阅读说明：本技术 一种测量微米粉末复介电常数的方法 (Method for measuring composite dielectric constant of micron powder ) 是由 吕清 赵佳 付超 赵华 武现聪 王瑾 于 2021-07-29 设计创作，主要内容包括：本发明公开了一种测量微米粉末复介电常数的方法,步骤包括：S1.将测量装置与矢量网络分析仪连接,通过所述矢量网络分析仪产生的微波扫频信号获取S参数；S2.提取出传播常数；S3.对所述传常数进行匹配,然后提取复介电常数。本发明提出了一种测量微米粉末复介电常数的方法,引入了长度不同的两个微带线测量单元,利用数学方法将相差部分的传播常数提取出来,这种方法避免了目前其他微带结构的电介质表征方法的测量单元不连续性,可以实现微波宽频带下测量微米粉末材料的介电常数,该方法还适用于测量微波宽频带下非金属固体材料的介电常数,测量装置简单便携。(The invention discloses a method for measuring the complex dielectric constant of micron powder, which comprises the following steps: s1, connecting a measuring device with a vector network analyzer, and acquiring an S parameter through a microwave frequency sweeping signal generated by the vector network analyzer; s2, extracting a propagation constant; and S3, matching the transmission constants, and then extracting the complex dielectric constant. The invention provides a method for measuring the complex dielectric constant of micron powder, which introduces two microstrip line measuring units with different lengths, extracts the propagation constant of a phase difference part by using a mathematical method, avoids the discontinuity of the measuring units of the dielectric characterization methods of other existing microstrip structures, can realize the measurement of the dielectric constant of the micron powder material under a microwave broadband, is also suitable for measuring the dielectric constant of a nonmetal solid material under the microwave broadband, and has a simple and portable measuring device.)

1. A method for measuring the composite dielectric constant of micron powder, which is characterized by comprising the following steps:

s1, connecting a measuring device with a vector network analyzer, and acquiring an S parameter through a microwave frequency sweeping signal generated by the vector network analyzer;

s2, extracting a propagation constant;

and S3, matching the propagation constants, and then extracting the complex dielectric constant.

2. A method for measuring the complex dielectric constant of micropowders as defined in claim 1, wherein: the propagation constant is: γ ═ α + j β, the Bianco-Parodi method is used, i.e. based on the measurement of the parameters S of two microstrip lines having the same topology, and the two microstrip lines differ only by Δ L in length.

3. A method for measuring the complex dielectric constant of micropowders as defined in claim 1, wherein: the process of extracting the propagation constant in S2 specifically includes:

a. define the microstrip line L_1、Microstrip line L₂Said L is₁Less than L₂The microstrip line is connected with a microwave connector of the vector network analyzer;

b. let S_ij,1And S_ij,2The scattering matrixes are two SMA connector-microstrip arrays; s_ij,1And S_ij,2At the end P₁And P2; the characteristic impedance of the microstrip line is 50 omega, and the connection modes of the SMA connector and the microstrip line are the same;

c. measuring S using mode propagating in microstrip_ij,1And S_ij,2And (3) calculating the propagation constant of the phase difference part delta L of the two microstrip lines, namely L2-L2, wherein the formula is as follows:

4. a method for measuring the complex dielectric constant of micropowders according to claim 2, wherein: the method for extracting the complex dielectric constant in the S3 comprises the following steps:

the first is that: matching the complex dielectric constant by a training method;

secondly, the following steps: and analyzing microstrip line propagation parameters by using a spectral domain method SDA to obtain the complex dielectric constant.

5. The method for measuring the complex dielectric constant of micron powder as set forth in claim 4, wherein: the method comprises the following steps: extracting a propagation constant gamma according to the difference delta L of the lengths of the two microstrip lines^*Said propagation constant γ^*As input to electromagnetic simulation software, for the propagation constant γ^*Optimizing, setting a target value of the propagation constant, and optimizing the propagation constant gamma^*Training is carried out until a value matched with the target value of the propagation constant is obtained, and the complex dielectric constant is extracted.

