JP2011169793A - Magnetic field probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic field probe with which the sensitivity in a desired frequency band can be improved by reducing the influence of reflected waves. <P>SOLUTION: The magnetic field probe 1 includes a transmission line part 12 connecting a detection part 9 and a connection part 10. This transmission line part 12 includes a strip conductor 13. The strip conductor 13 includes: a narrow part 13A having a narrow width W1; a wide part 13B having a wide width W2; and a tapered part 13C provided between the narrow part 13A and the wide part 13B. Thereby, since reflection is generated around the tapered part 13C in addition to both ends of the transmission line part 12, the frequency affecting the reflected waves can be more shifted compared to the case where the tapered part 13C is not included. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a magnetic field probe suitable for use in detecting a magnetic field.

  As a magnetic field probe according to the prior art, a detection unit made of a loop coil is provided on one end side of a substrate, one end side of a transmission line unit made of a strip line is connected to the detection unit, and a connector is connected to the other end side of the transmission line unit What provided the connection part for connecting to the exterior via the etc. is known (for example, refer nonpatent literature 1).

  As another conventional technique, a configuration is known in which a tapered electrode pattern is provided in a high-frequency connection portion that connects a strip line and a coaxial line, etc., and impedance matching is performed between the strip line and the coaxial line. (For example, see Patent Documents 1 and 2).

International Electrotechnical Commission, “IEC 61967-6 First Edition”, International Electrotechnical Commission, June 2002, p.11-31

JP 2004-69337 A JP 2007-123741 A

  By the way, in the magnetic field probe according to Non-Patent Document 1, the coaxial line attached to the transmission line part or the connection part has, for example, a characteristic impedance of 50Ω. On the other hand, the magnetic field probe detects a magnetic field over a wide band such as several tens Hz to several GHz, for example, and the impedance of the detection unit made of a loop coil changes according to the frequency of the magnetic field to be measured. In addition, the impedance of the connection portion to which the connector or the like is attached also tends to deviate from the characteristic impedance because different types of lines (for example, a strip line and a coaxial line) are connected. Therefore, the impedance of the detection unit and the connection unit cannot be made to match the characteristic impedance in all bands, and a difference occurs between the two impedances.

  For this reason, the detection signal of the magnetic field detected by the detection unit generates a reflected wave reflected by the connection unit or the detection unit in addition to the direct wave transmitted directly from the connection unit to the outside. The detection sensitivity tends to decrease for detection signals of some frequencies due to mutual interference.

  On the other hand, Patent Documents 2 and 3 disclose a configuration in which, for example, a tapered electrode pattern is provided at an end portion of a transmission line to improve matching with an external coaxial line. However, as described above, the magnetic field probe has a very wide frequency band of the magnetic field to be measured, and the impedance of the detection unit also changes according to the frequency of the magnetic field to be measured. For this reason, there is a problem that it is very difficult to match the impedances of the detection unit, the transmission line, and the connection unit with respect to detection signals of all frequencies.

  The present invention has been made in view of the above-described problems of the prior art, and an object of the present invention is to provide a magnetic field probe that can reduce the influence of reflected waves and improve sensitivity in a desired frequency band. .

  In order to solve the above-described problems, the present invention provides a substrate made of an insulating material, a detection unit made of a conductive loop provided on the substrate for detecting a magnetic field, and provided on the substrate and connected to the outside. Magnetic field probe comprising: a connection part that outputs a detection signal from the detection part; and a transmission line part that is provided on the substrate and has an elongated conductor pattern that connects between the conductive loop of the detection part and the connection part Applies to

  A feature of the configuration adopted by the invention of claim 1 is that the conductor pattern of the transmission line portion includes a narrow width portion connected to the conductive loop and a narrow width portion connected to the connection portion. And a line width changing portion that is provided between the narrow width portion and the wide width portion and changes the width dimension.

  According to a second aspect of the present invention, the line width changing portion is constituted by a tapered portion whose width dimension gradually increases from the narrow portion to the wide portion.

  According to a third aspect of the present invention, the line width changing portion is constituted by an intermediate coupling portion whose width dimension increases from the narrow width portion toward the wide width portion via one or more intermediate width portions.

  According to a fourth aspect of the present invention, the line width changing portion is constituted by a step portion whose width dimension increases in a step shape between the narrow width portion and the wide width portion.

