System and method for demodulating the second audio FM carrier

摘要

The present invention provides a system and method for SAP FM demodulation. The system includes a bandpass filter (120) for isolating the SAP signal, a Hilbert filter (140) to produce a copy of the SAP signal phase shifted by 90 degrees, an FM demodulator (150) for demodulating the SAP signal using the phase shifted SAP signal (Xq) and a delayed SAP signal (Xi), and a lowpass filter (160) to eliminate noise from the FM demodulated SAP signal. The system may also include an automatic gain control for normalizing amplitude of FM demodulator input signals. The digital FM demodulator uses a simplified approximation using non-unity delay for simplified demodulation of frequency modulated signals.