小型化行波管直角弯头输入结构设计

本文对某一微波功率模块(MPM)用小型化行波管的直角弯头输入结构进行了降低结构高度的研究。新直角弯头输入结构的高度从原结构的28.4mm减小到15.8mm,输入匹配性能也得到同步提升。MPM的宽度可由此减小12.6mm,因此可获得更高的集成度。     

Optically Injection-Locked VCSEL as a Duplex Transmitter/Receiver

We propose and experimentally demonstrate a novel communication system scheme with an optical injection-locked vertical-cavity surface-emitting laser (OIL-VCSEL) acting both as a transmitter and as a receiver, under an identical forward-bias condition. We show that an OIL-VCSEL can function as a receiver with a small signal modulation bandwidth of ~20 GHz, and for large signal digital modulation with data rate as high as 12 Gb/s.     

Entropy and data compression schemes

Some new ways of defining the entropy of a process by observing a single typical output sequence as well as a new kind of Shannon-McMillan-Breiman theorem are presented. This provides a new and conceptually very simple ways of estimating the entropy of an ergodic stationary source as well as new insight into the workings of such well-known data compression schemes as the Lempel-Ziv algorithm     

Vertical cavity surface-emitting semiconductor laser with CWinjection laser pumping

Room-temperature CW operation of a GaAs/AlGaAs vertical cavity surface-emitting laser with a resonant periodic gain medium, using a GaAs/AlGaAs diode laser array as a pump source, is discussed. Pumping thresholds as low as 11 mW at 730 nm, output powers as high as 10 mW at 856 nm, and external quantum efficiencies as high as 70% are obtained, with considerably improved temporal and spatial coherence properties compared to the pump laser. This is the first reported operation of such a laser with an efficient, compact pump source, demonstrating its suitability for efficient integration     

10-GHz ultralow-noise optical sampling stream from a semiconductordiode ring laser

We report, what is to our knowledge, the lowest-noise pulsetrain produced to date with an actively mode-locked external-cavity semiconductor diode laser. Operating characteristics at 10 GHz include dispersion-compensated pulsewidths as short as 1.2 ps, amplitude noise as low as 0.12% rms, and residual phase noise as low as 43-fs rms. Potential application of such a laser in a next-generation optical analog-to-digital converter would theoretically provide as much as 8.6 bits of resolution, while sampling a 5-GHz waveform at the Nyquist frequency     

A fast 7.5 ns access 1K-bit RAM for cache-memory systems

A 1024-bit ECL RAM with greatly improved speed performances was developed. Typical access time and write cycle time are as short as 7.5 and 10 ns, respectively, under 784 mW of power dissipation, achieving a power and access-time product as small as 5.7 pJ/bit. Novel ECL circuit techniques, especially in address decoder circuits, as well as improved process technologies enabled realizing these high-speed characteristics. The device uses a V-groove isolation process and a shallow emitter diffusion technology with doped polysilicon. It has a memory organization of 256-words by 4-bits where its main use is as a cache memory. Besides this basic organization, it has flexibility to also operate as a 512-word by 2-bit and 1024-word by 1-bit memory.     

Performance analysis by simulation of floating-gate MOSFETs applied on a bidirectional associative memory architecture

Floating-gate MOSFETs (FGMOSFETs) are devices that can be electrically programmable and have a non-volatile characteristic. This feature can be adopted to configure a basic cell performing as a variable resistance that can be applied in artificial neural networks as a synapse. Based on a simple model and considering the coupling coefficient of the structure as the gain of a voltage controlled voltage source, the electrical characteristics of a floating-gate MOSFET can be simulated in PSpice and an artificial neural net, such as the bidirectional associative memory (BAM), can be implemented. Therefore a performance analysis of the net may be done with different sets of threshold voltages for the FGMOSFETs configured as a CMOS inverter used as a synapse. The objective is to know pattern pairs in a bidirectional way. The result is a correlation matrix for the BAM as a function of an electrical parameter of the devices, which is directly related to the respective matrix calculated by the matrix dot product, using the method outlined by Kosko.     

Development of a hybrid switcher locomotive the Railpower Green Goat

The Green Goat, a diesel/battery hybrid switcher locomotive, demonstrated impressive fuel savings as the engine never operates at idle as on a conventional locomotive. The Railpower Green Goat locomotive design incorporates all of the above features, but most importantly, focuses on keeping the concept as well as the implementation as simple as possible. During initial trials at the Union Pacific Railroad in Chicago, Illinois, customer input was paramount in the design of the locomotives, and most customers encouraged as simple a design as possible. Hybrid locomotives are meeting the needs of the train industry. The partnering of a small heat engine with an energy-storing device has created a product with much more efficient fuel use and maneuverability. Our train system continues to be an important part of our economy, and advances in this technology show great promise now and in the years to come.     

