Frequency-domain echo canceller with phase adjustment

The frequency-domain filter is an efficient realization of an echo canceller that provides a simple and elegant solution to the problem of jitter compensation. An essential requirement for a low-error digital transmission system is that the echo canceller retains high accuracy while the sampling instant is being adjusted. One of the most attractive features of discrete Fourier transform is its capacity to reconstruct time-shifted signals using phase shifts in the frequency-domain. The signals involved, however, are not always alias-free (nor are they in telecommunications), which seriously degrades the echo cancellation. This paper introduces a de-aliasing technique, which results in an algorithm that is largely insensitive to the spectral content of cancelled signals. The de-aliasing technique allows preservation of high-performance echo cancellation during rapid changes in the sampling phase of the input signal. Computer simulations confirm the theoretically predicted behavior and accuracy.