The L5 Coaxial System Transmission System Analysis

The L5 system design characteristics and features, including the transmission plan, frequency allocation, and predicted noise, intermodulation, and crosstalk performance, are described. The effects of such factors as modulation product addition, misalignment, and mastergroup frogging on system performance are discussed. Signal-signal-to-noise optimization through transmission level shaping is described.     

Main Station, Line Interconnection, and Signal Administration

The L5 line connecting equipment fulfills several functions, including the routing of jumbogroup signals for through, branched, or terminal connections of the message service on the line. Any combination of three jumbogroup signals may be sent along the through route, branched directly to another route, or dropped locally to a multiplex terminal. Line pilots for dynamic equalization, temperature regulation, and office synchronization, as well as tones for fault location and protection switch control, are also administered in the line connecting equipment. The multiplex equipment separates the line signal into three basic lumbogroup signals which may be connected directly to other cable or radio facilities in any combination of up to six contiguous mastergroups through the basic jumbogroup trunk bay. The basic jumbogroups may also undergo further demultiplexing locally for lower forms of circuit administration, such as basic mastergroup, supergroup, group, or even voice frequency.     

Terminal and Main Station Functions

There are three types of main stations associated with the L5 system. Power feed main stations provide the dc power required by the line repeaters. Switching power feed main stations add the automatic line protection switching equipment for the L5 system. Terminal main stations provide the equipment for multiplex and related functions. This equipment includes the jumbogroup multiplex (JMX), which translates arrays of six analog or digitally derived mastergroup signals to and from line frequency; the L5 line bay, which provides the interface between the L5 line and the terminal equipment, including branching and blocking circuitry; the jumbogroup frequency supply, which provides highly stable signals from which JMX carriers are derived; the basic jumbogroup trunk bay, which processes the JMX baseband signal; and the transmission surveillance system which, in conjunction with the E2 status reporting and control system, allows the remote monitoring and trouble shooting of L5 line and main station equipment. L5 is a hardened system with main stations housed in self-contained, underground buildings. These buildings provide life support and auxiliary power equipment which allow main stations to operate under emergency status for as long as several weeks.     

A double-gate-type static-induction thyristor

A double-gate-type static-induction thyristor (DG-SIThy) with a high blocking voltage and a high current rating has been fabricated. In this paper, a basic operational mechanism, a fabrication procedure, and the electrical characteristics of the DG-SIThy are described. In the DG-SIThy, both electron injection and hole injection are controlled by signals applied to two gale regions so that the DG-SIThy is capable of higher frequency operations than a single-gate SIThy. In the DG-SIThy, described here, both a cathode and a gate (first gate) regions have been fabricated on one side of a semiconductor wafer and both an anode and gate.(second gate) regions on another side. For realizing the DG-SIThy with a high blocking voltage and a high current rating, we have tried attentively to form a p-n junction on one side of the wafer without influencing the p-n junction on the other side, and have developed a new counter-doping technique for epitaxial growth and an improved package structure for a compression-mounted device. The DG-SIThy fabricated with these techniques has shown a for-Ward blocking voltage of 1000 V, an average current rating of 100 A, and a forward voltage drop of 1.44 V at the rated anode current. A turn-on time of 0.95 its and a turn-off time of 0.48 µs have been observed at the rated anode current and at anode voltages of 650 and 550 V, respectively. As already speculated, the DG-SIThy shows a higher switching speed and a lower forward drop than the single-gate SIThy.     

Virtual impedance control for a regional dynamic voltage restorer

A dynamic voltage restorer (DVR) can be installed in a middle-voltage (MV) power grid, to concurrently protect a cluster of sensitive loads from voltage sags. To further improve its efficiency and reduce the difficulty in its implementation, a novel control strategy for operating such a DVR as a virtual impedance in series with sensitive loads is proposed in this paper. In addition to its usual function of compensating for voltage sags, such a DVR can also operate as a virtual inductance, to function as a fault current limiter (FCL) during a downstream fault, or a virtual capacitance, to function as a series compensator (SC) to compensate the voltage loss along the feeder line during heavy load. Based on a dual-loop control design, strategies for operating a DVR as a series virtual inductance and a virtual capacitance are proposed, and methods for tuning the parameter values and a stability analysis of the whole system are presented. The feasibility and effectiveness of the proposed method are verified by simulations using the PSCAD software, and experimental results obtained using a prototype DVR are presented.     

