Coaxially rotatable broadband low-cost magnetic field probe and magnetic field measuring device

Abstract

The invention relates to the field of near-field electromagnetic measurement, and discloses a broadband low-cost magnetic field probe capable of coaxially rotating and a magnetic field measurement device. The magnetic field probe is based on a low-cost FR-4 material and a conventional four-layer printed circuit board process. The magnetic field probe at least comprises a shielding ring, an isosceles cone ladder transmission structure, a fence type isolation via hole array, a non-metal mounting hole, a 50-ohm strip line, a multi-stage impedance joint matching structure and a side insertion type radio frequency connector. And an isosceles cone ladder transmission structure and a multi-stage impedance matching structure are adopted, so that the impedance continuity is improved, and the gain flatness is improved. The magnetic field measuring device comprises a magnetic field probe, a hollow rotating table, a micrometer, a magnetic field probe clamp, a metal connecting rod, a micrometer, a hollow rotating table, a three-dimensional mechanical arm, a driver module, a controller module, a computer and upper computer software, and magnetic field components in different directions can be accurately detected in the horizontal direction. The method is simple in scheme, low in cost and suitable for multi-component near-field magnetic field testing application.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of near-field electromagnetic measurement, in particular to a coaxial rotatable broadband low-cost magnetic field probe and a magnetic field measurement device. BACKGROUND

[0002] With the continuous improvement of integrated circuit integration and the continuous rise of working frequency, electromagnetic interference problem is increasingly prominent. Near-field measurement shows significant advantages in locating electromagnetic interference sources. In near-field magnetic field measurement, the traditional magnetic field probe can usually only measure a single magnetic field component, and if multiple directional magnetic field components need to be measured, the magnetic field probe often needs to be repeatedly disassembled to adjust the detection direction of the magnetic field probe, or a multi-component magnetic field probe is used. However, in near-field magnetic field testing, repeatedly disassembling the magnetic field probe will introduce unnecessary mechanical errors and affect the measurement accuracy, and the development and application of multi-component probes may bring higher costs. SUMMARY

[0003] In order to solve the above technical problems and meet the development needs of the electronic industry, the present application designs a coaxial rotatable broadband low-cost magnetic field probe and a magnetic field measurement device, which aims to improve the gain flatness of the magnetic field probe and reduce the errors introduced by repeatedly disassembling the magnetic field probe to obtain different detection magnetic field components on the basis of low-cost processing and preparation, and to provide a low-cost, high-performance special tool for accurate testing of near-field magnetic field.

[0004] In order to meet the above purpose, the present application provides the following technical scheme:

[0005] In a first aspect, the present application provides a coaxial rotatable broadband low-cost magnetic field probe, which is made of low-cost FR-4 material and conventional four-layer printed circuit technology; the four-layer printed circuit board is sequentially composed of a top layer, a first prepreg, an intermediate 1 layer, a substrate, an intermediate 2 layer, a second prepreg and a bottom layer from top to bottom; the magnetic field probe comprises at least a shielding ring, an isosceles tapered ladder transmission structure, a fence type isolation via array, a non-metal mounting hole, a 50Ω strip line, a multi-stage impedance joint matching structure and a side-inserted micro coaxial RF connector, the shielding ring and the fence type isolation via array are located at the detection end of the magnetic field probe, the 50Ω strip line and the isosceles tapered ladder transmission structure are located at the transmission end of the magnetic field probe, the multi-stage impedance joint matching structure and the side-inserted micro coaxial RF connector are located at the output end of the magnetic field probe, and the non-metal mounting hole is located at the mechanical connection end of the magnetic field probe.

[0006] The top layer and the bottom layer have inverted "convex" shaped windows in the detection end area, and the fence-type isolation via array is located above the inverted "convex" shaped windows; the isosceles conical trapezoidal transmission structure is an isosceles trapezoid that is wider at the top and narrower at the bottom, with the waistline being a smooth straight line, and the base angle formed by the waistline and the lower horizontal side being greater than 90° and less than 180°, and the base angle is determined by the ratio of the width of the upper horizontal side to the width of the lower horizontal side and the parallel distance;

[0007] The multi-level impedance matching structure consists of a coaxial via array, signal vias, a first-level anti-pad, a second-level anti-pad, a third-level anti-pad, and a signal via pad. On the top layer, the middle layer, and the bottom layer, circular copper of different radii is removed with the signal via as the center to construct the first-level anti-pad, the second-level anti-pad, and the third-level anti-pad, respectively. On the top shielding layer, circular copper is applied with the signal via as the center to construct the signal via pad.

