A Polyphase comb filter using interlaying multiplexers for high-speed single-bit Sigma-Delta modulators

This paper proposes a new design for a Polyphase implementation of a third-order SINC filter (SINC³) with a decimation factor of 8. In order to make our solution more power efficient in comparison with the classical Polyphase filters, we use the counterclockwise commutator technique and, by applying a multiplexer interlaying strategy, we are able to implement a multiplier-free Polyphase structure. Moreover, by using properly defined control signals, our circuit takes advantage of dispatching input bit stream and navigating bits in the related sub-filters. High-level simulation results in MATLAB shows that our filter allows reaching a dynamic performance comparable to the ideal SINC³ filter and, the corresponding implementation in a Xilinx Spartan3 FPGA demonstrates the feasibility and hardware efficiency of our solution. The proposed new filter architecture can be readily applicable to any Sigma-Delta ADC with a single-bit output stream and it requires a reduced number of adders and registers when compared with state-of-the-art approaches.