bluuebunny/crossref_metadata_2025 huggingface dataset:
Long-period upper mesosphere temperature and plasma scale height variations derived from VHF meteor radar and LF absolute reflection height measurements
Authors: Jacobi C. , Kürschner D.
Published: April 2010

Abstract. The change of ionospheric absolute reflection heights h of low-frequency (LF) radio waves at oblique incidence in the course of the day is measured at Collm Observatory (51.3° N, 13.0° E) using 1.8 kHz sideband phase comparisons between the sky-wave and the ground wave of a commercial 177 kHz transmitter (Zehlendorf, reflection point at 52.1° N, 13.2° E). Plasma scale height estimates H are calculated from the decrease/increase of h in the morning/evening. The day-to-day variations of H are compared with those of daily mean temperatures at 90 km, measured with a VHF meteor radar (36.2 MHz) at Collm and using the amplitude decay of meteor reflections. A good qualitative correspondence is found between the two data sets. Since mesospheric long-period temperature variations are generally accepted to be the signature of atmospheric planetary waves, this shows that LF reflection height measurements can be used for monitoring the dynamics of the upper middle atmosphere.
A multilevel fast spectral domain algorithm for electromagnetic analysis of infinite periodic arrays with large unit cells
Authors: Eibert T. F.
Published: April 2010

Abstract. A multilevel fast spectral domain algorithm (MLFSDA) is introduced for the efficient evaluation of the matrix vector products due to the boundary integral (BI) operator within a hybrid finite element - BI (FEBI) method for the analysis of infinite periodic arrays. The MLFSDA utilizes the diagonalization property of the spectral domain (SD) BI representation and handles the large numbers of Floquet modes required for large (with respect to wavelength) periodic unit cells by similar hierarchical techniques as applied in the multilevel fast multipole method/algorithm (MLFMM/MLFMA). With the capability of the MLFSDA to handle very large periodic unit cells, it becomes possible to model finite antennas and scatterers with the infinite periodic array model. For a cavity-backed antenna element and for a semi-finite array of 4 cavity-backed antenna elements in the finite direction, the dependence of the input impedances on the unit cell sizes is investigated and it is found that array resonances disappear for reasonably large unit cell dimensions. Finally, a semi-finite array of antipodal Vivaldi antenna elements is considered and simulation results for infinite periodic, finite, and semi-finite array configurations are compared to measured data.
Numerical simulation of transient electro-quasistatic fields using advanced subspace projection techniques
Authors: Steinmetz T. , Wimmer G. , Clemens M.
Published: April 2010

Abstract. The transient simulation of electro-quasistatic fields requires a formulation that takes both dielectric effects as well as nonlinear conductive effects into account. The successive solution of large linear systems of equations with similar or even identical system matrices has to be performed repeatedly if this formulation is discretized by the Finite-Element method and an Implicit-Runge-Kutta method, respectively. The solution processes can be accelerated by using subspace recycling techniques and subspace projection extrapolation techniques. Numerical results for three-dimensional high-voltage applications are presented and the efficiency of these techniques is shown.
Numerische Berechnung von Wirbelstromproblemen mit der Cell-Methode
Authors: Frenner K. , Rucker W. M.
Published: April 2010

Abstract. In dieser Arbeit wird die Cell-Methode auf die quasistatischen Maxwellgleichungen angewendet. Dabei werden für die notwendige Transformation vom Primärgitter auf das duale Gitter reziproke Basisvektoren verwendet. Anhand der Felddiffusion der magnetischen Induktion in einen zylindrischen Leiter werden Ergebnisse der Cell-Methode mit einer analytischen Vergleichsrechnung präsentiert.
Optimierung von FSS-Bandpassfiltern mit Hilfe der Schwarmintelligenz (Particle Swarm Optimization)
Authors: Wu G. , Hansen V. , Kreysa E. , Gemünd H.-P.
Published: April 2010

Abstract. In diesem Beitrag wird ein neues Verfahren zur Optimierung von Bandpassfiltern aus mehrlagigen frequenzselektiven Schirmen (FSS), die in ein Dielektrikum eingebettet sind, vorgestellt. Das Ziel ist es, die Parameter der gesamten Struktur so zu optimieren, dass ihre Transmissionseigenschaften hohe Filteranforderungen erfüllen. Als Optimierungsverfahren wird die Particle Swarm Optimization (PSO) eingesetzt. PSO ist eine neue stochastische Optimierungsmethode, die in verschieden Gebieten, besonders aber bei der Optimierung nicht linearer Probleme mit mehreren Zielfunktionen erfolgreich eingesetzt wird. In dieser Arbeit wird die PSO in die Spektralbereichsanalyse zur Berechnung komplexer FSS-Strukturen integriert. Die numerische Berechnung basiert auf einer Integralgleichungsformulierung mit Hilfe der spektralen Greenschen Funktion für geschichtete Strukturen. This paper presents a novel procedure for the optimization of band-pass filters consisting of frequency selective surfaces (FSS) embedded in a dielectric. The aim is to optimize the parameters of the complete structure so that the transmission characteristics of the filters fulfill the demanding requirements. The Particle Swarm Optimization (PSO) is used as the optimization procedure. PSO is a new stochastic optimization method that is successfully applied in different areas for the optimization of non-linear problems with several object-functions. In this work, PSO is integrated into the spectral domain analysis for the calculation of the complex FSS structures. The numerical computation is based on the formulation of an integral equation with the help of the spectral Green's function for layered media.
Coherent and non-coherent processing of multiband radar sensor data
Authors: Tejero S. , Siart U. , Detlefsen J.
Published: April 2010

