Abstract: 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 “channel of interest”, 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 (401 to 40L), each stage comprising filter means (42) and decimation means (43), 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.

Abstract: A method of simultaneous phase synchronization and decoding that makes use of the maximum likelihood criterion is provided. The method is applied to signal packets received at a receiver, wherein the signals have been subjected to convolution encoding at the transmitter. The method consists of calculating branch metrics taking account firstly of firm decisions calculated on the received symbols and secondly of a magnitude that takes account of the phase error between the carrier of the signal and the local oscillator signal used at the receiver, the magnitude weighting the decision variables constituted by the complex digital components of the received symbols. This magnitude is equal to &Sgr;*k for each of the paths studied where: &Sgr;k=&Sgr;Nn=0rk−n·d*k−n.

Abstract: 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.