An Immitance Based Tool for Modelling Passive One-Port Devices by Means of Darlington Equivalents

An immitance-based method is presented to model measured orcomputed data, obtained from a “passive one-port physical device” by means of its Darlington equivalent. In other words, the given data ismodelled as a lossless two port terminated in a unit resistor. The basis of the new modelling tool rests on the numerical decomposition of the given immitance data into its Foster and minimum parts. Therefore, the proposed technique does not require any choice for the circuit topology to build the model. Rather, the optimum circuit topology that characterises thegiven data is the natural consequence of the modelling process proposed in this paper. A main algorithm is presented to construct the model from the given data. It is expected that the proposed modelling tool will findpractical applications in the behaviour characterisation, simulation, and design of high speed/high frequency analog/digital mobile communication sub-systems manufactured on VLSI chips. An antenna-modelling example is included to systematically exhibit the implementation of the modelling technique.     

Recursive Halfband-Filters

The paper describes the properties and the design of recursive halfband-filters.The two possibilities of being complementary are introduced. The lowpass with the transfer function H_Lp(z)and the corresponding highpass, described by H_Hp(z) = H_Lp(-z)can either be strictly complementary or power complementary. According to the respective symmetry, the impulse responses, transfer functions and frequency responses possess certain characteristic properties, which are described in section 2. It turns out that these resulting symmetries of the frequency response reduce the number of the choosable design parameters. We can only prescribe the cutoff frequency and the tolerated deviation either for the passband or the stopband.

In the third section we treat the design of halfband-filters with approximately linear phase. By coupling an appropriately designed allpass of even degree n_A with a delay of order m=n_A±1 we obtain the desired solution by solving a corresponding approximation problem for the phase of the allpass. The resulting lowpass and highpass are strictly as well as power complementary!The kind of approximation will be done in the sense of maximal flatness, where a closed form solution exists [8], or in the sense of Chebychev, where the solution is obtained iteratively [13]. The design of systems with minimum phase is presented in section 4. The resulting lowpass and highpass are power complementary. Closed form solutions yield Butterworthand Cauer filters, if a maximal flat or a Chebychev approximation is desired. In all cases a fixed relation exists between the passband frequency Ω_P and the tolerated deviation δ_P in the passband when the degree n has been chosen.     

Modelling of 2-D Real Rational Reactance Functions. A Parameter-Based Approach

Lossless (reactive) one-ports are of great importance in the field of linear network theory. This statement also applies for the two-dimensional (2-D) case, where the design of corresponding impedance or admittance functions is a much more challenging task. In this paper a model for 2-D real rational reactance functions is introduced which is a rational function in p₁ and p₂ where the coefficients are functions of parameters. The following features make it best suited for the computer based design of lossless one-ports, namely no dependencies between the real valued parameters, coverage of the whole class of 2-D real rational reactance functions, and the coefficients are polynomials in the parameters. The synthesis of 2-D lossless networks and skew symmetric matrices form the basis of our considerations.     

Flexible Digital Receiver Architecture with Optimized Components

Future wireless communication systems require increased flexibility, lower power consumption, smaller size and decreasing costs for the terminals and therewith for the components. By replacing analogue by digital signal processing the degree of integration and the flexibility of a terminal with respect to multi-mode capability can be improved.In a highly integrated implementation the most critical components are the A/D-converter and the digital filter stages due to high speed and low power requirements. In this contribution a novel concept for a flexible, digital receiver with highly optimized components will be presented. The concept is based on down-conversion of the broadband receive signal to a low intermediate frequency. The main modules of the receiver are a properly designed ΔΣ-modulator for A/D-conversion, and novel digital filtering stages. It will be demonstrated, that the use of cascaded low-order wave digital lattice filters results in a number of advantages and makes a very efficient realization in VLSI-technology feasible.     

