bluuebunny/crossref_metadata_2025 huggingface dataset:
What do satellite backscatter ultraviolet and visible spectrometers see over snow and ice? A study of clouds and ozone using the A-train
Authors: Vasilkov A. P. , Joiner J. , Haffner D. , Bhartia P. K. , Spurr R. J. D.
Published: April 2010

Abstract. In this paper, we examine how clouds over snow and ice affect ozone absorption and how these effects may be accounted for in satellite retrieval algorithms. Over snow and ice, the Aura Ozone Monitoring Instrument (OMI) Raman cloud pressure algorithm derives an effective scene pressure. When this scene pressure differs appreciably from the surface pressure, the difference is assumed to be caused by a cloud that is shielding atmospheric absorption and scattering below cloud-top from satellite view. A pressure difference of 100 hPa is used as a crude threshold for the detection of clouds that significantly shield tropospheric ozone absorption. Combining the OMI effective scene pressure and the Aqua MODerate-resolution Imaging Spectroradiometer (MODIS) cloud top pressure, we can distinguish between shielding and non-shielding clouds. To evaluate this approach, we performed radiative transfer simulations under various observing conditions. Using cloud vertical extinction profiles from the CloudSat Cloud Profiling Radar (CPR), we find that clouds over a bright surface can produce significant shielding (i.e., a reduction in the sensitivity of the top-of-the-atmosphere radiance to ozone absorption below the clouds). The amount of shielding provided by clouds depends upon the geometry (solar and satellite zenith angles) and the surface albedo as well as cloud optical thickness. We also use CloudSat observations to qualitatively evaluate our approach. The CloudSat, Aqua, and Aura satellites fly in an afternoon polar orbit constellation with ground overpass times within 15 min of each other. The current Total Ozone Mapping Spectrometer (TOMS) total column ozone algorithm (that has also been applied to the OMI) assumes no clouds over snow and ice. This assumption leads to errors in the retrieved ozone column. We show that the use of OMI effective scene pressures over snow and ice reduces these errors and leads to a more homogeneous spatial distribution of the retrieved total ozone.
Instrumentational operation and analytical methodology for the reconciliation of aerosol water uptake under sub- and supersaturated conditions
Authors: Good N. , Coe H. , McFiggans G.
Published: April 2010

Abstract. The methodology for the operation and calibration of hygroscopicity tandem differential mobility analyser (HTDMA) and cloud condensation nuclei counter (CCNc) for size resolved measurements of aerosol water uptake are presented. A state of the science aerosol thermodynamic model is used to benchmark the performance of the instruments. The performance, calibration and operation of the instruments is then demonstrated in the field.
Lag time determination in DEC measurements with PTR-MS
Authors: Taipale R. , Ruuskanen T. M. , Rinne J.
Published: April 2010

Abstract. The disjunct eddy covariance (DEC) method has emerged as a popular technique for micrometeorological flux measurements of volatile organic compounds (VOCs). It has usually been combined with proton transfer reaction mass spectrometry (PTR-MS), an online technique for VOC concentration measurements. However, the determination of the lag time between wind and concentration measurements has remained an important challenge. To address this conundrum, we studied the effect of different lag time methods on DEC fluxes. The analysis was based on both actual DEC measurements with PTR-MS and simulated DEC data derived from high frequency H2O measurements with an infrared gas analyzer. Conventional eddy covariance fluxes of H2O served as a reference in the DEC simulation. The individual flux measurements with PTR-MS were rather sensitive to the lag time methods, but typically this effect averaged out when the median fluxes were considered. The DEC simulation revealed that the maximum covariance method was prone to overestimation of the absolute values of fluxes. The constant lag time methods, one resting on a value calculated from the sampling flow and the sampling line dimensions and the other on a typical daytime value, had a tendency to underestimate. The visual assessment method and our new averaging approach based on running averaged covariance functions did not yield statistically significant errors and thus fared better than the habitual choice, the maximum covariance method. Given this feature and the potential for automatic flux calculation, we recommend using the averaging approach in DEC measurements with PTR-MS.
Differential optical absorption spectroscopy (DOAS) and air mass factor concept for a multiply scattering vertically inhomogeneous medium: theoretical consideration
Authors: Rozanov V. V. , Rozanov A. V.
Published: April 2010

