WO2007132374A1

WO2007132374A1 - A magnetic sensor device for and a method of sensing magnetic particles

Info

Publication number: WO2007132374A1
Application number: PCT/IB2007/051579
Authority: WO
Inventors: Johannes Aldegonda Theodorus Marie Van Den Homberg; Haris Duric; Jeroen Jacob Arnold Tol
Original assignee: Koninklijke Philips Electronics N. V.
Priority date: 2006-05-09
Filing date: 2007-04-27
Publication date: 2007-11-22

Abstract

A magnetic sensor device (300) for sensing magnetic particles (15), the magnetic sensor device (300) comprising a magnetic field generator unit (12) adapted for generating a magnetic field, a sensing unit (11) adapted for sensing a signal indicative of the presence of the magnetic particles (15) in the generated magnetic field, and a resonator circuit (302, 306) for generating an oscillating signal for driving at least one of the group consisting of the magnetic field generator unit (12) and the sensing unit (11), wherein at least one of the group consisting of the magnetic field generator unit (12) and the sensing unit (11) is integrated within the resonator circuit (302, 306).

Description

A magnetic sensor device for and a method of sensing magnetic particles

FIELD OF THE INVENTION

The invention relates to a magnetic sensor device for sensing magnetic particles.

The invention further relates to a method of sensing magnetic particles. Moreover, the invention relates to a program element.

Further, the invention relates to a computer-readable medium. BACKGROUND OF THE INVENTION

A biosensor may be a device for the detection of an analyte that combines a biological component with a physicochemical or physical detector component. Magnetic biosensors may use the Giant Magnetoresistance Effect (GMR) for detecting biological molecules being magnetic or being labeled with magnetic beads.

In the following, biosensors will be explained which may use the Giant Magnetoresistance Effect.

WO 2005/010542 discloses the detection or determination of the presence of magnetic particles using an integrated or on-chip magnetic sensor element. The device may be used for magnetic detection of binding of biological molecules on a micro-array or biochip. Particularly, WO 2005/010542 discloses a magnetic sensor device for determining the presence of at least one magnetic particle and comprises a magnetic sensor element on a substrate, a magnetic field generator for generating an AC magnetic field, a sensor circuit comprising the magnetic sensor element for sensing a magnetic property of the at least one magnetic particle which magnetic property is related to the AC magnetic field, wherein the magnetic field generator is integrated on the substrate and is arranged to operate at a frequency of 100 Hz or above. WO 2005/010543 discloses a magnetic sensor device comprising a magnetic sensor element on a substrate and at least one magnetic field generator for generating a magnetic field on the substrate, wherein cross-talk suppression means are present for suppressing cross-talk between the magnetic sensor element and the at least one magnetic field generator.

However, conventional sensor devices may have a high power consumption.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to provide a sensor with sufficiently low power consumption and/or low noise performance.

In order to achieve the object defined above, a magnetic sensor device for sensing magnetic particles, a method of sensing magnetic particles, a program element, and a computer-readable medium according to the independent claims are provided. According to an exemplary embodiment of the invention, a magnetic sensor device for sensing magnetic particles is provided, the magnetic sensor device comprising a magnetic field generator unit adapted for generating a magnetic field, a sensing unit adapted for sensing a signal indicative of the presence of the magnetic particles in the generated magnetic field, and a resonator circuit for generating an oscillating signal for driving at least one of the group consisting of the magnetic field generator unit and the sensing unit, wherein at least one of the group consisting of the magnetic field generator unit and the sensing unit is integrated within the resonator circuit.

According to another exemplary embodiment of the invention, a method of sensing magnetic particles is provided, the method comprising generating a magnetic field by a magnetic field generator unit, sensing, by a sensing unit, a signal indicative of the presence of the magnetic particles in the generated magnetic field, and generating, by a resonator circuit, an oscillating signal for driving at least one of the group consisting of the magnetic field generator unit and the sensing unit, wherein at least one of the group consisting of the magnetic field generator unit and the sensing unit is integrated within the resonator circuit. According to still another exemplary embodiment of the invention, a program element is provided, which, when being executed by a processor, is adapted to control or carry out a method of sensing magnetic particles having the above mentioned features.

According to yet another exemplary embodiment of the invention, a computer-readable medium is provided, in which a computer program is stored which, when being executed by a processor, is adapted to control or carry out a method of sensing magnetic particles having the above mentioned features.

The electronic sensing scheme according to embodiments of the invention can be realized by a computer program, that is by software, or by using one or more special electronic optimization circuits, that is in hardware, or in hybrid form, that is by means of software components and hardware components.

