Deutsche Thomson-brandt Gmbh

Dominique Madeleine

Otto Klank

Various methods for terrestrial transmission of digital broadcast signals as DVB, HDTV-T and DAB signals are known. One of these methods is the OFDM method, where the transmitted signal includes a multiplicity of modulated carriers. These carriers are separated in the receiver by means of a Fast Fourier Transformation (FFT). Before being transposed in the frequency domain by the FFT, the analog signal must be sampled. For this purpose a local oscillator controls the timing in front of the FFT. Oscillator imperfections like jitter and frequency offsets can degrade the accuracy of the sampling operation and therefore introduce intercarrier interferences after the FFT. A feedback loop combining the AFC and CPEE process has been designed in order to correct frequency deviations and to reduce jitter of the signal without introducing significant phase noise.

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Hannover, Germany

Dominique Madeleine