Abstract. The Differential Optical Absorption Spectroscopy (DOAS) technique is widely used to retrieve amounts of atmospheric species from measurements of the direct solar light transmitted through the Earth's atmosphere as well as of the solar light scattered in the atmosphere or reflected from the Earth's surface. For the transmitted direct solar light the theoretical basis of the DOAS technique represented by the Beer-Lambert law is well studied. In contrast, scarcely investigated is the theoretical basis and validity range of the DOAS method for those cases where the contribution of the multiple scattering processes is not negligible. Our study is intended to fill this gap by means of a theoretical investigation of the applicability of the DOAS technique for the retrieval of amounts of atmospheric species from observations of the scattered solar light with a non-negligible contribution of the multiple scattering. Starting from the expansion of the intensity logarithm in the functional Taylor series we formulate the general form of the DOAS equation. The thereby introduced variational derivative of the intensity logarithm with respect to the variation of the gaseous absorption coefficient, which is often referred to as the weighting function, is demonstrated to be closely related to the air mass factor. Employing some approximations we show that the general DOAS equation can be rewritten in the form of the weighting function (WFDOAS), the modified (MDOAS), and the standard DOAS equations. For each of these forms a specific equation for the air mass factor follows which, in general, is not suitable for other forms of the DOAS equation. Furthermore, the validity range of the standard DOAS equation is quantitatively investigated using a suggested criterion of a weak absorption. The results presented in this study are intended to provide a basis for a better understanding of the applicability range of different forms of the DOAS equation as well as of the relationship between the air mass factor and the weighting function. To facilitate the understanding of the paper content for unexperienced reader we start our discussion considering in details the standard DOAS technique applied to the observations of the direct solar light transmitted through the Earth's atmosphere.
Validation of a modified AVHRR aerosol optical depth retrieval algorithm over Central Europe
Authors: Riffler M. , Popp C. , Hauser A. , Fontana F. , Wunderle S.
Published: April 2010

Abstract. The Advanced Very High Resolution Radiometer (AVHRR) carried on board the National Oceanic and Atmospheric Administration (NOAA) and the Meteorological Operational Satellite (MetOp) polar orbiting satellites is the only instrument offering more than 25 years of satellite data to analyse aerosols on a daily basis. The present study assessed a modified AVHRR aerosol optical depth τa retrieval over land. The initial approach has used a relationship between Sun photometer measurements from the Aerosol Robotic Network (AERONET) and the satellite data to post-process the retrieved τa. Herein a stand-alone procedure, which is more suitable for the pre-AERONET era, is presented. In addition, the estimation of surface reflectance, threshold values, and the aerosol model are adapted. The method's cross-platform applicability was tested by validating τa from NOAA-17 and NOAA-18 AVHRR at 15 AERONET sites in Central Europe (40.5° N–50° N, 0° E–17° E) from August 2005 to December 2007. Furthermore, the accuracy of the AVHRR retrieval was related to products from two newer instruments, the Medium Resolution Imaging Spectrometer (MERIS) on board the Environmental Satellite (ENVISAT) and the Moderate Resolution Imaging Spectroradiometer (MODIS) on board Aqua/Terra. Considering the linear correlation coefficient R, the AVHRR results were similar to those of MERIS with even lower root mean square error RMSE. Not surprisingly, MODIS, with its high spectral coverage gave the highest R and lowest RMSE. Regarding monthly averaged τa, the results were ambiguous. Focusing on small-scale structures, R was reduced for all sensors, whereas the RMSE solely for MERIS substantially increased. Regarding larger areas like Central Europe, the error statistics were similar to the individual match-ups. This was mainly explained with sampling issues. With the successful validation of AVHRR we are now able to concentrate on our large data archive dating back to 1985. This is a unique opportunity for both climate and air pollution studies over land surfaces.
Estimating drizzle drop size and precipitation rate using two-colour lidar measurements
Authors: Westbrook C. D. , Hogan R. J. , O'Connor E. J. , Illingworth A. J.
Published: April 2010

Abstract. A method to estimate the size and liquid water content of drizzle drops using lidar measurements at two wavelengths is described. The method exploits the differential absorption of infrared light by liquid water at 905 nm and 1.5 µm, which leads to a different backscatter cross section for water drops larger than ≈50 µm. The ratio of backscatter measured from drizzle samples below cloud base at these two wavelengths (the colour ratio) provides a measure of the median volume drop diameter D0. This is a strong effect: for D0=200 µm, a colour ratio of ≈6 dB is predicted. Once D0 is known, the measured backscatter at 905 nm can be used to calculate the liquid water content (LWC) and other moments of the drizzle drop distribution. The method is applied to observations of drizzle falling from stratocumulus and stratus clouds. High resolution (32 s, 36 m) profiles of D0, LWC and precipitation rate R are derived. The main sources of error in the technique are the need to assume a value for the dispersion parameter μ in the drop size spectrum (leading to at most a 35% error in R) and the influence of aerosol returns on the retrieval (≈10% error in R for the cases considered here). Radar reflectivities are also computed from the lidar data, and compared to independent measurements from a colocated cloud radar, offering independent validation of the derived drop size distributions.
Formaldehyde measurements by Proton Transfer Reaction – Mass Spectrometry (PTR-MS): correction for humidity effects
Authors: Vlasenko A. , Macdonald A. M. , Sjostedt S. J. , Abbatt J. P. D.
Published: April 2010

Abstract. Formaldehyde measurements can provide useful information about photochemical activity in ambient air, given that HCHO is formed via numerous oxidation processes. Proton transfer reaction mass spectrometry (PTR-MS) is an online technique that allows measurement of VOCs at the sub-ppbv level with good time resolution. PTR-MS quantification of HCHO is hampered by the humidity dependence of the instrument sensitivity, with higher humidity leading to loss of PTR-MS signal. In this study we present an analytical, first principles approach to correct the PTR-MS HCHO signal according to the concentration of water vapor in sampled air. The results of the correction are validated by comparison of the PTR-MS results to those from a Hantzsch fluorescence monitor which does not have the same humidity dependence. Results are presented for an intercomparison made during a field campaign in rural Ontario at Environment Canada's Centre for Atmospheric Research Experiments.
Total column CO2 measurements at Darwin, Australia – site description and calibration against in situ aircraft profiles
Authors: Deutscher N. M. , Griffith D. W. T. , Bryant G. W. , Wennberg P. O. , Toon G. C. , Washenfelder R. A. , Keppel-Aleks G. , Wunch D. , Yavin Y. , Allen N. T. , Blavier J.-F. , Jiménez R. , Daube B. C. , Bright A. V. , Matross D. M. , Wofsy S. C. , Park S.
Published: April 2010

