ON THE INSTANTANEOUS FREQUENCY SMOOTHING FOR SIGNALS WITH QUASI-LINEAR FREQUENCY CHANGES

The problem of estimation of the slowly-varying instantaneous frequency of a nonstationary complex sinusoidal signal buried in noise is considered. This problem is usually solved using frequency tracking algorithms. It is shown that the accuracy of frequency estimates can be considerably increased if the results yielded by the frequency tracker are further processed using the appropriately designed filters. The resulting frequency smoother can be employed in many off-line applications. Whenever signal frequency varies in a sufficiently smooth manner, the proposed algorithm, based on a new, quasi-linear model of frequency changes, outperforms the existing solutions.