Patent US 4,484,337

A circuit for regenerating a carrier wave on the basis of a modulated wave. It comprises a voltage-controlled oscillator, two demodulators supplying two demodulated signals, respectively X for the first and Y for the second; a first decision and regeneration circuit with an input connected to the first demodulator and an output supplying a difference signal (X-X), in which X is a signal regenerated from signal X; a first zero threshold comparator connected to the first demodulator and supplying a signal determining the sign of X, i.e., sgn X; a second zero threshold comparator connected to the decision and regeneration circuit and determining the sign of the difference X-X, i.e. sgn (X-X); a second decision and regeneration circuit connected to the second demodulator and supplying a difference signal (Y-Y), in which Y is a signal regenerated from signal Y; a third zero threshold comparator connected to the second demodulator and supplying a signal determining the sign of Y, i.e. sgn Y; a fourth zero threshold comparator connected to the second decision and regeneration circuit and determining the sign of the difference Y-Y, i.e. sgn (Y-Y); a first logic EXCLUSIVE-OR gate supplying a signal sgn (X-X) sgn (Y); a second EXCLUSIVE-OR gate supplying a signal -sgn (Y-Y) sgn (X); an adder supplying a signal sgn (X-X) sgn (Y) -sgn (Y-Y) sgn (X) applied to the voltage controlled oscillator.