Abstract. Increasing resolution is an attractive goal for all types of radar sensor applications. Obtaining high radar resolution is strongly related to the signal bandwidth which can be used. The currently available frequency bands however, restrict the available bandwidth and consequently the achievable range resolution. As nowadays more sensors become available e.g. on automotive platforms, methods of combining sensor information stemming from sensors operating in different and not necessarily overlapping frequency bands are of concern. It will be shown that it is possible to derive benefit from perceiving the same radar scenery with two or more sensors in distinct frequency bands. Beyond ordinary sensor fusion methods, radar information can be combined more effectively if one compensates for the lack of mutual coherence, thus taking advantage of phase information. At high frequencies, complex scatterers can be approximately modeled as a group of single scattering centers with constant delay and slowly varying amplitude, i.e. a set of complex exponentials buried in noise. The eigenanalysis algorithms are well known for their capability to better resolve complex exponentials as compared to the classical spectral analysis methods. These methods exploit the statistical properties of those signals to estimate their frequencies. Here, two main approaches to extend the statistical analysis for the case of data collected at two different subbands are presented. One method relies on the use of the band gap information (and therefore, coherent data collection is needed) and achieves an increased resolution capability compared with the single-band case. On the other hand, the second approach does not use the band gap information and represents a robust way to process radar data collected with incoherent sensors. Combining the information obtained with these two approaches a robust estimator of the target locations with increased resolution can be built.
Design und Analyse elektrisch kleiner Antennen für den Einsatz in UHF RFID Transpondern
Authors: Herschmann R. , Camp M. , Eul H.
Published: April 2010

Abstract. RFID Systeme werden seit Anfang der neunziger Jahre mit stetig zunehmender Verbreitung im Bereich der automatischen Produktidentifikation, der Diebstahlsicherung (EAS, Electronic Article Surveillance) und für automatische Zutrittskontrollsysteme eingesetzt. Objekte werden hierzu mit einem Transponder ausgestattet, der aus einer Antenne und einem Chip auf einem Trägermaterial besteht. Von großem Interesse ist die Entwicklung und Optimierung von passiven Transpondern für den Einsatz in UHF RFID Systemen. Diese Transponder beziehen die Energie zum Betrieb des Chips aus dem elektromagnetischen Feld einer Schreib-Leseeinheit. Hierfür ist neben der Anpassung der Eingangsimpedanz der Antenne an die Chipimpedanz auch eine möglichst hohe Bandbreite der Antennen wünschenswert, um die Funktion des Transponders bei Schwankungen der Chipimpedanz und variablen Umgebungsparametern zu gewährleisten. Der aus Platzgründen notwendige Einsatz elektrisch kleiner Antennen bedingt eine möglichst optimale Ausnutzung der zur Verfügung stehenden Fläche auf dem Trägermaterial zur Aufnahme der Antenne. Die vorliegende Arbeit beschreibt ein Verfahren zur Analyse und Synthese neuartiger Antennendesigns auf der Basis parametrisierter meandrierter, spiralförmiger und logarithmisch periodischer Dipole.
Determination of the input impedance of RFID transponder antennas with novel measurement procedure using a modified on-wafer-prober
Authors: Camp M. , Herschmann R. , Zelder T. , Eul H.
Published: April 2010

Abstract. This paper shows a new method to determine the input impedance of RFID transponder antennas with a combination of on-wafer-prober and network analyzer. It is shown that the results are in a good agreement with FEM simulations (HFSS) for a large part of the examined antenna structures.
On the optimum antenna pattern for widebeam radar reflectivity estimation
Authors: Gerbl F. , Biebl E. M.
Published: April 2010

Abstract. Noise is a limiting factor in radar systems. The power received from a target depends on the target reflectivity varying with the aspect angle, the target range and the antenna pattern, amongst others. Inevitably, an estimation algorithm for the mean target reflectivity weights noise contributions from greater aspect angles stronger than such from smaller aspect angles due to the target range increasing with increasing aspect angle. However, as an opposed effect, due to the supposed equidistant rather than equiangular sampling along the linear aperture, noise contributions for greater aspect angles have lower influence than those for smaller aspect angles. In the paper, the signal-to-noise ratio for a linear, equidistantly sampled aperture and an arbitrary antenna pattern is determined. Moreover, an upper limit for the achievable signal-to-noise ratio is given, and the antenna pattern maximizing the signal-to-noise ratio is derived.
On network representations of antennas inside resonating environments
Authors: Gronwald F. , Glüge S. , Nitsch J.
Published: April 2010

Abstract. We discuss network representations of dipole antennas within electromagnetic cavities. It is pointed out that for a given configuration these representations are not unique. For an efficient evaluation a network representation should be chosen such that it involves as few network elements as possible. The field theoretical analogue of this circumstance is the possibility to express electromagnetic cavities' Green's functions by representations which exhibit different convergence properties. An explicit example of a dipole antenna within a rectangular cavity clarifies the corresponding interrelation between network theory and electromagnetic field theory. As an application, current spectra are calculated for the case that the antenna is nonlinearly loaded and subject to a two-tone excitation.
Bestimmung der Exposition der Bevölkerung in der Umgebung von GSM und UMTS Basisstationen
Authors: Bornkessel C. , Schubert M. , Wuschek M. , Schmidt P.
Published: April 2010

