A data recording system, such as a magnetic recording hard disk drive, has a
recording
medium in which the data tracks have pseudo-random binary sequences for the servo
information used to control the position of the recording head. A first pseudo-random
binary sequence (PRBS) and a second PRBS identical to the first PRBS but shifted
by a portion of the period of the first PRBS are located between the track boundaries
in alternating tracks in a first region of the servo pattern and between the track
centers in alternating tracks in a second region spaced along the track from said
first region. A servo decoder has two correlators, one for each PRBS. Each correlator
outputs a dipulse when its PRBS repeats. The difference in amplitude of the dipulses
represents the head position signal. The dipulses also control the amplifier for
the signal read back by the head and the timing of the track identification (TID) detector.