bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of microwave circuits and laser structures including PML by means of FIT
Authors: Hebermehl G. , Schefter J. , Schlundt R. , Tischler Th. , Zscheile H. , Heinrich W.
Published: April 2010

Abstract. Field-oriented methods which describe the physical properties of microwave circuits and optical structures are an indispensable tool to avoid costly and time-consuming redesign cycles. Commonly the electromagnetic characteristics of the structures are described by the scattering matrix which is extracted from the orthogonal decomposition of the electric field. The electric field is the solution of an eigenvalue and a boundary value problem for Maxwell’s equations in the frequency domain. We discretize the equations with staggered orthogonal grids using the Finite Integration Technique (FIT). Maxwellian grid equations are formulated for staggered nonequidistant rectangular grids and for tetrahedral nets with corresponding dual Voronoi cells. The interesting modes of smallest attenuation are found solving a sequence of eigenvalue problems of modified matrices. To reduce the execution time for high-dimensional problems a coarse and a fine grid is used. The calculations are carried out, using two levels of parallelization. The discretized boundary value problem, a large-scale system of linear algebraic equations with different right-hand sides, is solved by a block Krylov subspace method with various preconditioning techniques. Special attention is paid to the Perfectly Matched Layer boundary condition (PML) which causes non physical modes and a significantly increased number of iterations in the iterative methods.
Link budget comparison of different mobile communication systems based on EIRP and EISL
Authors: Fischer G. , Pivit F. , Wiebeck W.
Published: April 2010

Abstract. The metric EISL (Equivalent Isotropic Sensitivity Level) describing the effective sensitivity level usable at the air interface of a mobile or a basestation is used to compare mobile communication systems either based on time division or code division multiple access in terms of coverage and emission characteristics. It turns out that systems that organize the multiple access by different codes rather than different timeslots run at less emission and offer greater coverage.
A fast vectorial network analyser for frequencies up to 4 GHz
Authors: Schulte B. , Musch T. , Schiek B.
Published: April 2010

Abstract. A fast four channel network analyser is introduced to measure S-parameters in a frequency range from 10MHz to 4GHz. The measurement period of this kind of network analyser is short in comparison with a conventional one, which becomes possible by using highly linear analogue frequency ramps, realized with fractional divider phase locked loop circuits. The settling time for the discrete frequency points, which is typical for a conventional network analyser, is nearly eliminated by the use of frequency ramps. To achieve the necessary bandwidth of 4 GHz in the baseband, a heterodyne principle is applied. A VCO-signal from 5 to 9 GHz is down converted to the baseband with a fixed frequency generator of 9 GHz. The structure of the following network analyser is similar to the structure of a conventional four channel network analyser and therefore all known calibration techniques are suited for the fast network analyser. The intermediate frequency, which is necessary for the evaluation, carries the required information. However a special analysis technique is necessary. This technique is based on two Fourier transformations.
Application driven evaluation of network on chip architectures forcation parallel signal processing
Authors: Neeb C. , Thul M. J. , Wehn N.
Published: April 2010

Abstract. Today’s signal processing applications exhibit steadily increasing throughput requirements which can be achieved by parallel architectures. However, efficient communication is mandatory to fully exploit their parallelism. Turbo-Codes as an instance of highly efficient forward-error correction codes are a very good application to demonstrate the communication complexity in parallel architectures. We present a network-on-chip approach to derive an optimal communication architecture for a parallel Turbo-Decoder system. The performance of such a system significantly depends on the efficiency of the underlying interleaver network to distribute data among the parallel units. We focus on the strictly orthogonal n-dimensional mesh, torus and k-ary-n cube networks comparing deterministic dimension-order and partially adaptive negative- first and planar-adaptive routing algorithms. For each network topology and routing algorithm, input- and output-queued packet switching schemes are compared on the architectural level. The evaluation of candidate network architectures is based on performance measures and implementation cost to allow a fair trade-off.
Eine verlustleistungsoptimierte Dezimator-Architektur für kaskadierte Sigma-Delta Analog-Digital Umsetzer
Authors: Becker M. , Heiber K. , Ortmanns M. , Manoli Y.
Published: April 2010

Abstract. Dieser Beitrag stellt einen neuartigen Ansatz einer leistungsfähigen Dezimator-Architektur f¨ur kaskadierte Sigma-Delta Modulatoren vor. Die Besonderheit der dargestellten Struktur ist die Integration der Rekombinationslogik kaskadierter Modulatoren und der Korrektur des Verstärkungsfehlers zeitkontinuierlicher (continuous time, CT) Modulatoren in die erste Stufe des Dezimators. Der Entwurf einer passenden Filtertopologie wird abgeleitet, analysiert und durch Simulationen verifiziert. Die vorgeschlagene Struktur wird mit einer herk¨ommlichen Implementierung verglichen. Das Ergebnis dieses Vergleiches ist eine Verbesserung der Effizienz um Dekaden.
Power estimation on functional level for programmable processors
Authors: Schneider M. , Blume H. , Noll T. G.
Published: April 2010

