Permeability measuring device and permeability measuring method

Abstract

The objective of the present invention is to provide a permeability measuring device capable of measuring the permeability of a relatively thick planar magnetic body with high accuracy. The permeability measuring device for measuring the permeability of a planar sample, which is a magnetic body, comprises: a probe in which two symmetrical signal transmission lines are formed extending in parallel with a predetermined gap therebetween, and in which a sample is held in the predetermined gap so as to be sandwiched by the signal transmission lines by making the plane extension direction of the sample parallel to the signal transmission lines; a signal measuring instrument for supplying the signal transmission lines with high-frequency signals that are transmitted in different directions to the signal transmission lines, and measuring the high-frequency signals for transmitting the signal transmission lines; and a calculation means for obtaining the permeability of the sample by numerical analysis on the basis of the high-frequency signals measured by the signal measuring instrument.

Description

Magnetic permeability measuring device and magnetic permeability measuring method

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

[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 permeability μ expressed by the following equation (10), where μ′ is the real part of the complex permeability μ and μ″ is the imaginary part of the complex permeability μ.

[0005]

[0006] The real part μ′ of the complex permeability μ corresponds to the inductance component L of the magnetic material, and the imaginary part μ″ of the complex permeability μ is the loss component (resistance component) of the magnetic material.

[0007] JP 2010-060367 A JP 2012-032165 A JP 2015-172497 A JP 2016-053569 A

[0008] On the other hand, high-frequency magnetic materials such as ferrites used in high-frequency bands, such as radio wave absorbing materials, are becoming thicker. For example, for thick-film magnetic materials formed in a sheet or plate shape with a thickness of about 10 to 50 μm or more, the magnetic material to be measured is brought into contact with the strip conductor part of the probe having a structure in which a dielectric layer is sandwiched between the above-mentioned strip conductor and ground conductor, and the transmission coefficient S of the magnetic material is measured. 21 In the method for measuring the magnetic field, there is a possibility that measurement errors may occur due to demagnetizing fields.

[0009] Figure 12 shows the magnetic field in the thickness direction within a relatively thick magnetic material. When a thick magnetic material is excited, the magnetization shifts in the thickness direction, which is negligible in a thin-film magnetic material of, for example, 10 μm or less, generating a demagnetizing field. 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. This demagnetizing field has the effect of canceling 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 resonant frequency of the imaginary part μ″ of the complex permeability μ in the above equation (10) may be shifted, making it impossible to measure the magnetic permeability with high accuracy.

[0010] FIG. 13 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. The graph shows measurements made using a probe equipped with a microstrip line made of a thin conductor (Meas. (Microstrip probe)) and measurements made using the Nicolson-Ross-Weir (NRW) method, a standard permeability measurement method that is not affected by demagnetizing fields. FIG. 13(a) shows the value of the imaginary part μ″ of the complex permeability μ, and FIG. 13(b) shows the value of the real part μ′ of the complex permeability μ. The magnetic material being measured is a NiZn ferrite film (3 mm × 1 mm × 100 μm thick). As shown in FIG. 13(a), the resonance frequency in the imaginary part μ″ of the complex permeability μ shifts to the higher frequency side by about 7 GHz compared to the measurement by the NRW method (Meas. (Nicolson-Ross-Weir)). There is a large error in the measured value (Meas. (microstrip probe)). The calculated value (Calc. (FEM)) of the magnetic permeability by numerical analysis processing using the finite element method (FEM) also has an error, just like the measured value. Note that the measured value (Meas. (microstrip probe)) and calculated value (Calc. (FEM)) of the real part μ' of the complex magnetic permeability μ shown in Figure 13(b) appear to be roughly in line with the measured value (Meas. (Nicolson-Ross-Weir) by the NRW method, but in reality the change point should have shifted to the high frequency side in the same way, and it may be difficult to observe because it is buried in noise.

[0011] 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 toroidal shape and to be placed in a coaxial tube with precise positioning accuracy, which makes it technically difficult and time-consuming.

[0012] 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.

[0013] Therefore, an object of the present invention is to provide a magnetic permeability measurement device and method that can measure with high accuracy the magnetic permeability of a planar magnetic material, for example, a thick-film magnetic material with a thickness of about 10 to 50 μm or more. Furthermore, the present probe is superior in principle to other methods in that it can reduce errors in the demagnetizing field due to the magnetic field component in the perpendicular direction as the sample film thickness increases.

