Magnetic permeability measuring method

Abstract

Provided is a magnetic permeability measuring method that makes it possible to highly accurately measure the magnetic permeability of a magnetic material, especially a thick film-shaped magnetic material having a relatively large film thickness. This magnetic permeability measuring method comprises: a step for measuring a measured permeability coefficient of a magnetic material using a measurement probe; a step for setting an analysis model corresponding to a measurement condition of the measuring step, and calculating a calculated permeability coefficient of the magnetic material in the analysis model and a magnetic permeability of the magnetic material corresponding to the calculated permeability coefficient by finite element analysis; a step for acquiring first sets which are a plurality of sets of the real part and the imaginary part of a magnetic permeability corresponding to the real part of the calculated permeability coefficient that matches the real part of the measured permeability coefficient; a step for acquiring second sets which are a plurality of sets of the real part and the imaginary part of a magnetic permeability corresponding to the imaginary part of the calculated permeability coefficient that matches the imaginary part of the measured permeability coefficient; and a step for determining a magnetic permeability with a matching real part and a matching imaginary part from among the first and second sets.

Description

Magnetic permeability measurement method

[0001] The present invention relates to a magnetic permeability measuring method for measuring the magnetic permeability of a magnetic material.

[0002] Currently, high-frequency applications using the GHz band, such as mobile phones and wireless communications, are becoming increasingly popular. High-frequency magnetic materials that are useful for further miniaturization and high integration of these components are highly desired, and magnetic thin films with high magnetic permeability are particularly essential for the magnetic materials used in circuits. At the same time, the establishment of a method for evaluating high-frequency magnetic permeability is becoming essential.

[0003] The present inventors have developed a magnetic permeability measurement device that does not require the effort of processing a sample. Patent documents 1 to 4 disclose probes and magnetic permeability measurement devices developed by the present inventors for measuring the magnetic permeability of magnetic materials, particularly film-like magnetic materials. The probe has a structure in which a dielectric layer is sandwiched between a strip conductor through which a high-frequency carrier signal is passed and a ground conductor, and the magnetic material to be measured is brought into contact with the conductor, and the permeability coefficient S of the magnetic material to be measured is measured. ２１ The magnetic permeability of the magnetic material is determined by measuring the

[0004] The permeability to be obtained is the complex relative permeability μ r where μ r ' is the complex relative permeability μ r The real part of μ r '' is the complex relative permeability μ r is the imaginary part of

[0005] Complex permeability μ r The real part μ of r ' corresponds to the inductance component L of the magnetic material, and the complex permeability μ r The imaginary part μ r '' is the loss (resistance component) of the magnetic material.

[0006] JP 2010-060367 A JP 2012-032165 A JP 2015-172497 A JP 2016-053569 A

[0007] On the other hand, high frequency magnetic materials such as ferrites used in high frequency bands are becoming thicker. For example, for thick magnetic materials with a thickness of 10 to 50 μm or more, a probe having a structure in which a dielectric layer is sandwiched between the above-mentioned strip conductor and ground conductor is brought into contact with the magnetic material to be measured, and the transmission coefficient S of the magnetic material to be measured is measured. ２１ In the method for measuring the magnetic field, measurement errors may occur due to demagnetizing fields.

[0008] When a thick magnetic material is excited, magnetization fluctuates in the thickness direction inside the magnetic material, generating a demagnetizing field, which does not occur in a thin-film magnetic material with a thickness of, for example, 10 μm or less. Furthermore, when a film-like magnetic material is locally excited by a linear strip conductor, a demagnetizing field is generated outside the magnetic field locally generated in the magnetic material. The influence of this demagnetizing field cancels out the magnetic flux of the excited magnetic field, resulting in an error in the actual magnetic permeability of the magnetic material being measured. More specifically, the complex relative permeability μ in the above formula (1) r The imaginary part μ r The resonant frequency in the ''' may be shifted, making it impossible to measure the magnetic permeability with high accuracy.

