Performance analysis of modified PRML channels for perpendicular recording systems

Joint design of optimum partial response target and equalizer for recording channels with jitter noise

“…The model in (12) may be further approximated using Taylor expansion to derive a model similar to (6) as (14) where (15) Comparing the approximations made in deriving (6), (12), and (14), we can see that the approximate model (12) will be more accurate compared to (6) and (14) for large jitter. The simplified models are acceptable only when the standard deviation of jitter is small enough compared to the bit duration .…”

“…There have been publications on analytical approaches for the design of GPR target [10], [12]. But, these approaches are based on infinite length equalizers (i.e., joint design of infinite-length equalizer and finite-length target), even though these may be replaced/approximated by finite-length equalizers after getting the target.…”

“…This is similar to the approach used in [13], [11]. On the other hand, several papers use a different SNR definition where the noise power is taken as the sum of the powers of electronics noise and jitter noise, with the jitter noise power computed based on either single transition or multiple transitions [12], [15], [19]. Since jitter noise and electronics noise have very different effect on the detection performance, defining the SNR by adding the powers of these noises may lead to inconsistent results.…”

“…Whereas all the references quoted above deal with longitudinal recording, Sawaguchi et al [12] and Kovintavewat et al [13] presented target design approaches for perpendicular recording channels with jitter noise. While they also use the monic constraint, the targets of Sawaguchi et al [12] incorporate dc suppression of varying degrees in view of the low-frequency disturbances (e.g., jitter noise, thermal asperity, etc.) in practical channels.…”

Simplification of neural network equalizer for perpendicular magnetic recording

“…In current hard disk drives using longitudinal recording, the partial response maximum likelihood (PRML) method [2] is an indispensable signal processing method and is considered to be an important signal processing method even in perpendicular magnetic recording. Various versions of the positive coefficient PRML method have been proposed as the PRML method for perpendicular magnetic recording on a two-layer medium [3][4][5][6]. When a GMR head having a high playback sensitivity is used in perpendicular magnetic recording, the jitter medium noise produced by fluctuations in the magnetic transition point becomes dominant [7].…”