[0014] In order to achieve the above object, the magnetic permeability measuring device of the present invention measures the magnetic permeability of a planar sample that is a magnetic material, and is characterized by comprising: two signal transmission lines that are formed symmetrically and extend parallel to each other with a predetermined distance between them; a probe that holds the sample so that the planar extension direction of the sample is parallel to the signal transmission lines between the predetermined distance so that the sample is sandwiched between the signal transmission lines; a signal measuring device that supplies high-frequency signals that transmit in mutually different directions to the signal transmission lines and measures the high-frequency signals transmitted through the signal transmission lines; and calculation processing means that determines the magnetic permeability of the sample by numerical analysis calculation processing based on the high-frequency signals measured by the signal measuring device.

[0015] Preferably, in the above configuration, the signal transmission line is a linear conductive line having a circular cross section. Preferably, in the above configuration, the probe holds the sample in a state in which the sample is in contact with the signal transmission line. Preferably, in the above configuration, the probe holds the sample in a state in which the sample is spaced from the signal transmission line. Preferably, in the above configuration, the probe holds the sample by sandwiching it between the signal transmission lines by placing a flat insulating substrate having a hole into which the sample is fitted between the signal transmission lines. Preferably, in the above configuration, the probe holds the sample by sandwiching it between the signal transmission lines by placing non-conductive linear members for sandwiching the sample on one or both sides of each of the two signal transmission lines in parallel to the signal transmission lines. Preferably, in the above configuration, the probe holds the sample by sandwiching it between the signal transmission lines by the two signal transmission lines themselves contacting both sides of the sample. Preferably, in the above configuration, the probe is covered with an electromagnetic wave shielding member.

[0016] A magnetic permeability measurement method according to the present invention is a method for measuring the magnetic permeability of a flat sample that is a magnetic material, and is characterized by comprising the steps of: placing the sample at a position between two symmetrical signal transmission lines that extend in parallel with a predetermined distance apart and that are approximately equally spaced from each other from the two signal transmission lines, with the planar extension direction of the sample parallel to the two signal transmission lines; supplying high-frequency signals to the two signal transmission lines in mutually different directions using a signal measuring instrument electrically connected to the two signal transmission lines; and measuring the signals transmitted through the signal transmission lines using the signal measuring instrument.

[0017] According to the present invention, when measuring the magnetic permeability of a relatively thick, planar magnetic body, it is possible to measure the magnetic permeability of the magnetic body so as to cancel out the demagnetizing field generated inside the magnetic body in the thickness direction, eliminating measurement errors caused by the demagnetizing field and enabling highly accurate measurement of the magnetic permeability of the magnetic body. The two parallel lines of this probe allow currents to flow in opposite directions above and below, canceling the magnetic field component in the thickness direction of the magnetic body sandwiched between them, thereby generating a magnetic field consisting almost entirely of in-plane components inside the magnetic body. Therefore, the thicker the magnetic body, the better this method is at reducing errors in the demagnetizing field caused by the magnetic field component in the perpendicular direction compared to other methods.

[0018] FIG. 1 is a diagram showing a schematic configuration example of a magnetic permeability measurement device according to an embodiment of the present invention. FIG. 2 is a diagram (perspective view) showing a first configuration example of a probe 10. FIG. 3 is a diagram (plan view and rear view) showing a first configuration example of a probe 10. FIG. 4 is a diagram showing a magnetic field simulation result of a sample 1 using a magnetic permeability measurement device according to an embodiment of the present invention. FIG. 5 is a flowchart showing a magnetic permeability measurement method according to an embodiment of the present invention. FIG. 6 is a diagram showing an example of data obtained by electromagnetic field analysis processing. r 1 is a graph showing a second configuration example of a magnetic permeability measurement device according to an embodiment of the present invention. FIG. 2 is a diagram showing a third configuration example of a magnetic permeability measurement device according to an embodiment of the present invention. FIG. 3 is a diagram showing a fourth configuration example of a magnetic permeability measurement device according to an embodiment of the present invention. FIG. 4 is a diagram showing a fifth configuration example of a magnetic permeability measurement device according to an embodiment of the present invention. FIG. 5 is a diagram showing the presence of a magnetic field component in the thickness direction inside a relatively thick magnetic body. FIG. 6 is a graph showing a measurement example in which an error occurs in the imaginary part of the magnetic permeability due to the influence of a demagnetizing field.

