Fast wavelength switching of three-section DBR lasers

For optical crossconnect and packet switched applications based on fast wavelength switching of distributed Bragg reflector (DBR) lasers, the wavelength switching delay is an important device characteristic. A large-signal model for a three-section DBR laser is described which permits evaluation of the intramodal and intermodal wavelength switching delay. The steady-state mode spectrum and loss obtained from a transmission line model of the laser are used in modified multimode rate equations to explicitly include the device structure and operating conditions in the dynamic model. Mode competition is shown to cause the intermodal wavelength switching delay to increase significantly as the destination wavelength approaches the edge of a mode tuning curve. The same behaviour is observed experimentally     

Characteristics of metal/tunnel-oxide/n/p+ silicon switching devices—II: Two-dimensional effects in oxide-isolated structures

Effects of oxide isolation on the two-terminal D.C. characteristics of metal/tunnel-oxide/n/p⁺ silicon switching devices have been studied.Recent experimental results have shown that the switching characteristics are strongly dependent on area, and area-to-perimeter ratio of the device. To carry out a systematic investigation of this phenomenon, the devices in this study were isolated using V-grooves of various areas. For a given tunnel-oxide thickness and area, it was found that the magnitude of the switching voltage and holding current of the device increased with isolation area, whereas the switching current remained essentially constant. Furthermore, it is shown that the switching current is almost completely determined by the characteristics of the tunnel-oxide; in particular, the minority carrier concentration at the SiSiO₂ interface. Physical arguments are presented which adequately explain the observed trends. It is also experimentally shown that both switching current and holding current decrease as the tunnel-oxide thickness is increased.A simple two-dimensional model for the oxide-isolated MISS device is derived which effectively explains the above area-related phenomena. In agreement with experimental results, the model predicts that for a given tunnel-oxide thickness and area, an increase in switching voltage magnitude and holding current will result as the isolated p⁺-n junction area is increased. Calculations based on this model are shown to be in good agreement with experimental data.     

Characterisation of electrical and optical base controlled switching in the V-groove isolated punch through mode mist

The base controlled switching characteristic of the isolated, punch through mode metal-insulator (tunnel)-silicon thyristor is examined under various base inputs. It is shown that an excitation threshold and sensitivity are sufficient to characterise the electrical and optical base controlled switching modes. A simple model is presented which adequately explains the observed switching characteristics for both electrical and optical excitations. Furthermore for the optical case, the responsivity is derived and measured in order to provide a basis for comparison with existing photodetectors.     

Design considerations of IGBT's in resonant converter applications

The switching dynamics of insulated gate bipolar transistors (IGBT's) in zero voltage switching (ZVS) resonant converter applications is studied and optimized using an advanced mixed device and circuit simulator. It is shown that bipolar and MOS device parameters must be carefully optimized to obtain the lowest total power loss. A simple circuit simulation model was used in an advanced behavioral circuit simulator where the model parameters were extracted from mixed device and circuit simulations. Performance analysis of a typical series resonant converter (SRC) shows that ZVS condition is more favorable than the zero current switching (ZCS) condition from the standpoint of obtaining efficient power conversion. It is shown that IGBT's with narrower source result in lower total switching power loss     

Modeling the switching performance of a MOSFET in the high side of a non-isolated buck converter

This paper uses generic equations to model the switching performance of metal oxide semiconductor field effect transistors (MOSFETs). Two MOSFETs with different gate structures are analyzed and switching times are presented, which are compared against practical measurements. It is shown that it is possible to get a reasonable accuracy of the switching performance of a MOSFET in a nonsynchronous buck converter, but care must be taken to ensure the correct values of the parameters are used. It is also shown that the MOSFET with the thick bottom oxide gate provides a faster switching instant when compared to a conventional U-Trench gated MOSFET.     

A behavioral circuit simulation model for high-power GaAs Schottky diodes

This paper proposes a physically based behavioral circuit simulation model for high-power GaAs Schottky diodes which is valid over all regions of operation. No conditional statements are needed to define the regions of operation. A new and more accurate method of obtaining depletion capacitance model parameters from the measured capacitance values is proposed. A simple current- and temperature-dependent resistance model is used to model the nonlinear diode resistance as well as contact and packaging resistances. The validity of the model is demonstrated under various DC and transient switching conditions. Simulation results are compared with the experimental data obtained from a 200 V GaAs Schottky diode. The diode model is tested at various temperatures in different test circuits and the simulation results are shown to be in excellent agreement with the measured data under static and dynamic switching conditions. The model can be easily implemented in other circuit simulators.<>     

