JPH01244343A - Broad-band measuring cell - Google Patents

Abstract

PURPOSE:To prevent the occurrence of errors due to machining of a sample and to perform accurate measurement, by providing electrode plates having matching structures so that the characteristic impedance of the plates become the same as that of a cable at one end of the coaxial cable. CONSTITUTION:A voltage from a signal generator 14 is applied to one end of a coaxial cable 11. A measuring instrument 15 which measures the amplitude and the phase of the reflected voltage is connected to one end of the cable 11. A main body 16 of a broad-band measuring cell is connected to the other end of the coaxial cable 11. The cell main body 16 is composed of outer conductor plates 20 and 21 and a central conductor plate 23. The outer conductor plates 20 and 21 are connected to the outer conductor of said coaxial cable 11. The central conductor plate 23 is connected to the central conductor. The characteristic impedance between each of the conductor plates 20, 21 and 23 is made to agree with that of the coaxial cable 11. In this constitution, a sample can be loaded between electrode plates without machining the shape of the sample, and the high frequency characteristics can be measured. Therefore, measuring errors due to the machining of the sample can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION One Industrial Application - The present invention relates to a broadband measurement cell for measuring the complex dielectric constant of a material using microwaves.

Background of the Invention - To measure the properties of a material using microwaves, a sample is placed in a space surrounded by a coaxial tube or waveguide conductor, and the complex dielectric constant of the sample is determined from changes in the intensity and phase of the incident signal and reflected signal. This is done by measuring high-frequency characteristics such as complex conductivity, complex magnetic permeability, etc. The measurement cell for this purpose has a structure that can create a space for placing the sample in the electric and magnetic fields of the microwave. In response to this demand, for example, as disclosed in Japanese Patent Application Laid-Open No. 62-226051, a structure has been proposed in which the length of the sample filling section is made variable.

Problems to be Solved by the Invention - In conventional cells, the filling space for the sample can be made variable, but this is limited to samples that are liquid or gas; when measuring solid samples, it is necessary to It had to be processed into a shape or turned into powder. For this reason, processing a sample into a cell shape requires a high degree of processing precision, and there is a problem in that it requires a lot of effort. On the other hand, when the sample is made into a powder, the properties in the solid state may change in conditions such as humidity and density, resulting in a problem of large measurement errors.

An object of the present invention is to provide a high-frequency measurement cell that can accurately measure broadband characteristics without processing or turning a solid sample into powder.

Means and Effects for Solving One Problem - In order to achieve the above object, the present invention provides an external conductor plate connected to a jacket conductor at one end of a coaxial cable to which a voltage is applied, and one end of the coaxial cable. and a center conductor plate connected to the center conductor and supported by matching with the coaxial cable, and detects the reflection or transmission signal of electromagnetic waves when a sample is loaded between the outer conductor plate and the center conductor plate. The structure is designed to measure the broadband characteristics of the sample, and the central conductor plate and outer conductor plate have the same characteristic impedance as a coaxial cable, and the change in impedance due to the dielectric constant of the sample loaded between the conductors is reflected or transmitted. The properties of the sample are measured by detecting changes in the rate.

One Embodiment - FIG. 1 is a perspective view of a high frequency measurement cell showing one embodiment of the present invention. A center conductor 1 is attached to one end of the coaxial cable 11.
A voltage is applied from a signal generator 14 between the conductor 2 and the jacket conductor 13, and a measuring device 15 that can measure the amplitude and phase of the reflected voltage is connected. At the other end of the coaxial cable 11,
A broadband measurement cell body 16 is connected. In this broadband measurement cell body 16, a pin 18 connected to the center conductor 12 of the coaxial cable 11 is provided through a hole in the center of a base 17 of the outer conductor, and a pin 18 connected to the center conductor 12 of the coaxial cable 11 is provided around the hole. The outer sheath conductor 13 of is connected. The base body 17 has elongated holes 19 on both sides, and the elongated holes 19 and the outer conductor plates 20, 21
The mounting structure is such that the outer conductor plates 20.21 are supported oppositely by the setscrews 22, and the outer conductor plates 20.21 can be slid toward the center. A center conductor plate 23 is attached to the tip of the center conductor 12 of the coaxial cable 11 protruding from the center of the base 17 in parallel to the outer conductor plates 20 and 21.