Optimum path planning using convex hull and local search heuristic algorithms

Whether in improving quality or productivity the impact of mechatronic systems such as robots in industry is unquestionable. One aspect of interest in robotics is planning the optimum path for a mobile robot or the optimum trajectory for link movements of a stationary robot in order to increase their efficiency. However, for a given set of points complete enumeration of all the possible paths to establish an optimal one is not feasible as the search space increases exponentially (explodes combinatorially) as the number of points increases. This problem, traditionally known as the “Traveling Salesman Problem” (TSP) has attracted a great deal of attention for a long time. Proven enumerative techniques such as “nearest neighbour algorithm”, “branch and bound”, “cutting planes”, and “dynamic programming” as well as approximation methods such as “tabu search”, “greedy algorithm”, “simulated annealing” and “genetic algorithm”, have had only a limited success in solving this problem. Recently “convex hull”, a minimum area and perimeter shape, has been used as an initial sub-tour along with enumerative techniques such as minimising insertion costs to solve the TSP problem. We present a system which uses heuristic rules to augment the convex hull initial sub-tour created by the Graham scan algorithm. The system is able to provide a solution in a polynomial time.     

Simplified Design Approach of Reliable Transparent Optical Networks

Transparent optical networks will play an important role in the near future. The aim of this work is to provide a simplified design approach how to utilize the new feature “optical transparency” in WDM based optical networks. Therefore optical nodes and transmission links are characterized and a set of simplified parameters and rules describing the transparent sub-networks is presented. In this way the complexity originating from physical constraints is reduced substantially, simplifying the management of these optical networks and the physical parameters which will be implemented in the routing protocols. This contribution is a compendium of results of the BMBF KomNet project in the field of optical networks optimisation.     

1994 America on display… American LCDs playing catch-up

With each sensational new development, the real life race for American dominance over Japan in next-generation flat panel displays is looking progressively more like a rough draft of a techno-thriller (with the likelihood of getting even rougher). The real life drama that is unfolding is not only exciting, it often seems less believable than fiction. In this episode of “America On Display,” we'll try to sort through what some of the leading characters have been up to lately, who they're working with (or against), and what the U.S. government and various “cooperative” catalysts are contributing to the chain of chaotic events.     

A two-dimensional integrated device/circuit numerical model for GaAs DCFL gate simulation

A two-dimensional integrated numerical device/circuit model for GaAs/MESFET DCFL gate simulation is presented. It is different from previous publications in that (a) transient carrier transport equations of the FETs are calculated with consideration for the interaction between interconnected FETs in a circuit, (b) the numerical calculations are carried out for the coupled equations to provide accuracy and (c) with the new algorithm used, the numerical calculation can be carried out with high efficiency. A “dynamic method” and a “single gate method” have been developed to simulate the steady state transfer and ring oscillator transient characteristics, respectively, which have proved to be much more efficient than the previously used methods. Based on the model, a gate level two-dimensional numerical simulator, LADES2G, has been developed and successfully applied to GaAs DCFL circuit design.     

Evaluation of D.U.V positive resist Shipley XP9493 for E-BEAM lithography

The purpose of this investigation is to demonstrate the capability of using D.U.V resist XP9493 from Shipley for E-BEAM applications. The mains parameters which have been checked are, a high resist sensitivity to get a lower exposure time coupled with a sub micron resolution and a sufficient process window. The softbake value which optimizes the dose (best throughput) to stability (process window) ratio is 100°C/60s. The Post Exposure Bake variation shows the Dose to clear (D0) to decrease when increasing the temperature, however “resist loss” becomes a problem over 125°C. The contrast is adequate for a E-beam application (γ9). The linearity measured on contacts is good in the range of 0.8μm to 2.0μm. The profile is adequate (i.e vertical) in a 1.4μm thick resist for a dose of 6μC/cm²; a higher dose would generate “uncontrolled size of contact”, a lower dose could generate “closed contacts”. The throughput earning should be 30% for the referenced implantation levels.

The resist XP9493 from SHIPLEY seems to be a good candidate for Implantation and Contact levels production application. This is the second Deep-UV positive resist tested from Shipley, on the AEBLE 150s (column 20kV), the first was the XP9402. The to-date results are the most promising ever obtained at ES2 with a positive tone resist for E-Beam applications.     

