Alcatel

Alcatel N.v.

Cyril Bertrand

Philippe R Sehier

Fabien Buda

Emmanuel Lemois

The invention relates to apparatus for filtering, decimating and transposing into baseband, the apparatus being of the entirely digital type, and serving both to extract and transpose into baseband one of the channels, referred to as the &ldquo;channel of interest&rdquo;, of a frequency multiplex of channels, and also to reduce the oversampling factor of said channel of interest, each channel being associated with a distinct carrier. The said apparatus comprising at least two stages in cascade ( to ), each stage comprising filter means ( ) and decimation means ( ), said filter means being placed upstream from said decimation means and enabling a portion of the spectrum to be purged at locations where the decimation means produce aliasing. According to the invention, each stage ( to ) also comprises transposition means ( ) placed upstream from said filter means ( ) and associated with a transposition frequency (f ) previously selected from a set of N possible distinct transposition frequencies so as to transpose the carrier (p ) associated with said channel of interest as close as possible to zero frequency.

Digital device and method for filtering, decimation and transposition into distributed baseband and corresponding digital modulator

Simultaneous decoding and phase synchronization using the criterion of maximum likelihood

A device for receiving a source digital signal transmitted at one or more source symbol frequencies F.sub.s samples a received analog signal transposed into the baseband and delivers an entirely demodulated sample signal. The sampling frequency F.sub.e complies with the generalized sampling condition. A single filter module filtering the sampled signal comprises a digital filter controlled by a filter coefficient vector. The filter coefficients are determined according to a determination criterion allowing for the ratio of the sampling frequency F.sub.e to the source frequency F.sub.s, to interpolate the sampled signal, and for an analysis of the transmission path, in order to limit interference introduced by the path.

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Paris, France

Cyril Bertrand