CN106199287A - A kind of material electric field shielding effect test system and method based on rectangular waveguide - Google Patents

Abstract

The present invention relates to electromangnetic spectrum field, particularly relate to a kind of material electric field shielding effect test method and system based on rectangular waveguide.Device used in native system has rectangular waveguide, Network Analyzer, coaxial TEM mode rectangle TE₁₀Mode converter and radio frequency coaxial-cable；During test, detected materials is placed horizontally in gap in the middle of rectangular waveguide, and compresses detected materials with two open ends；The S before and after placement detected materials is measured by Network Analyzer₂₁Parameter, utilizes formula be calculated material electric field shielding usefulness and estimate the electrical conductivity of detected materials.The method can be used to test electric field shielding usefulness during anisotropic material difference E field polarization direction, makes up the deficiency of flange coaxial method.

Description

A kind of material electric field shielding effect test system and method based on rectangular waveguide

Technical field

The invention belongs to electromangnetic spectrum field, particularly relate to a kind of material electric field shielding usefulness based on rectangular waveguide Test system and method.

Background technology

Electromagnetic shielding is the technical measures suppressing the electromagnetic disturbance by spatial field coupling path.Traditionally, electromagnetism Shield the encirclement harassing and wrecking source of the shield shell by making with metal material or sensitive objects is implemented.Metal has fabulous conduction Property, it is sufficiently high to shielding electromagnetic waves usefulness.Therefore, the analysis of metal shield shield effectiveness focus on perforate and seam Impact.In recent years, along with material science and the development of technology, the conductive material of increasing nonmetal template is at electromagnetic screen It is applied in covering, such as metal foam, carbon fiber, conductive rubber, periodic structure, Compact frequency selective surface etc..These are unconventional Shielding material has that density is low, flexible or the feature such as frequency selectivity is good, has significant application value under special occasions.

Shield effectiveness is the key index of material electromagnetic shielding application.Due to structure or the complexity of composition, unconventional screen The effective electromagnetic parameter covering material is difficult to obtain.In wide frequency ranges, particularly obtain material electromagnetic parameter not a duck soup.? In the case of electromagnetic parameter disappearance, analysis of material electromagnet shield effect is typically extremely difficult theoretically.Therefore, experiment is surveyed Examination is the indispensable means of assessment material electromagnet shield effect.

At present, flange coaxial method is to investigate the common method of material far field (plane wave) shield effectiveness.Flange coaxial method base In the similarity of TEM mode Yu plane wave, the plane wave shield effectiveness of simulation test material.By along on-axis wave when being embodied as Lead cross section and load tabular detected materials, and characterize shield effectiveness with the insertion loss of Network Analyzer acquisition material.Flange The advantage of coaxial method is not affected by surrounding scene, and measuring stability is good, and can pass through shield effectiveness inverting in theory The effective electromagnetic parameter (according to the analytic formula of plane wave shield effectiveness) of material.But there are the following problems for the method, flange is same The polarised direction of the electric field intensity of the TEM mode that axle excites is axisymmetric, therefore when anisotropic material is tested, Coaxial waveguide TEM mode embody be various polarised directions lower plane ripple shield effectiveness " average effect ", it is impossible to test each to Shield effectiveness under unlike material difference E field polarization direction.

Summary of the invention

For the problems referred to above, the present invention propose a kind of material electric field shielding effect test system based on rectangular waveguide and Method.

A kind of material electric field shielding effect test system based on rectangular waveguide,

Described system includes: rectangular waveguide, Network Analyzer, coaxial TEM mode rectangle TE₁₀Mode converter and radio frequency Coaxial cable；

Described rectangular waveguide is the cylindrical shell that cross section is rectangle using metallic plate to make, from described cylindrical shell Intermediate lateral disconnects, and is used for placing detected materials；

Described coaxial TEM mode rectangle TE₁₀Mode converter has two, the respectively first coaxial TEM mode rectangle TE₁₀Mode converter and the second coaxial TEM mode rectangle TE₁₀Mode converter, described first coaxial TEM mode rectangle TE₁₀First end of mode converter is connected with the first end of described rectangular waveguide, described second coaxial TEM mode rectangle TE₁₀ First end of mode converter is connected with the second end of described rectangular waveguide；

Described radio frequency coaxial-cable has two sections, the respectively first radio frequency coaxial-cable and the second radio frequency coaxial-cable, described The two ends of the first radio frequency coaxial-cable respectively with described first coaxial TEM mode rectangle TE₁₀Second end of mode converter and The input port of described Network Analyzer connects, the two ends of described second radio frequency coaxial-cable respectively with described second TEM coaxial Pattern rectangle TE₁₀Second end of mode converter and the output port of described Network Analyzer connect.

