JPH0460228B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for measuring the relative permittivity of a dielectric plate and a measuring instrument used in this method.

(Prior art) As disclosed in Japanese Unexamined Patent Publication No. 56-57302, a TEM has a plurality of dielectric coaxial TEM resonators and a capacitor electrode provided on a single dielectric substrate. There is a filter in which inter-stage coupling is obtained by connecting the center conductor of each resonator to a capacitor electrode.

When employing a dielectric substrate for use in such a filter, it was necessary to know its relative dielectric constant.

Conventionally, a capacitor was constructed by providing electrodes of appropriate dimensions and shapes on both sides of a sample substrate, and the relative permittivity was determined by measuring the capacitance.

However, with this method, the measurement frequency is usually ~
Up to about 10MHz, 1000MHz actually used
There is a possibility that the relative permittivity is different from that exhibited in a similar frequency range. It is necessary to mold the dielectric substrate to appropriate dimensions and form electrodes, which results in a destructive test, and it takes time to obtain measurement results. There is also an error of about 1% in measurement accuracy.

(Problems to be Solved by the Invention) Therefore, an object of the present invention is to measure the dielectric constant of a dielectric plate non-destructively, quickly, and with high precision.

Another object of the invention is to provide a measuring instrument that can employ such a method.

(Means for Solving the Problem) That is, the present invention arranges two dielectric resonators with their axes aligned and facing each other, and aligns the axial directions of two dielectric resonators with each other, and sets the stationary point of the electric field intensity distribution obtained using TE ₀₁ δ mode resonance. This is a method for measuring the dielectric constant of a dielectric plate, which is characterized in that the dielectric constant is determined by inserting a sample plate and measuring the change in resonance frequency.

In addition, this invention provides a method for fixing two dielectric resonators in a case with their axes aligned and facing each other.
TE ₀₁ Relative permittivity of a dielectric plate, characterized by having a δ-mode resonance system, means for positioning a sample plate at a stopping point of the obtained electric field intensity distribution, and means for determining the change in resonance frequency depending on the presence or absence of a sample plate. It is a rate measuring instrument.

(Example) FIG. 1 is a diagram showing the main parts of a measuring instrument related to the present invention. In the figure, 1 is a metal case, 2
is a dielectric resonator, and 3 is a holding stand. The case 1 has a cylindrical space inside and a holding base 3 concentrically therewith.
is fixed, and the resonator 2 is fixed thereon. The top surface of the case 1 is open. Above such a structure, a similar structure is placed facing each other. 11 is a metal case similar to case 1; 12 is a dielectric resonator similar to the resonator; and 13 is a holder similar to holder 3. In this way, resonators 2 and 12
The feature is that the fixed sides of the non-holding bases are facing each other. It is assumed that the resonators 2 and 12 are both cylindrical in shape, for example, and utilize TE ₀₁ δ mode resonance. The upper case 11 is provided with input/output coupling means 14 and 15, and is connected to a resonance frequency measuring device 16. Input/output coupling means 1
4 and 15 use connecting rods or connecting loops as shown. There is a gap between cases 1 and 11, into which a dielectric substrate 17, which is a sample, is inserted and temporarily held on a suitable holding stand (symbolically represented by numeral 18 in the figure). do. This holding position is intermediate between resonators 2 and 12.

When the substrate 17 is inserted into a resonant system having such a structure, the resonant frequency changes slightly, which is expressed by the following equation.

