Design of 4-bit Barrel Shifter in Quantum Dot Cellular Automata

Abstract

This thesis proposes the design of a 4-bit barrel shifter using Quantum DotCellular Automata (QCA) technology. With decreasing feature size, CMOS technologyfaces various challenges like leakage current, drain induced barrier lowering,power dissipation etc. Researchers have proposed alternative technologieswhich helps to alleviate the problems associated with CMOS. Quantum DotCellular Automata (QCA) is one such promising technology which can replacetransistor based CMOS Technology. The thesis begins with an introduction toQCA technology and its basic elements which are QCA inverter and QCA majoritygate. Basic logic gates designs are implemented using majority gates andinverter. It then presents two major concepts of QCA namely QCA Clocking andQCA Crossover. QCA Clocking is a technique used to synchronize QCA cells,while QCA Crossover is used to transmit signals through crossing wires. Thecrux of the thesis is the design of a 4-bit barrel shifter using QCA technology.Barrel shifter is a crucial component in digital signal processing and graphics applications.The left and right shift operations of barrel shifter are useful in findingGreatest Common Divisor(GCD) using Steins� Algorithm. The proposed designis a right shifter that is capable of shifting the input by one, two, or three positionsto the right, depending on the control signals.The proposed design utilizes optimized2:1 multiplexers which provide the advantage of minimum area and powerconsumption. The proposed design is simulated using QCADesignerE software,and the obtained results are compared with the performance of existing shiftersin QCA.The simulation results demonstrate that the proposed design provides asignificant improvement in terms of area with a cell count of 381 and a delay of6 clock phases. Further, a comparison of the proposed QCA based barrel shifterwith conventional CMOS-based shifter is also presented.