[0008] Optionally, the center conductor of the 50Ω stripline is located in the middle 2 layers, with the impedance reference planes being the middle 1 layer above it and the bottom layer below it.

[0009] Optionally, the barrier-type isolation via array consists of equally spaced metal vias, with all metal vias connecting the top layer and the bottom layer.

[0010] Optionally, the radii of the first-level anti-solder pad, the second-level anti-solder pad, and the third-level anti-solder pad decrease sequentially.

[0011] Secondly, the present invention also provides a coaxially rotatable magnetic field measuring device, which includes a magnetic field probe, a magnetic field probe clamp, a metal connecting rod, a micrometer, a hollow rotary table, a three-dimensional robotic arm, a driver module, a controller module, a computer, and host computer software, as described in any of the first aspects; the magnetic field probe is fixed to the micrometer by the magnetic field probe clamp, the micrometer is connected to the hollow rotary table by the metal connecting rod, and the hollow rotary table is installed on the three-dimensional robotic arm by screws.

[0012] Optionally, the magnetic field probe fixture is composed of a cylindrical block, a first rectangular pressing block, and a second rectangular pressing block. The second rectangular pressing block is physically inseparable from the cylindrical block, while the first rectangular pressing block and the second rectangular pressing block are physically separable. The first rectangular pressing block also has non-metallic mounting holes.

[0013] Optionally, the computer is equipped with host computer control software, which is used to send set operation instructions to the controller module to achieve user-friendly human-computer interaction.

[0014] Optionally, the computer and the controller module communicate through an RS485 interface, the controller module and the driver module are connected through a control cable, and the driver module is connected with the hollow rotating table and the three-dimensional mechanical arm through a driving cable.

[0015] The read register and the write register in the controller module microcontroller follow the MODBUS485 protocol, the setting instruction of the upper computer can be converted into a square wave, and the driver module drives the hollow rotating table to rotate and the three-dimensional mechanical arm to move after power amplification of the converted square wave.

[0016] The coaxial rotating wideband low-cost magnetic field probe and the magnetic field measuring device have the following advantages:

[0017] The coaxial rotating wideband low-cost magnetic field probe and the magnetic field measuring device have the following advantages:

DRAWINGS

[0018] Figure 1 It is a four-layer printed circuit board stack diagram of a coaxial rotating wideband low-cost magnetic field probe.

[0019] Figure 2 It is a whole structure diagram of a coaxial rotating wideband low-cost magnetic field probe.

[0020] Figure 3 It is a three-dimensional development diagram of a coaxial rotating wideband low-cost magnetic field probe.

[0021] Figure 4 It is a plan view of each layer of a coaxial rotating wideband low-cost magnetic field probe.

[0022] Figure 5 It is a clamp structure diagram of a coaxial rotating wideband low-cost magnetic field probe.

[0023] Figure 6 It is a composition schematic diagram of a coaxial rotating magnetic field measuring device.

[0024] Figure 7 It is a frequency response simulation and test result of a coaxial rotating wideband low-cost magnetic field probe before coaxial rotation and after coaxial rotation of 90 degrees.

[0025] Figure 8 Cross-polarization simulation and test results of a coaxial-rotatable broadband low-cost magnetic field probe.

