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-impedance (GMI) effect in a 30 /spl mu/m diameter amorphous FeCoSiBNd wire of zero magnetostriction. 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 develop a wirelessly interrogable magnetic field sensor, the combination of GMI sensors and SAW transponders is discussed by several measurements. The device shows a relative signal sensitivity of 80 dB/T at low magnetic flux density B<30 mT, quick response (/spl ges/40 MHz bandwidth), and a high-temperature stability.