Adder and multiplier design and analysis in quantum-dot cellular automata
Quantum-dot cellular automata (QCA) is an emerging nanotechnology for electronic circuits. Its advantages such as faster speed, smaller size, and lower power consumption are very attractive. The fundamental device, a quantum-dot cell, can be used to make gates, wires, and memories. As such it is the basic building block of nanotechnology circuits. While the physical nature of the nanoscale materials is complicated, the circuit designer can concentrate on the logical and structural design, so the design effort is reduced. Because of its novelty, the current literature shows only simple circuit structures. This research broadens the QCA circuit designs with larger circuits, explores the characteristics of QCA circuit designs, and shows analysis based on those design results. This dissertation proposes three kinds of adder designs in QCA from the conventional adder design approaches. Ripple carry adders, carry lookahead adders, and conditional sum adders are designed for optimization with QCA technology and simulated with several different operand sizes. Using the newly discovered knowledge of the QCA circuit characteristics, new designs for serial adders and multipliers are presented, which are the carry flow adder and the serial multiplier. The carry flow adder design is compared with the previous three adder designs. From the filter design methodology, the carry shift multiplication and the carry delay multiplication algorithms are proposed. The serial multipliers are implemented with both algorithms. The final designs are compared according to the complexity, area, and delay.