O. Andrisano et M. Chiani, THE 1ST NYQUIST CRITERION APPLIED TO COHERENT RECEIVER DESIGN FOR GENERALIZED MSK SIGNALS, IEEE transactions on communications, 42(2-4), 1994, pp. 449-457
A simple procedure for designing the post-detection Alter of an MSK-ty
pe receiver for Continuous Phase Modulation with modulation index h =
0.5 (Generalized MSK signals) is proposed: the criterion descends from
a useful, general representation of this class of signals. The freque
ncy response of the baseband receiver filter is analytically optimized
in closed form whatever the modulation pulse shaping of the transmitt
ed signal, and signal-to-noise ratio at the receiver. The criterion is
pointed out through a significant, exact representation of Generalize
d MSK signals, whatever the modulation pulse-shaping waveform, which i
s assumed to be included in a time range equal to LT, T = symbol time.
The main part of intersymbol interference, as appears from the repres
entation of the CPM signal, is cancelled by applying the Nyquist crite
rion to the most significant function among those describing the signa
l structure. The numerical results obtained show a performance improve
ment with respect to the Averaged Matched Filter (AMF) criterion and a
re very close to the results reported in the literature, deriving from
more complex design criteria. The suitability of the design criterion
is also tested in the presence of interferers, showing a signifiCant
advantage of the proposed filter when considering adjacent channel int
erference.