Bit Error Rate Evaluation of MR Heads through a PRML Read Channel

Joichiro EZAKI
1994 Journal of the Magnetics Society of Japan  
Bit error rates of magnetoresistive heads (MR heads) were evaluated through a partial response maximum likelihood (PRML) read channel. The heads were characterized by utilizing technologies of a shared pole structure, a soft adjacent layer (SAL) for the transverse biasing, and the Fe-Mn boundary controlled stabilizer (BCS) for the Barkhausen noise suppression purpose. The PRML read channel consisted of a sampled data read channel with Viterbi detection, a programmable filter/equalizer for
more » ... l response class 4, a three tap transversal filter for adaptive equalization and an 8/9 GCR encoder/decoder. Two of the key read/write parameters, the amplitude asymmetry of the readback pulses, which is unique to the magnetoresistive read-out process, and the nonlinear transition shift (NLTS) as the critical measure for the PRML application, were selected for the main objects of the evaluation. Their effect on the bit error rates was investigated. The amplitude asymmetry was found not to deteriorate the bit error rates as long as it was kept approximately within ±15%. However, the error rates rapidly degraded as the asymmetry increased to around 20 % or more. The NLTS due to the less steep gradient of the trailing write field caused by the pole tip saturation, was found to affect and degrade the error rates, significantly. It was also found that the error rate deterioration caused by the NLTS could be effectively suppressed by the write pre-compensation.
doi:10.3379/jmsjmag.18.s1_365 fatcat:xqvv4m5zabdy3ikjht4m6znomy