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 ra-dio applications. Conversely, PFBs can also be used to perform digital upconversion, a process in which a wide-band signal is constructed from several narrowband chan-nels. 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 chan-nel filter masks, we show in this paper that the General-ized 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 impor-tant consideration for radio receivers, we also present an augmented GPFB architecture that intrinsically performs frequency offset correction. 1