CN103149449A - Single-port coaxial line complex permittivity measuring device and method based on mode matching - Google Patents
Single-port coaxial line complex permittivity measuring device and method based on mode matching Download PDFInfo
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- CN103149449A CN103149449A CN2013100398476A CN201310039847A CN103149449A CN 103149449 A CN103149449 A CN 103149449A CN 2013100398476 A CN2013100398476 A CN 2013100398476A CN 201310039847 A CN201310039847 A CN 201310039847A CN 103149449 A CN103149449 A CN 103149449A
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Abstract
The invention provides a single-port coaxial line complex permittivity measuring device and a method based on mode matching. The single-port coaxial line complex permittivity measuring device comprises a coaxial line cable connector, a coaxial waveguide section and a terminal short circuit metal plate, wherein the coaxial line cable connector, the coaxial waveguide section and the terminal short circuit metal plate are connected in sequence, the lateral dimension of the coaxial waveguide section is not dependent on the size of the coaxial line cable connector, and the coaxial waveguide section works in a multimode state. The measuring method relates to the measuring device and a vector network analyzer. A reflection coefficient of a sensing device which is filled in substance to be measured is measured through the vector network analyzer and then through data processing, a complex permittivity of the substance is achieved through inversion. Due to the fact that a multimode matching model is used in the inversion process, the coaxial waveguide section can works in the multimode state, so that the design and processing demands of measuring and sensing devices are lowered and an upper limit of working frequency is improved.
Description
Technical field
The present invention relates to a kind of single port coaxial line type complex dielectric constant measuring apparatus and method based on the mould coupling.
Background technology
The complex permittivity of measurement of species is significant in scientific research and commercial production, especially in the frequency microwave frequency range.Along with developing rapidly of electronic technology, the survey frequency scope of vector network analyzer is increasing, precision is more and more higher, complex permittivity frequency domain measuring method based on vector network analyzer is widely studied, wherein a kind of wide-band width measurement method commonly used is coaxial axis method, the method has been filled the reflection-transmission coefficient of the coaxial waveguide of sample by measurement, according to the mathematical relation between the complex permittivity of reflection-transmission coefficient and sample, be finally inversed by the complex permittivity under different frequency.Traditional coaxial axis method requires to fill in the coaxial waveguide of sample and only has the TEM ripple, and mathematical model is fairly simple like this, but when practical application, need to carry out particular design to the coaxial cable junction of different size, does not have higher mode to be energized out with assurance.
Summary of the invention
The invention provides a kind of coaxial waveguide of terminal short circuit of utilizing and the material complex permittivity is carried out the method for wide-band width measurement.
A kind of single port coaxial line type complex dielectric constant measuring apparatus based on the mould coupling comprises the coaxial fitting, coaxial waveguide section and the terminal short circuit sheet metal that are connected successively; The lateral dimension of coaxial waveguide section does not rely on the size of coaxial fitting; The coaxial waveguide section works in the multimode state.
Described coaxial fitting is SMA or N-type head.