[0009] Fig. 14 is a graph showing an example of measurement in which an error occurs in the imaginary part of the permeability due to the influence of a demagnetizing field. Fig. 14 shows the measurement value obtained by a probe equipped with a microstrip line of an elongated conductor and the measurement value obtained by the Nicolson-Ross-Weir (NRW) method, which is a standard permeability measurement method that is not affected by a demagnetizing field. Fig. 14(a) shows the complex relative permeability μ r The imaginary part μ r 14(b) shows the value of the complex relative permeability μ r The real part μ of r The magnetic material to be measured is a NiZn ferrite film (3 mm × 3 mm × 100 μm thick), and as shown in FIG. 14(a), the complex relative permeability μ r The imaginary part μ r The resonant frequency at '' is shifted to the high frequency side by about 7 GHz, resulting in a large error in the measured value. r The real part μ of rThe measured values ​​of ' appear to be roughly in line with the values ​​measured by the NRW method, but in reality the resonant frequency should have shifted to the high frequency side in the same way, and it is possible that this is being buried in noise and making it difficult to observe.

[0010] The magnetic permeability of a magnetic material, which is a sample to be measured, is often evaluated using the standard measurement method, such as the Nicolson-Ross-Weir (NRW) method. However, this method requires the sample to be precisely machined into a doughnut shape and to be placed in a coaxial tube with precise positioning accuracy, which makes it technically difficult and time-consuming.

[0011] On the other hand, when measuring the magnetic permeability by placing a magnetic material close to a strip conductor, when measuring a thick-film magnetic material that has a large area compared to the width of the strip conductor, the ferromagnetic resonance frequency shifts and the magnetic permeability fluctuates due to the fluctuations in magnetization that occur in the thickness direction of the magnetic material due to the thick film and the influence of the demagnetizing field caused by the local application of a magnetic field, making it difficult to accurately measure the material's inherent magnetic permeability.

[0012] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for measuring magnetic permeability that can measure with high precision the magnetic permeability of a magnetic body, particularly a thick-film magnetic body having a relatively thick film thickness.

[0013] In order to achieve the above object, the magnetic permeability measurement method of the present invention for measuring the magnetic permeability of a magnetic body comprises the steps of: measuring a measured permeability coefficient of the magnetic body using a measurement probe; setting an analytical model corresponding to the measurement conditions of the measuring step, and calculating a calculated permeability coefficient of the magnetic body in the analytical model and the corresponding magnetic permeability of the magnetic body by finite element analysis; acquiring a first set of multiple pairs of real and imaginary parts of the permeability corresponding to the real part of the calculated permeability coefficient that matches the real part of the measured permeability coefficient; acquiring a second set of multiple pairs of real and imaginary parts of the permeability corresponding to the imaginary part of the calculated permeability coefficient that matches the imaginary part of the measured permeability coefficient; and determining the magnetic permeability whose real and imaginary parts match from the first and second sets.

[0014] According to the present invention, the magnetic permeability of a thick-film magnetic material can be measured easily and with high accuracy.

[0015] FIG. 1 is a diagram showing an example of a schematic configuration of a magnetic permeability measurement device according to an embodiment of the present invention. FIG. 1 is a diagram showing an example of a configuration of a probe 10. FIG. 2 is a diagram showing an analysis model by electromagnetic field analysis software of a calculation processing program. FIG. 3 is a flowchart showing a magnetic permeability measurement method according to an embodiment of the present invention. FIG. 4 is a diagram for explaining optimization processing by electromagnetic field analysis software using the finite element method. FIG. 5 is a diagram for explaining optimization processing by electromagnetic field analysis software using the finite element method. FIG. 6 is a diagram showing an example of a first measurement result of the magnetic permeability measurement method according to the present embodiment. FIG. 7 is a diagram showing an example of a first measurement result of the magnetic permeability measurement method according to the present embodiment. FIG. 8 is a diagram showing an example of a second measurement result of the magnetic permeability measurement method according to the present embodiment. FIG. 9 is a flowchart showing another processing procedure of the magnetic permeability measurement method according to an embodiment of the present invention. 21 mea and the approximated measured permeability coefficient S 21 The real part of mea, Re{S 21 10 is a graph showing an example of a portion of the imaginary part of the magnetic permeability due to the influence of a demagnetizing field.

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. However, the technical scope of the present invention is not limited to these preferred embodiments.