  According to the invention of claim 1, the conductor pattern of the transmission line portion is provided with the line width changing portion that is located between the narrow width portion and the wide width portion and changes the width dimension. For this reason, in addition to the both ends of the transmission line portion, the detection signal is also reflected around the tapered portion. As a result, compared to the case where reflection occurs only at both ends of the transmission line section as in the prior art, reflection occurs also in the middle of the transmission line section, so the frequency at which the reflected wave affects the detection signal is shifted. Can be made. Thus, by appropriately setting the position of the tapered portion with respect to the length direction of the transmission line portion, the sensitivity of the detection signal in a desired frequency band can be improved.

  According to the invention of claim 2, since the line width changing portion is configured by the tapered portion whose width dimension gradually increases from the narrow width portion toward the wide width portion, the impedance change of the tapered portion in the length direction is reduced. Can do. For this reason, the intensity | strength of the reflected wave which arises in a taper part can be made small, and the influence of a reflected wave can be reduced.

  According to the invention of claim 3, the line width changing portion is constituted by the intermediate connecting portion whose width dimension increases from the narrow width portion toward the wide width portion via the intermediate width portion of one or a plurality of steps. Reflected waves are generated at both ends of the intermediate width portion where the width dimension changes. For this reason, a detection signal in a desired frequency band can be detected with high sensitivity by appropriately adjusting the length dimension and the number of steps of the intermediate width portion.

  According to the invention of claim 4, since the line width changing portion is constituted by the step portion whose width dimension is increased in a step shape between the narrow portion and the wide portion, the reflected wave is generated intensively at the step portion. Can be made. For this reason, since the frequency of the detection signal whose sensitivity decreases according to the position of the stepped portion can be reliably grasped, for example, the length dimension between the detecting portion and the stepped portion or the stepped portion with respect to the desired frequency By setting the length dimension between the first and second connection parts to a value different from the quarter wavelength, the influence of the reflected wave on the detection signal having a desired frequency can be suppressed. Thereby, the detection signal of a desired frequency band can be detected with high sensitivity.

It is a perspective view which shows the magnetic field probe by the 1st Embodiment of this invention. It is a perspective view which shows the detection part in FIG. 1 in the state which saw through the multilayer substrate. It is sectional drawing which looked at the detection part from the arrow III-III direction in FIG. It is a front view which shows the magnetic field probe in FIG. 1 in the state which excluded the insulating layer of the surface side. It is sectional drawing which looked at the connection part from the arrow VV direction in FIG. It is a front view which expands and shows the taper part in FIG. It is a front view similar to FIG. 4 which shows the magnetic field probe by a comparative example in the state which excluded the insulating layer of the surface side. In a 1st embodiment and a comparative example, it is a characteristic line figure showing a frequency characteristic of a gain of a magnetic field probe. It is a front view which shows the magnetic field probe by 2nd Embodiment in the state which excluded the insulating layer of the surface side. It is a front view which expands and shows the intermediate | middle connection part in FIG. It is a front view similar to FIG. 10 which shows the intermediate | middle connection part by a 1st modification. It is a front view which shows the magnetic field probe by 3rd Embodiment in the state which excluded the insulating layer of the surface side. It is a front view which expands and shows the level | step-difference part in FIG. It is a perspective view of the same position as Drawing 2 showing the magnetic field probe by the 2nd modification in the state where seeing through the substrate.

  Hereinafter, magnetic field probes according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  1 to 6 show a magnetic field probe 1 according to the first embodiment. The magnetic field probe 1 is accommodated in a cylindrical case 2 made of, for example, a nonmagnetic insulating material, and is electrically connected to a signal processing circuit (not shown) through a coaxial cable 3 (coaxial line). This signal processing circuit detects a magnetic field generated in the vicinity of the detection unit 9 based on detection signals such as voltage and current generated in the detection unit 9 of the magnetic field probe 1. The magnetic field probe 1 includes a multilayer substrate 4 to be described later, a detection unit 9, a connection unit 10, and a transmission line unit 12 provided on the multilayer substrate 4.

  The multilayer substrate 4 is formed in a flat plate shape extending in parallel with the X axis direction and the Z axis direction, for example, among the X axis direction, the Y axis direction, and the Z axis direction orthogonal to each other. The multilayer substrate 4 is configured by, for example, laminating two insulating layers 5 and 6 in the Y-axis direction that is the thickness direction. At this time, the multilayer substrate 4 has a width dimension of, for example, about several millimeters with respect to the X-axis direction serving as the width direction, and extends along the Z-axis direction serving as the length direction. It is about.