Abstract. Vorliegender Beitrag fasst die Ergebnisse von zwei Projekten aus dem Deutschen Mobilfunk Forschungsprogramm (DMF) zusammen, die vom Bundesamt für Strahlenschutz und dem Ministerium für Umwelt, Naturschutz und Reaktorsicherheit (BMU) gefördert wurden. Sie beschäftigen sich mit der Entwicklung von Mess- und Berechnungsverfahren zur Bestimmung der Exposition der Bevölkerung in der Umgebung von GSM- und UMTS-Basisstationen sowie einer Analyse der elektromagnetischen Feldverteilung in verschiedenen Szenarien im Umfeld derartiger Sendeanlagen.
Retrospektive Bestimmung der elektromagnetischen Exposition durch analoge Rundfunksender im Rahmen von KiSS
Authors: Philipp J. , Merzenich H. , Brüggemeyer H. , Schmiedel S. , Blettner M. , Schüz J.
Published: April 2010

Abstract. Im Rahmen einer epidemiologischen Fall-Kontroll-Studie zur Untersuchung eines möglichen Zusammenhangs zwischen der Häufigkeit kindlicher Leukämien und elektromagnetischer Strahlung (,,KiSS" – Kindliche Leukämien und Expositionen in der Umgebung von hochfrequenten Sendestationen) soll die Exposition durch leistungsstarke analoge Rundfunksender retrospektiv (Zeitraum 1982–2003) quantifiziert werden. Die zu betrachtenden Sendernetze für AM-Hörfunk, FM-Hörfunk und analoges Fernsehen unterscheiden sich nicht nur hinsichtlich der Modulationsart und der von den Einzelsendern abgestrahlten Leistung, sondern auch in der Netzkonfiguration und den je nach Wellenbereich verschiedenen Strahlungseigenschaften der Sendeantennen. Damit sind bei diesen drei Rundfunkdiensten sowohl die absolute Größe als auch die räumliche Struktur der hervorgerufenen Exposition verschieden. Es wird dargelegt, wie die für die Prognose der Rundfunkversorgung verwendeten Rechenverfahren zur Modellierung der Feldstärke für die Modellierung der Exposition herangezogen und durch Kontrollmessungen validiert werden und wie trotz Wahrung der Vertraulichkeit der dabei unabdingbar zu verwendenden Senderbetriebsdaten eine unerwünschte Beeinflussung der Studienergebnisse durch die Senderbetreiber ausgeschlossen wird.
Front End Schaltung zur Online Auswertung von EKG-Signalen
Authors: Ayari E. , Tielert R.
Published: April 2010

Abstract. Ein mobiles EKG-System zur Online Auswertung von EKG-Signalen wird dargestellt. Die Auswertung beruht auf ein energiesparendes Verfahren, das den Vorteil einer zulässigen Unterabtastung des Signals bietet und eine Interaktion zwischen der messenden Elektronik und dem funkgebundenen Auswertungsrechner ermöglicht. Diese Interaktion besteht darin, sowohl die Front End Schaltung im EKG-Sensor als auch den im ATmega8L eingebetteten A/D-Wandler vom Auswertungsrechner zu steuern und den Datenbedarf des Rechners dynamisch an die Erfordernisse des Analyseprogramms anzupassen. Das entwickelte EKG-System liefert erfolgreiche Charakterisierungen erfasster Elektrokardiogramme. A mobile ecg-system for an online analysis of electrocardiogram signals is presented. The analysis is based on an energy-saving procedure, which offers the advantage of an acceptable undersampling of the signal, and which allows an interaction between the measuring electronic and the radio-bound analysis-computer. In this interaction both the front-end circuit in the ecg-sensor and the A/D converter, which is embedded in the ATmega8L, are steered by the analysis computer. The data requirement of the computer is also dynamically adapted to the requirements of the analysis-program. The developed ecg-system supplies successful characterisations of measured electrocardiograms.
Analyse und Entwurf von hochbitratigen Clock-and-Data-Recovery Schaltungen in CMOS-Technologie
Authors: Bremer J.-K. , Zemko C. , Schmackers J. , Mathis W.
Published: April 2010

Abstract. In dieser Arbeit wird ein neuartiges Schaltungskonzept für die Realisierung eines Phasendetektors einer Clock-and-Data-Recovery Schaltung vorgestellt. Es handelt sich hierbei um eine nichtlineare Phasendetektorarchitektur, die nach dem Verfahren von Alexander arbeitet. Um die Funktionalität des Phasendetektors im Hochfrequenzbereich zu gewährleisten, wurden in dem Design sehr schnell schaltende HLO-Flip-Flops (high-speed latching operation flip-flop) verwendet. Ein wesentliches Entwurfsziel war die Begrenzung des selbstgenerierten Jitters des Phasendetektors. Der Schaltungsentwurf wurde mit der Simulationsumgebung Cadence Spectre durchgeführt und die Funktionalität der Schaltung im GHz-Bereich anhand von ausgewählten Simulationen verifiziert. This paper presents a novel realization concept for Clock-and-Data-Recovery circuits. Our Design uses a nonlinear phase detector architecture, which is based on the Alexander phase detection method. In order to ensure circuit functionality in the RF region, we use very fast switching HLO-Flip-Flops (high-speed latching operation flip-flop) in our design. The primal goal in our design was the minimization of self induced jitter of the phase detector. The accuracy of our circuit design and the functionality in the GHz regime is confirmed by various circuit simulations executed with the SPECTRE Simulator.
Entwurf von zeitkontinuierlichen ΣΔ-Modulatoren – Äquivalenz zwischen zeitkontinuierlichen und zeitdiskreten Systemen
Authors: Anders J. , Mathis W. , Ortmanns M.
Published: April 2010

