Comparison Of Equalization & Detection For Very High Density Magnetic Recording

As linear densities increase in magnetic storage, media noise and signal nonlinearity begin to substantially inhibit the performance of various detection schemes[l][2]. NonLinear Transition Shift (NLTS) can usually be mitigated during the write process (write precompensation). However, nonlinear amplitude loss (partial erasure) due to the percolation of neighboring domains and transition broadening can only be dealt with during readback. To obtain acceptable bit error rates in the face of these high-density effects, one must understand their impact on equalization and detection schemes currently in use. This paper compares the performance of EPR4 equalization with Viterbi detection to FDTS/DF (tree-depth 2) on high-density magnetic data via simulations. The data used for the comparison was collected directly from a spin stand using a digitizing oscilloscope. The head and media used were specifically manufactured for high linear density recording. In addition to the above comparison, FDTSDF simulations were run using a modified branch metric in the tree search. The metric incorporates an extra term that accounts for pattern-dependent media noise.