解决光突发交换竞争的新模型

针对光突发中的竞争问题，提出了一种分割反馈模型，相应地建立了数学分析模型，并进行了仿真与性能分析。结果表明这一模型是解决光突发交换中竞争问题的一个较佳方案。     

Phasor transformation and its application to the DC/AC analyses offrequency phase-controlled series resonant converters (SRC)

A novel modeling technique based on phasor transformation that provides a unified model of series resonant converters (SRCs) is proposed. The approach gives explicit and simple equations that provide fruitful physical insight. When the switching frequency deviates from the resonant frequency, a first-order SRC model is obtained, and in the case of resonance a second-order model is obtained. It is shown that the frequency band of the second-order model is very narrow in practice. The time constant, small-signal gains, and system order are highly dependent on the switching frequency, load resistor, and output capacitor     

Analysis and characterization of P-N junction diode switching

A new charge control model of a p-n junction diode is introduced in which the reverse current iRas well as the forward current IFare related to the chargeQstored in the base region by time constants τRand τF, respectively. The reverse switching transient is analyzed for normal switching operation where a constant current phase (storage phase) and a decaying current phase exist, and for overdriven switching operation where no constant current phase exists. New switching time equations are derived. The equations are expressed in terms of measurable device parameters τF, τR, and Cjexternal circuit variables IFand IRand an external circuit parameter R. The proposed model is applicable to p-n junction diodes of any type. Experimental results using various types of diodes are also reported. It is shown that the experimental results are in very good agreement with the theory.     

A frequency-domain analytical model of an uncontrolled single-phasevoltage-source rectifier

The harmonic currents generated by the single-phase rectifier are well known. As the levels of these currents become larger, the use of power conditioners, such as shunt active filters, to lower the levels is becoming more attractive. In order to analyze the interaction between the condition, AC system and rectifier, it is necessary to have an accurate model of the rectifier. This paper describes a frequency-domain analytical model of the single-phase rectifier. The model includes the dominant frequency transfer mechanisms. These are the direct transfer and that due to the modulation of the switching instants. A small-signal linearized analysis is presented and the behavior predicted is confirmed by perturbation analysis using time-domain simulation. Accurate results are obtained, and the importance of including the switching instant modulation is shown     

Dimensioning an ATM switch based on a three-stage Clos interconnection network

ATM (asynchronous transfer mode) is a new technique for transmitting voice, data and video. The performance of atm networks will depend on switch structure. Performance analysis of an atm switch based on a three-stage Clos network is presented. In this paper two types of switches are studied: a switch with input queues in the switching elements and a switch with output queues. This study is at the cell level and intends to dimension the switch. First, the traffic is supposed to be uniform, cells arrive on each input according to a geometric arrival process, they are uniformly directed over all the network outputs. An analytic model is proposed for both input and output queues in the switching elements. A study of the saturation throughput is proposed for input buffer switching elements. This work proves the influence of buffer dimensioning on the different stages of the switch. Dissymmetric switching elements are shown to be better than symmetric ones. A model is then designed for nonuniform traffic patterns and output buffers. Two types of non-uniform traffic are presented: single source to single destination (sssd) and multi-hot spots traffic (mhs). Discrete event simulations are used to validate the different models.     

Switching in polymeric resistance random-access memories (RRAMS)

Resistive switching in aluminum-polymer-based diodes has been investigated using small signal impedance measurements. It is shown that switching is a two-step process. In the first step, the device remains highly resistive but the low frequency capacitance increases by orders of magnitude. In the second step, resistive switching takes place. A tentative model is presented that can account for the observed behavior. The impedance analysis shows that the device does not behave homogenously over the entire electrode area and only a fraction of the device area gives rise to switching.     

开关功率变换器符号分析方法的原理

本文介绍了ＰＷＭ开关功率变换器的一种符号分析方法，着重阐述了该方法的一般原理，这一方法容易得到输出纹波的解析表达式以及系统的小信号模型，兼有计算过程简单和准确度较高的优点，可望成为功率电子学领域比较通用的一种方法。     

GaAs—Si photon-activated switch

A light-activated low-level switch (LAS) has been developed for multiplexing applications. The switch consists of an electroluminescent GaAs p-n diode and a double-emitter silicon transistor. (Both NPN and PNP units have been made.) The two, light emitter and detector, are coupled optically. The switch is a substantial improvement over existing switching devices used in multiplexers. A general design theory based on the Ebers & Moll [1] low-level transistor model is given, with special emphasis on breakdown voltage, ON impedance, offset voltage, and switching speed. It is shown how the design considerations lead to a specific geometry for the detector. Results of extensive testing are reported.     

