Reconfigurable channel filtering and digital down conversion in optimal CSD space for software defined radio

Software defined radio (SDR) is a platform for using the same hardware to support multiple wireless communication standards. The channelizer in the SDR is used to separate the channels from the wideband signal. The features required for using the same hardware to switch between different standards are reconfigurability and low complexity. To achieve this, we use a variable bandwidth filter (VBF) with facility for the reduction and enhancement of the bandwidth, without changing the filter coefficients. This paper proposes an optimal and multiplier-less implementation of a baseband channel filter for supporting the bandwidth requirements of various wireless communication standards. This paper also discusses the concept for using it as a multi-band SDR channelizer for the direct conversion of signals from a wideband input to the baseband signal without using an intermediate stage. Frequency response masking (FRM) filter with continuous coefficients is designed and modified harmony search algorithm is used for finding the optimal canonic signed digit representation for the multiplier-less implementation. This reduces the complexity and power consumption. The VBF with the optimized FRM filter is evaluated for the selectable bandwidths starting from 1.25 to 8 MHz, which covers the bandwidth requirements of a wide range of wireless communication standards.