JP5589180B2 - High frequency material constant measurement system - Google Patents

Description

  The present invention relates to a measurement system for high-frequency material constants such as high-frequency dielectric constant and high-frequency dielectric loss.

  In electronic equipment devices with higher frequencies such as electronic information equipment and mobile communication equipment, it is important to evaluate the performance of capacitors, wiring boards, etc., which are basic component materials. Typical examples of material constants related to electrical performance for high-frequency signals include dielectric constant and dielectric loss, or complex dielectric constant, and various measurement evaluation methods have been invented so far.

  The conventional methods for evaluating these material properties can be broadly divided into parallel metal plate method, waveguide method, resonator method, and free space method, and according to the characteristics of each measurement method, They are properly used according to the evaluation items (see Non-Patent Document 1). That is, in these methods, there are advantages and disadvantages and trade-offs with respect to the measurable frequency range, the accuracy requirements regarding the mechanical processing of the measurement sample, the accuracy of the measurement values obtained, and the like.

  Among the above methods, the free space method has the characteristics that the frequency range that can be measured is wide and the requirements for processing accuracy of the sample to be measured are not so strict, but the sample to be measured is irradiated with radiated electromagnetic waves. Based on the principle of measuring the intensity or polarization of the reflected or transmitted wave from the sample, the sample to be measured must be sufficiently large with respect to the measurement wavelength.

  The present invention is classified into the above-mentioned free space method having the characteristics that the shape accuracy requirement of the sample to be measured is loose and it can cope with a wide range of frequencies. The method of the present invention estimates the material constant by measuring the scattered wave from the sample to be measured, while other conventional free space methods use reflected waves, transmitted waves, or polarized waves on the sample to be measured. is there. In the method using scattered waves, the size of the sample to be measured should be 1/10 or less of the measurement wavelength (for example, 300 mm at a frequency of 1 GHz), and if the volume of the sample to be measured is given accurately, the shape of the sample to be measured The effect is characterized in that it can be corrected. Furthermore, the dielectric constant of the liquid can be easily measured by sealing it in an appropriate container, and can be applied to applications other than electronic component evaluation.

  The present invention provides a system capable of measuring dielectric constant easily and quickly without requiring precise machining of a sample to be measured over a wide range of measurement frequencies.

  Up to now, an electric field measurement method using a dielectric scattering probe has been developed for the purpose of noise measurement in an arbitrary space from a radio wave source to a distant place (see Non-Patent Document 2 and Non-Patent Document 3). This measurement method uses the unique relationship between the electric field strength at the scatterer position, the dielectric constant of the scatterer, and the scattered wave power (Takashi Komone et al., “Using a dielectric scatter sphere. Electromagnetic field measurement method ", IEICE technical report, vol.EMCJ2007, no.77, pp.135-139, 2007). Therefore, contrary to this electric field measurement, if a scattered wave is measured when a known electric field is applied to a scatterer having an unknown dielectric constant, the dielectric constant can be estimated from the above relationship. From the theoretical investigation of the above relationship and the experimental results of the scattered wave electric field measurement, the quantitative validity of the dielectric constant estimation has been clarified.

Osamu Hashimoto "Material Constant Measurement Method in High Frequency Region" Morikita Publishing 2003 A. L. Cullen and J.M. C. Parr, "A NEW PERTURBATION METHOD FOR MEASURING MICROWAVE FIELDS IN FREE SPACE," Proc. Inst. Elct. Eng. , Pt. 3, vol. B, 102, pp. 836-844, 1955 J. et al. H. RICHMOND, “A Modulated Scattering Technique for Measurement of Field Distributions,” IRE Trans. Microwave Theory and Technologies, vol. MTT-3, no. 13-5, pp. 13-15, 1955

  The present invention relates to a method for measuring basic material constants such as dielectric constants of electronic component materials and chemical materials at high frequencies. As described above, the free space method, which is one of the measurement methods for material constants, can handle a wide range of measurement frequencies, and the requirements for processing accuracy and dimensions of the sample to be measured are relatively gentle. The sample to be measured was required.

  The object of the present invention is to support a wide range of measurement frequencies, without strict requirements on the processing accuracy and dimensions of the sample to be measured, and to quickly evaluate the high-frequency dielectric constant etc. with the sample to be measured is sufficiently smaller than the measurement wavelength It is to provide a high-frequency material constant measurement system.

