Equiripple group delay digital filter sets for use in FSK modems

Frequency shift keyed data signals may be demodulated by splitting the message signals into two spectral bands and comparing the received signal energy in the two bands. The band splitting filters in this type of demodulator are required to have both constant in-band group delay and matched group delay between the two bands. The problem considered in this paper is that of designing recursive digital filters which approximate this group delay requirement in an equiripple sense, and which can perform the required band splitting function.