Patent ID: 7724636
Filing Date: 2010-05-25
Classification: G11B,H04L

Abstract:
1. An asymmetry compensator used in a partial response maximum likelihood (PRML) decoder, which is used to eliminate an asymmetric component in a regenerating signal read from an optical recording medium, comprising: an offset controller arranged to determine a central level of said regenerating signal, and adjust an offset of said regenerating signal according to said central level, said offset controller including: an adder for adding said regenerating signal read from said optical recording medium to said offset to generate an added signal, said added signal corresponds to the regenerating signal having the adjusted offset; a comparator, connected to said adder, and arranged to determine whether a central level of said added signal is greater or less than 0, if it is greater than 0, then output the determination signal having a logic value 1, otherwise output the determination signal having a logic value −1; a first integrator, used to receive said determination signal, and successively add said added signal to generate a corresponding first integration signal; and a first controller, used to multiply said first integration signal with a multiplier to generate said offset; and a gain controller, connected to said offset controller, and is arranged to adjust a gain of said regenerating signal thereby to output said regenerating signal without the asymmetric component, said gain controller including: a second integrator, arranged to add successively the regenerating signal not having the asymmetric component, to generate a corresponding second integration signal; a second controller, arranged to be connected to said second integrator, and multiply said second integration signal with a multiplier to generate an operation signal; and an calculator, arranged to output an asymmetric gain signal based on said determination signal and said operation signal, wherein, when the determination signal is 1, said calculator is arranged to subtract said operation signal from 1 to obtain said asymmetric gain signal, and when the determination signal is −1, said calculator is arranged to add 1 to said operation signal to obtain said asymmetric gain signal.