EMC Concerns in Magnetic Bubble Memory Modules

Magnetic bubble memory devices offer nonvolatile data storage and increased storage densities over contemporary storage devices; they are being manufactured in production quantities by a number of sources world wide. The devices are small and use low signal levels; for operation, they require a unique set of conditions quite different from those required by their semiconductor predecessors. In particular, permanent (static) and rotational (dynamic) orthogonal magnetic fields are necessary to sustain and propagate magnetic bubble domains along permalloy patterns. Bubble domains must be generated, directed, and annihilated on a uniaxial magnetic film in a prescribed manner. Unlike semiconductors, bubble memory devices do not employ p-n junctions. Detection of low-level bubble signals is typically accomplished with magnetoresistive techniques. This paper describes basic bubble memory operation, identifies conditions necessary for memory operation, and presents EMC (electromagnetic compatibility) concerns of a magnetic bubble memory module. EMC concerns of the module are discussed from two aspects: internal compatibility, which considers inherent factors that compromise bubble detection in the unique operation environment; and external compatibility, which considers electromagnetic factors of the outside environment in which the module must satisfactorily operate.