A kind of method of test material electric field shielding usefulness using above-mentioned test system, described method includes following step Rapid:

S1, calculates the TE of described rectangular waveguide₁₀Mode cutoff frequency f_c1TE with described rectangular waveguide₀₁Mode cutoff frequency Rate f_c2, calibrate described Network Analyzer, the test frequency range regulating described Network Analyzer is f_c1～f_c2；

S2, when not placing detected materials in described rectangular waveguide, operates described Network Analyzer, record do not place to be measured Parameter during material

S3, is placed horizontally in described detected materials gap in the middle of described rectangular waveguide, and compresses institute with two open ends State detected materials, again operate described Network Analyzer, record parameter when placing detected materialsDescribed detected materials is wanted Asking and meet σ/ω ε > 1000, wherein: σ is the electrical conductivity of described detected materials, the angular frequency of electromagnetic wave when ω is test, ε is institute State the dielectric constant of detected materials；

S4, calculates the electric field shielding usefulness of described detected materials；

S5, utilizes the described electric field shielding usefulness recorded and the corresponding anti-electrical conductivity pushing away described detected materials of frequency, estimates Calculate the conductivity range of described detected materials.

The computing formula of described electric field shielding usefulness is:

$SE=S_{21}^{\left(1\right)}-S_{21}^{\left(2\right)}+{\mathrm{\Δ}}_{TE}$

Wherein,For not placing S during detected materials₂₁Parameter,For placing S during detected materials₂₁Parameter；Δ_TEFor Corrected parameter, i.e. detected materials is to TE₁₀Pattern insertion loss and the detected materials difference to TEM mode insertion loss, Δ_TEMeter Calculation formula is:

Δ_TE=-10log₁₀(1-(f_c/f)²)

Wherein, f is wave frequency, f_cFor described rectangular waveguide TE₁₀Mode cutoff frequency.

The described conductivity range estimating described detected materials utilizes infinitely great conductive plate to vertical incidence plane wave electricity Magnetic shield operational effectiveness formula:

$SE=20{\log }_{10}|e^{{\mathrm{jk}}_{c}d}\frac{{(Z_0+Z_c)}^2}{4Z_0{Z}_c}\[1-e^{-2{\mathrm{jk}}_{c}d}{\left(\frac{Z_0-Z_c}{Z_0+Z_c}\right)}^2\]|$

Wherein,For plane wave in the natural impedance of free space,For plane wave at conductive plate In natural impedance,For plane wave propagation constant in conductive plate, ε_e=ε_c-j σ/ω is that conductive plate contains The effective dielectric constant of electrical conductivity impact, ε_cFor the dielectric constant of conductive plate, μ_cFor the pcrmeability of conductive plate, σ is the electricity of conductive plate Conductance, the angular frequency of electromagnetic wave when ω is test, d is the thickness of conductive plate, ε₀For permittivity of vacuum, μ₀For permeability of vacuum.

Electric field shielding usefulness during test anisotropic material difference E field polarization direction in aforementioned manners.

The beneficial effects of the present invention is:

Providing a kind of material electric field shielding effect test system and method based on rectangular waveguide, it is simple to operate, institute The shield effectiveness recorded is the far field (plane wave) the electric field shielding usefulness to infinitely great board under test, thus estimates the electricity of detected materials Conductance, can be used to test shield effectiveness during anisotropic material difference E field polarization direction, due to TE in rectangular waveguide₁₀Mould The E field polarization direction of formula is identical, then utilize the TE of rectangular waveguide₁₀Pattern carries out shield effectiveness test, compensate for flange coaxial method Deficiency.

Accompanying drawing explanation

Fig. 1 is material electric field shielding performance testing device figure based on rectangular waveguide.

Fig. 2 is the schematic diagram of the pole form guide of the arbitrary cross section being laterally loaded with conductive plate.

Fig. 3 is that different electrical conductivity lower conducting plate is to rectangular waveguide TE₁₀The insertion loss of pattern is with the variation diagram of wave frequency.

