Method for the correction of phase and amplitude errors in COFDM signals.

In the transmission of digital television data according to the COFDM method, the single carrier frequencies used in this case are phase-modulated. For demodulation of the single carrier frequencies in the receiver, a phase reference signal is transmitted in each transmission frame. The phase difference between the phase reference signal and the individual carrier frequencies received in the same transmission frame contains the transmitted information. The problem is the distortion of the single carrier frequencies, in phase and amplitude, which can be caused by assemblies of transmitter and receiver and through the transmission path. The new method allows to correct these distortions, as far as a mathematical model can be given. To correct the phase of the received single carrier frequencies, a mathematical model is calculated for the phase distortions of the phase reference signals as a function of time. The data signals received between two phase reference signals are corrected on the basis of this mathematical model of the time course of the reference phase. In order to additionally eliminate random phase distortions, a maximum likelihood decision is made with the corrected phase value. The correction of the amplitude of the single carrier frequencies is based on an amplitude reference value, which is determined from the amplitudes of previously received single carrier frequencies. The new method allows the correction of phase-modulated single carrier frequencies and can be used in transmissions according to the COFDM method.