Abstract. Im vorliegenden Artikel wird eine vollstängige, d.h. unter Einbeziehung des Eingangssignals, Äquivalenz zwischen zeitkontinuierlichen und zeitdiskreten ΣΔ-Modulatoren im Zustandsraum hergeleitet. Es wird ebenfalls gezeigt, wie eine wichtige Nichtidealität, das sog. "excess loop delay", in den Berechnungen berücksichtigt werden kann. Die dargestellte Methode dient dazu, den Entwurf und dabei vor allem die Stabilitätsuntersuchungen, von zeitkontinuierlichen ΣΔs auf die bereits empirisch intensiv erforschten zeitdiskreten Systeme zurückzuführen. In the article at hand a complete equivalency, i.e. including the input signal, between continuous-time and discrete-time ΣΔ-modulators in state-space is derived. In addition, it is shown, how one can incorporate the important non-ideality of "excess loop delay" into the formalism. The method introduced is supposed to facilitate the design, especially the stability analysis part of the design, of continuous-time ΣΔs by making use of the empirically thoroughly examined discrete-time systems.
Eine präzise Multilevel-Testbench zur Systemsimulation und Charakterisierung einer 2,5 GHz PLL
Authors: Kebaisy I. , Maibaum F. , Hinz M. , Meinerzhagen B.
Published: April 2010

Abstract. In diesem Aufsatz wird eine präzise Multilevel-Testbench zur PLL-Charakterisierung vorgestellt. Die Schwerpunkte dieses Beitrags sind einerseits das 10 GHz VCO-Design und andererseits die vorhersagefähigen Ergebnisse der mit Hilfe dieses Multilevelansatzes durchgeführten PLL-Systemsimulationen. Bei dem VCO-Design wurden folgende Ergebnisse erreicht: Abstimmbereich ≈26% bzw. kvco≈1300 MHz/V, Phasenrauschen PN=–101,4 dBc/Hz @1 MHz Offset vom 10 GHz Träger, Leistungsverbrauch = 5,5 mW. Als realistisches Demonstrationsbeispiel ist das „analog mixed signal“-Verhalten eines 2,5 GHz PLL-Systems für „dual-conversion“-Strukturen bei IEEE 802.11a WLAN-Anwendungen gewählt worden. Für dieses Beispiel wird eine effiziente PLL-Modellierung kritischer PLL-Blöcke (Frequenzteiler und Phasenfrequenzdetektor) auf der Basis der PSS-Analyse und neuer Verilog-A/MS Befehle demonstriert. Die dabei verwendete Testbench kann im Prinzip in verschiedenen aktuellen Wireless Kommunikationssystemen bis 10 GHz wieder verwendet werden (Reuse-IP). Dieser Ansatz führt einerseits zur Verbesserung der Simulationszeiten (verglichen mit dem Transistorlevel) und andererseits zu genaueren und realistischeren Ergebnissen, vor allem am VCO-Ausgang (verglichen mit dem HDL-Level).
Open water, inundated vegetation and upland vegetation discriminated through a disturbing atmosphere
Authors: Böttger U. , Demircan A. , Vanderbilt V.
Published: April 2010

Abstract. Methane is an important greenhouse gas. The areal extent of Boreal wetlands, source areas for methane, is poorly known. At times estimates have differed by as much as seven fold, which contributes uncertainty to present day energy and carbon budgets and to projections of future climates. In this research we applied optical remote sensing technology to identify methane source areas in POLDER imagery collected from both aircraft and satellite. Our approach takes advantage of the specular reflecting properties of surface waters in order to differentiate inundated wetlands (with emergent vegetation), open water (without emergent vegetation) and non-inundated cover types. Unlike our previous research, here we account for the affects of the disturbing atmosphere, presenting a radiative transfer model that represents an atmosphere above a mixed pixel that includes various proportions of open water, inundated vegetation and upland vegetation. The results show that our algorithm accurately identified these three cover types in both aircraft and satellite data. The results point to the probable importance of atmospheric correction to the discrimination procedure.
Reduction of electromagnetic exposure using hybrid (DVB-H/UMTS) networks
Authors: Schack M. , Unger P. , Kürner T.
Published: April 2010

Abstract. The hybrid mobile communication network described in this paper consists of a point-to-point network (UMTS) and a point-to-multipoint network (DVB-H). Using an additional DVB-H network increases the downlink capacity of the communications system. Another benefit of combining these two networks is an optimised transfer of data by collecting several user requests for a single response via the broadcast network DVB-H. It is analysed how the hybrid network structure influences the electromagnetic exposure. Therefore, realistic scenarios have been developed consisting of different user behaviour and different network structures. These scenarios provide building data for investigations of indoor coverage and realistic propagation of signals. In order to evaluate the grade of exposure, criteria have been defined. These criteria have been used for comparing a hybrid network with a single UMTS network in terms of electromagnetic exposure. The simulation results of the scenarios are shown for different network structures and network configurations.
Radio network planning and human exposure to electromagnetic fields
Authors: Baldauf M. A. , Sörgel W. , Wiesbeck W.
Published: April 2010

