Magnetostrictive resonator for oscillators and narrow band filters - has rod longitudinally vibrated by magnetostriction with reduced parasitic coupling and operates in range 10khz to 100khz

摘要

The device is for use in oscillators and narrow band filters and comprises a rod (R) excited to oscillate in a longitudinal mode by two coils (E3, E4) coaxially mounted on the rod (R) on respective sides of its juncture with a thin leaf support (S1) located at a vibration node. Parasitic coupling between the coils (E3, E4) is reduced by intermediate short circuit rings. The range of operation of the device is 10KH2 to 100KH2. Polarisation of the coils (E3, E4) is effected by adjacent magnets or passage of current through the coils. In an oscillator, the coils are connected respectively to the input and output of an amplifier such that parasitic coupling is applied as negative feedback. In the presence of the magnets the rod is vibrated by the phenomenon of longitudinal magnetostriction with a stable frequency (S) at the amplifier output determined by the length and nature of the rod. Two amplifiers are used to provide a filter of bandwidth 1/600 of the frequency used.