Quadrature demodulation of a data sequence following a particular signal sequence with a local reference carrier signal having a frequency different from a received carrier signal

摘要

An angular modulated signal is quadrature demodulated (37) into first and second signal vectors by a local carrier signal (36) having a frequency difference from a received carrier signal which is angular modulated by a modulating signal comprising symbols representative of binary one and zero at a symbol interval. In the modulating signal, a particular symbol sequence comprises the symbols in a predetermined manner and results in the first signal vector. A data symbol sequence comprises the symbols to represent data and results in the second signal vector. The first signal vector has inphase and quadrature phase amplitudes which are converted (41) to phase values substantially at the symbol interval. An individual error is provided by comparing (44) a phase variation between two phase values (42-43) with a reference variation (45) determined by the predetermined manner. Such individual errors are averaged (46) into a phase error (47) which is used in correcting (39) the second signal vector. It is possible to compute the phase error by calculating the phase variation using a reference variation determined by the predetermined manner and the received carrier signal.