Patent ID: 6546057
Filing Date: 2003-04-08
Classification: H04B,H04L

Abstract:
Noise suppression apparatus for a communications channel (10), comprising:(i) a hybrid device (11) for coupling to the channel for providing a differential signal corresponding to a signal received from the channel; (ii) extraction means (13) for coupling to the channel for extracting a common mode signal from said channel; (iii) a noise estimation unit (15,16,17) comprising means (15,20) for deriving from said common mode signal a plurality of digital signals (S1, . . . , SM) each representing a different one of a plurality of frequency bands of the common mode signal and a plurality of noise detection means (231, . . . , 23M) for deriving from the digital signals (S1, . . . , SM) a plurality of noise estimate signals (E1, . . . , EM), respectively; (iv) means (24) for combining selected samples of the noise estimate signals (E1, . . . , EM) to provide a common mode noise estimate signal (ECM); (v) a delay unit (12) coupled to an output of the hybrid device (11) for delaying said differential signal such that the common mode noise estimate signal (ECM) corresponds temporally with the delay differential signal; and (vi) means (19) for subtracting the common mode noise estimate signal (ECM) from the delayed differential signal to form a noise-reduced output signal; wherein each of the noise detector means (231, . . . , 23M) comprises selector means (281, . . . , 28M) for selecting a respective one of said selected samples in dependence upon whether or not a measure of plurality of previous samples of the corresponding one of the digital signals (S1, . . . , SM) exceeds a predetermined threshold level (T).