  The insulating layers 5 and 6 are formed in layers using, for example, an insulating resin material. And the front-end | tip part 4A of the multilayer substrate 4 is located in the one end side (lower end side in FIG. 1) of a Z-axis direction, and the below-mentioned detection part 9 is provided. On the other hand, the base end portion 4B of the multilayer substrate 4 is formed to have a width dimension larger than that of the tip end portion 4A, and is disposed on the other end side (upper end side in FIG. 1) in the Z-axis direction.

  Ground electrodes 7 and 8 made of, for example, a conductive metal thin film are provided on the front and back surfaces of the multilayer substrate 4 located on both ends in the Y-axis direction. The ground electrodes 7 and 8 are connected to, for example, an external ground and held at the ground potential, and cover substantially the entire surface of the multilayer substrate 4 except for the front end portion 4A of the multilayer substrate 4. Further, elongate connection electrode portions 7A and 8A extending toward the inside of the distal end portion 4A are provided on the distal end side of the ground electrodes 7 and 8.

  As shown in FIGS. 1 to 3, the detection unit 9 includes a conductive loop 9 </ b> A that is disposed at the distal end portion 4 </ b> A of the multilayer substrate 4 and is formed in a substantially C shape. The conductive loop 9A is formed by, for example, a one-turn loop coil. Specifically, the conductive loop 9A is formed in a substantially rectangular frame shape by using, for example, an elongated electrode pattern made of a conductive metal thin film having a width dimension W0, and an intermediate position in the thickness direction of the multilayer substrate 4 Is disposed between the insulating layers 5 and 6. One end of the conductive loop 9A is electrically connected to the connection electrode portions 7A and 8A through a via 9B penetrating the multilayer substrate 4. On the other hand, the other end side of the conductive loop 9A is electrically connected to a strip conductor 13 of the transmission line portion 12 to be described later.

  And the detection part 9 generate | occur | produces a voltage in 9 A of conductive loops according to the magnetic field (magnetic flux change) which passes the inside of 9 A of conductive loops. Thereby, the detection part 9 detects the magnetic flux change over a wide band, for example to several tens Hz-several GHz.

  As shown in FIGS. 1, 4, and 5, the connection portion 10 is disposed at the base end portion 4 </ b> B of the multilayer substrate 4. The connecting portion 10 includes a through hole 10A provided through the multilayer substrate 4, and a conductive metal film is formed on the inner wall surface of the through hole 10A by plating or the like. Here, substantially circular openings 10B and 10C surrounding the periphery of the through hole 10A are formed in the ground electrodes 7 and 8 positioned at the base end 4B, and the through holes 10A and 10C are formed by the openings 10B and 10C. The ground electrodes 7 and 8 are insulated.

  Further, the through hole 10A is electrically connected to a strip conductor 13 of the transmission line portion 12 described later. A connector 11 such as an SMA connector is attached to the connection portion 10, and the coaxial cable 3 is attached to the connector 11. Thereby, the connection part 10 is connected to an external signal processing circuit via the connector 11 and the coaxial cable 3, and outputs the detection signal of the magnetic field by the detection part 9 toward the signal processing circuit.

  As shown in FIGS. 1, 4 and 6, the transmission line unit 12 is provided on the multilayer substrate 4 and connects between the conductive loop 9 </ b> A of the detection unit 9 and the through hole 10 </ b> A of the connection unit 10. . The transmission line portion 12 has a strip conductor 13 (signal electrode) as an elongated conductor pattern. The transmission line unit 12 is configured by a strip line including a strip conductor 13 and ground electrodes 7 and 8 provided on both surfaces of the multilayer substrate 4.

  The strip conductor 13 extends linearly along the Z axis. The strip conductor 13 includes a narrow width portion 13A having a narrow width dimension W1 connected to the conductive loop 9A of the detection section 9, a wide width section 13B having a wide width dimension W2 connected to the through hole 10A of the connection section 10, and A tapered portion 13C as a line width changing portion provided between the narrow portion 13A and the wide portion 13B is provided.

