Northern Telecom Limited

J M Simard

William T Ross

A digital FSK demodulator used in e.g. a telephone loop produces unequal amplitudes in detected mark and space tones. The inequality or offset must be cancelled so that a proper timing signal can be recovered from the FSK signal. The demodulator includes a digital compensation circuit for offset cancellation in which peak amplitudes of digital 0 and digital 1 signals are continuously monitored. The peak amplitudes are then averaged to obtain an offset estimation which is subtracted from the output of the demodulator for offset compensation.

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Hull, Canada

J M Simard