JP3085651B2 - Magnetic field sensor - 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 field sensor which can be used as a detection coil of a permeance measuring device, and more particularly to a magnetic field sensor using a strip conductor.

[0002]

2. Description of the Related Art As a conventional magnetic field sensor, a magnetoresistive element and a Hall element are generally known. Further, as a conventional magnetic field sensor using a microstrip line capable of detecting a high-frequency magnetic field using a microstrip line, there is one disclosed in Japanese Patent Application Laid-Open No. 8-129958. As shown in FIG. 8, the magnetic field sensor 50 using the microstrip line has almost one turn on the surface of the dielectric substrate 51 along the outer periphery of the through hole 51-1 provided in the dielectric substrate 51. And characteristic impedance 50Ω
And terminated by connecting the open end (termination side) of the microstrip conductor 53 to the ground conductor 52 formed on the back surface of the dielectric substrate 51 by a termination resistor 54 of 50Ω. .

[0003]

However, the above-mentioned conventional magnetic field sensor using a magnetoresistive element or a Hall element has a low operating frequency band. For example, in the case of a Hall element, detection of a high-frequency magnetic field of about 10 MHz is a limit. , G
There is a problem that a high-frequency magnetic field in the Hz band cannot be detected.

The above-mentioned conventional magnetic field sensor using a microstrip line is advantageous because it can detect a high-frequency magnetic field. And the sensitivity is low.

An object of the present invention is to provide a magnetic field sensor capable of detecting a high-frequency magnetic field in a GHz band, having a small ratio of an induced voltage due to an electric field, and having high sensitivity.

[0006]

In the magnetic field sensor according to the present invention, a through hole is provided substantially at the center, and a notch for communicating the through hole to the outside is provided, and the through hole and the notch coincide with each other. Ground conductors are separately formed on the respective outer surfaces of a pair of dielectric wiring boards to be stacked facing each other, and a predetermined position facing the notch across the through hole is set as a start end position, and a C-shaped is formed. A predetermined position in one half-peripheral portion is defined as an end position. From the starting end position, along the other C-shaped half-periphery, across the notch, and along one C-shaped half-periphery to the end position. Forming a strip conductor on the inner surface of the dielectric wiring board, electrically connecting each ground conductor and the strip conductor at the terminal position, electrically connecting each ground conductor, Connect the ground conductor and strip The induced voltage between the starting end position of the conductor, characterized in that the magnetic field detection output.

[0007] According to the magnetic field sensor of the present invention, an almost half-turn coil is formed by the strip conductor,
An induced voltage is generated by a change in magnetic flux linked to a coil formed by the strip conductor, and a high-frequency magnetic field can be detected based on the induced voltage induced in the strip conductor.

In this case, since the strip conductor is sandwiched between the ground conductors,
It is shielded from the external electric field, and each ground conductor is formed symmetrically with respect to the line connecting the notch from the beginning of the strip conductor. Only the induced voltage due to the Further, since the induced voltage is high, it is possible to detect a magnetic field over a wide band while maintaining S / N in a low-frequency magnetic field.

In order to measure the permeance of a magnetic thin film using the magnetic field sensor according to the present invention, a characteristic impedance of a pair of parallel transmission lines opposed to each other is measured.
The magnetic field sensor of the present invention is inserted into a substantially uniform high-frequency magnetic field generated by energizing an exciting coil terminated by a terminating resistor of 0Ω, and an induced voltage between a ground conductor and a strip conductor of the magnetic field sensor is generated. Based on the above, the permeance of the magnetic thin film inserted into the through hole of the magnetic field sensor is measured.

In order to measure the permeance of a magnetic thin film using the magnetic field sensor according to the present invention, an exciting coil constituted by a pair of parallel transmission lines facing each other and terminated by a terminating resistor having a characteristic impedance of 50Ω is used. When two magnetic field sensors of the present invention are inserted into a substantially uniform high-frequency magnetic field generated by energizing the magnetic field and the magnetic thin film is inserted into the through hole, the magnetic field sensor and the ground conductor and the strip conductor of one magnetic field sensor are inserted. Magnetic thin film inserted into the through-hole of the one magnetic field sensor based on the induced voltage between the magnetic field sensor and the induced voltage between the ground conductor and the strip conductor of the other magnetic field sensor in a state where the magnetic thin film is not inserted into the through-hole. Is measured.