Abstract. This paper analyzes the effect of a change in cell size and of transmit power control on the human exposure to electromagnetic fields. In a simplified network configuration the well accepted COST-Hata model is considered to assess the path loss. It is shown that increasing the base station density will not generally raise the exposure but can rather help to lower it significantly. The exposure due to base stations is hardly affected by allowing a transmit power reduction at the base station for individual links. In contrast to this, it is demonstrated that transmit power control at the mobile station is a helpful means to lower the exposure efficiently.
The CPW-TEC project: Planetary waves in the middle atmosphere and ionosphere
Authors: Jacobi C. , Jakowski N. , Pogoreltsev A. , Fröhlich K. , Hoffmann P. , Borries C.
Published: April 2010

Abstract. Maps of vertically integrated electron density over the higher middle and polar latitudes that are regularly produced by DLR Neustrelitz are investigated with respect to planetary waves (PW) in the period range of several days. The results are compared with planetary wave analyses using stratospheric reanalyses. Case studies show that PW signatures in the ionosphere and neutral middle atmosphere waves have similar seasonal variations, indicating a possible coupling between these layers. Numerical modelling of the middle and upper atmosphere is performed to analyse the possible penetration of PW effects into the thermosphere. Numerical results show that direct propagation of PW to the thermosphere is not possible, and indirect ionospheric effects must be responsible for the wave coupling of the atmospheric layers. In the paper an overview of the data used and the methods applied in this project is given.
Modellierung des elektrischen Feldes für Anordnungen mit Singularitäten
Authors: Mente D. , Greiff M. , Mathis W.
Published: April 2010

Abstract. Mit Hilfe von weitverbreiteten numerischen Methoden wie BEM/FEM lassen sich Singularitäten im Feldverlauf nur bedingt berücksichtigen. Es sollen daher zwei alternative numerische Feldberechnungsmethoden vorgestellt werden, die sich insbesondere für Spitzengeometrien eigenen, wie sie bei Rasterkraftmikroskopen eingesetzt werden. Dabei soll ein weiteres Augenmerk auf die Eignung der Kopplung der vorgeschlagenen Methoden an andere Feldberechnungsmethoden gerichtet werden. Modern numerical methods for field calculations are having problems dealing with singularities correctly. This paper provides two alternative methods that are able to handle electric fields including singularities in tip-like configurations. These configurations occur in atomic force microscopes. Another focus will be the suitability of coupling the presented methods with usual numerical methods.
A comparison of software- and hardware-gating techniques applied to near-field antenna measurements
Authors: Leibfritz M. M. , Blech M. D. , Landstorfer F. M. , Eibert T. F.
Published: April 2010

Abstract. It is well-known that antenna measurements are error prone with respect to reflections within an antenna measurements test facility. The influence on near-field (NF) measurements with subsequent NF to far-field (FF) transformation can be significantly reduced applying soft- or hard-gating techniques. Hard-gating systems are often used in compact range facilities employing fast PIN-diode switches (Hartmann, 2000) whereas soft-gating systems utilize a network analyzer to gather frequency samples and eliminate objectionable distortions in the time-domain by means of Fourier-transformation techniques. Near-field (NF) antenna measurements are known to be sensitive to various errors concerning the measurement setup as there have to be mentioned the accuracy of the positioner, the measurement instruments or the quality of the anechoic chamber itself. Two different approaches employing soft- and hard-gating techniques are discussed with respect to practical applications. Signal generation for the antenna under test (AUT) is implemented using a newly developed hard-gating system based on digital signal synthesis allowing gate-widths of 250 ps to 10 ns. Measurement results obtained from a Yagi-Uda antenna under test (AUT) and a dual polarized open-ended waveguide used as probe antenna are presented for the GSM 1800 frequency range.
A simple evaluation procedure of the TAN calibration and the influence of non-ideal calibration elements on VNA S-parameter measurements
Authors: Stumper U.
Published: April 2010

Abstract. For the 7-term general TAN (Through-Attenuator-Network) self-calibration method of a four-sampler vector network analyser (VNA), and for all derived calibration methods like TLN, TRL, TRM, TAR, or TMN, it is shown that a very simple evaluation procedure of the seven error terms is possible, even if the Through connection is replaced by a reflectionless network with known transmission. Expressions for the deviations of the measured S-parameters of two-port test objects (d.u.t.s) from the true values, which are caused by deviations of the modeled S-parameters of non-ideal calibration elements ("standards") from their true values, are also presented. Additionally, it is shown that a TAN calibration is also possible in case of unequal reflections of the Network.
Electromagnetic and transient shielding effectiveness for near-field sources
Authors: Möller C. , Klinkenbusch L.
Published: April 2010

Abstract. The contribution deals with an investigation of the recently proposed definitions for the electromagnetic and transient shielding effectiveness (SE) in the case of an electric-dipole near-field source. To this end, new factors are introduced which depend on the distance between the dipole source and the measurement point inside the shield and which are valid for perpendicularly (with respect to the distance vector) polarized dipoles. Numerical results support and confirm the theoretical derivations.
A wireless MIMO CPM system with blind signal separation for incoherent demodulation
Authors: Weikert O. , Zölzer U.
Published: April 2010

