A PRML with modified branches of a dual MTR code for high-density PMR channels

Maximum transition run (MTR, j) code is a modulation code that limits the consecutive transitions. We present a dual MTR code that can be applicable to high-density perpendicular magnetic recording (PMR) channels. The code restricts j=2 in each codeword and allows j=3 when codewords are connected. Furthermore, to improve the detection performance of the PMR systems, we propose a partial response maximum likelihood (PRML) detection scheme with modified branches of the Viterbi trellis for the code. The PRML detection of the dual MTR code achieves an SNR gain of more than 2 and 0.3 dB over the conventional fourth-order PRML detections with rate 8/9 code and rate 6/7 MTR (j=2) code at 10−5 bit error rate (BER) in the PMR channel model, respectively.