FIELD OF THE INVENTION

The present invention relates to a magnetic field generator for providing one or more specific magnetic waveforms and/or magnetic intensities. Further, the present invention relates to a device including a number of magnetic field generators.

BACKGROUND OF THE INVENTION

There are technical applications in which the generation ofa broad-frequency magnetic field is desirable.

Broad-frequency magnetic fields are required in numerous test-and-measurement applications, for example in scientific experiments where oftentimes a high magnetic field strength is needed. But also in medical sciences where the effect of magnetic fields on living cells is investigated. Such broad-frequency magnetic fields are also used in probe calibrations, magnetic field accumulators and EM shielding of electronic products.

Another example is audio technology, where class A or B linear amplifiers apply a voltage signal to the loudspeaker coil. There is, however, a phase shift (-90°) between the applied voltage and the current that eventually passes through the coil. As the coil is not an ideal inductor due to the coil wire having some resistance, the phase shift between the applied voltage and the current through the coil varies with frequency. For this reason, loudspeaker coils should be driven by a current signal, and not by a voltage signal. A current driver that drives a loudspeaker coil such that it generates a broad-frequency magnetic field is highly desirable in terms of loudspeaker performance and audible pleasure.

Further, in medical technology it is known that at least some diseases, particularly if they are triggered by pathogens, such as bacteria, parasites, fungi, viruses, etc., which may be built from proteins, DNA, cells, etc., in a human or animal body may be treated by a broad- frequency magnetic field. This may affect proteins, DNA, cells, etc., in order to weaken or kill the pathogen. Technically, however, it is a challenge to provide a suitable magnetic field in a reliable way, since the requirements are high for both a coil that generates the magnetic field and controlling of the coil, for which an electric current at a desired frequency and/or level has to be generated.

SUMMARY OF THE INVENTION

There may, therefore, be a need for providing an improved means for providing a broad-frequency magnetic field. The object of the present invention is solved by the subject matter of the independent claims. Preferred or optional features are indicated in the dependent claims.

According to a first aspect of the present invention, there is provided a magnetic field generator for providing one or more specific magnetic waveforms and/or magnetic intensities. The magnetic field generator comprises: a controller, comprising a pulse-width modulation (PWM) generator configured to generate a number of PWM signals corresponding to a control program comprising information on the one or more specific magnetic waveforms and/or magnetic intensities to be provided; an electronic switching circuit, comprising a number of switches connected to the controller to receive the number of PWM signals and configured to be selectively switched on and off to generate an electric current, caused by the number of PWM signals, through the electronic switching circuit; and a coil assembly comprising a number of conductive coils stacked in a layer-by-layer fashion and mounted on a printed circuit board, PCB, wherein adjacent coils are insulated from one another by an intermediate insulating layer; at least one of the conductive coils of the coil assembly is connected to the number of switches of the H-bridge and configured to be driven by the electric current and to generate, in response to the electric current, the one or more specific magnetic waveforms and/or magnetic intensities to be provided.

In this way, the magnetic field generator may provide a broad-frequency magnetic field. Further, this configuration allows a high-power efficiency, a high frequency magnetic spectrum, and requires merely few electrical components. Moreover, no additional support structure is needed for the coil assembly.

As used herein, the controller may be broadly understood as an arrangement of electrical and/or electronic components, such as a Field Programmable Gate Array (FPGA), a processor and/or microprocessor, a memory, data interfaces, etc., and/or software components that can perform control of the magnetic field generator based on at least the control program.

As used herein, the PWM generator may, for example, be implemented in a field programmable gate array (FPGA).

Further as used herein, the electronic switching circuit may be broadly understood as an electronic circuit configured to switch a polarity of a voltage applied to a load. Optionally, the number of PWM signals are voltage signals.

For example, the number of switches may be of a metal-oxide-semiconductor field- effect transistor (MOSFET) type.

For example, the magnetic waveform to be provided may be selected from square, DC, saw tooth, sine, triangle, and/or a combination thereof. Likewise, a waveform of the electric current driving the coil assembly and causing the magnetic field may be selected from square, DC, saw tooth, sine, triangle, and/or a combination thereof.

