bluuebunny/crossref_metadata_2025 huggingface dataset:
The horizontal resolution of MIPAS
Authors: von Clarmann T. , De Clercq C. , Ridolfi M. , Höpfner M. , Lambert J.-C.
Published: April 2010

Abstract. Limb remote sensing from space provides atmospheric composition measurements at high vertical resolution while the information is smeared in the horizontal domain. The horizontal components of two-dimensional (altitude and along-track coordinate) averaging kernels of a limb retrieval constrained to horizontal homogeneity can be used to estimate the horizontal resolution of limb retrievals. This is useful for comparisons of measured data with modeled data, to construct horizontal observation operators in data assimilation applications or when measurements of different horizontal resolution are intercompared. We present these averaging kernels for retrievals of temperature, H2O, O3, CH4, N2O, HNO3 and NO2 from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) high-resolution limb emission spectra. The horizontal smearing of a MIPAS retrieval in terms of full width at half maximum of the rows of the horizontal averaging kernel matrix varies typically between about 200 and 350 km for most species, altitudes and atmospheric conditions. The range where 95% of the information originates from varies from about 260 to 440 km for these cases. This information spread is smaller than the MIPAS horizontal sampling, i.e. MIPAS data are horizontally undersampled, and the effective horizontal resolution is driven by the sampling rather than the smearing. The point where the majority of the information originates from is displaced from the tangent point towards the satellite by typically less than 10 km for trace gas profiles and about 50 to 100 km for temperature, with a few exceptions for uppermost altitudes. The geolocation of a MIPAS profile is defined as the tangent point of the middle line of sight in a MIPAS limb scan. The majority of the information displacement with respect to this nominal geolocation of the measurement is caused by the satellite movement and the geometrical displacement of the actual tangent point as a function of the elevation angle.
First eddy covariance flux measurements by PTR-TOF
Authors: Müller M. , Graus M. , Ruuskanen T. M. , Schnitzhofer R. , Bamberger I. , Kaser L. , Titzmann T. , Hörtnagl L. , Wohlfahrt G. , Karl T. , Hansel A.
Published: April 2010

Abstract. The recently developed PTR-TOF instrument was evaluated to measure methanol fluxes emitted from grass land using the eddy covariance method. The high time resolution of the PTR-TOF allowed storing full mass spectra up to m/z 315 with a frequency of 10 Hz. Three isobaric ions were found at a nominal mass of m/z 33 due to the high mass resolving power of the PTR-TOF. Only one of the three peaks contributed to eddy covariance fluxes. The exact mass of this peak agrees well with the exact mass of protonated methanol (m/z 33.0335). The eddy covariance methanol fluxes measured with PTR-TOF were compared to virtual disjunct eddy covariance methanol fluxes simultaneously measured with a conventional PTR-MS. The methanol fluxes from both instruments show excellent agreement.
Determination of an effective trace gas mixing height by differential optical absorption spectroscopy (DOAS)
Authors: Zhou B. , Yang S. N. , Wang S. S. , Wagner T.
Published: April 2010

Abstract. A new method for the determination of the Mixing layer Height (MH) by the DOAS technique is proposed in this article. The MH can be retrieved by a combination of active DOAS and passive DOAS observations of atmospheric trace gases; here we focus on observations of NO2. Because our observations are sensitive to the vertical distribution of trace gases, we refer to the retrieved layer height as an ''effective trace gas mixing height'' (ETMH). By analyzing trace gas observations in Shanghai over one year (1017 hourly means in 93 days in 2007), the retrieved ETMH was found to range between 0.1 km and 2.8 km (average is 0.78 km); more than 90% of the measurements yield an ETMH between 0.2 km and 2.0 km. The seasonal and diurnal variation of the ETMH shows good agreement with mixing layer heights derived from meteorological observations. We investigated the relationship of the derived ETMH to temperature and wind speed and found correlation coefficients of 0.65 and 0.37, respectively. Also the wind direction has an impact on the measurement to some extent. Especially in cases when the air flow comes from highly polluted areas and the atmospheric lifetime of NO2 is long (e.g. in winter), the NO2 concentration at high altitudes over the measurement site can be enhanced, which leads to an overestimation of the ETMH. Enhanced NO2 concentrations in the free atmosphere and heterogeneity within the mixing layer can cause additional uncertainties. Our method could be easily extended to other species like e.g. SO2, HCHO or Glyoxal. Simultaneous studies of these molecules could yield valuable information on their respective atmospheric lifetimes.
Determination of water-insoluble light absorbing matter in rainwater using polycarbonate membrane filters and photometric detection
Authors: Engström J. E. , Leck C.
Published: April 2010

