Nonlinear distortion causes significant degradation at high linear recording densities. Nonlinear distortion cannot generally be corrected by equalization and is thus particularly important to correctly identify and quantify. A technique is described which is easily applied, clearly separates linear from nonlinear effects, can be related to the underlying physical processes, and provides a good basis for modeling the channel. The technique involves the recording of a binary pseudorandom sequence and the capture and processing of the playback waveform. The technique is used to identify four distinct nonlinear effects and to examine their behavior as a function of flying height and record current.
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