Phase equalization for magnetic recording

The origins of phase distortion in analog magnetic recording are reviewed. These include bandlimiting, record equalization, record magnetization angle, and reproduce aperture equalization. While the magnitude of the complex frequency response for the overall record/reproduce process is maximally flat by design, the cumulative effect of the different phase distortions present is a severe linear distortion of transient signals. Reproduced transient waveforms generally are not replicas of the original input signals. Furthermore, large overshoots may occur which increase waveform peak factor. The operation and performance of several phase equalization schemes are reviewed, including conjugate filtering, first-order all-pass filters, Hilbert transformers, and cosine equalizers.