The impact of synchronization on the performance of FDL buffers

Circumventing the speed bottleneck of electronic switching, novel switching approaches like optical burst switching (OBS) and optical packet switching (OPS) handle the switching of bursts (or packets) in backbone nodes optically, and include a set of fiber delay lines (FDLs) for optical buffering. While previous work acknowledges the performance difference between optical FDL buffers and electronic RAM buffers, the important role of synchronization herein has received little attention to date.     

Comparison of ATM switching architectures

Clear examination of work currently done within CCITT indicates the importance of a broadband telecommunication network. As this network should be capable of integrating all services in an efficient way—in order to reduce cost—the asynchronous transfer mode (ATM) was selected by CCITT as the target transfer mode for implementing the broadband integrated services digital network (BISDN). This selection implies that the switching nodes in the BISDN network are capable of supporting this high-speed packet and connection-orientated technique. Within the literature different switching node architectures based upon ATM have been proposed. All of these architectures should meet the high-speed and high-throughput requirements so as to cope with the delay and jitter performance objectives. In a first step this paper describes alternative switching techniques for the basic building block (switching element) of a switching node. A common model architecture of the switching element is drafted. A classification of switching elements described in the literature is derived and the influence on the complexity and performance is weighted. In a second step the switching node architecture is further elaborated according to the control and flexibility requirements. Core (switching) and edge (switching related) functions are listed, and possible functional partitionings are discussed. Finally, these ATM switching architectures are compared according to a background frame consisting of several straightforward comparison points such as the buffering strategy, the internal routeing method, the switching overhead, the connection-orientated or connectionless operation, etc.     

Size effect on polarization switching kinetics of P(VDF-TrFE) copolymer nanodots

We demonstrate polarization switching kinetics of poly(vinylidene fluoride-ran-trifluoroethylene) P(VDF-TrFE) nanodots depending on their sizes. Ferroelectric copolymer P(VDF-TrFE) nanodots, ranging from 20 to 250 nm in lateral size, were deposited on a Nb-doped SrTiO₃ substrate by a position-controlled dip-pen nanolithography technique. Ferroelectric switching characteristics of P(VDF-TrFE) nanodots was investigated by piezoresponse force microscopy. Asymmetric switching behavior was observed during switching process, indicating that the threshold electric fields for polarization reversal were measured differently under the same conditions according to the switching polarity. Significantly, when the size of P(VDF-TrFE) nanodot approached around 250 nm, electric fields for polarization switching were compatible with those of the P(VDF-TrFE) thin film. We suggest that the electric fields required for polarization reversal of the P(VDF-TrFE) nanodots present asymmetric switching behaviors, and asymptotic behavior be observed as the nanodots increase in lateral size.     

Parametric fault detection of analog circuits based on Bhattacharyya measure

A high energy and area efficiency switching scheme for successive approximation register (SAR) analog-to-digital converter (ADC) is presented. The proposed procedure achieved 99.8% saving in switching energy and 97.4% reduction in total capacitance when applied to a 10-bit SAR ADC, compared to the conventional switching scheme. The switching energy has been calculated by taking into account both the power consumed in the switching processes and the reset energy.     

Ingénierie des systèmes de commutation optique et des réseaux locaux à large bande sur fibres optiques : analyses et perspectives

This paper first reviews how switching evolves in the ISDN environment with emphasize placed on changes in conventionnal time-division switches, then assesses techniques and technologies usable in optical switching and broadband networks : optical space-division switching systems (architecture, technologies based on dielectrics, semiconductors, photorepactive material) and optical time-division switching (optical memories based on delay lines and on bistable components multiplexing); multiple access networks (tdma, multiple access by code) ; switching using spread spectrum (bit switching); wavelength switching (multiplexer-demultiplexer, tunable laser and filters) ; packet switching in multi-wavelength networks (broadband networks standardization, local area networks with bus, passive star or multi-star configuration).     

光突发交换中的路由技术

光突发交换是面向下一代因特网的光交换模式,是光电路交换和光分组交换的有效折衷方案,避免了各自的缺点.它使用的带宽粒度介于光电路交换和光分组交换之间,比光电路交换灵活,带宽利用率高,比光分组交换易于实现,是很有发展前途的光交换技术.路由技术在光突发交换中起重要作用,在很大程度上影响着光突发交换网络的性能.本文首先介绍了光突发交换技术的原理,然后分析了光突发交换技术的现状及存在的问题,最后探讨了光突发交换中的路由技术及其发展.     

Switching analysis of tunnel-diode pairs†

The switching behaviour of tunnel-diode combinations in series and parallel modes has been studied theoretically. It is found that the series combination produces larger voltage swing, providing a smaller switching time/volt (nsec/volt) — a desirable feature in switching applications. On the other hand, the parallel mode results in a larger fan-out current with a reduced switching time/current (nseo/mA) which has wide applications in current triggering.     

