Switchable Time-Domain Filter
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
The data channel in a disk drive includes a time-domain filter. The optimum value of time delay used for data read at the outer radius of the disk is usually not the optimum value for data read at the inner radius. At the inner radius, shifted bits due to intersymbol interference, are the major contributor to the soft error rate. Therefore, excess time-domain filter delay will only aggravate the situation by forcing data bits into adjacent variable frequency oscillator (VFO) windows. However, at the outer diameter, high disk resolution and wider bit spacing are the major contributors to the soft error rate in the disguise of extra bits. Additionally, excess system noise will aggravate the problem by "riding" on the flat waveform between two data bits, thereby influencing the differentiator/zero-crossing detector.