Laboratory Simulations of Multipath and the Effect on FM Stereo Signals

Increasing application of high-performance audio media and sound systems requires new levels of performance be achieved in automotive FM reception. Multipath distortion has been identified as a leading industry concern which often limits the quality of FM reception.

Laboratory tests will be used to empirically quantify the effects resulting from a direct wave combining with a single reflected wave at the receiver. The reflected wave will be adjusted in amplitude, phase, and delay time to simulate conditions of mild, moderate, and severe multipath. The effects on the stereo signal will be characterized by the following parameters:

1. 1.
   Total Harmonic distortion (% THD)
2. 2.
   Signal-to-Noise Ratio (dB.)
3. 3.
   Stereo Separation (dB.)

Additionally, the effects of the modulating frequency and carrier deviation will be explored. Data will quantify potential improvements in THD and signal-to-noise ratio by reducing the stereo separation in the receiver. Finally, field data will be shown to illustrate multipath conditions in the “real world.”