Abstract. A method for determination of water-insoluble light absorbing matter in rainwater has been developed. After collection the rainwater samples were filtered using polycarbonate membrane filter in the laboratory. After drying the filter in filtered air, the amount of water-insoluble light absorbing matter (soot) on the filters was determined with photometry at a wavelength of 555 nm. The precision for the method was better than 10% calculated as relative standard deviation. The overall loss of soot due to adsorption during collection and filtration was 22±2%. The detection limit was estimated to 0.025 in optical density, or 2 ng/ml expressed as a concentration assuming a filtration volume of 30 ml. Analysis of environmental samples have been successfully performed with the described method at the Maldives Climate Observatory Hanimaadhoo and Nepal Climate Observatory. At Maldives the average soot concentration in rain was 0.048 μg/ml and at the Nepal obseravtory 0.086 μg/ml.
Springtime Arctic ground-based spectroscopy of O3 and related trace gases at Eureka, Canada – Part 1: Evaluation of the analysis method and comparison with infrared measurements
Authors: Farahani E. , Strong K. , Mittermeier R. L. , Fast H. , Van Roozendael M. , Fayt C.
Published: April 2010

Abstract. For the first time in spring 1999 the ground-based UV-visible zenith-sky measurements of stratospheric gases were performed at Environment Canada's Arctic Stratospheric Ozone Observatory (ASTRO) located at Eureka, Nunavut, Canada (80.05° N, 86.42° W, 610 m a.s.l.). The University of Toronto UV-visible ground-based spectrometer (UT-GBS) has been deployed for nine years afterwards at Eureka to measure ozone and NO2 total columns by using sunlight scattered from the zenith sky during spring, when the conditions leading to polar ozone depletion develop. During spring 2000, elevated OClO slant column densities were also measured for the first time. First dedicated analysis of UT-GBS measurements applying two independent differential optical absorption spectroscopy algorithms was performed on spectra recorded during spring 2000. The resulting ozone and NO2 total columns agreed to 4% and 5% or better, respectively. Also, first four years of UT-GBS results (1999–2003) were compared with those made by ozonesondes and by the Meteorogical Service of Canada Fourier transform infrared spectrometer (MSC FTS) at ASTRO, which has been operated by Canada's Department of Environment for measuring the total columns of several stratospheric gases. The comparison of UT-GBS and MSC FTS ozone total columns proved to be better than 5% for the periods when both instruments were viewing similar air masses.
Validation of water vapour profiles (version 13) retrieved by the IMK/IAA scientific retrieval processor based on full resolution spectra measured by MIPAS on board Envisat
Authors: Milz M. , Clarmann T. v. , Bernath P. , Boone C. , Buehler S. A. , Chauhan S. , Deuber B. , Feist D. G. , Funke B. , Glatthor N. , Grabowski U. , Griesfeller A. , Haefele A. , Höpfner M. , Kämpfer N. , Kellmann S. , Linden A. , Müller S. , Nakajima H. , Oelhaf H. , Remsberg E. , Rohs S. , Russell III J. M. , Schiller C. , Stiller G. P. , Sugita T. , Tanaka T. , Vömel H. , Walker K. , Wetzel G. , Yokota T. , Yushkov V. , Zhang G.
Published: April 2010