[0026] BRIEF DESCRIPTION OF DRAWINGS

[0027] 1-1: top layer, 1-2: middle 1 layer, 1-3: middle 2 layer, 1-4: bottom layer, 1-5: first prepreg, 1-6: substrate, 1-7: second prepreg, 2-1: detection end, 2-2: inverted "convex" window, 2-3: isosceles tapered transmission structure, 2-4: transmission end, 2-5: side-inserted micro coaxial RF connector, 2-6: non-metal mounting hole, 2-7: mechanical connection end, 2-8: output end, 2-9: fence type isolation via array, 2-10: 50Ω strip line center conductor, 2-11: ground via, 2-12: signal via, 3-1: first level reverse pad, 3-2: second level reverse pad, 3-3: third level reverse pad, 3-4: signal via pad, 3-5: coaxial via array, 3-6: top end connection hole, 3-7: cylindrical block, 3-8: first rectangular pressing block, 3-9: second rectangular pressing block, 4-1: magnetic field probe, 4-2: magnetic field probe clamp, 4-3: micrometer, 4-4: metal connecting rod, 4-5: hollow rotating table, 4-6: three-dimensional mechanical arm, 4-7: drive cable, 4-8: driver module, 4-9: control cable, 4-10: controller module, 4-11: computer, 4-12: RS485 cable. DETAILED DESCRIPTION

[0028] The specific structure of the coaxial-rotatable broadband low-cost magnetic field probe and the magnetic field measuring device, the positional relationship of the structures of the various components, and the functions of the various components are further illustrated in conjunction with the drawings.

[0029] For the sake of understanding the present application, the present application will be described more fully below with reference to the attached drawings. However, the present application can be realized in many different forms and is not limited to the embodiments described herein.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0031] It should be noted that the terms "top", "bottom", "upper", "lower", "top-down", and similar expressions used herein are based on the orientation or relative positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description.

[0032] The processing and preparation of the magnetic field probe designed in the application are based on low-cost FR-4 material and conventional four-layer printed circuit board process. Figure 1 The four-layer printed circuit board stack of the coaxially rotatable wideband low-cost magnetic field probe comprises, from top to bottom, a top layer 1-1, a first prepreg 1-5, a first intermediate layer 1-2, a substrate 1-6, a second intermediate layer 1-3, a second prepreg 1-7 and a bottom layer 1-4. The four-layer printed circuit board structure used in the design scheme has a small number of stack layers, does not involve special processes, and uses FR-4 material which is inexpensive, so the processing and preparation cost of the magnetic field probe is low. In one embodiment of the application, the copper thickness of the top layer 1-1 is 1 oz, the copper thickness of the first intermediate layer 1-2 is 0.5 oz, the copper thickness of the second intermediate layer 1-3 is 0.5 oz, the copper thickness of the bottom layer 1-4 is 1 oz, the material model of the first prepreg 1-5 and the second prepreg 1-7 is FR-4 GreenYard S1000-2B, the material model of the substrate 1-6 is FR-4 GreenYard S1000-2, the thickness of the first prepreg 1-5 is 0.197 mm to 0.199 mm, the thickness of the substrate 1-6 is 0.392 mm to 0.396 mm, and the thickness of the second prepreg 1-7 is 0.192 mm to 0.194 mm. It should be noted that the selection of the FR4 material model and thickness of the first prepreg 1-5, the second prepreg 1-7 and the substrate 1-6 in the scheme should meet the requirements of low cost and stable high-frequency performance.

