Method using matched filters for determining head positioner micro-jog in hard disk drive employing magneto-resistive heads

A disk drive comprising:

• a rotatable magnetic data storage disk;
• at least one data transducer assembly controllably positionable at concentric positions adjacent the disk by a rotary actuator, the data transducer including a magneto-resistive read, inductive write transducer head assembly;
• read channel electronics coupled to the transducer assembly and including a partial response detector having a filter for generating digital sample responsive to read signals during disk drive data read operations;
• means for recording a predetermined interference bit pattern onto each of first and second interference positions radially offset to respective sides of a selected track on the data storage disk;
• means for recording a predetermined test bit pattern onto the selected track of the disk, the test bit pattern having a selected frequency higher than the interference bit pattern frequency;
• control means for setting the read channel gain loop to a predetermined fixed gain mode of operation while reading the selected track;
• means for generating a first digital test signal having a frequency equal to the test bit pattern frequency;
• a first correlation circuit for correlating the first digital test signal to the digital samples generated by the partial response detector while reading the selected track;
• means for generating a second digital test signal that is 90 degrees out of phase relative to the first digital test signal;
• a second correlation circuit for correlating the second digital test signal to the digital samples generated by the partial response detector while reading the selected track;
• and
• means for combining the outputs of the first and second correlation circuits to form an indication of the amount of interference energy resulting from the recorded interference bit patterns at a selected lateral position of the head assembly, for use in locating a lateral position of the head assembly where said interference energy is minimized.

In a disk drive having a magneto-resistive read, inductive write transducer head assembly coupled to a read channel including a partial response detector, the partial response detector having an automatic gain loop and a FIR filter, a method of estimating a micro-jog distance for a selected track on the disk drive recording media, the selected track having a nominal centerline location and track pitch and the method comprising the steps of:

• recording a first test bit pattern onto the selected track;
• laterally positioning the transducer head assembly over the selected track;
• disabling the automatic gain loop in the partial response detector so that it has a predetermined, fixed gain value;
• setting the FIR filter so as to operate in a static mode;
• reading the selected track, thereby forming a series of equalized samples at the output of the FIR filter responsive to the recorded first test bit pattern;
• matched filtering the equalized samples to form an indication of an average energy of the detected signal over the length of the first test bit pattern;
• repositioning the head assembly;
• and
• repeating said reading, material filtering and repositioning steps so as to determined a lateral position of the head assembly at which the detector signal strength is maximized;
• and then
• selecting as the micro-jog distance a distance that positions the head assembly at said position where the detected on-track signal strength is maximized during a read operation.

A disk drive comprising:

• a rotatable magnetic data storage disk;
• at least one magneto-resistive read, inductive write transducer head assembly controllably positionable at concentric track locations over the disk by a rotary actuator;
• read channel electronics coupled to the transducer head assembly including a partial response detector for generating digital samples responsive to read signals during disk drive data read operations;
• control means for setting the read channel gain loop to a predetermined fixed gain mode of operation while reading a selected track of the disk;
• means for generating a first noiseless digital test signal having a pattern frequency equal to the pattern frequency of an interference bit pattern prerecorded on the disk laterally offset from the selected track centerline;
• a first correlation circuit coupled to the read channel and to the first digital test signal generating means for correlating the digital samples generated by the partial response detector to the first digital test signal while reading the selected track;
• means for generating a second noiseless digital test signal having a pattern frequency equal to the pattern frequency of the interference bit pattern, the second digital test signal being 90 degrees out of phase relative to the first digital test signal;
• a second correlation circuit coupled to the read channel and to the second digital test signal generating means for correlating the digital samples generated by the partial response detector to the second digital test signal while reading the selected track;
• means for combining output signals from the first and second correlation circuits to form an indication of an amount of interference energy resulting from the prerecorded interference bit patterns for use in locating a lateral position of the transducer head assembly where said interference energy is minimized;
• and
• means for measuring on-track read signal energy resulting from an on-track bit pattern prerecorded on the selected track while minimizing interference from the interference bit pattern.