Synchronization Bandwidth Research Articles

Enhancement of Synchronization in Nonlinear MEMS Oscillator Based on Electrothermal Adjustment

Abstract Synchronization in Microelectromechanical Systems (MEMS) typically encounters the impact of electrothermal phenomena, often in conjunction with piezoresistive detection or frequency tuning. However, the effects of electrothermal on synchronization have not been previously explored. This paper investigates the electrothermal effects on synchronization bandwidth and frequency stability in a nonlinear MEMS arch oscillator. Experimental results demonstrate a non-monotonic pattern in synchronization bandwidth as electrothermal current increases, corroborated by theoretical models based on quality factors and equivalent nonlinearity. Drawing from theoretical analysis, which suggests that synchronization can be enhanced by adjusting feedback and perturbation strength, we achieved a 5.72-fold enhancement in synchronization bandwidth in our experiments. Furthermore, we observed that increased electrothermal significantly improve frequency stability. We developed a model based on the Allan deviation that incorporates electrothermal temperature to evaluate frequency stability, and this model successfully verified our experimental results. These experimental and theoretical findings highlight the potential of electrothermal effects to enhance synchronization and frequency stability in MEMS devices, paving the way for more robust sensor technology applications.

Synchronization bandwidth enhancement induced by a parametrically excited oscillator

The synchronization phenomenon in nature has been utilized in sensing and timekeeping fields due to its numerous advantages, including amplitude and frequency stabilization, noise reduction, and sensitivity improvement. However, the limited synchronization bandwidth hinders its broader application, and few techniques have been explored to enhance this aspect. In this paper, we conducted theoretical and experimental studies on the unidirectional synchronization characteristics of a resonator with phase lock loop oscillation. A novel enhancement method for the synchronization bandwidth using a parametrically excited MEMS oscillator is proposed, which achieves a remarkably large synchronization bandwidth of 8.85 kHz, covering more than 94% of the hysteresis interval. Importantly, the proposed method exhibits significant potential for high-order synchronization and frequency stabilization compared to the conventional directly excited oscillator. These findings present an effective approach for expanding the synchronization bandwidth, which has promising applications in nonlinear sensing, fully mechanical frequency dividers, and high-precision time references.

Nonlinearity-Induced Asymmetric Synchronization Region in Micromechanical Oscillators.

Synchronization in microstructures is a widely explored domain due to its diverse dynamic traits and promising practical applications. Within synchronization analysis, the synchronization bandwidth serves as a pivotal metric. While current research predominantly focuses on symmetric evaluations of synchronization bandwidth, the investigation into potential asymmetries within nonlinear oscillators remains unexplored, carrying implications for sensor application performance. This paper conducts a comprehensive exploration employing straight and arch beams capable of demonstrating linear, hardening, and softening characteristics to thoroughly scrutinize potential asymmetry within the synchronization region. Through the introduction of weak harmonic forces to induce synchronization within the oscillator, we observe distinct asymmetry within its synchronization range. Additionally, we present a robust theoretical model capable of fully capturing the linear, hardening, and softening traits of resonators synchronized to external perturbation. Further investigation into the effects of feedback strength and phase delay on synchronization region asymmetry, conducted through analytical and experimental approaches, reveals a consistent alignment between theoretical predictions and experimental outcomes. These findings hold promise in providing crucial technical insights to enhance resonator performance and broaden the application landscape of MEMS (Micro-Electro-Mechanical Systems) technology.

Application of nonlinear stiffness mechanism on energy harvesting from vortex-induced vibrations

This study investigates the potential of vortex-induced vibration (VIV) as a renewable energy source, achieved when fluid flow interacts with a bluff body, inducing self-sustained oscillations through vortex shedding in the wake. While VIV research has traditionally focused on understanding its mechanisms and mitigating detrimental effects, interest in VIV energy harvesting has surged as a means to convert marine hydrokinetic (MHK) energy into usable electrical power. The nonlinear effects of two linear oblique springs on VIV energy harvesting are explored using the wake oscillator model, encompassing bistable and Duffing hardening stiffness. The study examines the response and energy harvesting performance while considering the impact of undeformed spring length, structural damping, and initial conditions on VIV energy conversion. Findings show that nonlinear stiffness application in the VIV system can broaden the synchronization bandwidth or reduce the VIV initiation flow speed. Bistable stiffness may broaden the synchronization velocity range, while Duffing hardening stiffness efficiently reduces the VIV initiation speed with small energy harvesting loss. Combining both stiffness types with appropriate control strategies presents a promising approach for achieving a broad synchronization VIV bandwidth and low initiation flow speed. Key parameters, such as the nondimensional parameter defining spring system obliquity and the ratio between undeformed spring length and cylinder diameter, significantly influence VIV response and energy harvesting. Moreover, optimal structural damping is vital to maximize energy harvesting efficiency, and understanding and controlling initial conditions are crucial for optimizing VIV synchronization bandwidth and energy harvesting efficiency for both bistable and Duffing hardening stiffness. This study provides valuable insights into VIV system dynamics and energy conversion potential with nonlinear springs, offering promising avenues for enhancing energy harvesting efficiency and inspiring further applications of nonlinear effects in VIV energy converters.

