| 摘要 |
A noise suppression circuit for a communications channel (12) comprises a noise reference extraction device (14), for example a hybrid transformer or circui t, for extracting from an input signal (S) a reference signal (N CM) corresponding to a noise component in the input signal and supplying the noise reference signal to a noise estimation unit (16) which derives therefrom a noise estimate (Y j) which is subtracted from the input signal to produce a noise-suppressed output signal (D OUT). T he noise suppression circuit comprises a first analog-to-digital converter (24) for digitizing the input signal at a first sampling rate (Fs) and a second analog-to-digital converter for sampling the noise reference signal (N CM) at a second, lower sampling rate (FS/M), the ratio (M) between the two sampling rates being an integer. A decimator (40) decimates the input signal to produce a decimated signal (D j+N j). An adaptive filter (34) produces a noise estimate signal (Y'j) that is subtracted from the decimated signal t o produce an error signal (.epsilon.j) which is used by adaptive filter (34) to adjust it s coefficients. An interpolator (36) interpolates the interim noise estimate signal (Y'j) by th e same integer (M) to provide a noise estimate signal (Y j) which is subtracted from a digitized and delayed version of the input signal to produce the noise-suppressed output signal (D OUT).
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