Fig. 4 be anisotropic material placement direction in rectangular waveguide be schematic diagram when 0 ° and 90 °, wherein Fig. 4 (a) Being 0 °, Fig. 4 (b) is 90 °.

Fig. 5 be under different placement direction anisotropic material to rectangular waveguide TE₁₀The insertion loss of pattern is with wave frequency Variation diagram.

Detailed description of the invention

Below in conjunction with the accompanying drawings, embodiment is elaborated.

Embodiment one:

A kind of material electric field shielding effect test system based on rectangular waveguide, this system includes: rectangular waveguide, network divide Analyzer, coaxial TEM mode rectangle TE₁₀Mode converter and radio frequency coaxial-cable；

Rectangular waveguide is the cylindrical shell that cross section is rectangle using metallic plate to make, and states the intermediate lateral of cylindrical shell Disconnect, be used for placing detected materials.

Coaxial TEM mode rectangle TE₁₀Mode converter has two, the respectively first coaxial TEM mode rectangle TE₁₀ Mode converter and the second coaxial TEM mode rectangle TE₁₀Mode converter, the first coaxial TEM mode rectangle TE₁₀Pattern First end of transducer is connected with the first end of rectangular waveguide, the second coaxial TEM mode rectangle TE₁₀The first of mode converter End is connected with the second end of rectangular waveguide.

Radio frequency coaxial-cable has two sections, the respectively first radio frequency coaxial-cable and the second radio frequency coaxial-cable, the first radio frequency The two ends of coaxial cable respectively with the first coaxial TEM mode rectangle TE₁₀Second end of mode converter and Network Analyzer Input port connect, the two ends of the second radio frequency coaxial-cable respectively with the second coaxial TEM mode rectangle TE₁₀Mode converter The output port of the second end and Network Analyzer connects.

Specific in Fig. 1, rectangular waveguide 1 is the cylindrical shell that cross section is rectangle using metallic plate to make, from cylindricality The intermediate lateral of housing disconnects and is used for placing detected materials 5, its two ends and coaxial TEM mode rectangle TE₁₀Mode converter 4 is even Connecing, Network Analyzer 2 is by radio frequency coaxial-cable 3 and coaxial TEM mode rectangle TE₁₀Mode converter 4 connects；Will during test Detected materials 5 is placed horizontally in gap in the middle of rectangular waveguide, and compresses detected materials with two open ends；Pass through Network Analyzer 2 measure the S before and after placement detected materials 5₂₁Parameter, finally gives material electric field shielding usefulness and estimates its electrical conductivity.

Embodiment two:

The method utilizing the system in embodiment one to carry out electric field shielding usefulness measurement, comprises step performed below:

Step 1, measures length and the width of described rectangular waveguide cross section, calculates described rectangular waveguide TE₁₀Mode cutoff frequency f_c1TE with described rectangular waveguide₀₁Mode cutoff frequency f_c2, calibrate described Network Analyzer, regulate described Network Analyzer Test frequency range is f_c1～f_c2, test device is connected by above-mentioned requirements.

Step 2, when not placing detected materials in described rectangular waveguide, operates described Network Analyzer, records parameter

Step 3, when placing detected materials in described rectangular waveguide, again operates described Network Analyzer, records parameter

Described detected materials is required to meet σ/ω ε > 1000, wherein: σ is the electrical conductivity of described detected materials, and ω is test Time electromagnetic wave angular frequency, ε is the dielectric constant of described detected materials, and this condition easily reaches for shielding material.

Step 4, calculates the electric field shielding usefulness of detected materials, the formula of described calculating detected materials electric field shielding usefulness For:

$SE=S_{21}^{\left(1\right)}-S_{21}^{\left(2\right)}+{\mathrm{\Δ}}_{TE}---\left(1\right)$

In formula,For not placing S during detected materials₂₁Parameter,For placing S during detected materials₂₁Parameter, Δ_TE For corrected parameter, i.e. detected materials is to TE₁₀Pattern insertion loss with to TEM mode insertion loss (plane wave shield effectiveness) it Difference.Δ_TEFormula proving process as follows:

As a example by the uniform pole form guide figure of the arbitrary cross section shown in Fig. 2, region 2 is that the thickness loaded in waveguide is The conductive plate of d, its dielectric constant, pcrmeability and electrical conductivity are respectively ε_c, μ_c, and σ.Region 1 and region 3 are vacuum.In scheming O point is that zero sets up general orthogonal curvilinear coordinate system, its three coordinate amounts be respectively (u, v, z).Wherein, u and v is horizontal To coordinate.