Abstract. Vertical profiles of stratospheric water vapour measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) between September 2002 and March 2004 and retrieved with the IMK/IAA scientific retrieval processor were compared to a number of independent measurements in order to estimate the bias and to validate the existing precision estimates of the MIPAS data. The independent instruments were: the Halogen Occultation Experiment (HALOE), the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS), the Improved Limb Atmospheric Spectrometer-II (ILAS-II), the Polar Ozone and Aerosol Measurement (POAM III) instrument, the Middle Atmospheric Water Vapour Radiometer (MIAWARA), the Michelson Interferometer for Passive Atmospheric Sounding, balloon-borne version (MIPAS-B), the Airborne Microwave Stratospheric Observing System (AMSOS), the Fluorescent Stratospheric Hygrometer for Balloon (FLASH-B), the NOAA frostpoint hygrometer, and the Fast In Situ Hygrometer (FISH). In the stratosphere there is no clear indication of a bias in MIPAS data, because the independent measurements in some cases are drier and in some cases are moister than the MIPAS measurements. Compared to the infrared measurements of MIPAS, measurements in the ultraviolet and visible have a tendency to be high, whereas microwave measurements have a tendency to be low. The results of χ2-based precision validation are somewhat controversial among the comparison estimates. However, for comparison instruments whose error budget also includes errors due to uncertainties in spectrally interfering species and where good coincidences were found, the χ2 values found are in the expected range or even below. This suggests that there is no evidence of systematically underestimated MIPAS random errors.
The impact of surface reflectance variability on total column differential absorption LiDAR measurements of atmospheric CO2
Authors: Lawrence J. P. , Leigh R. J. , Monks P. S.
Published: April 2010

Abstract. The remote sensing technique, total column differential absorption LiDAR (TC-DIAL) has been proposed in a number of feasibility studies as a suitable method for making total column measurements of atmospheric CO2 from space. Among the sources of error associated with TC-DIAL retrievals from space is an undefined modulation of the received signals resulting from the variability in the Earth's surface reflectance between the LiDAR pulses. This source of uncertainty is investigated from a satellite perspective by the application of a computer model for spaceborne TC-DIAL instruments. The simulations are carried out over Europe and South America using modified MODIS surface reflectance maps and a DIAL configuration similar to that suggested for the proposed ESA A-SCOPE mission. A positive bias of 0.01 ppmv in both continental test sets is observed using 10 Hz pulse repetition frequency and 200 km integration distance. This bias is a consequence of non-linearity in the DIAL equation, and in particular regions such as the Alps and over certain coastlines it contributes to positive errors of between 0.05 and 0.16 ppmv for 200 and 50 km integration distances. These retrieval errors are defined as lower bound estimates owing to the likely resolution difference between the surface reflectance data and the expected surface heterogeneity observed by a DIAL instrument.
A guide for upper-air reference measurements
Authors: Immler F. , Dykema J. , Gardiner T. , Whiteman D. N. , Thorne P. W. , Vömel H.
Published: April 2010

Abstract. The accurate monitoring of climate change imposes strict requirements upon observing systems, in particular regarding measurement accuracy and long-term stability. Currently available data records of the essential climate variables (temperature-T, geopotential-p, humidity-RH, wind, and cloud properties) in the upper-air generally fail to fulfill such requirements. This raises serious issues about the ability to detect, quantify and understand recent climate changes and their causes. GCOS is currently implementing a Reference Upper-Air Network (GRUAN) in order to fill this major void within the global observing system. As part of the GRUAN implementation plan we provide herein fundamental guidelines for establishing and maintaining reference quality atmospheric observations which are based on principal concepts of metrology, in particular traceability. It is argued that the detailed analysis of the uncertainty budget of a measurement technique is the critical step for achieving this goal. As we will demonstrate with an example, detailed knowledge of the calibration procedures and data processing algorithms are required for determining the uncertainty of each individual data point. Of particular importance is the careful assessment of the uncertainties introduced by correction schemes adjusting for systematic effects.
Speaker tracking with a microphone array using Kalman filtering
Authors: Bechler D. , Grimm M. , Kroschel K.
Published: April 2010

Abstract. In this publication a method for tracking a speaker with acoustical information by means of a microphone array is presented. A sound source localization algorithm based on the time delays of arrival of sound waves in microphone pairs provides initial position estimates. These significantly varying estimates are spatially filtered by an adaptive Kalman filter to obtain a smoothed trajectory of the speaker’s movement. Experimental results with real data are presented for a variety of scenarios recorded in a noisy and reverberant office room environment.
Planar millimeter wave radar frontend for automotive applications
Authors: Grubert J. , Heyen J. , Metz C. , Stange L. C. , Jacob A. F.
Published: April 2010

