Robust QCA Sequential Circuit Design for Fault Tolerant Nano Communication Technologies

Redundancy is the important factor which play a significant in designing the complex circuits. Quantum-dot Cellular Automata (QCA) is a latest upcoming technology to replace the native CMOS which promises the high speed, ultra-low power and extremely dense structures at a nano scale. This is based on a specific physical phenomenon in which the state of the cells changes due to mutual interactions of either electrostatic or magnetic fields. Using purely Columbic interaction between the neighboring cells, the information propagated through QCA cells and various digital logical operations are performed based on the polarization states of the QCA cell. This paper presents the implementation of basic building blocks of sequential circuits of D flip flop in QCA technology with minimum complexity. After the comparative analysis, the D flip flop having lower complexity of 20 cells comprising area 0.02 µm² ideal for designing complex sequential circuit like shift register complexity. The triple modular redundancy method is used to enhance the reliability of the whole circuit. This paper presents the implementation of TMR on proposed shift register structure. The fault-tolerant design, based on the TMR approach, is also well-suited for use in nano communication devices.