Optionally, the PWM generator may be further configured to selectively control, based on the control program, the number of switches to be switched on or off to generate, by applying the number of PWM signals, the electric current through at least one of the conductive coils or, alternatively, the coil assembly in a specific way according to the control program to generate the one or more specific magnetic waveforms and/or magnetic intensities to be provided. For example, the magnetic field generator may further comprise a number of switch drivers, connected to the PWM generator, and configured to switch the corresponding switch on or off in accordance with the PWM signals and/or the control program. In this way, the current flow can be switched and/or changed quickly by short switching times.

Optionally, the PWM generator may be further configured to alternately switch on or off, based on the control program, two switches of the number of switches arranged diagonally to each other at a time, thereby directing the electric current through at least one of the conductive coils, or alternatively the coil assembly in a specific way to generate the one or more specific magnetic waveforms and/or magnetic intensities to be provided. In this way, the current flow can be switched and/or changed quickly by short switching times.

Optionally, the PWM generator may be further configured to control, based on the control program, the number of switches to be switched on or off to establish a specific duty- cycle D of the number of PWM signals. Further optionally, the specific duty-cycle D may determine at least a signal shape of the electric current through the at least one conductive coil, or, alternatively, the coil assembly, thereby resulting in the one or more specific magnetic waveforms and/or magnetic intensities to be provided. The duty cycle D may be defined as a ratio between an active pulse and a PWM period, which may be expressed by

D = wherein ton is an active pulse time and Ts is a PWM period time.

The conductive coils of the coil assembly are stacked in a layer-by-layer fashion and mounted on a printed circuit board, PCB, wherein adjacent coils are insulated from one another by an intermediate insulating layer. Hence, the PCB, which is mechanically stable and can withstand thermal stress, can act as a support structure for the conductive coils with no other stabilizing and fixing structure being needed. To mount the conductive coils to the PCB, SMD technology or THT technology may be used. PCB technology is a somewhat well- developed and mature technology which allows to manufacture “clones” in a very efficient way and with high precision. Thus, the coil parameters of each conductive coil can be precisely controlled during manufacturing. Also important to note is the high predictability of the coil parameters, when using PCB technology. In particular, the parasitic capacitive and inductive parameters are known from the very beginning, which allows for precise theoretical simulations prior to manufacturing, as a result of which the coil parameters can be the same for each conductive coil. If needed, other electric and electronic components can be added in a controlled and very simple way.

According to an embodiment, the conductive coils of the coil assembly are connected in parallel, and the coil assembly is connected to the number of switches of the electronic switching circuit. Hence, all conductive coils of the coil assembly are connected to the number of switches of the electronic switching circuit, as a result of which the PWM voltage is equally applied to all conductive coils of the coil assembly. In addition, the coil assembly will remain fully operational even if one of the conductive coils should fail due to, for example, failure of an electrical contact.

In an embodiment, the number of conductive coils of the coil assembly are co- linearly arranged and mounted on the printed circuit board. In other words, the conductive coils are arranged side-by-side, with the insulating layer in between. In this way, the total magnetic flux density of the coil assembly equals the sum of the magnetic flux densities through each conductive coil.

In an embodiment, each conductive coil of the coil assembly is spirally wound in a layer plane. In other words, the windings of each conductive coil are not arranged side-by- side as in cylindrical coils, but one above the other. For example, the coil windings may be made from copper. In this way, each conductive coil may have a low inductivity, thereby further improving the broad-frequency magnetic field. Further, each conductive coil may have high rigidity due to the spiral structure, a minimized self-induction between the spirals, a self- resonance at high frequency, low parasitic capacity, and may be produced in a simple way. This type of conductive coil structure may also be referred to as planar-spiral type conductive coil.

In an embodiment, the shape of each of the number of coils of the coil assembly is selected from the group consisting of a circle, an ellipse, a spiral, a rectangle or a polygon. In this way, conductive coils may have varying shapes, not necessarily spiral, if needed.

Optionally, the number of conductive coils of the coil assembly is in a range of 2 to 15, preferably in a range of 5 to 13, most preferably amounts to 8. In this way, the number of conductive coils can be selected depending on the needed magnetic flux density.

In an embodiment, the thickness of each conductive coil of the coil assembly is in a range of 0.030 mm to 0.120 mm, preferably in a range of 0.060 mm to 0.090 mm, most preferably is 0.070 mm.

