Device comprising a magnetic field generator, and method for providing a coil arrangement

Abstract

The invention relates to a device comprising at least one magnetic field generator, which in turn comprises a coil arrangement with multiple coils that have multiple windings each. The invention further relates to a method for providing a coil arrangement for such a device.

Description

[0001] Device with a magnetic field generator and method for providing a coil arrangement

[0002] The invention relates to a device comprising at least one magnetic field generator having a coil arrangement with a plurality of coils, each having a plurality of turns. The invention also relates to a method for providing a coil arrangement for such a device.

[0003] The device is intended to be particularly suitable for testing, characterizing, and / or calibrating magnetic field sensors. It is known to use permanent magnets or very large coil arrangements for this purpose, such as a Helmholtz coil or a cylindrical coil surrounding the magnetically sensitive element of a magnetic field sensor.

[0004] However, existing devices are relatively inflexible in their application possibilities and, in some cases, very space- and cost-intensive. Furthermore, generating reproducible, homogeneous magnetic fields in such arrangements is problematic.

[0005] The invention is based on the object of providing an improved device with at least one magnetic field generator that overcomes the aforementioned disadvantages. Furthermore, a method for providing a coil arrangement for such a device is to be provided.

[0006] This object is achieved by a device comprising at least one magnetic field generator having a coil arrangement with a plurality of coils, each having a plurality of turns, wherein the coil arrangement has a first planar coil layer with at least one coil and a second planar coil layer arranged parallel thereto with at least one coil, wherein the second planar coil layer is arranged at a distance from the first planar coil layer, wherein the coil arrangement is configured, when the coil arrangement is electrically energized, to generate a parallel magnetic field on the side of the first coil layer facing away from the second coil layer at a distance from the first coil layer, which parallel magnetic field has magnetic field lines parallel to the first coil layer. The parallel magnetic field is thus a magnetic field directed tangentially to the plane of the first planar coil layer.

[0007] The second planar coil layer can thus be arranged in a plane parallel to the plane of the first planar track layer, and thus not in the same plane. For example, the coils of the first and second planar track layers can have their planar extension in the x- and y-coordinate directions. The second planar track layer is then slightly offset from the first planar track layer in the z-direction. The coils of the first planar track layer can be arranged so as to overlap the tracks of the second planar track layer.

[0008] Such a coil arrangement with a first and a second planar coil layer can be provided relatively easily and inexpensively, e.g., by means of conductor tracks in corresponding conductor track layers of a printed circuit board (PCB). Furthermore, the aforementioned design of the coil arrangement allows a relatively homogeneous magnetic field directed in a desired direction to be generated outside the area surrounded by the coil layers, i.e., the magnetic field sensor does not need to be arranged between the coil layers.

[0009] For example, the desired parallel magnetic field can be generated at a distance from the first coil layer that is at least 50% of the distance between the first coil layer and the second coil layer. As mentioned, the first coil layer and the second coil layer are designed as planar coil layers, i.e., the invention implements planar coils whose coil turns are thus arranged in a plane. For example, the first planar coil layer can have two coils. The second planar coil layer can have two coils.

[0010] The invention allows for the advantageous, relatively cost-effective generation of directed and homogeneous magnetic fields in the sensitive plane of a magnetic field sensor without the need for wire-wound coils. The coil arrangement of the magnetic field generator according to the invention can therefore be implemented in a relatively small design, e.g., on an electrical circuit board. Compared to the use of permanent magnets, the invention has the advantage that by controlling the current supply to the coil arrangement, the magnetic field can be adjusted as desired and can be changed as desired during operation of the device. The parallel magnetic field generated by the magnetic field generator can be used to characterize a magnetic field sensor, to adjust its operating point, and / or to compensate for external fields.

[0011] A further advantage of the invention is that the coils of the coil arrangement can be manufactured cost-effectively and reproducibly, e.g., by using existing, widespread, and established manufacturing techniques, such as the manufacture of electrical circuit boards. Advantageously, a generally unused space on the circuit board can be used to accommodate the coil arrangement, with the circuit board otherwise serving as a support and protection for the magnetic field sensor. This makes it possible to provide a dedicated, stable coil system associated with the magnetic field sensor, which is suitable for system calibration and characterization. A device with such a magnetic field generator can be realized with a coil design that is particularly robust against external interference fields.

[0012] The device according to the invention can be used to characterize and calibrate a magnetic field sensor. It is also possible to exert a desired influence on its behavior during operation, e.g., by influencing the sensor characteristic curve through the parallel magnetic field and its control.

