Unconstrained optimization for parameter estimation of closely spaced tones

In this paper the methods for estimating the parameters of two closely spaced tones in frequency are presented. They are iterative procedures posed as an optimization problem. Both first and second order methods in combination with the corresponding tone estimation techniques are treated in order to circumvent the problem of interharmonic interference. It is shown that the convergence can be achieved for the frequency separation less then a bin within the limited number of iterations.