In the measurement of permeance, the measured value of the induced voltage between the ground conductor and the strip conductor when the magnetic thin film is not inserted (the measured value of the high-frequency magnetic field used for calibration) and the magnetic thin film were inserted. It is based on the measured value of the induced voltage between the ground conductor and the strip conductor in the state, but by inserting the two magnetic field sensors into the high frequency magnetic field, the output of the two magnetic field sensors allows the two induced voltages to be measured. Are obtained at the same time, and the number of measurements is halved compared to the case where one magnetic field sensor is used, so that the measurement can be performed in a short time.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

FIG. 1 is a partially sectional perspective view showing a configuration of a magnetic field sensor according to one embodiment of the present invention, and FIG. 2 is an exploded perspective view showing a configuration of the magnetic field sensor according to one embodiment of the present invention. It is.

In the magnetic field sensor 1 according to one embodiment of the present invention, a through-hole 6 is provided substantially at the center, and a notch G (hereinafter, also referred to as a gap G) connecting the through-hole 6 to the outside is provided. A dielectric wiring board 2-1 formed of a Teflon substrate or a glass epoxy resin substrate and formed substantially in a C-shape, and a cut-out in which a through-hole 6 is provided substantially in the center and the through-hole 6 communicates with the outside. A dielectric wiring board 2-2 made of a Teflon substrate or a glass epoxy resin substrate or the like formed with a notch portion G and formed substantially in a C shape is combined with the dielectric wiring board 2-1 and the dielectric wiring board 2-2. Are stacked so that the through-holes 6 coincide with each other and the gap portions G of the dielectric wiring board 2-1 and the dielectric wiring board 2-2 match. Here, the dielectric wiring board 2-1 and the dielectric wiring board 2-2 are made of the same material.

On the other hand, a ground conductor 3-1 and a ground conductor 3-2 are separately formed on the outer surfaces of the dielectric wiring board 2-1 and the dielectric wiring board 2-2, respectively.
The ground conductor 3-1 and the ground conductor 3-2 are connected to the coaxial cable 5 at an end position P (hereinafter, also referred to as a start end position P) of the ground conductor 3-1 and the ground conductor 3-2 opposed to the gap portion G with the. Are electrically connected to the outer conductor (outer conductor).

On the other hand, from a starting position P on the dielectric wiring board 2-1 to a predetermined position E (hereinafter referred to as an ending position E) in one of the C-shaped half-circumferential portions formed on the dielectric wiring board 2-1. Up to the following), extending along the other half of the C-shape formed by the dielectric wiring board 2-1 and across the gap G to form the C formed by the dielectric wiring board 2-1. The dielectric wiring board 2-
A strip conductor 4 having a characteristic impedance of 50Ω and having a half-turn is formed on the inner surface of the substrate 1. At the end position E of the strip conductor 4, the strip conductor 4 penetrates the dielectric wiring board 2-1 and the dielectric wiring board 2-2. Strip conductor 4
And the ground conductor 3-1 and the ground conductor 3-2 are electrically connected and terminated, and the strip conductor 4 is electrically connected to the center conductor (inner conductor) of the coaxial cable 5 at the start position P of the strip conductor 4. Then, an induced voltage between the strip conductor 4 and the ground conductors 3-1 and 3-2 is taken out.

Therefore, in the magnetic field sensor 1, the strip conductor 4 having a characteristic impedance of 50Ω and approximately half turn formed through the gap G is connected to the ground conductor 3-1 via the dielectric wiring boards 2-1 and 2-2. And the strip conductor 4 is sandwiched between the ground conductor 3-2 and the ground conductor 3-2, and the strip conductor 4 penetrates through the dielectric wiring board 2-1 and the dielectric wiring board 2-2 at its end (E). 1 and the ground conductor 3-2, the strip conductor 4 is electrically connected to the center conductor of the coaxial cable 5 at the start position P, and the ground conductor 3-1 and the ground conductor 3-2 are coaxial. It is electrically connected to the outer conductor of the cable 5, so that the induced voltage of the strip conductor 4 is extracted by the coaxial cable 5.