[0033] Figure 2 The overall structure of the coaxially rotatable wideband low-cost magnetic field probe, Figure 3 The three-dimensional development of the coaxially rotatable wideband low-cost magnetic field probe, Figure 4A plan view of each layer of a coaxial rotatable broadband low-cost magnetic field probe. The magnetic field probe includes a detection end 2-1, a transmission end 2-3, an output end 2-8 and a mechanical connection end 2-7. A 50Ω strip line center conductor 2-10 is located in the middle 2 layer 1-3, and the impedance reference planes are the upper middle 1 layer 1-2 and the lower bottom layer 1-4, respectively. The 50Ω strip line center conductor 2-10 is in the shape of "L", and the end of the horizontal part of the "L" shape of the 50Ω strip line center conductor 2-10 is short-circuited to the top layer 1-1 and the bottom layer 1-4 through a grounding via 2-11. The vertical part of the "L" shape of the 50Ω strip line center conductor 2-10 is located at the transmission end 2-4 of the magnetic field probe. The top layer 1-1, the middle 1 layer 1-2 and the bottom layer 1-4 of the detection end of the magnetic field probe are opened with the same physical size of the inverted "convex" window 2-2. The horizontal part of the "L" shape of the 50Ω strip line center conductor 2-10, the grounding via 2-11 and the inverted "convex" window 2-2 form a shielding ring, which is located at the detection end 2-1 of the magnetic field probe and realizes the induction of the time-varying magnetic field. The vertical part of the "L" shape of the 50Ω strip line center conductor 2-10 is connected with a signal via 2-12, and the signal detected by the shielding ring flows through the signal via 2-12 along the vertical part of the "L" shape of the 50Ω strip line center conductor 2-10, and then is transmitted to an external measuring instrument by a side-inserted micro coaxial RF connector 2-5. In an embodiment of the present application, the side-inserted micro coaxial RF connector 2-5 is a vertical solder-free SMA RF connector, model SMA-KFD216, which is located at the output end 2-8 of the magnetic field probe. The SMA RF connector of this model is low in cost, easy to install and operate, and stable in high-frequency performance. It should be noted that the model of the side-inserted micro coaxial RF connector 2-5 is not fixed and only one case is listed in this embodiment. However, in order to be well connected with the magnetic field probe designed in the present application, the connector style needs to be side-inserted. The physical size of the inverted "convex" window 2-2 needs to be determined by full-wave simulation optimization, and the simulation process needs to pay attention to the climbing bandwidth and improve the transmission gain of the magnetic field probe at low frequency. In an embodiment of the present application, after full-wave simulation optimization, the physical size of the upper half of the inverted "convex" window 2-2 is 1.8mm×1mm, and the physical size of the lower half is 0.65mm×0.4mm. A fence type isolation via array 2-9 is placed above the inverted "convex" window 2-2 to suppress the surface common mode current of the magnetic field probe. The fence type isolation via array 2-9 is located at the detection end 2-1 of the magnetic field probe and is composed of horizontal and vertical metal vias. The number, radius, horizontal distance and vertical distance of the metal vias of the fence type via array 2-9 are determined by full-wave simulation. In an embodiment of the present application, the number of metal vias is 16, the radius is 0.12mm, and the horizontal distance and the vertical distance are both 0.5mm.

[0034] The "L"-shaped vertical part of the 50Ω strip line center conductor 2-10 is connected with a signal via hole 2-12, and there is a sudden change in the characteristic impedance at the signal via hole 2-12, and when the signal induced by the shielding ring flows through the signal via hole 2-12, signal reflection is generated, and the magnetic field probe appears ringing wave, surge wave and even multi-frequency resonance at the high frequency band, which affects the gain flatness and bandwidth of the magnetic field probe. The scheme of the application reduces the processing and preparation cost of the magnetic field probe by using FR-4 material, and the material loss of FR-4 puts higher requirements on the impedance matching accuracy of the magnetic field probe, and the multi-stage impedance joint matching structure is used in the scheme to realize accurate matching of the impedance at the signal via hole 2-12. The multi-stage impedance joint matching structure includes a coaxial via hole array 3-5, a signal via hole 2-12, a first-stage reverse pad 3-1, a second-stage reverse pad 3-2, a third reverse pad 3-3 and a signal via hole pad 3-4. In the top layer 1-1, the middle layer 1-2 and the bottom layer 1-4, a certain radius of circular copper is removed from the signal via hole 2-12 as the center to build the first-stage reverse pad 3-1, the second-stage reverse pad 3-2 and the third-stage reverse pad 3-3, and each stage of the reverse pad keeps the same center, and the signal via hole pad 3-4 is built by covering the circular copper with the center of the signal via hole 2-12 as the center. The radii of the first-stage reverse pad 3-1, the second-stage reverse pad 3-2 and the third-stage reverse pad 3-3 are successively reduced. The coaxial via hole array 3-5 realizes primary matching of the impedance of the signal via hole 2-12, and it should be noted that when adjusting the metal via hole position of the coaxial via hole array 3-5, the metal via hole should not pass through the "L"-shaped vertical part of the 50Ω strip line center conductor 2-10, and the distribution radius and the number of metal via holes of the coaxial via hole array 3-5 are determined by the TDR function of the full-wave simulation. In one embodiment of the application, the coaxial via hole array 3-5 is composed of seven identical metal via holes, all of which are uniformly distributed at an interval of 45° with a distribution radius of 1.0mm-1.4mm, the radius of the metal via hole is 0.120mm-1.30mm, and all the metal via holes are connected with the top layer 1-1, the middle layer 1-2 and the bottom layer 1-4. On the basis of the primary matching of the impedance of the signal via hole 2-12 by the coaxial via hole array 3-5, the radii of the first-stage reverse pad 3-1, the second-stage reverse pad 3-2, the third-stage reverse pad 3-3 and the signal via hole pad 3-5 are successively optimized to realize accurate matching of the impedance of the signal via hole 2-12, and the impedance matching difficulty caused by FR-4 material is solved.The values of the metal via radius, number, length, distribution radius, the radius of each level of the reverse pad and the radius of the circular pad involved in the multi-stage impedance joint matching structure in the present application need to meet the high-precision matching of the signal via 2-12 impedance according to full-wave simulation. In another embodiment of the present application, the radius of the first level of the reverse pad 3-1 is 0.74mm-0.76mm, the radius of the second level of the reverse pad 3-2 is 0.724mm-0.726mm, the radius of the third level of the reverse pad 3-3 is 0.370mm-0.380mm, and the radius of the signal via pad 3-4 is 0.23mm-0.27mm.