  In order to achieve the above object, the present invention measures a generation mechanism of a high-frequency radiated electromagnetic field having an arbitrary frequency and a scattered wave electromagnetic field scattered from a sample to be measured placed in the radiated electromagnetic field generated by the generation mechanism. An electromagnetic field receiving mechanism installed to perform the analysis, and an analysis processing unit (for example, a spectrum analyzer connected to a high frequency amplifier and a bandpass filter) that calculates a material constant from the scattered wave reception voltage output from the receiving mechanism. A high-frequency material constant measuring system is provided.

  By having a mechanism that can vary the frequency, intensity, and polarization of the electromagnetic field generated by the radiated electromagnetic field generating mechanism, it is possible to cope with a wide range of frequencies, and to compensate for the sensitivity derived from the size of the sample to be measured and the material constants. Measurement taking account of the directivity becomes possible.

  According to the present invention, the sample to be measured having a sufficiently small size compared to the measurement wavelength by measuring the scattered wave electromagnetic field scattered from the sample to be measured installed in the radiated electromagnetic field generated from the generation mechanism of the radiated electromagnetic field. The high-frequency material constant can be measured.

  In the high-frequency material constant measuring apparatus according to the present invention, the radiation electromagnetic field generation mechanism has a mechanism capable of varying the frequency and intensity of the generated electromagnetic field and the polarization, thereby allowing a wide range of measurement conditions such as a wide frequency range and anisotropy of the sample to be measured. It can respond to.

It is explanatory drawing which showed the implementation method of the high frequency material characteristic measuring system. Example 1 It is explanatory drawing which showed the implementation method of the high frequency material characteristic measuring system. (Example 2)

  The high-frequency material constant measuring system according to the present invention places a sample to be measured in an anechoic chamber or a casing that can be regarded as a free space in which an electromagnetic wave absorber or the like is installed so as not to cause internal reflection. A radiated electric field having an arbitrary frequency at which the electric field strength at the sample installation position is known is applied by the transmitting antenna.

  The sample to be measured placed in the radiated electric field generates polarization according to the material constant such as its dielectric constant, and this polarization is generated alternately in the direction of polarization of the applied electric field, so that the scattered electromagnetic field is regenerated from the sample to be measured. Radiated.

  The re-radiated scattered electromagnetic wave is received by a receiving antenna installed at a known distance where the distance from the sample to be measured is a far field at the frequency.

  In order to eliminate the effect of superimposition of the direct wave component from the transmitting antenna, the electric field component due to the received scattered wave is the square value of the received electric field when not placed from the square value of the received electric field when the sample to be measured is placed. Obtained by obtaining the square root of the reduced value.

  The obtained scattered wave reception field strength value is received from the sample when the dimension of the sample to be measured is sufficiently smaller than the length of the electromagnetic wave to be irradiated, the dielectric polarization effect term, the wavelength related term, the sample shape term, the sample field strength value, and the sample position. It is equal to the product of the reciprocal of the distance to the antenna, and the value of the dielectric polarization effect term can be found from this relationship, and the dielectric constant can be obtained from the relational expression between the dielectric constant and the dielectric polarization term.

  As described above, by applying the present invention, it is possible to measure the dielectric constant of the sample by measuring the electric field strength caused by the scattered wave from the sample to be measured.

  FIG. 1 is a layout view of an embodiment of the system of the present invention, wherein 1 is an anechoic chamber as a measurement field, 2 is a transmitting antenna, 3 is a receiving antenna, 4 is a sample to be measured, and 5 is a sample to be measured. , 6 is a signal analyzer, 7 is a high-frequency signal generator, and 8 is a radio wave absorber.

  The result of measuring the dielectric constant of pure water sealed in a non-conductive container having a radius of 40 mm as the sample 4 to be measured in the anechoic chamber 1 will be described. The anechoic chamber 1 is a CISPR international standard 3m method anechoic chamber in which electromagnetic wave absorbers are installed on the walls and ceiling other than the metal floor, and a stationary electromagnetic wave absorber is laid on the floor. And simulated free space.

