A Bit-Serial Pipelined Architecture for High-Performance DHT Computation in Quantum-Dot Cellular Automata

In this brief, we consider quantum-dot cellular automata (QCA) realization of the discrete Hadamard transform (DHT). An analysis of a full-parallel solution based on efficient multibit addition in QCA is first presented. We show that this leads to large area as well as delay. We then propose a bit-serial pipelined architecture for QCA-based DHT. The proposed architecture is based on a new one-bit adder-subtractor requiring only six majority gates and a feedback latch that requires only one majority gate and limited wiring. The approach leads to a reduction in area-delay-cycle product of 74% and 91% (over a full-parallel solution) for wordlengths of 4 and 8, respectively. Results of simulations in QCADesigner are also presented.