Abstract. A fully integrated planar sensor for 77 GHz automotive applications is presented. The frontend consists of a transceiver multichip module and an electronically steerable microstrip patch array. The antenna feed network is based on a modified Rotman-lens and connected to the array in a multilayer approach offering higher integration. Furthermore, the frontend comprises a phase lock loop to allow proper frequency-modulated continuous wave (FMCW) radar operation. The latest experimental results verify the functionality of this advanced frontend design featuring automatic cruise control, precrash sensing and cut-in detection. These promising radar measurements give reason to a detailed theoretical investigation of system performance. Employing commercially available MMIC various circuit topologies are compared based on signal-tonoise considerations. Different scenarios for both sequential and parallel lobing hint to more advanced sensor designs and better performance. These improvements strongly depend on the availability of suitable MMIC and reliable packaging technologies. Within our present approach possible future MMIC developments are already considered and, thus, can be easily adapted by the flexible frontend design. Es wird ein integrierter planarer Sensor für 77 GHz Radaranwendungen vorgestellt. Das Frontend besteht aus einem Sende- und Empfangs-Multi-Chip-Modul und einer elektronisch schwenkbaren Antenne. Das Speisenetzwerk der Antenne basiert auf einer modifizierten Rotman- Linse. Für eine kompakte Bauweise sind Antenne und Speisenetzwerk mehrlagig integriert. Weiterhin umfasst das Frontend eine Phasenregelschleife für eine präzise Steuerung des frequenzmodulierten Dauerstrichradars. Die aktuellen Messergebnisse bestätigen die Funktionalit¨at dieses neuartigen Frontend-Designs, das automatische Geschwindigkeitsregelung, Kollisionswarnung sowie Nahbereichsüberwachung ermöglicht. Die Qualität der Messergebnisse hat weiterführende theoretische Untersuchungen über die potenzielle Systemleistungsfähigkeit motiviert. Unter Berücksichtigung von kommerziell erhältlichenMMICs werden verschiedene Schaltungstopologien auf der Grundlage des Signal-Rausch-Verhältnisses verglichen. Sowohl für sequenzielle als auch für parallele Ansteuerung der Antennenkeulen wird eine deutliche Leistungssteigerung ermittelt. Diese Verbesserungen hängen maßgeblich von der Verfügbarkeit geeigneter MMICs und einer zuverlässigen Aufbau- und Verbindungstechnik ab. Das vorliegende Frontend-Konzept kann auf Grund seiner Flexibilität leicht an derlei zukünftige Entwicklungen angepasst werden.
Telemetric surface acoustic wave sensor for humidity
Authors: Dierkes M. , Hilleringmann U.
Published: April 2010

Abstract. Surface acoustic wave sensors consist of a piezoelectric substrate with metal interdigital transducers (IDT) on top. The acoustic waves are generated on the surface of the substrate by a radio wave, as it is well known in band pass filters. The devices can be used as wireless telemetric sensors for temperature and humidity, transmitting the sensed signal as a shift of the sensor’s resonance frequency.
Accurate modeling of high frequency microelectromechanical systems (MEMS) switches in time- and frequency-domainc
Authors: Coccetti F. , Dressel W. , Russer P. , Pierantoni L. , Farina M. , Rozzi T.
Published: April 2010

Abstract. In this contribution we present an accurate investigation of three different techniques for the modeling of complex planar circuits. The em analysis is performed by means of different electromagnetic full-wave solvers in the timedomain and in the frequency-domain. The first one is the Transmission Line Matrix (TLM) method. In the second one the TLM method is combined with the Integral Equation (IE) method. The latter is based on the Generalized Transverse Resonance Diffraction (GTRD). In order to test the methods we model different structures and compare the calculated Sparameters to measured results, with good agreement.
First harmonic injection locking of 24-GHz-oscillators
Authors: Kühn M. R. , Biebl E. M.
Published: April 2010

Abstract. An increasing number of applications is proposed for the 24 GHz ISM-band, like automotive radar systems and short-range communication links. These applications demand for oscillators providing moderate output power of a few mW and moderate frequency stability of about 0.5%. The maximum oscillation frequency of low-cost off-theshelf transistors is too low for stable operation of a fundamental 24GHz oscillator. Thus, we designed a 24 GHz first harmonic oscillator, where the power generated at the fundamental frequency (12 GHz) is reflected resulting in effective generation of output power at the first harmonic. We measured a radiated power from an integrated planar antenna of more than 1mW. Though this oscillator provides superior frequency stability compared to fundamental oscillators, for some applications additional stabilization is required. As a low-cost measure, injection locking can be used to phase lock oscillators that provide sufficient stability in free running mode. Due to our harmonic oscillator concept injection locking has to be achieved at the first harmonic, since only the antenna is accessible for signal injection. We designed, fabricated and characterized a harmonic oscillator using the antenna as a port for injection locking. The locking range was measured versus various parameters. In addition, phase-noise improvement was investigated. A theoretical approach for the mechanism of first harmonic injection locking is presented.
A planar hybrid transceiving mixer at 76.5GHz for automotive radar applications
Authors: Olbrich M. O. , Grübl A. , Raßhofer R. H. , Biebl E. M.
Published: April 2010

