CN102798766A - Method for testing microwave dielectric property of high-loss dielectric substance - Google Patents

Abstract

The invention discloses a method for testing microwave dielectric property of a high-loss dielectric substance. According to the method, a small-size sample to be tested is used, and a large-size and low-loss reference sample is introduced, so that the high loss of the sample to be tested is reduced, and the resonance peak is ensured to be observed. According to the changes of the resonance peak of a TE01 delta model when only the reference sample is arranged in a resonant cavity and the reference sample and the sample to be tested are simultaneously arranged in the resonant cavity, and the distribution of an electromagnetic field under the two conditions can be simulated by using finite element analysis, so that the dielectric constant and the dielectric loss of the sample to be tested at the resonance frequency can be obtained. According to the method, the characteristics of high test precision of the microwave resonance method is utilized, and the influence on the distribution of the electromagnetic field caused by the introduction of the sample to be tested, is considered, so that the defects of low precision of other conventional methods can be overcome from the test principle, and the accurate test of the microwave dielectric property of the high-loss substance can be realized. Meanwhile, the resonance frequency is decided by the reference sample with large size, so that the frequency conversion test can be realized by changing the dielectric constant or the size of the reference sample.

Description

A kind of method of testing high loss dielectric substance microwave dielectric property

Technical field

The invention belongs to the microwave testing field, the measuring technology of particularly high loss dielectric substance microwave dielectric property.

Background technology

High loss is (greater than 10 ^-2) dielectric substance such as ferroelectric material, huge dielectric constant material have important potential application foreground at microwave frequency band, but its microwave dielectric property is difficult to accurate test.The method of testing of high consumable material microwave dielectric property mainly comprises reflectometry, reflective-transmissive method and resonant cavity perturbation method.As far as the above two, the scattering parameter under the single frequency point directly is used for the calculating of dielectric properties, and along with the rising of specific inductive capacity, scattering parameter is more and more insensitive to the variation of specific inductive capacity, so measuring accuracy also sharply descends thereupon; Resonant cavity perturbation rule has been utilized the characteristic of microwave resonance, and precision is high slightly, but owing to consider to introduce the variation that electromagnetic field distributes in the cavity that sample causes, so the measuring accuracy can't guarantee equally that specific inductive capacity is higher the time.

Summary of the invention

The purpose of this invention is to provide a kind of method of testing high loss dielectric substance microwave dielectric property, this method has the precision height, is prone to realize the characteristics of frequency conversion test.

The method of the high loss dielectric substance of test of the present invention microwave dielectric property is used high Q value cylindrical metal resonator cavity test, and concrete testing procedure is following:

(1) cylindrical low-loss reference coupon A is positioned on the single crystal quartz support C in the cylindrical metal resonator cavity,, utilizes finite element analysis to calculate TE according to the size and the specific inductive capacity of reference coupon _{01 δ}The resonant frequency range that pattern is corresponding, and in this frequency range, find harmonic peak with vector network analyzer, write down resonance frequency f ₀₁And resonance frequency f ₀₁Near scattering parameter S _11,1With the variation of frequency, obtain the no-load quality factor q with curve fitting method _U1

(2) according to resonance frequency f ₀₁And the size of reference coupon A, utilize finite element analysis and the accurate DIELECTRIC CONSTANTS of iteration Method reference coupon A _{R, A}, the electromagnetic field that obtains according to finite element analysis distributes, by the no-load quality factor q _U1Calculate reference coupon A at resonance frequency f ₀₁The dielectric loss tan δ at place _A

(3) sample to be tested B is positioned on the reference coupon A, the size of reference coupon A is utilized vector network analyzer record resonance frequency f greater than the size of sample to be tested B ₀₂And resonance frequency f ₀₂Near scattering parameter S _11,2With the variation of frequency, obtain the no-load quality factor q with curve fitting method _U2

(4) according to size, the DIELECTRIC CONSTANTS of reference coupon A and sample to be tested B _{R, A}And resonance frequency f ₀₂, utilize the DIELECTRIC CONSTANTS of finite element analysis and iteration Method sample to be tested B _{R, B}, the electromagnetic field that obtains according to finite element analysis distributes, by the no-load quality factor q _U2Calculate sample to be tested B at resonance frequency f ₀₂The dielectric loss tan δ at place _B

(5) size or the specific inductive capacity of change reference coupon A, the frequency conversion test of sample to be tested B microwave dielectric property is realized in repeating step (1)-(4).

Low-loss described in the present invention refers to that the dielectric loss of dielectric substance is less than 10 ^-3, high loss refers to that the dielectric loss of dielectric substance is greater than 10 ^-2

Method of testing provided by the invention has been utilized the high characteristic of microwave resonance method test dielectric properties precision; And the introducing of having considered sample to be tested influence that electromagnetic field is distributed; So can overcome existing reflectometry, reflective-transmissive method and the low defective of resonant cavity perturbation method measuring accuracy from test philosophy, thereby realize the high precision measurement of high consumable material microwave dielectric property.Used the low-loss reference coupon big among the present invention, be for the high loss that reduces sample to be tested contribution, thereby guarantee to observe harmonic peak the resonator system total losses than the sample to be tested size.Simultaneously, because resonance frequency is mainly by larger-size reference coupon decision, so can realize the frequency conversion test easily through specific inductive capacity and the size that changes reference coupon.