Quantum synchronization effects induced by strong nonlinearities

A paradigm for quantum synchronization is the quantum analog of the Stuart--Landau oscillator, which corresponds to a van der Pol oscillator in the limit of weak (i.e. vanishingly small) nonlinearity. Due to this limitation, the quantum Stuart--Landau oscillator fails to capture interesting nonlinearity-induced phenomena such as relaxation oscillations. To overcome this deficiency we propose an alternative model which approximates the van der Pol oscillator to finitely large nonlinearities while remaining numerically tractable. This allows us to uncover interesting phenomena in the deep-quantum strongly-nonlinear regime with no classical analog, such as the persistence of amplitude death on resonance. We also report nonlinearity-induced position correlations in reactively coupled quantum oscillators. Such coupled oscillations become more and more correlated with increasing nonlinearity before reaching some maximum. Again, this behavior is absent classically. We also show how strong nonlinearity can enlarge the synchronization bandwidth in both single and coupled oscillators. This effect can be harnessed to induce mutual synchronization between two oscillators initially in amplitude death.

Enhancement of synchronization bandwidth in an arch beam

Synchronization in microstructures has been widely investigated because of its rich dynamics and promising applications. Most investigations are devoted to revealing the basic features or enhancing the application performance in oscillator with hardening nonlinearity. However, few theoretical and experimental studies have been conducted on synchronization with softening nonlinearity, which easily occurs in imperfect manufacturing. In this paper, we built up a phase feedback loop with an arch beam that exhibits softening effect subjected to a synchronization perturbation. Theoretical analysis and experimental verification are applied to explore the effects of the feedback phase delay and nonlinearity on the synchronization bandwidth. The optimal phase delay for best synchronization bandwidth is determined and the significant enhancement of nonlinearity on the synchronization bandwidth is observed. An practical approach of manipulating the nonlinearity strength is proposed by tuning the ratio of the applied ac voltage VAC to DC voltage VDC. The presented foundings provide novel strategies to enhance the synchronization bandwidth in nonlinear oscillator with softening effects.

Software-defined optical intra-data center network and access control Strategy

The continuously emerging cloud services provide an unprecedented traffic growth into the large-scale data centers (DCs) globally. In this paper, we introduce an optical DC network (DCN) architecture to organize the servers into computing clusters. Since a high percentage of the total DCΝ traffic is served within a cluster, we assume two distinct networks: the intra-cluster passive optical network that handles the traffic destined to any server of the same cluster and the inter-cluster one to route the traffic to any other cluster. The servers interconnection within the passive optical intra-cluster network causes low power consumption, while the Top-of-Cluster (ToC) switch requires less ports than a relative Top-of-Rack (ToR) one to interconnect the same number of servers within the intra network, reducing even more the total power consumption. In the data plane, the intra- and the inter-cluster networks use separate wavelengths. In the control plane, the software-defined networking (SDN) paradigm is followed. Especially, in each cluster we adopt a cluster controller to coordinate the medium access control (MAC) in both the intra and inter-cluster networks. Unlike other studies that assume electrical connectivity with the controller, we consider that it is performed in the optical domain to guarantee the effective synchronized operation of the control and data planes. In our work, we focus on the intra-cluster network. We propose a synchronous transmission software-defined bandwidth allocation (SD-BA) MAC protocol to fairly coordinate the collisions-free transmission of different quality of service traffic categories in the intra-cluster network, based on the wavelength and time division multiplexing (W&TDM) techniques. The proposed DCN architecture along with the SD-MAC protocol provides scalability and efficiency. Simulations results show that the proposed SD-BA MAC protocol achieves almost 100% bandwidth utilization, while it reaches at high loads 145% higher throughput, 573% lower delay and 233% less dropped packets as compared to the relative DMAC network architecture (Zheng and Sun, Apr. 2020) [24]. Also, the proposed intra-cluster DCN architecture is compared to some other currently leading relative ones in terms of throughput and power consumption and it is proven to be a performance and energy efficient DCN solution.

