Exciter architecture for digital sound and video broadcasting transmitters

Modem radio-communications have begun the transition process from analog to digital radio-communications and broadcasting. During this transition process, main changes are required in exciter units of transmitters. The architecture of transmitters themselves is the same for both digital and analog broadcasting, but the exciters used for digital broadcasting have to create analog RF exciting signals for the transmitters from the digital data stream. The most common modulation procedure used in digital broadcasting systems is OFDM with QPSK or some kind of QAM keying of sub carriers. Apart from RF signal generation, the exciters are often responsible for control of the whole system, because control data is often included in the digital stream distributed from the broadcast center to the transmitters.