Abstract. In diesem Beitrag werden verschiedene Ansätze zur Verlustleistungsschätzung von programmierbaren Prozessoren vorgestellt und bezüglich ihrer Übertragbarkeit auf moderne Prozessor-Architekturen wie beispielsweise Very Long Instruction Word (VLIW)-Architekturen bewertet. Besonderes Augenmerk liegt hierbei auf dem Konzept der sogenannten Functional-Level Power Analysis (FLPA). Dieser Ansatz basiert auf der Einteilung der Prozessor-Architektur in funktionale Blöcke wie beispielsweise Processing-Unit, Clock-Netzwerk, interner Speicher und andere. Die Verlustleistungsaufnahme dieser Bl¨ocke wird parameterabhängig durch arithmetische Modellfunktionen beschrieben. Durch automatisierte Analyse von Assemblercodes des zu schätzenden Systems mittels eines Parsers können die Eingangsparameter wie beispielsweise der erzielte Parallelitätsgrad oder die Art des Speicherzugriffs gewonnen werden. Dieser Ansatz wird am Beispiel zweier moderner digitaler Signalprozessoren durch eine Vielzahl von Basis-Algorithmen der digitalen Signalverarbeitung evaluiert. Die ermittelten Schätzwerte für die einzelnen Algorithmen werden dabei mit physikalisch gemessenen Werten verglichen. Es ergibt sich ein sehr kleiner maximaler Schätzfehler von 3%. In this contribution different approaches for power estimation for programmable processors are presented and evaluated concerning their capability to be applied to modern digital signal processor architectures like e.g. Very Long InstructionWord (VLIW) -architectures. Special emphasis will be laid on the concept of so-called Functional-Level Power Analysis (FLPA). This approach is based on the separation of the processor architecture into functional blocks like e.g. processing unit, clock network, internal memory and others. The power consumption of these blocks is described by parameter dependent arithmetic model functions. By application of a parser based automized analysis of assembler codes of the systems to be estimated the input parameters of the Correspondence to: H. Blume (blume@eecs.rwth-aachen.de) arithmetic functions like e.g. the achieved degree of parallelism or the kind and number of memory accesses can be computed. This approach is exemplarily demonstrated and evaluated applying two modern digital signal processors and a variety of basic algorithms of digital signal processing. The resulting estimation values for the inspected algorithms are compared to physically measured values. A resulting maximum estimation error of 3% is achieved.
Theory of circuit block switch-off
Authors: Henzler S. , Berthold J. , Georgakos G. , Schmitt-Landsiedel D.
Published: April 2010

Abstract. Switching-off unused circuit blocks is a promising approach to supress static leakage currents in ultra deep sub-micron CMOS digital systems. Basic performance parameters of Circuit Block Switch-Off (CBSO) schemes are defined and their dependence on basic circuit parameters is estimated. Therefore the design trade-off between strong leakage suppression in idle mode and adequate dynamic performance in active mode can be supported by simple analytic investigations. Additionally, a guideline for the estimation of the minimum time for which a block deactivation is useful is derived.
"easyMine" – realistic and systematic mine detection simulation tooltion
Authors: Böttger U. , Beier K. , Biering B. , Müller C. , Peichl M. , Spyra W.
Published: April 2010

Abstract. Mine detection is to date mainly performed with metal detectors, although new methods for UXO detection are explored worldwide. The main problem for the mine detection to date is, that there exist some ideas of which sensor combinations could yield a high score, but until now there is no systematic analysis of mine detection methods together with realistic environmental conditions to conclude on a physically and technically optimized sensor combination. This gap will be removed by a project “easyMine" (Realistic and systematic Mine Detection Simulation Tool) which will result in a simulation tool for optimizing land mine detection in a realistic mine field. The project idea for this software tool is presented, that will simulate the closed chain of mine detection, including the mine in its natural environment, the sensor, the evaluation and application of the measurements by an user. The tool will be modularly designed. Each chain link will be an independent, exchangeable sub- module and will describe a stand alone part of the whole mine detection procedure. The advantage of the tool will be the evaluation of very different kinds of sensor combinations in relation of their real potential for mine detection. Three detection methods (metal detector, GPR and imaging IR-radiometry) will be explained to be introduced into the easyMine software tool in a first step. An actual example for land mine detection problem will be presented and approaches for solutions with easyMine will be shown.
GPS TEC and ITEC from digisonde data compared with NEQUICK model
Authors: Jodogne J.-C. , Nebdi H. , Warnant R.
Published: April 2010

Abstract. At the Dourbes station, a digisonde 256 is colocated with a Turbo Rogue GPS receiver. Real time processing of the digisonde data gives the electron density profile and the ITEC value (SAO file) for each sounding. The GPS receiver produces data that are treated at the Royal Observatory in order to extract a vertical TEC. Running the wellknown NeQuick ionospheric model allows to compute vertical TEC values. Comparisons of the results obtained in 1996 and 2001 by these different approaches are shown.
A wonderful laboratory and a great researcher
Authors: Sheikh N. M.
Published: April 2010

Abstract. It was great to be associated with Prof. Dr. Karl Rawer. He devoted his life to make use of the wonderful laboratory of Nature, the Ionosphere. Through acquisition of the experimental data from AEROS satellites and embedding it with data from ground stations, it was possible to achieve a better empirical model, the International Reference Ionosphere. Prof. Dr. Karl Rawer has been as dynamic as the Ionosphere. His vision about the ionospheric data is exceptional and has helped the scientific and engineering community to make use of his vision in advancing the dimensions of empirical modelling. As a human being, Prof. Dr. Karl Rawer has all the traits of an angel from Heaven. In short he developed a large team of researchers forming a blooming tree from the parent node. Ionosphere still plays an important role in over the horizon HF Radar and GPs satellite data reduction.
New Standards for the Validation of EMC Test Sites particularly above 1 GHz
Authors: Battermann S. , Trautnitz F. W. , Garbe H.
Published: April 2010