[0019] 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.

[0020] 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.

[0021] The sample 1 to be measured is a magnetic material having a thickness of, for example, approximately 10 to 50 μm or more, preferably a sheet-like or flat magnetic material having a thickness of 100 μm or more. The probe 10 is arranged between two parallel conductive lines (signal transmission lines) 11 as shown in FIG. 2 so as to be in contact with or in close proximity to the sample (magnetic material) 1. Specifically, as described below, the probe 10 has a parallel double-line structure in which two symmetrical signal transmission lines 11 are arranged parallel to each other with a predetermined distance between them, and the sample 1 is sandwiched between the two signal transmission lines 11. The probe 10 is connected to a network analyzer 20 via a non-magnetic coaxial cable 3. A high-frequency signal is supplied from the network analyzer 20, which serves as a high-frequency signal source (current source) and a signal measuring device, and the two signal transmission lines 11 transmit high-frequency signals in opposite directions. One of the two signal transmission lines 11 is a signal line that transmits a high-frequency signal supplied from the signal measuring instrument 20, and the other signal transmission line 11 is a ground line that transmits a return signal.

[0022] The network analyzer 20 measures the high frequency signal transmitted through the sample 1, specifically the transmission coefficient S 21 The signal data is measured, and the signal data is input into an arithmetic processing device (computer device) 30, and the complex permeability of the magnetic material is calculated by a predetermined numerical analysis process. In addition, in order to magnetically saturate the sample 1, the network analyzer 20 is calibrated using a magnet (magnetic field application unit) consisting of, for example, a double-yoke electromagnet 40.

[0023] The arithmetic processing device 30 functions as a rate calculation processing means for determining the high-frequency magnetic permeability of the sample 1, and executes a calculation processing program for calculating the magnetic permeability. The calculation processing program is a computer program that executes the magnetic permeability calculation process described below. Table data used to execute the calculation processing program is stored in the storage means of the arithmetic processing device 30. This table data is numerical data for three-dimensional electromagnetic field analysis, and specifically, is data that indicates the relationship between the inductance L and magnetic permeability μ of the magnetic body 1 to be measured, which is prepared in advance through simulation calculations using a known electromagnetic field analysis program. The calculation processing program includes general-purpose electromagnetic field analysis software that executes finite element analysis, and the electromagnetic field analysis software that can be used is, for example, Maxwell by Ansys, Inc.

[0024] 2 and 3 are diagrams showing a first configuration example of the probe 10. The probe 10 is formed by two signal transmission lines 11, both ends of which are electrically connected to connectors 15. FIG. 2 is a perspective view of the probe 10, showing a state in which a sample 1 is placed on the probe 10, and FIG. 3 is a plan (front) view (FIG. 3(a)) and a rear (back) view (FIG. 3(b)) of the probe 10 (the connector 15 is not shown). In the first configuration example of the probe 10, the probe 10 is formed with two symmetrical linear signal transmission lines 11 extending in parallel with a predetermined gap between them, and holds the planar sample 1 between the signal transmission lines 11 with the planar extension direction of the planar sample 1 parallel to the extension direction of the signal transmission lines 11.

[0025] The sample 1 is embedded in a through-hole 16a provided in an insulating substrate (e.g., a printed circuit board) 16, and the insulating substrate 16 with the sample 1 embedded therein is disposed so as to be sandwiched between two parallel signal transmission lines 11. The sample 1 is disposed in contact with the signal transmission lines 11 or in close proximity to the signal transmission lines 11 with a slight gap therebetween, preferably at positions approximately equidistant from the two signal transmission lines 11, and is held between the signal transmission lines 11.

[0026] An end of the insulating substrate 16 is joined to the connector 15 by, for example, soldering (the soldered joint is indicated by reference numeral 16b), and the two signal transmission lines 11 are electrically connected to the connector 15, which is connected to the cable 3. Of the two signal transmission lines 11, the signal transmission line 11a on the front side is connected to a signal terminal (core wire) of the connector 15 via a conductor pattern 17 on the front side of the insulating substrate 16, and the signal transmission line 11b on the back side is connected to a ground terminal of the connector 15 via a conductor pattern 18 on the back side of the insulating substrate 16. The connections of the two signal transmission lines 11 to the signal terminal and ground terminal of the connector 15 may be reversed. Alternatively, the signal transmission line 11 may be directly connected to the signal terminal and ground terminal of the connector 15 without going through the conductor patterns 17 and 18.