  Here, the width dimension W1 of the narrow width portion 13A is set to a value approximately the same as the width dimension W0 of the conductive loop 9A of the detection section 9, for example. On the other hand, the width dimension W2 of the wide portion 13B is set to such a value that the characteristic impedance of the strip line is, for example, 50Ω around it.

  The width of the tapered portion 13C gradually increases from the narrow portion 13A toward the wide portion 13B. That is, the width dimension of the tapered portion 13C continuously increases from the narrow width portion 13A toward the wide width portion 13B. The edge portions on both sides in the width direction of the tapered portion 13C extend obliquely with respect to the Z-axis direction. As a result, the impedance of the tapered portion 13C gradually changes from the narrow portion 13A toward the wide portion 13B.

  The magnetic field probe 1 according to the present embodiment has the above-described configuration, and the operation thereof will be described next.

  First, the tip portion of the magnetic field probe 1 is disposed in the state of being close to the surface of a measurement target (for example, a substrate to be measured). Then, the magnetic field probe 1 is moved on the surface of the measurement target. Here, when a magnetic field in the Y-axis direction is generated on the surface of the measurement object located near the magnetic field probe 1, the magnetic field passes through the inside of the conductive loop 9 </ b> A of the detection unit 9. Thereby, for example, a voltage is generated in the conductive loop 9A, and by detecting this voltage, the magnetic field generated on the surface of the measurement object can be detected.

  However, the detection unit 9 and the connection unit 10 are connected using the transmission line unit 12, and the strip conductor 13 of the transmission line unit 12 has a taper unit 13C between the narrow portion 13A and the wide portion 13B. It was set as the structure provided. For this reason, reflection occurs at both end sides of the narrow width portion 13A and both end sides of the wide width portion 13B, and the frequency at which the detection sensitivity is lowered is shifted compared to the case where a strip conductor having a constant width dimension is used.

  Therefore, the frequency characteristics of each gain were measured for the magnetic field probe 1 according to the present embodiment and the magnetic field probe 21 according to the comparative example shown in FIG. The result is shown in FIG.

  In the magnetic field probe 21 according to the comparative example shown in FIG. 7, the strip conductor 23 of the transmission line portion 22 has a certain width dimension in which, for example, the characteristic impedance is 50Ω.

  As indicated by a broken line in FIG. 8, in the case of the comparative example, the gain of the detection signal is reduced in the vicinity of 2 GHz, for example. The reason for this is considered to be that reflection occurs at both ends of the transmission line portion 22, and the reflected wave Sr and the direct wave St interfere with each other to reduce the intensity of the detection signal.

  On the other hand, as indicated by a solid line in FIG. 8, in the case of the present embodiment, the gain of the detection signal is reduced, for example, in the vicinity of 3.2 GHz. In this embodiment, as shown in FIG. 4, reflection occurs at both ends of the narrow portion 13A and both ends of the wide portion 13B, and these reflected waves Sr1 and Sr2 interfere with the direct wave St. This is probably because of this. According to the result of FIG. 8, in this embodiment, for example, the gain decreases near 1 GHz due to the influence of phase change or multiple reflection in the strip conductor 13, but the vicinity of 2.5 GHz. The gain is improved compared to the comparative example. For this reason, for example, a detection signal in a frequency band near 2 to 3 GHz can be detected with higher sensitivity than in the comparative example.

  Thus, in the present embodiment, the strip conductor 13 of the transmission line portion 12 is configured to be provided with the tapered portion 13C that changes the width dimension between the narrow width portion 13A and the wide width portion 13B. For this reason, in addition to the both ends of the transmission line portion 12, the detection signal is also reflected around the tapered portion 13C where the impedance changes. As a result, compared to the case where reflection occurs only at both ends of the transmission line portion 12 as in the prior art, reflection occurs also at an intermediate position of the transmission line portion 12, and therefore the frequency at which the reflected wave affects the detection signal. Can be shifted. Thus, by appropriately setting the position of the tapered portion 13C with respect to the length direction (Z-axis direction) of the transmission line portion 12, the sensitivity of the detection signal in a desired frequency band can be improved. .

  Further, since the taper portion 13C has a configuration in which the width dimension gradually increases from the narrow width portion 13A toward the wide width portion 13B, the impedance change of the taper portion 13C in the length direction can be reduced. For this reason, the intensity | strength of the reflected wave produced in the taper part 13C can be made small, and the influence of a reflected wave can be reduced.