Abstract. An automated Fourier Transform Spectroscopic (FTS) solar observatory was established in Darwin, Australia in August 2005. The laboratory is part of the Total Carbon Column Observing Network, and measures atmospheric column abundances of CO2 and O2 and other gases. Measured CO2 columns were calibrated against integrated aircraft profiles obtained during the TWP-ICE campaign in January–February 2006, and show good agreement with calibrations for a similar instrument in Park Falls, Wisconsin. A clear-sky low airmass relative precision of 0.1% is demonstrated in the CO2 and O2 retrieved column-averaged volume mixing ratios. The 1% negative bias in the FTS XCO2 relative to the World Meteorological Organization (WMO) calibrated in situ scale is within the uncertainties of the NIR spectroscopy and analysis.
Cellular neural networks for motion estimation and obstacle detection
Authors: Feiden D. , Tetzlaff R.
Published: April 2010

Abstract. Obstacle detection is an important part of Video Processing because it is indispensable for a collision prevention of autonomously navigating moving objects. For example, vehicles driving without human guidance need a robust prediction of potential obstacles, like other vehicles or pedestrians. Most of the common approaches of obstacle detection so far use analytical and statistical methods like motion estimation or generation of maps. In the first part of this contribution a statistical algorithm for obstacle detection in monocular video sequences is presented. The proposed procedure is based on a motion estimation and a planar world model which is appropriate to traffic scenes. The different processing steps of the statistical procedure are a feature extraction, a subsequent displacement vector estimation and a robust estimation of the motion parameters. Since the proposed procedure is composed of several processing steps, the error propagation of the successive steps often leads to inaccurate results. In the second part of this contribution it is demonstrated, that the above mentioned problems can be efficiently overcome by using Cellular Neural Networks (CNN). It will be shown, that a direct obstacle detection algorithm can be easily performed, based only on CNN processing of the input images. Beside the enormous computing power of programmable CNN based devices, the proposed method is also very robust in comparison to the statistical method, because is shows much less sensibility to noisy inputs. Using the proposed approach of obstacle detection in planar worlds, a real time processing of large input images has been made possible.
Active miniature radio frequency field probe
Authors: Glasmachers A.
Published: April 2010

Abstract. For the measuring of the electromagnetic interference (e.g. on men) of RF fields produced by mobile communication equipment field probes are required with high spatial resolution and high sensitivity. Available passive probes show good results with respect to bandwidth and low field distortion, but do not provide the required sensitivity and dynamic range. A significant limitation for active miniature probes is the power supply problem, because batteries cannot be used. Therefore the effect of high impedance connection lines is examined by a numerical field simulation. Different approaches for the design of an active probe are discussed, a favourable solution with a logarithmic demodulator is implemented and measuring results are presented.
Verringerung des Parameterraums von IP unter Verwendung von Parameterabhängigkeiten
Authors: Jerinić V. , Müller D.
Published: April 2010

Abstract. Um eine Wiederverwendung in verschiedenen Anwendungen zu ermöglichen, verfügen Intellectual Properties (IP) häufig über einen umfangreichen Parametersatz. Auf der einen Seite erlaubt die extensive Verwendung von Parametern die Anpassung von IP an verschiedene Spezifikationen. Andererseits vergrößert jeder Parameter den Parameterraum, wodurch es praktisch unmöglich wird, die korrekte Funktion der IP für alle Parameterkombinationen zu verifizieren. Es wird eine Methode vorgestellt, die, basierend auf vorgegebenen Abhängigkeiten der Parameter untereinander, den Parameterraum in orthogonale Subräume, sogenannte Parameter-Domänen, unterteilt, wobei ungültige Parameterkombinationen entfernt werden. Durch diesen Schritt kann der Parameterraum zum Teil erheblich verkleinert werden. Durch die Verwendung von orthogonalen Subräumen werden Verifikationsumgebungen, wie z.B. Specman EliteTM von Verisity, die Stimuli und Parameterzuweisungen pseudozufällig erzeugen k¨onnen, wirkungsvoll unterstützt, indem mehrfache Simulationen gleichwertiger Zuweisungen verhindert werden. In order to be reused in different applications IP are usually parameterized.While a rich parameter set enables users to customize IP to their needs, verification complexity is increased by enlarging the parameter space with every additional parameter. In this work, a graph-based approach to splitting the parameter space into orthogonal subspaces on the basis of defined parameter interdependences is proposed. By utilizing so-called parameter domain graphs, invalid parameter configurations are removed from the parameter space. Verification environments with the capability to automatically generate pseudo-random parameter combinations, e.g. Specman EliteTM von Verisity, may create parameter combinations which are virtually equal. This can be avoided by using orthogonal subspaces.
A curvature-corrected CMOS bandgap reference
Authors: Mitrea O. , Popa C. , Manolescu A. M. , Glesner M.
Published: April 2010