A kind of single port coaxial line type method for measuring complex dielectric constant based on the mould coupling of described device, step is as follows:
1) calibration vector network analyzer is elected alignment surface as the z=-L face, calibrates;
2) measure the reflection coefficient of empty measurement mechanism, obtain equivalent electric length from the z=-L face to the z=0 face and the length d of coaxial waveguide section;
3) measure the reflection coefficient of the measurement mechanism of having filled sample;
4) according to step 2), 3) measurement data carry out Inversion Calculation, obtain the complex permittivity of sample under different frequency:
Three kinds of patterns of TEM, TM and TE are arranged in coaxial waveguide, and the higher mode of excitation only has TM
0mMould, the TM in coaxial waveguide
0mThe modular function of mould is Z (ζ
amρ)=J
1(ζ
amρ)+G
amN
1(ζ
amρ), wherein ρ is radial coordinate, J
1And N
1Respectively the first kind and the Equations of The Second Kind Bessel function of single order, G
amScale-up factor, ζ
amTM
0mThe horizontal transmission function of mould, the left and right sides, surface of discontinuity place represent with subscript a and b respectively, and direct problem model mode expansion is:
Wherein A represents the incident wave amplitude of each pattern, is unknown quantity, and Y represents the mode admittance of each pattern:
Represent that each pattern is at the ratio of surface of discontinuity place's reflection wave and incident wave:
Wherein ω is the angular frequency of measuring, ε
a, ε
bRespectively the specific inductive capacity of the filling material of coaxial fitting and coaxial waveguide section, k
zamAnd k
zbnIt is the longitudinal propagation constant of each pattern:
Have according to surface of discontinuity place boundary condition:
E
aρ=0,R
1≤ρ≤R
4
E
bρ=0,R
2≤ρ≤R
3
Wherein, R
1, R
2Respectively the radius of the internal and external conductor of standard coaxial joint, R
4, R
3It is respectively the radius of the internal and external conductor of coaxial waveguide section;
Utilize the orthogonality of Bessel function, can solve Г with numerical method
a0/ A
a0, i.e. the reflection coefficient of whole measurement mechanism; On the basis of direct problem model, with the inverse problem algorithm, the reflection coefficient of measuring is finally inversed by the complex permittivity of testing sample.
Beneficial effect of the present invention: this method is based on the mould Matching Model in coaxial cable, do not require and only have the TEM ripple in sample, the sampling receptacle of any size can directly connect with concentric cable, and the upper limit of survey frequency also significantly improves because being not limited to the TEM ripple.Owing to having used the mould Matching Model in the data inversion process, so have the survey frequency wide ranges, sensing device is simple in structure and the measuring accuracy advantages of higher.
Description of drawings
Accompanying drawing 1 is based on the single port coaxial line type complex dielectric constant measuring apparatus structural representation of mould coupling.
Accompanying drawing 2 is based on the single port coaxial line type method for measuring complex dielectric constant schematic diagram of mould coupling.
Embodiment
Below in conjunction with the drawings and specific embodiments, the present invention is described further.Based on single port coaxial line type complex dielectric constant measuring apparatus structure such as the accompanying drawing 1 of mould coupling, wherein 1 is the standard coaxial cable joint, the 2nd, and as the coaxial waveguide section of sampling receptacle, the 3rd, short circuit sheet metal.The standard coaxial cable joint here can be that SMA or N-type are first-class, the lateral dimension of coaxial waveguide section 2 does not rely on coaxial fitting 1, this application scenario for the large capacity sampling receptacle of needs is very favourable, and the internal and external conductor diameter of coaxial waveguide section 2 can design arbitrarily according to functional need.
The measuring method schematic diagram as shown in Figure 2, wherein 4 is vector network analyzers, the 5th, measure concentric cable, the 6th, measure sensing device.
Measuring process is as follows:
1. calibration vector network analyzer: elect alignment surface as the z=-L face, calibrate vowing net.
2. measure the reflection coefficient of empty sensing device (being that filling material is air), to obtain equivalent electric length from the z=-L face to the z=0 face and the length d of coaxial waveguide section 2.
3. measure the reflection coefficient of the sensing device of having filled sample.
4. above measurement data is carried out Inversion Calculation, obtain the complex permittivity of sample under different frequency.
The below provides data inversion method.Because this problem is the inverse problem of a standard, so at first need to set up the direct problem model, used is the mould Matching Model here.So-called mould coupling refers to, if the somewhere physical dimension is undergone mutation in waveguide, each pattern size of the field of surface of discontinuity both sides can be determined at the boundary condition of surface of discontinuity according to electromagnetic field so.