In the magnetic field sensor 1 constructed as described above, since the strip conductor 4 is sandwiched between the ground conductor 3-1 and the ground conductor 3-2, the strip conductor 4 is shielded from an external electric field, so that the shielded digit loop coil is formed. Becomes Since the ground conductor surfaces of the ground conductor 3-1 and the ground conductor 3-2 are formed symmetrically with respect to a line connecting the gap G and the start end position P of the strip conductor 4, the induced voltage due to the electric field is generated. Is differentially suppressed, the induced voltage due to the electric field is canceled out,
A voltage induced mainly by a magnetic field is extracted.

Further, the induced voltage per unit area of the coil by the strip conductor 4 in the magnetic field sensor 1 is, as described later, per unit area of the microstrip conductor 53 in the magnetic field sensor 50 disclosed in Japanese Patent Application Laid-Open No. 8-129958. Since it is about three times the induced voltage, it is possible to detect a magnetic field in a wide band while maintaining S / N in a low-frequency magnetic field.

Further, since the magnetic field sensor 1 itself operates as a balun, the magnetic field sensor 1 also serves to match the unbalanced mode of the signal transmission coaxial cable 5 with the balanced mode of the magnetic field sensor 1.

As the dielectric wiring board 2-1 and the dielectric wiring board 2-2, the dielectric constant ε _r is ε _r = 5 and the thickness d is d =
Using a 0.5 mm Teflon printed board, the length g of the gap G is set to 1 mm, and the vertical length l of the dielectric wiring board 2-1 and the dielectric wiring board 2-2 of the Teflon from the gap G is set. (L) to 2 mm, dielectric wiring board 2
-1 and the length w of the through hole 6 of the dielectric wiring board 2-2 is 26 mm, and the height h of the through hole 6 of the printed circuit board is 2 mm.
In the case where the line width cw of the strip conductor 4 is 0.5 mm, the characteristic impedance at each position on the strip conductor 4 along the strip conductor 4 with reference to the start position P of the strip conductor 4 is measured by time domain reflection measurement. Law (T
DR) (HP5421A Hewlett-Packard)
As shown in FIG. As is clear from FIG. 3, the characteristic impedance of the strip conductor 4 up to the gap G is almost constant at 50Ω, and rapidly increases at the position of the gap G to reach almost 110Ω. After passing through the position, it dropped sharply to about 0Ω, and the characteristic impedance from the starting position P of the strip conductor 4 to the gap G was almost 50Ω.

Next, a broadband permeance measuring apparatus for a magnetic thin film as a sample to be measured using the magnetic field sensor 1 will be described.

FIG. 4 is a schematic view showing the configuration of a permeance measuring device using the magnetic field sensor 1.

The permeance measuring device 20 shown in FIG.
The magnetic field sensor 1 includes an exciting coil 21 for generating a substantially uniform alternating magnetic field and the magnetic field sensor 1, and the measurement sample 30 is inserted into the through hole 6 of the magnetic field sensor 1.

The excitation coil 21 is constituted by flat transmission lines 22 and 23 each having a flat strip line structure and opposed to each other.

The flat transmission line 22 has a substantially rectangular flat transmission line portion 22-1 and a tapered flat transmission line portion 22- extending from both ends of the flat transmission line portion 22-1.
2, 22-3.