Abstract. This paper presents a CMOS bandgap reference that employs a curvature correction technique for compensating the nonlinear voltage temperature dependence of a diode connected BJT. The proposed circuit cancels the first and the second order terms in the VBE(T ) expansion by using the current of an autopolarizedWidlar source and a small correction current generated by a MOSFET biased in weak inversion. The voltage reference has been fabricated in a 0.35µm 3Metal/2Poly CMOS technology and the chip area is approximately 70µm × 110µm. The measured temperature coefficient is about 10.5 ppm/K over a temperature range of 10– 90°C while the power consumption is less than 1.4mW.
Exploration of dual supply voltage logic synthesis in state-of-the-art ASIC design flows
Authors: Mahnke T. , Stechele W. , Embacher M. , Hoeld W.
Published: April 2010

Abstract. Dual supply voltage scaling (DSVS) for logiclevel power optimization at the has increasingly attracted attention over the last few years. However, mainly due to the fact that the most widely used design tools do not support this new technique, it has still not become an integral part of real-world design flows. In this paper, a novel logic synthesis methodology that enables DSVS while relying entirely on standard tools is presented. The key to this methodology is a suitably modeled dual supply voltage (DSV) standard cell library. A basic evaluation of the methodology has been carried out on a number of MCNC benchmark circuits. In all these experiments, the results of state-of-the-art powerdriven single supply voltage (SSV) logic synthesis have been used as references in order to determine the true additional benefit of DSVS. Compared with the results of SSV power optimization, additional power reductions of 10% on average have been achieved. The results prove the feasibility of the new approach and reveal its greater efficiency in comparison with a well-known dedicated DSVS algorithm. Finally, the methodology has been applied to an embedded microcontroller core in order to further explore the potentials and limitations of DSVS in an existing industrial design environment.
Calibration of vector network analyzers on the basis of the LRR-method
Authors: Rolfes I. , Schiek B.
Published: April 2010

Abstract. The LRR method for the calibration of vector network analyzers is presented. This method belongs to the self calibration procedures where the calibration circuits might be partly unknown. The LRR calibration circuits are all of equal mechanical length in contrast to the well known TRL calibration, which needs a line-standard with a different length than the other calibration standards. For the LRR method it is thus not necessary to displace the connectors of the vector network analyzer during calibration in order to contact the calibration structures. The calibration circuits mainly consist of reflective networks that have to be placed at three consecutive positions. As the algorithm accounts for different distances between the reflective networks, the circuits are easy to realize. The robust functionality of the LRR method is confirmed by measurements.
Efficient MAP-algorithm implementation on programmable architectures
Authors: Kienle F. , Michel H. , Gilbert F. , Wehn N.
Published: April 2010

Abstract. Maximum-A-Posteriori (MAP) decoding algorithms are important HW/SW building blocks in advanced communication systems due to their ability to provide soft-output informations which can be efficiently exploited in iterative channel decoding schemes like Turbo-Codes. Multi-standards demand flexible implementations on programmable platforms. In this paper we analyze a quantized turbo-decoder based on a Max-Log-MAP algorithm with Extrinsic Scaling Factor (ESF). Its communication performance approximate to a Turbo-Decoder with a Log-MAP algorithm and is less sensitive to quantization effects. We present Turbo-Decoder implementations on state-of-the-art DSPs and show that only a Max-Log-MAP implementation fulfills a throughput requirement of ~2 Mbit/s. The negligible overhead for the ESF implementation strengthen the use of Max-Log-MAP with ESF implementation on programmable platforms.
A Comparison of current SDRAM types: SDR, DDR, and RDRAM
Authors: Klehn B. , Brox M.
Published: April 2010

Abstract. The ever increasing demand for bandwidth of computer-systems lead to several standards of SDRAMs. This article compares SDR, DDRI, DDRII, and RDRAM systems. Besides the overall basic innovations, differences will be discussed. Topics like architecture, interfaces, and modules are described.
ESD compact-simulation: investigation of inverter failure
Authors: Drüen S. , Esmark K. , Stadler W. , Gossner H. , Schmitt-Landsiedel D.
Published: April 2010

Abstract. An ESD failure occurring inside the core circuitry known as “inverter failure" will be presented and analysed in this paper. The compact model utilised for this investigation is shortly presented. It will be shown that not only properties of the failed structure are relevant, but also surrounding circuitry. So the gate of an inverter will be connected during the simulations in diverse ways to VDD and VSS. The different possibilities of influence of pre drivers can be appraised in this way. In order to achieve a detailed understanding of the individual failure, it is necessary to include ambient circuitry as well as parasitics like resistors and capacitances.
Impact of near field dispersion on time domain susceptibility tests
Authors: Sabath F. , Garbe H.
Published: April 2010

