US 4,785,445 AGranted

Method of manufacturing BaPb.sub.1-x Bi.sub.x O.sub.3 single crystal

AssigneeTelecommunications Radioelectriques et Telephoniques T.R.T.

InventorLoic B. Y. Guidoux

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Abstract

Echo canceler associated with a modem utilizing amplitude and phase modulation of a carrier, the echo canceler comprising adaptive filters (16-1) to (16-p) producing signals which are combined in an adder (15) for forming a synthetic echo signal .epsilon. (n). The coefficients of these filters are adjusted to minimize the mean square value of the residual echo signal e(n)=.epsilon.(n)-.epsilon.(n), where .epsilon. (n) is the echo received. The echo canceler comprises a code conversion circuit (17) which receives a signal D(n) characterizing in each modulation interval the amplitude and phase state of the carrier to be transmitted and which produces distinct configurations of several veral numbers of values +1, -1 or 0, said distinct configurations corresponding to the distinct possible states of the carrier to be transmitted such that elementary signals D.sub.1 (n) to D.sub.p (n) are formed which are mutually independent in the mean and which are applied to the filters (16-1) to (16-p). These filters can then be realized in a simple way.

Claims12

Dependent claims

An echo canceller associated with a data transmission modem, the modem utilizing amplitude and phase modulation, the modem including a transmit path and a receive path, such that an undesired echo signal appears in the receive path resulting from a carrier signal in the transmit path, the carrier signal having a phase and amplitude state at each modulation interval, the echo canceller comprising:

(a) first input means coupled to the transmit path for receiving a digital representation of the carrier signal, the representation indicating for each modulation interval the phase and amplitude state of the carrier signal;
(b) code conversion means coupled to receive the representation and having a plurality of parallel outputs, each of the parallel outputs providing one of the values +1, -1, and 0, so that the parallel outputs together provide distinct configurations D.sub.i (n) corresponding to the phase and amplitude states of the carrier signal, said distinct configurations satisfying the equation:
E[D.sub.i (n).multidot.D.sub.i,(n)]=0
where:
the operator E represents mathematical expectation;
n is an integer representing an instant of time;
i and i' represent respective parallel outputs of the code conversion means and are integers between 1 and a number of the parallel outputs;
i.noteq.i';
and D.sub.i (n) and D.sub.i,(n), are the values provided at the respective parallel outputs;
(c) output means, coupled to the receive path, for providing an analog synthetic echo signal;
(d) means, disposed within the receive path, for subtractively combining the analog synthetic echo signal and the undesired echo signal to produce a residual echo signal therefrom;
(e) second input means coupled to the receive path, for supplying a digital representation of the residual echo signal;
and
(f) a plurality of adaptive filters, coupled to receive the distinct configurations from respective ones of the parallel outputs of the code conversion means and to receive the digital representation of the residual echo signal from the second input means, having respective outputs coupled with the output means of the echo canceller, and having coefficients which are adjusted in an iterative manner in order to minimize the mean square value of the residual echo signal.

11 more elements

(a) first input means coupled to the transmit path for receiving a digital representation of the carrier signal, the representation indicating for each modulation interval the phase and amplitude state of the carrier signal;
(b) code conversion means coupled to receive the representation and having a plurality of parallel outputs, each of the parallel outputs providing one of the values +1, -1, and 0, so that the parallel outputs together provide distinct configurations D.sub.i (n) corresponding to the phase and amplitude states of the carrier signal, said distinct configurations satisfying the equation:
E[D.sub.i (n-q).multidot.D.sub.i,(n-q')]=0
where:
the operator E represents mathematical expectation;
n is an integer representing an instant of time;
i and i' represent respective parallel outputs of the code conversion means and are integers between 1 and a number of the parallel outputs;
i.noteq.i';
q and q' are integers between 1 and the number of the parallel outputs;
and D.sub.i (n) and D.sub.i '(n) are the values provided at the respective parallel outputs;
(c) output means, coupled to the receive path, for providing an analog synthetic echo signal;
(d) means, disposed within the receive path for subtractively combining the analog synthetic echo signal and the undesired echo signal to produce a residual echo signal therefrom;
(e) second input means, coupled to the receive path for supplying a digital representation of the residual echo signal;
and
(f) a plurality of adaptive filters, coupled to receive the distinct configurations from respective ones of the parallel outputs of the code conversion means and to receive the digital representation of the residual echo signal from the second input means, having respective outputs coupled with the output means of the echo canceller, and having coefficients which are adjusted in an iterative manner in order to minimize the mean square value of the residual echo signal.

12 more elements

Dependencies are inferred from the claim text.