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In this analysis we studied the potential field around a perpendicular recording head by a Fourier method. As this potential function obtained is easy to operate, the wavelength response of the head can be calculated and is shown to be similar to that of a ring head for a recorded sine wave. The first term of our expansion of the flux through the head turned out to be sinx/x. This term is nominally not affected by spacing; thus,the head has good reliability. We built some perpendicular recording heads and obtained a reasonably good response curve as illustrated. However, we find the main drawback of such a head, in a standard tape system, lies with the recording process, i.e., a wavelength loss on tape rather than a limitation of the playback head. Since there is no essential difference between sine-wave and digital recording, the analysis can easily be extended to a digital system.
George J. Y. Fan (Sun,) studied this question.