Dollar-sign transfer for magnetic bubbles

The evolution and characteristics of dollar-sign transfer gates for use in bubble mass memories are described. With this type of gate both directions of transfer require only a single conductor and unipolar current pulses. Directionality is achieved by the phase relationship between the transfer current pulse and the rotating field. It is shown that ordinarily the transfer function performs bidirectionally over the entire propagation range at current amplitudes of the order of 35 mA. Experiments on a 20 kbit chip indicate that over a range of rotating field between 25 and 35 Oe and a bias field range of 74 to 85.5 Oe, the worst-worst margins on the transfer current amplitude, phase and pulsewidth are ±14%, ±11° and ±23%, respectively.