环Zn上椭圆曲线的密钥交换协议

设n=pq,p,q为奇素数,环Z_n上的椭圆曲线E_n(a,b)的SOM密钥交换协议与QV密钥交换协议均选取E_n(a,b)上的阶为M_n=lcm{#E_p(a,b),＃E_q(a,b)}的点G作为公钥(称G为基点),并且限定其对应的E_p(a,b)和E_q(a,b)均为循环群,这就限制了这两个协议只能选择一类特殊的椭圆曲线E_n(a,b)构作密钥交换协议.本文指出,E_p(a,b)和Eq(a,b)均为循环群这一限定是不必要的.本文给出了E_n(a,b)上存在阶为M_n的点G的一个充分必要条件,并给出一个例子,其中E_p(a,b)为循环群,E_q(a,b)为非循环群,且对应的E_n(a,b)上有阶为M_n的点G.同时,本文选取E_n(a,b)上阶为lcm{n₁,m₁}的点作为基点,这里n₁,m₁分别为E_p(a,b)和E_q(a,b)的最大循环子群的阶.这样,就能够选择更多的椭圆曲线E_n(a,b),用来构作密钥交换协议(包括将两方之间的密钥交换协议扩展到三方).     

Ultra-Low-Power Interface Chip for Autonomous Capacitive Sensor Systems

Traditionally, most of the sensor interfaces must be tailored towards a specific application. This approach results in a high recurrent design cost and time to market. On the other hand, generic sensor interface design reduces the costs and offers a handy solution for multisensor applications. This paper presents a generic sensor interface chip (GSIC), which can read out a broad range of capacitive sensors. It contains capacitance-to-voltage converters, a switched-capacitor amplifier, an analog-to-digital converter, oscillators, clock generation circuits and a reference circuit. The system combines a very low-power design with a smart energy management, which adapts the current consumption according to the accuracy and speed requirements of the application. The GSIC is used in a pressure and an acceleration monitoring system. The pressure monitoring system achieves a current drain of 2.3 muA for a 10-Hz sample frequency and an 8-bit accuracy. In the acceleration monitoring system, we measured a current of 3.3 muA for a sample frequency of 10 Hz and an accuracy of 9 bits     

Modeling the flow-level performance of hierarchical modulation in?OFDMA-based networks

Hierarchical Modulation (HM) is a means to enhance the spectral efficiency of a system by superposing, in terms of modulation, an additional stream for a given user with good radio conditions on a basic stream of a user with worse radio conditions. This, in turn, increases the throughput of the former user and hence the overall performance of the whole system. We consider, in this work, such a performance at the flow level, for a realistic dynamic setting where users come to the system and leave it after a finite duration corresponding, for instance, to the completion of a file transfer. We specifically model and quantify, both analytically and via simulations, the gain thus achieved and propose two extensions to the basic HM algorithm: a first one in which a user with bad radio conditions is also superposed on one with better radio conditions and a second one in which a user of one type is further superposed on a user of the same type as well.     

Impact of Channel Errors on Decentralized Detection Performance of Wireless Sensor Networks: A Study of Binary Modulations, Rayleigh-Fading and Nonfading Channels, and Fusion-Combiners

We provide new results on the performance of wireless sensor networks in which a number of identical sensor nodes transmit their binary decisions, regarding a binary hypothesis, to a fusion center (FC) by means of a modulation scheme. Each link between a sensor and the fusion center is modeled independent and identically distibuted (i.i.d.) either as slow Rayleigh-fading or as nonfading. The FC employs a counting rule (CR) or another combining scheme to make a final decision. Main results obtained are the following: 1) in slow fading, a) the correctness of using an average bit error rate of a link, averaged with respect to the fading distribution, for assessing the performance of a CR and b) with proper choice of threshold, on/off keying (OOK), in addition to energy saving, exhibits asymptotic (large number of sensors) performance comparable to that of FSK; and 2) for a large number of sensors, a) for slow fading and a counting rule, given a minimum sensor-to-fusion link SNR, we determine a minimum sensor decision quality, in order to achieve zero asymptotic errors and b) for Rayleigh-fading and nonfading channels and PSK (FSK) modulation, using a large deviation theory, we derive asymptotic error exponents of counting rule, maximal ratio (square law), and equal gain combiners.     