Abstract. A growing number of applications for radar systems in automobiles demands for low-cost radar front-ends. A planar monostatic radar front-end is particularly suited for low cost applications as it uses only one antenna for transmission and reception and, thus, minimizes the needed chip area. Generally, in a standard homodyne radar a radio-frequency (RF) signal generated by an oscillator is used for both, the transmitted signal and the local oscillator (LO). Well controlled distribution of the input power between antenna and mixer is crucial. A transceiving mixer at 76.5GHz is presented, where this distribution is done by use of a rat-race coupler. In a conventional transceiver the oscillator signal is split into the transmitted and in the LO signal by a directional coupler. A second directional coupler is needed in order to merge the received and the LO signal at the mixer. In our design the purpose of splitting and merging the signals is realized with only one coupler. Elimination of the second coupler reduces losses significantly. The received signal is down-converted to the intermediate frequency (IF) by use of a balanced mixer. For small relative speed in a CW-Doppler-radar or short distance in a FMCWradar the IF is very small. Therefore 1/f noise is a significant value. In order to achieve good 1/f noise characteristics, Schottky diodes were used. The diodes were flip-chip bonded onto a microstrip circuit on a Al2O3 substrate. \\ The assembled transceiver was measured on-waver. An input power of 7 dBm was applied. The measured output power was 3 dBm and the conversion loss 9 dB. A noise figure of 15.3 dB was measured at 100 kHz.
Resonance circuits for adiabatic circuits
Authors: Schlachta C. , Glesner M.
Published: April 2010

Abstract. One of the possible techniques to reduces the power consumption in digital CMOS circuits is to slow down the charge transport. This slowdown can be achieved by introducing an inductor in the charging path. Additionally, the inductor can act as an energy storage element, conserving the energy that is normally dissipated during discharging. Together with the parasitic capacitances from the circuit a LCresonant circuit is formed.
Adaptive Buskodierverfahren zur verlustleistungseffizienten Datenübertragung auf Bussen digitaler Systeme
Authors: Kretzschmar C. , Siegmund R. , Müller D.
Published: April 2010

Abstract. In diesem Beitrag wird ein Überblick ber transitionsmindernde Buskodierverfahren zur verlustleistungsminimierten Datenübertragung zwischen Modulen digitaler Systeme gegeben. Ein neues adaptives Verfahren, das Adaptive Minimum Weight Codes (AMWC) Verfahren wird vorgestellt, welches Datenworte auf einen Code mit minimalem Gewicht unter Nutzung dynamisch rekonfigurierbarer Codetabellen abbildet. Aufgrund der Anpassbarkeit der Kodiervorschrift benötigt es keine Kenntnis statistischer Parameter der zu übertragenden Datenströme und eignet sich deshalb insbesondere zur Kodierung von Datenströmen mit über der Zeit veränderlichen Parametern. Im Gegensatz zu anderen bislang publizieren adaptiven Verfahren, welche aufgrund ihres enormen Eigenverlustleistungsanteiles nicht effizient implementierbar sind, besitzt die Implementierung von AMWC einen geringeren Hardwareoverhead und verändert das Systembusinterface nicht. Der Beitrag stellt theoretische Grundlagen vor und gibt eine hardwareeffiziente Implementierung an. Experimentelle Untersuchungen ergaben eine Reduktion der Schaltaktivität um 38%.In this paper state-of-the-art transition-minimizing bus encoding schemes for power-efficient data transmission between modules of digital systems are summarized. A new adaptive scheme, the Adaptive Minimum Weight Codes (AMWC) is presented which maps data words unambiguously on a minimum weight code using dynamically reconfigurable code tables. Due to its adaptability our scheme does not require a priori knowledge about statistical parameters of data streams to be transmitted. Therefore it is especially suited for data streams with time-varying parameters. Unlike other adaptive techniques presented to date, which are infeasible to implement into hardware due to their tremendous overhead in self dissipated power, the implementation of our encoding technique requires less interface. The fundamentals of the encoding scheme and a hardware-efficient implementation are given. Experimental results showed a reduction in bus transition activity of up to 38%. hardware overhead and does not modify the system bus
Resonant charging
Authors: Saas C. , Nossek J. A.
Published: April 2010

