MULTIPLE POLE HIGH PASS THERMAL SPIKE FILTER FOR TAPE CHANNELS
Original Publication Date: 2000-Feb-01
Included in the Prior Art Database: 2003-Jun-19
Thermal spikes (or thermal asperities) occur in magnetic tape and disk channels which use MR heads when a defect or debris on the media hits the MR head. This causes localized heating of the MR element which changes its resistance to increase and results in a transient in the detected signal. The transient is characterized by fast rise times and slow decay times as the localized heating dissipates. The transient causes the baseline of the signal to shift, often to levels several times the amplitude of the signal. Such shifts cause the data detector in the channel to make errors. The filter described here attenuates the low frequency energy associated with the thermal spike minimizing its effect on the error rate of the channel. Tape and disk channels typically have a single pole high pass filter to attenuate thermal spikes. Typically this is a simple RC filter formed by the coupling capacitors into the preamplifier and the input resistance of the preamplifier. 1 The figure below shows the wave form from an analog simulation showing the effect of a single and a double pole high pass filter on the output wave form during a thermal spike.