According to an exemplary embodiment of the invention, a magnetic sensor device may be provided in which a resonator circuit generates an oscillating signal for driving a magnetic field generator unit which magnetic field generator unit is embedded or circuited within the resonator circuit. Additionally or alternatively, a resonator circuit for generating an oscillating signal for driving a sensing unit of such a magnetic sensor device may be provided, wherein the sensing unit may be embedded or circuited within the resonator circuit. In other words, any of the functional components of such a magnetic sensor device which shall be supplied with a modulating drive signal may be connected within a resonator circuit which may allow a low energy operation mode. Such a resonator circuit (for instance including a capacitor and an inductance) may be supplied with electric energy and starts oscillating (for instance in a resonant or harmonic manner). Therefore, a time-dependent electric signal is present within such a resonator circuit which may be used for driving the magnetic field generator and/or the sensing unit. For a magnetic sensor device as disclosed, for instance, in WO 2005/010542 or WO2005/010543 a magnetic field generator and a sensing unit need to be supplied with a time varying (for instance oscillating) signal. By using the repeated or continuous oscillation of a resonator circuit with a small (or in an extreme case vanishing) loss of electric energy, the magnetic sensor device may be operated in a low power mode. Thus, particularly when such a magnetic sensor device is provided as a portable or wireless device without connection to a mains supply and is powered for instance by a battery or the like, the lifetime of the battery may be increased and the use of the magnetic sensor device may be more convenient for a user.

In a resonator circuit, the losses of electric power may be very small, for instance may be restricted to ohmic losses. Thus, as compared to a solution in which a separate driver unit drives a magnetic field generator or a sensing unit, embodiments of the invention may use the present energy more efficiently. The supply current may oscillate between a capacitance and an inductance of a resonator circuit thereby passing and modulating the magnetic field generator or sensing unit, and losses occur essentially only due to the resistance of such a circuitry. Such a magnetic sensor device may be based on the principle that the magnetic field generator generates a magnetic field with a time dependence. The sensing unit may then, using an effect like for instance the GMR effect, sense the presence of magnetic particles (like biological molecules having magnetic beads attached thereto) due to the varying signal of the exciting magnetic field. However, when simply incorporating the magnetic field generator unit and/or the sensing unit into the respective resonator circuit, the energy consumption can be significantly reduced.

Taking such measures may also have a noise filtering effect and may improve noise filtering and amplitude stabilizing properties of the resonant tank. A resonant tank may dampen out band circuit noise and improve resistance to amplitude fluctuations. The term "resonator circuit" may particularly denote a circuit comprising a capacity and an inductance so that the circuit is capable of oscillating. Such a harmonic oscillation may be performed particularly at a frequency which is not too far away from a resonance frequency defined by the value of the impedance and the inductance of the resonator circuit. However, it is not absolutely necessary to operate the resonator circuit exactly at the resonance frequency. The use of a resonator circuit for generating a modulating signal for driving the magnetic field generator or the sensing unit may allow to "recycle" the energy.

Thus, exemplary embodiments of the invention may allow for a reduction or minimization of the power for the magnetic bead excitation of a sensor, particularly of a biosensor. Such a system may be embedded in a magnetic biosensor device targeting an intermediate space between the low performance low cost devices (for instance glucose sensors, dip-stick pregnancy tests, etc.) at the one side, and high performance high cost laboratory equipment (for instance optical biochips) at the other side.

Such a magnetic sensor device may be in an ensemble of battery operated handheld devices, delivering high analytical performance by detecting low concentrations of multiple molecules, in short time.

The mobile battery operated usage of the device limits the total available energy budget. It is in general required to reduce or minimize the power consumption of the device in order to increase or maximize battery lifetime. The integration of the sensing unit and/or the magnetic field generator unit in a respective resonator circuit may contribute significantly to an energy reduction.

Next, further exemplary embodiments of the invention will be explained. In the following, further exemplary embodiments of the magnetic sensor device for sensing magnetic particles will be explained. However, these embodiments also apply to the method of sensing magnetic particles, to the program element and to the computer-readable medium.

The resonator circuit may comprise a capacitance (C) and an inductance (L) coupled with the magnetic field generator unit and/or the sensing unit in serial or in parallel. Therefore, some closed loop circuit may be generated including the capacitance, the inductance and the magnetic field generator unit or the sensing unit. The decision whether the design should connect these elements in serial or in parallel may depend on the actual resistance value needed for a specific operation mode of the magnetic sensor.

The resonator circuit may comprise a resonator tank. A "tank circuit" may particularly denote a parallel resonator circuit containing only a coil and a capacitor. Both the coil and the capacitor may store electrical energy for a part of each cycle. A resonator tank may be a resonator part of an oscillator. It may include (only) passive parts of such an oscillator. An oscillator, apart from a resonator circuit, may further comprise active components like a switch transistor or the like.