Abstract. Standards for the validation of alternative test sites with conducting groundplane exist for the frequency range 30-1000 MHz since the end of the eighties. Recently the procedure for fully anechoic rooms (FAR) has been included in CISPR 16 after more than 10 years intensive discussion in standards committees (CENELEC, 2002; CISPR, 2004). But there are no standards available for the validation of alternative test sites above 1 GHz. The responsible working group (WG1) in CISPR/A has drawn up the 7th common draft (CD). A CDV will be published in spring 2005. The German standards committee VDE AK 767.4.1 participates in the drafting of the standard. All suggested measurement procedures proposed in the last CDs have been investigated by measurements and theoretical analysis. This contribution describes the basic ideas and problems of the validation procedure of the test site. Furthermore measurement results and numerical calculations will be presented especially for the use of omni-directional antennas.
Shielding properties of a conducting bar calculated with a boundary integral method
Authors: Fichte L. O. , Lange S. , Steinmetz Th. , Clemens M.
Published: April 2010

Abstract. A plane rectangular bar of conducting and permeable material is placed in an external low-frequency magnetic field. The shielding properties of this object are investigated by solving the given plane eddy current problem for the vector potential with the boundary integral equation method. The vector potential inside the rectangle is governed by Helmholtz' equation, which in our case is solved by separation. The solution is inserted into the remaining boundary integral equation for the exterior vector potential in the domain surrounding the bar. By expressing its logarithmic kernel as a Fourier integral the overall solution inside and outside the bar is calculated using analytical means only.
Schirmwirkung von Hochfrequenz (HF)-Schutzkleidung: Untersuchung verschiedener Konstruktionsmerkmale
Authors: Arps V. , Scheibe K.
Published: April 2010

Abstract. Die Messverfahren zur Bestimmung der Schutzwirkung von HF-Schutzkleidung sind in der Norm DIN 32780-100 festgelegt. Entsprechend diesen Anforderungen wird die elektrische und magnetische Schirmdämpfung bestimmt und daraus als Maß für die Schutzwirkung die elektromagnetische Schirmdämpfung berechnet. Diese ist eine der SAR vergleichbare Größe. In diesem Beitrag werden die Einflüsse verschiedener Konstruktionsmerkmale von HF-Schutzanzügen auf die elektromagnetische Schirmdämpfung untersucht. Zu diesen gehören die nach MIL STD 285 vermessene elektrische Schirmdämpfung der verwendeten Gewebe. Weiter werden verschiedene Teilbereiche der HF-Schutzkleidung auf ihre Schutzwirkung untersucht. Der Schwerpunkt liegt hierbei auf der Fragestellung inwieweit Verschlüsse, Reißverschlüsse oder leitfähiges Klettband, die Schutzwirkung beeinträchtigen. Zu diesem Zweck werden zwei Schutzanzüge unterschiedlicher Konstruktion vergleichend vermessen. Es handelt sich dabei um einen bereits im Handel befindlichen und entsprechend der Norm zertifizierten Anzug und einen neuen Prototyp, welcher nach verschiedenen Gesichtspunkten optimiert wurde. Schwachstellen der Konstruktion werden herausgearbeitet und Ansatzpunkte für weitere Verbesserungen erarbeitet. The measuring methods for determining the shielding effectiveness of radiofrequency (RF)-protective clothing are defined in German Standard DIN 32780-100. According to this standard, both the electric and the magnetic shielding effectiveness are measured in order to calculate the electromagnetic shielding effectiveness. The electromagnetic shielding effectiveness is an adequate quality criterion for the degree of protection and also compares well with the Specific Absorption Rate (SAR). In this article, the impact of different design features on the electromagnetic shielding effectiveness is analyzed. The electric shielding effectiveness of the used shielding materials is measured according to MIL STD 285 and thereupon taken into account. Moreover, different parts of the RF-Protective Clothing are analyzed in terms of shielding properties. The main focus is on the question to what extent seams and zippers impair the shielding properties. Therefore, two RF-protective suits with different design features are tested and compared. One of the tested suits is accredited according to German Standard and is already on the market. The other one is an optimized prototype. Weak spots concerning design features and starting points for further optimization are worked out.
Employing beam-forming for estimating the direction of arrival in a multi-path propagation environment
Authors: Bresch M. , Shi J. , Kokozinski R.
Published: April 2010

Abstract. Due to recent researches on traffic accidents with vulnerable road users (VRUs), several measures revealed a great opportunity of reduction. However, all measures applied so far failed to reduce the number of traffic accidents if there is no line-of-sight. Therefore, a transponder signal is utilized to make the VRU visible. The motor vehicle carries a mobile receiver for VRU detection and location. The receiver employs digital beam-forming for estimating the direction of arrival (DOA) with an antenna array for RF ISM band. A sequence of DOA estimations is used for location and motion estimation purposes.
Optimally Accurate Second-Order Time-Domain Finite-Difference Scheme for Acoustic, Electromagnetic, and Elastic Wave Modeling
Authors: Bommaraju C. , Marklein R. , Chinta P. K.
Published: April 2010

