Frequency-modulation type magnetic field sensor using transmission-line magnetic device

A novel frequency-modulation type magnetic field sensor composed of transmission-line magnetic device and phase-shift type oscillator has been developed. The transmission line magnetic device consists of soft magnetic layers, dielectric layers and conductor lines, which operate as a distributed constant circuit. The transmission characteristics such as voltage-gain and phase are influenced by permeability change due to the external magnetic field applied to the magnetic layer. A transmission-line device developed by using Co based amorphous ribbon was used in the feedback circuit of a phase-shift type oscillator. The oscillation frequency of the oscillator increased with increasing magnetic field.