Hard bubble analog multiplier

Analog multiplication of alternating currents is possible if the diameter of a moving bubble can be modulated independently of the driving field gradient. This independence can be approximated in the case of a hard bubble restricted such that the net motion is perpendicular to the gradient. In this case, the drive does not contribute to the net bias field. The restricting channel can be formed by garnet film edges. Experiments with Y-Eu garnet films and computer simulation allowed the authors to determine basic characteristics of a hard bubble multiplier device. The lowest frequency of operation is determined by the hard bubble coercivity. For presently available garnet materials, that lower limit is of the order of 1 kHz.