[0017] 1 is a diagram showing a schematic configuration example of a magnetic permeability measurement device according to an embodiment of the present invention, which is configured to include a probe 10, a network analyzer (signal measuring instrument) 20, and a processing device (e.g., a computer such as a personal computer) 30 (processing means) that executes numerical analysis processing.

[0018] The magnetic material 1 to be measured is a thick-film magnetic material having a thickness of, for example, about 10 to 50 μm. The probe 10 is placed in contact with or in the vicinity of the magnetic material 1, and is connected to a network analyzer 20 via a non-magnetic coaxial cable 3. The network analyzer 20 supplies a current signal and measures the transmission coefficient S of the magnetic material 1 to be measured. ２１ The signal data is input to a processing unit (computer) 30, and the complex permeability of the magnetic material is calculated by a predetermined numerical analysis process (including the optimization process described below). In addition, to magnetically saturate the magnetic material 1, a magnet (magnetic field application unit) consisting of, for example, a double-yoke electromagnet 40 is used.

[0019] 2A and 2B are diagrams showing an example of the configuration of the probe 10, where FIG. 2A shows the configuration of the probe 10 and FIG. 2B shows a state in which a sample is placed on the probe 10. As shown in FIG. 2A, the probe 10 includes a signal transmission line having a band-shaped strip conductor formed on the surface of a dielectric substrate and a ground conductor formed on the front or back surface of the dielectric substrate. Specifically, the probe 10 includes a microstrip conductor 11 (width = 0.4 mm), a dielectric flexible substrate (sheet) 12 (e.g., ROGERS duroid 5880, relative permittivity = 2.2, thickness = 0.127 mm), a ground conductor 14, and a pair of connectors 15 connected to both ends of the microstrip conductor 11. The probe 10 includes a microstrip line in which the dielectric flexible substrate 12 is sandwiched between the microstrip conductor 11 and the ground conductor 14.

[0020] The connector 15 connects to the signal cable 3 (Figure 1). The microstrip conductor 11 and the flexible substrate 12 are integrally fixed by chemical or thermal treatment. In the first configuration example, the flexible substrate 12 is pressed against a ground conductor 14 having a planar and curved structure. The interior of the ground conductor 14 is shown as transparent for ease of explanation, but in reality it is made of a metal material such as copper. The microstrip conductor 11 is formed by etching. The microstrip conductor 11 is composed of a central linear portion 11a and curved portions 11b on both sides. The ends of the microstrip conductor 11 are electrically connected to the connector 15. The linear portion 11a and the curved portion 11b of the microstrip conductor 11 both have a characteristic impedance matched to 50 Ω. The configuration in which the flexible substrate 12, which is a dielectric, is sandwiched between the microstrip conductor 11 and the ground conductor 14 forms a microstrip line.

[0021] As shown in FIG. 2B, the magnetic body 1 to be measured is prepared by adhering it to a planar substrate 17, and is placed by applying pressure (not shown) from above so that it is in close proximity to or in contact with the microstrip conductor 11.

[0022] The microstrip conductor 11 extends into the ground conductor 14 through an opening 14a provided in the ground conductor 14 and is connected to a connector 15 on the opposite side, and when, for example, a large-diameter magnetic body 1 and a substrate 17 are placed close to each other, measurement is possible without hitting the connector 15 or the signal cable 3 (FIG. 1) connected to it. Note that although the connector 15 is shown in FIG. 2 as being inside the ground conductor 14, the connector 15 is exposed from the ground conductor 14 and is connected to the signal cable 3.

[0023] The microstrip conductor 11 and the magnetic body 1 may be brought into direct contact with each other, or a predetermined gap may be provided between them for measurement. The gap may be formed, for example, by placing a flexible substrate between the microstrip conductor 11 and the magnetic body 1, or by applying an insulating material such as resist to a thickness of several microns. Alternatively, a gap-forming jig may be provided around the probe 10 to set the gap to a predetermined size, and the microstrip conductor 11 may be placed close to the magnetic body 1 for measurement.

[0024] The probe 10 is not limited to the microstrip line configuration shown in FIG. 2, but may be other transmission line bodies such as a coplanar line.

[0025] 1 functions as a magnetic permeability calculation means for calculating the high-frequency magnetic permeability of the magnetic body 1 by calculation, and executes a calculation program for calculating the magnetic permeability. The calculation program is a computer program for executing a magnetic permeability measurement process by calculation, which will be described later. The calculation program includes general-purpose electromagnetic field analysis software for performing finite element analysis, and the electromagnetic field analysis software may be, for example, HFSS by Ansys, Inc.