This pole form guide is propagated the H of TE pattern along z-axis_zComponent can be expressed as:

$H_z={\mathrm{AT}}^{2}V(u,v)e^{-{\mathrm{jk}}_{z}z}---\left(2\right)$

In formula, A is amplitude, k_zFor propagation constant.

Eigenfunction V describes the cross direction profiles of field, and it and characteristic value T are determined equation and boundary condition (on wave guide wall by general The tangential component of electric field intensity E is zero) determine:

${\▿}_T^{2}V(u,v)+T^{2}V(u,v)=0---\left(3\right)$

$\frac{\∂V(u,v)}{\∂n}{|}_S=0---\left(4\right)$

In formula,For horizontal Laplace operator, n represents the normal unit vector of wave guide wall, and S is wave guide wall border.Formula And (4) simultaneous may determine that a series of V and T being associated, corresponding to a series of TE patterns (3).Characteristic value is actual is exactly pattern Cut-off wave number.Eigenfunction is the most relevant with shape of cross section and size with characteristic value, therefore three regions have identical intrinsic letter Number and characteristic value.Propagation constant k_zCan be given expression to by characteristic value T and wave number k:

$k_z=\sqrt{k^2-T^2}---\left(5\right)$

Wherein,ω is angular frequency, ε and μ is respectively dielectric constant and the pcrmeability of region medium.

The cross stream component of TE pattern can use its H_zRepresentation in components is:

$\begin{array}{c}{E}_u=-\frac{j\mathrm{\ω}\mathrm{\μ}}{h_2}{\mathrm{Ae}}^{-{\mathrm{jk}}_{z}z}\frac{\∂V}{\∂v}\\ E_v=\frac{j\mathrm{\ω}\mathrm{\μ}}{h_1}{\mathrm{Ae}}^{-{\mathrm{jk}}_{z}z}\frac{\∂V}{\∂u}\\ H_u=-\frac{{\mathrm{jk}}_z}{h_1}{\mathrm{Ae}}^{-{\mathrm{jk}}_{z}z}\frac{\∂V}{\∂u}\\ H_v=-\frac{{\mathrm{jk}}_z}{h_2}{\mathrm{Ae}}^{-{\mathrm{jk}}_{z}z}\frac{\∂V}{\∂v}\end{array}---\left(6\right)$

In formula, h₁And h₂It is respectively u and the Lame Coefficient of v coordinate.

When certain TE mould electromagnetic wave is propagated along z-axis from region 1 and incides conductive plate, be reflected with transmission after, region 1 Field distribution is represented by the superposition of incidence wave and echo:

$\begin{array}{c}{H}_{1z}=T^2(A_1^{+}{e}^{-{\mathrm{jk}}_{1z}z}+A_1^{-}{e}^{{\mathrm{jk}}_{1z}z})V(u,v)\\ E_{1u}=-\frac{{\mathrm{j\ω\μ}}_0}{h_2}(A_1^{+}{e}^{-{\mathrm{jk}}_{1z}z}+A_1^{-}{e}^{{\mathrm{jk}}_{1z}z})\frac{\∂V}{\∂v}\\ E_{1v}=\frac{{\mathrm{j\ω\μ}}_0}{h_1}(A_1^{+}{e}^{-{\mathrm{jk}}_{1z}z}+A_1^{-}{e}^{{\mathrm{jk}}_{1z}z})\frac{\∂V}{\∂u}\\ H_{1u}=-\frac{{\mathrm{jk}}_{1z}}{h_1}(A_1^{+}{e}^{-{\mathrm{jk}}_{1z}z}-A_1^{-}{e}^{{\mathrm{jk}}_{1z}z})\frac{\∂V}{\∂u}\\ H_{1v}=-\frac{{\mathrm{jk}}_{1z}}{h_2}(A_1^{+}{e}^{-{\mathrm{jk}}_{1z}z}-A_1^{-}{e}^{{\mathrm{jk}}_{1z}z})\frac{\∂V}{\∂v}\end{array}---\left(7\right)$

In formula,WithRepresent incidence wave and the amplitude of echo in region 1 respectively.

