Adaptive optimum cdr bandwidth estimation by using a kalman gain extractor

Abstract

Exemplary embodiments of the present invention relate to a clock and data recovery (CDR) apparatus with adaptive optimum CDR bandwidth estimation by using a Kalman gain extractor. The Kalman gain extractor includes an off chip digital processor which receives a phase update information from the CDR outputs an estimated optimum Kalman gain obtained by extracting the standard deviation of step sizes of the accumulation jitter from the power spectral density (PSD) of the phase update information, and a on chip digital loop filter consists of a cyclic accumulator which accumulates the phase detector's output, a gain multiplier and a phase interpolator (or DCO) controller. The off chip digital processor includes a storage register, a fast Fourier transform (FFT) processor and an optimum Kalman gain estimator. The storage register stores the phase update information, from which the FFT processor extracts the PSD of the absolute input jitter. The optimum Kalman gain estimator calculates the optimum gain from the PSD of the accumulation jitter. The off chip digital processor may further include a gain calibrator to compensate for the variations in the transition density.