The magnetic sensor device may comprise an oscillator circuit in which the resonator circuit is incorporated. Such an oscillator circuit may be connected between an upper voltage level and a lower voltage level provided by a battery or the like and may generate an oscillation frequency for driving the field generating wire or the GMR. According to one embodiment, the resonator circuit may be incorporated in such an oscillator circuit.

Particularly, the oscillator circuit may be one of the group consisting of a Pierce oscillator, a Colpitt oscillator, and a negative resistance oscillator. A Pierce oscillator may be an integrated circuit or a transistor based crystal oscillator circuit which can be a stand alone or part of an even larger, more complex circuit. The term "Pierce oscillator" may denote a variation of a Colpitt oscillator and may use a quartz crystal in place of an inductor which may be found in a Colpitt's oscillator feedback network. The crystal may maintain a highly stable output frequency. A "Colpitt oscillator" may denote an oscillator with a pair of tapped capacitors in a feedback network.

As an alternative to the configuration with the oscillator circuit, the magnetic sensor device may comprise a radio frequency power stage in which the resonator circuit may be incorporated. Such a radio frequency power stage may be a class-E power stage. A class-E power stage is disclosed, as such, in US 4,607,323, for example. In such an class-E power stage, the magnetic field generating device may be circuited in series with an inductance and in parallel with a capacitance, and may be connected between a supply voltage and a ground voltage. However, between ground voltage and the magnetic field generator including circuitry, a (transistor) switch may be provided which may connect the circuitry to ground or not. The magnetic sensor device may further comprise a frequency locking unit adapted for locking a frequency of the oscillating signal. The oscillation frequency of the resonator circuit for the magnetic field generating unit and/or for the sensing unit may be locked for synchronous detection of the magnetic signal. For example, this may be realized using a phase-locked loop (PLL). The magnetic sensor device may comprise a further magnetic field generator unit adapted for generating a magnetic field. The magnetic sensor device may further comprise a further sensing unit adapted for sensing a signal indicative of the presence of the magnetic particles in the generated magnetic field. At least one of the group consisting of the further magnetic field generator unit and the further sensing unit may be integrated within the resonator unit. Therefore, it is possible to connect a plurality of magnetic field generating units and/or a plurality of sensing units in parallel to one another, particularly to reduce the total resistance, while simultaneously increasing an effective sensor area.

The magnetic sensor device may comprise an evaluation unit adapted for electronically evaluating the signal sensed by the sensing unit. Such an evaluation unit may comprise components like an amplifier for amplifying the signal sensed by the sensing unit, analog to digital converter units, filter units, etc.

The magnetic sensor device may further comprise an actuation wire adapted for attracting the magnetic particles towards the sensing unit. The magnetic sensor device may further comprise a further resonator circuit for generating an oscillating signal for driving the actuation wire. The actuation wire may also be integrated within the further resonator circuit. In other words, the same principle as has been described for the magnetic field generator unit and/or for the sensing unit can also be applied for the large currents in the actuation wires that are used to attract the beads towards the binding surface. By taking this measure, the energy consumption of the entire circuit may be further reduced. The magnetic sensor device may be a battery-powered device. Particularly, the magnetic sensor device may be a device which is powered without a wired connection to a main supply. Also a solar cell realization with a solar cell which recharges a battery or an accumulator is possible. However, in all these kinds of devices, the reduction of the energy consumption is an important task for improving the performance and the user- friendliness of the magnetic sensor device.

The magnetic sensor device may be adapted as a portable device. Again, in a portable device, energy consumption is a very important point since the portability makes it difficult or impossible to recharge the magnetic sensor device using a main supply.

The sensing unit may be adapted for sensing the magnetic particles based on the Giant Magnetoresistance Effect (GMR). Magnetic biosensors may use the Giant

Magnetoresistance Effect (GMR) being a quantum mechanical effect observed in thin film structures composed of alternating ferromagnetic and nonmagnetic metal layers. The effect manifests itself as a significant decrease in resistance from the zero-field state, when the magnetization of adjacent (ferro)magnetic layers are antiparallel due to a weak anti- ferromagnetic coupling between layers, to a lower level of resistance when the magnetization of the adjacent layers align due to an applied external field. General aspects of how to realize such a GMR sensor may be taken from WO 2005/010542 A2 and WO 2005/010543 Al, which are herein incorporated by reference in their entirety, in particular with respect to all aspects related to GMR magnetic sensors, particularly biosensors. Moreover, the sensing unit can comprise any suitable sensor based on the detection of the magnetic properties of particles to be measured on or near to the sensor surface. Therefore, the sensing unit is designable as a coil, magneto -resistive sensor, magneto -restrictive sensor, Hall sensor, planar Hall sensor, flux gate sensor, SQUID (Semiconductor Superconducting Quantum Interference Device), magnetic resonance sensor, or as another sensor actuated by a magnetic field. The sensing unit may be adapted for quantitatively sensing the magnetic particles. Therefore, the evaluation unit may evaluate amplitudes of the signals in such a manner that as a final result, a concentration or amount of magnetic particles or of magnetically labeled particles to be detected may be estimated. This may be a more meaningful result as compared to a purely qualitative result whether a particular species or fraction of (biological) molecules is present or absent.