Performance Analysis of a Packet Switch Based on Single-Buffered Banyan Network

Banyan networks are being proposed for interconnecting memory and processor modules in multiprocessor systems as well as for packet switching in communication networks. This paper describes an analysis of the performance of a packet switch based on a single-buffered Banyan network. A model of a single-buffered Banyan network provides results on the throughput, delay, and internal blocking. Results of this model are combined with models of the buffer controller (finite and infinite buffers). It is shown that for balanced loads, the switching delay is low for loads below maximum throughput (about 45 percent per input link) and the blocking at the input buffer controller is low for reasonable buffer sizes.     

An upper limit for high power switching with a polymer currentlimiter device

The high power electrical switching properties of a polymer current limiter device configured to switch at only one electrical contact are studied as a function of applied voltage. It is shown that a dramatic change in switching behavior occurs at a characteristic voltage. Below this voltage, the device switches to a high resistance state whereas at higher applied voltages it does not. It is shown that the high voltage, low resistance state has similar electrical characteristics to an arc discharge and a qualitative model for the state is proposed. Material variation experiments are also described which demonstrate that the voltage at which the observed change in switching behavior occurs depends sensitively on the composite material composition and fabrication parameters     

Performance and Optimization of Switched Diversity Systems for the Detection of Signals with Rayleigh Fading

The performance and optimization of switched diversity systems are considered. First, the one-dimensional distribution and probability density functions of the envelope of the received signal are obtained for three different switching strategies. This information is used to obtain the average probability of bit error for the case of non-coherent detection of binary FSK signals with Rayleigh fading envelopes and additive white Gaussian noise. The optimization of two of these switching strategies is then considered, and it is shown that by proper selection of switching thresholds, the average probability of bit error during detection can be minimized. It is also shown that these optimized switching strategies yield a significant improvement in performance over non-diversity systems and can approach the performance of more complex receivers such as maximal ratio combining. Computer simulations of switched diversity systems using a practical field model are used to verify the analysis.     

All-optical flip-flop based on coupled laser diodes

An all-optical set-reset flip-flop is presented that is based on two coupled lasers with separate cavities and lasing at different wavelengths. The lasers are coupled so that lasing in one of the lasers quenches lasing in the other laser. The flip-flop state is determined by the laser that is currently lasing. A rate-equation based model for the flip-flop is developed and used to obtain steady-state characteristics. Important properties of the system, such as the minimum coupling between lasers and the optical power required for switching, are derived from the model. These properties are primarily dependent on the laser mirror reflectivity, the inter-laser coupling, and the power emitted from one of the component lasers, affording the designer great control over the flip-flop properties. The flip-flop is experimentally demonstrated with two lasers constructed from identical semiconductor optical amplifiers (SOAs) and fiber Bragg gratings of different wavelengths. Good agreement between the theory and experiment is obtained. Furthermore, switching over a wide range of input wavelengths is shown; however, increased switching power is required for wavelengths far from the SOA gain peak     

The process of arc splitting between metal plates in low voltage arc chutes

The behavior of arcs in low voltage switching devices is affected by several interactions. For studying simple arrangements of arc runners without metallic splitter plates ("deion plates") a three-dimensional simulation system has already been developed. It takes into account the plasma fluid dynamics, the current flow within the electrodes and the plasma, and the magnetic field generated by both currents. In order to model the arc splitting process simulations with an insulating barrier were done in a first step. For the simulation of the splitting process between metallic deion-plates the simulation model has to be extended. In experiments including high-speed movies it is shown that this process is a continuous transition of current flow from the still undivided arc to the new arc roots formed on the metal plates. A new simulation model representing the roots by a thin layer of current-dependent resistivity is discussed and simulation results are compared with switching experiments.     

Optical crosstalk-induced switching between bistable soliton states

It is shown that the controlled use of optical crosstalk can induce switching between bistable soliton states in a fiber whose intensity-dependent refractive index is described by the linear plus smooth step model. The closely related phenomena of soliton fission, soliton fusion, radiation stripping, and the soliton transparency-extinction transition are also examined. The evanescently coupled model equations use are discussed, and numerical results are given. It is stressed that the general features of the crosstalk-induced switching and related phenomena do not depend on the specific nonlinearity (the LSS model) chosen