Data demodulator for a direct frequency modulated signal.

摘要

A data demodulator for a direct frequency modulated signals such as an FSK signal used in quasi-synchronous signalling systems for example paging systems. The data demodulator comprises means (12 to 28) providing a positive frequency filter and a negative frequency filter. The filters each have a pass band that includes the modulus of the deviation frequency ( DELTA f) and providing outputs (A min , B min , C and D) with two different phases for the positive frequency and two different phases for the negative frequency. The demodulator further includes means (32 to 52) for comparing the signal strength in the outputs of the positive and negative frequency filters to provide a data output.