Schneider write equalization has been proposed in some digital recording systems. In this paper, a class of Schneider write equalizers with zero degree phase shift and with added pulse width equal to T/M (M is an integer greater than 1, M greater than or equal to 2) for the (1, k) peak detection recording channel will be investigated. The effects of the equalizers on the linear peak shift and resolution for (1, 7) RLL sequences will be studied, and the capacity of the equalized recording channel will be compared, under the assumption of an ideal Lorentzian channel model. One of the equalizers with added pulse width T/2 together with a 2/3 (1, 7) RLL code is applied to an R-DAT (rotary head-digital audio tape recorder) and results show improvement in recording density and data transfer rate over an 8/10 (0, 3) dc-free code. This class of equalizer together with a (1, k) RLL sequence can be described as a new modulation sequence and the power spectrum will be computed based on the new modulation sequence. As added pulses of this class of equalizers are very narrow, especially for large M, the linear channel model might not be accurate because of nonlinear distortion due to inadequate write current risetime and/or to the demagnetization field from recorded transitions. Hardware implementations of the equalizers, including compensation for nonlinear effects introduced in the recording process, will be considered.
