JP3398901B2 - Permeability measurement method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic permeability measuring method .

[0002]

2. Description of the Related Art Conventionally, as a method for measuring the magnetic permeability of a magnetic material at several MHz to 100 MHz, a method utilizing the magneto-optical effect (A. Thompson and H. Chang, Phys. Status S.
olii., 17, 83 ('66)) and a method using a figure-8 coil (PA Calcagno and DA Thompson, Rev. Sci., Ins.
trum., 46, 904 ('75)) is known. However, the method utilizing the magneto-optical effect has a drawback in that the magnetic permeability of the entire sample cannot be measured because the movement of the magnetization on the surface of the magnetic body is observed. Further, in this method, the measurement system resonates in the high frequency band, and therefore 100 MHz is the upper limit of measurement. On the other hand, in the 8-shaped coil method, since the entire sample is contained in the sample coil, the magnetic permeability of the entire sample can be measured. However, this method also
Since the measurement system resonates in the high frequency band, 100 MHz
Is the upper limit of measurement. As described above, the magnetic permeability of the magnetic material cannot be measured in the high frequency band of 100 MHz or higher by the conventional method.

The present invention has been proposed in order to improve the above-mentioned drawbacks, and its object is that the magnetic permeability cannot be measured in a high frequency band of 100 MHz or more in the conventional magnetic permeability measuring device and magnetic permeability measuring method. Solved, 100MH
measuring permeability to allow permeability measured at more high frequency band z
To provide a law .

[0004]

In order to achieve the above-mentioned object, the present invention is designed so that a magnetic body makes a round around the conductor or directly sandwiches the conductor on the surface of the conductor or via a non-magnetic body. In a measurement system composed of an arranged line and a ground conductor arranged so as to be electrically insulated from the line, a reflection coefficient S ₁₁ at one end, a reflection coefficient S _{22 at the} other end, and one end to the other end Up to the transmission coefficient S ₂₁ of the magnetic material in the line
If the square of the absorption coefficient due to is smaller than 1
For the case where the comparison is sufficiently large magnetic field to the magnetic anisotropy field of the magnetic material such as a degree can be regarded not applied to the case of externally applied to said line, by measuring, determining the permeability of the magnetic body The method of measuring magnetic permeability is characterized by the gist of the invention. In the present invention,
The magnetic permeability of the magnetic material is L (0) = (1- [S ₁₁ (0)] ² ) (1- [S ₂₂ (0)] ² ) / [S ₂₁ (0)] ² L (H) = (1- [S ₁₁ (H)] ² ) (1- [S ₂₂ (H)] ² ) / [S ₂₁ (H)] ² [A _m (0)] ² = 1-L (H) / L (0) μr ″ ∝ [A _m (0)] ² / f is characterized by using four formulas.
In the above four formulas, S ₁₁ (H): reflection coefficient at one end of the measurement system when a sufficiently large magnetic field is applied to the line from the outside, S ₂₂ (H): line The reflection coefficient at the other end of the measurement system when a magnetic field that is sufficiently larger than the anisotropic magnetic field of the magnetic substance is applied from the outside, S ₂₁ (H): A magnetic field that is sufficiently large compared to the anisotropic magnetic field of the magnetic substance on the line. From one end to the other end of the measurement system when S is applied from outside, S ₁₁ (0): Reflection coefficient at one end of the measurement system when no magnetic field is applied to the line from outside, S ₂₂ (0): Line Reflection coefficient at the other end of the measurement system when no magnetic field is applied from the outside, S ₂₁ (0): Transmission coefficient from one end to the other end of the measurement system when no magnetic field is applied to the line, μr ″: Magnetic The relative magnetic permeability of the body is μr = μr′−j · μr ″
The imaginary part of the relative magnetic permeability, where (-1) ^1/2 =
j, f: the frequencies at which the reflection coefficients and the transmission coefficients are measured . Further, the present invention is characterized in that the magnetic body has a strip shape. Further, according to the present invention, the line and the ground conductor are arranged so as to be electrically insulated from each other through a dielectric, air, or vacuum. Further, the present invention is characterized in that the measurement system has any structure of a microstrip type, a triplate type, a parallel line type, a coplanar type, or a coaxial type. The component structure and the measuring principle are different from those of the conventional magnetic permeability measuring device and magnetic permeability measuring method.

[0005]

According to the present invention, since the measurement system does not resonate because the transmission line is used, the magnetic permeability can be measured even in a high frequency band of 100 MHz or more.

[0006]

EXAMPLES Next, examples of the present invention will be described. Figure 1
FIG. 3 is a diagram showing an example of line 1 of the present invention, in which the magnetic substance 2
Is in the shape of a strip, and the magnetic body 2 is arranged around the conductor 3 on the surface of the conductor 3 with a non-magnetic body 4 interposed therebetween. FIG. 2 is a view showing another embodiment of the line 1 of the present invention, in which the magnetic body 2 has a strip shape, and the magnetic body 2 is arranged on the surface of the conductor 3 with the non-magnetic body 4 interposed therebetween so as to sandwich the conductor 3. Form a structure. Here, in order to avoid the influence of the demagnetizing field, the shape of the magnetic body 2 is a strip shape. Further, in FIG. 1, the magnetic body 2 is arranged so as to surround the conductor 3 once to form a closed magnetic circuit structure, thereby preventing magnetic flux leakage. In this sense, the structure of FIG. 1 enables more accurate measurement than the structure of FIG. The same effect can be obtained by removing the non-magnetic body 4 and disposing the magnetic body 2 directly on the surface of the conductor 3.

