Simulation of dual conductor current access magnetic bubble devices

A simulator for current-accessed dual-conductor magnetic bubble technology was implemented on a single-user graphics minicomputer and used to develop an exclusive or (XOR) logic gate and a bubble CROSSOVER circuit employing bubble-bubble interaction effects. Using the simulator, a designer can layout a chip on the graphics terminal, insert simulated bubbles into the device, and observe device operation and failure mechanisms (e.g. failure to propagate or bubble collapse), much as one presently observes failures in fabricated devices using magneto-optic techniques. The simulator program computes the currents in a conductor sheet with an arbitrary pattern of apertures using finite element techniques. Knowing the currents, the fields in the underlying magnetic bubble layer are calculated. Bubble-bubble interaction effects are taken into account by computing the fields of interacting bubbles. Bubble size is determined by a balance of forces from wall energy, magnetostatic energy, and energy from the bias field, currents, and bubble-bubble interaction fields. Materials parameters such as magnetization, film thickness, wall energy, coercivity, and mobility are all explicitly taken into account in the simulated device operation.