Adhoc-like routing in wired networks with genetic algorithms

Routing of packets in networks requires that a path be selected either dynamically while the packets are being forwarded, or statically (in advance) as in source routing from a source node to a destination. Quality of service (QoS) driven routing has been proposed using a protocol called the “Cognitive Packet Network” (CPN) which dynamically selects paths through a store and forward packet network so as to provide best effort QoS to route peer-to-peer connections. CPN operates very much as an adhoc protocol within a wired setting, and uses smart packets to select routes based on QoS requirements. We extend the path discovery process in CPN to include a genetic algorithm which can help discover new paths that may not have been discovered by smart packets. We describe how possible routes can “evolve” from prior knowledge, and then be selected based on “fitness” with respect to QoS. We detail the design of the algorithm and of its implementation, and report on resulting QoS measurements.     

Profiling Voids Embedded in a Slab by a Non-Linear Model

In this paper, by applying a non linear model for the electromagnetic inverse scattering, a technique for the dielectric profiling of a planarly layered medium is investigated and applied to void localization and diagnostics inside a homogeneous lossless slab (one-dimensional geometry). Data are collected under plane wave multifrequency normal incidence. Suitable finite dimensional representations for the unknown functions are introduced and their influence on the model is discussed. The resulting functional equation is solved by the method of weighted residuals and the solution algorithm amounts to minimizing a non quadratic function, where particular attention is devoted to reduce the occurrence of local minima. Finally, the inversion algorithm is validated by applications to both simulated and experimental data.     

A “Group-Division Multiple Access” framework for channel access to multiple destinations

We consider the problem of media-access control in multiple-cell networks, such as ad hoc networks in which clusterheads take on a role similar to base stations. We assume that a single channel is used by all cells, and that the user populations that transmit to different base stations overlap, causing interference in the neighboring cells. Starting with a two-destination network, we introduce the “Group-Division Multiple Access” (GDMA) concept, according to which different groups of users multiplex their transmission in time while being free to use the protocol of their choice within their own group. We show that use of GDMA provides higher stable throughput than a “free-running” scheme (under which all slots are available to all users) when the First-Come First-Serve collision–resolution algorithm is used as the channel-access protocol, and we show how performance depends on the degree of overlap of communication and interference regions. Finally, we show that this approach can be applied to larger cellular-like networks as well.     

Synthetic organisms and self-designing systems

This paper examines the need for complex, adaptive solutions to certain types of complex problems typified by the Strategic Defense System and NASA's Space Station and Mars Rover. Since natural systems have evolved with capabilities of intelligent behavior in complex, dynamic situations, it is proposed that biological principles be identified and abstracted for application to certain problems now facing industry, defense, and space exploration. Two classes of artificial neural networks are presented — a nonadaptive network used as a genetically determined “retina,” and a frequency-coded network used as an adaptive “brain.” The role of a specific environment coupled with a system of artificial neural networks having simulated sensors and effectors is seen as an ecosystem. Evolution of synthetic organisms within this ecosystem provides a powerful optimization methodology for creating intelligent systems able to function successfully in any desired environment. A complex software system involving a simulation of an environment and a program designed to cope with that environment are presented. Reliance on adaptive systems, as found in nature, is only part of the proposed answer, though an essential one. The second part of the proposed method makes use of an additional biological metaphor—that of natural selection—to solve the dynamic optimization problems every intelligent system eventually faces. A third area of concern in developing an adaptive, intelligent system is that of real-time computing. It is recognized that many of the problems now being explored in this area have their parallels in biological organisms, and many of the performance issues facing artificial neural networks may find resolution in the methodology of real-time computing.     

E-beam lithography by using an STEM with integrated laser interferometer stage

A high resolution e-beam lithography instrument has been developed consisting of an STEM (Zeiss EM 910) equipped with a laser interferometer stage, an electrostatic beam blanker, and “ELPHY Plus”. This new system now allows to perform high voltage e-beam lithography on small samples with highest resolution and precise stitching.     

