VHF-FM receiver secondary services: RDS to ARI compatibility topics

The authors investigate the mutual compatibility of the usual traffic announcement analog secondary broadcasting ARI (auto radio information) service and simultaneous digital secondary service, known as the radio data system (RDS), evaluating cross-interferences in the standard VHF-FM receiver without coherent detection. On the basis of the analysis and computer simulation the authors conclude that full compatibility of the RDS and ARI systems is possible solely by quadrature procedures both at the transmitting and receiving sides. This implies coherent detection at the receiving side of the circuit for both RDS and ARI signals. The compatibility of the already existing ARI receivers (using an envelope detector) with the RDS system is not ideal. The worst case occurs when some broadcast transmitter broadcasts only RDS signals (without ARI signals). The compatibility of an only-ARI receiver for the reception of RDS+ARI signals depends primarily on the bandpass width of the filter for separation of signals and 57-kHz subcarrier