Digital method of correcting non-linearity in a transmission chain, and apparatus implementing the method

Claim 1

A digital method of correcting non-linearity in a transmission chain, in which the effects of amplifier non-linearities are compensated by means of baseband predistortion prior to modulation, the digital processing of the signal taking place in real time, wherein the digital processing is applied to Cartesian coordinates defining two new axes attached to an arbitrary vector to be corrected, the first new axis being collinear therewith, and the second being in quadrature therewith; wherein relative to these two new axes, two corrections f 1 (Ri) and f 2 (Ri) are to be performed, namely: f.sub.1 (Ri)=R' cos θ' and f.sub.2 (Ri)=R' sin θ' with: Ri=modulus of the vector to be corrected R'=a' 0 +a' 1 Ri+a' 2 Ri 2 +a' 3 Ri 3 . . . +a' n Ri n θ'=b' 0 +b' 1 Ri+b' 2 Ri 2 +b' 3 Ri 3 . . . +b' n Ri n with a' 0 -a' n and b' 0 -b' n being fixed coefficients and n being an integer; wherein, transferred to fixed axes OX and OY defined by the modulation, these corrections become: Xc=X.sub.i [f.sub.1 (Ri)/Rc]+Y.sub.1 [f.sub.2 (Ri)/Rc] Yc=Y.sub.1 [f.sub.1 (Ri)/Rc]-X.sub.1 [f.sub.2 (Ri)/Rc]; Rc corresponding to an amplitude: Xi and Yi being the Cartesian coordinates of the vector to be corrected along the axis OX and OY.