[0013] The coil arrangement can be designed with only two external connections via which an electrical current can be fed to the coil arrangement.

[0014] According to an advantageous embodiment of the invention, the at least one coil of the first coil layer has a winding direction opposite to that of the at least one coil of the second coil layer. This allows a parallel magnetic field to be generated in a particularly advantageous manner outside the area surrounded by the first and second coil layers, i.e., beyond the coil arrangement.

[0015] According to an advantageous embodiment of the invention, the coils of the first coil layer and / or the second coil layer are formed by conductor tracks of a printed circuit board (PCB). The conductor tracks form coil-like conductor loops. This enables a simple, reproducible, cost-effective, and robust implementation of the coil arrangement. According to an advantageous embodiment of the invention, the printed circuit board has multiple conductor track layers, wherein the first coil layer is formed on a first conductor track layer (conductor layer) and the second coil layer is formed on a second, spaced-apart conductor track layer. In this case, it is sufficient to use a printed circuit board with two conductor track layers, for example, a printed circuit board coated on both sides with conductor track material.The first coil layer can then be implemented on one conductor layer of the circuit board, and the second coil layer on the other conductor layer. In a two-layer circuit board, the distance between the first and second coil layers essentially corresponds to the thickness of the circuit board. It is also possible to use multilayer circuit boards. For example, a circuit board with four conductor layers can be used. In this case, the conductor layers arranged inside the circuit board can be used to create the coil arrangement.

[0016] According to an advantageous embodiment of the invention, conductor tracks of the first coil layer are connected to conductor tracks of the second coil layer by one or more through-contacts (vias). In this way, a relatively complex coil system can be implemented simply and cost-effectively using printed circuit board technology.

[0017] According to an advantageous embodiment of the invention, the first coil layer has a greater spacing between turns of the at least one coil in the region covered by the parallel magnetic field than outside the region covered by the parallel magnetic field. This ensures a high degree of homogeneity of the parallel magnetic field. If the turns are implemented as conductor tracks, the first coil layer has a greater spacing between conductor tracks in the region covered by the parallel magnetic field than outside the region covered by the parallel magnetic field.

[0018] According to an advantageous embodiment of the invention, the second coil layer has concavely curved windings or conductor track sections that directly border the area covered by the parallel magnetic field. In this way, the conductor tracks can be routed around the area of ​​the coil arrangement covered by the parallel magnetic field. This also ensures particularly good homogeneity of the parallel magnetic field.

[0019] According to an advantageous embodiment of the invention, the device has at least one magnetic field sensor, in particular a magnetic field sensor using thin-film technology, with a magnetically sensitive element that is arranged in the region of the parallel magnetic field. In this way, an integrated device can be realized that has both a magnetic field sensor and a magnetic field generator associated with the magnetic field sensor. The magnetic field sensor can be measured and / or calibrated using the magnetic field generator. The magnetic field generator can also influence the sensor properties of the magnetic field sensor during ongoing operation, e.g., by changing the characteristic curve of the magnetic field sensor in a desired manner by controlling the parallel magnetic field.

[0020] The object stated at the outset is also achieved by a method for providing a coil arrangement of a device of the type explained above, with the following steps: a) determining the installation space available for the coil arrangement, b) determining a desired area in which the parallel magnetic field is to be generated by the coil arrangement, c) arranging the conductor tracks of the first coil layer and the second coil layer on a circuit board, special virtual arrangement of the conductor tracks in a CAD program, d) simulating the magnetic field that can be generated by the coil arrangement with a check as to whether the parallel magnetic field meets the specified requirements, e) if the requirements are not met, continuing the process in step c), otherwise terminating the process.

[0021] This also allows the previously discussed advantages to be realized. In particular, it can provide a coil arrangement for a magnetic field generator that can generate a very homogeneous and relatively strong parallel magnetic field in the desired area.

[0022] According to an advantageous embodiment of the invention, the following sub-steps are carried out in step c): c1) distributing the conductor tracks in the first and second coil layers, c2) determining the coil center distance and core diameter, c3) connecting the conductor tracks to form coil-like conductor loops.

[0023] This allows the homogeneity of the parallel magnetic field to be further improved or iteratively optimized. According to an advantageous embodiment of the invention, after step c) and before step d), a check is carried out to determine whether the distribution of the conductor tracks in the second coil layer is sufficiently suitable for the specified generation of the parallel magnetic field. If this is not the case, the defined core diameter is increased and step c2 is continued; otherwise, step d) is continued. In this way, the coil arrangement and thus the magnetic field generator can be iteratively optimized for the desired application. For example, a software simulation of the expected parallel magnetic field can be carried out to carry out the method step, and optimization can be carried out on the computer in one or more iterative steps during the coil design.

