Abstract: A QPSK modulator has a signal generator which generates four carrier outputs having respective phases of 0.degree., 90.degree., 180.degree., and 270.degree.. A four input phase selector is connected to the four outputs of the generator, has four modulator signal inputs, and has four phase shifted carrier outputs connected to an OR gate which provides the QPSK output signal. The generator comprises a source of signals in opposite phase coupled to two frequency dividers, each divider having two outputs of opposite phase. It also has two pairs of flip-flops whose outputs form the four outputs of the generator. The signal inputs of one pair of flip-flops are connected to the outputs of the first divider. The signal inputs of the other pair of flip-flops are connected to the outputs of the second divider. Variable capacitors are provided between the clock inputs of the flip-flops and ground. A 2.sup.

Abstract: 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.