FIG. 3 is a diagram showing an embodiment of the magnetic permeability measuring apparatus of the present invention, in which 1 is a line, 2 is a magnetic body, 3 is a conductor, 5 is a ground conductor, and 6 is a dielectric. The line 1 and the ground conductor 5 are electrically insulated via the dielectric 6. Figure 4
3A is a cross-sectional view of FIG. 3, in which 1 is a line, 5 is a ground conductor, and 6 is a dielectric. FIGS. 4B to 4E are views showing another embodiment of the magnetic permeability measuring device of the present invention, which is a view showing a cross-sectional structure. In the triplate type of (b), the parallel line type of (c), the coplanar type of (d), and the coaxial type of (e), the same effect as that of the microstrip type of (a) can be obtained. In the figure, 1 is a line, 5 is a ground conductor, and 6 is a dielectric.
Here, the dielectric 6 is necessary in terms of structural strength, and the same effect can be obtained even with air or vacuum.

Next, the principle of measurement will be described with reference to FIG. In FIG. 3, the reflection coefficient at the a end is S ₁₁ (measured value), the reflection coefficient at the b end is S ₂₂ (measured value), the transmission coefficient from the a end to the b end is S ₂₁ (measured value), in line 1. It is assumed that the absorption coefficient due to other than the magnetic material 2 is A ₀ and the absorption coefficient due to the magnetic material 2 in the line 1 is A _m . Further, by comparing the anisotropic magnetic field of the magnetic body 2 to the line 1, these coefficients are measured when a sufficiently large magnetic field is applied from the outside.
_{Like 11} (H), these coefficients when not applied are represented as S ₁₁ (0). The following formula is established between these coefficients.

[Equation 1] (1- [S ₁₁ (0)] ² ) (1- [A ₀ (0)] ² ) (1- [A
_m (0)] ² ) (1- [S ₂₂ (0)] ² ) = [S ₂₁ (0)] ² … (1)

[Equation 2] (1- [S ₁₁ (H)] ² ) (1- [A ₀ (H)] ² ) (1- [A
_m (H)] ² ) (1- [S ₂₂ (H)] ² ) = [S ₂₁ (H)] ² … (2) Here, when a magnetic field sufficiently larger than the anisotropic magnetic field is applied, absorption by the magnetic substance Becomes very small, and [A _m (H)] ^{2 to} 0 can be set. Therefore, the formula (2) is

[Equation 3] (1- [S ₁₁ (H)] ² ) (1- [A ₀ (H)] ² ) (1- [S ₂₂ (H)]
² ) = [S ₂₁ (H)] ² … (3). Also,

[Expression 4] L (0) = (1- [S ₁₁ (0)] ² ) (1- [S ₂₂ (0)] ² ) / [S ₂₁
(0)] ² … (4)

[Equation 5] L (H) = (1- [S ₁₁ (H)] ² ) (1- [S ₂₂ (H)] ² ) / [S ₂₁
(H)] ² ... (5), from the formulas (1) to (5), [A _m (0)] ² = 1-L (H) / L (0)
… (6). Incident power P _in to line 1, loss power P _{m due} to magnetic material, relative permeability μr (: μr′−j · μ of magnetic material)
r ″, where (−1) ^1/2 = j) and frequency f,

[Equation 6] P _in・ [A _m (0)] ² = P _m ∝f ・ μr ″
Since the relationship of (7) holds,

[Equation 7] μr ″ ∝ [A _m (0)] ² / f
... (8), and determined using the A _m the ₍₀₎ (6) at each frequency f, when the absolute value calibrated with standard samples, so that .mu.r "is required. In addition, .mu.r ' And μr ″ for Kramers-Kronig (Kram
ers-Kronig) relationship (C. Kittel, INTRODUCTIONTO SOLI
D STATE PHYSICS, John Wiley & Sons, Inc. 1976),

[Equation 8] Therefore, if the frequency characteristic of μr ″ is known, μ
The frequency characteristic of r'is also required. Where ω = 2πf,
x means an integration variable, and P means a main value of integration. Above, S
_From the transmission characteristics of the magnetic permeability measuring instrument of the present invention using S parameters such as ₁₁ , S ₂₂ and S ₂₁ , it was shown that the frequency characteristic of the relative magnetic permeability of the magnetic material can be obtained. Since the transmission line is used in this method, the resonance phenomenon of the measurement system, which has been a problem in the conventional method, does not occur, and the magnetic permeability can be measured even in a high frequency band of 100 MHz or more.