Abstract. Numerical methods are extremely useful in solving real-life problems with complex materials and geometries. However, numerical methods in the time domain suffer from artificial numerical dispersion. Standard numerical techniques which are second-order in space and time, like the conventional Finite Difference 3-point (FD3) method, Finite-Difference Time-Domain (FDTD) method, and Finite Integration Technique (FIT) provide estimates of the error of discretized numerical operators rather than the error of the numerical solutions computed using these operators. Here optimally accurate time-domain FD operators which are second-order in time as well as in space are derived. Optimal accuracy means the greatest attainable accuracy for a particular type of scheme, e.g., second-order FD, for some particular grid spacing. The modified operators lead to an implicit scheme. Using the first order Born approximation, this implicit scheme is transformed into a two step explicit scheme, namely predictor-corrector scheme. The stability condition (maximum time step for a given spatial grid interval) for the various modified schemes is roughly equal to that for the corresponding conventional scheme. The modified FD scheme (FDM) attains reduction of numerical dispersion almost by a factor of 40 in 1-D case, compared to the FD3, FDTD, and FIT. The CPU time for the FDM scheme is twice of that required by the FD3 method. The simulated synthetic data for a 2-D P-SV (elastodynamics) problem computed using the modified scheme are 30 times more accurate than synthetics computed using a conventional scheme, at a cost of only 3.5 times as much CPU time. The FDM is of particular interest in the modeling of large scale (spatial dimension is more or equal to one thousand wave lengths or observation time interval is very high compared to reference time step) wave propagation and scattering problems, for instance, in ultrasonic antenna and synthetic scattering data modeling for Non-Destructive Testing (NDT) applications, where other standard numerical methods fail due to numerical dispersion effects. The possibility of extending this method to staggered grid approach is also discussed. The numerical FD3, FDTD, FIT, and FDM results are compared against analytical solutions.
Combining the multilevel fast multipole method with the uniform geometrical theory of diffraction
Authors: Tzoulis A. , Eibert T. F.
Published: April 2010

Abstract. The presence of arbitrarily shaped and electrically large objects in the same environment leads to hybridization of the Method of Moments (MoM) with the Uniform Geometrical Theory of Diffraction (UTD). The computation and memory complexity of the MoM solution is improved with the Multilevel Fast Multipole Method (MLFMM). By expanding the k-space integrals in spherical harmonics, further considerable amount of memory can be saved without compromising accuracy and numerical speed. However, until now MoM-UTD hybrid methods are restricted to conventional MoM formulations only with Electric Field Integral Equation (EFIE). In this contribution, a MLFMM-UTD hybridization for Combined Field Integral Equation (CFIE) is proposed and applied within a hybrid Finite Element - Boundary Integral (FEBI) technique. The MLFMM-UTD hybridization is performed at the translation procedure on the various levels of the MLFMM, using a far-field approximation of the corresponding translation operator. The formulation of this new hybrid technique is presented, as well as numerical results.
Automotive Radar and Lidar Systems for Next Generation Driver Assistance Functions
Authors: Rasshofer R. H. , Gresser K.
Published: April 2010

Abstract. Automotive radar and lidar sensors represent key components for next generation driver assistance functions (Jones, 2001). Today, their use is limited to comfort applications in premium segment vehicles although an evolution process towards more safety-oriented functions is taking place. Radar sensors available on the market today suffer from low angular resolution and poor target detection in medium ranges (30 to 60m) over azimuth angles larger than ±30°. In contrast, Lidar sensors show large sensitivity towards environmental influences (e.g. snow, fog, dirt). Both sensor technologies today have a rather high cost level, forbidding their wide-spread usage on mass markets. A common approach to overcome individual sensor drawbacks is the employment of data fusion techniques (Bar-Shalom, 2001). Raw data fusion requires a common, standardized data interface to easily integrate a variety of asynchronous sensor data into a fusion network. Moreover, next generation sensors should be able to dynamically adopt to new situations and should have the ability to work in cooperative sensor environments. As vehicular function development today is being shifted more and more towards virtual prototyping, mathematical sensor models should be available. These models should take into account the sensor's functional principle as well as all typical measurement errors generated by the sensor.
Concept for the controlled plane wave exposure for animal experiments using a parabolic reflector
Authors: Tejero S. , Schelkshorn S. , Detlefsen J.
Published: April 2010

Abstract. In this paper a low-cost concept for the controlled RF plane wave exposure for in vivo experiments is presented. The exposure setup is based on the use of a parabolic reflector to convert the incident spherical wavefront emanating from the primary source into a plane wave. The employed paraboloid is a common prime focus paraboloid used in satellite-TV links. The main problems of the focussed approach are identified and a solution based on a defocussed system is introduced. It results in a compact, cost-effective and still power-efficient setup for the RF exposure at microwave frequencies. Simulation results show a very good performance of the concept achieving a quasi-plane wave incident on the animals with minimum variations of the exposure dose.
Investigations for broadband internet within high-speed trains
Authors: Gaspard I. , Zimmermann G.
Published: April 2010