Abstract. This paper considers the effect of changes of the waveform parameters over the distance. The objective is to show the near field effects on transient radiation and how near the equipment under test can be located to an antenna without significant changes of the width or rise time of the field pulse. It is shown that the well known frequency domain estimation models fail because the dimension of antenna systems and the wave propagation lead to a special kind of dispersion. The importance of this near field dispersion for practical applications is demonstrated by both theoretical considerations and measurements with a half impulse radiation antenna.
Efficient extrapolation methods for electro- and magnetoquasistatic field simulations
Authors: Clemens M. , Wilke M. , Weiland T.
Published: April 2010

Abstract. In magneto- and electroquasi-static time domain simulations with implicit time stepping schemes the iterative solvers applied to the large sparse (non-)linear systems of equations are observed to converge faster if more accurate start solutions are available. Different extrapolation techniques for such new time step solutions are compared in combination with the preconditioned conjugate gradient algorithm. Simple extrapolation schemes based on Taylor series expansion are used as well as schemes derived especially for multi-stage implicit Runge-Kutta time stepping methods. With several initial guesses available, a new subspace projection extrapolation technique is proven to produce an optimal initial value vector. Numerical tests show the resulting improvements in terms of computational efficiency for several test problems. In quasistatischen elektromagnetischen Zeitbereichsimulationen mit impliziten Zeitschrittverfahren zeigt sich, dass die iterativen Lösungsverfahren für die großen dünnbesetzten (nicht-)linearen Gleichungssysteme schneller konvergieren, wenn genauere Startlösungen vorgegeben werden. Verschiedene Extrapolationstechniken werden für jeweils neue Zeitschrittlösungen in Verbindung mit dem präkonditionierten Konjugierte Gradientenverfahren vorgestellt. Einfache Extrapolationsverfahren basierend auf Taylorreihenentwicklungen werden ebenso benutzt wie speziell für mehrstufige implizite Runge-Kutta-Verfahren entwickelte Verfahren. Sind verschiedene Startlösungen verfügbar, so erlaubt ein neues Unterraum-Projektion- Extrapolationsverfahren die Konstruktion eines optimalen neuen Startvektors. Numerische Tests zeigen die aus diesen Verfahren resultierenden Verbesserungen der numerischen Effizienz.
Comparison of errors and stability in FDTD and FVTD
Authors: Leuchtmann P. , Fumeaux C. , Baumann D.
Published: April 2010

Abstract. The methods of finite-difference time-domain (FDTD) and finite-volume time-domain (FVTD) are well known techniques for solving electromagnetic problems. While for FDTD a number of commercial codes is available there are only few based on FVTD. However, FVTD has advantages since it allows completely unstructured meshes. This paper 1. deals with the principle errors made in both approaches and 2. gives a theoretical comparison of the (local) stability of an FVTD scheme as opposed to the conventional Yee-scheme commonly used in FDTD. Finally the principles of a new FVTD program is presented. Its capabilities are demonstrated by the field of an antenna array.
A hybrid method combining the FDTD and a time domain boundary-integral equation marching-on-in-time algorithm
Authors: Becker A. , Hansen V.
Published: April 2010

Abstract. In this paper a hybrid method combining the FDTD/FIT with a Time Domain Boundary-Integral Marching-on-in-Time Algorithm (TD-BIM) is presented. Inhomogeneous regions are modelled with the FIT-method, an alternative formulation of the FDTD. Homogeneous regions (which is in the presented numerical example the open space) are modelled using a TD-BIM with equivalent electric and magnetic currents flowing on the boundary between the inhomogeneous and the homogeneous regions. The regions are coupled by the tangential magnetic fields just outside the inhomogeneous regions. These fields are calculated by making use of a Mixed Potential Integral Formulation for the magnetic field. The latter consists of equivalent electric and magnetic currents on the boundary plane between the homogeneous and the inhomogeneous region. The magnetic currents result directly from the electric fields of the Yee lattice. Electric currents in the same plane are calculated by making use of the TD-BIM and using the electric field of the Yee lattice as boundary condition. The presented hybrid method only needs the interpolations inherent in FIT and no additional interpolation. A numerical result is compared to a calculation that models both regions with FDTD.
Geometry-based channel modelling of MIMO channels in comparison with channel sounder measurements
Authors: Del Galdo G. , Haardt M. , Schneider C.
Published: April 2010

Abstract. In this paper we propose a flexible geometrybased propagation model for wireless communications developed at Ilmenau University of Technology. The IlmProp comprises a geometrical representation of the environment surrounding the experiment and a precise representation of the transmitting and receiving antennas. The IlmProp is capable of simulating Multi-User MIMO scenarios and includes a complete collection of tools to analyze the synthetic channels. In order to assess the potentials as well as the limits of our channel simulator we reconstruct the scenario encountered in a recent measurement campaign at Ilmenau University of Technology leading to synthetic data sets similar to the ones actually measured. The measurements have been collected with the RUSK MIMO multi-dimensional channel sounder. From the comparisons of the two channel matrices it is possible to derive useful information to improve the model itself and to better understand the physical origins of small-scale fading. In particular the effects of the different parameters on the synthetic channel have been studied in order to assess the sensibility of the model. This analysis shows that the correct positioning of a small number of scatterers is enough to achieve frequency selectiveness as well as specific traits of the channel statistics. The size of the scattering clusters, the number of scatterers per cluster, and the Rician K-factor can be modified in order to tune the channel statistics at will. To obtain higher levels of time variance, moving scatterers or time dependent reflection coefficients must be introduced.
Applicability of new radio technologies for advanced UMTS networks
Authors: Dekorsy A. , Schacht M. , Brueck S. , Fischer G.
Published: April 2010