[0026] 3 is a diagram showing an analytical model based on electromagnetic field analysis software in a calculation processing program. The measurement conditions of the magnetic permeability measuring device including the configuration of the probe 10 shown in FIG. 2 are modeled, and the permeability coefficient S of the magnetic body 1 to be measured is calculated by electromagnetic field analysis simulation calculation, as will be described later. ２１ and the corresponding magnetic permeability (complex relative magnetic permeability). More specifically, the permeability coefficient S ２１ The probe 10 in Fig. 2 has a bilaterally symmetrical structure with the microstrip conductor 11 at the center, and therefore Fig. 3 shows a half model of one side of the probe 10.

[0027] The procedure for measuring magnetic permeability using the magnetic permeability measuring device according to the present embodiment will be described below.

[0028] 4 is a flowchart showing the processing steps of the magnetic permeability measurement method according to an embodiment of the present invention. The probe 10 is brought into contact with or close to the magnetic body 1 to be measured (S100). Then, it is placed in the pole gap of the double-yoke electromagnet 40, and a strong DC magnetic field (for example, about 20 kOe) is applied to saturate the magnetic body 1, and calibration is performed with the network analyzer 20 (S102). This eliminates the electrical length of the probe 10 and the coaxial cable 3, the DC impedance of the magnetic body 1, non-magnetic signals, etc. Then, the DC magnetic field is removed, and the permeability coefficient S contributed by the magnetic body 1 is measured. ２１ is measured (S104).

[0029] In the following description, the transmission coefficient S measured in S104 ２１ Measure the transmission coefficient S ２１ mea, which is the transmission coefficient S calculated by the simulation calculation of electromagnetic field analysis software based on the analysis model of FIG. ２１ Calculate the permeability coefficient S ２１ The permeability coefficient S ２１ is a complex number expressed by the following equation (2), and Re{S ２１} is the complex transmission coefficient S ２１ The real part of Im{S ２１} is the double permeability coefficient S ２１ is the imaginary part of

[0030] S ２１ =Re{S ２１} + jIm{S ２１} (2)

[0031] The measured transmission coefficient S obtained in S104 ２１ Optimization processing is performed on mea using electromagnetic field analysis software using the finite element method, and the measured transmission coefficient S ２１ The magnetic permeability corresponding to mea is calculated (S106). The optimization process using electromagnetic field analysis software using the finite element method will be described with reference to FIGS.

[0032] 5, 6 and 7 are diagrams for explaining the optimization process by the electromagnetic field analysis software using the finite element method. The optimization process (S106) by the electromagnetic field analysis software using the finite element method is performed by using the calculated transmission coefficient S ２１ Based on the relationship between cal and the corresponding (complex) magnetic permeability μ, the following steps are performed: S106-1) Measure the permeability coefficient S ２１ The real part of mea, Re{S ２１ mea) and the calculated permeability coefficient S ２１ The real part of cal, Re{S ２１ cal}, the real part μ of the permeability μ real and the imaginary part μ imag S106-2) a step of acquiring a plurality of sets C1 of measured transmission coefficients S ２１ Imaginary part of mea Im{S ２１ mea}, the calculated permeability coefficient S ２１ The imaginary part of cal, Im{S ２１ cal} corresponding to the relative permeability μ r The real part μ of r real and the imaginary part μ r imag S106-3) acquiring a plurality of sets C2 of the real part μ r real and the imaginary part μ r imag Each of these has a corresponding relative permeability μ r The measured transmission coefficient S ２１ The relative permeability μ corresponding to mea r A process of determining as follows.

[0033] Specifically, FIG. 5 shows the step of S106-1, in which the calculated permeability coefficient S is calculated by changing the magnetic permeability μ for the analytical model of FIG. ２１ The real part of cal, Re{S ２１ The values ​​of relative permeability μ r The real part μ of r real and the imaginary part μ r imag The magnetic permeability μ r(For example, μ r real =1 and μ r imag =0, μ r real =1 and μ r imag =0.5, μ r real =1 and μ r imag =1, ..., μ r real =1 and μ r imag = 3, μ r real =2 and μ r imag =0, μ r real =2 and μ r imag =0.5, ... μ r real =2 and μ r imag =3, ... μ r real =3 and μ r imag = 5, μ r real =3 and μ r imag = 6, ...) ２１ cal is calculated, and its real part Re{S ２１ In FIG. 5, the calculated real part Re{S ２１ cal} are only partially exemplified.