The magnetic sensor device may be adapted for sensing magnetic beads attached to biological molecules. Therefore, for instance using linker molecules, paramagnetic or ferromagnetic beads may be attached directly to biological molecules (like nucleic acids, DNA strands, proteins, polypeptides, hormones, etc.) so as to allow or promote a magnetic detection. However, it is possible that magnetic properties of the biological molecules themselves are used as a basis for the detection, without magnetic labels.

Particularly, the magnetic sensor device may be adapted as a magnetic biosensor device, that is to say for detecting the presence or absence or concentration of biological molecules. At least a part of the magnetic sensor device may be realized as a monolithically integrated circuit. Thus, at least a part of the components of the magnetic sensor device may be monolithically integrated within a substrate, particularly a semiconductor substrate, more particularly a silicon substrate. However, embodiments of the invention may be also applied in a context of group III -V semiconductors, like gallium arsenide. Such a monolithically integration may significantly reduce the dimensions of the biosensor and therefore the required volumes of a sample to be analyzed. Furthermore, the signal processing paths are short and small in an integrated solution, so that the length of a conduction path along which the signals may be negatively influenced by disturbing effects may be reduced. Therefore, such a monolithically integrated biosensor may be particularly advantageous. The aspects defined above and further aspects of the invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to these examples of embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.

Fig. 1 illustrates a magnetic sensor device according to an exemplary embodiment of the invention. Fig. 2 illustrates the magnetic sensor device of Fig. 1 in another operation state.

Fig. 3 illustrates a magnetic sensor device according to an exemplary embodiment of the invention.

Fig. 4 illustrates a magnetic sensor device. Fig. 5 illustrates a magnetic sensor device according to an exemplary embodiment of the invention.

Fig. 6 illustrates different configurations of a sensing unit within a resonator circuit.

Fig. 7 illustrates a magnetic sensor device having a Pierce oscillator according to an exemplary embodiment of the invention.

Fig. 8 illustrates a magnetic field generator unit according to an exemplary embodiment of the invention having implemented an class-E driver.

Fig. 9 illustrates a magnetic sensor device according to an exemplary embodiment of the invention having a plurality of field generating wires. Fig. 10 illustrates a magnetic sensor device according to an exemplary embodiment of the invention having a frequency locking function for synchronous detection.

DESCRIPTION OF EMBODIMENTS

The illustration in the drawing is schematically. In different drawings, similar or identical elements are provided with the same reference signs.

In a first embodiment the device according to the present invention is a biosensor and will be described with respect to Fig. 1 and Fig. 2. The biosensor detects magnetic particles in a sample such as a fluid, a liquid, a gas, a visco-elastic medium, a gel or a tissue sample. The magnetic particles can have small dimensions. With nano-particles are meant particles having at least one dimension ranging between 0.1 nm and 1000 nm, preferably between 3 nm and 500 nm, more preferred between 10 nm and 300 nm. The magnetic particles can acquire a magnetic moment due to an applied magnetic field (e.g. they can be paramagnetic). The magnetic particles can be a composite, e.g. consist of one or more small magnetic particles inside or attached to a non-magnetic material. As long as the particles generate a non-zero response to a modulated magnetic field, i.e. when they generate a magnetic susceptibility or permeability, they can be used. The device may comprise a substrate 10 and a circuit e. g. an integrated circuit.

A measurement surface of the device is represented by the dotted line in Fig. 1 and Fig. 2. In embodiments of the present invention, the term "substrate" may include any underlying material or materials that may be used, or upon which a device, a circuit or an epitaxial layer may be formed. In other alternative embodiments, this "substrate" may include a semiconductor substrate such as e.g. a doped silicon, a gallium arsenide (GaAs), a gallium arsenide phosphide (GaAsP), an indium phosphide (InP), a germanium (Ge), or a silicon germanium (SiGe) substrate. The "substrate" may include for example, an insulating layer such as a Siθ₂ or an S1₃N₄ layer in addition to a semiconductor substrate portion. Thus, the term substrate also includes glass, plastic, ceramic, silicon-on-glass, silicon-on sapphire substrates. The term "substrate" is thus used to define generally the elements for layers that underlie a layer or portions of interest. Also, the "substrate" may be any other base on which a layer is formed, for example a glass or metal layer. In the following reference will be made to silicon processing as silicon semiconductors are commonly used, but the skilled person will appreciate that the present invention may be implemented based on other semiconductor material device(s) and that the skilled person can select suitable materials as equivalents of the dielectric and conductive materials described below.