Abstract. Broadband IP-based multimedia services are rapidly growing and there is the trend to use these services everywhere. Due to the fact that passengers in long distance high speed trains have a very comfortable environment to use their own terminal equipment, e.g. laptops with IEEE802.11×WLAN capability, it seems to be very promising to deliver broadband internet into trains. The challenge is the land-train connection where a high bit data rate link, e.g. 1Mbps in average in up- and downlink, has to be provided to enable several users within the train broadband internet access at the same time even at high speeds of the train. This paper describes a systematic approach starting at basic propagation measurements in a typical train environment and ending up with lab investigations by means of hardware channel simulation for different existing radio technologies which are candidates for the land-train connection.
Gate Leakage Reduction by Clocked Power Supply of Adiabatic Logic Circuits
Authors: Teichmann Ph. , Fischer J. , Amirante E. , Henzler St. , Bargagli-Stoffi A. , Otte Ch. , Schmitt-Landsiedel D.
Published: April 2010

Abstract. Losses due to gate-leakage-currents become more dominant in new technologies as gate leakage currents increase exponentially with decreasing gate oxide thickness. The most promising Adiabatic Logic (AL) families use a clocked power supply with four states. Hence, the full VDD voltage drops over an AL gate only for a quarter of the clock cycle, causing a full gate leakage only for a quarter of the clock period. The rising and falling ramps of the clocked power supply lead to an additional energy consumption by gate leakage. This energy is smaller than the fraction caused by the constant VDD drop, because the gate leakage exponentially depends on the voltage across the oxide. To obtain smaller energy consumption, Improved Adiabatic Logic (IAL) has been introduced. IAL swaps all n- and p-channel transistors. The logic blocks are built of p-channel devices which show gate tunneling currents significantly smaller than in n-channel devices. Using IAL instead of conventional AL allows an additional reduction of the energy consumption caused by gate leakage. Simulations based on a 90nm CMOS process show a lowering in gate leakage energy consumption for AL by a factor of 1.5 compared to static CMOS. For IAL the factor is up to 4. The achievable reduction varies depending on the considered AL family and the complexity of the gate.
Dynamische Rekonfiguration von arithmetischen Einheiten auf Bitebene
Authors: Pfänder O. A. , Pfleiderer H.-J.
Published: April 2010

Abstract. Im Hinblick auf Flexibilität und Effizienz beim modernen Schaltungsentwurf lohnt es sich oft, arithmetische Basiseinheiten mit passend gewählter fixer Wortlänge so zu erweitern, daß sich in Zusammenschaltung mit anderen Elementen eine übergeordnete Funktionalität mit erweiterter Bitbreite erreichen läßt. In diesem Beitrag soll die Multiplikation als konkretes Anwendungsbeispiel herangezogen werden. Dabei liegt das Hauptaugenmerk darauf, wie mit geringem Aufwand aus einer grundlegenden starren Struktur ein dynamisch rekonfigurierbarer Multiplizierer hervorgehen kann, der sowohl für vorzeichenlose als auch vorzeichenbehaftete Zahlen in den wichtigsten Zahldarstellungen geeignet ist. Die Vorgehensweise basiert auf dem Einsatz von Multiplexern auf Bitebene.
Analysis Method of Errors (Motion and Atmospheric) in Synthetic Aperture Radar (SAR) Images
Authors: Danklmayer A. , Camara de Macedo K. A. , Scheiber R. , Boerner T. , Chandra M.
Published: April 2010

Abstract. A method to allow the analysis of the effects of motion and atmospheric errors in SAR images is here presented. The objective of the method is to allow the visualization of the effects of motion errors and atmospheric artefacts on the processed (focused) SAR image. The method is intended to allow the analysis of the interaction of motion and atmospheric errors with the adopted SAR processing procedure and motion compensation algorithms. In this article the analysis method has been applied and tested to a C-Band E-SAR (DLR airborne SAR system) data set where we see that the effects of linear and non-linear phase errors observed are in agreement with the theory.
Model modulation to add smaller scale structures to large scale electron density models
Authors: Leitinger R. , Feichter E. , Rieger M.
Published: April 2010

Abstract. Usually regional and global electron density models provide large scale spatial structures only and smooth out the smaller scale features of the electron density distribution. We present a method to modulate existing electron density models by multiplication: M(h, φ, λ, t) = L(h, φ, λ, t) × S1(h, φ, λ, t) × S2(h, φ, λ, t) × ... Sn(h, φ, λ, t) M: resulting electron density distribution, L: large scale model, S1...Sn: modulating models for n the smaller scale structures; h: height; φ, λ: geographic coordinates, t: Universal Time. There are no restrictions to the nature of the large scale model provided it takes height and horizontal coordinates as input. Examples are models of the "profiler" type which use large scale "maps" for profile anchor points (e.g., E, F1, F2 peak properties) like the International Reference Ionosphere (IRI). Typical examples for smaller scale structures are ridges, troughs and wavelike disturbances. The advantage of modulation by multiplication is that there is no danger to get zero or negative values of electron density as long as the background and modulations are >0 everywhere. For each modulation model, unity means "undisturbed".
A Fractional Ramp Generator with Improved Linearity and Phase-Noise Performance for the Use in Heterodyne Measurement Systems
Authors: Musch T. , Schiek B.
Published: April 2010

