A linearly constrained adaptive FIR filter for hard disk drive read channels

The interactions between an adaptive FIR filter, the automatic gain control (AGC), and the phase-locked loop (PLL) timing recovery in hard disk read-channels can cause the adaptive process to become unstable. Sometimes simple adaptive filter tap constraints can be used to combat these adverse interactions, but tap constraints do not always work. In this paper we present a rank 2 linearly constrained adaptive algorithm that effectively eliminates the adverse interactions between the adaptive FIR filter the AGC, and the PLL in hard disk read-channel applications