An expandable time-division circuit switching LSI and networkarchitecture for broadband ISDN

A broadband network architecture is proposed that integrates multimedia services, such as data, video, and telephony information, using 52-Mb/s based STM-paths at the user network interface (UNI). The user can access any new service via the STM-based access network via either synchronous transfer mode (STM) switching or asynchronous transfer mode (ATM) switching. STM circuit switching supports long duration, constant bandwidth data transfer services such as video and high-definition television (HDTV) distribution and will also be used for the crossconnect system. Circuit switching can provide transparent transmission during long connection periods. This paper also proposes an expandable time-division switch architecture, an expandable time-division switching LSI, and an expandable switching module for small to large size system applications. The proposed time-division switching LSI, module, and system handle 52-Mb/s bearer signals and have throughputs of 2.4 Gb/s, 10 Gb/s, and 40 Gb/s, respectively. The time-division switch realizes video distribution with 1:n connections. Finally, a local switching node that features an expandable 52-Mb/s time-division circuit switching network is shown for multimedia access networking     

Optimal Variable Switching Frequency Scheme for Reducing Switching Loss in Single-Phase Inverters Based on Time-Domain Ripple Analysis

The choice of switching frequency for pulsewidth modulation single-phase inverters, such as those used in grid-connected photovoltaic application, is usually a tradeoff between reducing the total harmonic distortion (THD) and reducing the switching loss. This paper discusses an approach to minimize the switching loss while meeting a given THD requirement using variable switching frequency schemes (switching schemes with the switching frequency varying within a fundamental period). An optimal switching scheme is proposed based on time-domain current ripple analysis and the calculus of variations. The analysis shows that, to meet the same THD requirement, the optimal scheme has a significant saving on switching loss, compared to the fixed switching frequency scheme and the hysteresis control scheme, in addition to other benefits such as reduced peak switching loss and a spread spectrum of the current harmonics. The optimal scheme has been implemented in a prototype and the experimental results have verified the theoretical analysis. Also, a straightforward design method for designing filter inductors for single-phase converters is provided based on the time-domain current ripple analysis.     

Reconfigurable wavelength add-drop filtering based on a Banyannetwork topology and ferroelectric liquid crystal fiber-optic switches

This paper presents a modular optical implementation of a Banyan network by using the physical flexibility of the optical fiber to form the interconnections between compact switching stages based on bulk polarization optics. Specifically, these switching stages use total internal reflection (TIR) prisms with ferroelectric liquid crystal (FLC) polarization rotators to form compact modules. Using this Banyan network implementation, a reconfigurable multiwavelength add-drop filter for wavelength division multiplexed (WDM) applications is proposed. Experimental results for our fiber connected 2 in-2 out FLC-based bulk-optic switching stage gives a ~6.7 dB optical insertion loss and a ~-40 dB optical interchannel crosstalk level. A low 2 dB optical insertion loss design number is expected with optimized components, realizing high (e.g., 35 μs) switching speed and low crosstalk switching networks     

Stability of a class of linear switching systems with time delay

We consider a switching system composed of a finite number of linear delay differential equations (DDEs). It has been shown that the stability of a switching system composed of a finite number of linear ordinary differential equations (ODEs) may be achieved by using a common Lyapunov function method switching rule. We modify this switching rule for ODE systems to a common Lyapunov functional method switching rule for DDE systems and show that it stabilizes our model. Our result uses a Riccati-type Lyapunov functional under a condition on the time delay.     

Switching scheme with 98.4% switching energy reduction and high accuracy for SAR ADCs

An energy-efficient digital-to-analogue converter (DAC) switching scheme with high-accuracy is proposed for successive approximation register (SAR) analogue-to-digital converters (ADCs). By utilizing a complementary switching method, the proposed switching scheme achieves a 98.4% switching energy reduction and a 75% area reduction compared to the conventional SAR ADC. Moreover, the accuracy of the SAR ADC is independent on the accuracy of the third reference voltage (V_cm) except the least significant bit, and the common-mode voltage of the DAC outputs keeps approximately unchanged during a conversion cycle, making the design of the SAR ADC more relaxed.     

Low power SAR ADC switching without the need of precise second reference

In this paper a simple method to reduce the switching energy of capacitive digital-to-analog converters (DACs) in low-power successive approximation register analog-to-digital converters (ADCs) is described. The method is based on the well-known monotonic switching procedure and the use of one intermediate voltage level during switching. Unlike most recently published switching methods the proposed method does not require the intermediate voltage to be accurate. The implementation of digital control and an intermediate voltage-level generator is considered. To evaluate the reduction in switching energy compared to the conventional monotonic switching procedure, the behavioral model of a 10-bit ADC was examined. The additional digital logic, voltage generator, and capacitive DAC were modeled at a transistor level using a 65 nm STM design kit. Simulation results and the subsequent power efficiency gains are presented.     

