GROUP-DELAY OPTIMIZED IF FILTERS FOR NARROW-BAND PCS

We consider the design of group-delay optimized IF filters for a speci fic narrowband personal communications system (NPCS) intended for two- way digital messaging, We assess the bit-error-rate (BER) performance achieved when such filters are implemented in the system, and we compa re the results to those achieved with the filter originally recommende d for implementation in the system, Two alternatives to the original s ixth-order Bessel-Butterworth were examined: a fifth-order Butterworth with cascaded first-order phase equalizer and a sixth-order equirippl e group delay filter. The former showed up to 4 dB gain in BER perform ance for the forward channel, and the latter showed up to 1 dB gain in the reverse channel.