Unconstrained equalization method and apparatus with gain and timing bias to control runaway for direct access storage device (DASD) data channels

An unconstrained equalization apparatus for a direct access storage device (DASD) data channel including a finite impulse response (FIR) filter, a gain loop and a timing loop, said equalization apparatus comprising:

• an unconstrained equalization algorithm block coupled to the FIR filter, said unconstrained equalization algorithm block for calculating a direction for moving each of a plurality of tap weights;
• for determining new tap weights for each of a plurality of tap weights in said direction;
• and for comparing a gain of said FIR filter for said new tap weights with a set threshold gain value and for comparing a phase lag of said FIR filter for said new tap weights with a set threshold phase lag value;
• a gain control block coupled to said unconstrained equalization algorithm block for setting a polarity of a gain bias to adjust a gain of a gain loop of the data channel by a preselected amount responsive to said compared gain and set threshold gain values;
• said polarity of said gain bias being modified with successive iterations of the calculating, determining, and comparing steps of said unconstrained equalization algorithm;
• and
• a timing control block coupled to said unconstrained equalization algorithm block for setting a polarity of a timing bias to adjust a phase lag of a timing loop of said data channel by a preselected amount responsive to said compared phase lag and set threshold phase lag values;
• said polarity of said timing bias being modified with successive iterations of the calculating, determining, and comparing steps of said unconstrained equalization algorithm.

An unconstrained equalization method for a direct access storage device (DASD) data channel comprising the steps of:

• calculating a direction for moving each of a plurality of tap weights;
• determining new tap weights for each of a plurality of tap weights in said direction;
• comparing a gain of said FIR filter for said new tap weights with a set threshold gain value;
• setting a polarity of a gain bias term to adjust a gain of a gain loop of the data channel by a preselected amount responsive to said compared gain and set threshold gain values;
• said polarity of said gain bias term being modified with successive iterations of the calculating, determining, and comparing steps forcing said gain of said FIR filter close to said set threshold value;
• comparing a phase lag of said FIR filter for said new tap weights with a set threshold phase lag value;
• setting a polarity of a timing bias term to adjust a phase lag of a timing loop of said data channel by a preselected amount responsive to said compared phase lag and set threshold phase lag values;
• said polarity of said timing bias term being modified with successive iterations of the calculating, determining, and comparing steps forcing said phase lag of said FIR filter close to said set threshold phase lag value.