Xiaokuo Yang

Reliability and Performance Evaluation of QCA Devices With Rotation Cell Defect

As a novel nanotechnology, quantum-dot cellular automata (QCA) can achieve dense packages due to the extremely small size of quantum dots. However, fabrication defects and fault rates in the nanotechnology are expected to be quite high. In this paper, the behaviors of basic QCA devices in the presence of cell rotation are thoroughly analyzed in order to study their rotation defect tolerances and determine the ranges of allowable rotation angles. Rotation effect of QCA cell is modeled by using modified coherence vector formalism and rotation angle. The performances of five basic QCA devices with rotation cell defect are simulated under various cell sizes. The results show that different QCA devices have different rotation angle tolerances. The inverter is the weakest structure while the straight wire is the most reliable structure if measured by the smallest angle that impacts success rate, and the bigger cell size has a negative effect on allowable rotation angle range. More analysis results show that the diagonal cell and the cell close to the output perform the worst rotation tolerance on the inverter and the interconnect, respectively. Furthermore, the power gain of rotation defect device is discussed and the finding is provided that moderate rotation error can be restored at the location that is three cells away from the defect.

Design and Simulation of Turbo Encoder in Quantum-Dot Cellular Automata

Quantum-dot cellular automata (QCA) is a potential nanoelectronic technology for information processing. To be considered as a suitable CMOS candidate, QCA must be able to implement complex real-time applications of bit-serial information processing, which lacks of enough investigation. Turbo encoding is one of such applications, which refers to three representative issues of bit-serial circuits: convolution computation, feedback, and serial data permutation. The inherent shift-register nature of QCA offers an advantage to performing convolution computation but poses handicaps to resolve the latter two issues. How to manage the ambivalent effects of shift-register nature is investigated in this paper, which determines the efficient design of Turbo encoder. A strobe scheme based on main-branch wire crossing is proposed to efficiently make data choosing that is the communally key procedure of the implementation of feedback and serial data permutation. On this basis, a method of implementing recursive convolutional encoder with multifeedback is proposed. A two-stage pipelining interleaver is presented. Finally, a Turbo encoder is implemented using QCA based on these approaches and simulation demonstrates that it performs well.

A study on hyperchaotic system implemented by SETMOS

In this paper, we proposed a hardware implementation method for generating a sandwich hyperchaotic attractor. Based on the negative differential conductance (NDR) characteristic of hybrid single-electron transistor and complimentary metal-oxide-semiconductor (SETMOS) architecture, Saito hysteresis chaos generator (SHCG) was constructed using a cellular neural network (CNN). Complex dynamical behaviors of the hyperchaotic system were investigated by means of bifurcation diagram, Lyapunov exponent spectrum, Poincare mapping and power spectrum. Numerical simulations verify the theoretical analysis and design method and show that the implemented hyperchaotic circuit works very well.

Voltage Tunability of Magnetic Vortex Gyrotropic Mode Frequency in an Elliptical Magnetostrictive Nanodisk

Micromagnetic simulations predict vortex gyrotropic frequency variations induced by voltage-generated uniaxial stress in a soft, elliptical, magnetostrictive nanodisk. The gyrotropic frequency decreases when the direction of uniaxial stress changes from the major axis of the nanodisk to the minor axis, whereas a more notable downshift of the gyrotropic frequency occurs when the magnitude of the stress increases. The mechanism is analyzed in terms of the stiffness coefficients, which are calculated based on the vortex dynamic energy profile. This voltage tunability of gyrotropic frequency paves the way for the realization of vortex oscillators and frequency-controlled vortex computer memory with ultralow power consumption.

Reliability analysis of magnetic logic interconnect wire subjected to magnet edge imperfections

Nanomagnet logic (NML) devices have been proposed as one of the best candidates for the next generation of integrated circuits thanks to its substantial advantages of nonvolatility, radiation hardening and potentially low power. In this article, errors of nanomagnetic interconnect wire subjected to magnet edge imperfections have been evaluated for the purpose of reliable logic propagation. The missing corner defects of nanomagnet in the wire are modeled with a triangle, and the interconnect fabricated with various magnetic materials is thoroughly investigated by micromagnetic simulations under different corner defect amplitudes and device spacings. The results show that as the defect amplitude increases, the success rate of logic propagation in the interconnect decreases. More results show that from the interconnect wire fabricated with materials, iron demonstrates the best defect tolerance ability among three representative and frequently used NML materials, also logic transmission errors can be mitigated by adjusting spacing between nanomagnets. These findings can provide key technical guides for designing reliable interconnects.

