METHOD AND DEVICE FOR DIGITALLY DEMODULATING A FREQUENCY MODULATED SIGNAL

摘要

The present invention represents a new approach in the field of digital ly demodulating a frequency modulated signal as it is used for example for fm-audio broadcasting. The inventive algorithm improves the signal to noise ratio of the demodulated signal for carrier to noise ratios below the fm-threshold . According to the present invention the spikes in the demodulated signal whi ch are typical to occur for carrier to noise ratios below the fm-threshold are detected and eliminated. The detection is done by interpolation and other criteria of the unwrapped phase .PHI.u of the frequency modulated signal. The unwrapp ed phase .PHI.u is calculated as the absolute phase which is not limited to the range [ -.eta., ..., .eta.].