Previous work has indicated that highly effective double-filter receivers can be implemented for phase-shift keying (PSK) transmissions over linearly time-selective fading channels provided that the transmitter and receiver filters have root-raised-cosine transfer functions with unity rolloff factor. Revisiting the detection problem within the frame of maximum-likelihood (ML) sequence estimation we prove that this filter design is unique within the class of signaling pulses which are band limited to the symbol rate. It is concluded that some waste of bandwidth is inevitable for achieving ISI-free operation with double-filter receivers.
['Umberto Mengali', 'Giorgio Matteo Vitetta', 'Desmond P. Taylor']
Excess bandwidth is necessary for ISI-free double-filter receivers