[0024] The invention is explained in more detail below using exemplary embodiments and drawings:

[0025] It shows

[0026] Figure 1 - a magnetic field generator in perspective view,

[0027] Figure 2 - the magnetic field generator according to Figure 1 with a magnetic field sensor,

[0028] Figure 3 - a side sectional view through the device according to Figure 2 showing the magnetic field,

[0029] Figure 4 - Coils of a coil arrangement of the magnetic field generator according to Figure 1 in plan view,

[0030] Fig. 5, 6 - Dimensioning options of the coils according to Figure 3,

[0031] Figure 7 - the sequence of a method for providing a coil arrangement according to Figure 3.

[0032] Figure 1 shows a device 1 with a magnetic field generator 2, which has a coil arrangement with a plurality of coils 3, 4, 5, 6. The coils 3, 4, 5, 6 are designed as planar coils with a plurality of turns 7. The coils 3, 4 are located in a first planar coil layer 12, i.e. in the same plane, and the coils 5, 6 are located in a second planar coil layer 13 arranged parallel to the first coil layer 12, thus in a plane parallel to the coil layer 12. The coils 3, 4 are connected to one another via a line. The coil 3 is connected to the coil 5 via a via 8. The coil 4 is connected to the coil 6 via a via 8. The coil arrangement 2 has two external connections 9, via which an electrical signal can be applied to the coil arrangement 2, which flows through the coils 3, 4, 5, 6.As a result, a parallel magnetic field can be generated on the side of the first coil layer 12 facing away from the second coil layer 13, which parallel magnetic field has magnetic field lines parallel to the first coil layer 12.

[0033] Figure 2 shows the combination of device 1 with coil arrangement 2 and a magnetic field sensor 10 having a magnetically sensitive element 11. The magnetically sensitive element 11 is arranged in the region of the parallel magnetic field generated by coil arrangement 2.

[0034] Figure 3 illustrates this using a side sectional view. The coils 3, 4 in the first coil layer 12 and the coils 5, 6 in the second coil layer 13 are visible. The vias 8 are also visible. The magnetic field sensor 10 with the magnetically sensitive element 11 is arranged above the first coil layer 12. The arrows indicate the course of the magnetic field lines. The aforementioned parallel magnetic field 14 is generated above the first coil layer 12. The x and y components of the magnetic field lines in the region of the parallel magnetic field 14 run relatively homogeneously and are also parallel to the plane of the first coil layer 12 and, accordingly, also tangential to the longitudinal extent of the magnetically sensitive element 11.

[0035] Figure 4 illustrates an advantageous design of coils 3, 4, 5, and 6, as well as an advantageous connection option between these coils. Coils 3, 4, 5, and 6 are connected in series. Coil 6 is connected to coil 4 at connection point B via a through-hole. Coil 3 is connected to coil 5 at connection point D via a through-hole. Coils 3 and 4 are connected to each other at connection points C, either directly or via a conductor track in the same coil layer. Connection points A and E are connected to external terminals 9.

[0036] Coils 5, 6 in the second (lower) coil layer 13 ensure the highest possible magnetic field strength and, accordingly, sensitivity. Coils 3, 4 in the first (upper) coil layer 12 direct the magnetic field into a tangential plane to the first coil layer or to an electrical circuit board in which the first and second coil layers are implemented, and establish a homogeneous field distribution in the region of the parallel magnetic field 14.

[0037] With reference to the characteristics of coils 3, 4, 5, and 6 shown in Figures 5 and 6, the following advantageous method for dimensioning the coils using conductor tracks on a printed circuit board is proposed. The following relevant dimensions must be observed:

[0038] Xmax: maximum available installation space in x-direction (field direction of the parallel magnetic field 14) ymax: maximum available installation space in y-direction dmin: minimum radius of an inner conductor loop Vx: coil center distance in x-direction v y : core diameter of a coil pair pmin: minimum conductor track spacing to be realized pto P : Distance between the inner conductor tracks of coils 3, 4 (coil top) pbottom: Distance between the inner conductor tracks of coils 5, 6 (coil bottom)

[0039] Design and dimensioning of the coils:

[0040] 1. The dimensions Xmax and ymax indicate the total installation space occupied by the coils. This should be selected as large as possible. A high number of turns, which can be achieved within a large installation space, is advantageous in terms of field homogeneity and the maximum achievable field strength.