Secure group communications using key graphs

Many emerging network applications are based upon a group communications model. As a result, securing group communications, i.e., providing confidentiality, authenticity, and integrity of messages delivered between group members, will become a critical networking issue. We present, in this paper, a novel solution to the scalability problem of group/multicast key management. We formalize the notion of a secure group as a triple (U,K,R) where U denotes a set of users, K a set of keys held by the users, and R a user-key relation. We then introduce key graphs to specify secure groups. For a special class of key graphs, we present three strategies for securely distributing rekey messages after a join/leave and specify protocols for joining and leaving a secure group. The rekeying strategies and join/leave protocols are implemented in a prototype key server we have built. We present measurement results from experiments and discuss performance comparisons. We show that our group key management service, using any of the three rekeying strategies, is scalable to large groups with frequent joins and leaves. In particular, the average measured processing time per join/leave increases linearly with the logarithm of group size     

Set-based collision avoidance applications to robotic systems

A robotic system can consist of a single or multiple agents with a fixed or mobile base, with full or under-actuation, and possibly redundancy. Collision avoidance is a crucial task for any robotic system and is necessary to ensure safe operation. In this paper, we use a set-based approach to ensure collision avoidance as a high-priority task of a robotic system while simultaneously defining one or more tasks for the system to achieve. The set-based approach is highly generic and flexible, and we present theoretical results, practical implementation and experimental results of the approach applied to a redundant, fully actuated robot manipulator, a full-scale underactuated surface vessel and a multi-agent system of unicycles.     

A 0.25-μm CMOS 1.9-GHz PHS RF Transceiver With a 150-kHz Low-IF Architecture

We present a 1.9-GHz Personal Handy-phone System (PHS) transceiver, fully integrated and fabricated in 0.25-mum CMOS technology. The receiver is based on a 150-kHz low-IF architecture and meets the fast channel switching and DC-offset cancellation requirements of PHS. It includes a low-noise amplifier (LNA), a downconversion mixer, a complex filter, and a programmable gain amplifier. A fractional-N frequency synthesizer achieves seamless handover with a 25 mus channel switching time and a phase noise of -121 dBc/Hz at a 600-kHz offset frequency, with compliant ACS performance. The receiver provides -105 dBm sensitivity and 55 dBc ACS at a 600-kHz frequency offset. The transmitter is based on the direct modulation architecture and consists of an upconversion mixer and a pre-driver stage. The gain of the pre-driver is digitally controllable to suit any type of commercial power amplifier. The transmitter shows a 3% EVM and a 65 dBc ACPR at a 600-kHz offset frequency. The whole transceiver occupies 15.2 mm² and dissipates 70 mA in RX and 44 mA in TX, with a 2.8-V supply     

“信息论”课程教学方法改革的研究

"信息论"课程具有理论性强、内容抽象和知识点多等特点,本科学生学习容易产生畏惧心理。本文针对性地研究了一套教学改进方案:强化一条主线,营造一个场景;以阶段性目标为牵引,激发学生主动学习兴趣;同时,将全方位教育模式融入到"信息论"教学中,以适应不同学生的需求,平衡深度与广度之间的矛盾。经教学实践,学生学习兴趣普遍提高,教学效果良好。     

Compact and low-loss interleave filter employing lattice-form structure and silica-based waveguide

This paper describes a compact and practical interleave filter with uniform multi/demultiplexing properties and a wide operational wavelength range realized by using a lattice-form structure and a silica-based waveguide. In the design, we optimized the bandwidth by controlling the lattice stage number and the loss ripple in the spectrum. Moreover, we propose a novel coupler with a large fabrication tolerance, a new tandem configuration that provides uniform characteristics and low dispersion, a polarization dependence compensation method, and a folded configuration, which are effective in realizing a high-performance interleave filter. Based on the above techniques, we fabricated a 50-GHz channel spacing interleave filter by using planar-lightwave-circuit technologies and demonstrated that it performed well throughout the C-band, exhibiting a low insertion loss of about 2 dB, a low chromatic dispersion of within +/-20 ps/nm, a 1-dB passband width of over 34 GHz, and a 30-dB stopband width of over 25 GHz, which are sufficient for a 10-Gbps transmission system.     