[0035] In the present application, an isosceles tapered ladder transmission structure 2-3 is used to smoothly connect the detection end 2-1 and the output end 2-8 of the magnetic field probe. The isosceles tapered ladder transmission structure 2-3 is located at the transmission end 2-4 of the magnetic field probe. The isosceles tapered ladder transmission structure 2-3 has an overall isosceles trapezoidal shape with a wide top and a narrow bottom. The waist line is a smooth straight line, and the bottom angle formed by the waist line and the lower horizontal side is greater than 90° and less than 180°. The bottom angle is determined by the ratio of the widths of the upper and lower horizontal sides and the parallel distance. The isosceles tapered ladder transmission structure 2-3 has a simple implementation and effectively suppresses the common-mode surface current generated by the structural discontinuity between the detection end 2-1 and the output end 2-8 of the magnetic field probe at a low cost, reduces the energy loss of the desired signal during transmission, and thus increases the output signal of the magnetic field probe. The physical size of the isosceles tapered ladder transmission structure 2-3 is determined by full-wave simulation optimization. The simulation process focuses on the distribution of surface current at the corresponding frequency points of the ringing and surge waveforms. The physical size of the isosceles tapered ladder transmission structure 2-3 is dynamically adjusted according to the distribution characteristics of the surface current. In one embodiment of the present application, the ratio of the widths of the upper and lower horizontal sides of the isosceles tapered ladder transmission structure 2-3 is 7.5, and the parallel distance between the upper and lower horizontal sides is 48mm.

[0036] Three non-metal mounting holes 2-6 are opened at the mechanical connection end 2-7 of the magnetic field probe. The center of the middle non-metal mounting hole 2-6 is located on the symmetry axis of the inverted "convex" window, ensuring that the magnetic field probe can rotate around the center of the inverted "convex" window 2-2.

[0037] Figure 5 A coaxially rotatable broadband low-cost magnetic field probe clamp structure, Figure 6The schematic diagram of a coaxial rotatable magnetic field measuring device is shown. The magnetic field probe clamp 4-2 is composed of a first rectangular pressing block 3-8, a second rectangular pressing block 3-9 and a cylindrical block 3-7. The cylindrical block 3-7 and the second rectangular pressing block 3-9 are physically integrated and inseparable. The first rectangular pressing block 3-8 and the cylindrical block 3-7 are physically separable. The cylindrical block 3-7 is provided with a top connecting hole 3-6 for connecting with a micrometer 4-3. Three non-metal mounting holes 2-6 of the same physical size are formed in the first rectangular pressing block 3-8, and the middle non-metal mounting hole 2-6 is coplanar with the symmetry plane of the cylindrical block 3-7. The mechanical connecting end 2-7 of the magnetic field probe 4-1 is mounted between the first rectangular pressing block 3-8 and the second rectangular pressing block 3-9. After the three non-metal mounting holes 2-6 of the first rectangular pressing block 3-8 are aligned with the non-metal mounting holes 2-6 of the magnetic field probe 4-1, the magnetic field probe 4-1 is fixed on the magnetic field probe clamp 4-2 by screws.