[0041] 2. Vx and v ydenotes the coil center distance of a coil pair or the core diameter of a single coil. The largest possible v y reduces the field gradient in the y-direction. It should be selected at least large enough to ensure that all line sections below the desired field level run without bends. x should be at least 1.7 times the length of the desired field level. Furthermore, Vx > (ymax - v y ). A larger distance is advantageous in terms of homogeneity.

[0042] 3. dmin is the minimum diameter, or twice the minimum radius, of the innermost conductor loop. This is determined by the PCB technology used and the specifications of the PCB manufacturer. The limiting factor here is usually the minimum distance between a via used to connect the upper and lower coils and a conductor path passing by it. A small dmin leads to more effective use of the available installation space.

[0043] 4. The track spacing pmin is determined by the PCB manufacturer's design specifications and the selected track width. The track width (not specified in this drawing) should be as large as necessary to achieve low ohmic resistance in the coil, but also as small as possible to achieve the maximum number of turns.

[0044] 5. The conductor spacing pbottom should be equal to pmin for a maximally homogeneous magnetic field. A minimal increase in pbottom results in an increase in the maximum achievable field in the desired field plane, with only a slight deterioration in homogeneity.

[0045] 6. ptop must be chosen so that the conductors are evenly distributed over the free area. If n is the number of turns per individual coil, then ptop = (Vx+dmin) / (2n+1) .

[0046] 7. The distance between the upper coil (coil top) and the lower coil (coil bottom) is determined by the selected PCB technology (not specified in this drawing). However, the distance should be approximately equal to that between the upper coil and the desired field plane of the parallel magnetic field 14.

[0047] 8. All unspecified conductor tracks should be designed with a focus on minimum line length and maximum symmetry of the entire coil structure.

[0048] An advantageous method for providing such a coil arrangement 2 can proceed as follows, as shown in Figure 7.

[0049] In step 70, the available installation space can first be defined. The installation space should be as large as possible. It directly influences the number of coil turns to be implemented and thus also the achievable field strength and field homogeneity. The available installation space on the circuit board must be taken into account, especially when implementing on a circuit board.

[0050] In a subsequent step 71, a target area can be defined. The target area is the area in which the parallel magnetic field to be generated tangentially to the circuit board surface should be generated during the coil arrangement and should be as homogeneous as possible. For example, the areas 80 can be defined as the target area, which are, so to speak, a projection of the parallel magnetic field to be generated into the areas of the planar coil layers.

[0051] In a step 72, the conductor tracks are then distributed on the circuit board in the coil planes, i.e., in the first coil layer and the second coil layer. It is advantageous to place the outer conductor tracks as closely together as possible in the first coil layer. The inner conductor tracks should utilize the available space evenly. Furthermore, it is advantageous to place all conductor tracks as far as possible on the outer sides in the second coil layer and to substantially not cover the target area 80.

[0052] In a step 73, the coil center-to-center distance and core diameter are then determined. The maximum values ​​for the coil center-to-center distance and core diameter are defined by the conductor track width, the conductor track spacing, and the number of coil turns. In addition, areas 81 can already be reserved for the vias 8.

[0053] In a step 74, the conductor tracks are connected to form conductor loops. As can be seen, in the first coil layer, the conductor loops can at least partially cover the target area 80. In the second coil layer, the conductor loops are formed in such a way that the target area 80 is essentially left out. In this way, for example, two eyeglass-like coils can be created in the second coil layer 13. In general, the conductor tracks should be connected to form conductor loops using the shortest possible route. The connection is made using circular tracks and conductor tracks at a 45-degree angle.

[0054] In a step 75, the conductor tracks are then distributed across the coil planes, i.e., the first coil layer and the second coil layer. For example, the conductor loop geometry in the second coil layer can be evaluated: If no or only very short straight conductor tracks are present, so that the target area 80 is excessively covered, the core diameter can be increased, for example.

[0055] In a step 76, it is checked whether the geometry in the second coil layer is suitable for meeting the requirements of the parallel magnetic field 14 to be generated. If this is not the case, the process continues with step 73, e.g., by increasing the core diameter in the second coil layer 13.

