Alcatel Italia S.p.a.

Massimo Gelichi

Franco Guglielmi

Maurizio Bolla

Nino Leuratti

The present invention concerns a system for estimating the carrier frequency of a PSK numeric signal, in which symbols are transmitted at frequency fs. The invention is characterized by the use of an estimate, at each symbol interval, of the angular difference between two successive data. Such estimate, suitably processed, provides the control signal for a circuit that compensates the frequency error between the carrier of the received signal and the local oscillator. In a not limiting embodiment, the invention can be implemented through digital circuitry.

System and circuit for estimating the carrier frequency of a PSK numeric

The present invention relates to a QAM signal demodulation system able to recover phase and frequency of the carrier and convert the signal to baseband, and to perform these functions when frequency errors are remarkable with respect to the symbol frequency (low capacity links); to reconstruct the synchronism of symbol in order to correctly sampling the analog signal to be processed; to complete the shaping of the signal through a digital filter and to equalize the baseband converted signal (in order to compensate the selective fading effects due to propagation and the linear distortions due to imperfections in the realization of the apparatus). Therefore the system comprises several subsystems devoted to performing the various functions and, in particular, at least a carrier frequency and phase recovery subsystem, a subsystem for reconstructing the synchronism frequency capable of driving the signal sampling circuit, and a subsystem of filters. The present invention is directed to the choice of the particular subsystems used as well as their implementation and interconnections.

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San Piero A Grado, Italy

Massimo Gelichi