Error correcting circuit design with carbon nanotube field effect transistors

In this work, a parallel error correcting circuit based on (7, 4) Hamming code is designed and implemented with carbon nanotube field effect transistors, and its function is validated by simulation in HSpice with the Stanford model. A grouping method which is able to correct multiple bit errors in 16-bit and 32-bit application is proposed, and its error correction capability is analyzed. Performance of circuits implemented with CNTFETs and traditional MOSFETs respectively is also compared, and the former shows a 34.4% decrement of layout area and a 56.9% decrement of power consumption.

Control of magnetic vortex polarity by the phase difference between voltage signals

Using micromagnetic simulations, we investigate the voltage control of magnetic vortex polarity based on a designed multiferroic heterostructure that contains two separate piezoelectric films beneath a magnetostrictive nanodisk. The results show that controllable switching of vortex polarity can be achieved by proper modulation of the phase difference between two sinusoidal voltage pulses V1 and V2, which are applied to the two separate piezoelectric films, respectively. The frequencies of V1 and V2 are set at the gyrotropic eigenfrequency fG of the nanodisk, and the vortex polarity switching is completed via the nucleation-annihilation process of the vortex-antivortex pair. Our findings provide an additional effective means for ultralow power switching of the magnetic vortex, which lays the foundation for voltage-controlled vortex random access memory.

Spin-orbit torque induced magnetic vortex polarity reversal utilizing spin-Hall effect

We propose an effective magnetic vortex polarity reversal scheme that makes use of spin-orbit torque introduced by spin-Hall effect in heavy-metal/ferromagnet multilayers structure, which can result in subnanosecond polarity reversal without endangering the structural stability. Micromagnetic simulations are performed to investigate the spin-Hall effect driven dynamics evolution of magnetic vortex. The mechanism of magnetic vortex polarity reversal is uncovered by a quantitative analysis of exchange energy density, magnetostatic energy density, and their total energy density. The simulation results indicate that the magnetic vortex polarity is reversed through the nucleation-annihilation process of topological vortex-antivortex pair. This scheme is an attractive option for ultra-fast magnetic vortex polarity reversal, which can be used as the guidelines for the choice of polarity reversal scheme in vortex-based random access memory.We propose an effective magnetic vortex polarity reversal scheme that makes use of spin-orbit torque introduced by spin-Hall effect in heavy-metal/ferromagnet multilayers structure, which can result in subnanosecond polarity reversal without endangering the structural stability. Micromagnetic simulations are performed to investigate the spin-Hall effect driven dynamics evolution of magnetic vortex. The mechanism of magnetic vortex polarity reversal is uncovered by a quantitative analysis of exchange energy density, magnetostatic energy density, and their total energy density. The simulation results indicate that the magnetic vortex polarity is reversed through the nucleation-annihilation process of topological vortex-antivortex pair. This scheme is an attractive option for ultra-fast magnetic vortex polarity reversal, which can be used as the guidelines for the choice of polarity reversal scheme in vortex-based random access memory.

Analysis and Synchronization of a Novel Memristor Hyper-Chaotic System

In this work, a new hyper-chaotic system based on memristor is proposed and the anti-synchronization is demonstrated. Through the analysis of the system behaviors, including the stability of equilibrium set, Lyapunov exponents and phase portraits, it demonstrates the proposed system is a new hyper-chaotic system with the features of infinite equilibrium points and complex dynamic characteristics. Besides the anti-synchronization of the memristor hyper-chaotic system is realized. It is proven that the dynamics of the anti-synchronization error is globally and asymptotically stable based on the Lyapunov stability theory. Numerical simulations are given in the end. It provides the theoretical foundation for the aspects of security communication and image encryption.

Tracking control and synchronization of memristor hyper-chaotic system

In this work, a new hyper-chaotic system based on memristor is proposed and the tracking control and synchronization is achieved. The dynamic characteristics of memristor hyper-chaotic system are analyzed theoretically. Then, the synchronization controllers are designed to realize the chaotic synchronization with the different structure and the tracking synchronization with the given signal. Besides, the effectiveness of synchronization controllers are verified by the Lyapunov principle. The simulated results demonstrated that the memristor hyper-chaotic system has good performance in the tracking control and synchronization. It provides new theoretical guidance for the application of the nano-electronic chaotic system in secure communication and image encryption.