Simulation of servo position error signal in perpendicular recording

We describe simulations using a medium model with random grain structure, to study the servo position error signal (PES) in a perpendicular recording system. Under various detection schemes, values of the PES null position jitter and the PES sensitivity variation at the null point are calculated. To evaluate the effect of medium noise on the PES detection, the values are compared to those of media with different average grain in-plane areas and grain size distributions. For both the PES null position jitter and the PES sensitivity variation at the null point, decreasing the average grain in-plane area or the grain size distribution yields smaller fluctuation. The servo PES has a strong dependence on the average-medium grain in-plane area. When PES of longitudinal recording systems is compared with that of perpendicular systems, perpendicular recording yields much better results because of a sharp write-field gradient at the track edge.