6. The method for measuring the complex dielectric constant of micron powder as set forth in claim 5, wherein: the second method comprises the following steps: and establishing a mathematical model by using a continuity equation between different layers in the space Fourier transform alpha m, y and z, and automatically matching to obtain the complex dielectric constant of the detected material correspondingly matched with each frequency point after the continuity condition between different regions is brought in and the continuity condition between different regions is brought in.

Technical Field

The invention relates to the field of microwave measurement, in particular to a method for measuring a composite dielectric constant of micron powder.

Background

In recent years, there have been many methods for extracting complex dielectric constants from measurements of various material parameters. In the microwave and millimeter wave bands, the most commonly used measurement techniques for solid materials are basically non-resonance (reflection and reflection/transmission) and resonance (resonance and disturbance), free space, parallel electrode, and dome. In China, many organizations have started to measure and research parameters such as the complex dielectric constant of materials, for example, Beijing radio metrology research institute measures the complex dielectric constant of a large-loss solid material within the range of 2-40GHz according to SJ 20512-1995 'microwave large-loss solid material complex dielectric constant and complex permeability test method', and measures the complex dielectric constant of a millimeter-wave band dielectric material according to GB/T9534-1988 'millimeter-wave band solid dielectric material dielectric characteristic test method quasi-optical cavity method'. The zero point indication method and the resonant cavity method in ASTM D150-2011 of Wickie detection technology Limited and the like measure the relative complex dielectric constant and the dielectric loss tangent of liquid, fusible material and solid material, but the measuring range is only 15Hz-300 MHz. The methods have some common defects, such as only being suitable for solid dielectric materials, being suitable for low-loss dielectric materials below 1GHz, narrow measuring frequency band, and high complexity of a test system and a material clamp. For micron-sized powder materials, no effective measurement means is available at present, and because of the particularity of the powder materials, a reflection/transmission method, namely a TEM transmission line, is selected as the test method. The main reasons are the ease of handling and the operation of measuring as wide a band as possible for the powdered material.

Disclosure of Invention

The invention aims to provide a method for measuring the composite dielectric constant of micron powder, which solves the problems in the prior art and has the advantages of wide application range, simple and convenient measuring device and easy control.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a method for measuring the composite dielectric constant of micron powder, which is characterized by comprising the following steps of:

s1, connecting a measuring device with a vector network analyzer, and acquiring an S parameter through a microwave frequency sweeping signal generated by the vector network analyzer;

s2, extracting a propagation constant;

and S3, matching the propagation constants, and then extracting the complex dielectric constant.

Preferably, the propagation constant: γ ═ α + j β, the Bianco-Parodi method is used, i.e. based on the measurement of the parameters S of two microstrip lines having the same topology, and the two microstrip lines differ only by Δ L in length.

Preferably, the process of extracting the propagation constant in S2 specifically includes:

a. define the microstrip line L_1、Microstrip line L₂Said L is₁Less than L₂The microstrip line is connected with a microwave connector of the vector network analyzer;

b. let S_ij,1And S_ij,2The scattering matrixes are two SMA connector-microstrip arrays; s_ij,1And S_ij,2At the end P₁And P2; the characteristic impedance of the microstrip line is 50 omega, and the connection modes of the SMA connector and the microstrip line are the same;

c. measuring S using mode propagating in microstrip_ij,1And S_ij,2And (3) calculating the propagation constant of the phase difference part delta L of the two microstrip lines, namely L2-L2, wherein the formula is as follows:

preferably, the method for extracting the complex dielectric constant in S3 includes:

the first is that: matching the complex dielectric constant by a training method;

secondly, the following steps: and analyzing microstrip line propagation parameters by using a spectral domain method SDA to obtain the complex dielectric constant.

Preferably, the first method: extracting a propagation constant gamma according to the difference delta L of the lengths of the two microstrip lines^*Said propagation constant γ^*As input to electromagnetic simulation software, for the propagation constant γ^*Optimizing, setting target value of propagation constant, and optimizingSaid propagation constant γ of^*Training is carried out until a value matched with the target value of the propagation constant is obtained, and the complex dielectric constant is extracted.