[0027] The two signal transmission lines 11 are, for example, elongated conductive wires (e.g., copper wires) with a circular cross section, and both lines 11 have the same dimensions and the same symmetrical shape, and are arranged close to or in contact with the sample 1 at symmetrical positions. As a result, the high-frequency signals transmitted through the signal transmission lines 11 become current signals with approximately the same amount and in opposite directions, and the current signals flowing in opposite directions across the sample 1 cancel out the magnetic field component of the thickness direction of the sample. By canceling the magnetic field component of the thickness direction of the sample, the magnetic permeability of the sample can be measured with almost no influence of magnetization fluctuations or demagnetizing fields.

[0028] Furthermore, current signals flowing in opposite directions through the two signal transmission lines 11 excite magnetic fields of directional components parallel to the plane of the sample 1 in the same direction, resulting in a configuration in which the magnetic fields of directional components parallel to the plane are reinforced, improving measurement sensitivity and S / N ratio. If the signal transmission line does not have a circular cross section but has a flat portion like a strip conductor, for example, the current will be biased toward the end of the flat portion, resulting in an uneven current distribution and a bias in the magnetic field distribution, which may leave the effect of a demagnetizing field. Therefore, it is preferable that the signal transmission line 11 be a conductor with a circular cross section.

[0029] 4 is a diagram showing the results of a magnetic field simulation of sample 1 using a magnetic permeability measurement device according to an embodiment of the present invention. As described above, the magnetic field components in the thickness direction of sample 1 are canceled out by the signal transmission lines 11 arranged symmetrically above and below sample 1, and only the component parallel to the in-plane direction of sample 1 is excited. Since the component in the thickness direction of sample 1 is hardly excited, measurement errors are reduced without being affected by demagnetizing fields, enabling accurate magnetic permeability measurement.

[0030] 5 is a flowchart showing the steps of a method for measuring magnetic permeability according to an embodiment of the present invention. In FIG. 5, the sample 1 is placed in contact with or close to the two signal transmission lines 11 of the probe 10 so as to be sandwiched between them (S100). The sample 1 is then placed in an electromagnetic coil (magnetic field application unit) 40, and a strong DC magnetic field (e.g., approximately 20 kOe) is applied to magnetically saturate the sample 1, and the network analyzer 20 is calibrated (S102). This eliminates the electrical length of the probe 10 and coaxial cable 3, the DC impedance of the sample, non-magnetic signals, and the like. This calibration enables measurements based on a state in which a predetermined magnetic field is applied to the device under test.

[0031] After that, the DC magnetic field is removed, and the transmission coefficient S 21 After the calibration by applying a magnetic field sufficient to cause magnetic saturation, the application of the magnetic field is stopped and the transmission coefficient S 21 By measuring the transmission coefficient S of only the contribution of sample 1, 21 can be measured.

[0032] The measured permeability coefficient S 21 Based on this, the magnetic permeability is calculated by the following calculation process (S106). The calculation process for calculating the magnetic permeability is, for example, as follows.

[0033] (a1) A known electromagnetic field analysis process (for example, finite element analysis) is performed on the sample to be evaluated using the computer device 30, and the relationship between the magnetic permeability and inductance of the sample is obtained as table data.

[0034] 6A and 6B are diagrams showing examples of data obtained by electromagnetic field analysis processing, in which FIG. 6A shows an example of a screen of the computer device 30 showing a magnetic field analysis diagram of the sample, and FIG. 6B shows the magnetic permeability μ (relative magnetic permeability μ r This is an example of table data showing the relationship between the magnetic permeability μ and inductance. By using the finite element method analysis process, the inductance L when the magnetic permeability μ is changed can be calculated using Maxwell's equations. r Table data showing the relationship between the inductance and the capacitance is stored in advance in the storage means of the computer device 30. The example of measurement results shown in the figure is data obtained by the inventors' measurement work, and the sample used as the measurement target is a NiZn ferrite resin composite sheet (magnetic material).

[0035] (a2) The transmission coefficient S measured in step S104 21 is converted into impedance Z using the following equation (1).

[0036]

[0037] Here, the characteristic impedance Z0=50Ω.