The flat transmission line 23 is also a flat transmission line 22.
Similarly to the above, the transmission line portion 23-1 is formed of a substantially square plate transmission line portion 23-1 and tapered plate transmission line portions 23-2 and 23-3 extending from both ends of the plate transmission line portion 23-1. Further, the flat transmission line portion 22-1 extends from the end of the flat transmission line portion 23-2 and the end of the flat transmission line portion 23-3 so that the flat transmission line portion 22-1 is parallel to the flat transmission line portion 23-1. And a flat transmission line portion 23-4 and a flat transmission line portion 23-5 for fixing for supplying the exciting current and connecting the terminating resistor 24 to each other. The flat transmission line 22 and the flat transmission line 2 are connected via a connector 26 provided at 23-4.
3 is supplied with a high-frequency electromagnetic current. On the other hand, one end of the terminating resistor 24 is connected to the flat transmission line portion 23-5, and the other end of the terminating resistor 24 is connected to the flat transmission line portion 22-3 through the flat transmission line portion 23-5. And is terminated.

Here, the excitation coil 21 includes the fixed flat transmission line portions 23-4 and 23-5 and the tapered flat transmission line portions 22-2, 22-3, 23-2 and 23-3. The characteristic impedance is set to 50Ω
Termination is performed by a terminating resistor 24 of Ω, and impedance matching is performed. For example, in order to measure the permeance up to the 1 GHz band, it is necessary to remove the LC resonance. However, the LC resonance is removed by the above impedance matching. Further, only the traveling wave of the TEM is propagated in the exciting coil 21.

Also, TE from the electromagnetic field in the exciting coil 21
To eliminate higher-order modes other than M
The cross-sectional dimensions and the total length of 2, 23 are determined to be 波長 wavelength of the upper limit frequency. In this example, for example, wc =
50 mm, Lc = 15 mm, flat transmission lines 22 and 23
Was set to de = 10 mm (see FIG. 4).
On the other hand, in the case of a frequency of several hundred MHz or more, the ratio of the induced voltage due to the electric field to the magnetic field sensor increases, and at the same time, the induced voltage due to the magnetic field depends on the presence or absence of the measurement sample 30 and the material and size of the dielectric wiring substrate constituting the magnetic field sensor Therefore, it is necessary to extract only the induced voltage due to the magnetic field. However, as described above, the magnetic field sensor 1 extracts only the induced voltage due to the magnetic field.

When a high-frequency current is supplied to the exciting coil 21 via the connector 26 in the permeance measuring device 20 shown in FIG. 4 and the terminating resistor 24 has a characteristic impedance of 50Ω (matching), the terminating resistor 24 is removed and the flat plate is formed. When the transmission lines 22 and 23 are opened and when the terminating resistor 24 is short-circuited and the plate-shaped transmission lines 22 and 23 are short-circuited, respectively, inserted between the plate-shaped transmission lines 22 and 23. The induced voltage of the magnetic field sensor 1 is as shown in FIG. In FIG. 5, the solid line shows the case of matching, the broken line shows the case of short circuit, and the dashed line shows the case of open circuit.

On the other hand, when the measurement is performed using the magnetic field sensor 50 in place of the magnetic field sensor 1, when the matching is performed by the terminating resistor 54 as described above, when the terminating resistor 54 is removed (opened), The induced voltage of the magnetic field sensor 50 when the terminating resistor 54 is short-circuited is as shown in FIG. In FIG. 6, the solid line shows the case of matching, the broken line shows the case of short circuit, and the dashed line shows the case of open circuit.

As is clear from a comparison between FIG. 5 and FIG.
In the case of the strip conductor 4 in the magnetic field sensor 1, the induced voltage per unit area is about three times that of the microstrip conductor 53 in the magnetic field sensor 50 (for example, 100 MHz; in the case of a short circuit, the induced voltage of the former is about 32).
mV, and the latter induced voltage is about 10 mV). FIGS. 5 and 6 show the measurement results when the area of the strip conductor 4 and the area of the microstrip conductor 53 are substantially equal.

When the end of the exciting coil 21 is short-circuited or open, the magnetic field and the electric field become maximum in the exciting coil 21, respectively. The induced voltage due to the magnetic field is proportional to the frequency based on Faraday's law of electromagnetic induction. On the other hand, since the induced voltage due to the electric field is proportional to the square of the frequency, the ratio of the induced voltage due to the electric field is higher in the high frequency region near GHz than in the magnetic field.