The circuit may comprise a magneto -resistive sensor 11 as a sensor element and a magnetic field generator in the form of a conductor 12. The magneto -resistive sensor 11 may, for example, be a GMR or a TMR type sensor. The magneto -resistive sensor 11 may for example have an elongated, e.g. a long and narrow stripe geometry but is not limited to this geometry. Sensor 11 and conductor 12 may be positioned adjacent to each other within a close distance g. The distance g between sensor 11 and conductor 12 may for example be between 1 nm and 1 mm; e.g. 3 μm. The minimum distance is determined by the IC process. In Fig. 1 and Fig. 2, a co-ordinate device is introduced to indicate that if the sensor device is positioned in the xy plane, the sensor 11 mainly detects the x-component of a magnetic field, i. e. the x-direction is the sensitive direction of the sensor 11. The arrow 13 in Fig. 1 and Fig. 2 indicates the sensitive x-direction of the magneto -resistive sensor 11 according to the present invention. Because the sensor 11 is hardly sensitive in a direction perpendicular to the plane of the sensor device, in the drawing the vertical direction or z- direction, a magnetic field 14, caused by a current flowing through the conductor 12, is not detected by the sensor 11 in absence of magnetic nano-particles 15. By applying a current to the conductor 12 in the absence of magnetic nano-particles 15, the sensor 11 signal may be calibrated. This calibration is preferably performed prior to any measurement. When a magnetic material (this can e.g. be a magnetic ion, molecule, nano- particle 15, a solid material or a fluid with magnetic components) is in the neighborhood of the conductor 12, it develops a magnetic moment m indicated by the field lines 16 in Fig. 2.

The magnetic moment m then generates dipolar stray fields, which have in- plane magnetic field components 17 at the location of the sensor 11. Thus, the nano-particle 15 deflects the magnetic field 14 into the sensitive x-direction of the sensor 11 indicated by arrow 13 (Fig. 2). The x-component of the magnetic field Hx which is in the sensitive x- direction of the 12 sensor 11, is sensed by the sensor 11 and depends on the number of magnetic nano-particles 15 and the conductor current Ic.

For further details of the general structure of such sensors, reference is made to WO 2005/010542 and WO 2005/010543. Reference numeral 20 denotes a control unit for controlling the signal distribution and power supply within the magnetic sensor device of Fig. 1 and Fig. 2. As can further be taken from Fig. 1 and Fig. 2, such a control unit 20 is coupled to a battery 30 for supplying the components of the magnetic sensor device of Fig. 1 and Fig. 2 with electrical energy. Since the magnetic sensor device of Fig. 1 and Fig. 2 may be used as a portable device being battery powered, it is an important task of the control unit 20 to reduce the amount of electric energy needed or consumed by the magnetic sensor device.

In the following, referring to Fig. 3, a magnetic sensor device 300 for sensing magnetic particles 15 attached to biological molecules 301 (for instance DNA strands) according to an exemplary embodiment will be explained. The magnetic sensor device 300 comprises a magnetic field generator unit 12 which may also be denoted as a magnetic field generating wire or a conductor which is adapted for generating a magnetic field. Furthermore, a sensing unit 11 (for instance a GMR sensor) is provided and is adapted for sensing a signal indicative of the presence of the magnetic particles 15 in the generated magnetic field. Furthermore, a first resonator circuit 302 is shown which is adapted for generating an oscillating signal for driving the magnetic field generator unit 12. This first resonator circuit 302 comprises a first inductance 303 and a first capacitance 304. When the first resonator circuit 302 is operated between an upper supply potential Vaa and a lower supply potential V_ss, and when a switch 305 is operated accordingly, the oscillator circuits 302 oscillates and therefore supplies the magnetic field generator unit 12 with an oscillating or time varying or modulating signal. Consequently, the magnetic field generating unit 12 generates a modulated magnetic field which influences a sensing region in an environment of the sensing unit 11.