According to an embodiment, if each coil of the coil assembly has a circular shape, a diameter of each coil is in the range of 1 cm to 150 cm, preferably in the range of 15 cm to 50 cm, and most preferably of 17 cm, 25 cm or 50 cm. In this way, the coil may span a wide range of volumes, for example up to a volume sufficient to accommodate a human being inside the coil assembly, so that it is applicable for various applications, such as in audio technology, medical technology, etc.

In an embodiment, the coil assembly may have a time constant ts in the range of 5 ps to 15 ps, preferably in the range of 8 ps to 12 ps, further preferably of about 10 ps to 11 ps, and most preferably of 10,8 ps. For example, the time constant ts may be expressed by ts= -, wherein L is an inductivity of the coil assembly and R is its internal resistivity.

According to an embodiment, the coil assembly may have an inductivity L in the range of 20 pH to 90 pH, preferably in the range of 40 pH to 80 pH, further preferably of 65 pH. In this way, the coil may have a low inductivity, thereby further improving the broad- frequency magnetic field.

In an embodiment, the coil assembly may have a self-resonance frequency fr in the range of 4 MHz to 8 MHz, preferably in the range of 6 MHz to 7 MHz, further preferably of about 6,5 MHz, and most preferably of 6,525 MHz. The self-resonance of the coil assembly may be understood as the frequency when a complex impedance is maximum, the phase between the voltage and current changes and a behavior of the coil assembly turns form inductance to capacity.

According to an embodiment, the coil assembly may have a resistivity R in the range of 2 W to 10 W, preferably in the range of 4 W to 8 W, further preferably in range of 5 W to 7 W, and most preferably of 6 W.

Optionally, the coil assembly forms an applicator coil and/or a therapy coil, configured to be applied on or around a subject to provide the one or more specific magnetic waveforms and/or intensities to the subject. Thus, the number of possible practical applications of the system is increased. Furthermore, a specific therapy or treatment program can be applied to a patient using the coil assembly.

In an embodiment, the electronic switching circuit and the coil assembly may form a one-piece or integral applicator. For example, the applicator may be formed as a pad, electrode-like, etc. In this way, the magnetic field generator may be used for magnetic field therapy and/or treatment applications.

According to an embodiment, the magnetic field generator may form at least a part of a medical device, and wherein the one or more specific magnetic waveforms and/or intensities are to be provided to a subject.

As used herein, the subject to be exposed to the magnetic field, i.e. to the one or more magnetic waveforms and/or intensities, may be broadly understood, and may, for example, be a human or animal, a body thereof or a part of it. Alternatively, the subject may also be an in-vitro substance, e.g. a pathogen, an organism, or the like, such as one cultivated in a Petri dish, test tube, or the like, wherein the substance may be subjected to the magnetic field.

The medical device may be configured to apply the one or more specific magnetic waveforms and/or intensities to the subject for magnetic field treatment and/or magnetic field therapy.

According to an embodiment, the information on the one or more specific magnetic waveforms and/or magnetic intensities of the control program comprises a sequence of signal indicators indicating whether one or more signal parameters, used to generate the one or more specific magnetic waveforms and/or magnetic intensities to be provided, remain unchanged or are to be changed.

