On the design and multiplier-less realization of digital IF for software radio receivers

This paper proposes to reduce the decimation factor of the multistage decimator so that its output can be fed directly to the Farrow structure for sample rate conversion, eliminating the need for another L-band filter for upsampling. Furthermore, it was found out that the programmable FIR filter can be replaced by a half-band filter placed immediately after the Farrow structure, i.e. after sample rate conversion. This significantly reduces the complexity of the proposed software radio receiver because this half-band filter, which consists of fixed filter coefficients, can be implemented efficiently without multiplication using SOPOT coefficients. As the coefficients of the multistage decimators and the subfilters in the Farrow structure are also fixed, they can also be implemented efficiently using the SOPOT coefficients. As a result, apart from the limited number of multipliers required in the Farrow structure, the entire digital IF can be implemented without any multiplication. Design example is given to demonstrate the effectiveness and feasibility of the proposed approach.