JPH06308177A - Apparatus and method for measuring dielectric constant - Google Patents

Abstract

PURPOSE:To make it possible to measure the dielectric constant simply in high accuracy even for not only high-loss material but also ordinary-loss material by filling the cavity of a two-split cavity resonator with a dielectric substance whose dielectric constant and dielectric dissipation factor are known, holding the planar dielectric sample with agreed divided faces, and constituting the resonator. CONSTITUTION:A dielectric substance 4 is filled in a cavity 3 of a cavity resonator 2. The faces of the two-split left-right symmetric cavity resonator 2 are made to agree. A planar dielectric sample 6 is held between the faces, and a resonator 1 is constituted. Then, the resonance frequency f0 at the TE011 mode of the resonator 1 and the no-load Q are measured. The dielectric constant epsilon' and the dielectric dissipation factor tandelta are obtained by the expressions. In the expression, L is the thickness of the dielectric sample, R and M are the radius and the height of the filled dielectric substance, epsilon'1 and epsilon'2 are the dielectric constants of the dielectric sample 6 and the filled dielectric substance 4, beta1 and beta2 are the phase constants of the regions 1 and 2, (c) is the luminous flux J'0 is the differential of the first-class Bessel function in 0 order and omega is the resonance angular frequency. Thus, the dielectric constant can be obtained simply in high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a measuring device and a measuring method for measuring the dielectric constant of various dielectric ceramics used as electronic circuit boards and electronic parts in the frequency range of microwaves.

[0002]

2. Description of the Related Art Conventionally, various dielectric ceramics have been widely used as a dielectric material in electronic circuit boards, electronic parts and the like.
Silver (Ag) used as an electrode material, for example, as an electronic circuit board or electronic component used in the frequency range of 3 GHz
Alumina (Al ₂ O ₃ ) that can be co-fired with copper and copper (Cu)
Dielectric ceramics having a relative permittivity of 5 to 20, which is represented by a low-temperature fired substrate containing as a main component, has been actively used.

In this regard, when applied, the dielectric properties of the dielectric ceramics include dielectric constant, dielectric loss tangent, and others.
The dielectric constant such as the temperature characteristic of the resonance frequency is listed as an evaluation item. As the dielectric characteristic of the dielectric ceramic in the frequency range to be actually used, for example, the measurement accuracy is 1% or less in the relative permittivity, For the tangent, a measurement accuracy of about 1 × 10 ⁻⁵ is required.

Conventionally, as a microwave dielectric constant measuring method, the most accurate and standard measuring method is, for example, a both-end short-circuiting method in which an end face of a dielectric cylindrical sample is short-circuited by two conductor plates to form a resonator. There are known a dielectric cylinder resonator method, a cavity resonator method in which a resonator is formed by sandwiching a flat plate-shaped dielectric sample between two divided cylindrical cavity resonators.

However, the both-end short-circuit type dielectric cylindrical resonator method has a problem that the measurement frequency is limited by the relative permittivity and size of the dielectric material to be measured, and the cavity resonator method is Since the measurement frequency is mainly limited by the size of the resonator, when measuring the dielectric constant by changing the frequency, it is necessary to fabricate many cavity resonators and dielectrics of different sizes and measure for each frequency. However, there is a limit to the size of the measurement sample that can be manufactured in order to maintain the reproducibility of dielectric properties.

Therefore, when the dielectric constant of a dielectric sample having a relative dielectric constant of 5 to 20 is measured by the above method, the measurable frequency range is limited to 5 to 20 GHz, and the required 1 to
It was difficult to measure in the frequency region of 3 GHz.

Therefore, as a relatively simple method capable of measuring the dielectric characteristics in the frequency range of 1 to 3 GHz, the stripline resonator method, the dielectric resonator perturbation method, the reflected wave method, etc. have been proposed. (JP-A-3-5686)
No. 6, JP-A-3-286601).