Abstract. An expanded effort is under the way to support the evolution of UMTS (Universal Mobile Telecommunication System). Apart from delivering high data rates, future UMTS releases will also require to provide high network performance in terms of system capacity, low radiated power, and high coverage. Well promising performance-enhancing technologies are smart antennas as well as multiuser detection. Although these new radio technologies have recently been subject to intense research, main UMTS network integration aspects with their specific constraints have been neglected in many cases. Especially the interaction with UMTS radio resource control being required to meet Quality of Service (QoS) constraints has to be included to assess the applicability of these technologies for UMTS. In this paper, we study the interaction of beamforming concepts as well as multiuser detection with load and power control. We also work out UMTS specific constraints like signal-to-interference-plus-noise ratio (SINR) operating points, pilot power pollution or channel estimation, all strongly limiting network performance. Results are shown for capacity gains and power reduction for all beamforming concepts of interest as well as linear multiuser detection schemes. The results show that fix as well as user-specific beamforming significantly improves network performance gains in downlink. In uplink multiuser detection indicates fairly modest system capacity gains, while it reduces tremendously mobile station power.
On UWB beamforming
Authors: Kaiser T.
Published: April 2010

Abstract. Ultra-Wideband (UWB) communication systems and Multi-Input-Multi-Output (MIMO) techniques rank among the few emerging key technologies in wireless communications. For that reason the marriage of these two complementary approaches should deserve attention. Apparently, the extremely large ultra-wide bandwidth creates rich multipath diversity which calls, at a first glance, additional antenna elements into question. However, another point of view is as follows. The attenuation by solid materials usually increases with increasing frequency; e.g. frequencies above, say, 10 GHz are considered to be blocked by walls etc. Since UWB can occupy more than 7 GHz of bandwidth (according to FCC regularisation) the performance of a communication link can be physically extended only by adding spatial information, i.e. multiple antennas, even if such extension may play a minor role. From this point of view UWB& MIMO presents an upper physical bound for indoor communications and is therefore at least worth to be investigated. In order to see the forest for the trees, we will focus in this limited contribution on beamforming among all alternative MIMO techniques (like space time coding or spatial multiplexing).
Entropie analysis of floating car data systems
Authors: Gössel F. , Michler E. , Wrase B.
Published: April 2010

Abstract. The knowledge of the actual traffic state is a basic prerequisite of modern traffic telematic systems. Floating Car Data (FCD) systems are becoming more and more important for the provision of actual and reliable traffic data. In these systems the vehicle velocity is the original variable for the evaluation of the current traffic condition. As real FCDsystems are operating under conditions of limited transmission and processing capacity the analysis of the original variable vehicle speed is of special interest. Entropy considerations are especially useful for the deduction of fundamental restrictions and limitations. The paper analyses velocity-time profiles by means of information entropy. It emphasises in quantification of the information content of velocity-time profiles and the discussion of entropy dynamic in velocity-time profiles. Investigations are based on empirical data derived during field trials. The analysis of entropy dynamic is carried out in two different ways. On one hand velocity differences within a certain interval of time are used, on the other hand the transinformation between velocities in certain time distances was evaluated. One important result is an optimal sample-rate for the detection of velocity data in FCD-systems. The influence of spatial segmentation and of different states of traffic was discussed.
Ein 10 bit 10MS/s Low-Power AD-Converter in 0.11mm2
Authors: Muthers D. , Tielert R.
Published: April 2010

Abstract. Ein 10 bit 10MS/s Analog-Digital- Wandler mit niedriger Leistungaufnahme von 8,4mW wurde implementiert. Der geringe Flächenbedarf von 0,11mm2 macht diesen Wandler besonders geeignet f¨ur Multikanalanwendungen. Um die Anforderungen von 10 bit, 10 MS/s möglichst effizient zu erfüllen wurde eine zyklische Wandlerarchitektur gewählt, die in einem 0,18μm-CMOSProzess mit MIM-Kondensatoren implementiert wurde. Der entworfene ADC wurde in 21 parallelen Kanälen auf einem mixed-signal-Chip zusammen mit digitalen Filtern, vier RISC-CPUs und I/O-Schaltungen implementiert. A 10 bit 10MS/s Analog to Digital Converter, consuming a power of 8,4mW, has been implemented. Due to the small area of 0,11mm2 this ADC is highly suited for multichannel implementations. A cyclic converter architecture is best suited for this application, being implemented in a 0,18μm CMOS process with MIM-capacitors. The designed ADC was implemented in an array of 21 channels on a mixed signal chip together with digital filters, four RISC-CPUs and I/O circuitry.
Circuit architecture derivation starting from a formal requirements specification considering a DDS as example
Authors: Garbe H. , Richter R. , Jentschel H.-J.
Published: April 2010

