MATCHED-FILTER LIMITS AND CODE PERFORMANCE IN DIGITAL MAGNETIC RECORDING

This tutorial-level paper presents a method for evaluating the performance of recording channels and codes for systems with additive spectral Gaussian noise. Starting with a noise-whitened isolated pulse, matched filters are calculated for the amplitude and timing channels which have the maximum signal-to-noise ratio (SNR) and minimum jitter, respectively. In high density recording systems, the pulse slimming equalization required to control intersymbol interference degrades the SNR and jitter. For the timing channel, a detector SNR, SNR(D), is defined whose error statistics are nearly identical to the amplitude channel SNR. Procedures for calculating losses relative to the matched filter SNR are developed that facilitate performance comparisons of both channels. A series of runs for the Lorentzian input pulse and cos equalized output pulses compares the performance of several modulation codes and detection techniques. Write equalization and partial response type 4 equalization are also examined.