  Next, FIG. 9 and FIG. 10 show a second embodiment of the present invention. The feature of the present embodiment is that the line width changing portion is constituted by an intermediate coupling portion whose width dimension increases from the narrow width portion toward the wide width portion via a single intermediate width portion. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The magnetic field probe 31 includes the detection unit 9, the connection unit 10, and the transmission line unit 32 provided on the multilayer substrate 4 in substantially the same manner as the magnetic field probe 1 according to the first embodiment.

  The transmission line part 32 has a strip conductor 33 as an elongated conductor pattern that is provided on the multilayer substrate 4 and connects between the conductive loop 9A of the detection part 9 and the through hole 10A of the connection part 10. The transmission line portion 32 is configured by a strip line including a strip conductor 33 and ground electrodes 7 and 8 provided on both surfaces of the multilayer substrate 4.

  The strip conductor 33 extends linearly along the Z axis. The strip conductor 33 includes a narrow width portion 33A having a narrow width dimension W1 connected to the conductive loop 9A, a wide width portion 33B having a wide width dimension W2 connected to the through hole 10A of the connection portion 10, and a narrow width portion 33A. And an intermediate connecting portion 33C as a line width changing portion provided between the first and second wide portions 33B.

  The intermediate connecting portion 33C includes an intermediate width portion 33D having a width dimension W3, a tapered connecting portion 33E provided on both ends in the length direction of the intermediate width portion 33D and connected to the narrow width portion 33A and the wide width portion 33B, respectively. It is constituted by. Here, the intermediate width portion 33D has a constant width dimension W3 and extends in the length direction (Z-axis direction). The width dimension W3 of the intermediate width portion 33D is set to a value (W1 <W3 <W2) that is larger than the width dimension W1 of the narrow width portion 33A and smaller than the width dimension W2 of the wide width portion 33B. The width dimension of the intermediate connecting portion 33C increases from the narrow width portion 33A toward the wide width portion 33B via the one-stage intermediate width portion 33D. Further, the tapered connecting portion 33E has a configuration in which the width dimension is gradually increased from the narrow width portion 33A toward the wide width portion 33B in substantially the same manner as the tapered portion 13C according to the first embodiment.

  Thus, the present embodiment can provide the same operational effects as those of the first embodiment. In particular, in the present embodiment, the intermediate connecting portion 33C has a configuration in which the width dimension increases from the narrow width portion 33A to the wide width portion 33B via the one-stage intermediate width portion 33D. A reflected wave is generated at the tapered connecting portion 33E that is located on both ends and has a width that varies. For this reason, by appropriately adjusting the length dimension and the number of steps of the intermediate width portion 33D, the frequency affected by the reflected wave can be shifted, and a detection signal in a desired frequency band can be detected with high sensitivity.

  In the second embodiment, the intermediate connecting portion 33C of the strip conductor 33 has a single-stage intermediate width portion 33D. However, the present invention is not limited to this, and the intermediate connection portion 42C of the strip conductor 42 has two intermediate width portions 42D and 42E, such as the transmission line portion 41 according to the first modification shown in FIG. It is good also as a structure. In this case, the width dimensions of the intermediate width portions 42D and 42E are both set in a range between the width dimension W1 of the narrow width portion 42A and the width dimension W2 of the wide width portion 42B. Further, the width dimension of the intermediate width part 42E close to the wide width part 42B is larger than the width dimension of the intermediate width part 42D close to the narrow width part 42A. Further, tapered connecting portions 42F are provided between the narrow width portion 42A and the intermediate width portion 42D, between the intermediate width portions 42D and 42E, and between the intermediate width portion 42E and the wide width portion 33B.

  Furthermore, the intermediate connecting portion is not limited to one stage and two stages, and may have a structure having intermediate width parts of three or more stages. Moreover, although it was set as the structure connected using a taper-shaped connection part between adjacent intermediate width parts or between an intermediate width part and a narrow width part, a wide width part, a level difference connection part with a discontinuous level difference is used. It is good also as a structure connected using.

  Next, FIG. 12 and FIG. 13 show a third embodiment of the present invention. The feature of the present embodiment is that the line width changing portion is constituted by a step portion in which the width dimension increases in a step shape between the narrow portion and the wide portion. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.

