Fourier synthesis of digital recording waveforms

A digital recording system is modeled by means of a complex Fourier series representation employing transforms of arctangent functions to describe the effects of write field gradient demagnetization and self-demagnetization. Pulse asymmetry and rise time effects are incorporated by means of phase shifts from complex transfer functions used in describing the dependence of head properties on a complex permeability. Experimental measurements on a specific system (Co substituted γ-Fe2O3tape and metal heads) show good correlation with the theory, especially with respect to spectral content, waveform shape, and peak shifts. The model is one-dimensional and limited to recording media initially ac demagnetized and to a write current range in which it is possible to define an effective penetration depth for saturation recording.