Next, a specific measurement example will be shown. A magnetic permeability measuring device of the type shown in FIG. 3 was adopted, and network analyzers HP8753A and HP8720B were used for measuring transmission characteristics. A coaxial cable was connected to the input and output terminals of the network analyzer, and this was converted into a microstrip line and connected to a magnetic permeability measuring instrument. Co ₅₀ is used for the magnetic body 2.
Multi-layered film CoFe of Fe ₅₀ (at%) alloy and SiO ₂
/ SiO ₂ (50 nm / 100 nm), Cu was used for the conductor 3 and the ground conductor 5, and Corning No. 0211 glass having a relative dielectric constant of 6 was used for the dielectric 6. Each size is lc = 10 mm, 1 m = wc = 1500 μm, wm =
dc = 50 μm, dm = 5 μm, tm = 1.5 μm, t
c = 2 μm and td = 0.5 mm. The measurement results are shown in FIG. The absolute value of μr ′ was calibrated from the μr ′ value of 40 at the low frequency of the CoFe / SiO ₂ multilayer film. In this example, the upper limit frequency 20 of the network analyzer HP8720B is
The frequency characteristic of μr up to GHz could be measured. As is clear from the above results, the magnetic permeability measuring method of the present invention is 100% compared with the conventional magnetic permeability measuring device and the magnetic permeability measuring method.
There has been an improvement in that the magnetic permeability can be measured in the high frequency band of MHz or higher.

[0010]

As described above, the magnetic permeability measurement of the present invention is performed.
In the conventional method , since the measurement system does not resonate, there is an effect that the permeability can be measured at any high frequency in principle.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a line of a magnetic permeability measuring instrument of the present invention.

FIG. 2 is a diagram showing an example of a line of a magnetic permeability measuring instrument of the present invention.

FIG. 3 is a diagram showing an embodiment of a magnetic permeability measuring instrument of the present invention.

FIG. 4 is a diagram showing another embodiment of the magnetic permeability measuring instrument of the present invention.

FIG. 5 is a diagram showing a frequency characteristic of relative permeability.

[Explanation of symbols]

1 line 2 magnetic material 3 conductors 4 Non-magnetic material 5 Ground conductor 6 Dielectric

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-5-157784 (JP, A) JP-A-4-238283 (JP, A) JP-A-1-244343 (JP, A) JP-A-1- 54273 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01R 33/02-33/18

Claims (5)

(57) [Claims] 1. A line in which a magnetic material is arranged on the surface of a conductor so as to surround the conductor directly or via a non-magnetic material, or to sandwich the conductor, and the line is electrically insulated. In the measurement system including the ground conductors arranged in parallel, the reflection coefficient S ₁₁ at one end and the reflection coefficient S at the other end
₂₂ and the transmission coefficient _{S 21} from one end to the other, the
The square of the absorption coefficient due to the magnetic substance on the line is 1
A magnetic field that is sufficiently large as compared with the anisotropic magnetic field of the magnetic material that is considered to be sufficiently small in comparison with the line
Permeability measurement method and obtains the case of not applying the case of an externally applied by measuring the magnetic permeability of the magnetic body with respect. 2. The magnetic permeability of the magnetic material is L (0) = (1- [S ₁₁ (0)] ² ) (1- [S ₂₂ (0)] ² ) / [S ₂₁ (0)] ² L (H) = (1- [S ₁₁ (H)] ² ) (1- [S ₂₂ (H)] ² ) / [S ₂₁ (H)] ² [A _m (0)] ² = 1- The magnetic permeability measuring method according to claim 1, wherein the magnetic permeability is measured using four formulas of L (H) / L (0) μr ″ ∝ [A _m (0)] ² / f. In the two equations, S ₁₁ (H): reflection coefficient at one end of the measurement system when a sufficiently large magnetic field is applied to the line from the outside, S ₂₂ (H): magnetic substance in the line The reflection coefficient at the other end of the measurement system when a magnetic field that is sufficiently larger than the anisotropic magnetic field of S ₂₁ (H): S ₂₁ (H): A magnetic field that is sufficiently large compared to the anisotropic magnetic field of the magnetic substance is applied to the line. transmission coefficient from one end of the measuring system to the other end in the case of applying the, S ₁₁ (0): the reflection at one end of the measuring system when not applying a magnetic field from the outside to the line The number, S ₂₂ (0): the reflection coefficient at the other end of the measurement system in the case of not applying a magnetic field from the outside to the line, S ₂₁ (0): from one end of the measuring system when not applying a magnetic field from the outside to the line Permeability coefficient, μr ″: relative permeability of a magnetic material μr = μr′−j · μr ″
The imaginary part of the relative magnetic permeability, where (-1) ^1/2 =
j, f: the frequencies at which the reflection coefficients and the transmission coefficients are measured . 3. The magnetic permeability measuring method according to claim 1, wherein the magnetic body has a strip shape. 4. The line and the ground conductor are arranged so as to be electrically insulated from each other through a dielectric, air, or vacuum. The magnetic permeability measurement method described. 5. The measurement system is a microstrip type,
Alternatively, the magnetic permeability measuring method according to any one of claims 1 to 4, wherein the structure has any one of a triplate type, a parallel line type, a coplanar type, and a coaxial type.