Preferably, method two: and establishing a mathematical model by using a continuity equation between different layers in the space Fourier transform alpha m, y and z, and automatically matching to obtain the complex dielectric constant of the detected material correspondingly matched with each frequency point after the continuity condition between different regions is brought in and the continuity condition between different regions is brought in.

The invention discloses the following technical effects:

the invention provides a method for measuring the complex dielectric constant of micron powder, which introduces two microstrip line measuring units with different lengths, extracts the propagation constant of a phase difference part by using a mathematical method, avoids the discontinuity of the measuring units of the dielectric characterization methods of other existing microstrip structures, and can realize the measurement of the dielectric constant of the micron powder material under a microwave broadband band (50MHz-18 GHz).

The method is suitable for powder materials with different properties such as non-metal powder, metal oxide powder and the like, such as silicon carbide powder, aluminum oxide powder, aluminum powder and mixed powder of different materials.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

FIG. 1 is a schematic diagram of a process for measuring complex dielectric constant according to the present invention;

fig. 2 is a schematic diagram of microstrip lines L1 and L2 and microstrip line difference Δ L according to the present invention;

FIG. 3 is a schematic view of a sample holder apparatus according to the present invention;

FIG. 4 is a schematic diagram of a 2D section model for mathematical modeling according to the present invention.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The specification and examples are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

The "parts" in the present invention are all parts by mass unless otherwise specified.

The invention provides a method for measuring the complex dielectric constant of micron powder, which comprises the following steps,

s1, connecting a measuring device with a vector network analyzer, and acquiring an S parameter through a microwave frequency sweeping signal generated by the vector network analyzer; s2, extracting a propagation constant; and S3, matching the propagation constants, and then extracting the complex dielectric constant, as shown in figure 1. The method avoids discontinuity of measurement units of other dielectric medium characterization methods of the existing microstrip structure, can realize measurement of dielectric constant of micron powder materials under microwave broadband (50MHz-18GHz), is suitable for powder materials with different properties such as non-metal powder, metal powder and metal oxide powder, such as silicon carbide powder, aluminum oxide powder, aluminum powder and mixed powder of different materials, and has simple and portable measurement device.

1. Extracting a propagation constant gamma through a measurement result of the S parameter; propagation constants were derived by measuring the S-parameter: γ ═ α + j β, the Bianco-Parodi method is used, i.e. based on the measurement of the parameters S of two microstrip lines having the same topology, and the two microstrip lines differ only by Δ L in length. The method for extracting the propagation constant gamma needs two uniform microstrip lines L with different lengths₁And L₂(L₁<L₂) And two identical microwave connectors (SMA) L for connection to a vector network analyzer_A、L_BAs shown in fig. 2. Let S_ij,1And S_ij,2A scattering matrix which is two 'connector-microstrip'; s_ij,1And S_ij,2At the end P₁And P2; the characteristic impedance of the microstrip line is 50 omega, and the connection mode of the SMA connector and the microstrip line is the same. According to the formula derivation, the high-order mode generated near the connector and the microstrip line is negligible, and the mode propagated in the microstrip is a quasi-TEM mode. S measured by two microstrip lines_ij,1And S_ij,2Parameters, it can be derived that the propagation constants at the two microstrip line phase difference portions Δ L-L2-L2 conform to the following formula:

2. extraction of complex dielectric constant epsilon from transmission constant matching process_rA first step of; assuming that the dielectric constant of the material to be measured (especially the powder material) is to be laid on the sample holder devices respectively on the microstrip lines with the same characteristic impedance and the lengths of L1 and L2, the propagation constant gamma on the microstrip line at the position of delta L covered by the powder material can be extracted. Through simulation and experiments, it has been verified that the wave propagation of the sample holder device in the discontinuous part of the measuring structure, such as l section, can be ignored, and the propagation constant is not related to the SMA joint parameters. Therefore, the robustness of the method of extracting the propagation constant γ on the microstrip line at the powder material Δ L is very good, as shown in fig. 3.