Field distribution in region 2 can also be represented by the superposition of incidence wave and echo:

$\begin{array}{c}{H}_{2z}=T^2(A_2^{+}{e}^{-{\mathrm{jk}}_{2z}z}+A_2^{-}{e}^{{\mathrm{jk}}_{2z}z})V(u,v)\\ E_{2u}=-\frac{{\mathrm{j\ω\μ}}_c}{h_2}(A_2^{+}{e}^{-{\mathrm{jk}}_{2z}z}+A_2^{-}{e}^{{\mathrm{jk}}_{2z}z})\frac{\∂V}{\∂v}\\ E_{2v}=\frac{{\mathrm{j\ω\μ}}_c}{h_1}(A_2^{+}{e}^{-{\mathrm{jk}}_{2z}z}+A_2^{-}{e}^{{\mathrm{jk}}_{2z}z})\frac{\∂V}{\∂u}\\ H_{2u}=-\frac{{\mathrm{jk}}_{2z}}{h_1}(A_2^{+}{e}^{-{\mathrm{jk}}_{2z}z}-A_2^{-}{e}^{{\mathrm{jk}}_{2z}z})\frac{\∂V}{\∂u}\\ H_{2v}=-\frac{{\mathrm{jk}}_{2z}}{h_2}(A_2^{+}{e}^{-{\mathrm{jk}}_{2z}z}-A_2^{-}{e}^{{\mathrm{jk}}_{2z}z})\frac{\∂V}{\∂v}\end{array}---\left(8\right)$

Field distribution in region 3 only comprises transmitted wave:

$\begin{array}{c}{H}_{3z}=T^2{A}_3^{+}{e}^{-{\mathrm{jk}}_{3z}z}V(u,v)\\ E_{3u}=-\frac{{\mathrm{j\ω\μ}}_0}{h_2}{A}_3^{+}{e}^{-{\mathrm{jk}}_{3z}z}\frac{\∂V}{\∂v}\\ E_{3v}=\frac{{\mathrm{j\ω\μ}}_0}{h_1}{A}_3^{+}{e}^{-{\mathrm{jk}}_{3z}z}\frac{\∂V}{\∂u}\\ H_{3u}=-\frac{{\mathrm{jk}}_{3z}}{h_1}{A}_3^{+}{e}^{-{\mathrm{jk}}_{3z}z}\frac{\∂V}{\∂u}\\ H_{3v}=-\frac{{\mathrm{jk}}_{3z}}{h_2}{A}_3^{+}{e}^{-{\mathrm{jk}}_{3z}z}\frac{\∂V}{\∂v}\end{array}---\left(9\right)$

Wherein, region 1 is identical with region 3 medium, therefore propagation constant k_1zAnd k_3zEqual, all can be expressed as

$k_{1z}=k_{3z}=\sqrt{k^2-T^2}=\sqrt{{\mathrm{\ω}}^2{\mathrm{\μ}}_0{\mathrm{\ϵ}}_0-T^2}---\left(10\right)$

Propagation constant k in region 2_2zIn should comprise the impact of electrical conductivity, i.e.

$k_{2z}=\sqrt{k^2-T^2}=\sqrt{{\mathrm{\ω}}^2{\mathrm{\μ}}_c{\mathrm{\ϵ}}_e-T^2}---\left(11\right)$

ε in formula_e=ε_c-j σ/ω is the effective dielectric constant that conductive plate contains electrical conductivity impact.

The amplitude relation of the field of zones of different is determined below by interface condition.Separating surface (z=in region 1 and 2 0), derived continuously by the tangential component of electric field intensity and magnetic field intensity respectively:

${\mathrm{\μ}}_0(A_1^{+}+A_1^{-})={\mathrm{\μ}}_c(A_2^{+}+A_2^{-})---\left(12\right)$

$k_{1z}(A_1^{+}-A_1^{-})=k_{2z}(A_2^{+}-A_2^{-})---\left(13\right)$

At the separating surface (z=d) in region 2 and 3, derived continuously by the tangential component of electric field intensity and magnetic field intensity respectively:

${\mathrm{\μ}}_c(A_2^{+}{e}^{-{\mathrm{jk}}_{2z}d}+A_2^{-}{e}^{{\mathrm{jk}}_{2z}d})={\mathrm{\μ}}_0{A}_3^{+}{e}^{-{\mathrm{jk}}_{3z}d}---\left(14\right)$