Abstract. A multiple-input multiple-output (MIMO) wireless transmission system with continuous phase modulation (CPM) is considered. A novel MIMO CPM receiver with incoherent modulation is presented. The incoherent demodulation of CPM allows an uncomplicated handling of a frequency offset compared to coherent approaches requiring exact knowledge of the carrier frequency. Blind signal separation (BSS) is applied in the proposed MIMO CPM receiver to separate the signals without any knowledge of the MIMO channel. The BSS permits the demodulation of each separated signal by an incoherent CPM demodulator. For bandwidth efficient transmission partial response CPM and non-binary modulation is applied. The applicability of the proposed system is verified by simulation results.
A hybrid equalizer/Rake receiver for the Wideband CDMA Downlink in large delay spread channels
Authors: Buchacher C. , Zimmermann M. , Paul S. , Huemer M.
Published: April 2010

Abstract. Signals transmitted over a multi-path propagation channel exhibit Inter-Path Interference (IPI) and fading. The receiver has to employ measures to mitigate these effects or it will incur severe performance degradation. A classic approach in Code Division Multiple Access (CDMA) communications is the Rake receiver. Alternatively, a Linear Minimum Mean Square Error (LMMSE) equalizer can further improve performance. This paper compares performance and computational complexity of these two algorithms. A hybrid solution will be introduced in order to decrease computational complexity while retaining most of the interference suppression capabilities of the LMMSE equalizer.
Auxiliary branch method and modified nodal voltage equations
Authors: Reibiger A.
Published: April 2010

Abstract. A theorem is presented describing a transformation by means of which it is possible to assign to an elementary multiport with fairly general constitutive equations (including all kinds of controlled sources, nullors, ideal transformers, etc.) a modified multiport with the same all-pole terminal behavior. The branch set of this modified multiport is augmented with so called auxiliary branches whereas its constitutive equations are always in conductance form. Therefore an interconnection of a family of multiports transformed in this manner can always be analyzed by means of a system of nodal voltage equations. It will be shown that this system of equations is equivalent to a system of modified nodal voltage equations set up for the network that is an interconnection of the elementary multiports originally given.
The asynchronous rapid single-flux quantum electronics – a promising alternative for the development of high-performance digital circuits
Authors: Dimov B. , Ortlepp Th. , Mladenov V. , Terzieva S. , Uhlmann F.  H.
Published: April 2010

Abstract. In this paper, we investigate the application of the asynchronous logic approach for the realization of ultra high-speed digital electronics with high complexity. We evaluate the possible physical, technological, and schematical origins of restrictions limiting such an application, and propose solutions for their overcoming. Although our considerations are based on the rapid single-flux quantum technique, the conclusions derived can be generalized about any type of digital information coding.
Simultaneous large-scale reliability analysis of ultra-thin MOS gate dielectrics using an automated test system
Authors: Domdey A. , Hafkemeyer K. M. , Krautschneider W. H. , Schroeder D.
Published: April 2010

Abstract. This article presents an automated test system targeting the large-scale analysis of ultra-thin MOS gate dielectric degradation. The system allows for stress tests at elevated temperatures as well as supply voltages and long-term tests of thousands of MOS devices simultaneously. The aim is to build-up large and hence significant statistics about the degradation process as a function of time.
Investigation of carbon nanotube antennas using thin wire integral equations
Authors: Fichtner N. , Zhou X. , Russer P.
Published: April 2010

Abstract. In this paper the characteristics of small carbon nanotube (CNT) dipole antennas are investigated on the basis of the thin wire Hallén integral equation (IE). A surface impedance model for the CNT is adopted to account for the specific material properties resulting in a modified kernel function for the integral equation. A numerical solution for the IE gives the current distribution along the CNT. From the current distribution the antenna driving point impedance and the antenna efficiency are computed. The presented numerical examples demonstrate the strong dependence of the antenna characteristics on the used material and show the limitations of nanoscale antennas.
A low-noise current preamplifier in 120 nm CMOS technology
Authors: Uhrmann H. , Gaberl W. , Zimmermann H.
Published: April 2010

Abstract. In this paper we examine the impact of deep sub-micron CMOS technology on analog circuit design with a special focus on the noise performance and the ability to design low-noise preamplifiers. To point out, why CMOS technology can grow to a key technology in low-noise and high-speed applications, various amplifier stages, applied in literature, are compared. One, that fits as a current preamplifier for low-noise applications, is the current mirror. Starting from the basic current mirror, an enhanced current preamplifier is developed, that offers low-noise and high-speed operation. The suggested chip is realized in 0.12 μm CMOS technology and needs a chip area of 100 μm×280 μm. It consumes about 15 mW at a supply voltage of 1.5 V. The presented current preamplifier has a bandwidth of 750 MHz and a gain of 36 dB. The fields of application for current preamplifiers are, for instance, charge amplifiers, amplifiers for low-voltage differential signaling (LVDS) based point-to-point data links or preamplifiers for photodetectors.
Calibration-measurement unit for the automation of vector network analyzer measurements
Authors: Rolfes I. , Will B. , Schiek B.
Published: April 2010

