Echo detector having correlator with preprocessing

Abstract

An echo detector correlates between an incoming signal an echo signal to determine echo delay. A preprocesssor extracts a characteristic pattern such as a binary pattern derived by thresholding an averaged power of each signal. This pattern is down sampled then used for the correlation, and delay is deduced from peaks in the correlation. Advantages include reduced computational load, or larger correlation window size, because the characteristic pattern is easier to correlate. The quantising can enhance the correlation peaks, and the averaging can limit the number of transitions, to give more robustness to noise. An echo canceller has a coarse echo delay estimator and a fine echo delay estimator. The coarse estimated delay is used to adjust a delay detection range of a fine delay detector having a narrow range. The output of the fine detector is used to adjust or suppress the adaptive echo canceller.

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