A hardware efficient subsample adaptive quadrature delay estimator for sinusoidal signals

An efficient real-time algorithm for estimating the subsample delay between two noisy sinusoidal signals is presented. The new technique is based on the recently proposed discrete-time quadrature delay estimator (QDE). By using all of the in-phase and quadrature-phase components of the received signals, the estimator is able to produce a bias-free estimate of the delay between the input signals. The algorithm is insensitive to variations in the amplitudes of the input signals, and does not require an accurate estimate of the frequency of the input sinusoids. In addition, the algorithm directly updates the delay error estimate, which is in turn used directly as the coefficient input to an adaptive fractional delay filter (FDF). The technique is simple to implement and outperforms other FDF-based adaptive estimators.