In other words, the magnetic field generator, e.g. the controller, receives only one or more signal parameters that describe the corresponding analog signal to be output by the signal source, instead of receiving the control program, e.g. therapy and/or treatment program, sample by sample, i.e. in sample by sample data. For example, the one or more signal parameters may comprise one or more of a signal shape or waveform, amplitude, frequency, and signal duration. The magnetic field generator may receive the control program, which may correspond to the therapy program to be applied to the subject, and may generate, based on the control program, a corresponding control signal to control the signal source to generate and/or output the corresponding analog signal. In this way, by utilizing only the signal parameters instead of sample by sample data, the amount of data to generate the analog signal may be reduced. In an embodiment, the medical device, e.g. the controller, and preferably the magnetic field generator, is further configured to provide the one or more signal parameters such that the signal parameters are provided with signal parameter information indicating over which application time the one or more signal parameters remain unchanged or are to be changed. In other words, the medical device utilizes only information of length of time with regard to changes or non-changes of the one or more signal parameters according to a predefined function, instead of also specifying the exact signal parameters for each time point. This mechanism may also be referred to as a time slot concept, in which the time slot is defined as the length of time that the one or more signal parameters remain unchanged or are changed according to a predefined function. Thereby, the time slot may be further defined or dimensioned with a length of time within which a reaction or response of the subject, i.e. the body or the substance, can be expected or even recognized, i.e. a reaction or response can be measured. By way of example, the time slot may have a length of time in the range of Milliseconds (ms), but is not limited thereto. In this way, the size of data files of the control program may be reduced, as it only comprises a reduced amount of information. In an embodiment, the one or more signal parameters are selected from: a time slot duration indicating that the signal parameter remain unchanged during the time slot duration, an amplitude of the electric current, an offset of the electric current, a frequency of the electric current, a duty cycle if the waveform of the electric current is square, and a waveform type.

According to an embodiment, the waveform type is selected from: sine, triangle, saw-tooth, square, DC, semi-periodical, pulse, cirp and sine. In this way, the magnetic field may have a broad-frequency spectrum.

In an embodiment, the controller may further comprise a signal generator, arranged upstream to and connected to the PWM generator, and configured to generate, based on the control program, a source signal, corresponding to the one or more specific magnetic waveforms and/or magnetic intensities to be provided, to be used by the PWM generator to generate the number of PWM signals. For example, the signal generator may be configured to generate a specified PWM duty cycle in order to obtain a signal shape of the electric current through the coil assembly that is suitable to provide the one or more specific magnetic waveforms and/or magnetic intensities.

In an embodiment, the electronic switching circuit may be an H-bridge.

According to a second aspect of the present invention, there is provided a device comprising a number of magnetic field generators, wherein each magnetic field generator defines a dedicated channel of the device, and wherein each channel is configured to provide one or more specific magnetic waveforms and/or intensities to a subject. In this way, each coil assembly can be driven independently from the other coil assemblies. As a result, if each coil assembly is driven with a specific PWM signal, and possibly with a specific phase shift relative to the other coil assemblies, or at least some of them, varying magnetic flux densities in a particular direction can selectively be created. This gives the operator of the device the possibility to selectively manipulate the magnetic flux densities along three axes, and not only two axes which would be the case if the totality of coil assemblies were driven with the same PWM signals. In an embodiment, the device includes at least two magnetic field generators each having a coil assembly, wherein the coil assemblies are spaced apart from one another along a longitudinal axis. If the spacing equals the radius R of the conductive coils of each coil assembly, a Helmholtz-coil configuration can be established. But by varying the spacing, magnetic flux densities can variably be changed.

In an embodiment, the device includes at least three magnetic field generators, each having a coil assembly, wherein the coil assemblies are spaced apart from one another along a longitudinal axis, and wherein a spacing between two adjacent coil assemblies varies along the longitudinal axis. In this way, the magnitude of the total magnetic flux density can be increased, and if the spacing of adjacent coils again equals the radius R of the coils, uniformity or homogeneity of the magnetic field is secured.

In an embodiment, the device includes a first and a second Helmholtz coil configuration, wherein the first Helmholtz coil configuration includes at least two first circularly- shaped coil assemblies which are spaced apart from one another along a first longitudinal axis, and wherein the second Helmholtz coil configuration includes at least two second circularly- shaped coil assemblies which are spaced apart from one another along a second longitudinal axis, and wherein a radius Ri of the first coil assemblies is smaller than a radius R ₂ of the second coil assemblies, and wherein the first longitudinal axis intersects the second longitudinal axis at a right angle. Such a two-axes (or even multiple-axes) arrangement of two (or even more) Helmholtz coil configurations can be used to selectively define a particular magnitude of magnetic flux density or magnetic resultant in a pre determined specified point-in-space. This greatly increases the number of conceivable practical, both medical and non-medical, applications of the system.

In an embodiment, the device is a medical therapy and/or treatment device.

It is noted that the above embodiments may be combined with each other irrespective of the aspect involved.

These and other aspects of the present invention will now become apparent from and will be elucidated with reference to the embodiments described and shown hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will be described in the following with reference to the drawings.