The present invention can to specific inductive capacity less than 1000, dielectric loss is greater than 10 ^-2The dielectric properties of high consumable material in the 1-20GHz frequency range carry out exact evaluation.The relative error of specific inductive capacity and dielectric loss is all in 5%.

Description of drawings

Fig. 1 is the cross sectional representation of cylindrical metal resonator cavity, wherein, only places reference coupon among the figure (a), then puts into reference coupon and sample to be tested simultaneously among the figure (b).

Fig. 2 is that scattering parameter is with the synoptic diagram of change of frequency near the resonance frequency, and wherein solid line is for only placing the situation of reference coupon, and dotted line is for put into the situation of reference coupon and sample to be tested simultaneously.

Embodiment

TE _{01 δ}Pattern is the of paramount importance a kind of mode of resonance of cylindrical metal resonator cavity, has been widely used in the accurate test of low-loss material microwave dielectric property.Electric field in this pattern has only the component E along hoop _θIn cylindrical coordinate, the E of every bit _θAll satisfy:

$\frac{{\∂}^2{E}_{\mathrm{\θ}}}{{\∂r}^2}+\frac{{\∂}^2{E}_{\mathrm{\θ}}}{{\∂z}^2}+\frac{1}{r}\frac{{\∂E}_{\mathrm{\θ}}}{\∂r}+({\mathrm{\β}}^2-\frac{1}{r^2})E_{\mathrm{\θ}}=0,---\left(1\right)$

β wherein ²=ω ²μ ε=(2 π f ₀) ²μ ε, μ and ε are respectively the magnetic permeability and the specific inductive capacity of filling medium, and ω is an angular frequency, f ₀Be resonance frequency, r, z represent radially the coordinate with vertical direction respectively.When the specific inductive capacity of all packing materials in the cavity and size are known, utilize numerical methods such as finite element analysis, and introduce the cavity metallic walls E of place _θ=0 boundary condition, but solving equation (1).With resonance frequency f ₀For the equation (1) of unknown quantity has unlimited a plurality of separating, its minimum value is TE _{01 δ}The resonance frequency that pattern is corresponding, and the electromagnetic field that can try to achieve in the cavity distributes.Distribute based on the electromagnetic field in the cavity, can obtain the electric energy fill factor, curve factor of every kind of medium

$P_{e,i}=\frac{\underset{S_i}{\∫}{\mathrm{\ϵ}}_{r,i}{E}_{\mathrm{\θ}}^2\·{\mathrm{rdS}}_i}{\underset{i}{\mathrm{\Σ}}\underset{S_i}{\∫}{\mathrm{\ϵ}}_{r,i}{E}_{\mathrm{\θ}}^2\·{\mathrm{rdS}}_i},---\left(2\right)$

ε wherein _{R, i}Specific inductive capacity for medium.The no-load quality factor q of resonator system _uCan be expressed as:

$\frac{1}{Q_u}=\underset{i}{\mathrm{\Σ}}{P}_{e,i}\tan {\mathrm{\δ}}_i+\frac{1}{Q_c},---\left(3\right)$

Tan δ wherein _iBe the dielectric loss of medium, Q _cBe the quality factor of metallic walls, can try to achieve by the metallic surface conductivity.

The method of the high loss dielectric substance of test of the present invention microwave dielectric property, step is following:

(1) with diameter D _A, thickness H _ACylindrical low-loss reference coupon A be positioned on the single crystal quartz support C in the cylindrical metal resonator cavity, shown in Fig. 1 (a).According to the size and the specific inductive capacity of reference coupon, utilize finite element analysis to calculate TE _{01 δ}The resonant frequency range that pattern is corresponding, and in this frequency range, find harmonic peak with vector network analyzer, write down resonance frequency f ₀₁And resonance frequency f ₀₁Near scattering parameter S _11,1With the variation of frequency, shown in the solid line among Fig. 2, obtain the no-load quality factor q with curve fitting method _U1

(2) when only placing reference coupon in the cavity, the resonance frequency f of resonator system ₀₁Can be expressed as:

f ₀₁=g ₁(ε _r，A,D _A,H _A)，(4)

G wherein ₁Function for by formula (1) decision utilizes finite element analysis and the accurate DIELECTRIC CONSTANTS of iteration Method reference coupon A _{R, A}And corresponding electromagnetic field distributes.The dielectric loss of single crystal quartz support is very low, can ignore, so up-to-date style (3) can be rewritten as:

$P_{e,A1}\tan {\mathrm{\δ}}_A=\frac{1}{Q_{u1}}-\frac{1}{Q_{c1}}.---\left(5\right)$

The electromagnetic field that obtains according to finite element analysis distributes, by the no-load quality factor q _U1Calculate reference coupon A at resonance frequency f ₀₁The dielectric loss tan δ at place _A