PLAN-IT: Scheduling assistant for solar system exploration

At the Jet Propulsion Laboratory (JPL), the scheduling of spacecraft activities is a complex endeavor for which streamlining is always being sought. Using the Comet Rendezvous Asteroid Flyby mission (CRAF—proposed for 1993 launch) as a development base, PLAN-IT (a frame-based expert scheduling system shell) has been adapted to assist in one phase of schedule generation. PLAN-IT CRAF automatic scheduling routines attempt to return a “good-cut” schedule which can be adjusted by an expert with time-saving graphic manipulation tools. Work to date has led to a “GO” decision on technical factors for online capability development.     

Beyond transborder data flow

The unique nature of information gives rise to troublesome questions regarding traditional economic theory, ownership rights and the role of the government. Today, one of the main focusses of international information policy concerns the flow of data across national boundaries. One finds a disappointing outline of a new spirit of “double standards” in the U.S. information policy. The earlier spirit calling for unrestricted flow of information across international boundaries is being replaced by a form of “America first” philosophy.     

Probabilistic reliable multicast in ad hoc networks

When striving for reliability, multicast protocols are most commonly designed as deterministic solutions. Such an approach seems to make the reasoning about reliability guarantees (traditionally, binary, “all-or-nothing”-like) in the face of packet losses and/or node crashes. It is however precisely this determinism that tends to become a limiting factor when aiming at both reliability and scalability, particularly in highly dynamic networks, e.g., ad hoc networks. Gossip-based multicast protocols appear to be a viable path towards providing multicast reliability guarantees. Such protocols embrace the non-deterministic nature of ad hoc networks, providing analytically predictable probabilistic reliability guarantees at a reasonable overhead.

This paper presents the Route Driven Gossip (RDG) protocol, a gossip-based multicast protocol designed precisely to meet a more practical specification of probabilistic reliability in ad hoc networks. Our RDG protocol can be deployed on any basic on-demand routing protocol, achieving a high level of reliability without relying on any inherent multicast primitive. We illustrate our RDG protocol by layering it on top of the “bare” Dynamic Source Routing protocol, and convey our claims of reliability and scalability through both analysis and simulation.     

From OPIMA to MPEG IPMP-X: A standard''s history across R&D projects

This paper describes the work performed by a number of companies and universities who have been working as a consortium under the umbrella of the European Union Framework Programme 5 (FP5), Information Society Technologies (IST) research program, in order to provide a set of Digital Rights Management (DRM) technologies and architectures, aiming at helping to reduce the copyright circumvention risks, that have been threatening the music and film industries in their transition from the “analogue” to “digital” age. The paper starts by addressing some of the earlier standardization efforts in the DRM arena, namely, Open Platform Initiative for Multimedia Access (OPIMA). One of the described FP5 IST projects, Open Components for Controlled Access to Multimedia Material (OCCAMM), has developed the OPIMA vision. The paper addresses also the Motion Pictures Expert Group—MPEG DRM work, starting from the MPEG Intellectual Propriety Management and Protection—IPMP “Hooks”, towards the MPEG IPMP Extensions, which has originated the first DRM-related standard (MPEG-4 Part 13, called IPMP Extensions or IPMP-X) ever released by ISO up to the present days.² The paper clarifies how the FP5 IST project MPEG Open Security for Embedded Systems (MOSES), has extended the OPIMA interfaces and architecture to achieve compliance with the MPEG IPMP-X standard, and how it has contributed to the achievement of “consensus” and to the specification, implementation (Reference Software) and validation (Conformance Testing) of the MPEG IPMP-X standard.     

A new technique in the global reliability of cyclic communications network

The global reliability of a communications network is the probability that given any pair of nodes, there exists a viable path between them. A characterization of connectivity, for a given class of networks, can enable one to find this reliability. Such a characterization is described for a useful class of undirected networks called “daisy-chained” or “braided” networks. This leads to a new method of quickly computing the global reliability of these networks. Asymptotic behavior in terms of component reliability is related to geometric properties of the given graph. Generalization of the technique is discussed.