$k_{2z}(A_2^{+}{e}^{-{\mathrm{jk}}_{2z}d}-A_2^{-}{e}^{{\mathrm{jk}}_{2z}d})=k_{3z}{A}_3^{+}{e}^{-{\mathrm{jk}}_{3z}d}---\left(15\right)$

By formula (14), (15), A2+ and A2-A3+ can be expressed as:

$\begin{array}{c}{A}_2^{+}=\frac{e^{{\mathrm{jk}}_{2z}d}{e}^{-{\mathrm{jk}}_{3z}d}}{2}(\frac{k_{3z}}{k_{2z}}+\frac{{\mathrm{\μ}}_0}{{\mathrm{\μ}}_c})A_3^{+}\\ A_2^{-}=\frac{e^{-{\mathrm{jk}}_{2}d}{e}^{-{\mathrm{jk}}_{3z}d}}{2}(\frac{{\mathrm{\μ}}_0}{{\mathrm{\μ}}_c}-\frac{k_{3z}}{k_{2z}})A_3^{+}\end{array}---\left(16\right)$

By formula (12), (13), A1+ A2+ and A2-can be expressed as:

$A_1^{+}=\frac{1}{2}\[A_2^{+}(\frac{k_{2z}}{k_{1z}}+\frac{{\mathrm{\μ}}_c}{{\mathrm{\μ}}_0})+A_2^{-}(\frac{{\mathrm{\μ}}_c}{{\mathrm{\μ}}_0}-\frac{k_{2z}}{k_{1z}})\]---\left(17\right)$

Convolution (16) and (17), it can be deduced that the conductive plate insertion loss IL to TE pattern_TEFor:

${\mathrm{IL}}_{TE}=20{\log }_{10}|e^{{\mathrm{jk}}_{2z}d}\frac{{(Z_{1TE}+Z_{2TE})}^2}{4Z_{1TE}{Z}_{2TE}}\[1-e^{-2{\mathrm{jk}}_{2z}d}{\left(\frac{Z_{1TE}-Z_{2TE}}{Z_{1TE}+Z_{2TE}}\right)}^2\]|---\left(18\right)$

Z in formula_1TEAnd Z_2TEIt is respectively the natural impedance of TE pattern in region 1 (3) and region 2

$Z_{1TE}=\frac{{\mathrm{\ω\μ}}_0}{k_{1z}},Z_{2TE}=\frac{{\mathrm{\ω\μ}}_c}{k_{2z}}---\left(19\right)$

The electromagnet shield effect (insertion loss) of the plane wave of vertical incidence can be expressed as by conductive plate:

$SE=20{\log }_{10}|e^{{\mathrm{jk}}_{c}d}\frac{{(Z_0+Z_c)}^2}{4Z_0{Z}_c}\[1-e^{-2{\mathrm{jk}}_{c}d}{\left(\frac{Z_0-Z_c}{Z_0+Z_c}\right)}^2\]|---\left(20\right)$

In formula,For plane wave in the natural impedance of free space,For plane wave in conductive plate Natural impedance,For plane wave propagation constant in conductive plate.

It is good conductor in view of detected materials under normal circumstances, i.e. meets condition σ > ω ε_c, then have:

$k_c=\mathrm{\ω}\sqrt{{\mathrm{\μ}}_c{\mathrm{\ϵ}}_e}=\mathrm{\ω}\sqrt{-{\mathrm{j\μ}}_c\mathrm{\σ}/\mathrm{\ω}}=(1-j)/\mathrm{\δ}---\left(21\right)$

In formula, δ is the electromagnetic wave depth of penetration in conductive plate,

On the other hand, the wave frequency owing to investigating is higher than the cut-off frequency of pattern, i.e.Therefore have

$\left|{\mathrm{\ω}}^2{\mathrm{\μ}}_c{\mathrm{\ϵ}}_e\right|>>\left|{\mathrm{\ω}}^2{\mathrm{\μ}}_c{\mathrm{\ϵ}}_c\right|>T^2---\left(22\right)$

And then the propagation constant of TE pattern in conductive plate can be reduced to:

$k_{2z}=\sqrt{{\mathrm{\ω}}^2{\mathrm{\μ}}_c{\mathrm{\ϵ}}_e-T^2}\≈k_c---\left(23\right)$

I.e. in conductive plate, TE pattern and plane wave have approximately equalised propagation constant.