[0034] Calculated permeability coefficient S ２１ In the calculation of cal, the calculated transmission coefficient S ２１ The real part of cal, Re{S ２１ cal} is the real part μ of the magnetic permeability μ at which the predetermined value real and the imaginary part μ imag There are multiple sets of real numbers Re{S ２１ cal=0.9995 r The real part μ of r real and the imaginary part μ r imagA plurality of sets C1, real part Re{S ２１ cal=0.9983 r The real part μ of r real and the imaginary part μ r imag In step S106-1, the measured transmission coefficient S ２１ The real part of mea, Re{S ２１ mea}, the calculated permeability coefficient S ２１ The real part of cal, Re{S ２１ cal} corresponding to the relative permeability μ r The real part μ of r real and the imaginary part μ r imag A plurality of sets C1 of the above are obtained.

[0035] Similarly, FIG. 6 shows the step of S106-2, and for the analytical model of FIG. 3, the magnetic permeability μ r The calculated permeability coefficient S ２１ The imaginary part of cal, Im{S ２１ cal} is shown as an example. As in the step S106-1, the relative permeability μ r The real part μ of r real and the imaginary part μ r imag The relative permeability μ of a set of multiple set values ​​each within a predetermined numerical range r (For example, μ r real =1 and μ r imag =0, μ r real =1 and μ r imag =0.5, μ r real =1 and μ r imag =1, ..., μ r real =1 and μ r imag = 3, μ r real =2 and μ r imag =0, μ rreal =2 and μ r imag =0.5, ... μ r real =2 and μ r imag =3, ... μ r real =3 and μ r imag = 5, μ r real =3 and μ r imag = 6, ...) ２１ cal is calculated, and its imaginary part Im{S ２１ In FIG. 6, the calculated imaginary part Im{S ２１ cal} are only partially exemplified.

[0036] Calculated permeability coefficient S ２１ In the calculation of cal, the calculated transmission coefficient S ２１ The imaginary part of cal, Im{S ２１ cal} is a predetermined value of the relative permeability μ r The real part μ of r real and the imaginary part μ r imag There are a plurality of sets of imaginary parts (sets), and in FIG. 6, as an example, ２１ cal=0.0002 r The real part μ of r real and the imaginary part μ r imag A plurality of sets C2, imaginary part Im{S ２１ cal=0.0006 r The real part μ of r real and the imaginary part μ r imag In step S106-2, the measured transmission coefficient S ２１ Imaginary part of mea Im{S ２１ mea}, the calculated permeability coefficient S ２１ The imaginary part of cal, Im{S ２１ cal} corresponding to the relative permeability μr The real part μ of r real and the imaginary part μ r imag A plurality of sets C2 of the above are obtained.

[0037] FIG. 7 shows the step of S106-3, in which a plurality of sets C1 obtained in S106-1 and a plurality of sets C2 obtained in S106-2 are plotted, and the relative permeability μ r The measured transmission coefficient S ２１ The real part of mea, Re{S ２１ mea} and the imaginary part Im{S ２１ mea}, the relative permeability μ r The real part μ of r real and the imaginary part μ r imag Since the relative permeability μ r Measure the transmission coefficient S ２１ The relative permeability μ can be determined by the analysis model of the electromagnetic field analysis software that is not affected by the demagnetizing field. r and the calculated permeability coefficient S ２１ cal relationship, and from among multiple pairs of magnetic permeabilities, the measured permeability coefficient S ２１ By selecting a value where the real and imaginary parts of mea are the same, the measured transmission coefficient S ２１ The magnetic permeability of MEA can be measured with high accuracy.

[0038] The optimization process in S106 is performed for each frequency over a wide frequency range including high frequency bands exceeding 50 GHz, and the magnetic permeability μ is calculated for each frequency.

