Pulse superposition and high-density recording

The variation of output voltage with packing density in high-density digital tape recording has been shown to be consistent with the occurrence of a form of pulse superposition. Conditions necessaxy for this to be the superposition of isolated pulse shapes have been produced first using a model of the magnetization distribution in the tape which involves only in-plane components of magnetization and secondly using a model with a 'vector' magnetization distribution. The weakness of the theory is that it predicts symmetrical pulse shapes whereas those observed in practice are asymmetrical. Nevertheless, most of the experimental results satisfy the first derived condition, although some of the results need the assumption of certain types vector distribution, as a minimum, if they are to be explained. It is concluded, in the absence of knowledge of the real distributions, that while superposition is occurring it may not always be the superposition of isolated pulse shapes.