公开(公告)号：SG92795A1

公开(公告)日：2002-11-19

申请号：SG200102477

申请日：2001-04-18

Applicant: IBM

Inventor： CHAD EDWARD MITCHELL ,  RICK ALLEN PHILPOTT ,  JAYDIP BHAUMIK ,  RAYMOND ALAN RICHETTA

IPC: G11B5/00 ,  G11B5/09 ,  G11B20/10

Abstract: A system and method provides for calibrating a corner frequency of a tunable filter coupled to a read channel of a data storage system to a desired frequency. A signal having a frequency equal to the target corner frequency is generated. A gain of the signal is adjusted to a gain threshold. The gain of the signal is then increased from the gain threshold by a pre-established amount, such as by 3 dB. The corner frequency of the signal is shifted until the gain of the signal is substantially equal to the gain threshold, at which point the corner frequency of the tunable filter is calibrated to the desired frequency. The signal generated is a peak-detectable signal. The corner frequency of a tunable filter may be a low or high corner frequency appropriate for filtering a data signal or a servo signal. The corner frequency calibration circuitry may be implemented in-situ the read channel circuitry of a data storage system.

公开(公告)号：SG80647A1

公开(公告)日：2001-05-22

申请号：SG1999004464

申请日：1999-09-10

Applicant: IBM

Inventor： RICK ALLEN PHILPOTT ,  GREGORY SCOTT WINN

IPC: G11B5/00 ,  G11B5/39 ,  G11B5/455 ,  G11B19/04 ,  G11B7/09 ,  G11B20/10 ,  G11B27/36

Abstract: An apparatus and method for measuring an amplitude of a readback signal obtained from a data storage medium involves transmitting the readback signal to a gain modifying amplifier, such as a variable gain amplifier (VGA)(76), preferably provided in the read channel. A voltage signal associated with a loop gain of the amplification circuitry is sensed and compared with a number of control voltage signals, each of the control voltage signals being associated with a corresponding digital word value. The digital word value associated with a control voltage signal that is equal to the sensed voltage signal represents the relative amplitude of the readback signal. Gain characterization circuitry may further be combined with readback signal amplitude measuring circuitry (75), preferably in-situ a read channel, to obtain the absolute amplitude of a readback signal. Gain characteristics of the amplification circuitry are determined by applying reference voltage signals associated with corresponding pre-established gain values to the signal input of the gain modifying amplifier. A control voltage signal is selectively applied to the amplifier for each of the reference voltage signals until the amplifier output voltage signal is substantially equal to a pre-established reference voltage signal. Amplitude measurements may thereafter be taken to obtain the absolute amplitude of readback signals. Readback signal amplitude measurements may be performed when the read channel is in a read mode, idle mode, or servo mode of operation.