Sliding-Mode Control of a High-Speed Linear Axis Driven by Pneumatic Muscle Actuators

This paper presents a cascaded sliding-mode (SM) control scheme for a new pneumatic linear axis which could be seen as alternative to an electric direct linear drive. Its guided carriage is driven by a nonlinear mechanism consisting of a rocker with an antagonistic pair of pneumatic muscle actuators arranged at both sides. This innovative drive concept allows for both an increased workspace of approximately 1 m as well as higher carriage velocities of approximately 1.3 m/s as compared to a direct actuation. Modeling of the muscle-driven positioning system leads to a system of four nonlinear differential equations including polynomial approximations of the volume characteristic as well as the force characteristic of the pneumatic muscles. The differential flatness of the system is exploited in combination with SM techniques to stabilize the error dynamics in view of unmodeled dynamics. The internal pressure of each pneumatic muscle is controlled by a fast underlying control loop. Hence, the control design for the outer control loop can be simplified by considering these controlled muscle pressures as ideal control inputs. The control design of the outer control loop involves a decoupling of rocker angle as well as mean internal pressure of both pneumatic muscles as flat outputs. Additionally, model uncertainties in the equation of motion like nonlinear friction are directly counteracted by an observer-based disturbance compensation which reduces the chattering problem. Experimental results show an excellent control performance that outperforms alternative control approaches in a comparison.      

Monolithically integrated semiconductor LED-amplifier for applications as transceivers in fiber access systems

We have fabricated a monolithically integrated LED-amplifier chip for application as a high-power broad-band transmitter. Amplified LED output of 10 mW and fiber-coupled power of 4 mW was demonstrated. The device can be used as a spectrally-sliced transmitter for wavelength-division-multiplexed networks or as a broad-band transmitter in subcarrier multiple-access systems to eliminate optical beat interference. The amplifier section in the integrated device can also be used as a photodetector. The performance of the device as a transceiver in a WDM multiple-access system operating at a typically proposed local-access data rate of 10 Mb/s was successfully demonstrated.     

MAMA: a new methodically designed broadband microstrip antenna using off-the-shelf components

The current paper proposes a new, simple, methodical approach to broadband microstrip antenna design. The approach relies on a reformulation of the antenna-design problem as an impedance-matching problem, in which the antenna is considered to be the matching device required to match the feed line to air. Thus, impedance-matching techniques, such as Chebyshev transformers and a Klopfenstein taper, are employed to determine the antenna parameters necessary to satisfy a set of specifications. Simulation results as well as measured results show that the proposed matched-to-air microstrip antennas (MAMAs) qualify as a new class of broadband microstrip antennas, which have the advantages of relying on a systematic approach (as opposed to the usual trial-and-error procedures that are now prevalent), as well as being very easy to fabricate, using inexpensive off-shelf components.     

On factor graphs and the Fourier transform

We introduce the concept of convolutional factor graphs, which represent convolutional factorizations of multivariate functions, just as conventional (multiplicative) factor graphs represent multiplicative factorizations. Convolutional and multiplicative factor graphs arise as natural Fourier transform duals. In coding theory applications, algebraic duality of group codes is essentially an instance of Fourier transform duality. Convolutional factor graphs arise when a code is represented as a sum of subcodes, just as conventional multiplicative factor graphs arise when a code is represented as an intersection of supercodes. With auxiliary variables, convolutional factor graphs give rise to "syndrome realizations" of codes, just as multiplicative factor graphs with auxiliary variables give rise to "state realizations." We introduce normal and co-normal extensions of a multivariate function, which essentially allow a given function to be represented with either a multiplicative or a convolutional factorization, as is convenient. We use these function extensions to derive a number of duality relationships among the corresponding factor graphs, and use these relationships to obtain the duality properties of Forney graphs as a special case.     

Thermal buffer materials for enhancement of device performance of organic light emitting diodes fabricated by laser imaging process

Laser Induced Thermal Imaging (LITI) is a laser addressed thermal patterning technology with unique advantages such as an excellent uniformity of transfer film thickness, a capability of multilayer stack transfer and a possibility to fabricate high resolution as well as large-area display. Nevertheless, it has been an obstacle to use such a laser imaging process as a commercial technology so far because of serious deterioration of the device performances plausibly due to a re-orientation of the molecular stacking especially in the emitting layer during thermal transfer process. To improve device performances, we devised a new concept to suppress the thermal degradation during such kind of thermal imaging process by using a high molecular weight small molecular species with large steric hindrance as well as high thermostability as a thermal buffer layer to realize highly efficient LITI devices. As a result, we obtained very high relative efficiency (by EQE) up to 91.5% at 1000 cd/m² from the LITI devices when we utilize 10-(naphthalene-2-yl)-3-(phenanthren-9-yl)spiro[benzo[ij]tetraphene-7,9′-fluorene] as a thermal buffer material.     