Abstract. Concepts for the generation and the measurement of highly linear frequency ramps are presented. The fractional ramp synthesiser concept shown here is able to generate frequency ramps with a very low phase noise level, a very good frequency linearity and reproducibility. Related to the bandwidth of the generated frequency ramps of 4.5 GHz a relative linearity error below 4·10–10 is demonstrated in a prototype system. This linearity error is close to the limit set by the phase noise floor of the ramp generators and marks a significant improvement over existing aproaches (Musch and Schiek, 2000). The basic measurement sensitivity due to the phase noise is 1.8·10–10 without averaging. As the phase noise is important for the linearity of the frequency ramp the set-up has to be optimised for a good phase noise behaviour, too. In order to achieve this good phase noise a special phase-frequency detector is introduced that is especially designed for the use in a fractional phase locked loop.
Numerical quadrature for the approximation of singular oscillating integrals appearing in boundary integral equations
Authors: Fichte L. O. , Lange S. , Clemens M.
Published: April 2010

Abstract. Boundary Integral Equation formulations can be used to describe electromagnetic shielding problems. Yet, this approach frequently leads to integrals which contain a singularity and an oscillating part. Those integrals are difficult to handle when integrated naivly using standard integration techniques, and in some cases even a very high number of integration nodes will not lead to precise results. We present a method for the numerical quadrature of an integral with a logarithmic singularity and a cosine oscillator: a modified Filon-Lobatto quadrature for the oscillating parts and an integral transformation based on the error function for the singularity. Since this integral can be solved analytically, we are in a position to verify the results of our investigations, with a focus on precision and computation time.
Fast computation of electromagnetic near-fields with the multilevel fast multipole method combining near-field and far-field translations
Authors: Tzoulis A. , Eibert T. F.
Published: April 2010

Abstract. In Electromagnetic Compatibility (EMC) problems, computation of electromagnetic near-fields in the vicinity of complex radiation and scattering systems is often required. Numerical solution of such problems is achieved using Boundary Integral (BI) based approaches, where the involved Integral Equations (IE's) are solved with the Method of Moments (MoM). The MoM solution process is speeded up by fast IE solvers such as the Multilevel Fast Multipole Method (MLFMM). In the end the desired amplitudes of the expansion of the equivalent current densities on the discrete elements all over the Huygens' surfaces are known. Computation of the electromagnetic fields produced by the equivalent currents at observation points being in the near-field regions requires integration of the current densities over the Huygens' surfaces. Numerical evaluation of the near-field integrals using conventional integration rules can become extremely time consuming for large objects and large number of observation points. In this contribution, acceleration of the near-field integration of the equivalent current densities is provided using a postprocessing MLFMM, where near-field and far-field translations are combined in order to achieve optimum performance. The proposed approach was applied in the postprocessing stage of a powerful Finite Element Boundary Element (FEBI) method, resulting in significant decrease of the postprocessing computation time. The formulation of the proposed acceleration is presented and numerical results are shown.
A design approach for integrated CMOS LC-tank oscillators using bifurcation analysis
Authors: Prochaska M. , Bohle K. , Mathis W.
Published: April 2010

Abstract. Electrical oscillators play a decisive role in integrated transceivers for wired and wireless communication systems. In this context the study of fully integrated differential VCOs has received attention. In this paper formulas for investigations of the stability as well as the amplitude of CMOS LC tank oscillators are derived, where an overall model of nonlinear gain elements is used. By means of these results we are able to present an improved design approach which gives a deeper insight into the functionality of LC tank VCOs.
Full dynamic resolution low lower DA-Converters for flat panel displays
Authors: Saas C. , Franke J. , Nossek J. A.
Published: April 2010

Abstract. It has been shown that stepwise charging can reduce the power dissipated in the source drivers of a flat panel display. However the solution presented only provided a dynamic resolution of 3 bits which is not sufficient for obtaining a full color resolution display. In this work a further development of the basic idea is presented. The stepwise charging is increased to 4 bits and supplemented by a current source to provide an output signal which represents an 8 bit value with sufficient accuracy. Within this work the application is an AM-OLED flat panel display, but the concept can easily be applied to other display technologies like TFT-LCD as well.
Monotonic transition based forward body bias for dual threshold voltage low power embedded processors
Authors: Jayapal S. , Manoli Y.
Published: April 2010

Abstract. Dual threshold voltage and forward body bias techniques are effective ways to optimally balance the standby leakage power and performance. In this paper, we propose a novel fine-grained forward body biasing scheme for monotonic static logic circuits. In the proposed scheme, the forward body bias is applied to high threshold voltage of either the pull-up or the pull-down network based on the evaluation transition and the state of operation. This technique improves the low skew NAND and NOR circuit performance by 7% and 11%, high skew NAND and NOR by 8% and 13% respectively. It reduces both active and standby leakage power as compared to monotonic static CMOS with dual-VT technique. The simulations are carried out using 130 nm mixed mode process technology to validate our proposed technique.
On the synthesis and optimization of cascaded continuous-time Sigma-Delta modulators
Authors: Keller M. , Buhmann A. , Kuderer M. , Manoli Y.
Published: April 2010

