Patent ID: 8077419

Claim:
A read-channel module comprising: a variable-gain amplifier module configured to amplify a signal based on a variable gain; an analog-to-digital converter module configured to generate a sample based on the amplified signal; an automatic gain control module configured to control the variable gain of the variable-gain amplifier module; a gain adjusting module configured to in response to an amplitude of the sample being less than or equal to a first predetermined threshold, generate a first gain for the automatic gain control module., wherein the automatic gain control module is configured to increase the variable gain of the variable-gain amplifier module based on the first gain, and in response to the amplitude of the sample being greater than or equal to a second predetermined threshold, generate a second gain for the automatic gain control module, wherein the automatic gain control module is configured to decrease the variable gain of the variable-gain amplifier module based on the second gain; a zero phase start module configured to generate a phase information from the sample in response to the amplitude of the sample being (i) greater than or equal to the first predetermined threshold and (ii) less than or equal to the second predetermined threshold; and an amplitude measuring module configured to measure the amplitude of the sample, and disable the zero phase start module in response to the amplitude of the sample being (i) less than or equal to the first predetermined threshold and (ii) greater than or equal to the second predetermined threshold.