Fig 1 shows in a schematic circuit diagram a magnetic field generator according to an embodiment.

Fig. 2 shows schematically an exemplary magnetic field generated by a magnetic field generator according to an embodiment.

Fig. 3 shows schematically an exemplary coil assembly included in a magnetic field generator according to an embodiment.

Fig. 4 shows a cross-sectional view of the coil assembly of Fig. 3.

Fig. 5 shows a perspective view of an arrangement, according to a 1-axis Helmholtz coil configuration, of several coil assemblies included in a magnetic field generator according to an embodiment.

Fig. 6 shows a perspective view of an arrangement, according to a 2-axes Helmholtz coil configuration, of several coil assemblies included in a magnetic field generator according to an embodiment.

Fig. 7 shows a schematic block diagram of a medical device comprising a number of a magnetic field generators according to an embodiment.

Fig. 8 shows a schematic block diagram of a signal generator of a magnetic field generator according to an embodiment.

Fig. 9 shows a flow chart of a method for operating a medical device and/or a therapy and/or diagnostic device according to an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

Fig. 1 shows in a schematic circuit diagram an exemplary embodiment of a magnetic field generator 100, which is configured to provide one or more specific magnetic waveforms and/or magnetic intensities.

The term “number” used below may be broadly understood. If, for example, the description below uses the term “a number of coil assemblies”, it may refer to a single “coil assembly” or a plurality of “coil assemblies”.

The magnetic field generator 100 comprises a controller 110, which may be conceptually and/or functionally divided into one or more subunits, as indicated in the appended drawings by dashed rectangles. The controller 110 comprises a pulse-width modulation (PWM) generator 110-10 that is configured to generate a number of PWM signals PWM LH, PWM LL, PWM RH, PWM RL corresponding to a control program comprising information on the one or more specific magnetic waveforms and/or magnetic intensities to be provided. In other words, the magnetic field generator 100 is configured to provide a broad- frequency magnetic field.

Further, the magnetic field generator 100 comprises an electronic switching circuit, which may preferably be an H-bridge 120. The following description is based on a magnetic field generator 100 which comprises an H-bridge 120.

The H-bridge comprising a number of switches 120-10, 120-20, 120-30, 120-40 which are connected to the controller 110, e.g. the PWM generator 110-10, to receive the number of PWM signals PWM LH, PWM LL, PWM RH, PWM RL, wherein the number of switches 120-10, 120-20, 120-30, 120-40 is configured to be selectively switched on and off by the PWM generator 110-10 to generate an electric current, which is caused by the number of PWM signals PWM LH, PWM LL, PWM RH, PWM RL, through the H-bridge 120

Further, the magnetic field generator 100 comprises a coil assembly 130, which will be explained in more detail below. The coil assembly 130 is connected to the number of switches 120-10, 120-20, 120-30, 120-40, and configured to be driven by the electric current and to generate, in response to the electric current, the one or more specific magnetic waveforms and/or magnetic intensities to be provided.

Optionally, the magnetic field generator 100 may further comprise a number of switch drivers 120-11, 120-21, 120-31, 120-41, which are connected to the PWM generator 110-10, and which are configured to switch a corresponding switch 120-10, 120-20, 120-30, 120-40 on or off in accordance with the PWM signals PWM LH, PWM LL, PWM RH, PWM RL and/or the control program.

Optionally, the controller 110 may further comprise a signal generator 110-20, which is arranged upstream to and connected to the PWM generator 110-10. It is configured to generate, based on the control program, a source signal, corresponding to the specific magnetic waveforms and/or magnetic intensities to be provided, to be used by the PWM generator 110-20 to generate the number of PWM signals PWM LH, PWM LL, PWM RH, PWM RL.

Fig. 2 shows schematically an exemplary magnetic field generated by the magnetic field generator 100 as described herein. As can be seen, the magnetic field is emitted by the coil 130, which is arranged in a plane as further described below.

