Terminal for the transmission of data over a bidirectional analog channel with echo cancellation controlled by the reception rate

DETAILED DESCRIPTION The present invention overcomes the above drawbacks by providing a terminal which has no interpolation filter, does not required control of time sharing between the computing units, and makes it possible to use an echo canceller whose adaptation is controlled by the signal which controls the adaptation of the equalizing filter, which confers very good performances thereon.
For this, the present invention provides a terminal of the above defined type, in which: Said means for estimating the distant data include first means for sampling said received signal, means for processing the samples of said received signal, which are adapted for restoring estimated distant symbols and a timing signal whose frequency is equal to said modulation rate, and a means, synchronized by said timing signal, for controlling the sampling frequency of said first sampling means, and said echo canceller includes second sampling means for sampling said emitted signal, connected to said control means and controlled at the same frequency as said first sampling means, first filetring means for filtering the samples of said emitted signal and delivering samples of the estimated echo signal, and first subtraction means disposed after said first sampling means for subtracting said samples of the estimated echo signal from said samples of said received signal.
In the terminal of the invention, because the echo canceller operates at the timing defined by the clock signal synchronized with the reception baud frequency, it is pointless to place an interpolation filter downstream of the point where the samples of the estimated echo signals are subtracted from the samples of the received signal.
Because the echo canceller and the receiver operate at synchronized rates, it is easy to control the time sharing of the computing units.
Since the means for generating the emitted signal do not require a high computing power, it is possible, in one practical embodiment, to design a fairly simple and compact emitter, the echo canceller being included in the receiver, since these two systems operate at synchronous rates