SENSOR DEVICE WITH ALTERNATING EXCITATION FIELDS

摘要

The invention relates to a magnetic sensor device comprising excitation wires (11, 13) for generating a magnetic excitation field and a magnetic sensor element, particularly a GMR sensor (12), for sensing magnetic fields generated by labeling particles in reaction to the excitation field. The magnetic excitation fields are generated with non-sinusoidal forms, particularly as square-waves, such that their spectral range comprises a plurality of frequency components. Magnetic particles with different magnetic response characteristics can then be differentiated according to their reactions to the different frequency components of the excitation fields. The magnetic excitation field and the sensing current driving the GMR sensor (12) are preferably generated with the help of ring modulators (22, 24). Moreover, ring modulators (27, 29) may be used for the demodulation of the sensor signal.