Fig. 3 shows a top view of an example of a coil assembly 130 which is to be driven with the previously described magnetic field driver 100. The coil assembly 130 is fixedly mounted on a printed circuit board (PCB) 134. In the example of Fig. 3, the coil assembly 130 includes a conductive coil 130-10 which is spirally wound in a plane which is parallel to the plane defined by the PCB 134. The coil assembly 30 of Fig. 3 is for this reason of the spiral- type. However, other geometries are conceivable. For example, the conductive coil 130-10 can have a shape, such as a circle, an ellipse, a rectangle, a polygon or, as in Fig. 3, a spiral. The radial distance between adjacent coil windings, and thus the number of coil windings given a certain size of printed circuit board is selected depending upon the desired magnetic field density.

As shown in the cross-sectional view of Fig. 4, there are a number of conductive coils 130-10, 130-20, ..., 130-n which are stacked in a layer-by-layer fashion and deposited or mounted on the PCB 134. In other words, one layer includes one coil 130-10 and the next layer includes another coil 130-20, upon which another layer follows with yet another coil 130-30. Each coil 130-10, 130-20, ..., 130-n thus extends in a two-dimensional plane. It goes without saying that the thickness of each coil 130-10, 130-20, ..., 130-n may be argued to extend in a direction perpendicular to this two-dimensional plane. However, the general structure of each coil 130-10, 130-20, ..., 130-n remains planar or flat.

As the plurality of conductive coils 130-10, 130-20, ..., 130-n are stacked in a layer- by-layer fashion and are preferably arranged exactly on top of each other on the PCB 134, they can be said to be arranged co-linearly on the PCB 134. However, any off-set arrangements of the coils 130-10, 130-20, ..., 130-n in which the coils 130-10, 130-20, ..., 130-n have no common axis are also conceivable.

Each coil 130-10, 130-20, ..., 130-n is separated from an adjacent coil 130-10, 130-20, ..., 130-n by an intermediate insulating layer 132. The plurality of coils 130-10, 130-20, ..., 130-n are connected in parallel to the switches 120-10, 120-20, 120-30, 120-40 of the H- bridge 120, as a result of which the same PWM voltage is applied to each coil 130-10, 130- 20, ... , 130-n of the coil assembly 130.

The number of conductive coils 130-10, 130-20, ..., 130-n is in a range of 2 to 15, preferably in a range of 5 to 13, and most preferably amounts to 8. The thickness of each conductive coil is in a range of 0.030 mm to 0.120 mm, preferably in a range of 0.060 mm to 0.090 mm, and most preferably amounts to 0.070 mm. The thickness of each insulating layer is in a range of 0.200 mm to 0.800 mm, preferably in a range of 0.300 mm to 0.600 mm, and most preferably amounts to 0.406 mm. The conductive coils 130-10, 130-20, ..., 130-n are preferably made of copper, or gold-plated copper to reduce the coil resistivity and allow high skin-effect currents, if needed. A preferred material for the insulating layer 132 is a fiberglass- reinforced epoxy.

The coil assembly 130 may preferably have a time constant ts in the range of 5 ps to 15 ps, preferably in a range of 8 ps to 12 ps, further preferably in a range of 10 ps to 11 ps, and most preferably of 10,8 ps.

Optionally, the coil assembly 130 may have an inductivity L in the range of 20 pH to 90 pH, preferably in the range of 40 pH to 80 pH, further preferably of 65 pH. This means a relatively low inductivity of the coil assembly 130. The inductivity of the coil assembly 130 ought to be such that it matches the period of the PWM generator 110-10.

Preferably, the coil assembly 130 may have a self- resonance frequency fr in the range of 4 MHz to 8 MHz, preferably in the range of 6 MHz to 7 MHz, further preferably of about 6,5 MHz, and most preferably of 6,525 MHz.

Optionally, the coil assembly 130 may have a resistivity R in the range of 2 W to 10 W, preferably in the range of 4 W to 8 W, further preferably in range of 5 W to 7 W, and most preferably of 6 W.

In order for the coil assembly 130 to be used in a final product, such as in a medical therapy and/or treatment device, the coil assembly 130 is preferably embedded in a material that has a relative magnetic permeability close to 1, or an absolute permeability close to mq. Such materials have the effect that any magnetic field lines created by the coil assembly will not be disturbed.