A centroid-based PWM switching technique for full-bridge inverterapplications

A novel centroid-based pulse-width-modulation (PWM) switching strategy is proposed which is suitable for full-bridge inverter applications. This method is evaluated, and its performance is compared with existing PWM switching strategies. The performance evaluation and comparison are based on the total harmonic distortion (THD) and number of pulses per cycle of the inverter output waveform. The objective of the new switching strategy is to minimize both the THD and low-order harmonics. Simulation results show that this technique yields a significant improvement in performance. In addition, a hybrid switching sequence is developed for the proposed scheme, which can lead to further reduction in switching losses     

基于聚乙烯咔唑的非挥发型阻变存储特性分析

采用聚乙烯咔唑作为活性层构建了ITO/PVK/Al的三明治结构阻变存储元件,并对其阻变特性进行了测量。结果表明其具有明显的非挥发型双稳态阻变特性, 具有WORM存储特性。该元件具有良好的数据保持能力和耐久能力,开关态电流比可达103,且具有较低的阈值转换电压。分别对低阻态和高阻态的载流子传输机制进行了拟合, 低阻态为欧姆传导机制,高阻态为空间电荷限制电流发射机制。根据载流子传输机制, 对阻变特性进行了解释。     

Optimization of multi-branch switched diversity systems

A performance optimization based on the optimal switching threshold(s) for a multi-branch switched diversity system is discussed in this paper. For the conventional multi-branch switched diversity system with a single switching threshold, the optimal switching threshold is a function of both the average channel SNR and the number of diversity branches, where computing the optimal switching threshold is not a simple task when the number of diversity branches is high. The newly proposed multi-branch switched diversity system is based on a sequence of switching thresholds, instead of a single switching threshold, where a different diversity branch uses a different switching threshold for signal comparison. Thanks to the fact that each switching threshold in the sequence can be optimized only based on the number of the remaining diversity branches, the proposed system makes it easy to find these switching thresholds. Furthermore, some selected numerical and simulation results show that the proposed switched diversity system with the sequence of optimal switching thresholds outperforms the conventional system with the single optimal switching threshold.     

Mode switching control design with initial value compensation andits application to head positioning control on magnetic disk drives

To meet an increasing demand for high performance and large-capacity in magnetic hard disk drives, both fast response and precise positioning are strongly required for the head positioning control. A mode switching control (MSC) system, which includes a track seeking controller, a track following controller, and a switching function, is widely used to meet this requirement. The issue for MSC is to confirm a design method of servo mode switching. This paper proposes the initial value compensation method (IVC). The IVC inputs certain initial values in the controller state variables at mode switching in order to improve the transient response after switching. There are two approaches to determine the values: (1) minimizing a linear-quadratic function of the plant state variables; and (2) cancelling the unfavorable poles of the transfer function between initial values and head position by relocating zeros. Some experimental results are shown to be effective     

Electronic step down (220/110 V) transformer using a new quantumseries resonant converter

A novel quantum series resonant converter (QSRC) topology for a pure sinewave 60 Hz AC chopper is proposed. It has three bidirectional switches and operates at high switching frequency with low switching loss. Bidirectional power flow is possible, and the switches can operate in either zero current switching (ZCS) mode or zero voltage switching (ZVS) mode by slight modification. The QSRC is thought to be suitable for such a system with fixed voltage conversion ratio. The proposed converter is applied to an electronic 220/110 V transformer. Detailed analyses and experimental results for 1 kVA are presented     

A coherent photonic wavelength-division switching system forbroad-band networks

A coherent photonic wavelength-division (WD) switching system, utilizing a coherent wavelength switch (λ switch), is proposed. In the proposed coherent λ switch, the tunable wavelength filter function is accomplished using coherent optical detection with a wavelength tunable local oscillator. The coherent photonic WD switching system has the following features; (1) low crosstalk switching for dense WDM signal, and (2) large line capacity capability. Design considerations show that 32 wavelength division channels can be available with a coherent λ switch. It is also shown that a broadband metropolitan-area-network with over 1000 line capacity is possible, using a multistage connection in the coherent λ switches. The switching function of the coherent λ switch is demonstrated in a two-channel wavelength-synchronized switching experiment, using 8-GHz-spaced, 280-Mb/s optical FSK signals     

The new switching effect in liquid selenium

Liquid selenium shows above 720°C a reversible switching from higher to lower conductance effected by an electric field. Below 720°C liquid selenium switches first to higher and then to lower conductance. After switching to low conductance, a voltage controlled negative resistance is observed. By means of a single pulse technique the current oscillograms of the switchings (switching to high conductance, to low conductance and multi-switching) are investigated. The influence of magnetic field upon the switching (delay time and threshold voltage) is investigated. An electronic explanation for the switching and the influence of the magnetic field on it is given.