An efficient channelizer tree for portable software defined radios

Power consumption is one of the most critical issues in the portable software defined radio devices. A software radio receiver has to be able to select and, eventually, down convert a single narrowband channel from a collection of channels that in many practical cases are equally spaced and have equal bandwidth, while providing the minimum power consumption. In this paper we present an efficient solution for selecting a single, 30 kHz wide, channel from a large collection of 1000 channels. The proposed structure is a ten-stage tree with each stage composed of a 4-path polyphase down converter channelizer performing 2-to-1 down sampling of the input signal. The low-pass prototype filter at each stage is chosen to be a half-band filter with the pass-band such that, after partitioning, the overlapping zone of its aliased copies is wide enough to cover exactly one channel. This ensures no channel losses during the processing. The desired channel is recovered at the output of the last stage where a complex heterodyne can be applied (at a very low rate) for shifting it to base-band. The paper provides a detailed workload analysis of the proposed structure along with simulation results that prove its effectiveness.