[0008]

However, in the stripline resonator method, the two dielectric samples 14 and 15 are superposed so that the stripline 13 is sandwiched therebetween, and the dielectric samples 14 and 15 are provided on the upper and lower surfaces thereof, respectively. Ground conductor surface 16,
17 is a method of obtaining the dielectric constant from the resonance characteristics of the triplate resonator having the structure 17 described above.
In the case of stacking the 15 pieces, it is difficult to apply the method to the dielectric ceramics, because a gap between the two dielectric samples is likely to occur in a material having no flexibility and the measurement accuracy may be deteriorated. is there.

In the dielectric resonator perturbation method, a dielectric sample 19 is inserted between two TE ₀₁ δ mode resonators 18 which are vertically symmetrically arranged, and the resonance characteristics change before and after the insertion. This is a method for obtaining the dielectric constant of a dielectric sample by using a perturbation formula of an electromagnetic field. Since the perturbation formula itself is an approximate solution, there is a systematic error, and the measurable range of the dielectric loss tangent is 10 ^−. There is a problem of being restricted to ⁴ to 10 ^-2 .

Further, since the reflected wave method is also a method in which the transmission line 20 is terminated by the dielectric sample 21 and the reflection coefficient is measured to obtain the dielectric constant, when measuring low-loss dielectric ceramics, There is a problem in that the magnitude of the reflection coefficient becomes extremely close to 1 and the measurement accuracy decreases.

As described above in detail, in each of the above-mentioned measuring methods, although the dielectric constant can be measured in the frequency range actually used, there is a problem that the accuracy of the measured value does not satisfy the above-mentioned requirement.

[0012]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has a microwave frequency range, especially 1 to 3 GHz.
It is an object of the present invention to provide a dielectric constant measuring device and a measuring method thereof, which can easily measure the dielectric constant satisfying the required accuracy not only for a high loss material but also for a low loss material in the frequency region of.

[0013]

A dielectric constant measuring device according to the present invention is such that a cavity of a cavity resonator divided into two is filled with a cylindrical dielectric having a known relative permittivity and dielectric loss tangent, and the plane matching is achieved. It is characterized in that a flat plate-shaped dielectric sample is sandwiched between two symmetrically symmetric resonator parts having the above-mentioned division surface to constitute a resonator.

On the other hand, the method for measuring the dielectric constant is such that the surface of the dielectric material filled in the cavity of the cavity resonator and the bilaterally symmetric cavity resonator are made to coincide with each other, and a flat dielectric sample is placed between them. The resonance frequency f ₀ of the TE ₀₁₁ mode and the no-load Q of the resonator constituted by sandwiching are measured, and the relative permittivity ε ′ and the dielectric loss tangent tan δ are measured.

[0015]

[Equation 1]

And

[0017]

[Equation 2]

It is characterized by being obtained from the equation (1).

The dielectric filled in the cavity of the cavity resonator has a microwave frequency range in consideration of the dimensions of a measurement sample that can be manufactured to maintain the reproducibility of dielectric characteristics and the dimensions of a practical resonator. In particular, in order to measure the dielectric constant in the frequency range of 1 to 3 GHz, the relative dielectric constant is 10 to 10
The range of 0 is good, and as a concrete dielectric material, a single crystal having a small dielectric loss tangent, such as sapphire, is suitable.

[0020]

The dielectric constant measuring device of the present invention is designed such that a cylindrical cavity resonator filled with a dielectric material having a known relative permittivity and dielectric loss tangent is divided at a central portion, and a flat plate-shaped dielectric measurement sample is provided therebetween. Since the resonator is sandwiched between the
The resonance frequency of the ₀₁₁ mode, that is, the measurement frequency of the dielectric constant is lowered.

This means that the dielectric material filled in the cavity acts so as to reduce the resonance frequency as the relative permittivity increases, and specifically, the resonance frequency is the measurement frequency of the conventional cavity resonator method. Since it is about 1 / √ε ^′ ₂ , the dielectric constant in the microwave frequency region, particularly in the frequency region of 1 to 3 GHz can be measured by adjusting the magnitude of the relative permittivity and the dimensions of the resonator.