[0039] 8 and 9 are diagrams showing a first example of measurement results of the magnetic permeability measurement method according to this embodiment. The magnetic sample used in the first example of measurement results is a NiZn ferrite sheet having a thickness of 100 μm. FIG. 8( a ) shows the measured permeability coefficient S ２１ mea value, and Fig. 8(b) shows the relative permeability μ obtained by the conventional method that does not consider the influence of the demagnetizing field. r 9 shows the relative permeability μ obtained by optimization processing using the permeability measurement method according to this embodiment.r 8(a) is a graph showing the measured transmission coefficient S ２１ The value of the magnetic permeability μ shown in FIG. 8(b) is different from the value of mea due to the action of the demagnetizing field, especially the relative magnetic permeability μ r The resonance frequency in the imaginary part of the magnetic field is higher, causing an error in the magnetic permeability.

[0040] On the other hand, the magnetic permeability shown in FIG. 9 is found to be a value that is in considerable agreement with the value measured by the Nicolson-Ross-Weir (NRW) method, which is a standard magnetic permeability measurement method, and it is confirmed that the magnetic permeability can be measured with high accuracy.

[0041] 10 and 11 are diagrams showing a second example of measurement results of the magnetic permeability measurement method according to this embodiment. The magnetic sample used in the second example of measurement results is a CIP sheet (iron carbonyl iron powder sheet) having a thickness of 100 μm. FIG. 10(a) shows the measured permeability coefficient S ２１ 10(a) is a graph showing the value of the magnetic permeability μ obtained by a conventional method that does not take into account the influence of the demagnetizing field, and FIG. 11 is a graph showing the value of the magnetic permeability μ obtained by optimization processing using the magnetic permeability measurement method according to this embodiment. ２１ The relative permeability μ shown in FIG. 10(b) for the value of mea r The value of is determined by the action of the demagnetizing field, especially the relative permeability μ r The resonance frequency in the imaginary part of the magnetic field is higher, causing an error in the magnetic permeability.

[0042] On the other hand, the magnetic permeability shown in FIG. 11 is found to be a value that is in considerable agreement with the value measured by the Nicolson-Ross-Weir (NRW) method, which is a standard magnetic permeability measurement method, and it is confirmed that the magnetic permeability can be measured with high accuracy.

[0043] 12 is a flowchart showing another procedure of the magnetic permeability measurement method according to the embodiment of the present invention. In comparison with the procedure shown in FIG. 4, the other procedure shown in FIG. 12 has a different procedure from the procedure shown in FIG. 4 in that the measured permeability coefficient S ２１The process of S100, S102, S104 and S106 are the same as the process procedure shown in FIG. 4. In S106, the approximated measured transmission coefficient S ２１ The permeability corresponding to mea is calculated.

[0044] In the process of S105, the measured transmission coefficient S ２１ The value of mea is approximated by a ferromagnetic resonance curve expressed by the following equation (3).

[0045] S ２１ mea=m ４ -m １ ２ / {(m ２ ２ ・ω ２ ) ２ +m ３ ２ ・ω ２} １／２ (3)

[0046] Here, ω is the frequency, and m1, m2, m3, and m4 are constants.

[0047] FIG. 13 shows the measured transmission coefficient S before approximation. ２１ mea and the approximated measured permeability coefficient S ２１ Each real part of mea, Re{S ２１ mea) shown in FIG. 13. ２１ Theoretically, the measured value of mea varies along a predetermined curve as a whole depending on the frequency. In reality, however, the measured transmission coefficient S ２１ Each measured value of mea is affected by noise and the like, and the measured transmission coefficient S shown by the solid line L2 in FIG. ２１ There is a possibility that errors may occur in the calculated permeability due to this variation and deviation. ２１ The approximate curve L2 that is closest to each measured value of mea is calculated using the above formula (3), and the values ​​on the approximate curve are used as the measured transmission coefficient S ２１By using it as MEA, it is possible to eliminate variations and fluctuations in the actual measured values ​​and calculate more accurate magnetic permeability.