(3) with diameter D _B, thickness H _BSample to be tested B be positioned on the reference coupon A, the size of sample to be tested B is less than reference coupon A, shown in Fig. 1 (b).Utilize vector network analyzer record resonance frequency f ₀₂And resonance frequency f ₀₂Near scattering parameter S _11,2With the variation of frequency, shown in the dotted line among Fig. 2, obtain the no-load quality factor q with curve fitting method _U2

When (4) placing reference coupon and sample to be tested simultaneously in the cavity, the resonance frequency f of resonator system ₀₂Can be expressed as:

f ₀₂=g ₂(ε _r，A,D _A,H _A,ε _r，B,D _B,H _B)，(6)

G wherein ₂Be function by formula (1) decision.Simultaneously, f ₀₂Usually only than f ₀₁Low several MHz can think that reference coupon A is at f ₀₁And f ₀₂The specific inductive capacity at place is identical with dielectric loss, so the DIELECTRIC CONSTANTS of finite element analysis capable of using and iteration Method sample to be tested B _{R, B}And corresponding electromagnetic field distributes.This up-to-date style (3) can be rewritten as:

$P_{e,A2}\tan {\mathrm{\δ}}_A+P_{e,B2}\tan {\mathrm{\δ}}_B=\frac{1}{Q_{u2}}-\frac{1}{Q_{c2}},---\left(7\right)$

The electromagnetic field that obtains according to finite element analysis distributes, by the no-load quality factor q _U2Calculate sample to be tested B at resonance frequency f ₀₂The dielectric loss tan δ at place _B

(5) size or the specific inductive capacity of change reference coupon A, the frequency conversion test of sample to be tested B microwave dielectric property is realized in repeating step (1)-(4).

Embodiment 1

To having the BaTiO of high dielectric loss ₃The microwave dielectric property of ferroelectric ceramics is tested.

Sample to be tested B is the BaTiO of diameter 2mm, thickness 0.2mm ₃Pottery; Low-loss reference coupon A is the Ca of diameter 12mm, thickness 1-5mm _1.15Nd _0.85Al _0.85Ti _0.15O ₄, Ba ₂Ti ₉O ₂₀And Ba _1.85Sm _4.1Ti ₉O ₂₄Pottery.

Test result is as shown in table 1.

Table 1

Know by table 1: with method test b aTiO provided by the invention ₃The pottery microwave dielectric property the time, in the frequency range of 1-20GHz, have good repeatability.

Embodiment 2

To having the CaCu of high dielectric loss ₃Ti ₄O ₁₂The microwave dielectric property of ferroelectric ceramics is tested.

Sample to be tested B is the CaCu of diameter 3mm, thickness 0.5mm ₃Ti ₄O ₁₂Pottery; Low-loss reference coupon A is the Ca of diameter 12mm, thickness 1-5mm _1.15Nd _0.85Al _0.85Ti _0.15O ₄, Ba ₂Ti ₉O ₂₀And Ba _1.85Sm _4.1Ti ₉O ₂₄Pottery.

Test result is as shown in table 2.

Table 2

Know by table 2: with method test CaCu provided by the invention ₃Ti ₄O ₁₂The pottery microwave dielectric property the time, in the frequency range of 1-20GHz, have good repeatability.

Claims (1)

1. One kind the test high loss dielectric substance microwave dielectric property method, it is characterized in that may further comprise the steps:

   (1) cylindrical low-loss reference coupon A is positioned on the single crystal quartz support C in the cylindrical metal resonator cavity,, utilizes finite element analysis to calculate TE according to the size and the specific inductive capacity of reference coupon _{01 δ}The resonant frequency range that pattern is corresponding, and in this frequency range, find harmonic peak with vector network analyzer, write down resonance frequency f ₀₁And resonance frequency f ₀₁Near scattering parameter S _11,1With the variation of frequency, obtain the no-load quality factor q with curve fitting method _U1

   (2) according to resonance frequency f ₀₁And the size of reference coupon A, utilize finite element analysis and the accurate DIELECTRIC CONSTANTS of iteration Method reference coupon A _{R, A}, the electromagnetic field that obtains according to finite element analysis distributes, by the no-load quality factor q _U1Calculate reference coupon A at resonance frequency f ₀₁The dielectric loss tan δ at place _A

   (3) sample to be tested B is positioned on the reference coupon A, the size of reference coupon A is utilized vector network analyzer record resonance frequency f greater than the size of sample to be tested B ₀₂And resonance frequency f ₀₂Near scattering parameter S ₁₁₂With the variation of frequency, obtain the no-load quality factor q with curve fitting method _U2

   (4) according to size, the DIELECTRIC CONSTANTS of reference coupon A and sample to be tested B _{R, A}And resonance frequency f ₀₂, utilize the DIELECTRIC CONSTANTS of finite element analysis and iteration Method sample to be tested B _{R, B}, the electromagnetic field that obtains according to finite element analysis distributes, by the no-load quality factor q _U2Calculate sample to be tested B at resonance frequency f ₀₂The dielectric loss tan δ at place _B

   (5) size or the specific inductive capacity of change reference coupon A, the frequency conversion test of sample to be tested B microwave dielectric property is realized in repeating step (1)-(4).

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