As the dielectric material with which the cavity of the cavity resonator is filled, the above-mentioned single crystal such as sapphire is used to reduce the dielectric loss that occurs in the filled dielectric material and to have a dielectric loss tangent of 10. ^It can also be applied to the measurement of low-loss dielectric ceramics of ^-5 to 10 ^-4 .

Further, since the method for measuring the dielectric constant of the present invention can apply the exact solution of the resonance electromagnetic field assuming a cavity resonator for analysis, the error included in the calculation becomes extremely small,
A calculation error caused by assuming a cavity resonator for analysis is 1% or less in relative permittivity and 1 × 10 ⁻⁵ or less in dielectric loss tangent.

[0024]

The following is a detailed description of the dielectric constant measuring apparatus and the measuring method thereof according to the present invention. FIG. 1 is a cross-sectional view showing a resonator which is a main part of a dielectric constant measuring device according to the present invention, and FIG. 2 is a resonance which is a main part of a dielectric constant measuring device according to the present invention assumed for analysis. It is sectional drawing which shows a container.

In the figure, reference numeral 1 is a bilaterally symmetric cavity 2, and a cavity 3 is filled with a dielectric 4 having a known relative permittivity and dielectric loss tangent, and a plane-shaped dielectric is formed by a plane-divided plane 5. This is a dielectric constant measuring resonator forming an essential part of a dielectric constant measuring device configured by sandwiching a body sample 6.

In the resonator 1, since the peripheral edge portion 7 of the dielectric sample 6 is outside the resonator 1, the electromagnetic field slightly leaks to the outside, and an exact solution of the electromagnetic field cannot be obtained. Can not. Therefore, assuming a resonator for analysis in which the dielectric sample 6 is completely embedded in the resonator ₁ , the relative permittivity ε'1 is calculated from the resonance frequency f _{0 according} to the following _equations .

In FIG. 2, 10 is the thickness L of the dielectric sample, and 11 is the diameter 2R of the dielectric 4 filled in the cavity.
And 12 is the height M of the dielectric 4.

The dielectric constant epsilon _'1 can be calculated from the following formula obtained by the continuity of the tangential component of the electromagnetic field in the region 2 in the regions 1 and 9 of 8 shown in FIG.

[0029]

[Equation 1]

Next, the dielectric loss tangent ta of the flat plate-shaped dielectric sample
nδ ₁ is obtained from the measured values of the unloaded Q and Q _{u in} the TE ₀₁₁ mode of the resonator shown in FIG. However, the calculation of the dielectric loss tangent is performed by using the resonator of the dielectric constant measuring apparatus according to the present invention shown in FIG.

The unloaded Q and Q _u in FIG. 2 are given by the following equations.

[0032]

[Equation 3]

However, W ₁ ^e and W ₂ ^e are stored energies of the electric fields of the regions 1 and 2, respectively, and P _cy1 and P _cy2
Is the conductor loss on the sidewalls of regions 1 and 2, respectively, and P
_end is the conductor loss in the end plate.

Further, P _d1 and P _d2 are dielectric losses in the regions 1 and 2, respectively, and the dielectric loss tangents of the regions 1 and 2 are tan.
If δ ₁ and tan δ ₂ , then P _d1 = ωW ₁ ^e tanδ ₁ P _d2 = ωW ₂ ^e tan δ ₂ .

From the relationship between the above equation 3 and the dielectric loss, the dielectric loss tangent tan δ ₁ of the dielectric sample is expressed by the following equation.

[0036]

[Equation 2]

It is shown by.

Here, W ₁ ^e in the TE ₀₁₁ mode,
W ₂ ^e , P _cy1 , P _cy2, and P _end are each represented by the following formula.

[0039]

[Equation 4]

[0040]

[Equation 5]

[0041]

[Equation 6]

[0042]

[Equation 7]

[0043]

[Equation 8]

However, R _s is the surface resistance of the inner wall of the resonator, calculated from its effective conductivity, A and B are the amplitude coefficients of the electromagnetic field in the regions 1 and 2, and B / A = -cosX / sinY Have a relationship.

