Magnetoresistive sensor with reduced output signal jitter

Abstract

A magnetoresistive sensor for use in detecting relative motion between the sensor and a further object bearing an alternating pattern of north/south magnetic poles. The sensor includes one or more pairs of magnetoresistive elements positioned so that each element within a pair magnetically complements the corresponding element in that pair. That is, whenever an element is exposed to a north pole of the magnetic pattern, a corresponding complementary element is exposed to a south pole so as to provide a magnetically complemented output. Such pair of complementary magnetoresistive elements are connected into a bridge circuit such that jitter effects caused by asymmetric magnetic fields and physical differences between sensor elements are cancelled. The quadrature sensor output is frequency multiplied to provide frequency multiplied output signals in quadrature. The sensing arrangement can be used, for example, in the context of a rotary encoder having a drum having a circumference covered with a magnetic track at a predetermined pitch, and may include a plurality of magnetoresistive elements positioned opposite the drum and connected in a bridge circuit such that when the drum rotates an output signal from the encoder indicates rotary motion of the drum.