PERFORMANCE OF PARTIAL-RESPONSE SYSTEM IN PERPENDICULAR MAGNETIC RECORDING

The error-rate performance of the partial response maximum likelihood (PRML) system combining the partial response (PR) system with the Vite rbi decoding, which is a type of maximum likelihood (ML) decoding, is investigated in perpendicular magnetic recording using a multilayered main-pole head. Waveform approximation is carried out with regard to t he isolated reproducing waveform obtained by experiment; and, based on this, the bit error rate is determined by computer simulation. First, taking into account the noise increase due to equalization, the signa l-to-noise ratio (SNR) at the discrimination point and the bit error r ates of bit-by-bit decoding of several PR systems using the characteri stics of the multilayered main-pole head are determined. Next, the bit error rates of the PRML system are determined for these PR systems an d then compared with those for the conventional PR system. Then it is clarified that the best performance is obtained by the PR(1, 0, 0, 0, -1) system among these PR systems, and the improvement of SNR compared with the conventional PR system is about 1.9 dB in the case of the bi t-by-bit decoding system and 4. 1 dB in the case of the PRML system at an error rate of 10(-4).