Three kinds of patterns of TEM, TM and TE are arranged in coaxial waveguide, and in coaxial configuration as shown in Figure 1, because the incident wave of coming from concentric cable only has the TEM ripple, and surface of discontinuity has axial symmetry, so the higher mode of excitation only has TM
0mMould, the TM in coaxial waveguide
0mThe modular function of mould is Z (ζ
amρ)=J
1(ζ
amρ)+G
amN
1(ζ
amρ), wherein ρ is radial coordinate, J
1And N
1Respectively the first kind and the Equations of The Second Kind Bessel function of single order, G
amScale-up factor, ζ
amTM
0mThe horizontal transmission function of mould.Like this electromagnetic field of the left and right sides, surface of discontinuity place (representing take subscript a and b respectively) can with mode expansion as:
Wherein A represents the incident wave amplitude of each pattern, is unknown quantity, and Y represents the mode admittance of each pattern:
Represent that each pattern is at the ratio of surface of discontinuity place's reflection wave and incident wave:
Wherein ω is the angular frequency of measuring, ε
a, ε
bRespectively the specific inductive capacity of the filling material of coaxial fitting and coaxial waveguide section, k
zamAnd k
zbnIt is the longitudinal propagation constant of each pattern:
Have according to surface of discontinuity place boundary condition:
E
aρ=0,R
1≤ρ≤R
4
E
bρ=0,R
2≤ρ≤R
3
Wherein, R
1, R
2Respectively the radius of the internal and external conductor of standard coaxial joint, R
4, R
3It is respectively the radius of the internal and external conductor of coaxial waveguide section.
Above-mentioned formula has been described the total electromagnetic field that is combined to form of infinite a plurality of patterns, and the amplitude of each pattern reduces along with the increase of pattern exponent number, when carrying out numerical evaluation, as long as limited enough pattern of intercepting.Utilize the orthogonality of Bessel function, can solve with numerical method
Be the reflection coefficient of whole sensing device, this is the solution procedure of direct problem.
On the basis of direct problem model, can the reflection coefficient of measuring be finally inversed by with simple inverse problem algorithm (as Newton iteration method) complex permittivity of sample.
Claims (3)
1. the single port coaxial line type complex dielectric constant measuring apparatus based on the mould coupling, is characterized in that, it comprises coaxial fitting (1), coaxial waveguide section (2) and the terminal short circuit sheet metal (3) that is connected successively; The lateral dimension of coaxial waveguide section (2) does not rely on the size of coaxial fitting (1); Coaxial waveguide section (2) works in the multimode state.
2. device according to claim 1, is characterized in that, described coaxial fitting (1) is SMA or N-type head.
3. the single port coaxial line type method for measuring complex dielectric constant based on the mould coupling that installs according to claim 1, is characterized in that, step is as follows:
1) calibration vector network analyzer (4), elect alignment surface as the z=-L face, calibrates;
2) measure the reflection coefficient of empty measurement mechanism, obtain equivalent electric length from the z=-L face to the z=0 face and the length d of coaxial waveguide section (2);
3) measure the reflection coefficient of the measurement mechanism of having filled sample;
4) according to step 2), 3) measurement data carry out Inversion Calculation, obtain the complex permittivity of sample under different frequency: three kinds of patterns of TEM, TM and TE are arranged in coaxial waveguide, and the higher mode of excitation only has TM
0mMould, the TM in coaxial waveguide
0mThe modular function of mould is Z (ζ
amρ)=J
1(ζ
amρ)+G
amN
1(ζ
amρ), wherein ρ is radial coordinate, J
1And N
1Respectively the first kind and the Equations of The Second Kind Bessel function of single order, G
amScale-up factor, ζ
amTM
0mThe horizontal transmission function of mould, the left and right sides, surface of discontinuity place represent with subscript a and b respectively, and direct problem model mode expansion is:
Wherein A represents the incident wave amplitude of each pattern, is unknown quantity, and Y represents the mode admittance of each pattern:
Represent that each pattern is at the ratio of surface of discontinuity place's reflection wave and incident wave:
Wherein ω is the angular frequency of measuring, ε
a, ε
bRespectively the specific inductive capacity of the filling material of coaxial fitting (1) and coaxial waveguide section (2), k
zamAnd k
zbnIt is the longitudinal propagation constant of each pattern:
Have according to surface of discontinuity place boundary condition:
R
4≤ρ≤R
2
E
aρ=0,R
1≤ρ≤R
4
E
bρ=0,R
2≤ρ≤R
3
Wherein, R
1, R
2Respectively the radius of the internal and external conductor of standard coaxial joint (1), R
4, R
3It is respectively the radius of the internal and external conductor of coaxial waveguide section (2);
Utilize the orthogonality of Bessel function, can solve Г with numerical method
a0/ A
a0, i.e. the reflection coefficient of whole measurement mechanism; On the basis of direct problem model, with the inverse problem algorithm, the reflection coefficient of measuring is finally inversed by the complex permittivity of testing sample.
