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Browsing by Subject "Two dimensional magnetic recording"

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    System study of two dimensional magnetic recording system
    (2014-08) Wang, Yao
    Two-dimensional magnetic recording (TDMR) has been proposed as a promising approach for ultra-high densities towards 10 Tbits/in2. How to effectively write and detect the data to reach such a high density is a challenge. For read back and detection process, a novel system design for sensing very high density magnetic recording data is investigated. The rotated single head (RSH) with oversampled signals, minimum mean squared error equalizers and pattern-dependent noise prediction detector has been proposed. The bit error rate (BER) can be decreased by a factor of 5 compared to a normally oriented head array, increasing user bit density to 10.04 Tbits/in2 with conventional media. Simulation indicates that a rotated head achieves a density gain of 1.7x (single head) or 2.1x (array) over a normally oriented single head (NSH) at a target BER of 10-3 with sampling period of 2nm. The study indicates that the significant improvement in performance of the rotated head compared to the normally oriented head can be attributed to the larger amplitude of its dibit response and the reduced overlap between conditional probability density functions. The proposed reader has been also applied to bit patterned magnetic recording: it has more than 20 dB gain compared to a normally oriented head array for reading back at 10 Tbits/in2. For the writing process, micromagnetic writing on 8nm grains and readback with various readers has also been studied. For a conventional writer recording a pseudo-random binary sequence with 2 Tbits/in2 channel bit density, user densities of 1.52 Tbits/in2 and 1.09 Tbits/in2 can be achieved with a RSH and a NSH, respectively, using oversampling signal processing. Simulation indicates that a RSH with multiple scans and 2D equalization provides better resistance to a skew angle of 15° than NSH. An optimized shingled writer is proposed; simulation indicates that a RSH and rotated head array can reach a user areal density of 3.76 and 4.52 Tbits/in2 for 2 grains per channel bit, which is close to the predicted maximum user areal density (4.66 Tbits/in2) for this grain size obtained with an ideal writer and reader.