[0056] Otherwise, the process continues after step 76 with step 77. There, the magnetic field resulting from energizing the coil arrangement, at least in the X-direction, can be checked by simulation. For example, relevant evaluation criteria for the suitability of the resulting magnetic field can be the homogeneity of the magnetic field in the plane of the desired parallel magnetic field, i.e., in the target range, as well as the sensitivity of the coil arrangement relative to the target range in T / A. In a step 78, the parameters determined from the simulation are checked, for example, whether the homogeneity and the sensitivity reach the desired values. If this is not the case, the process branches back to step 72. For example, the homogeneity of the magnetic field can then be improved by changing the number of turns and / or the coil center distance. If the field strength is insufficient, e.g.a change in the number of turns and / or the conductor spacing in the second coil layer.

[0057] If it is determined in step 78 that the desired criteria are met, the process continues with step 79. There, the conductor loops are connected to form a coil system, i.e., to the finished coil arrangement 2, as shown in Figure 1. The conductor loops can, for example, be connected in such a way that the impairment of symmetry is as minimal as possible. The four individual coils are then connected in series. These steps can be performed entirely or at least partially in a circuit board design program.

Claims

Patent claims:

1. A device comprising at least one magnetic field generator (1) having a coil arrangement (2) with a plurality of coils (3, 4, 5, 6), each having a plurality of turns (7), wherein the coil arrangement (2) has a first planar coil layer (12) with at least one coil (3, 4, 5, 6) and a second planar coil layer (13) arranged parallel thereto with at least one coil (3, 4, 5, 6), wherein the second planar coil layer (13) is arranged at a distance from the first planar coil layer (12), wherein the coil arrangement (2) is configured, when the coil arrangement (2) is energized electrically, to generate a parallel magnetic field (14) on the side of the first coil layer (12) facing away from the second coil layer (13) at a distance from the first coil layer (13), which parallel magnetic field has magnetic field lines parallel to the first coil layer (12).

2. Device according to claim 1, characterized in that the at least one coil (3, 4, 5, 6) of the first coil layer (12) has an opposite winding direction to the at least one coil (3, 4, 5, 6) of the second coil layer (13).

3. Device according to one of the preceding claims, characterized in that the coils (3, 4, 5, 6) of the first coil layer (12) and / or the second coil layer (13) are formed by conductor tracks (15) of a printed circuit board (PCB).

4. Device according to claim 3, characterized in that the printed circuit board has a plurality of conductor track layers, wherein the first coil layer (12) is formed on a first conductor track layer and the second coil layer (13) is formed on a second conductor track layer spaced therefrom.

5. Device according to one of claims 3 to 4, characterized in that conductor tracks (15) of the first coil layer (12) are connected to conductor tracks (15) of the second coil layer (13) by one or more through-contacts (8) (vias).

6. Device according to one of the preceding claims, characterized in that the first coil layer (12) has a greater distance between turns (7) of the at least one coil (3, 4, 5, 6) in the area covered by the parallel magnetic field (14) than outside the area covered by the parallel magnetic field (14).

7. Device according to one of the preceding claims, characterized in that the second coil layer (13) has concavely curved windings (7) or conductor track sections which directly border on the area covered by the parallel magnetic field (14).

8. Device according to one of the preceding claims, characterized in that the device has at least one magnetic field sensor (10), in particular a magnetic field sensor using thin-film technology, with a magnetically sensitive element (11) which is arranged in the region of the parallel magnetic field (14).

9. Method for providing a coil arrangement (2) of a device according to one of the preceding claims, with the following steps: a) determining the installation space available for the coil arrangement (2), b) determining a desired area in which the parallel magnetic field (14) is to be generated by the coil arrangement (2), c) arranging the conductor tracks (15) of the first coil layer (12) and the second coil layer (13) on a printed circuit board, d) simulating the magnetic field that can be generated by the coil arrangement (2) with a check as to whether the parallel magnetic field (14) meets the stated requirements, e) if the requirements are not met, continuing the process in step c), otherwise terminating the process.

10. Method according to claim 9, characterized in that in step c) the following sub-steps are carried out: c1) Distributing the conductor tracks (15) in the first and second coil layers (12, 13), c2) Determining the coil center distance and core diameter, c3) Connecting the conductor tracks (15) to form coil-like conductor loops.

11. The method according to claim 9 or 10, characterized in that after step c) and before step d) it is checked whether the distribution of the conductor tracks (15) in the second coil layer (13) is sufficiently suitable for the predetermined generation of the parallel magnetic field (14), and if this is not the case, enlarging the defined core diameter and continuing in step c2), otherwise continuing in step d).

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