JPH0356866A - Method and instrument for measuring dielectric material constant - Google Patents

Abstract

PURPOSE:To obtain a compact and inexpensive measuring instrument of the dielectric material constant by constitution an oscillation circuit having a dielectric resonator using a dielectric sample, thereby measuring the change of oscillation frequency. CONSTITUTION:At the center part of a sealed case having a bottom plate and a lid and a cylindrical part 50 as a side wall, the hollow cylindrical dielectric sample 16 is fixed and exhausted, and the dielectric resonator 12 is constituted. And a coaxial cable 56, a directional coupler, 40, an LPF 41, an amplifier 42, and a coaxial cable 57 are worked as a regular feed back circuit for the resona tor 12, and the oscillation circuit is constituted. In the case of measuring the constant, the high frequency signal of a specific frequency generated by a signal oscillator 46 is poured into the resonator 12 through the high-power amplifier 47, Qe adjusting mechanism 48 and a connector 36 and the sample 16 is heated, and the oscillation frequency is measured with a frequency counter 43. In such a manner, an expensive network analyzer is eliminated, and the instrument is constituted in compact and inexpensively.

Description

DETAILED DESCRIPTION OF THE INVENTION (ai Industrial Application Field) This invention relates to a method and apparatus for measuring dielectric material constants, and more particularly to a method and apparatus for measuring temperature characteristics of a dielectric sample.

(b) Conventional technology A dielectric sample is placed inside a shield case, TEOI,
, (generally n-1) or TEo1δ mode, then place the case in a thermostatic oven and heat it to bring it close to a thermal equilibrium state, then measure the resonance frequency again. A method of measuring its temperature characteristics is known.

However, the method using a constant temperature bath not only increases the size of the apparatus, but also requires a long time for the dielectric sample to rise to a predetermined temperature and reach an equilibrium state.

Therefore, the applicant of the present application published in Japanese Patent Laid-Open No. 62-211566 a method and apparatus for measuring dielectric material constants, which solves the above conventional problems by directly heating a dielectric sample with high frequency. There is.

Examples of the above-mentioned application will now be briefly described.

FIG. 3 is a schematic diagram of the device. In the figure, 14 is a cylindrical shield case with a bottom, and this shield case 1
A hollow cylindrical dielectric sample 16 is fixed approximately at the center of the inside of the sample 4 by a support rod l8. Further, an input connector 30 and an output connector 32 are attached to the side wall of the shield case 14 at opposing positions, and each is provided with coupling means such as a coupling loop. A network analyzer 34 is connected between the input connector 30 and the output connector 32. Furthermore, another connector 36 is attached to the side wall of the seal case l4, and this connector 36 is also provided with coupling means such as a coupling loop. A high-frequency injection device 38 for heating is connected to this Kofuctor 36 .

In such a measuring device, the heating high frequency injection device 3
8 injects high frequency power into the dielectric resonator 12. As a result, the dielectric sample 16 is heated with high frequency. On the other hand, the independent work analyzer 34 measures the resonance frequency of the dielectric resonator 12 coupled between the connectors 30 and 32.

By measuring the resonance frequency when the dielectric sample 16 is at a predetermined temperature in this manner, the temperature characteristics of the dielectric sample can be determined.

(Problem to be solved by the Cl invention)However, in the above-mentioned example of the method and measuring device for measuring dielectric material constants using high-frequency heating, a very expensive network analyzer is required to measure the resonant frequency of the electromagnetic resonator. The purpose of this invention is to solve the above-mentioned conventional problem by making it possible to measure the resonant frequency of a dielectric resonator without using an expensive general network analyzer. It is an object of the present invention to provide a method and a measuring device for measuring dielectric material constants that solve the problems.

f [1) Means for Solving the Problems The method for measuring dielectric material constants of the present invention involves arranging a dielectric sample in a shield case and providing a plurality of coupling means for human output of signals. A positive feedback circuit including an amplifier circuit is connected between the coupling means for signal input and the coupling means for signal output to constitute an oscillation circuit together with the electromagnetic body resonator, and a high frequency is transmitted to the specific coupling means. The method is characterized in that a change in the oscillation frequency of the oscillation circuit is measured by injecting power to heat the dielectric sample, and a predetermined material constant of the electroelectric body sample is determined from the change in the oscillation frequency.

Further, the dielectric material grain constant measuring device of the present invention includes a dielectric resonator in which a dielectric sample is placed in a shield case, and a plurality of coupling means for signal input/output are provided, and a coupling means for signal input. a positive feedback circuit including an amplifier circuit, which is connected between the signal output coupling means and the dielectric resonator to form an oscillation circuit, and a frequency measurement means for measuring the oscillation frequency of the oscillation circuit; a high-frequency power injection means for heating the dielectric sample by injecting high-frequency power into the means, and determining a predetermined material constant of the dielectric sample from the oscillation frequencies before and after the dielectric sample is heated. It is characterized by