According to FIG. 6, in the case of the magnetic field sensor 50, the induced voltage due to the electric field is larger than the induced voltage due to the magnetic field at the frequency of 500 MHz to 1 GHz. This is thought to be for two reasons. First, the ground conductor 5 of the magnetic field sensor 50
Since the eddy current recirculates in two planes, the amount of interlinkage magnetic flux
Second, the microstrip conductor 53 is not shielded from the electric field.

On the other hand, in the case of the magnetic field sensor 1, as described above, the ground conductor 3-1 and the ground conductor 3-2 serve as an electric shield, and the induced voltage due to the magnetic field is reduced to about 2 GHz by the induced voltage due to the electric field. About one order of magnitude larger.
This is because there is a gap G on the ground conductor 3-1 surface and the ground conductor 3-2 surface, and the ground conductor 3-1 surface and the ground conductor 3-
It is considered that this is because the eddy current flowing back to the two surfaces is small. Therefore, in the magnetic field sensor 1, since the induced voltage due to the electric field is as small as the GHz band, the magnetic thin film, the dielectric wiring board 2-1 and the dielectric wiring board 2-2 as the measurement sample 30 are used.
It is considered that the change in the electric field distribution due to the influence of the electric field and the induced voltage due to the electric field can be suppressed, and the increase of the interlinkage magnetic flux mainly by the magnetic material as the measurement sample 30 can be detected.

Next, Co ₈₅ Zr ₃ was used as the measurement sample 30.
Nb ₁₂ thin film (diameter 6 mm, thickness 1 μm), formed in Ar atmosphere at 20 mTorr and 200 W, and heat treated in a rotating magnetic field (500 ° C., 2 hours, 60 rpm)
Then, heat treatment in a static magnetic field (500 ° C., 1 hour)
The permeance measuring device 20 shown in FIG.
Was measured by That is, the through hole 6 of the magnetic field sensor 1
Then, the magnetic permeability of the measurement sample 30 was measured based on the measured value of the induced voltage from the magnetic field sensor 1.

The measurement results are as shown in FIG. In FIG. 7, μr ′ indicates the real part of magnetic permeability (dashed line), μr ″ indicates the imaginary part of magnetic permeability (solid line), and in FIG. This is a calculated value in consideration of eddy current and natural resonance.The measured value and the calculated value agree well.The reason that the measured value does not match the calculated value at several 100 MHz is due to the anisotropic dispersion of the magnetic film. From the above, the magnetic permeability is about 1.5 GHz.
It has been measured up to.

In the state shown in FIG. 4, that is, in a state where the magnetic field sensor 1 is inserted between the flat transmission line 22 and the flat transmission line 23 forming the exciting coil 21, the other magnetic field sensor 1 Is inserted into the excitation coil 21 almost in parallel with the magnetic field sensor 1, the measurement sample 30 is inserted into the through hole 6 of the magnetic field sensor 1, and the other magnetic field sensor 1
Without using the measurement sample inserted therein, the induced voltage from the other magnetic field sensor 1 is used for calibration, and the measurement sample 30 based on the induced voltage from the magnetic field sensor 1 and the induced voltage from the other magnetic field sensor 1 is used. May be measured.

The induced voltage from the other magnetic field sensor 1 is a measurement output based on a high-frequency magnetic field. In the measurement of permeance, the induced voltage from the magnetic field sensor 1 and the induced voltage from the other magnetic field sensor 1 as a background are measured. Permeance is measured based on the voltage. Thus 2
By using one magnetic field sensor 1 and using one of them for calibration, the number of times of measurement of the induced voltage can be substantially halved compared to the case where one magnetic field sensor 1 is used.

[0040]

As described above, according to the magnetic field sensor of the present invention, the magnetic field sensors are formed substantially in the shape of a letter C, and
Ground conductors are separately formed on the outer surfaces of a pair of dielectric wiring boards in which the letter-shaped penetrating portions and the notch portions are aligned and opposed to each other, and face the notch portions with the C-shaped penetrating portions interposed therebetween. A predetermined position in one half of the C-shape as an end position, along the other half-periphery of the C-shape from the start-end position, and across the notch to form a C-shape. Forming a strip conductor on the inner surface of one of the dielectric wiring boards along a half-periphery of the ground conductor up to the terminal position, and electrically connecting the respective ground conductors and the strip conductor at the terminal position; Is electrically connected to detect the magnetic field by the induced voltage between the electrically connected ground conductor and the start position of the strip conductor, so that the magnetic flux linked to the coil formed by the strip conductor is To change Induced voltage is generated in the strip conductors I, there is an effect that can be detected in the high-frequency magnetic field by the induced voltage.