Abstract. Up to now, there exist two completely different approaches for the synthesis of cascaded CT Sigma-Delta modulators. While the first method is based on a DT prototype and thus on the application of a DT-to-CT transformation, the second one is entirely performed in the CT domain. In this contribution, the method of lifting will be applied to overcome the disadvantages afflicted with the first method (e.g. less ideal anti-aliasing filter performance, increased circuit complexity) and to establish a time efficient DT simulation model for the second method. Thereby, optimal modulator coefficients as well as optimal digital cancellation filters for an arbitrary cascaded CT modulator can be simulated in an efficient and rapid manner. For illustrative purposes, the complete synthesis procedure is demonstrated by the example of a 2-1-1 cascaded CT modulator.
Neuartige, differentiell gespeiste Transmissionsleitung auf Silicium
Authors: El Rai S.
Published: April 2010

Abstract. Die elektrische Länge von technisch relevanten TLs liegt zwischen λ/8 und λ. Klassische TLs weisen jedoch kaum praktikabele Ausmaße in Ausbreitungsrichtung auf, (um sie in integrierte Schaltungen zu verwenden). Weiterhin besitzen die klassischen TLs hohe elektrische Dämpfungen, sobald ein hoher Wellenwiderstand angestrebt wird. Im vorliegender Artikel wird gezeigt, wie durch geometrisches Verändern der Leitungskonfiguration und Einfügen von MIM Kapazitäten herkömmliche, differentiell gespeisten Transmissionsleitungen gleichzeitig deren Leitungsabmessungen und deren Dämpfung bei gleicher elektrischer Länge bedeutend verringert werden kann.
Simulation von CNFET basierten Digitalschaltungen
Authors: Soffke O. , Zipf P. , Velten M. , Glesner M.
Published: April 2010

Abstract. Einwandige Kohlenstoff Nanoröhrchen können sowohl halbleitende als auch metallische Eigenschaften aufweisen, je nachdem wie die Röhrchenachse im Vergleich zur Anordnung der Kohlenstoffatome verläuft. Dies wird durch den sogenannten Aufrollvektor bestimmt. Halbleitende Nanoröhrchen können für Transistoren (CNFETs) verwendet werden, deren Verhalten sich mit einer modifizierten Version von Berkeley Spice 3f5 simulieren läßt. Die aus diesen Simulationen gewonnenen Parameter werden zur Parametrisierung von SystemC Modellen aus CNFETs bestehender Grundschaltungen verwendet, was zu einer um Größenordnungen höheren Simulationsgeschwindigkeit bei hoher Genauigkeit führt. Single walled carbon nanotubes (CNT) can be either metallic or semiconducting depending on the tube's orientation in relation to the configuration of the carbon atoms. This is determined by the so-called chiral vector. Semiconducting CNT can be used in transistors (CNFET) which can be simulated by a modified version of Berkeley Spice 3f5. The parameters determined by these simulations are used to parameterise SystemC models of some basic building blocks yielding fast simulations with high accuracy.
Automatisierte VHDL-Code-Generierung eines Delta-Sigma Modulators
Authors: Spilka R. , Ostermann T.
Published: April 2010

Abstract. Im vorliegenden Beitrag wird eine automatische Generierung des VHDL-Codes eines Delta-Sigma Modulators präsentiert. Die Koeffizientenmultiplikation wird hierbei durch Bit-Serielle-Addition durchgeführt. Mit Hilfe zweier neuer Matlab Funktionen wird der Systementwurf durch die bekannte Delta-Sigma Toolbox von R. Schreier erweitert und direkt synthesefähiger VHDL Code erzeugt.
Efficient ω-k-algorithm for circular SAR and cylindrical reconstruction areas
Authors: Dallinger A. , Schelkshorn S. , Detlefsen J.
Published: April 2010

Abstract. We present a novel reconstruction algorithm of ω-k type which suits for wideband circular synthetic aperture data taken in stripmap mode. The proposed algorithm allows to reconstruct an image on a cylindrical surface. The range trajectory is approximated by Taylor Series expansion using only the quadratic terms which limits the angular reconstruction range (cross range). In our case this is not a restriction for the application. Wider areas with respect to cross range can be realized by joining several reconstructed images side by side to build a wider image by means of digital spotlighting.
Advances in hybrid finite element – boundary integral – multilevel fast multipole – uniform geometrical theory of diffraction method
Authors: Tzoulis A. , Eibert T. F.
Published: April 2010

Abstract. Numerical modeling of problems including composite metallic/dielectric objects with arbitrary shapes and electrically large conducting objects within a common environment is performed in an optimum way with the recently developed powerful hybrid numerical method, which combines the Finite Element Boundary Integral (FEBI) method and the Multilevel Fast Multipole Method (MLFMM) with the Uniform Geometrical Theory of Diffraction (UTD), giving full electromagnetic coupling between all involved objects. In this contribution, the hybrid FEBI-MLFMM-UTD method is extended to double diffracted fields on pairs of straight metallic edges, formulated with the hard and soft scalar diffraction coefficients of UTD. The diffraction points on each pair of edges are determined by an iterative three-dimensional parametric realization of the generalized Fermat's principle. The divergence factor of the double diffracted field is computed by multiplying the appropriate divergence factors of the single diffracted UTD fields on each edge for the particular case. Thereby, the ray caustic distance of the diffracted field at the second edge is determined by linear interpolation between the radii of curvature in the two principal planes of the incident astigmatic ray tube. Further, fast near-field computation in the postprocessing stage of the hybrid method is extended in each translation domain to ray optical contributions due to the presence of electrically large objects, according to the hybridization of MLFMM with UTD. Formulations and numerical results will be presented.
Contactless vector network analysis using diversity calibration with capacitive and inductive coupled probes
Authors: Zelder T. , Rolfes I. , Eul H.
Published: April 2010

