Importance

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Abstract

A synchronized broadcast network comprises a main transmitter transmitting an audio source signal to a plurality of receiver/transmitter units remote from each other and from the main transmitter, the receiver/transmitter units broadcasting the audio signal using frequency modulation. In the main transmitter the audio source signal is digitized by sampling it at a predetermined sampling frequency. A digitized signal representing the sampled audio signal is transmitted to the receiver/transmitter units. In each receiver/transmitter unit a reference signal representing the sampling frequency is derived from the received digitized signal and the received digitized signal is passed through a succession of digital processing stages including a stage in which a carrier derived from the reference signal is digitally modulated and a stage in which the result of the digital modulation is digital-to-analog converted. In one of the digital processing stages the received digitized signal is delayed for a predetermined time in order to synchronize the phase of the receiver/transmitter units. All the digital processing stages are synchronized to the reference signal to obtain identical digital modulation of the same carrier for all the receiver/transmitter units. The result of the digital-to-analog conversion stage is transposed to a final frequency derived from the reference signal for broadcasting the analog audio signal using frequency modulation with the same modulation, phase and carrier at all receiver/transmitter units.

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First Claim