Error signal biasing for an adaptive filter in a disk drive read channel

A disk drive system comprising:

• a disk device operational to store data and transfer an analog signal representing the data;
• and
• control circuitry operational to receive the analog signal, convert the analog signal into a digital signal, transfer the digital signal, and bias an error signal used to adjust coefficients for an adaptive filter, wherein the control circuitry comprises a disk drive controller operational to manage data transfers, read channel circuitry operational to convert the analog signal into the digital signal, and servo circuitry operational to control positioning of the disk device, and wherein the read channel circuitry further comprises:
• an analog-to-digital converter operational to receive and sample the analog signal to generate a sampled signal;
• the adaptive filter is operational to shape the sampled signal based the coefficients to produce a shaped signal;
• a decoder operational to process the shaped signal to generate the digital signal;
• and
• error signal circuitry operational to bias the error signal.

A method for operating a disk drive system comprising:

• transferring an analog signal representing data stored on a disk device;
• receiving the analog signal;
• sampling the analog signal to generate a sampled signal;
• shaping the sampled signal in the adaptive filter based on the coefficients to produce a shaped signal;
• decoding the shaped signal to generate a digital signal. transferring the digital signal;
• and biasing an error signal used to adjust coefficients in an adaptive filter.