Performance of recording channels employing partial response signaling

Performance of magnetic recording channels employing partial response signaling is investigated. It is shown that for the case of the Lorentzian channel, with additive white Gaussian noise, a closed form expression for the signal-to-noise ratio (SNR) can be obtained. It is demonstrated that at high densities, higher order partial response (PR) systems have less equalization loss. The off-track interference is analyzed by examining the free distance of sequences at the input to the Viterbi detector. It is shown that higher order PR systems are more sensitive to off-track noise. We use the method developed here to compare PR systems with three types of modulation coding, i.e., d=O, d=1, and trellis codes. Further analysis, based on the slope of the obtained performance curve, is used to determine the optimal linear and track densities to achieve an overall areal density given an SNR budget