Abstract. With the availability of multi-port vector network analyzers, the need for automated, calibrated measurement facilities increases. In this contribution, a calibration-measurement unit is presented which realizes a repeatable automated calibration of the measurement setup as well as a user-friendly measurement of the device under test (DUT). In difference to commercially available calibration units, which are connected to the ports of the vector network analyzer preceding a measurement and which are then removed so that the DUT can be connected, the presented calibration-measurement unit is permanently connected to the ports of the VNA for the calibration as well as for the measurement of the DUT. This helps to simplify the calibrated measurement of complex scattering parameters. Moreover, a full integration of the calibration unit into the analyzer setup becomes possible. The calibration-measurement unit is based on a multiport switch setup of e.g. electromechanical relays. Under the assumption of symmetry of a switch, on the one hand the unit realizes the connection of calibration standards like one-port reflection standards and two-port through connections between different ports and on the other hand it enables the connection of the DUT. The calibration-measurement unit is applicable for two-port VNAs as well as for multiport VNAs. For the calibration of the unit, methods with completely known calibration standards like SOLT (short, open, load, through) as well as self-calibration procedures like TMR or TLR can be applied.
Detection of transient disturbing signals on PC boards
Authors: Korte S. , Döring O. , Garbe H.
Published: April 2010

Abstract. This paper shows a possibility to visualize signal propagation in electronic circuits. Instead of using various galvanic measurement points all over the circuit, a test method is shown which measures the radiated field of the printed circuit board. By use of a 2-dimensional positionable field probe it is possible to get an overview over the signals running on the different parts of the PCB. In order to measure transient disturbing signals and distinguish them from normal device operation, problems of probe design and triggering need to be discussed.
Investigation of the behaviour of UWB protection elements against HPM signals
Authors: Brauer F. , Krzikalla R. , ter Haseborg J. L.
Published: April 2010

Abstract. The development of protection circuits against a variety of electromagnetic disturbances is important to assure the immunity to interferences of an electronic system. In this paper protection elements which were investigated under UWB conditions are now to be tested with HPM signals to achieve a comprehensive protection.
Transient measurement results of pulse propagation in large GTEM cells
Authors: Thye H. , Armbrecht G. , Koch M.
Published: April 2010

Abstract. This contribution deals with the results of a transient measurement campaign incorporating ultra-wideband (UWB) pulses applied to a large GTEM cell. The main purpose is to analyse the distortion effects on such a feeding pulse when transformed into a field pulse inside the cells testing volume. We will investigate if the TEM field distribution is interfered by multimode propagation, that may lead to location-dependent pulse distortion and ringing. Finally, conclusions on the applicability of GTEM cells for standardized transient EMC measurements will be drawn.
Cloud physical properties and empirical polarimetric measurements of rain signatures at C-Band
Authors: Steinert J. , Chandra M.
Published: April 2010

Abstract. Raindrops are one type of precipitation in stratiform and convective clouds. To get relationships for describing the raindrops two different methods were used. In the first way, the microphysical properties of the liquid hydrometeors were examined. For this the use of the Rayleigh approximation for small particles (raindrops at C-Band) and the drop size distribution by Ulbrich (Γ-DSD) lead to the calculation of the reflectivity at horizontal polarisation ZHH, the reflectivity at vertical polarisation ZVV and the differential reflectivity ZDR. In the second way, rain signatures were separated from polarimetric measurements. The database of these measurements consists of datasets measured by the dual polarimetric C-Band weather radar POLDIRAD (DLR, Oberpfaffenhofen). The aim of this study was then to combine and to compare the results from the real radar measurements against the theoretical calculations in the ZHH-ZDR plane. Based on these observations and calculations, scientific results for future practical use will be presented in form of empirical equations including ZHH-ZDR. Finally in form of scientific discussion, the ZHH-ZDR plane will be critically assessed for outstanding problems or issues.
Micro- and macroscopic simulation of periodic metamaterials
Authors: Schuhmann R. , Bandlow B. , Lubkowski G. , Weiland T.
Published: April 2010

Abstract. In order to characterize three-dimensional, left-handed metamaterials (LHM) we use electromagnetic field simulations of unit cells. For waves traveling in one of the main directions of the periodic LHM-arrays, the analysis is concentrated on the calculation of global quantities of the unit cells, such as scattering parameters or dispersion diagrams, and a careful interpretation of the results. We show that the concept of equivalent material values – which may be negative in a narrow frequency range – can be validated by large "global" simulations of a wedge structure. We also discuss the limitations of this concept, since in some cases the macroscopic behavior of an LHM cannot be accurately described by equivalent material values.
Determination of the permittivity of soils by use of double transmission measurements
Authors: Will B. , Gerding M.
Published: April 2010

Abstract. Delay time measurements, e.g. time domain reflectometry (TDR), are a well-established method for the measurement of permittivity of various materials, especially soils. However, common measurement systems only provide one average value of the dielectric constant along the length of the TDR probe. This contribution deals with an advanced application of the TDR principle, the so-called double transmission method, for the determination of the water content of soil along a probe. To apply the advanced TDR technique, a probe, realized by a combination of a transmission line and a dielectric obstacle, which can mechanically be moved along the probe, is used. The probe is inserted into the soil to measure the effective soil permittivity. Thus, the water content along the probe can be estimated by means of the effective permittivity. Based on the known mechanical position of the reflection at the end of the probe and the position of the obstacle, the measured delay time can be used as a measure for the effective dielectric constant of the environment surrounding the obstacle. Thus, it is possible to determine the effective dielectric constant with a spatial resolution given by the step size of the obstacle displacement.
Resolving longitudinal amplitude and phase information of two continuous data streams for high-speed and real-time processing
Authors: Guntoro A. , Glesner M.
Published: April 2010