Furthermore, a second resonator circuit 306 is provided for generating an oscillating signal for driving the sensing unit 11. In contrast to the first resonator circuit 302, the second resonator circuit 306 comprises a second inductance 307 and a second capacitance 308 which are connected in parallel, and not in serial as in the case of the first resonator circuit 302. However, it is also possible that the first inductance 303 and the first capacitance 304 are connected in parallel and/or that the second capacitance 308 and the second inductance 307 are connected in serial. Again, the second resonator circuit 307 is connected between the upper potential Vaa and the lower potential V_ss which may be provided by a battery 30 of the system (not shown in Fig. 3). A switch 309 may be provided so as to generate a time- dependent signal for activating the second resonator circuit 306. A further switch 310 is provided for coupling a signal of the sensing unit 11 to an evaluation unit 311 for evaluating the signal, and for estimating a concentration of the magnetic particles 15.

It is a characteristic for the magnetic sensor device 300 that the magnetic field generator unit 12 is connected within the first resonator unit 302, and that the sensing unit 11 is connected within the second resonator unit 306. In this context, the term "connected " or "integrated" may denote that the oscillating function of the resonator circuit directly influences the corresponding components 12 or 11 due to the fact that these components 12 or 11 are directly located within the oscillation path of the resonator circuit 302 and 306, respectively.

The evaluation unit 311 which is adapted for electronically evaluating the signal sensed by the sensing unit 11 may comprise components like an amplifier unit for amplifying the signal sensed by the sensing unit 11, etc.

In the following, referring to Fig. 4, a conventional magnetic sensor device 400 will be explained.

The magnetic sensor device 400 comprises an oscillator circuit 401 which includes a capacitance 402 and an inductance 403. An output signal of the oscillator circuit 401 serves as a control signal for a driver unit 404. The driver unit 404 outputs a signal driving the magnetic field generator unit 12 which may also be denoted as a field generating wire. Beyond this, a GMR current modulation unit 405 generates a signal for driving a GMR sensor 11 for detecting magnetic particles 15. A signal may be tapped off and supplied to a filter unit 406 which is connected to an amplifier unit 407 for deriving an amount of the particles 15 to be detected. The biosensor 400 uses large alternating currents for excitation of the magnetic particles 15 (with typical magnitudes between 50 and 100 mA_p__p). The greatest part (for instance more than two third) of the aforementioned current may be dissipated in the oscillator 401 and the driver circuit 404 of the field generating wire 12. Furthermore, the excitation current is continuously drawn from the batteries 30.

However, in an improved situation which can be obtained by embodiments of the invention as shown in Figs. 3, 5 to 10, magnetic beads 15 are excited essentially without any power loss in the driver circuit.

In the following, it will be explained on the basis of the magnetic sensor device 500 shown in Fig. 5 how a significant power reduction may be achieved.

This can be obtained by including the low resistance field generating wire 12 into the LC resonator tank 502 being part of an oscillator circuit 501. Once excited, the current will flow back and forth within the resonator tank 502, through the field generating wire 12. Fig. 5 further shows a GMR current modulation unit 503, a filter unit 504 and an amplifier unit 505 of an evaluation portion.

The quality factor of the resonator tank 502 may be made as high as possible, such that the power consumed from the batteries 30 is approximately equal to the power that is dissipated in the field generating wire 12 only. The resonator tank 502 is a part of the oscillator circuit 501. Alternatively, the resonator tank 502 may be incorporated in a common "class-E" RF power stage that is driven by an external frequency reference.

The noise normally present in the excitation current is filtered out by the resonator tank 502. Furthermore, a high quality factor Q will damp an amplitude fluctuation that can be caused by disturbances on the supply voltage Vaa- This may be important as amplitude variations in the excitation current appear directly on the demodulated signal at the output.

The same principle as has been explained referring to Fig. 5 for the magnetic field generating unit 12 can be used, additionally or alternatively, in the GMR branch. This is shown in Fig. 6. Fig. 6 shows a first configuration 600 in which the sensing unit 11 is connected in parallel with an inductance L 307 and is connected in parallel with a capacitance C 308. In a second configuration 610, the sensing unit 11 is connected in parallel to the capacitance 308 and in parallel to the inductance 307. The GMR 11 can thus be included in series with the capacitor 308 or coil

307 in an LC current, or in parallel to the LC branch, depending on the actual resistance value of the GMR 11.

In the case that the voltage swing across the GMR 11 is much larger than the voltage swing across the field generating wire 12, the power savings may be less than for the field generating wire 12. In a situation where the GMR 11 is driven by a traditional class AB amplifier, the efficiency is theoretically around 70% for a rail-to-rail sine wave. When the GMR is included in a resonant tank, a theoretical efficiency of 100% can be obtained, because zero voltage switching can be realized into the oscillator circuit.

