Cooper & Dunham LLP
Method and apparatus for the compensation of an additive signal in a data signal
 The method and apparatus have application to the compensation of transient signals produced on reading a data storage device with a magneto-resistive head due to thermal contact with asperities on the data storage medium. Preferably, the data channel employs partial-response maximum-likelihood detection. The method compensates for an additive signal in a data signal and comprises the steps of: detecting the contribution to said data signal by said additive signal; initially compensating the data signal by maintaining a DC offset in said data signal, the initial level of said DC offset being set in dependence on the detected contribution; and while compensating the data signal, detecting when the compensated data signal exceeds a predetermined threshold and varying the set level of said DC offset in dependence upon said detection. 
Data Storage Institute
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Srinivasan Yuan Xing Bin
Gopalaswamy Lee Liu