Next, the dielectric constant measuring apparatus and the measuring method of the present invention will be explained based on concrete examples. As a resonator for measuring the dielectric constant at a measurement frequency of 3 GHz, a cylindrical cavity resonator made of oxygen-free copper having a cavity having an inner diameter of 40 mm and a height of 40 mm is divided into two, and each of the two divided cavities has a dielectric loss tangent. A single crystal sapphire cylinder, which is a small, low-loss material, having an end face perpendicular to the C-axis was fitted, and the divided faces were made to coincide with each other to form a resonator constituent member.

The relative permittivity of the sapphire in the direction perpendicular to the C axis is 9.4, and when the cylindrical cavity resonator of the above size is filled, the TE ₀₁₁ mode resonance frequency is 3.2 G.
It becomes Hz. Table 1 shows the constants of the resonator whose measurement frequency is 3 GHz.

[0047]

[Table 1]

Next, the resonator constituent member has a purity of 96%.
And a thickness of 1.0 mm consisting of 90% alumina sintered body,
A dielectric sample having a diameter of 50.0 mm is sandwiched and tightened to form a resonator for measuring the dielectric constant, and coaxial cables are arranged on the input side and the output side of the resonator, and a loop is provided at the tip thereof. After that, a device for measuring the dielectric constant was produced. Table 2 shows the result of measurement using the thus-obtained dielectric constant measuring device together with the result of measurement by the conventional cavity resonator method.

[0049]

[Table 2]

From the results shown in Table 2, in the method for measuring the dielectric constant of the present invention, the measurement accuracy is ± 0.1 (1
%) Or less, and the dielectric loss tangent is ± 0.1 × 10 ⁻⁴
It was below.

The present invention is not limited to the above embodiment.

[0052]

Industrial Applicability The dielectric constant measuring apparatus and the measuring method therefor according to the present invention include a cavity resonator in which the cavity of the cavity resonator is filled with a dielectric having a known relative permittivity and dielectric loss tangent, and the cavity is filled with the dielectric. Is divided into two at the central part, and a flat plate-shaped dielectric measurement sample is sandwiched between them to form a resonator, and the resonance frequency f ₀ of the TE ₀₁₁ mode and the unloaded Q of the resonator are measured to measure the dielectric constant. Since the dielectric constant of the body sample is obtained, the dielectric of any shape can be accurately and easily deviated from the true value not only for high-loss materials but also for low-loss materials in the frequency range of 1 to 3 GHz. It is possible to measure extremely small dielectric constants.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a resonator which is a main part of a device for measuring a dielectric constant according to the present invention.

FIG. 2 is a cross-sectional view showing a resonator which is a main part of a dielectric constant measuring apparatus according to the present invention which is assumed for analysis.

FIG. 3 is a cross-sectional view showing a main part of a stripline resonator.

FIG. 4 is a cross-sectional view showing a main part of a measuring device of a dielectric resonator perturbation method.

FIG. 5 is a diagram showing a circuit for explaining an outline of a reflected wave method.

[Explanation of symbols]

 1 Resonator for dielectric constant measurement 2 Cavity resonator 3 Cavity 4 Dielectric 5 Dividing surface 6 Dielectric sample

Claims (2)

[Claims] 1. A resonator in which a cavity of a cavity resonator divided into two is filled with a dielectric material whose relative permittivity and dielectric loss tangent are known, and a flat plate-shaped dielectric sample is sandwiched between plane-matched division surfaces. An apparatus for measuring a dielectric constant, comprising: 2. A cavity of a cavity resonator divided into two is filled with a dielectric material having a known relative permittivity and dielectric loss tangent, and a planar dielectric sample is sandwiched between plane-matched division surfaces to form a resonator. And the resonance frequency f ₀ and the unloaded Q of the resonator are measured, and the relative permittivity ε ^' and the dielectric loss tangent tan δ are respectively expressed by the following equations: And A method for measuring a dielectric constant, which is characterized by further obtaining.