The impact of GMR baseline popping noise on the servo position error signal of a hard disk drive

Baseline popping noise (BLPN) is one of the major types of instability in a GMR head, and it is often shown as "popping" of the baseline between isolated pulses. From the experiment, BLPN is still a problem in the servo frequency range (10-15 MHz). The offtrack performance of a high BLPN head and the impact of BLPN on a HDD position error signal (PES) are studied in this paper. Generally, burst average amplitude (BAA) rises when the unstable permanent magnet is in the track, especially at the track edge. The head PES is distorted and its linear range could be significantly reduced because of BLPN. A simple model is introduced to analyze it. When the servo tolerance is known, it can be used to scan the head at component level with spin stand.