To TE pattern, may certify that its natural impedance in conductive plate is much smaller than natural impedance in a vacuum, i.e.

|Z_1TE|>>|Z_2TE| (24)

Also have simultaneously for plane wave | Z₀|>>|Z_c|, therefore formula (18), (20) can be simplified to respectively:

${\mathrm{IL}}_{TE}=20{\log }_{10}\left|e^{(1+j)d/\mathrm{\δ}}\frac{Z_{1TE}}{4Z_{2TE}}(1-e^{-2(1+j)d/\mathrm{\δ}})\right|---\left(25\right)$

$SE=20{\log }_{10}\left|e^{(1+j)d/\mathrm{\δ}}\frac{Z_0}{4Z_c}(1-e^{-2(1+j)d/\mathrm{\δ}})\right|---\left(26\right)$

Then TE insertion loss and the difference DELTA of plane wave shield effectiveness_TEApproximate expression be:

Δ_TE=IL_TE-SE≈-10log₁₀(1-(T/k₀)²)=-10log₁₀(1-(f_c/f)²) (27)

This formula gives the transformational relation of the conductive plate insertion loss to TE pattern and the plane wave shield effectiveness of conductive plate. In formulaFor the free space natural impedance of electromagnetic wave,For the cut-off frequency of pattern, f is Wave frequency.Can be seen that Δ_TEApproximation unrelated with the electrical conductivity of material and size.It is computed, when detected materials meets condition During σ/ω ε > 1000, TE pattern insertion loss is unrelated with the electrical conductivity of material and size with the difference of plane wave shield effectiveness.

Step 5, utilizes the electric field shielding usefulness recorded and the corresponding anti-electrical conductivity pushing away detected materials of frequency, thus estimates Go out the conductivity range of detected materials.Wherein, the conductivity range of estimation detected materials can utilize formula (20) to realize.

Embodiment three:

The present embodiment is a preferred implementation of above-mentioned two embodiment.

Take the long a=10cm in cross section, the rectangular waveguide of wide b=5cm, conductive plate ε_c=ε₀, μ_c=μ₀And d=1mm.Calculate TE can be obtained₁₀The cut-off frequency f of pattern_c1=1.5GHz, TE₀₁The cut-off frequency f of pattern_c2=3GHz.

Fig. 3 gives when the electrical conductivity of conductive plate is respectively 10S/m, 100S/m and 1000S/m, and conductive plate is to TE₁₀Mould Formula insertion loss analytic formula (solid line, formula (18)) result of calculation and the correlation curve of full-wave simulation result, it can be seen that two Curve conformity is preferable, demonstrates the correctness of analytic formula.

Embodiment four:

The present embodiment is another preferred implementation of embodiment one and embodiment two.

Take the long a=10cm in cross section, the rectangular waveguide of wide b=5cm, can be calculated TE₁₀The cut-off frequency f of pattern_c1= 1.5GHz, TE₀₁The cut-off frequency f of pattern_c2=3GHz.Detected materials is anisotropic ideal conductor material, and its structure is thin Strip, d=1mm.

Fig. 4 be anisotropic material placement direction in rectangular waveguide be schematic diagram when 0 ° and 90 °, wherein Fig. 4 (a) Being 0 °, Fig. 4 (b) is 90 °.Fig. 5 gives when anisotropic material placement direction is respectively 0 ° and 90 °, anisotropic material To TE₁₀The full-wave simulation result of pattern insertion loss, wherein, corresponding 90 ° an of line of upside, corresponding 0 ° an of line of downside. During it can be seen that utilize rectangular waveguide test anisotropic material, E field polarization direction its electric field shielding usefulness different is the most different.

Above-described embodiment is only the present invention preferably detailed description of the invention, but protection scope of the present invention is not limited to This, any those familiar with the art in the technical scope that the invention discloses, the change that can readily occur in or replace Change, all should contain within protection scope of the present invention.Therefore, protection scope of the present invention should be with the protection model of claim Enclose and be as the criterion.