As shown in Fig. 5, in another preferred embodiment, a number of magnetic field generators 100 having a number of coil assemblies 130A, 130B, 130C, 130D, 130E may be provided. The coil assemblies 130A, 130B, 130C, 130D, 130E are spaced apart in a longitudinal direction, thus generating a so-called Helmholtz coil configuration. In such a configuration, the conductive coils 130-10, 130-20, ..., 130-n are circular with a radius R that corresponds to the longitudinal spacing between two adjacent coil assemblies 130A, 130B, 130C, 130D, 130E. The longitudinal spacing may, however, vary along the longitudinal axis. Other arrangements are conceivable having a number of coil assemblies 130A, 130B, 130C, 130D, 130E which differs from the number of coil assemblies 130A, 130B, 130C, 130D,

130E shown in Fig. 5, such as two, three or four.

In addition, and as shown in Fig. 6, a two-axes Helmholtz coil concept can be realized in which a pair of coil assemblies 130A, 130B are arranged on a first longitudinal axis, and a second pair of Helmholtz coil assemblies 130C, 130D are arranged on a second longitudinal axis, whereby the first and the second longitudinal axes intersect at a right angle. The conductive coils 130-10, 130-20, ..., 130-n of each coil assembly 130A, 130B of the first pair have a radius R1 which is smaller than the radius R2 of the conductive coils 130-10, 130-20, .. 130-n of each coil assembly 130C, 130D of the second pair.

Generally, each coil assembly 130A, 130B, 130C, 130D, 130E is connected to the switches of an H-bridge, as a result of which each coil assembly 130A, 13 OB, 130C, 130D, 130E can be controlled independently from any other coil assembly 130A, 13 OB, 130C,

130D, 130E. However, it may also be conceivable that each conductive coil 130-10, 130-20,

..., 130-n of a given coil assembly 130A is connected to the switches of an H-bridge, as a result of which each conductive coil 130-10, 130-20, ..., 130-n of a given coil assembly 130A can be controlled independently from any other conductive coil 130-10, 130-20, ..., 130-n of the same coil assembly 130A.

Fig. 7 shows in a schematic block diagram a medical device 200, which is configured to apply the one or more specific magnetic waveforms and/or intensities to a subject S for magnetic field treatment and/or magnetic field therapy.

The medical device 200 comprises at least one magnetic field generator 100 as described above. By way of example, the medical device 200 comprises a number of magnetic field generators 100, each of which forms a dedicated channel. The number of channels may be one, two, three, four, five, six, seven, eight, nine, or more.

In this context, the control program may represent a magnetic field treatment program and/or a magnetic field therapy program to be applied to the subject S.

Optionally, the H-B ridge 120 and the coil assembly 130 may form an integral or one- piece applicator that is configured to be applied on or around the subject S to provide the one or more specific magnetic waveforms and/or intensities to the subject S. Therefore, the coil assembly 130 may also be referred to as or may form an applicator coil and/or a therapy coil, configured to be applied on or around the subject S to provide the one or more specific magnetic waveforms and/or intensities to the subject S.

According to Fig. 8, which shows a schematic block diagram, the controller 110 may further comprise a signal generator 110-20. It may be arranged upstream to and connected to the PWM generator 110-20, and may be configured to generate, based on the control program, a source signal that corresponds to the specific magnetic waveforms and/or magnetic intensities to be provided, to be used by the PWM generator 110-10. Based on the source signal, the PWM generator may generate the number of PWM signals PWM LH, PWM LL, PWM RH, PWM RL.

According to Fig. 8, the signal generator 110-20 may comprise several subunits, such as a waveform generator unit 110-21, a phase generator unit 110-22, a duty cycle variation unit 110-23, an amplitude variation unit 110-24, an offset variation unit 110-25, a frequency compensation unit 110-26, and an adder 110-27. The output of the signal generator 110-20 may be the source signal, which may be the output of the adder 110-27, which source signal may then be provided to the PWM generator 110-20.

The waveform generator unit 110-21 may be used to generate the required waveforms in a normalized form, i.e. by providing a value between -1 to +1, which may be provided as a bitstream. For example, the waveform generator 110-21 may receive one or more input signals, such as a clock signal, a phase information, used to access one or more look-up tables (LUT) containing waveform data, a duty cycle information, and a waveform information. Thereby, the one or more specific waveforms may be generated utilizing the one or more LUT's, comprising predefined data or user defined data, e.g. for providing advanced waveforms. Further, a specific square waveform may be generated utilizing a comparator which compares a current phase value with a duty cycle value.

