Wirelessly interrogable magnetic field sensor utilizing giant magneto-impedance effect and surface acoustic wave devices

A micro-magnetic field sensor is developed using the giant magneto-impedanc e (GMI) effect in a 30 mu m diameter amorphous FeCoSiBNd wire of zero magne tostriction. Surface Acoustic Wave (SAW) devices are described as passive, radio requestable sensor devices. A new type employs the electrical load of the SAW device by the impedance of conventional sensors, In order to devel op a wirelessly interrogable magnetic field sensor, the combination of GMI sensors and SAW transponders is discussed by several measurements, The devi ce shows a relative signal sensitivity of 80 dB/T at low magnetic flux dens ity B < 30 mT,quick response (greater than or equal to 40 MHz bandwidth), a nd a high-temperature stability.