Pulse shape, resolution, and signal-to-noise ratio in perpendicular recording

Read and write processes, and head technology for perpendicular recording

“…For perpendicular media with realistic grains size distributions and with random grain locations, the minimum transition parameter is a$D=p [23], and the cross-track correlation width is larger than the grain diameter, s c XD, for almost all kinds of media, and s c further increases with medium intergranular exchange [23][24][25][26][27]. This leads us to the fundamental conclusion that higher media SNR requires smaller grain size for magnetic recording.…”

“…The noise power, on the other hand, is proportional to the variance of the magnetization at a transition boundary. By using the square of the definition of a maximum signal from an isolated transition and dividing this by the root-mean-square (rms) transition noise in square wave recording at given bit separation B, we obtain [24] …”

Modeling of the nonlinear perpendicular recording readback signal

“…We can also observe that the tail on the left is also longer than 9 channel bit durations. This effect called ''droop'' is unique to the perpendicular recording signals [2] and is predominantly a linear effect that lengthens both tails of the dibit response.…”

“…The Volterra Model (VM) used to model longitudinal recording readback signals [1] is an inadequate model for keepered perpendicular recording because unlike longitudinal recording, the linear response in keepered perpendicular recording suffers from very long inter-symbol interference (ISI) due to the presence of ''droop'' [2] and the presence of a high pass filter in the preamplifier. The long ISI translates into a requirement of a large memory length L for the VM in order to avoid truncation errors that cause a lack of fit [3].…”

Readback Responses for Complex Recording Media Configurations

“…A number of approaches for generating increasingly accurate and fast approximations have been developed [4]- [8]. These have included configurations for perpendicular recording, where a soft underlayer is included [9]- [11]. However, this prior work has tended to describe relatively simple configurations with isotropic permeability and a minimum of layers: for example, longitudinal media with no soft underlayer or perpendicular media with an ideal soft underlayer.…”