Abstract. It has been shown (Athas et al., 1994) that adiabatic switching can significantly reduce the dynamic power dissipation in an integrated circuit. Due to the overhead in the realization of adiabatic logic blocks (Saas et al., 2000) the best results are achieved when it is used only for charging dominant loads in an integrated circuit (Voss and Glessner, 2001). It has been demonstrated (Saas et al., 2001) that a multi stage driver is needed for minimal power dissipation. In this article a complete three stage driver including the generation of oscillating supply is described. To obtain a minimal power dissipation during synchronization the resonant frequency has to be constant. Therefore the waveforms for the logic states of the signal and the realization of a single stage differ from those presented in (Saas et al., 2001). In the H-SPICE simulations losses of the inductor are taken into account. This allows to estimate the power reduction that is achievable in a real system.
Resonant 90 degree shifter generator for 4-phase trapezoidal adiabatic logic
Authors: Bargagli-Stoffi A. , Amirante E. , Fischer J. , Iannaccone G. , Schmitt-Landsiedel D.
Published: April 2010

Abstract. Many adiabatic logic families make use of multi phase trapezoidal or sinusoidal power clocks to recover the energy stored in the load capacitances. A key aspect for the evaluation of the performance of adiabatic logic is then the study of a system that includes the power clock generator. A four-phase trapezoidal power clock generator, according to the requirements of the most promising architectures, namely the ECRL and PFAL, has been designed and simulated. The proposed circuit, realized with a double-well 0.25 µm CMOS technology and external inductors, is a resonant generator designed to oscillate at a frequency of 7 MHz, which is within the optimum frequency range for adiabatic circuits realized with this CMOS technology. The generator has been simulated with the equivalent load of fifty 1-bit adders and the operating behavior of a 4-bit adder has been evaluated. The key aspects of a generator for adiabatic logic are its power consumption and the phase relationships between its output signals. The proposed generator has a conversion efficiency higher than 80%, and it is robust with respect to variations of technology parameters. The four power supplies exhibit the correct relationship of phase also in the presence of no equally distributed loads.
Konzeption und Entwurf einer auf Petri-Netzen basierenden programmierbaren Kontrollschaltung
Authors: Baur H. , Pfleiderer H.-J.
Published: April 2010

Abstract. Petri-Netze eignen sich aufgrund der direkten Darstellbarkeit von Nebenläufigkeiten und leistungsfähiger Analyseverfahren zur Beschreibung von komplexen Kontrollabläufen. Die hier vorgestellte PNDU (Petri Net Decision Unit) ist ein programmierbarer Hardware- Interpreter für Kontrollalgorithmen, die durch Petri-Netze beschrieben werden. Die Petri-Netze werden kodiert in einem Speicher abgelegt und unter Einbeziehung der Eingangssignale und interner Zustände nach einem festgelegten Algorithmus abgearbeitet. Der implizite Wartezustand der PNDU motiviert in Hinblick auf den Einsatz in eingebetteten, batteriebetriebenen Geräten eine asynchrone Realisierung. Die PNDU wurde mit VHDL als synchrone und vergleichend dazu als selbstgetaktete Schaltung entworfen.
Precision level measurement based on time-domain reflection (TDR) measurements
Authors: Gerding M. , Musch T. , Schiek B.
Published: April 2010

Abstract. A system for a high precision multi target level measurement based on guided microwave pulses is presented. A wide-band technique based on time-domain reflectometry (TDR) in combination with a TEM-waveguide as the probe fulfils the requirements of mm-precision level measurements in tanks. The coaxial waveguide provides very low dispersion for wide-band signals. Inside the coaxial waveguide the different fluids with their specific dielectric constants influence the waveguide’s characteristic impedance, so that reflections take place at each discontinuity and separating layer respectively. A second very important requirement of the system is a high resolution. Thin layers (< 10 mm) should be measured reliably. For that reason the pulse width must be sufficiently small. In this case a pulse width about 100 ps is suitable. It is obvious, that a high bandwidth of the whole system is necessary to provide the precision and the resolution. One further requirement is a nearly jitter free generation of two pulse trains with slightly different pulse repetition rates. These pulse trains are used for sequential sampling. The following analog to digital conversion of the received signal occurs at a relatively slow rate, in order to allow an A/D conversion with a high resolution.
Analytische Modellierung des Zeitverhaltens und der Verlustleistung von CMOS-Gattern
Authors: Geißler R. , Pfleiderer H.-J.
Published: April 2010