−δω／ω＝(ε ₂ −ε ₀ )∫ _v2 〓 ₁・〓 ₂ dv／ε ₀ ∫｜
〓 ₁ | ² dv Here, ω is the resonant angular frequency of the resonant system before inserting the substrate 17, δω is the amount of change in the resonant angular frequency of the resonant system due to inserting the substrate 17, and ε ₀ is the change in the resonant angular frequency of the resonant system before inserting the substrate 17. The dielectric constant, ε ₂ is the product of the relative dielectric constant εr of the substrate 17 and the permittivity of vacuum ε ₀ , E ₁ is the electric field vector before the substrate 17 is inserted, 〓 ₂ is the electric field vector after the substrate 17 is inserted, V ₂ is the substrate 17 represents the volume of each. Now, board 1
Assuming that the electric field distribution does not change before and after the insertion of 7, the ratio of the energy stored in the entire resonant system to the energy stored in the substrate 17 is (εr−
1) is the frequency perturbation ratio, so by measuring the change in the resonant frequency, the substrate 17
The relative permittivity of is determined. In more detail, there is a substrate whose dielectric constant is known to serve as a reference, and the frequency perturbation ratio of that substrate can be found by measuring changes in the resonance frequency. Let this value be −δω ₁ /ω. Now, if the value of the frequency perturbation ratio when the sample plate is inserted is −δω ₂ /ω, then ∫v ₂ 〓 ₁・〓 ₂ dv／∫｜〓 ₁ ｜ ² dv is the same for both the reference substrate and the sample substrate. Since it is unchanged, δω ₂ /δω ₁ = εr ₂ ^-1 /εr ₁ ^-1 .

Here, ε _r1 is the relative permittivity of the reference substrate, and ε _r2 is the relative permittivity of the sample substrate.

Such a dielectric constant measurement method can be said to be suitable for managing variations among products. In other words, when the required allowable range of dielectric constant is determined, this allowable range is replaced with the allowable change range of the resonant frequency, and when a sample is inserted, the resonant frequency changes within this allowable change range. If you choose just the right method, you can use a more efficient work method.

Note that the dielectric constant of the sample is determined by multiplying the dielectric constant determined as described above by the dielectric constant of vacuum.

Further, the dielectric loss (tan δ) of the sample can also be measured using the above-mentioned measuring instrument, and is determined by the following equation.

tanδ=(1/Q ₀ ¹ −1/Q ₀ )ω/δω Here, Q ₀ is the unloaded Q of the resonant system before inserting the sample,
Q ₀ ¹ is the non-negative Q of the resonant system after inserting the sample.

In this way, the dielectric constant ε ₂ and dielectric loss of the sample are
Once tanδ is determined, the complex permittivity ε is ε=ε ₂ (1
−jtanδ).

In addition, when using the above-mentioned measuring instrument, the strength of the electric field strength in the axial direction of each resonator 2 and 12 in the TE ₀₁ δ mode is as shown in Fig. 2 in the gap part between the resonators 2 and 12. Since it does not change, it has the advantage that there is little measurement error due to variations in the insertion position.

(Effects) As is clear from the above examples, according to the present invention, the relative permittivity εr (as well as the permittivity _ε2 and complex permittivity ε, if necessary) of a dielectric plate can be measured non-destructively and at high speed. .

Further, according to the present invention, it is possible to accurately measure the dielectric constant of a dielectric plate in the microwave region.

Furthermore, according to the present invention, it is possible to perform measurements with good reproducibility, that is, with small measurement errors.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the main parts of a measuring instrument related to the present invention, and FIG. 2 is a diagram showing the electric field distribution. 1 and 11 are metal cases, 2 and 12 are dielectric resonators, and 17 is a dielectric substrate.

Claims (1)

[Claims] 1. Two dielectric resonators are placed facing each other with their axes aligned, and a sample plate is inserted into the stationary point of the electric field strength distribution obtained using TE ₀₁ δ mode resonance to determine the resonant frequency. A method for measuring the relative permittivity of a dielectric plate, characterized by determining the relative permittivity by measuring changes. 2 TE ₀₁ δ mode resonance system fixed in the case with two dielectric resonators aligned and facing each other, means for positioning the sample plate at the stopping point of the obtained electric field strength distribution, presence or absence of the sample plate 1. A device for measuring the relative dielectric constant of a dielectric plate, characterized in that it has a means for determining a change in resonance frequency due to the change in resonance frequency.