A far-end echo canceller with a digital filter for simulating a far end echo containing a frequency offset

摘要

A far-end echo path may be simulated at a terminal which utilizes QAM by processing the in-phase and quadrature data symbols by a pulse shaping filter whose transfer function may be a raised cosine function. The in-phase and quadrature data symbols are then multiplied by cos ((omega)c+(omega)o)t and sin ((omega)c+(omega)o)t, respectively, where (omega)c is the carrier frequency and (omega)o is the adaptively determined offset frequency of the far-end echo signal. The output signals of the multipliers are then summed and the result is processed by a single transversal filter whose transfer function is determined adaptively. The output of this filter is a simulated far-end echo signal.