  The magnetic field probe 51 includes a detection unit 9, a connection unit 10, and a transmission line unit 52 provided on the multilayer substrate 4 in substantially the same manner as the magnetic field probe 1 according to the first embodiment.

  The transmission line section 52 has a strip conductor 53 as an elongated conductor pattern that is provided on the multilayer substrate 4 and connects between the conductive loop 9A of the detection section 9 and the through hole 10A of the connection section 10. The transmission line portion 52 is configured by a strip line including a strip conductor 53 and ground electrodes 7 and 8 provided on both surfaces of the multilayer substrate 4.

  The strip conductor 53 extends linearly along the Z axis. The strip conductor 53 includes a narrow width portion 53A having a narrow width dimension W1 connected to the conductive loop 9A, a wide width portion 53B having a wide width dimension W2 connected to the through hole 10A of the connection portion 10, and a narrow width portion 33A. And a step part 53C as a line width changing part provided between the wide part 33B and the wide part 33B. The step portion 53C is enlarged in a step shape having discontinuous width dimensions.

  Thus, the present embodiment can provide the same operational effects as those of the first embodiment. In particular, in the present embodiment, the stepped portion 53C has a configuration in which the width dimension increases in a stepped manner between the narrow-width portion 53A and the wide-width portion 53B, so that reflected waves are generated intensively at the stepped portion 53C. be able to. For this reason, since the frequency of the detection signal whose sensitivity decreases according to the position of the stepped portion 53C can be reliably grasped, for example, the length dimension between the detecting portion 9 and the stepped portion 53C with respect to a desired frequency. In addition, by setting the length dimension between the step portion 53C and the connection portion 10 to a value different from the quarter wavelength, the influence of the reflected wave on the detection signal in a desired frequency band can be suppressed. Thereby, the detection signal of a desired frequency can be detected with high sensitivity.

  In each of the above embodiments, the transmission line portions 12, 32, 41, and 52 are configured by strip lines in which the strip conductors 13, 33, 42, and 53 are provided between the two ground electrodes 7 and 8, respectively. However, the present invention is not limited to this, and as in the second modification shown in FIG. 14, the transmission line portion 12 'is configured by a microstrip line composed of one ground electrode 7 and a strip conductor 13'. May be. In this case, it is not necessary to use a multilayer substrate, and a configuration using a substrate 4 'made of a single-layer insulating material may be used.

  In each of the above embodiments, the conductive loop 9A is formed in a substantially rectangular shape, but may be formed in other polygonal shapes such as a triangle and a pentagon, and may be formed in a circle, a semicircle, an ellipse, and the like. Furthermore, although the conductive loop 9A is formed by a one-turn loop coil, it may be formed by a loop coil wound two or more times.

1,31,51 Magnetic field probe 4 Multilayer substrate (substrate)
4 'Substrate 9 Detection unit 9A Conductive loop 10 Connection unit 12, 12', 32, 41, 52 Transmission line unit 13, 13 ', 33, 42, 53 Strip conductor (conductor pattern)
13A, 33A, 42A, 53A Narrow part 13B, 33B, 42B, 53B Wide part 13C Taper part 33C, 42C Intermediate connection part 53C Step part

Claims (4)

A substrate made of an insulating material; a detection unit comprising a conductive loop provided on the substrate for detecting a magnetic field; and a connection unit provided on the substrate and connected to the outside to output a detection signal from the detection unit. In the magnetic field probe provided with a transmission line portion having an elongated conductor pattern that is provided on the substrate and connects between the conductive loop of the detection portion and the connection portion,
The conductor pattern of the transmission line portion includes a narrow width portion having a narrow width connected to the conductive loop, a wide width portion having a wide width connected to the connection portion, and the narrow width portion and the wide width portion. A magnetic field probe characterized by comprising a line width changing portion provided between them to change the width dimension.   2. The magnetic field probe according to claim 1, wherein the line width changing portion is configured by a tapered portion whose width dimension gradually increases from the narrow width portion toward the wide width portion.   2. The magnetic field probe according to claim 1, wherein the line width changing portion is configured by an intermediate coupling portion whose width dimension increases from the narrow width portion toward the wide width portion via one or more intermediate width portions. .   2. The magnetic field probe according to claim 1, wherein the line width changing unit is configured by a stepped portion having a width dimension increased in a stepped manner between the narrowed portion and the widened portion.

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