MAGNETIC SENSOR DEVICE WITH DIFFERENT INTERNAL OPERATING FREQUENCIES

摘要

The invention relates to a magnetic sensor device (10) comprising wires (11, 13) for the generation of a magnetic field with a first frequency f₁ a GMR sensor (12) operated with an input current of a second frequency f₂, and a demodulator (26) operated at a third frequency f₃. In order to avoid signal corruption by phase noise and to improve the signal-to-noise ratio, the first, second and third frequencies are derived by a supply unit (121) from a common reference frequency f_ref. Said derivation may for example be achieved with the help of digital frequency dividers. Furthermore, phase detectors (PD1, PD2) may be used in a feedback control loop to assure predetermined relations between the phases of the three frequencies. In another embodiment of the invention, the phase and/or amplitude of a model signal, which is used to process a desired signal component in the output of the sensor, is tracked by an adaptation algorithm, for example a gradient descent.