Abstract. Contactless vector network analysis based on a diversity calibration is investigated for the measurement of embedded devices in planar circuits. Conventional contactless measurement systems based on two probes for each measurement port have the disadvantage that the signal-to-noise system dynamics strongly depends on the distance between the contactless probes. In order to avoid a decrease in system dynamics a diversity based measurement system is presented. The measurement setup uses one inductive and two capacitive probes. As an inductive probe a half magnetic loop in combination with a broadband balun is introduced. In order to eliminate systematic errors from the measurement results a diversity calibration algorithm is presented. Simulation and measurement results for a one-port configuration are shown.
Realisierung eines verzerrungsarmen Open-Loop Klasse-D Audio-Verstärkers mit SB-ZePoC
Authors: Schnick O. , Mathis W.
Published: April 2010

Abstract. In den letzten Jahren hat die Entwicklung von Klasse-D Verstärkern für Audio-Anwendungen ein vermehrtes Interesse auf sich gezogen. Eine Motivation hierfür liegt in der mit dieser Technik extrem hohen erzielbaren Effizienz von über 90%. Die Signale, die Klasse-D Verstärker steuern, sind binär. Immer mehr Audio-Signale werden entweder digital gespeichert (CD, DVD, MP3) oder digital übermittelt (Internet, DRM, DAB, DVB-T, DVB-S, GMS, UMTS), weshalb eine direkte Umsetzung dieser Daten in ein binäres Steuersignal ohne vorherige konventionelle D/A-Wandlung erstrebenswert erscheint. Die klassischen Pulsweitenmodulationsverfahren führen zu Aliasing-Komponenten im Audio-Basisband. Diese Verzerrungen können nur durch eine sehr hohe Schaltfrequenz auf ein akzeptables Maß reduziert werden. Durch das von der Forschungsgruppe um Prof. Mathis vorgestellte SB-ZePoC Verfahren (Zero Position Coding with Separated Baseband) wird diese Art der Signalverzerrung durch Generierung eines separierten Basisbands verhindert. Deshalb können auch niedrige Schaltfrequenzen gewählt werden. Dadurch werden nicht nur die Schaltverluste, sondern auch Timing-Verzerrungen verringert, die durch die nichtideale Schaltendstufe verursacht werden. Diese tragen einen großen Anteil zu den gesamten Verzerrungen eines Klasse-D Verstärkers bei. Mit dem SB-ZePoC Verfahren lassen sich verzerrungsarme Open-Loop Klasse-D Audio-Verstärker realisieren, die ohne aufwändige Gegenkopplungsschleifen auskommen. Class-D amplifiers are suiteble for amplification of audio signals. One argument is their high efficiency of 90% and more. Today most of the audio signals are stored or transmitted in digital form. A digitally controlled Class-D amplifier can be directly driven with coded (modulated) data. No separate D/A conversion is needed. Classical modulation schemes like Pulse-Width-Modulation (PWM) cause aliasing. So a very high switching rate is required to minimize the aliasing component within the signal band. This paper shows a first implementation of the new SB-ZePoC modulation scheme (Zero Position Coding with Separated Baseband), which allows the generation of a binary signal with separated baseband. Therefore Class-D amplifiers using SB-ZePoC can be run with very low switching rates. Some benefits and problems in the design process because of low switching rates will be discussed. Measurements of a realtime implementation will be presented.
Zellulare Nichtlineare Netzwerke: Anwendungen in der Informationstechnologie
Authors: Tetzlaff R.
Published: April 2010

Abstract. Zellulare Nichtlineare Netzwerke (CNN) wurden 1988 von Chua und Yang (Chua und Yang, 1988) eingeführt. Diese Netzwerke sind dadurch gekennzeichnet, dass eine Zelle, die die kleinste Einheit eines CNN darstellt, nur mit Zellen innerhalb einer bestimmten Umgebung verbunden ist. üblicherweise sind Art und Stärke der Wechselwirkung zwischen zwei Zellen eines CNN translationsinvariant, d.h. sie hängen nur von der relativen Lage beider Zellen zueinander ab. Im Vordergrund aktueller Arbeiten stehen auf derartigen Netzwerken basierende schaltungstechnische Realisierungen mit bis zu 176x144 Zellen, die eine direkte Verbindung zu zweidimensionalen optischen Sensor-Anordnungen aufweisen. Über einen separaten Speicherbereich können die Zellkopplungen eines Netzwerks verändert werden, wodurch eine adaptive Verarbeitung von mehrdimensionalen Sensorsignalen ermöglicht wird. Das kürzlich vorgestellte so genannte EyeRis System (Anafocus Ltd.) enthält zusätzlich noch einen Standardprozessor und stellt (bei einer Größe vergleichbar mit der einer Kreditkarte) daher ein vollständiges superschnelles System zur Informationsverarbeitung dar. In diesem Beitrag sollen, nach einem kurzen Überblick über die Eigenschaften von CNN, aktuelle Realisierungen und exemplarisch eine neuere eigene Anwendung vorgestellt und besprochen werden.