A software radio architecture for multi-channel digital upconversion and downconversion using generalized polyphase filterbanks with frequency offset correction

Polyphase filterbanks (PFBs) provide a computationally efficient approach to extracting channels of arbitrary bandwidth from a wideband signal. This technique, know as digital downconversion, would find use in software radio applications. Conversely, PFBs can also be used to perform digital upconversion, a process in which a wideband signal is constructed from several narrowband channels. In this paper, we apply the PFB technique to the IS-136 standard (North American Digital TDMA). Since the IS-136 standard requires non-overlapping adjacent channel filter masks, we show in this paper that the Generalized PFB is the optimal architecture given the non-integer sampling rate conversion that is needed to go from IF to baseband. Since frequency offset correction is an important consideration for radio receivers, we also present an augmented GPFB architecture that intrinsically performs frequency offset correction.