Abstract. Based on a formal specification of a direct digital synthesis (DDS) and assuming the availability of a set of possible circuit architectures we derive a customised system configuration. We calculate the design parameters that can be used for the specification to synthesise the circuit components. We show how the derived parameters and the selected IC technology influence the complexity of the circuit implementation.
Robust statistics for ionosphere data: from Rawer’s nombre de corrélation (1951) to maximum-depth regression technique (1998)*
Authors: Taubenheim J.
Published: April 2010

Abstract. Contrast between “normal" and “disturbed" states of the ionosphere early induced the suggestion to present ionospheric data with the aid of a “robust" (i.e. outlierresistant) statistic, namely, the median instead of the conventional arithmetic mean. K. Rawer, in 1951, defined on this concept a nombre de corrélation, which proved to be well resistant to misleading effects of outlier data when analyzing correlations between ionospheric and related data. Various attempts over many years, however, to extend this idea towards a robust fitting of regression models to outliercontaminated data, remained unsatisfactory. Only a few years ago, a mathematically correct and unambiguous technique for robust regression has been reached by Belgian authors (Rousseeuw and Hubert, 1998), based on the new paradigm of “maximum data depth", which is exemplified here for ionospheric data presentation.
Screening attenuation of coaxial cables determined in GTEM-cells
Authors: Knobloch A. , Garbe H.
Published: April 2010

Abstract. This paper describes the determination of the screening attenuation with a GTEM cell. An analytical part gives the link between the voltage at the cell port and the total radiated power. The next section investigates the optimal cable setup in the cell. With a measurement of the common mode current on the cable and a simulation of the radiation resistance the loop antenna characteristic of the cable setup could be verified. It is shown that the use of ferrit cores decrease the difference between the maximum and the minimum screening attenuation. The determination of great screening attenuation could be improved with the use of N-type measurement cables. A comparison between this GTEM cell method and the standard methods shows a good agreement.
Measuring the upset of CMOS and TTL due to HPM-signals
Authors: Esser N. , Smailus B.
Published: April 2010

Abstract. To measure the performance of electronic components when stressed by High Power Microwave signals a setup was designed and tested which allows a well-defined voltage signal to enter the component during normal operation, and to discriminate its effect on the component. The microwave signal is fed to the outside conductor of a coaxial cable and couples into the inner signal line connected to the device under test (DUT). The disturbing HF-signal is transferred almost independent from frequency to maintain the pulse shape in the time domain. The configuration designed to perform a TEM-coupling within a 50 Ohm system prevents the secondary system from feeding back to the primary system and, due to the geometrical parameters chosen, the coupling efficiency is as high as 50–90%. Linear dimensions and terminations applied allow for pulses up to a width of 12ns and up to a voltage level of 4–5 kV on the outside conductor. These pulse parameters proved to be sufficient to upset the DUTs tested so far. In more than 400 measurements a rectangular pulse of increasing voltage level was applied to different types of CMOS and TTL until the individual DUT was damaged. As well the pulse width (3, 6 or 12 ns) and its polarity were varied in single-shot or repetitive-shot experiments (500 shots per voltage at a repetition rate of 3 Hz). The state of the DUT was continuously monitored by measuring both the current of the DUT circuit and that of the oscillator providing the operating signal for the DUT. The results show a very good reproducibility within a set of identical samples, remarkable differences between manufacturers and lower thresholds for repetitive testing, which indicates a memory effect of the DUT to exist for voltage levels significantly below the single-shot threshold.
Review of singular potential integrals for method of moments solutions of surface integral equations
Authors: Tzoulis A. , Eibert T. F.
Published: April 2010

Abstract. Accurate evaluation of singular potential integrals is essential for successful method of moments (MoM) solutions of surface integral equations. In mixed potential formulations for metallic and dielectric scatterers, kernels with 1/R and r1/R singularities must be considered. Several techniques for the treatment of these singularities will be reviewed. The most common approach solves the MoM source integrals analytically for specific observation points, thus regularizing the integral. However, in the case of r1/R a logarithmic singularity remains for which numerical evaluation of the testing integral is still difficult. A recently by Yl¨a-Oijala and Taskinen proposed remedy to this issue is discussed and evaluated within a hybrid finite element – boundary integral technique. Convergence results for the MoM coupling integrals are presented where also higher-order singularity extraction is considered.
Measurement of the Shielding Effectiveness of Conducting Enclosures with the Image Theory
Authors: Paoletti U. , Garbe H. , John W.
Published: April 2010

Abstract. Two simple techniques for the measurement of the shielding efficiency for the electric field of a symmetric enclosure are presented.y They allow measurements in the symmetry plane of the enclosure without disturbances b the cables. Measurements in near and far field regions are possible. Comparisons with simulation results are shown. Both techniques are particularly suitable for the evaluation of numerical techniques. Limits of the concept of shielding efficiency of enclosures at high frequencies are also briefly discussed.
Radiation Efficient Unidirectional Low-Profile Slot Antenna Elements for X-Band Application
Authors: Löcker C. , Vaupel T. , Eibert T. F.
Published: April 2010

