Alcatel N.v.

Alcatel Transmission Par Faisceaux Hertziens

Robert Ravoalavoson

Didier Martineau

Guy Allemand

The invention provide a digital method of correcting non-linearity in a transmission chain, in which the effects of amplifier non-linearities are compensated by applying predistortion in baseband prior to modulation, with the signal being processed digitally in real time. The invention also provides apparatus for implementing the method. The invention is particularly applicable to radio beams for conveying digital signals.

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

Servo-controlling position in a modulator having 2.sup.n phase and amplitude states (used for e.g. 16-QAM radio beam transmission) is achieved by monitoring the amplitude of the signal output from the modulator. In a first or inner loop, any constellation centering error in the modulation states is corrected; in a second or middle loop, any quadrature error between the modulated carriers is corrected; and in a third or outer loop, any amplitude difference between the X and Y channels input to the modulator is corrected.

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Courbevoie, France

Robert Ravoalavoson