Claims (5)

1. a material electric field shielding effect test system based on rectangular waveguide, it is characterised in that described system includes: rectangle Waveguide, Network Analyzer, coaxial TEM mode rectangle TE₁₀Mode converter and radio frequency coaxial-cable, detected materials；

Described rectangular waveguide is the cylindrical shell that cross section is rectangle using metallic plate to make, from the centre of described cylindrical shell Laterally disconnect, be used for placing described detected materials；

Described coaxial TEM mode rectangle TE₁₀Mode converter has two, the respectively first coaxial TEM mode rectangle TE₁₀Mould Formula transducer and the second coaxial TEM mode rectangle TE₁₀Mode converter, described first coaxial TEM mode rectangle TE₁₀Mould First end of formula transducer is connected with the first end of described rectangular waveguide, described second coaxial TEM mode rectangle TE₁₀Pattern turns First end of parallel operation is connected with the second end of described rectangular waveguide；

Described radio frequency coaxial-cable has two sections, the respectively first radio frequency coaxial-cable and the second radio frequency coaxial-cable, and described first The two ends of radio frequency coaxial-cable respectively with described first coaxial TEM mode rectangle TE₁₀Second end of mode converter and described The input port of Network Analyzer connects, the two ends of described second radio frequency coaxial-cable respectively with described second TEM coaxial mould Formula rectangle TE₁₀Second end of mode converter and the output port of described Network Analyzer connect.

2. the method for the test material electric field shielding usefulness using test system as claimed in claim 1, it is characterised in that Said method comprising the steps of:

S1, calculates the TE of described rectangular waveguide₁₀Mode cutoff frequency f_c1TE with described rectangular waveguide₀₁Mode cutoff frequency f_c2, Calibrating described Network Analyzer, the test frequency range regulating described Network Analyzer is f_c1～f_c2；

S2, when not placing described detected materials in described rectangular waveguide, operates described Network Analyzer, records described in not placing Parameter during detected materials

S3, is placed horizontally in described detected materials gap in the middle of described rectangular waveguide, and treats described in two open ends compressions Measure and monitor the growth of standing timber material, again operate described Network Analyzer, record parameter when placing described detected materialsDescribed detected materials is wanted Asking and meet σ/ω ε > 1000, wherein: σ is the electrical conductivity of described detected materials, the angular frequency of electromagnetic wave when ω is test, ε is institute State the dielectric constant of detected materials；

S4, calculates the electric field shielding usefulness of described detected materials；

S5, utilizes the described electric field shielding usefulness recorded and the corresponding anti-electrical conductivity pushing away described detected materials of frequency, estimates The conductivity range of described detected materials.

Method the most according to claim 2, it is characterised in that the computing formula of described electric field shielding usefulness is:

$SE=S_{21}^{\left(1\right)}-S_{21}^{\left(2\right)}+{\mathrm{\Δ}}_{TE}$

Wherein,For not placing S during detected materials₂₁Parameter,For placing S during detected materials₂₁Parameter；Δ_TEFor revising Parameter, i.e. detected materials is to TE₁₀Pattern insertion loss and the detected materials difference to TEM mode insertion loss, Δ_TECalculating public Formula is:

Δ_TE=-10log₁₀(1-(f_c/f)²)

Wherein, f is wave frequency, f_cFor described rectangular waveguide TE₁₀Mode cutoff frequency.

Method the most according to claim 2, it is characterised in that described in estimate described detected materials conductivity range profit With infinitely great conductive plate to vertical incidence plane wave electromagnet shield effect formula:

$SE=20{\log }_{10}|e^{{\mathrm{jk}}_{c}d}\frac{{(Z_0+Z_c)}^2}{4Z_0{Z}_c}\[1-e^{-2{\mathrm{jk}}_{c}d}{\left(\frac{Z_0-Z_c}{Z_0+Z_c}\right)}^2\]|$

Wherein,For plane wave in the natural impedance of free space,For plane wave in conductive plate Natural impedance,For plane wave propagation constant in conductive plate, ε_e=ε_c-j σ/ω is that conductive plate contains conductance The effective dielectric constant of rate impact, ε_cFor the dielectric constant of conductive plate, μ_cFor the pcrmeability of conductive plate, σ is the conductance of conductive plate Rate, the angular frequency of electromagnetic wave when ω is test, d is the thickness of conductive plate, ε₀For permittivity of vacuum, μ₀For permeability of vacuum.

5. according to the method described in any one of claim 2-4, it is characterised in that with described method test anisotropic material not Electric field shielding usefulness during same electric field polarised direction.