Method and apparatus for carrier phase tracking

A method for carrier phase tracking in a telecommunications system comprised of a transmitter and a receiver,

• said transmitter performing the steps of:
• adding a pilot signal to a data signal, said data signal comprised of data symbols having a symbol interval with a midpoint, said pilot signal having a frequency equal to the inverse of two times the symbol interval, a first zero crossing point located at a first symbol interval midpoint, and a second zero crossing located at a next symbol interval midpoint,
• modulating the data signal and pilot signal on to a carrier sinusoid, and
• transmitting the modulated carrier into a channel;
• and
• said receiver performing the steps of
• receiving from the channel the modulated carrier transmitted by the transmitter;
• demodulating the received modulated carrier to produce a demodulated signal, having an inphase component and a quadrature component;
• recovering the pilot signal from the demodulated signal produced by the demodulator to produce a phase error estimate, of the pilot tone, calculated using the outputs of a pair of phase locked-loops, which when combined, said outputs produce a phase error estimate;
• sampling the inphase component and the quadrature component of the recovered pilot signal to calculate a phase-error estimate from said samples;
• and
• adjusting the phase of the demodulated signal based on the phase error estimate which is applied to a complex data signal to produce an inphase component estimate and a quadrature component estimate, adjusted for phase error.

A receiver for receiving from a channel a signal comprising a carrier modulated with periodic data symbols and with a pilot signal having a frequency equal to the symbol the inverse of two times the symbol interval, said pilot signal having zero crossings coinciding with the midpoints of the symbol intervals, said receiver comprising:

• (i) a demodulator for demodulating the received modulated carrier to produce a demodulated signal, having an inphase component and a quadrature component;
• (ii) a phase estimator for recovering the pilot tone from the demodulated signal produced by the demodulator to produce a phase error estimate, of the pilot tone, calculated using the outputs of a pair of phase locked-loops, which when combined, said outputs produce a phase error estimate;
• and
• (iii) a phase adjuster for adjusting the phase of the demodulated signal based on the phase error estimate which is applied to a complex data signal to produce an inphase component estimate and a quadrature component estimate, adjusted for phase error.