Development of a standing style transfer system "ABLE" for disabled lower limbs

We have developed a standing style transfer system, or "ABLE," for a person with disabled legs. It allows travel in a standing posture even on uneven ground, a standing up motion from a chair, and allows the stairs. ABLE consists of three modules: a pair of telescopic crutches, a powered lower extremity orthosis, and a pair of mobile platforms. We present here the conceptual design of ABLE and the motion of each module. Cooperative operations using the three modules are discussed through simulations. The standing up motion from a chair and ascending the stairs, however, have problems with adaptability to the environment and safety, because it executes the movement that has till now relied on telescopic crutches. To solve these problems, we propose a new motion technique and compare it with the previous one. In this paper, some experimental results are also presented.     

A Binary-Weighted Switching and Reconfiguration-Based Programmable Gain Amplifier

In previous works, the authors reported on binary-weighted switching and reconfiguration techniques to design programmable gain amplifiers (PGAs) with a wide decibel (dB)-linear range, a small gain error, a wide 3-dB bandwidth, and high linearity. In this brief, two techniques are analyzed in more detail. Adopting the two techniques, a new low-voltage PGA version is proposed that offers a precise and process/temperature-insensitive gain and achieves a double dB-linear range with a small gain error while maintaining the same chip size, as compared with those of previous designs. Implemented in 0.18-mum CMOS, from the measurements, the proposed PGA shows a dB-linear gain range of 42 dB (-21 to 21 dB) with a gain error of less than plusmn 0.54 dB, a maximum input-referred third-order intercept point (IIP3) of 14 dBm, and a 3-dB bandwidth of 60 MHz at the maximum gain while consuming only 2.1 mA from a 1.5-V supply.     

Human cooperative wheelchair for haptic interaction based on dual compliance control

A human and a robot will carry out a task which is not attainable by themselves. In particular, a human recognizes environment and plans his trajectory without collision with obstacles. On the other hand, a robot generates a controlled force more than a human. In this paper, the best combination of human ability and robot capacity is considered. Based on force commands from a human, a robot supports it A reaction torque observer is implemented in a robot to observe an environmental disturbance. Environmental disturbance is classified into translational and rotational direction modes. As a result, adaptive force control in each mode is attained. Dual compliance control is applied to a wheelchair. A wheelchair that has the abilities of power-assist and relaxation of contact force is developed in this paper. As a result, operationality and stability are improved. The numerical and experimental results show the viability of the proposed method.     

Laser tuners and wavelength-sensitive detectors based on absorbersin standing waves

We propose a new method for making laser tuners, and wavelength-sensitive or tunable detectors, that is based on absorbers in standing waves. Because the method does not rely on mechanical movement or changes in refractive index, it may offer high-speed tunable devices whose range is not constrained by limits on the size of refractive index changes. The devices can be made either in a longitudinal form by back reflection, or in a transverse form by interfering beams at an angle on a surface. We give theoretical models for these structures, and illustrate the concepts with various specific device designs. These include a narrow band detector based on transverse gratings, a simple wavelength sensitive longitudinal structure with a single absorber, and a two-absorber longitudinal structure capable of many functions, including a narrow band detector, a two wavelength detector, a wavelength measuring detector, a continuously variable laser tuner, and a laser phase controller. These devices can all be made using layered semiconductor growth and lithography, and are particularly suited to quantum wells. The devices are applicable to wavelength division multiplexing and switching, and to sensors and spectroscopy     

A 2-V CMOS cellular transceiver front-end

This work presents the design and implementation of a 2-V cellular transceiver front-end in a standard 0.25-μm CMOS technology. The prototype integrates a low-IF receiver (low noise amplifier, I/Q mixers, and VGAs) and a direct-upconversion transmitter (I/Q mixers and pre-amplifier) on a single die together with a complete phase-locked loop, including a 64/79 prescaler, a fully integrated loop filter, and a quadrature voltage controlled oscillator with on-chip inductors. Design trade-offs have been made over the boundaries of the different building blocks to optimize the overall system performance. All building blocks feature circuit topologies that enable comfortable operation at low voltage. As a result, the IC operates from a power supply of only 2 V, while consuming 191 mW in receiver (RX) mode and 160 mW in transmitter (TX) mode. To build a complete transceiver system for 1,8-GHz cellular communication, only an antenna, an antenna filter, a power amplifier, and a digital baseband chip must be added to the analog front-end. This work shows the potential of achieving the analog performance required for the class I/II DCS-1800 cellular system in a standard 0.25-μm CMOS technology, without tuning or trimming