  A half-wave dipole antenna was used as the transmission antenna 2 and the reception antenna 3, and a sine wave signal having a frequency of 1 GHz was applied to the transmission antenna 2 from the high-frequency signal generator 7. The receiving antenna 3 directs the minimum direction of the directivity of the dipole antenna so that the electromagnetic wave component directly transmitted from the transmitting antenna 2 is reduced, and performs electromagnetic shielding between the transmitting and receiving antennas by the radio wave absorber 8. The element centers were installed with an interval of 1.5 m.

  A high-frequency signal such that the electric field strength due to the electromagnetic wave 2 ′ emitted from the transmitting antenna at a distance of 3.1 m from the center of the antenna element on the center line of the transmitting antenna 2 and the receiving antenna 3 is 0.0095 V / m. The output of generator 7 was adjusted. An alumina sphere sample 4 having a radius of 40 mm was placed through a sample support 5 so that the center of the sphere came to this point.

  By obtaining the square root of (E1 × E1-E2 × E2) from the measured voltage value E1 by the signal analyzer 6 when the sample 4 to be measured is placed and the measured voltage value E2 when the sample 4 is not placed, the sample support 5 or the like is obtained. 81 μV / m was obtained as the electric field intensity Er at the position of the receiving antenna 3 only by the scattered electromagnetic wave 4 ′ re-radiated by the sample 4 to be measured.

  Relational expression between electric field intensity and dielectric constant due to scattered wave (Takashi Komone, “Electromagnetic field measurement technique using dielectric scattering sphere”, IEICE technical report, vol.EMCJ2007, no.77, pp.135-139 , 2007) using a distance of 3.1 m, a wavelength of 0.3 m, a radius of the sample to be measured of 40 mm, an electric field intensity of the sample position of 0.0095 V / m, and an electric field intensity of the scattered wave of 81 μV / m. The dielectric constant of the measurement sample was estimated by calculation as about 70 as the relative dielectric constant, which is the ratio to the vacuum dielectric constant.

  The relative permittivity 70 at a frequency of 1 GHz in pure water in a non-conductive container having a radius of 40 mm according to the present invention matches the standard relative permittivity value 80 of water with a difference of about 10%.

  In the embodiment of FIG. 2, the material constant is estimated by detecting the scattered electromagnetic wave 11 ′ re-radiated from the sample 11 to be measured by the broadband transmitting antenna 9 and the broadband receiving antenna 10 installed in a small anechoic box. The electromagnetic wave generated from the broadband transmitting antenna 9 has a structure that does not directly reach the broadband receiving antenna 10, and only the scattered electromagnetic wave 11 ′ can be received by the broadband receiving antenna 10. According to this structure, measurement is possible with a small device, which is useful for improving the convenience of measurement.

DESCRIPTION OF SYMBOLS 1 Electromagnetic anechoic chamber 2 Transmitting antenna 2 'Electromagnetic wave radiated | emitted from transmitting antenna 3 Receiving antenna 4 Sample to be measured 4' Scattered electromagnetic wave re-radiated from sample to be measured 5 Measured sample support 6 Signal analyzer 7 High-frequency signal generator 8 Radio wave absorber 9 Broadband transmitting antenna 10 Wideband receiving antenna 11 Sample to be measured 11 'Scattered electromagnetic wave re-radiated from sample to be measured 12 Electromagnetic anechoic box

Claims (1)

In the material constant measurement system for measuring the material constant of a dielectric sample to be measured having a dimension sufficiently smaller than the wavelength, utilizing the fact that the scattered wave intensity of the dielectric has a unique relationship with the dielectric constant,
A signal generator with variable frequency,
A transmitting antenna connected to the signal generator;
A signal analyzer;
A receiving antenna connected to the signal analyzer;
An anechoic box,
With
The anechoic box is provided when the receiving antenna, the transmitting antenna, and the measured dielectric sample are installed in the anechoic box so that the measured dielectric sample is between the receiving antenna and the transmitting antenna. The electromagnetic wave transmitted from the transmitting antenna has a shape that does not reach the receiving antenna directly,
In the anechoic box, the receiving antenna, the transmitting antenna, and the dielectric sample to be measured are respectively arranged in the above relationship, and the dielectric sample to be measured is irradiated from the transmitting antenna with the electromagnetic wave from the signal generator. A material constant measurement system, wherein a scattered wave from the dielectric sample to be measured is received by the receiving antenna, and a material constant of the dielectric sample to be measured is measured.