In the method and apparatus for measuring dielectric material constants according to the present invention, a dielectric sample is placed in a shield case, and a plurality of coupling means for inputting and outputting signals are provided. The vessel is constructed. A positive feedback circuit including an amplifier circuit is connected between the signal input section and the signal output section of the coupling means, and an oscillation circuit is configured together with the lecture body resonator. The coupling means of the signal input section and the signal output section are selected to couple to a predetermined mode, and the loop length is an integral multiple of the wavelength at the oscillation frequency so that the positive feedback circuit also oscillates in the predetermined mode. To be elected. Therefore, this positive feedback circuit causes the dielectric resonator to resonate in a predetermined mode. The frequency measuring means measures the oscillation frequency of the oscillation circuit, that is, the resonant frequency of the dielectric resonator. On the other hand, the high frequency power injection means injects high frequency power into the specific coupling means. As a result, a high-frequency electromagnetic field is applied to the dielectric sample, and the dielectric sample is heated using the principle of induction heating. In this way, predetermined material constants such as the salinity coefficient of the resonant frequency of the dielectric sample can be determined from the change in the oscillation frequency of the oscillation circuit, that is, the resonant frequency of the dielectric resonator, before and after heating the dielectric sample.

(f) Embodiment FIG. 1 is a configuration diagram of the measuring device used in this invention, and FIG.
Figures (A) and (B) are longitudinal cross-sectional views of a dielectric resonator used in a measuring device. In FIG. 1, 12 is a dielectric resonator, and the figure shows a schematic cross section thereof. The dielectric resonator 2 includes a shield case made of a conductive material such as aluminum or an alloy thereof.

This shield case has a cylindrical part 50 as a side wall, a bottom plate 51 attached to the lower part, and a lid 52 covering the upper part. Note that this shield case may be one in which a shield electrode is formed on a dielectric material such as ceramic material.

As shown in FIGS. 2(A) and 2(B), a hollow cylindrical dielectric sample 16 is mounted inside the shield case by a cylindrical support 53 made of a dielectric material with a low dielectric constant, such as forsterite. ! By placing the dielectric sample 16 in place, the dielectric sample 16 is fixed approximately at the center of the shield case. Connectors 30 and 32 are provided on the side wall 50, which constitutes a part of the shield case, at two positions at the center height of the dielectric sample 16, as shown in FIG. 2(A). Each of these connectors has a coupling lube 3 between the central soul body and ground.
0a and 32a are provided. Furthermore, as shown in FIGS. 1 and 2(B), connectors 36 are provided at other positions on the side wall 50 at a height different from the center height of the dielectric sample 16. A coupling lube 36a is provided between the center conductor of this connector 36 and ground. Furthermore, a window 54 for measuring the temperature of the dielectric sample and an exhaust hole 55 for evacuation are provided at other locations on the side wall 50. The vacuum evacuation device 49 evacuates the inside of the shield case to prevent heat leakage to the outside due to air convection and heat conduction, and also evacuates the lid 52 at a constant pressure with respect to the shield case consisting of the side wall 50 and the bottom plate 51. It is for adsorption.

A measuring device is constructed by connecting various circuit devices described below to the dielectric resonator constructed as described above. Directional coupler 40 distributes signals from connector 32 and coaxial cable 56 and supplies them to frequency counter 43 and low-pass filter 41, respectively. The low-pass filter 41 filters the frequency at which the dielectric resonator 12 oscillates in the TEo+δ mode, and cuts out some of the frequencies at which the dielectric resonator 12 oscillates in other higher-order modes. The amplifier 42 amplifies the output signal of the low-pass filter 41 and applies the signal to the dielectric resonator 12 via the coaxial cable 57, coaxial connector 30, and coupling loop 30a. Said coaxial cable 56. The directional coupler 40, the low-pass filter 41, the amplifier 42, and the coaxial cable 57 are operated as a positive feedback circuit for the dielectric resonator 12. That is, the line length is set so that the phase difference caused by this positive feedback circuit is an integral multiple of the wavelength at the resonant frequency of the T E o l δ mode. Therefore, the oscillation circuit consisting of the dielectric resonator 12 and the positive feedback circuit oscillates at the resonant frequency of the dielectric resonator 12. A frequency counter 43 measures the oscillation frequency of this oscillation circuit.

The temperature sensor 44 is composed of, for example, a radiation thermometer, and measures the radiation heat of the dielectric sample 16 through the window portion 54 of the electric field resonator. The signal generator 46 generates a specific frequency signal given from the control device 45. The high power amplifier 47 amplifies the power of the signal. The Qe adjustment mechanism 48 adjusts the external Q (Qe) of the coupling loop 36a and injects the output of the high power amplifier 47 into the dielectric resonator 12 via the connector 36. At this time, since the coupling lube 36a was provided at a position slightly offset from the center height of the dielectric sample, as shown in FIG. 2(B), the TE. ,. It joins the electromagnetic field of the δ mode, thereby causing the dielectric sample l6 to generate heat.

As shown in the figure, in the TEQI1+δ mode, the electromagnetic field density is approximately 0 at the center height position of the dielectric sample, so as shown in Figure 2 (
Signal output coupling loop 3 of the frequency measurement system shown in A)
It does not bind to 0a and 32a. Therefore, the oscillation circuit is not affected.