The phase generator unit 110-22 may be configured to generate a phase information for the waveform generator 110-21 according to a frequency information, received as an input. For example, the phase generator unit 110-22 may receive one or more input signals, such as a clock signal, a reset signal, a variation mode information, such as no variation, linear, exponential, and logarithmic, a frequency information, and a variation step.

Fig. 9 shows a flow chart of a method for operating the above magnetic field generator 100.

In step SI, the PWM generator 110-10 generates a number of PWM signals PWM LH, PWM LL, PWM RH, PWM RL based on the control program comprising information on the one or more specific magnetic waveforms and/or magnetic intensities to be provided.

In step S2, the PWM generator 110-10 controls the H-bridge 120 comprising the number of switches 120-10, 120-20, 120-30, 120-40 connected to the PWM generator 110-10 to receive the number of PWM signals PWM LH, PWM LL, PWM RH, PWM RL, by selectively switching on and off the number of switches 120-10, 120-20, 120-30, 120-40, thereby generating an electric current, caused by the number of PWM signals PWM LH, PWM LL, PWM RH, PWM RL, through the H-bridge 120.

In step S3, the coil assembly 130, which is connected to the number of switches 120- 10, 120-20, 120-30, 120-40 of the H-bridge 120, is driven by the generated electric current, thereby generating, in response to the electric current, the one or more specific magnetic waveforms and/or magnetic intensities.

Optionally, the one or more specific magnetic waveforms and/or intensities may be applied to the subject S for magnetic field treatment and/or magnetic field therapy.

Optionally, the control program may represent a magnetic field treatment program and/or a magnetic field therapy program that is applied to the subject S.

Optionally, the coil assembly 130 may form an applicator coil and/or a therapy coil, to be applied on or around the subject S to provide the one or more specific magnetic waveforms and/or intensities to the subject S.

Optionally, the information on the one or more specific magnetic waveforms and/or magnetic intensities of the control program may comprise a sequence of signal indicators indicating whether one or more signal parameters, used to generate the one or more specific magnetic waveforms and/or magnetic intensities to be provided, remain unchanged or are to be changed.

Optionally, the one or more signal parameters may be selected from: a time slot duration indicating that the signal parameter remain unchanged during the time slot duration, an amplitude of the electric current, an offset of the electric current, a frequency of the electric current, a duty cycle if the waveform of the electric current is square, and a waveform type.

Optionally, the waveform type may be selected, for example, from: sine, triangle, saw-tooth, square, DC, pulse, cirp and sine.

Optionally, the method may further comprise deriving, from the control program, phase information and waveform information, deriving, from the at least one look-up table, LUT, assigning the phase information and the waveform information to a specific waveform, a specific waveform, and generating, using the derived specific waveform, a source signal to be provided to the PWM generator 110-10.

Optionally, the method may further comprise utilizing a comparator, configured to compare a current phase information with a duty cycle value, for generating a specific square waveform for generating a source signal to be provided to the PWM generator 110-10.

A computer program or computer program element may be provided that is characterized by being configured to execute the method steps on an appropriate system.

The computer program element might therefore be stored on the controller, e.g. a data processing unit. This data processing unit may be configured to perform or induce performing of the steps of the method described above. Moreover, it may be configured to operate the components of the above-described device and/or system. The computing unit can be configured to operate automatically and/or to execute the orders of a user. A computer program may be loaded into a working memory of a data processor. The data processor may thus be equipped to carry out the method.

Further, the computer program element might be able to provide all necessary steps to fulfill the procedure of an exemplary embodiment of the method as described above.

According to a further exemplary embodiment of the present invention, a computer readable medium, such as a CD-ROM, USB stick or the like, is presented wherein the computer readable medium has a computer program element stored on it which computer program element is described by the preceding section.

A computer program may be stored and/or distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the internet or other wired or wireless telecommunication systems. However, the computer program may also be presented over a network like the World Wide Web and can be downloaded into the working memory of a data processor from such a network. A medium for making a computer program element available for downloading may also be provided, which computer program element is arranged to perform the above-described method.