Group-delay optimized IF filters for narrowband PCS

We consider the design of group-delay optimized IF filters for a specific 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 compare the results to those achieved with the filter originally recommended for implementation in the system. Two alternatives to the original sixth-order Bessel-Butterworth were examined: a fifth order Butterworth with cascaded first-order phase equalizer and a sixth-order equiripple group delay filter. The former showed up to 1 dB gain in BER performance for the forward channel, and the latter showed up to 1 dB gain in the reverse channel.