The control device 45 shown in FIG. 1 is composed of a personal computer or the like, reads the measurement results of the frequency counter 43 and the temperature sensor 44, and controls the signal generator 46.

By the way, the no-load Q (Qo) of the dielectric resonator 12 including the dielectric sample 16 is given by the following equation.

1/low o-(1/Qj+) + (1/Qaz)
+ (1/Qc) Here, Qdl is QO regarding the dielectric loss of the dielectric sample, 2 is Q regarding the reading loss of the support 53, and Oc is Q regarding the Joule loss of the shielding case. When injecting high-frequency power into a dielectric resonator 12 like the one shown in FIG. Most of the high frequency power generated by the dielectric resonator■
Absorbed by 2. At this time, reflection from the dielectric resonator (coupling loop) is minimized by matching the frequency of the signal output by the signal generator 46 to the resonant frequency of the electrostatic resonator l2. As a result, the dielectric sample 16 is heated and generates heat at a ratio of Qo/Q■ of the high frequency power injected into the dielectric resonator. This increases the temperature of the dielectric sample 16.

Generally, the temperature coefficient winding of the frequency of a dielectric sample, τ, is given by the following equation. τf = (1/f1) (f2 - fl)/(T2 - T
I) Here, T1 is the temperature before heating, T2 is the temperature after heating,
fl is the resonant frequency at temperature T1, and f2 is the resonant frequency at temperature T2.

That is, by measuring the resonant frequency of the dielectric resonator at two temperatures, the temperature coefficient of the frequency of the dielectric sample can be determined. Specifically, control '4B device 4
5 is the temperature T of the dielectric sample before heating by the temperature sensor 44.
1 and read the resonance frequency f1 at that time using the frequency counter 43. Thereafter, a control signal is generated to the signal generator 46 to TEo++. Generate a signal with a frequency equal to the resonant frequency of the δ mode. As a result, the dielectric sample 16 is heated with high frequency. Temperature sensor 44
Based on the measured value f2 of the frequency counter 43, when the temperature of the dielectric sample l6 reaches a predetermined value T2 and is in an equilibrium state, the measured value f2 of the frequency counter 43 is read. Strictly speaking, the resonant frequency of the dielectric resonator changes as the temperature of the dielectric sample 16 increases. Therefore, even during the heating period of the dielectric sample 16, the control device 45 reads the measurement results of the frequency counter 43, TE0,,,
The signal generator 46 is controlled to inject high frequency power having a frequency equal to the resonance frequency of the δ mode.

In the above example, the temperature coefficient of frequency of the dielectric sample 16 was measured. For example, by measuring the linear expansion coefficient of the dielectric sample in advance using another measuring means, the temperature coefficient of the dielectric constant of the dielectric sample can be determined from the temperature coefficient of frequency.

Ig) Effects of the Invention According to the present invention, an oscillation circuit is constructed by connecting a positive feedback circuit to a dielectric resonator formed by disposing a dielectric sample in a shield case, so that the oscillation of the oscillation circuit is suppressed. By measuring the frequency, it becomes possible to measure the resonant frequency of the dielectric resonator. Therefore, the expensive network analyzer that has been used in the past becomes unnecessary, and the entire measuring device can be constructed in a small size and at low cost.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention. Figures 2 (A) and (B) are longitudinal cross-sectional views of the dielectric resonator used in the device shown in Figure 1, where (A) is the mode in the frequency measurement system and (B) is the mode in the heating system. are shown respectively. FIG. 3 is a schematic block diagram of a conventional measuring device. 12 16 30 32 30 36 36 50 51 52 53 - Dielectric resonator, one dielectric sample, signal input connector, signal output connector, a, 32a one coupling loop, one high frequency power injection connector, a one coupling loop , side walls, bottom plate, lid, and one support. Figure 2 (A) Figure 2 (B) 36a Figure 3 734 ゝ38

Claims (2)

[Claims] (1) A dielectric resonator is constructed by arranging a dielectric sample in a shield case and providing multiple coupling means for signal input/output, and amplification is performed between the signal input coupling means and the signal output coupling means. A positive feedback circuit including a circuit is connected to form an oscillation circuit together with the dielectric resonator, and the oscillation frequency of the oscillation circuit is changed by injecting high frequency power into a specific coupling means and heating the dielectric sample. A method for measuring a dielectric material constant, characterized in that a predetermined material constant of the dielectric sample is determined from a change in the oscillation frequency. (2) A dielectric resonator in which a dielectric sample is disposed in a shield case and is provided with a plurality of coupling means for signal input/output, and a dielectric resonator connected between the coupling means for signal input and the coupling means for signal output, A positive feedback circuit including an amplifier circuit that constitutes an oscillation circuit together with a dielectric resonator, a frequency measuring means for measuring the oscillation frequency of the oscillation circuit, and a specific coupling means for injecting high frequency power into the dielectric sample. 1. A dielectric material constant measuring device, comprising: heating high-frequency power injection means, and determining a predetermined material constant of a dielectric sample from oscillation frequencies before and after the dielectric sample is heated.