Variable Bandwidth SAW Filter Using Magnetoelastic Coupling

The attenuation of a 600 HHz Sourface Acoustic Wave propagating through a 600 A thick nickel iron alloy and permaloy film may be changed by as much as 30 dB/cm by changing an applied magnetic field from 4 gauss to 12 gauss. Hagnetoelastic coupling is responsible for this effect. Exploitation of the effect in terms of specific SAW devices is discussed and utilization of the effect in several devices is described. The first device is a surface wave filter in which the operating frequency may be tuned by local application of the external magnetic field. The second example is a surface wave dispersive delay line where the magnetoelastic effect controls the dispersion bandwidth. These prototype devices are expected to provide data as to the usefulness of the SAW magnetoelastic effect.