[0048] The above formula (3) is known to represent the ferromagnetic resonance curve of a magnetic thin film (see, for example, formula (4-29) and Figure 4-10 in Magnetic Engineering Lectures (5) Magnetic Thin Film Engineering, by Shuichi Iida, Maruzen, 1977, pp. 152-153). The measured transmission coefficient S ２１ It is appropriate to use the above formula (3) as the formula for expressing the approximate curve of mea. ２１ In order to minimize the error between the measured value of mea and the above equation (3), an approximation process is performed to determine the constants m1, m2, m3, and m4 of the above equation (3) using the known least squares method, and the measured transmission coefficient S shown by the solid line L2 in FIG. ２１ Obtain an approximate curve for mea and measure the value on this curve. ２１ mea to calculate the magnetic permeability.

[0049] The present invention is not limited to the above-described embodiments, and it goes without saying that the present invention also includes design changes within the scope of the gist, including various modifications and alterations that would be conceivable to a person with ordinary knowledge in the field of the present invention.

[0050] 1: magnetic material, 3: coaxial cable, 10: probe, 11: strip conductor, 12: dielectric (flexible substrate), 14: ground conductor, 15: connector, 20: network analyzer (signal measuring device), 30: arithmetic processing unit, 40: double yoke electromagnet

Claims

1. A magnetic permeability measurement method for measuring the magnetic permeability of a magnetic body, comprising the steps of: measuring a measured permeability coefficient of the magnetic body using a measurement probe; setting an analytical model corresponding to the measurement conditions of the measuring step, and calculating a calculated permeability coefficient of the magnetic body in the analytical model and the corresponding magnetic permeability of the magnetic body by finite element analysis; acquiring a first set which is a plurality of sets of real parts and imaginary parts of the magnetic permeability corresponding to the real part of the calculated permeability coefficient that coincides with the real part of the measured permeability coefficient; acquiring a second set which is a plurality of sets of real parts and imaginary parts of the magnetic permeability corresponding to the imaginary part of the calculated permeability coefficient that coincides with the imaginary part of the measured permeability coefficient; and determining the magnetic permeability whose real parts and imaginary parts coincide from the first set and the second set.

2. The method for measuring magnetic permeability according to claim 1, characterized in that the measurement probe comprises a signal transmission line having a band-shaped strip conductor formed on the surface of a dielectric substrate and a ground conductor formed on the surface or back surface of the dielectric substrate, and the magnetic body is brought into contact with or close to the signal transmission line, and the measured permeability coefficient of the magnetic body is measured by a signal measuring device electrically connected to the signal transmission line.

3. The magnetic permeability measuring method according to claim 2, wherein the signal transmission line is a microstrip line.

4. A method for measuring magnetic permeability as described in claim 1, characterized in that an approximation process is performed to approximate the measured transmission coefficient values ​​measured over a specified frequency range to a specified approximation curve, and a value on the approximation curve is used as the measured transmission coefficient.

5. The approximation curve is: Measured transmission coefficient = m ４ -m １ ２ / {(m ２ ２ ・ω ２ } ２ +m ３ ２ ・ω ２ } １／２ 5. The magnetic permeability measuring method according to claim 4, wherein ω is a frequency, and m1, m2, m3, and m4 are constants.

6. A measuring device for measuring the magnetic permeability of a magnetic body, comprising: a measurement probe on which a signal transmission line is formed, the magnetic body being capable of being arranged in proximity to or in contact with the signal transmission line; a magnetic field application unit for applying a magnetic field to the magnetic body; a signal measuring device for measuring a measured transmission coefficient of the magnetic body; and a calculation processing device for calculating the magnetic permeability of the magnetic body based on the measured transmission coefficient by calculation processing, wherein the calculation processing device sets an analysis model corresponding to measurement conditions of the measured transmission coefficient, and calculates the calculated transmission coefficient of the magnetic body in the analysis model and the corresponding magnetic permeability of the magnetic body by finite element method analysis, obtains a first set which is a plurality of sets of real parts and imaginary parts of the magnetic permeability corresponding to the real part of the calculated transmission coefficient which is equal to the real part of the measured transmission coefficient, obtains a second set which is a plurality of sets of real parts and imaginary parts of the magnetic permeability corresponding to the imaginary part of the calculated transmission coefficient which is equal to the imaginary part of the measured transmission coefficient, A magnetic permeability measuring device comprising: determining, from the first set and the second set, the magnetic permeability whose real parts and imaginary parts match.

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