Method and apparatus for data detection for PRML data channels

Apparatus for data detection for a partial-response maximum-likelihood (PRML) data detection channel in a direct access storage device comprising:

• an input providing a class-IV partial response (PR4) signal;
• a PR4 Viterbi detector receiving the PR4 signal and providing a PR4 Viterbi output;
• a first matching delay means for receiving the PR4 signal and for providing a delayed PR4 signal;
• adder means for subtracting said PR4 Viterbi output from said delayed PR4 signal and for providing a resulting signal;
• a first filter having a frequency response of 1/(1-.alpha.D.sup.2) receiving said resulting signal and providing a filtered signal;
• a second filter receiving said filtered signal and providing a second filtered output signal;
• a second matching delay means for receiving said PR4 Viterbi output and providing a delayed PR4 Viterbi output;
• and
• correcting means for correcting said delayed PR4 Viterbi output responsive to said second filtered output signal.

A method for data detection for a partial-response maximum-likelihood (PRML) data detection channel in a direct access storage device, said method comprising the steps of:

• receiving a class-IV partial response (PR4) signal;
• applying the received PR4 signal to a PR4 Viterbi detector to provide a PR4 Viterbi output;
• applying the received PR4 signal to a first matching delay circuit to provide a delayed PR4 signal;
• subtracting said PR4 Viterbi output from said delayed PR4 signal to provide a resulting signal;
• applying the resulting signal to a first infinite impulse response (IIR) filter having a frequency response of 1/(1-.alpha.D.sup.2) to provide a filtered signal;
• applying the filtered signal to a second matched filter for identifying a dominant error event;
• applying said PR4 Viterbi output to a second matching delay circuit to provide a delayed PR4 Viterbi output signal;
• and
• correcting said delayed PR4 Viterbi output responsive to an identified dominant error event by said second matched filter.

Apparatus for data detection for a partial-response maximum-likelihood (PRML) data detection channel in a direct access storage device comprising:

• an input providing a class-IV partial response (PR4) signal;
• a PR4 Viterbi detector receiving the PR4 signal and providing a PR4 Viterbi output;
• a first matching delay means for receiving the PR4 signal and for providing a delayed PR4 signal;
• adder means for subtracting said PR4 Viterbi output from said delayed PR4 signal and for providing a resulting signal;
• a filter having a frequency response of ##EQU5## receiving said resulting signal and providing a filtered signal;
• said filter combined with an error event filter providing an error output signal;
• a second matching delay means for receiving said PR4 Viterbi output and providing a delayed PR4 Viterbi output;
• and
• correcting means for correcting said delayed PR4 Viterbi output responsive to said error output signal.