[0038] The magnetic field probe clamp 4-2 is connected with the micrometer 4-3, the micrometer 4-3 is connected with the hollow rotating table 4-5 through the metal connecting rod 4-4, and the hollow rotating table 4-5 is installed on the three-dimensional mechanical arm 4-6. The metal connecting rod 4-4 is located at the center of the hollow rotating table 4-5, the hollow rotating table 4-5 contains one motor, and the rotation in the horizontal direction at any angle can be realized, the three-dimensional mechanical arm 4-6 contains three motors, and the position movement in the three-dimensional space can be realized. The driver module 4-8 is connected with the three-dimensional mechanical arm 4-6 and the hollow rotating table 4-5 through the 4-7 driving cable, the controller module 4-10 is connected with the driver module 4-8 through the control cable 4-9, and the computer 4-11 is connected with the controller module 4-10 through the RS485 cable 4-12. The host computer software is installed on the computer 4-11, the friendly man-machine interaction between the tester and the host computer software can be realized, the controller module 4-10 contains a read register and a write register, and MODBUS485 protocol is followed, the tester can convert the setting instructions (motion speed, motion direction, motion displacement, motion step, rotation angle, angle step, rotation direction) of the host computer into a square wave, and the driver module 4-8 drives the hollow rotating table 4-5 to rotate and the three-dimensional mechanical arm 4-6 to move after power amplification of the converted square wave. In one embodiment of the application, the controller module 4-10 has 14 input channels and 8 output channels, the power supply voltage of the controller module 4-10 is 5V, and the power supply voltage of the driver module 4-8 is 24V. The register for executing the fixed-length motion of the controller module 4-10 is a 32-bit write-only register, the register address 20D (D represents the decimal counting method) is the motion speed, the unit of the written value is mm / min, the register address 22D and the register address 24D are the motion increments of the x-axis and the y-axis respectively, and the unit of the written value is micrometer. Assuming that the x-axis and the y-axis of the three-dimensional mechanical arm 4-6 move forward and backward respectively at the speed of 1000D mm / min, the command written by the host computer to the microcontroller is 01 10 00 14 00 060C 03E8 00 00 27 10 00 00 D8 F0 FF FF 15 63 (the above command is expressed in hexadecimal method).

[0039] Figure 7The simulation and test results of the frequency response of a coaxial rotatable wideband low-cost magnetic field probe before coaxial rotation and after coaxial rotation by 90 degrees. The simulation and test results before rotation show that the magnetic field probe has a high gain value in the low frequency band, can reach the average gain value at 3GHz, has stable amplitude in the medium and high frequency band, has no resonance, obvious ringing wave and surge wave, the effective working frequency band is 9kHz-20GHz, the gain fluctuation in the working frequency band is not more than 2dB, the average fluctuation in the 4GHz-17GHz frequency band is about 1.25dB, and the test result curve and the simulation result curve have high coincidence degree. The magnetic field measuring device disclosed by the application can realize magnetic field measurement in any direction of the horizontal direction, Figure 8 The simulation and test results of the cross polarization of a coaxial rotatable wideband low-cost magnetic field probe. The simulation results and test results of 5GHz and 10GHz are good in consistency, which shows that the coaxial rotatable magnetic field measuring device disclosed by the application has high test precision and stability.

[0040] It should be pointed out that the technical means, design method disclosed by the application are not only limited to the application, but also suitable for other schemes, invention methods, invention products derived from the design idea, invention method, technical means of the application and the technical features described in the application, so these derived other schemes, invention methods, invention products should be regarded as the protection range of the application.

