Thermal asperity suppression in perpendicular recording channels

In this paper, we present an approach for detection and suppression of thermal asperity (TA) induced signal distortions in perpendicular recording channels. When the MR read head comes in contact with the disk surface, the resulting thermal transient causes a change in the resistance of the MR read element. This change in the resistance manifests as an additive voltage transient in the readback signal. Typically, a TA signal has a short rise time (60-150 ns) with a longer decay time (1-5 μs). The peak TA amplitude can be as large as 250%. If precautions are not taken, such transients could cause sector read failure. As the flying height continues to decrease and as the recording density continues to increase, the adverse effects of TA will become even more serious in future drives. Thus, it is particularly important to develop means to handle TA effectively in perpendicular recording channels. The study shows that the proposed method is robust with respect to the changes of the peak TA amplitude and to the mismatch between estimated and actual TA durations. Thus, in conclusion, we have developed an easily implementable and effective TA detection and mitigation approach for perpendicular recording channels.