Abstract. Slots in metallic ground planes are very promising candidates for conformal antenna applications. However, a low-profile unidirectional antenna requires a back reflector close to the slot and the resulting stripline feed causes strong excitation of parallel-plate modes. In this contribution, we consider unidirectional reflector-backed slot configurations with parallel-plate mode suppression by shorting pins. Starting from a parametric study with respect to shorting pin location and back reflector distance, we present a stripline-fed rectangular slot element with radiation efficiency of more than 80% and a bandwidth of about 5% at centre frequency 10GHz. A careful optimisation of shorting pin locations guarantees reliable parallel-plate mode suppression without deteriorating the slot radiation behaviour. Coupling coefficients between parallel and aligned rectangular slot elements are presented. For increased bandwidth applications, a bow-tie slot element with about 8% bandwidth and radiation efficiency of close to 80% is proposed.
Microwave sensors for detection of wild animals during pasture mowing
Authors: Patrovsky A. , Biebl E. M.
Published: April 2010

Abstract. More than 400000 wild animals are killed or severely injured every year during spring time pasture mowing. Conventional methods for detection and removal or expulsion of animals before mowing are either inefficient or very time-consuming. The first really working method is based on a pyro-detector which senses the temperature contrast between the animals body and the surrounding pasture. Unfortunately, the detection reliability of this sensor decreases with increasing ambient temperature and strong sunlight, i.e. for typical weather conditions, when pasture is mowed, especially around noon. In this paper, a detector is presented that exhibits complementary behaviour. It works best during dry conditions (i.e. around noon), but has a tendency to false alarms when dew is present (i.e. morning and evening). The sensor is based on a commercial, low-cost Doppler module at 24GHz. It senses the difference of radar cross section between the animals body (high water content, specular reflection) and the pasture (low water content, diffuse reflection). The signal is analysed by means of a non-linear Wigner time-frequency transformation. Experimental results are presented for a laboratory setup as well as for measurement in actual spring-time pasture. The results prove that a microwave sensor is capable of reliably detecting animals of the size of a fawn even if it is covered by a layer of pasture.
Computation of currents induced by ELF electric fields in anisotropic human tissues using the Finite Integration Technique (FIT)
Authors: Motrescu V. C. , van Rienen U.
Published: April 2010

Abstract. In the recent years, the task of estimating the currents induced within the human body by environmental electromagnetic fields has received increased attention from scientists around the world. While important progress was made in this direction, the unpredictable behaviour of living biological tissue made it difficult to quantify its reaction to electromagnetic fields and has kept the problem open. A successful alternative to the very difficult one of performing measurements is that of computing the fields within a human body model using numerical methods implemented in a software code. One of the difficulties is represented by the fact that some tissue types exhibit an anisotropic character with respect to their dielectric properties. Our work consists of computing currents induced by extremely low frequency (ELF) electric fields in anisotropic muscle tissues using in this respect, a human body model extended with muscle fibre orientations as well as an extended version of the Finite Integration Technique (FIT) able to compute fully anisotropic dielectric properties.
Evolution of Electromagnetics in the 19th Century
Authors: Lindell I. V.
Published: April 2010

Abstract. Steps leading to the present-day electromagnetic theory made in the 19th Century are briefly reviewed. The progress can be roughly divided in two branches which are called Continental and British Electromagnetics. The former was based on Newton's action-at-a-distance principle and French mathematics while the latter grew from Faraday's contact-action principle, the concept of field lines and physical analogies. Maxwell's field theory and its experimental verification marked the last stage in the process.
Turbo Equalization Of Nonlinear ISI-channels Using High Rate FEC Codes
Authors: Siegrist M. , Schorr T. , Dittrich A. , Sauer-Greff W. , Urbansky R.
Published: April 2010

Abstract. Turbo equalization is a widely known method to cope with low signal to noise ratio (SNR) channels corrupted by linear intersymbol interference (ISI) (Berrou and Galvieux, 1993; Hagenauer et al., 1997). Recently in this workshop it was reported that also for nonlinear channels a remarkable turbo decoding gain can be achieved (Siegrist et al., 2001). However, the classical turbo equalization relies on code rates at 1/3 up to 1/2 which makes it quite unattractive for high rate data transmission. Considering the potential of iterative equalization and decoding, we obtain a considerable turbo decoding gain also for high rate codes of less than 7% redundancy by using punctured convolutional codes and block codes.
Robustness of IFDMA as Air Interface Candidate for Future High Rate Mobile Radio Systems
Authors: Frank T. , Klein A. , Costa E. , Schulz E.
Published: April 2010

Abstract. The Interleaved Frequency Division Multiple Access (IFDMA) scheme is a candidate for next generation mobile radio systems. IFDMA is based on compression, repetition and subsequent user dependent frequency shift of a modulated signal. As in OFDMA, multiple access is enabled by the assignment of overlapping but mutually orthogonal subcarriers to each user. It provides various advantages such as low peak to average power ratio, orthogonality of the signals of different users even for transmission over a time dispersive channel and low complexity. However, IFDMA is sensitive to frequency offsets. In this paper, a derivation of IFDMA based on a generalised OFDMA signal model with specific precoding and specific subcarrier allocation is presented. Moreover, simulation results showing the robustness properties of IFDMA against frequency errors are given.