Abstract. Although there is an increase of performance in DSPs, due to its nature of execution a DSP could not perform high-speed data processing on a continuous data stream. In this paper we discuss the hardware implementation of the amplitude and phase detector and the validation block on a FPGA. Contrary to the software implementation which can only process data stream as high as 1.5 MHz, the hardware approach is 225 times faster and introduces much less latency.
Analysis of iteration control for turbo decoders in turbo synchronization applications
Authors: Lehnigk-Emden T. , Wasenmüller U. , Gimmler C. , Wehn N.
Published: April 2010

Abstract. Wireless data transmission results in frequency and phase offsets of the signal in the receiver. In addition, the received symbols are corrupted by noise. Therefore, synchronization and channel coding are vital parts of each receiver in digital communication systems. By combining the phase and frequency synchronization with an advanced iterative channel decoder (inner loop) e.g. turbo codes in an iterative way (outer loop), the communications performance can be further increased. This principle is referred to as turbo synchronization. The energy consumption and the peak throughput of the system depend on the number of iterations for both loops. An advanced iteration control can decrease the mean number of needed iterations by detecting correctly decoded blocks. This leads to a dramatic energy saving or to an increase of throughput. In this paper we present a new stopping criterion for decodable blocks for turbo decoding in interrelation with turbo synchronization. Furthermore the implementation complexity of the turbo decoder is shown on a Xilinx FPGA.
CMOS low noise amplifiers for 1.575 GHz GPS applications
Authors: Isikhan M. , Richter A.
Published: April 2010

Abstract. This paper presents Low Noise Amplifier (LNA) versions designed for 1.575 GHz L1 Band Global Positioning System (GPS) applications. A 0.35 μm standard CMOS process is used for implementation of these design versions. Different versions are designed to compare the results, analyze some effects and optimize some critical performance criteria. On-chip inductors with different quality factors and a slight topology change are utilized to achieve this variety. It is proven through both on-wafer and on-PCB measurements that the LNA versions operate at a supply voltage range varying from 2.1 V to 3.6 V drawing a current of 10 mA and achieve a gain of 13 dB to 17 dB with a Noise Figure (NF) of 1.5 dB. Input referred 1 dB compression point (ICP) is measured as −5.5 dBm and −10 dBm for different versions.
Hybrid multilevel plane wave based near-field far-field transformation utilising combined near- and far-field translations
Authors: Schmidt C. H. , Eibert T. F.
Published: April 2010

Abstract. The radiation of large antennas and those operating at low frequencies can be determined efficiently by near-field measurement techniques and a subsequent near-field far-field transformation. Various approaches and algorithms have been researched but for electrically large antennas and irregular measurement contours advanced algorithms with low computation complexity are required. In this paper an algorithm employing plane waves as equivalent sources and utilising efficient diagonal translation operators is presented. The efficiency is further enhanced using simple far-field translations in combination with the expensive near-field translations. In this way a low complexity near-field transformation is achieved, which works for arbitrary sample point distributions and incorporates a full probe correction without increasing the complexity.
An experimental study on passive charge balancing
Authors: Sooksood K. , Stieglitz T. , Ortmanns M.
Published: April 2010

Abstract. This paper presents a simplified analysis of the electrode potential upon mismatched, biphasic stimulation using passive discharge techniques, e.g. by shortening of the electrodes. It turns out that especially for microelectrodes the required shorting intervals become as large as to limit a feasible stimulation interval. If no blocking capacitors can be used due to limited space and the degree of miniaturisation, the passive discharge even imposes severe risks to the surrounding tissue and the electrode.
Device reliability challenges for modern semiconductor circuit design – a review
Authors: Schlünder C.
Published: April 2010

Abstract. Product development based on highly integrated semiconductor circuits faces various challenges. To ensure the function of circuits the electrical parameters of every device must be in a specific window. This window is restricted by competing mechanisms like process variations and device degradation (Fig. 1). Degradation mechanisms like Negative Bias Temperature Instability (NBTI) or Hot Carrier Injection (HCI) lead to parameter drifts during operation adding on top of the process variations. The safety margin between real lifetime of MOSFETs and product lifetime requirements decreases at advanced technologies. The assignment of tasks to ensure the product lifetime has to be changed for the future. Up to now technology development has the main responsibility to adjust the technology processes to achieve the required lifetime. In future, reliability can no longer be the task of technology development only. Device degradation becomes a collective challenge for semiconductor technologist, reliability experts and circuit designers. Reliability issues have to be considered in design as well to achieve reliable and competitive products. For this work, designers require support by smart software tools with built-in reliability know how. Design for reliability will be one of the key requirements for modern product designs. An overview will be given of the physical device damage mechanisms, the operation conditions within circuits leading to stress and the impact of the corresponding device parameter degradation on the function of the circuit. Based on this understanding various approaches for Design for Reliability (DfR) will be described. The function of aging simulators will be explained and the flow of circuit-simulation will be described. Furthermore, the difference between full custom and semi custom design and therefore, the different required approaches will be discussed.