Considerations on Interference for Hybrid Mode Digital Radio Broadcast Standards over AM Frequencies

The development of digital radio broadcasting standards turns indispensable the analysis of their technical characteristics to define the advantages of every system on itself and in comparison with others. One important characteristic consists in the usage, over a period of time called transition period, of the current equipment and keeper frequency bands of the analogue transmission systems to carry both analogue and digital signals (a transmission mode denominated "hybrid mode"). When both signals are sent over minimal frequency bands (10 kHz), digital signals could generate interference on transmission, a situation that has passed unnoticed in the implementation studies previously realized. In this work, we analyze this issue for DRM and AM IBOC digital standards. Based on data obtained by the simulation of propagation of digital signals, are exposed the measurements of interference found for three commercial stations operating in Mexico City.