Quad Burst Servo Pattern
Original Publication Date: 1980-May-01
Included in the Prior Art Database: 2005-Feb-13
The prior art quad-burst servo pattern of Fig. 1 offers many advantages, such as a continuous linear position error signal (PES) over the entire track ranges, an extension of off-track capability to one-half track pitch, less sensitivity to servo head pole tip width variations, a narrower spread of the servo frequency spectrum and the generation of electronic tachometer pulses. However, it has the following disadvantages: 1. It is sensitive to noise pick-up because more than half of the servo surface is unused magnetically. 2. The servo sampling rate is inherently lower because PES is generated by comparing the demodulated signal of the alternate bursts, such as A and B; C and D. 3. Circuit gain imbalance of the two PES channels results in a built-in offset error.