Peak-to-Average Power Ratio Reduction in an FDM Broadcast System

Digital predistortion is a technique used to reduce the signal dynamic range in a multichannel system in order to improve power amplifier (PA) efficiency. These techniques have been developed for orthogonal frequency-division multi-plexing (OFDM) systems, but are not directly applicable to general frequency-division multiplexing (FDM) systems such as those used in broadcast. A modification to the tone injection approach allows constellation translations to be directly applied at the digital intermediate frequency (IF) domain and provides redundancy in lowering peak-to-average ratio (PAR). Simulation of a 24-channel 256-QAM FDM cable television transmission system shows a 3.3 dB PAR reduction at 10^-6 clipping probability.