Pattern for Buried Servo
Original Publication Date: 1980-Jun-01
Included in the Prior Art Database: 2005-Feb-13
A prior-art buried servo system uses the servo pattern shown in Fig. 1. The areas marked f(1) and f(2) have pure sine waves recorded at frequencies f(1) and f(2). Both servo and data signals are recorded using AC-bias, anhysteretic techniques. The servo frequencies, f(1) and f(2) , are much lower than the data frequencies, so servo and data signals can be separated by filtering. The position-error signal (PES) is derived from the difference in amplitudes, A(f(1)) and A(f(2)) of the f and f servo signals. Equal amplitudes [A(f(j) - A(f(2)), of the f(1) and f(2) servo exactly on track; the data tracks straddle the servo tracks. When reading or writing an even numbered data track, a positive PES [A(f(1)) - A(f(2)) > 0] means that the head is off-track in the direction of increasing track numbers.