Automatically adjusting gain/bandwidth loop filter

摘要

An automatically adjusting gain/bandwidth loop filter suitable for a digital phase lock loop or a digital adaptive carrier recovery loop with variable loop gain/bandwidth for rapid acquisition and lower steady-state jitter is provided. The automatically adjusting gain/bandwidth loop filter comprises a variable gain/bandwidth loop filter, a tracking status detector and a gain/bandwidth control state machine. The tracking status detector observes the frequency error which is the output of the frequency tracking (integral) branch of the variable gain/bandwidth loop filter, then it outputs a tracking state of the carrier recovery loop. The loop gain/bandwidth is then adjusted by the gain/bandwidth control state machine in response of the tracking state to improve the pull-in time and steady-state carrier frequency jitter.