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Cited By (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN103884919A (en) * | 2014-03-13 | 2014-06-25 | 四川大学 | Medium dielectric coefficient measuring probe with coaxial line structure under high-temperature condition and system |
CN105067895A (en) * | 2015-08-05 | 2015-11-18 | 袁渊 | Compact type band-stop resonant cavity fixture and test piece determination method |
CN105974345A (en) * | 2016-04-27 | 2016-09-28 | 电子科技大学 | High temperature calibration method of free space terminal short circuit method complex dielectric constant test system |
CN106324360A (en) * | 2015-06-19 | 2017-01-11 | 深圳光启高等理工研究院 | Dielectric parameter measurement system and method |
CN109001540A (en) * | 2018-07-18 | 2018-12-14 | Oppo广东移动通信有限公司 | Dielectric constant acquisition methods and relevant apparatus |
CN109782073A (en) * | 2018-12-14 | 2019-05-21 | 华北电力大学(保定) | A kind of twin-core power line unit length parametric solution method |
CN110082606A (en) * | 2019-06-14 | 2019-08-02 | 中国石油大学(华东) | Dielectric constant measurement system and method based on multichannel Open ended coaxial probe |
CN110596463A (en) * | 2019-09-20 | 2019-12-20 | 电子科技大学 | Coaxial measuring device, testing system and method for measuring dielectric constant of medium |
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Cited By (14)
Publication number | Priority date | Publication date | Assignee | Title |
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CN103884919A (en) * | 2014-03-13 | 2014-06-25 | 四川大学 | Medium dielectric coefficient measuring probe with coaxial line structure under high-temperature condition and system |
CN103884919B (en) * | 2014-03-13 | 2017-02-15 | 四川大学 | Medium dielectric coefficient measuring probe with coaxial line structure under high-temperature condition and system |
CN106324360B (en) * | 2015-06-19 | 2023-10-31 | 深圳光启高等理工研究院 | Measurement system and measurement method for dielectric parameters |
CN106324360A (en) * | 2015-06-19 | 2017-01-11 | 深圳光启高等理工研究院 | Dielectric parameter measurement system and method |
CN105067895A (en) * | 2015-08-05 | 2015-11-18 | 袁渊 | Compact type band-stop resonant cavity fixture and test piece determination method |
CN105067895B (en) * | 2015-08-05 | 2018-07-20 | 深圳鼎缘电子科技有限公司 | Compact band hinders resonant cavity fixture and test specimen assay method |
CN105974345B (en) * | 2016-04-27 | 2018-09-18 | 电子科技大学 | Free space terminal short circuit complex dielectric permittivity tests system high temperature calibration method |
CN105974345A (en) * | 2016-04-27 | 2016-09-28 | 电子科技大学 | High temperature calibration method of free space terminal short circuit method complex dielectric constant test system |
CN109001540A (en) * | 2018-07-18 | 2018-12-14 | Oppo广东移动通信有限公司 | Dielectric constant acquisition methods and relevant apparatus |
CN109001540B (en) * | 2018-07-18 | 2021-04-13 | Oppo广东移动通信有限公司 | Dielectric constant acquisition method and related device |
CN109782073A (en) * | 2018-12-14 | 2019-05-21 | 华北电力大学(保定) | A kind of twin-core power line unit length parametric solution method |
CN109782073B (en) * | 2018-12-14 | 2021-03-02 | 华北电力大学(保定) | Method for solving unit length parameter of dual-core power line |
CN110082606A (en) * | 2019-06-14 | 2019-08-02 | 中国石油大学(华东) | Dielectric constant measurement system and method based on multichannel Open ended coaxial probe |
CN110596463A (en) * | 2019-09-20 | 2019-12-20 | 电子科技大学 | Coaxial measuring device, testing system and method for measuring dielectric constant of medium |
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