In this structure, a solid sample is sandwiched between the outer conductor plate 20 and the center conductor plate 23 and between the outer conductor plate 21 and the center conductor plate 23 during measurement. At this time, the cell body 16 is adjusted to have an impedance structure that matches the coaxial cable 11. That is, the outer conductor 1 of the coaxial cable 11
The center conductor plate is adjusted so that the relationship between the diameter D1 of No. 3, the gap D2 between the outer conductor plates 20. The axial position of 23 is adjusted.

The broadband measurement of the sample in this example uses the signal generator 1.
4 is applied to the broadband measurement cell body 16, and the measuring device 15 measures the intensity and phase of the wave reflected by the sample inside the cell.
The properties of the sample can be determined by measuring.

Therefore, the sample remains solid, and its shape processing and powder processing are not required, making it possible to easily measure broadband characteristics.

In the above embodiments, one of the external conductor plates 20 and 21 may be fixed, and high frequency measurement can be performed with a sample loaded on either one. Further, the cell main body and the coaxial cable may have a structure in which they can be connected and detached using a connector.

FIG. 2 shows another embodiment of the present invention, and shows a cell structure for wideband measurement that utilizes transmission of electromagnetic waves. In the figure, a high frequency measurement cell 30 is connected to a pair of external conductor plates 3.
1.32 is sandwiched between base bodies 33 and 34, and the base body 33
is connected to the signal generator 14 via a coaxial cable 35, and the measuring instrument 15 is connected to the base 34 via a coaxial cable 36.
The central conductor plate 37 connects to the coaxial cable 35 at both ends.
．． 36 center conductors.

In this structure, the outer conductor plate 31. 32 and the distance between the base 33, 34 and the center conductor plate 37 are set to values that match the characteristic impedance of the coaxial cable 35, 36. As a result, before loading the sample, the high frequency signal from the high frequency power source 14 is not reflected or attenuated by the high frequency measurement cell 30, and the coaxial cable 36
It is measured by the measuring device 15 through the sensor. When a sample is loaded into the broadband measurement cell 30 from this state, the reflectance and transmittance of the signal in the broadband measurement cell 30 change depending on the characteristics such as the dielectric constant of the sample, and the signal reaching the measuring device 15 changes. Since the intensity and phase change, the high-frequency characteristics of the sample can be measured from this change.

In this embodiment as well, as long as the sample can be loaded into the broadband measurement cell 30, it is possible to perform measurements without the need for shape processing or powder processing.

Effects of the Invention As described above, according to the present invention, since the coaxial cable has a structure in which one end has an electrode plate with a matching structure that has the same characteristic impedance as the cable, it is possible to eliminate the need for shaping the sample and to perform powder processing. It is possible to measure the high frequency characteristics by loading it between the electrode plates without having to
This has the effect of eliminating errors caused by sample processing and allowing highly accurate measurements.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the invention, and FIG. 2 is a perspective view showing another embodiment of the invention. 11... Coaxial cable, 12... Center conductor, 13...
...Sheath conductor, 14...Signal generator, 15...Measuring device, 16...Broadband measurement cell body, 20.21...
-Outer conductor plate, 23...center conductor plate.

Claims (1)

[Claims] 1) An outer conductor plate connected to the outer conductor of the coaxial cable at one end to which a voltage is applied, and a center conductor plate connected to the center conductor of the coaxial cable at one end and supported in a matching manner with the coaxial cable. A cell for broadband measurement, characterized in that the broadband characteristic of the sample is measured from reflected or transmitted signals of electromagnetic waves when the sample is loaded between the outer conductor plate and the center conductor plate.