However, important advantages which may be obtained by embodiments of the invention are in the noise filtering and amplitude stabilizing properties of the resonant tank. Any noise present in the conventional GMR current modulation circuit would be directly coupled to the input of the LNA (Low Noise Amplifier). A resonant tank will dampen out the band circuit noise and provide some resistance to amplitude fluctuations.

In the following, referring to Fig. 7, a magnetic sensor device 700 according to an exemplary embodiment will be explained.

The magnetic sensor device 700 comprises an amplifier unit 701, wherein the capacities 304 and the amplifier unit 701 may be part of a pre-processing IC 102.

In the described embodiment including a Pierce oscillator configuration, the field generating wire 12 is included in a Pierce oscillator as shown in Fig. 7 (for example, see US 5,821,828, this oscillator realizes zero voltage switching for rail-to-rail sine waves). In order to obtain a high Q, low values for the capacitance 304 and resistance, and high value for the impedance 303 may be advantageous.

Q = IIRs^LIC

The capacitances 304 can be easily integrated on the pre-processing IC 702, whereas the inductance 303 may be included in the cartridge. In the following, referring to Fig. 8, a magnetic sensor device 800 according to an exemplary embodiment including an class-E driver will be explained.

The embodiment of Fig. 8 shows a possible realization of a conventional class-E power stage. The field generating wire 12 may also be in series with the capacitor 304.

A switching transistor 801 is provided which is driven by a sine wave in signal 802. However, a capacitor 803 is connected between the sine wave in terminal 802 and the gate of the transistor 801. An ohmic resistor 804 is furthermore provided. The source/drain terminals of the transistor 801 are connected between the resonator circuit 805 on the one hand and a lower potential V_ss on the other hand.

In the following, referring to Fig. 9, a magnetic sensor device 900 according to an exemplary embodiment will be explained which implements parallel field generating wires 12.

In the embodiment of Fig. 9, several field generating wires 12 are connected in parallel to reduce the total wire resistance, while increasing the effective sensor area. Furthermore, a plurality of corresponding sensing units 11 are shown in Fig. 9.

In the following, referring to Fig. 10, an embodiment 1000 will be explained which includes frequency locking for synchronous detection.

The oscillation frequency of the wire and GMR oscillator may need to be locked for synchronous detection of the magnetic bead signals. This can be implemented by phase locked loops (PLLs) locked to the same reference oscillator as shown in Fig. 10.

The wire oscillator 1001 and the GMR oscillator 1002 are made controllable, for instance voltage controlled oscillators, and used as oscillator inside each PLL. The divider ratio N_wire and N_GMR determine the oscillation frequency of wire oscillator 1001 and GMR oscillator 1002, respectively. Furthermore, a phase detector 1003 and a loop filter 1004 are shown.

A third PLL or even simpler, the reference frequency itself, can be used for synchronous detection. For example, if N_wire = 10 and N_GMR =9, that is, the wire and GMR frequency are closely spaced, Nd_emoduiation⁼l, i.e. the reference frequency itself can be used for synchronous detection. If the bandwidth of each PLL is chosen sufficiently large, phase noise of each harmonic oscillator may be reduced to the phase noise level of the applied reference, for instance a crystal oscillator, which translates into an improved dynamic range of the biosensor. Furthermore, the resonator tank may be realized on the sensor chip, MID

(moulded interconnect device), flex connections, discrete passives, integrated on the preprocessing IC or any combination of the aforementioned.

It should be noted that the term "comprising" does not exclude other elements or features and the "a" or "an" does not exclude a plurality. Also elements described in association with different embodiments may be combined.

It should also be noted that reference signs in the claims shall not be construed as limiting the scope of the claims.

Claims

CLAIMS:

1. A magnetic sensor device (300) for sensing magnetic particles (15), the magnetic sensor device (300) comprising a magnetic field generator unit (12) adapted for generating a magnetic field; a sensing unit (11) adapted for sensing a signal indicative of the presence of the magnetic particles (15) in the generated magnetic field; a resonator circuit (302, 306) for generating an oscillating signal for driving at least one of the group consisting of the magnetic field generator unit (12) and the sensing unit

(H); wherein at least one of the group consisting of the magnetic field generator unit (12) and the sensing unit (11) is integrated within the resonator circuit (302, 306).

2. The magnetic sensor device (300) of claim 1, wherein the resonator circuit (302, 306) comprises a capacitance (304, 308) and an inductance coupled with the at least one of the group consisting of the magnetic field generator unit (12) and the sensing unit (11) in serial or in parallel.

3. The magnetic sensor device (300) of claim 1, wherein the resonator circuit (302) comprises a resonator tank (502) in which the at least one of the group consisting of the magnetic field generator unit (12) and the sensing unit (11) is integrated.

