The performance of the track-follow and reel-to-reel servo systems is ultimately limited by the resolution and bandwidth of the velocity and position signals provided by the servo channel, which are in turn related to the geometry of the servo pattern. Figure 1 illustrates the basic format of the pattern used in LTO1-LTO4 tape drives.
Currently, we are investigating alternative servo geometries (azimuth angle, transition width and period) in order to optimize the resolution and bandwidth of the servo signals. To optimize performance, the characteristics of the servo channel and the magnetic media have to be taken into account, and the geometry of the servo reader must be optimized for a given pattern. Figure 2 shows an example of the standard LTO servo pattern written with an azimuth angle of 6 degrees and an experimental pattern written with an angle of 12 degrees.
Our goal is to improve the resolution of the servo signal down to the nanometer scale by jointly optimizing the servo pattern, servo channel, and servo reader.