A DSP-Based Stereo Decoder for Automotive Radio

With the introduction of compact disk players to automotive entertainment systems a new standard of in-car sound reproduction quality has been set. To ensure that the level of performance that CD offers is not compromised it has been suggested that digital signal processing techniques be used to perform the usual audio processing. By performing as much of the AM and FM radio processing as possible using digital signal processing (DSP) it is possible to integrate many entertainment system functions into a single programmable unit. This paper describes a technique for decoding the stereo multiplex signal from the FM detector into the left and right audio channels in a way that is particularly amenable to DSP implementation. A brief description of such an implementation using the Motorola DSP56001 digital signal processor IC and DSP56ADC16 A/D converter IC is included.