Adaptive system in a digital data receiver providing compensation for amplitude and phase distortions introduced by a data transmission channels

Claim 1

In a digital data receiver, an adaptive system providing compensation for amplitude and phase distortions introduced by a data transmission channel and comprising an adaptive equalizing circuit receiving a signal vector X k from the data transmission channel output and producing an output signal y k , and a decision circuit receiving this output signal y k and producing an estimation s k-d of each one of the digital data s k-d applied to the data transmission channel input, characterized in that the adaptive equalizing circuit is a non-recursive transversal filter having N adjustable weighting coefficients and the adaptive system comprises for the direct determination of these coefficients: a first circuit for determining, in an estimated matrix A e of the square signal autocorrelation matrix A=E(X k .X k TR ) where E is the expectation operator and X k TR is the transpose of X k , the (N/2+1) first elements (a 0 e , a 1 e , a 2 e , . . . a N/2 e ) of the first row if N is even, or the (N+1)/2 first elements (a 0 e , a 1 e , a 2 e , . . . a.sub.(N-1)/2 e ) of the first row if N is odd, over an interval equal to a predetermined number M of data symbol periods of duration T on the basis of the relation ##EQU17## a second circuit connected to said first circuit for forming a vector U=(r 0 e , r 1 e , r 2 e , . . . r N-2 e , r N-1 e ) in which r i e =a i e for every i not exceeding N/2 if N is even, or not exceeding (N-1)/2 if N is odd, and r i e =a N-i e for every i exceeding said limits, a third circuit connected to said second circuit for forming a vector Λ e =(λ 0 e , λ 1 e , λ 2 e , . . . , λ N-1 e ), whose components are the eigenvalues of a circulant matrix having said vector U as a first row, with the aid of the relation ##EQU18## where U TR is the transpose of U and P is the unitary matrix of the order N defined by P=||P.sub.f,g ||(f,g=0, 1, 2, . . . , N-2, N-1) and ##EQU19## a fourth circuit connected to the data transmission channel output and the decision circuit output for determining an estimation V e of the signal correlation vector V=E(X k s k-d ) in accordance with the relation ##EQU20## a fifth circuit connected to said fourth circuit for multiplying said estimated vector V e by the complex conjugate P cc of said unitary matrix P, a sixth circuit connected to said fifth and third circuits for dividing the vector Q=P cc .V e at the output of said fifth circuit by said vector Λ e at the output of said third circuit on a term-by-term basis so that the resulting vector F=(f 0 , f 1 , f 2 , . . . f N-1 )=Q/Λ e has components f i =q i /λ i e for every i not exceeding N-1, a seventh circuit connected to said sixth circuit for multiplying said vector F by said unitary matrix P, the resulting vector P.F is the estimate of the vector C R constituting an approximation of the vector of the N optimum weighting coefficients of said transversal filter and being applied to said transversal filter for adjusting the weighting coefficients.