NEW METHOD FOR EXTRACTING SIGNALS GENERATED BY MAGNETORESISTIVE SENSORS

A new ac detection technique which reduces the influence of offset, te mperature drift and remanence of magnetoresistive sensors is proposed. The technique relies on nonlinearity of the magnetoresistance, permit ting mixing of excitation fields of close frequencies and detection of the sensor output signal at the difference frequency. The difference frequency component appears in the output signal spectrum only when an external de field is applied along the excitation direction. This fre quency is located further apart from the excitation frequencies, and t his relatively large gap between the frequencies reduces undesirable c oupling between the output and excitation circuits and alleviates the filtering problem. Another advantage of the method is due to its poten tially better sensitivity (up to nearly two orders), since it enables measuring fields aligned along the sensor easy axis, for which the dem agnetizing field is smaller.