4. The magnetic sensor device (300) of claim 3, wherein the resonator tank (502) is provided at one of the positions of the group consisting of a chip in which at least a part of the magnetic sensor device is monolithically integrated, a moulded interconnect device, a flex connection, a discrete passive, and a pre-processing integrated circuit.

5. The magnetic sensor device (500) of claim 1, comprising an oscillator circuit (501) in which the resonator circuit (502) is incorporated.

6. The magnetic sensor device (500) of claim 5, wherein the oscillator circuit is one of the group consisting of a Pierce oscillator, a Colpitt oscillator, and a negative resistance oscillator.

7. The magnetic sensor device (700) of claim 1, comprising a radio frequency power stage in which the resonator circuit is incorporated.

8. The magnetic sensor device (700) of claim 7, wherein the radio frequency power stage is a class-E power stage.

9. The magnetic sensor device (1000) of claim 1, comprising a frequency locking unit adapted for locking a frequency of the oscillating signal.

10. The magnetic sensor device (1000) of claim 9, wherein the frequency locking unit comprises a phase-locked loop.

11. The magnetic sensor device (900) of claim 1 , comprising a further magnetic field generator unit (12) adapted for generating a magnetic field; comprising a further sensing unit (11) adapted for sensing a signal indicative of the presence of the magnetic particles (15) in the generated magnetic field; wherein at least one of the group consisting of the further magnetic field generator unit (12) and the further sensing unit (11) is integrated within the resonator circuit.

12. The magnetic sensor device (300) of claim 1, comprising an evaluation unit (311) adapted for electronically evaluating the signal sensed by the sensing unit (11).

13. The magnetic sensor device (500) of claim 12, wherein the evaluation unit (311) comprises an amplifier unit (505) for amplifying the signal sensed by the sensing unit (11).

14. The magnetic sensor device (300) of claim 1, comprising an actuation wire adapted for guiding the magnetic particles (15) towards the sensing unit (11); comprising a further resonator circuit for generating an oscillating signal for driving the actuation wire; wherein the actuation wire is integrated within the further resonator circuit.

15. The magnetic sensor device (300) of claim 1, adapted as a battery-powered device.

16. The magnetic sensor device (300) of claim 1, adapted as a portable device.

17. The magnetic sensor device (300) of claim 1, wherein the sensing unit (11) is adapted for sensing the magnetic particles (15) based on the Giant Magnetoresistance Effect.

18. The magnetic sensor device (300) of claim 1, wherein the sensing unit (11) is adapted for quantitatively sensing the magnetic particles (15).

19. The magnetic sensor device (300) of claim 1, adapted for sensing magnetic beads (15) attached to biological molecules.

20. The magnetic sensor device (300) of claim 1, adapted as a magnetic biosensor device.

21. The magnetic sensor device (300) of claim 1, wherein at least a part of the magnetic sensor device (300) is realized as a monolithically integrated circuit.

22. A method of sensing magnetic particles (15), the method comprising generating a magnetic field by a magnetic field generator unit (12); sensing, by a sensing unit (11), a signal indicative of the presence of the magnetic particles (15) in the generated magnetic field; generating, by a resonator circuit (302, 306), an oscillating signal for driving at least one of the group consisting of the magnetic field generator unit (12) and the sensing unit (11); wherein at least one of the group consisting of the magnetic field generator unit (12) and the sensing unit (11) is integrated within the resonator circuit (302, 306).

23. A program element, which, when being executed by a processor (20), is adapted to control or carry out a method of sensing magnetic particles (15), the method comprising: generating a magnetic field by a magnetic field generator unit (12); sensing, by a sensing unit (11), a signal indicative of the presence of the magnetic particles (15) in the generated magnetic field; generating, by a resonator circuit (302, 306), an oscillating signal for driving at least one of the group consisting of the magnetic field generator unit (12) and the sensing unit (11); wherein at least one of the group consisting of the magnetic field generator unit (12) and the sensing unit (11) is integrated within the resonator circuit (302, 306).

24. A computer-readable medium, in which a computer program is stored which, when being executed by a processor (20), is adapted to control or carry out a method of sensing magnetic particles (15), the method comprising: generating a magnetic field by a magnetic field generator unit (12); sensing, by a sensing unit (11), a signal indicative of the presence of the magnetic particles (15) in the generated magnetic field; generating, by a resonator circuit (302, 306), an oscillating signal for driving at least one of the group consisting of the magnetic field generator unit (12) and the sensing unit (11); wherein at least one of the group consisting of the magnetic field generator unit (12) and the sensing unit (11) is integrated within the resonator circuit (302, 306).