New type (1,7) RLL partial response over 5 Gbit/in2 areal density

In this work, we consider narrow band partial response (NBPR) systems for (1,7) RLL code. As a new type of (1,7) PRML system, a PR(1,1.5,0,-1.5,-1) system called a modified MEEPR4 (MMEEPR4) which contains a spectral null below the Nyquist frequency is proposed. We compared the performances of 8/9 (0,4,4) PR4, (1,7) EEPR4, (1,7) MEEPR4 and (1,7) MMEEPR4 in recording systems with both electronic and medium noise characterized by Thurlings´ model. Medium noise power was corrected using the code magnetic transition probability. Thus the average medium noise power for code-2/3 (1,7) was 20% smaller than that of code-8/9 (0,4,4). To verify the practical use of this system, we defined the broader constraints and calculated the error propagation. It is clear that the (1,7) MEEPR4 system does not satisfy the broader constraints because it generates no quasi-catastrophic trellis sequence. Simulation results indicate that the narrow-band (1,7) MMEEPR4 system provides a significant improvement over 8/9 (0,4,4) PR4 and (1,7) EEPR4 and avoids the signal band extension for a 2/3 code-rate without a loss in performance