[0038] (a3) The obtained impedance Z is converted into inductance L using the following equation (2).

[0039]

[0040] (a4) From the table data showing the relationship between magnetic permeability and inductance obtained by electromagnetic field analysis, the magnetic permeability (complex relative magnetic permeability) μ corresponding to the calculated inductance L r Ask for.

[0041] FIG. 7 shows the complex relative permeability μ obtained by the processing in step S106. r 1 is a graph showing the complex relative permeability μ of Sample 1. r As described above, is expressed by the following equation (3), and μ r ' is the real part of the complex relative permeability, μ r '' is the imaginary part of the complex relative permeability.

[0042]

[0043] The real part μ of the complex relative permeability obtained by measurement with the permeability measuring device in this embodiment r ' and the imaginary part of the complex relative permeability μ r The results obtained by measuring the magnetic permeability using the Nicolson-Ross-Weir (NRW) method (shown as thin lines), a standard method of measuring magnetic permeability that is not affected by demagnetizing fields, are generally consistent with those obtained by measuring the magnetic permeability using the Nicolson-Ross-Weir (NRW) method (shown as thin lines), which is a standard method of measuring magnetic permeability that is not affected by demagnetizing fields (they are shown as almost overlapping). The magnetic permeability measuring device of this embodiment eliminates measurement errors caused by demagnetizing fields and can accurately measure the magnetic permeability of sample 1 over a wide frequency band from low frequencies to over 10 GHz.

[0044] 8 is a diagram showing a second configuration example of a magnetic permeability measurement device according to an embodiment of the present invention. The second configuration example differs from the first configuration example in that the means for holding the sample 1 is different. In the second configuration example, instead of the insulating substrate 16 in the first configuration example, linear members 12 for holding the sample 1 are provided on both the front and back surfaces of the sample 1, spanning between the connectors 15 on both sides of the signal transmission line 11. The linear members 12 are non-conductive members and are joined to the ends of the connectors 15 on both sides. The sample 1 is inserted between the linear members 12 on the front and back sides so that the sample 1 is placed between the signal transmission line 11 and held by the linear members 12 on both sides. In the example of FIG. 8 , the linear members 12 are provided on both the front and back surfaces of the sample 1 so as to span between the connectors 15 on both sides of the signal transmission line 11, but the linear members 12 may also be arranged on at least one side of the signal transmission line 11 on both the front and back surfaces of the sample 1 so as to span between the connectors 15.

[0045] 9 is a diagram showing a third configuration example of a magnetic permeability measurement device according to an embodiment of the present invention. In comparison with the second configuration example, the third configuration example omits the linear member 12 and uses the signal transmission line 11 itself to hold the sample 1. By inserting the sample 1 between two signal transmission lines 11 in a manner that allows them to come into contact with each other, the sample 1 is placed between the signal transmission lines 11 and is sandwiched between the signal transmission lines 11. When the sample 1 is a relatively thick, plate-like body that is difficult to deform, the sample 1 can be held by sandwiching it between a pair of signal transmission lines 11.

[0046] 10 is a diagram showing a fourth configuration example of a magnetic permeability measurement device according to an embodiment of the present invention. In the fourth configuration example, in addition to the first configuration example, the probe 10 is covered with an electromagnetic wave shielding member 14. By covering the probe 10 with an electromagnetic wave shielding member, interaction with the electromagnetic field from surrounding magnets and the like is blocked, improving the S / N ratio and reducing noise, enabling measurements with good sensitivity. The configuration in which the probe is covered with an electromagnetic wave shielding member may be applied to the second configuration example of FIG. 8 and the third configuration example of FIG. 9 described above.

[0047] 11 is a diagram showing a fifth configuration example of a magnetic permeability measurement device according to an embodiment of the present invention. In the fifth configuration example, in addition to the first to fourth configuration examples, the sample 1 sandwiched between two signal transmission lines 11 is surrounded by a conductive thin plate 19 along the entire periphery in the longitudinal direction of the signal transmission lines 11. The conductive thin plate 19 is an easily deformable metal plate, preferably made of copper foil. The conductive thin plate 19 is wound around the two signal transmission lines 11 so as to be spaced apart from one signal transmission line 11a, which is a signal line through which a high-frequency signal supplied from a signal measuring instrument 20 is transmitted, and to be in contact with the other signal transmission line 11b, which is a ground line through which a return signal is transmitted.

