Device for carrier phase recovery

A transmitter-receiver chain comprising a differentially encoding transmitter and a differentially decoding receiver, the differentially encoding transmitter comprising a baseband modulator arranged to modulate a complex baseband signal and to output, at point n1 in time, a complex modulated signal x1in(n1) with amplitude g1 and phase q1, x1in(n1)=g1(n1)ejq1(n1), to an input port of a first filter, the first filter in turn having its output coupled to a transmit unit, said first filter being arranged to output, at point n1 in time, a filtered complex output signal x1out(n1) with amplitude g1 and phase m1, x1out(n1)=g1(n1)ejm1(n1), so that the first filter is arranged to affect the phase but not the amplitude of its input signal, the first filter being arranged to have as its transfer function for the phase of its input signal a z-transform F(z)=1+wz−1, the differentially decoding receiver comprising a receive unit whose output is connected to a second filter, the second filter in turn having its output coupled to a detector unit which is connected to a demodulator, said second filter being arranged to receive from the receiver unit at point n2 in time a complex input signal x2in(n2)=g2(n2)ejq2(n2), and to output, at point n2 in time, a filtered complex output signal x2out(n2)=g2(n2)ejm2(n2), so that the second filter is arranged to affect the phase but not the amplitude of its input signal, the second filter being arranged to have as its transfer function for the phase of its input signal an inverse of the z-transform F(z)=1+wz−1, w being a weighting function whose value is determined based on an additive noise autocorrelation, a phase noise autocorrelation and the signal amplitude of x1in.