Principle of Distributed Bus Protection Based on Directional Impedance Component Comparison

Distributed bus protection is one of the main tasks of smart substation construction to improve the secondary system because it is economical, simple, easy to layout, and easy to realize double. This paper mainly considers that distributed current differential protection is limited by high precision synchronization and high bandwidth and a distributed bus protection based on the directional impedance element comparison principle is proposed. The bus impedance protection constructed by reverse current calculation is proposed, which the impedance protection with positive sequence polarization and the impedance protection with memory polarization are the main components. Further considering the influence of system oscillation, the power frequency variable distance protection is introduced to form a distributed bus protection system, and the setting and time setting principles are given. The principle of the protection system is simple and the action is reliable. The effectiveness of the protection system is verified based on PSCAD simulation software.

Phase-delay induced variation of synchronization bandwidth and frequency stability in a micromechanical oscillator

Phase feedback is commonly utilized to set up a synchronized MEMS oscillator for high performance sensor application. It is a consensus that the synchronization region varies with phase delay with an ‘Anti-U’ mode. In this paper, phase-delay induced variation of synchronization bandwidth and frequency stability in a micromechanical oscillator is investigated analytically and experimentally. The analytical expression for predicting the synchronization bandwidth with phase delay is derived based on the mathematic model. An additional dynamic extreme point of synchronization bandwidth actuated by nonlinearity is observed, which leads to three different types (‘U’, ‘Anti-U’ and ‘M’) of variation pattern of synchronization bandwidth as feedback tuning. The variation of frequency stability along phase delay is also studied. The synchronization bandwidth and the frequency stability have exactly opposite variation pattern with phase delay in linear oscillators while they are totally consistent in nonlinear oscillators. Experimental results validate the analytical observations. Our work provides a precise way for achieving best performance of a synchronized MEMS oscillator in the sensor application.

A Clock Synchronization Algorithm for the Satellite System Based on MF-TDMA

In order to ensure microsecond slot scheduling, all terminals must maintain high precision of time synchronization in MF-TDMA(Multi-Frequency Time Division Multiple Access) satellite communication system. Due to the different frequency of crystal oscillator at the terminal, the absolute value of the clock deviation is constantly increasing, so a clock synchronization algorithm is required to keep the time synchronization of the satellite system. The traditional satellite clock synchronization algorithm minimizes the clock error through periodic synchronization, but it only considers the phase offset, not the crystal frequency offset, the synchronization accuracy is low and waste of bandwidth resources. Based on the traditional satellite clock synchronization, this paper proposes a gradient descent algorithm for the satellite system based on MF-TDMA(GDAS), adding clock frequency offset prediction and compensation mechanism to improve clock synchronization accuracy and bandwidth resource utilization rate. The simulation results of the proposed algorithm has optimized the precision performance of clock synchronization.

Anomalous amplitude-frequency dependence in a micromechanical resonator under synchronization

It is well known that the oscillation frequency relates approximately quadratically with amplitude in a Duffing nonlinear oscillator while the frequency is independent of amplitude in a linear oscillator. In this article, the dynamics of a micromechanical oscillator during synchronization is studied and anomalous amplitude-frequency (a-f) dependence in a micromechanical resonator is observed. We theoretically and experimentally observed that in a linear resonator the amplitude is tuned quadratically with frequency while tuned linearly in a hardening as well as a softening nonlinear resonator, when the self-sustained resonator is synchronized to an external weak perturbation. Further investigation shows that the tunable range of the oscillation amplitude of a certain oscillator directly relies on the synchronization bandwidth, perturbation amplitude and frequency difference. The slope of the dependence can be tuned by phase delay in the feedback loop, while the feedback force dominantly determines the properties of the dependence from nonlinear relation to linear relation. This anomalous a-f effect provides a convenient technique for precise amplitude control.