Claims

1. A coaxially rotatable broadband low-cost magnetic field probe, characterized by: The magnetic field probe is prepared by using low-cost FR-4 material and conventional four-layer printed circuit technology, and the four-layer printed circuit board is sequentially composed of a top layer, a first prepreg, a middle 1 layer, a substrate, a middle 2 layer, a second prepreg and a bottom layer from top to bottom; the magnetic field probe comprises at least a shielding ring, an isosceles tapered ladder transmission structure, a fence type isolation via array, a non-metal mounting hole, a 50Ω strip line, a multi-stage impedance joint matching structure and a side-inserted micro coaxial RF connector; the shielding ring and the fence type isolation via array are located at the detection end of the magnetic field probe, the 50Ω strip line and the isosceles tapered ladder transmission structure are located at the transmission end of the magnetic field probe, the multi-stage impedance joint matching structure and the side-inserted micro coaxial RF connector are located at the output end of the magnetic field probe, and the non-metal mounting hole is located at the mechanical connection end of the magnetic field probe; the top layer and the bottom layer are provided with an inverted "convex" type window in the detection end area, and the fence type isolation via array is located above the inverted "convex" type window; the isosceles tapered ladder transmission structure is in the shape of an isosceles trapezoid with the width increasing from top to bottom, the waist line is a smooth straight line, the bottom angle formed by the waist line and the lower horizontal side is greater than 90° and less than 180°, and the bottom angle is determined by the ratio of the width of the upper horizontal side to the lower horizontal side and the parallel distance; the multi-stage impedance joint matching structure is composed of a coaxial via array, a signal via, a first reverse pad, a second reverse pad, a third reverse pad and a signal via pad; in the top layer, the middle 1 layer, the bottom layer, the first reverse pad, the second reverse pad and the third reverse pad are respectively constructed by digging circular copper with different radii around the signal via as the center, and the signal via pad is constructed by covering circular copper around the signal via in the top shielding layer.

2. A coaxially rotatable, wideband, low-cost magnetic field probe according to claim 1, characterized in that: The center conductor of the 50Ω strip line is located in the middle 2 layer, and the impedance reference planes are the middle 1 layer above and the bottom layer below.

3. A coaxially rotatable, wideband, low-cost magnetic field probe according to claim 1, characterized in that: The fence type isolation via array is composed of metal vias arranged at equal intervals, and all the metal vias connect the top layer and the bottom layer.

4. A coaxially rotatable, wideband, low-cost magnetic field probe according to claim 1, characterized in that: The radii of the first reverse pad, the second reverse pad and the third reverse pad decrease in turn.

5. A coaxial rotating magnetic field measuring device, characterized by: The magnetic field probe, a magnetic field probe clamp, a micrometer, a metal connecting rod, a hollow rotating table, a three-dimensional mechanical arm, a driver module, a controller module and a computer are included; the magnetic field probe is fixed to the micrometer by the magnetic field probe clamp, the micrometer is connected to the hollow rotating table through the metal connecting rod, the hollow rotating table is installed on the three-dimensional mechanical arm by screws, and is driven by the driver module and controlled by the controller module, so as to realize accurate coaxial rotation and three-dimensional space movement of the magnetic field probe in the horizontal direction.

6. A coaxial rotating magnetic field measurement device according to claim 5, characterized in that: The magnetic field probe clamp is composed of a cylindrical block, a first rectangular pressing block and a second rectangular pressing block, the second rectangular pressing block is physically inseparable from the cylindrical block, the first rectangular pressing block is physically separable from the second rectangular pressing block, and the first rectangular pressing block is also provided with a non-metal mounting hole.

7. A coaxial rotating magnetic field measuring device according to claim 5, characterized in that: The computer is installed with host computer control software, which is used for sending setting operation instructions to the controller module, so as to realize friendly human-computer interaction.

8. A coaxial rotating magnetic field measuring device according to claim 5, characterized in that: The computer and the controller module communicate through an RS485 interface, the controller module and the driver module are connected through a control cable, the driver module is connected with the hollow rotating table and the three-dimensional mechanical arm through a driving cable; the read and write registers in the microcontroller of the controller module follow the MODBUS485 protocol, can convert the setting instructions of the host computer into square waves, and the driver module drives the hollow rotating table to rotate and the three-dimensional mechanical arm to move after power amplification of the converted square waves.

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