Schutzintervallerzeugung in einer Übertragung mit DMT-Modulation

The circuit takes a sample from the header and re-copies this at the end of the signal. The circuit generates a cyclical symbol prefix composed of a series of samples in the time domain. The prefix is the reproduction of the last symbol samples in the symbol header. The symbol is obtained by inverse Fourier transformation of the complex coefficients corresponding to the respective frequencies. The circuit includes a device (22) for dephasing each complex coefficient of a value proportional to its frequency. A memory (24) is provided for storing the samples of the start of the symbol, and a further circuit (16) is provided for re-copying the memorised samples at the end of the symbol.