3. The complex dielectric constant ε of the powder material covering the Δ L segment needs to be extracted next by the propagation constant_r*. There are two methods available to extract complex dielectric constants: firstly, the method comprises the following steps of; a propagation constant gamma extracted by a phase difference part delta L of two microstrip lines^*The method is input into electromagnetic simulation software, a propagation constant target value is set by utilizing the optimization function of the electromagnetic simulation software, and the complex dielectric constant matched with the test material is searched iteratively. And secondly, analyzing microstrip line propagation parameters by using a spectral domain method (SDA) to extract complex dielectric constants. The SDA-based numerical simulation can represent the electromagnetic field continuity condition in a direct space transformation domain which utilizes Fourier series decomposition of the electromagnetic field along the axial direction parallel to the interface of the metal conductor, so that when the interface has non-uniformity, the method can also describe the continuity condition of the interface by a mathematical model. After determining the propagation constant γ of Δ L covered by the measured material, in order to extract the dielectric constant of the material covered on the line segment with the length of Δ L, electromagnetic simulation software, such as HFSS, CST Microwave Studio and other software, may be used, the propagation constant is input into the electromagnetic simulation software by the software, the dielectric constant is extracted by the software optimization matching function, the method requires inputting γ value on each single frequency point to search for the dielectric constant of the matched material, one frequency point calculation requires about half an hour. In fact, we only need to calculate the propagation characteristics of the structure (microstrip line) which is not changed along the propagation axis, so the calculation structure can be limited in the two-dimensional modeling of the structure cross section. Thus. We can use a mathematical computation model based on the spectral domain method (SDA). In this method, it is necessary to model the continuity equation between different layers in the spatial fourier transform (α m, y, z) to form a mathematical model, i.e. to describe a two-dimensional model of the spectral domain of different regions in fig. 3 by using the spatial electromagnetic field, and then to bring the continuity condition between different regions into the mathematical model, so that the calculation time of each frequency point can be reduced to several seconds by using this method. Taking into account all continuity conditions of the different interfaces and the expressions of the E-field and the H-field, the following matrix equation is obtained:

therefore, the real part and the imaginary part of the dielectric constant of the measured material can be used as variable parameters by the method on the basis of the known parameters. Thus, the dielectric constant of the material to be measured corresponding to each frequency point is obtained through automatic matching, as shown in fig. 4.

(1) Micro-strip line processing dimension

The lengths of the two microstrip lines are respectively 101.5mm and 76mm in L1 and 76mm in L2, the substrate is made of an RT Duroid5880 substrate (epsilon r' is 2.2 and tan delta is 0.0009), the thickness is 508 mu m, the central conductor is made of copper, the thickness is 17.5 mu m, and the width is 1.54 mm.

And 4 mounting holes are uniformly drilled on the microstrip line according to the measuring frame so as to mount the sample rack and connect the SMA joint with the microstrip line in a welding manner.

(2) Measuring frame for solid or powder material to be measured

Measurement sample holder (50 x 30 x 20 mm)³) Made of plexiglass (wall thickness 5 mm). This size is a reasonable size that has no effect on the measurement results after testing.

(3) Before measurement, Thru, Load and reflex of the vector network analyzer are calibrated, the temperature and humidity of a test environment are guaranteed, the measuring device is connected to the vector network analyzer, S parameters of the assembled testing device and a proper amount of network analyzer are measured by using a microwave frequency sweeping signal generated by the vector network analyzer, the measured S parameters are input into a computer, and the complex dielectric constant of the measured material is calculated by using the method.

The method has tested the complex dielectric constants of the following solid and powder materials over a wide frequency band (0.5-18 GHz):

solid material: complex dielectric constant of organic glass (thickness 15 mm);

micron-sized powder material (Norton type F100 HD): SiC, Al2O3 and Al, grain size of about 100 μm, and complex nodal constants of micron powder materials mixed in different proportions.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.