[0048] When the frequency of a high-frequency signal transmitted through the signal transmission line 11 is relatively low, the electric and magnetic fields generated by the high-frequency signal are distributed independently, and the electromagnetic field is generated locally between the two transmission lines 11. However, as the frequency increases (e.g., 10 GHz or higher), electromagnetic waves begin to be emitted to the outside. In other words, the signal transmission line 11 acts as an antenna radiating electromagnetic waves to the outside, which can lead to measurement errors due to energy loss caused by electromagnetic radiation. To suppress this electromagnetic radiation, the two signal lines 11 sandwiching the sample are surrounded by conductive thin plates 19, thereby suppressing energy loss due to electromagnetic radiation.

[0049] The conductive thin plate 19 is wrapped around the entire longitudinal periphery of the signal transmission line 11 sandwiching the sample 1, and as described above, is disposed so as to be spaced apart from the signal transmission line 11a, which is the signal line, and so as to be in contact with the signal transmission line 11b, which is the ground line. This causes the current flowing through the ground line to flow over the entire periphery, adjusting the overall characteristic impedance to 50Ω and thereby suppressing electromagnetic wave radiation.

[0050] 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.

[0051] 1: magnetic material, 3: coaxial cable, 10: probe, 11: signal transmission line, 12: linear member, 14: electromagnetic wave shielding member, 15: connector, 16: insulating substrate, 16a: through-hole portion, 17: conductor pattern, 18: conductor pattern, 19: conductive thin plate, 20: network analyzer (signal measuring device), 30: arithmetic processing device, 40: double-yoke electromagnet

Claims

1. A magnetic permeability measuring device for measuring the magnetic permeability of a planar sample that is a magnetic material, comprising: two symmetrical signal transmission lines extending parallel to each other with a predetermined gap between them; a probe that holds the sample so that the planar extension direction of the sample is parallel to the signal transmission lines between the predetermined gaps so that the sample is sandwiched between the signal transmission lines; a signal measuring device that supplies high-frequency signals that transmit in mutually different directions to the signal transmission lines and measures the high-frequency signals transmitted through the signal transmission lines; and calculation processing means that determines the magnetic permeability of the sample by numerical analysis calculation processing based on the high-frequency signals measured by the signal measuring device.

2. The magnetic permeability measuring device according to claim 1, wherein the signal transmission line is a linear conductive wire having a circular cross section.

3. The magnetic permeability measuring device according to claim 1, wherein the probe holds the sample in a state where the sample is in contact with the signal transmission line.

4. The magnetic permeability measuring device according to claim 1, wherein the probe holds the sample in a state where the sample is spaced apart from the signal transmission line.

5. The magnetic permeability measuring device according to claim 1, characterized in that the probe has a flat insulating substrate having a hole into which the sample is fitted, which is placed between the signal transmission lines, thereby sandwiching and holding the sample between the signal transmission lines.

6. The magnetic permeability measuring device according to claim 1, characterized in that the probe has non-conductive linear members for holding the sample arranged parallel to the signal transmission lines on one or both sides of each of the two signal transmission lines, thereby sandwiching and holding the sample between the signal transmission lines.

7. A magnetic permeability measuring device according to claim 1, characterized in that the probe holds the sample by sandwiching the sample with the two signal transmission lines themselves in contact with both sides of the sample.

8. The magnetic permeability measuring device according to claim 1, wherein the probe is covered with an electromagnetic wave shielding material.

9. A magnetic permeability measuring device as described in claim 1, characterized in that the sample sandwiched between the two signal transmission lines is surrounded by a conductive thin plate all around the longitudinal direction of the signal transmission lines, and the conductive thin plate is positioned so as to be spaced apart from one of the two signal transmission lines and in contact with the other signal transmission line.

10. A method for measuring the magnetic permeability of a flat sample that is a magnetic material, comprising the steps of: placing the sample at a position between two symmetrical signal transmission lines that extend in parallel at a predetermined interval and are spaced apart from each other and that are approximately equally spaced from each other from the two signal transmission lines, with the planar extension direction of the sample parallel to the two signal transmission lines; supplying high-frequency signals to the two signal transmission lines in mutually different directions using a signal measuring instrument that is electrically connected to the two signal transmission lines; and measuring the signals transmitted through the signal transmission lines using the signal measuring instrument.

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