Further, the magnetic field sensor according to the present invention has the effect that the induced voltage due to the electric field is canceled out, the electric field distribution and the change in the induced voltage due to the electric field can be suppressed, and only the induced voltage mainly due to the magnetic field can be taken out.

The permeance of a magnetic thin film can be measured using the magnetic field sensor of the present invention.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a configuration of an embodiment of a magnetic field sensor according to the present invention.

FIG. 2 is an exploded perspective view showing a configuration of an embodiment of a magnetic field sensor according to the present invention.

FIG. 3 is a characteristic impedance characteristic diagram of a strip conductor in an embodiment of the magnetic field sensor according to the present invention.

FIG. 4 is a partially sectional perspective view of a permeance measuring device using the magnetic field sensor according to the present invention.

FIG. 5 is an induced voltage characteristic diagram of one embodiment of the magnetic field sensor according to the present invention.

FIG. 6 is a diagram showing an induced voltage characteristic of a conventional magnetic field sensor.

FIG. 7 is a diagram showing a measurement result of permeance according to an embodiment of the magnetic field sensor according to the present invention.

FIG. 8 is a perspective view showing a configuration of a conventional magnetic field sensor.

[Explanation of symbols]

1. Magnetic field sensor 2-1, 2-2 ...
Dielectric wiring board 3-1, 3-2 ... ground conductor 4 ... strip conductor 5 ... coaxial cable P ... start end position E ... end position 20 ... permeance measuring device 21 ... excitation coil 24 ... termination resistance

Claims (5)

(57) [Claims] A through hole is provided at substantially the center, a notch is provided to communicate the through hole to the outside, and a pair of dielectrics are stacked so that the through hole and the notch coincide with each other and face each other. A ground conductor is separately formed on each outer surface of the wiring board, a predetermined position facing the notch across the through hole is defined as a start position, and a predetermined position in one half of the C-shaped half is defined as an end position. Along the other half of the C-shape from the starting position,
A strip conductor is formed on the inner surface of one of the dielectric wiring boards across the notch portion and along one of the C-shaped half-peripheries up to the termination position, and a ground conductor and a strip conductor are formed at the termination position. Are electrically connected to each other, each ground conductor is electrically connected, and the induced voltage between the electrically connected ground conductor and the starting position of the strip conductor is used as a magnetic field detection output. Magnetic field sensor. 2. The characteristic impedance of a strip conductor is 5
2. The magnetic field sensor according to claim 1, wherein the magnetic field sensor is set to 0Ω. 3. An earth coil inserted into a substantially uniform high-frequency magnetic field generated by energizing an exciting coil formed of a pair of parallel transmission lines facing each other and terminated by a terminating resistor having a characteristic impedance of 50Ω. 2. The permeance of a magnetic thin film inserted into a through hole is measured based on an induced voltage between a conductor and a strip conductor.
A magnetic field sensor as described. 4. The magnetic field sensor according to claim 3, wherein the pair of parallel transmission lines forming the exciting coil have a characteristic impedance set to 50Ω. 5. Two substantially parallel high-frequency magnetic fields generated by energizing an exciting coil formed of a pair of parallel transmission lines facing each other and terminated by a terminating resistor having a characteristic impedance of 50Ω are inserted. The induced voltage between the ground conductor and the strip conductor of one magnetic field sensor when the magnetic thin film is inserted into the through hole, and the ground conductor and the strip conductor of the other magnetic field sensor when the magnetic thin film is not inserted into the through hole. The magnetic field sensor according to claim 1, wherein the permeance of the magnetic thin film is measured based on an induced voltage between the magnetic field and the magnetic field.