scales, and rotating the dielectric material 3 to a corresponding angle according to the scales;
7. acquisition of S under loading of dielectric Material 3 at this angle 21 Curve, record S under loading condition 21 The phase of the curve is theta 2 ；
8. Based on the obtained cavity phase theta 1 And phase θ after loading of dielectric material 3 2 Calculating a phase difference delta theta;
9. according to the inserted phase shift at the same frequency point, completing inversion calculation of the relative dielectric constant;
10. and (4) changing the frequency to perform inversion of the relative dielectric constant for a plurality of times, observing consistency, and ending calculation if the consistency is within 0.1.
Based on the technical scheme, the device further comprises an angle adjusting structure, wherein the angle adjusting structure is used for installing the dielectric material 3 and adjusting the angle of the dielectric material 3 according to specified requirements. The system is applicable to the measurement of the relative dielectric constant of anisotropic materials through the angle adjusting structure. The angle adjusting structure in this embodiment is an existing structure, and has many structures, and only needs to meet the requirement that the dielectric material 3 rotates at the center positions of the two quasi-optical ellipsoidal mirrors 1, and specifically, can be set to rotate around the XYZ three axes respectively.
In the application, the type of the dielectric material 3 is any type, the shape of the dielectric material 3 is any shape, the center of the dielectric material 3 and the center of the quasi-optical ellipsoidal mirror are positioned on the same horizontal line, the dielectric material 3 is positioned at the centers of two focuses of the quasi-optical ellipsoidal mirror 1, and the dielectric material 3 can realize high-precision measurement of relative dielectric constants under different angles of 0-80 degrees.
The thickness of the dielectric material 3 is smaller than half a wavelength corresponding to the center frequency, and the dielectric material 3 is preferably thin cylindrical.
The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.
Claims (8)
1. The method for measuring the relative dielectric constant of the dielectric material based on the quasi-optical ellipsoidal mirror is characterized by comprising the following steps:
s1, constructing a quasi-optical ellipsoidal mirror unit, and setting a quasi-optical transmission light path based on the quasi-optical ellipsoidal mirror unit;
s2, performing TRL calibration on the quasi-optical transmission light path;
s3, after calibration, the electric field distribution in the quasi-optical ellipsoidal mirror unit is normal and accords with the beam waist transformation theory, and the step S3 is carried out, otherwise, the step S2 is returned;
s4, under the condition of acquiring cavity S 21 Curve and phase theta 1 ；
S5, arranging a rotatable medium material at the beam waist position of the quasi-optical ellipsoidal mirror to enable the quasi-optical transmission light path to penetrate through the medium material, and acquiring S under the loading condition 21 Curve and phase theta 2 ；
S6, calculating phase theta 1 Phase θ 2 The phase difference delta theta at the same frequency point;
s7, based on the phase theta 1 Phase θ 2 And inverting the phase difference delta theta to obtain the relative dielectric constant.
2. The method for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoidal mirror according to claim 1, further comprising the steps of:
and S8, changing the frequency of the Gaussian beam input into the quasi-optical ellipsoidal mirror unit, returning to the step S4, inverting the relative dielectric constant again, comparing the consistency of the relative dielectric constants obtained in the step S7 and the step S8, ending the measurement and outputting a measurement result when the difference is smaller than a preset threshold, and otherwise returning to the step S5.
3. The method for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoidal mirror according to claim 1, wherein in step S1, the process of constructing a quasi-optical transmission path includes the following steps:
s9, constructing the quasi-light transmission light path by using at least a vector network analyzer, a Gaussian beam radiation horn, a Gaussian beam receiving horn and a quasi-light ellipsoidal mirror, 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 loudspeaker is used as a feed source, the output end of the Gaussian beam radiation loudspeaker sends Gaussian beams, and the Gaussian beams are reflected to the Gaussian beam receiving loudspeaker after secondary focusing in a quasi-optical ellipsoidal mirror.
4. The method for measuring dielectric constant of dielectric material based on quasi-optical ellipsoidal mirror according to claim 3, wherein in step S9, the Gaussian beam radiation horn is a shaped horn, the shaped curve of the shaped horn is a connection combination of at least three curves, and sin is selected from the input port to the output port of the horn p The curve, the second section selects polynomial form, the third section selects hyperbolic form, the function expression of the shaping curve is:
wherein r is i To shape the radius of the input port face of the horn, r o The radius of the output port surface of the shaping horn is set; r is (r) a The radius of the shaped horn at the cut-off of the first section of curve is set; r is (r) b The radius of the shaped horn at the cut-off position of the second section of curve is given; l is the total length of the shaped horn; A. p is p 1 、p 2 Is a control parameter; in the direction from the input port to the output port of the shaping horn, the length of the first section of curve is denoted as a, the length of the second section of curve is denoted as (b-a), and the length of the third section of curve is denoted as (L-b);
the beam waist radius of the Gaussian beam radiation horn is set to be larger than the working wavelength of the Gaussian beam radiation horn.
5. The method of measuring dielectric constant of dielectric material based on quasi-optical ellipsoidal mirror according to claim 3, wherein in step S9, the quasi-optical transmission path is of symmetrical structure, and the beam waist radius of Gaussian beam incident on the quasi-optical ellipsoidal mirror is set to be w 1 An incident distance d in Determining the radius w of the emergent beam waist according to the size of the test beam waist and the test distance required by the quasi-optical transmission light path 2 And exit distance d out The method comprises the steps of carrying out a first treatment on the surface of the Radius of curvature R of the equiphase surface of the incident beam in Radius of curvature R of equiphase surface of outgoing beam out The method comprises the following steps of:
wherein λ is the wavelength;
radius of curvature R of equiphase surface of incident beam in Radius of curvature R of equiphase surface of outgoing beam out Distance R from any point on quasi-optical ellipsoidal mirror to two focuses 1 、R 2 The following relationship exists:
R 1 ＝R in
R 2 ＝R out
r according to quasi-optical ellipsoidal mirror 1 、R 2 The geometric relation of the (2) is used for obtaining the major axis, the minor axis and the focal length value of the (b) so as to obtain the structural parameters of the quasi-optical ellipsoidal mirror.
6. A system for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoidal mirror, based on a method for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoidal mirror according to any one of claims 1 to 5, wherein the system at least comprises:
a quasi-optical ellipsoidal mirror;
the Gaussian beam radiation horn and the Gaussian beam receiving horn are respectively and correspondingly arranged above the two quasi-optical ellipsoidal mirrors according to preset positions, so that Gaussian beams are emitted through the Gaussian beam radiation horn, secondarily focused through the quasi-optical ellipsoidal mirrors and reach the Gaussian beam receiving horn;
the medium material is arranged between the two focuses of the quasi-optical ellipsoidal mirror and is positioned at the beam waist position of the quasi-optical ellipsoidal mirror, so that the Gaussian beam passes through the medium material;
the signal output end and the signal input end of the vector network analyzer are respectively connected with a Gaussian beam radiation loudspeaker and a Gaussian beam receiving loudspeaker in a corresponding way;
and the computer is connected with the vector network analyzer.
7. The system for measuring the relative permittivity of a dielectric material based on a quasi-optical ellipsoidal mirror of claim 6 further comprising an angle adjustment structure for mounting said dielectric material and adjusting the angle of the dielectric material.
8. The system for measuring the relative dielectric constant of a dielectric material based on a quasi-optical ellipsoidal mirror according to claim 7, wherein the thickness of the dielectric material is smaller than half wavelength corresponding to the center frequency of the frequency band applied by the relative dielectric constant measuring system, and the dielectric material has a thin cylindrical shape.
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