System architectures and digital signal processing algorithms for enhancing the output audio quality of stereo FM broadcast receivers

This paper presents two FM receiver architectures and three digital signal processing algorithms for enhancing the output audio quality of FM broadcast receivers. The two receiver architectures differ only in the front-end processing for estimating the carrier-to-noise ratio and noise floors of the stereo audio signals. The shared back-end processing consists of three algorithms to suppress the noise in the audio signal, to detect and cancel noise pulses (static), and to conceal the degrading effects of fast fading, respectively. Together these FM enhancement techniques achieve about 20 to 35 dB improvements in SNR and stereo separation over a wide range of RF signal strength spanning nearly 30 dB. Perceptually, the audio quality improvement is large and obvious when the received FM signal is weak.