Signal equalization in digital magnetic recording

Abstract

The signal applied to the head in the writing process undergoes changes and distortions of various sources. Equalization must be applied to the read signal to help restore the input waveshape. The object is to improve timing accuracy which ultimately allows the use of increased bit density. An equalization method is presented in which amplitude and phase are controlled separately. The phase equalizer is adjustable, compensating for waveshape asymmetry. The networks are extremely simple and not sensitive to component tolerances. In continuous waveshape codes, such as phase recording or double frequency recording, the system is capable of compensating for considerable variations in the spacial parameters of recording. The equalization can also be used in nonreturn to zero (NRZ) code, where the ability to restore symmetry can be used to great advantage in eliminating errors.