Programmable synchronization enhanced MEMS resonant accelerometer

Acceleration measurement is of great significance due to its extensive applications in military/industrial fields. In recent years, scientists have been pursuing methods to improve the performance of accelerometers, particularly through seeking new sensing mechanisms. Herein, we present a synchronized oscillator-based enhancement approach to realize a fivefold resolution improvement of a microelectromechanical resonant accelerometer. Through the unidirectional electrical coupling method, we achieved synchronization of the sensing oscillator of the microelectromechanical resonant accelerometer and an external reading oscillator, which remarkably enhanced the stability of the oscillation system to 19.4 ppb and the resolution of the accelerometer to 1.91 μg. In addition, the narrow synchronization bandwidth of conventional synchronized oscillators was discussed, and hence, we propose a novel frequency automatic tracking system to expand the synchronization bandwidth from 113 to 1246 Hz, which covers the full acceleration measurement range of ±1 g. For the first time, we utilized a unidirectional electrical synchronization mechanism to improve the resolution of resonant sensors. Our comprehensive scheme provides a general and powerful solution for performance enhancement of any microelectromechanical system (MEMS) resonant sensor, thereby enabling a wide spectrum of applications.

Synchronization extension using a bistable galloping oscillator for enhanced power generation from concurrent wind and base vibration

This Letter proposes a compact bistable galloping oscillator for achieving enhanced power generation from concurrent wind and base vibration. The harvester consists of a D-shaped bluff body attached to a piezoelectric cantilever, with magnetic interaction introduced between the bluff body and a fixed windward prism. Both theoretical analysis and experiment demonstrate the remarkably broadened synchronization bandwidth for concurrent energy harvesting. In the experiment, the voltage steadily increases from 26.6 V at 8.5 Hz to 40.7 V at 12 Hz, achieving a 10 times wider bandwidth than the linear galloping harvester.

RedSync: Reducing synchronization bandwidth for distributed deep learning training system

Data parallelism has become a dominant method to scale Deep Neural Network (DNN) training across multiple nodes. Since the bandwidth requirement of synchronizing the gradients of the local model can be a bottleneck for large-scale distributed training, compressing communication traffic has gained widespread attention recently. Among several recent proposed compression algorithms, Residual Gradient Compression (RGC) is one of the most successful approaches—it can significantly compress the transmitting message size (0.1% of the gradient size) of each node and still achieve correct accuracy and the same convergence speed. However, the literature on compressing deep networks focuses almost exclusively on achieving good theoretical compression rate, while the efficiency of RGC in real implementation has been less investigated. In this paper, we develop an RGC method that is able to reduce the end-to-end training time on real-world multi-GPU systems. Our proposed RGC system design called RedSync, introduces a set of optimizations to reduce communication bandwidth while introducing limited overhead. We examine the performance of RedSync on two different multiple GPU platforms, including 128 GPUs of a supercomputer and an 8-GPU server. Our test cases include image classification on Cifar10 and ImageNet, and language modeling tasks on Penn Treebank and Wiki2 datasets. For DNNs featured with high communication to computation ratio, which has long been considered with poor scalability, RedSync shows significant performance improvement.

Impedance Differential Protection for Active Distribution Network

The current differential protection is introduced into the active distribution network to improve the selectivity and reliability of protection. However, it is difficult to meet the synchronous requirement of differential protection for distribution networks. Therefore, this paper proposes an impedance differential protection for the active distribution network. The principle and criterion of the impedance differential protection are established according to the significant differences between differential impedance and restraint impedance during normal operation, external fault, and internal fault. Furthermore, an auxiliary criterion is constructed by the amplitude characteristic of fault current to cope with the existing dead-zone fault. A complete protection scheme based on the proposed principle is designed. Several major factors are taken full consideration in the scheme including transition resistances, current transformer saturation, unsynchronized data, various penetrations, and underground cables. Extensive digital simulations are conducted to verify the principle. Theoretical analyses and simulations demonstrate the effectiveness and advantage of this principle. Compared with current differential protection, the impedance differential protection significantly reduces the requirement of data synchronization and transmission bandwidth, which plays an important role in adapting to the communication infrastructure of distribution network.

NOMURA: A Spectrally Efficient Non-orthogonal 5G Multiple Access Downlink Scheme for Cognitive Radio

ABSTRACTOrthogonal Frequency Division Multiple Access (OFDMA) is now becoming an impeding rather than a sustainable technology for realizing the vision of 5G due to its tight synchronization, orthogonality constraints, and significant bandwidth wastage due to Cyclic Prefix. To overcome this limitation, several non-orthogonal schemes have been introduced as candidates for upcoming 5G technology for providing flexible, reliable, fair and high-speed multiple access to users and/or devices. A combination of Non-Orthogonal Multiple Access (NOMA) and Universal Filtered Multi-Carrier (UFMC) is found suitable for downlink scenario. We propose NOMA-UFMC-based Radio Access (NOMURA) scheme, which is asynchronous, bandwidth efficient and provides higher throughput. The proposed scheme is non-orthogonal in two aspects: (1) NOMA provides resources to different users via power scaling while utilizing same frequency resources, and (2) UFMC allows for a slight delay in synchronization, hence not strictly compliant with orthogonality requirements. The components of the proposed scheme, namely NOMA and UFMC, are backward compatible with OFDMA ensuring trivial application of Multiple Input Multiple Output and other performance enhancement measures already developed for OFDMA. We provide simulation results benchmarked against OFDMA and Filter Bank Multi-Carrier-Filtered Multi-Tone and show that NOMURA is more apt for flexible bandwidth allocations, active cancellation, higher throughput and provides equivalent Bit Error Rate performance under AWGN and Rayleigh fading conditions.