An Intra-Arterial Induction Gauge

A flexible collapsible catheter gauge that can be introduced into an artery through a French 7 catheter is described. It expands when entering a wide blood vessel or tubular organ and the degree of expansion is measured by electromagnetic induction. The sensor consists of two collapsible congruent wire loops, one of which acts as the primary and the other one as the secondary of a transformer. The output of the secondary varies as the logarithm of the artery diameter over a wide range. Variations as small as 0.01 mm in a 10-mm-diameter lumen can be recorded. The paper describes construction of the probe and presents examples of nonradiographic measurement of arterial diameters as well as of recording of pulsatile changes in artery diameter in dogs.     

Design of a Compact Millimeter-Wave Microstrip Antenna with Wide Bandwidth and Broad Beamwidth

Design of a novel compact millimeter-wave microstrip antenna with wide bandwidth and broad beamwidth is presented. In the structure, multiple layers and a parasitic element as well as a coupling aperture are used to achieve wideband, while a conducting cylinder and the coupling aperture are used to obtain broad beamwidth. Finally, phased array with eight present elements has been designed as an example. Compared to traditional microstrip antennas and arrays, present antenna and array are of smaller dimension and broader beamwidth as well as wider bandwidth.     

P2P下载技术在嵌入式设备中的应用

嵌入式系统作为一种低功耗,微内核设备以及本身的硬件限制等各种特点,开发在一种具有下载功能的嵌入式设备很具有商业意义。传统的下载方式是节点和服务器之间交换信息,而P2P技术与传统的C/S方式有很大不同,它允许节点之间直接交换信息,很适合嵌入式系统之中。下本文通过对amule了进行移植,分析了交叉编译环境的搭建,嵌入式调试中的调试技术以及交叉编译过程中遇到的各种问题,成功实现了MIPS平台下的P2P文件共享技术,此外本文还用简洁的语言给出了一个完整的嵌入式开发流程。     

Visual literacy in corporate communication: some implications forinformation design

A model for the design of information products is presented. The model serves as a resource to diagnose ineffective designs as well as a guide for the construction of effective displays. It accommodates many factors affecting the reader's processing of visual displays, including cognitive and perceptual processing, ergonomic factors, and the influence of cultural differences. Because the disciplines employed in this paper are incomplete and often depend upon speculation, the model should not be viewed as complete or comprehensive. However, the model can be modified as information design matures as a discipline     

Via hole studies on a monolithic 2-20 GHz distributed amplifier

The effect of source inductance on the performance of a distributed amplifier is investigated. A simple theoretical analysis shows that optimum performance is obtained with as low a source inductance as possible (as would be intuitively expected), and that the flattest gain and minimum gate line attenuation occur with the inductance common to the whole amplifier rather than parceled out to each FET individually, as would occur for a MIC distributed amplifier. A novel through-the-wafer via hole process has been developed for a low-inductance contact on monolithic circuits. A 2-20 GHz variable-gate-width monolithic distributed amplifier fabricated with this via-hole grounding technique has demonstrated a 2-dB gain improvement as well as a flatter gain profile compared to that without via grounding. Evidence is presented that indicates that MMIC (monolithic microwave integrated circuit) designs may not be as ideal as expected with regard to being typified by the common inductance case     

The MICROMIXER: a highly linear variant of the Gilbert mixer usinga bisymmetric Class-AB input stage

This paper outlines the basic theory of a development of the Gilbert mixer. The bipolar junction transistor (BJT) differential pair widely used as the RF input stage is replaced by a bisymmetric Class-AB topology based on translinear principles. It does not have inherent gain compression, affording a greatly extended signal capacity. The linearity of variants of the basic form is excellent, providing two-tone intermodulation intercepts as high as +30 dBm, without the expenditure of high bias currents. It can operate on supplies as low as 2.2 V, with a power consumption of under 5 mW. The input impedance of this mixer is accurately controllable (typically 50 Ω) and provides a true broadband match. The noise figure depends on design details and is generally not as low as in mixers specifically optimized for noise performance, although acceptable for many receiver applications. Inductively degenerated variants can be tuned to a narrowband match at microwave frequencies and provide full-mixing SSB noise figures as low as 6.5 dB, Practical realizations are in use in applications to 1.9 GHz     

From Remote Experiments to Web-Based Learning Objects: An Advanced Telelaboratory for Robotics and Control Systems

This paper describes the current evolution of the telelaboratory facilities at the University of Pisa. In particular, starting from a standard environment providing remote access to a set of experiments, the telelaboratory is now organized as a collection of learning objects, i.e., modular didactic units designed following specific learning objectives within control systems and robotic fields. The telelaboratory has a remote web-based access which can be used both as a simulation environment and as a remote way of performing real physical experiments. The developed telelaboratory is based on free open-source software such as Scilab/Scicos, Comedi, and Real-Time Application Interface patch for Linux kernels. In-house software tools, such as a Java wEb Hyper modUlar inTerface sYstem, graphic environment tools, and a virtual laboratory interface based on Java applets, have been developed as a support for the learning process.