External driving synchronization in a superconducting quantum interference device based oscillator

We propose an external driving, self-sustained oscillator based on superconducting resonators. The dynamics of the self-sustained oscillator can be described by a Duffing–van der Pol like equation. Under external driving, the self-sustained oscillator presents synchronization phenomena. We analytically and numerically investigate the synchronization regions, and the results show that the synchronization bandwidth can be quickly adjusted in situ by the external weak magnetic field in sub-nano seconds. Moreover, the system can re-stabilize in about 10 ns with a certain sudden change of driving frequency or the critical current of the superconducting quantum interference device (SQUID). These advantages allow the potential applications of self-sustained oscillators in timing reference, microwave communication and electromagnetic sensing.

Noise enhanced the electrical stimulation-contractile response coupling in isolated mouse heart

BackgroundStochastic resonance is a phenomenon that allows a system to improve its capability to detect stimulus when a limited amount of noise is added to the stimuli. It has experimentally been shown that noise enhances the homeostatic function of the blood pressure regulatory system. This study aimed to investigate whether the noise can enhance the contractile response in the whole heart. MethodsExperiments were conducted in isolated mouse hearts (0.040kg, n=8), a Langendorff heart preparation is used to obtain two variables of the contractile response contraction force and heart rate. The contractile response due to an electrical stimulation perturbed with Gaussian noise was recorded. ResultsThe results show that the intensity of noise induced in the electrical stimuli has an effect on the electrical stimulation-contractile response coupling. With 10% noise induced, the bandwidth where the synchronization effect is presented was increased from (7–11Hz) to (6–12Hz), and the irregular dynamic threshold was changed to 13Hz. ConclusionsWe find that the noise increases the synchronization bandwidth in the electrical stimulation-contractile response coupling. We have experimentally demonstrated the stochastic resonance in isolated mouse heart.

Optimization setup based on multi-tone harmonic balance for the direct and accurate control of the locking range of rationally synchronized oscillators

In this work, a new approach for the optimization of the locking range of rationally synchronized oscillators (RSO) is presented. The proposed method is based on a non-linear optimization setup, easily implementable on commercial harmonic balance software packages, which involves two copies of the circuit. An auxiliary generator (AG) is connected to each copy. The AGs are used to set the working points of the two circuit copies around the limits of the locking range, through the control of the phase of the autonomous signals. A conventional optimization process is then used to increase the synchronization bandwidth by changing the working frequency of one or both AGs. The synchronization loci of the RSO will be calculated to determine the achieved locking range and to analyze its dependence with the amplitudes of the synchronizing harmonics.

General Formulation for the Analysis of Injection-Locked Coupled-Oscillator Systems

The use of an external injection-locking source prevents undesired frequency shifts in coupled-oscillator systems. Here an explicit formulation for the analysis of these systems is presented, based on a numerical model of the oscillator elements in free-running regime, obtained with harmonic balance. It demonstrates the opposed effects of oscillator coupling and injection locking in a realistic manner and brings to light the influence of the oscillator characteristics and coupling-network parameters. The explicit expressions provide the minimum injection-locking power required for a full variation of the inter-stage phase shift and enable the locking bandwidth to be fixed or maximized through a suitable choice of the coupling networks. Two different cases are considered: a basic system of three oscillator elements and a general system with any number of elements. In the latter case, the influence of the particular element chosen for the signal injection on the synchronization bandwidth is studied. The stability analysis is based on a perturbation system, which, unlike previous works, relies on a direct analytical calculation of the steady-state solutions, instead of a numerical one. This enables the full coverage of all possible solutions and hence an in-depth understanding of the influence of the coupling network and injection source on the stable phase-shift ranges. The phase noise analysis, applied to the same explicit formulation, demonstrates the injection locking effects and enables the identification of different regions as the offset frequency increases.