Abstract. In modernen CMOS-Technologien werden die Verzögerungszeit, die Ausgangsflankensteilheit und der Querstrom eines Gatters sowohl durch die Lastkapazität als auch durch die Steilheit des Eingangssignals beeinflusst. Die heute verwendeten Technologiebibliotheken beinhalten Tabellenmodelle mit 25 oder mehr Stützpunkten dieser Abhängigkeiten, woraus durch Interpolation die benötigten Zwischenwerte berechnet werden. Bisherige Versuche, analytische Modelle abzuleiten beruhten darauf, den Querstrom zu vernachlässigen oder Transistorströme als stückweise linear anzunähern. Der hier gezeigte Ansatz beruht auf einer näherungsweisen Lösung der Differentialgleichung, die aus den beiden Transistorströmen und einer Lastkapazität besteht und damit das Schaltverhalten eines Inverters beschreibt. Mit wenigen Technologieparametern können daraus für einen beliebig dimensionierten Inverter die für eine Timing- und Verlustleistungsanalyse notwendigen Größen berechnet werden. Das Modell erreicht bei einem Vergleich zu Referenzwerten aus SPICE Simulationen eine Genauigkeit von typischerweise 5%.In modern CMOS-technologies the gate delay, output transition time and the short-circuit current depend on the capacitive load as well as on the input transition time. Today’s technology libraries use table models with 25 or more samples for these dependencies. Intermediate values have to be calculated through interpolation. Attempts to derive analytical models are based on neglecting the short-circuit current or approximating it by piecewise linear functions. The approach shown in this paper provides an approximate solution for the differential equation describing the dynamic behavor of an inverter circuit. It includes the influence of both transistor currents and a single load capacitance. The required values for timing and power analysis can be calculated with a small set of technology parameters for an arbitrary designed inverter. Compared to reference values extracted from SPICE simulations, the model achieves a typical precision of 5%.
A new BIST scheme for low-power and high-resolution DAC testing
Authors: Li H. , Eckmueller J. , Sattler S. , Eichfeld H. , Weigel R.
Published: April 2010

Abstract. A BIST scheme for testing on chip DAC is presented in this paper. We discuss the generation of on chip testing stimuli and the measurement of digital signals with a narrow-band digital filter. We validate the scheme with software simulation and point out the possibility of ADC BIST with verified DACicus-journals.
MOS capacitances used in mixed-signal circuits and their operative range
Authors: Kraus W. , Stelzig B. , Tille T. , Schmitt-Landsiedel D.
Published: April 2010

Abstract. To avoid additional layers for high linearity capacitances in modern CMOS process families, compensated depletion mode MOS capacitances can be used. As shown in previous publications, these MOS capacitances are suitable for low voltage applications. But there exist limitations concerning the linearity of these capacitances. In this work, the impact of the nonlinearity of the capacitances on different kinds of circuits is investigated. Several examples will be discussed to show how to choose the right capacitance topology.
Scattering in remote sensing in the visible and microwave spectral range and in traffic control
Authors: Böttger U. , Kühne R. , Thiessenhusene K.-U.
Published: April 2010

Abstract. The treatment of scattering processes in remote sensing for interpretation of satellite data is demonstrated in the visible and microwave spectral range comparing the two spectral ranges. Analogies and distinctions in the treatment of the scattering processes are shown. Based on this cognition an approach for traffic simulation is outlined. Simulating the traffic of a part of a city, a whole city or a larger area in an acceptable time is one of the tasks in recent traffic research. One possible approach is the areal treatment of the road network. That means that single streets are not resolved but are introduced into simulations only by parameters that correspond to a specific traffic area resistance. The aim of this work is to outline such a possibility using experiences obtained from the theory of radiative transport to simulate scattering processes and applying them to the very complex system of traffic simulation.
Effects of nonlinearities from the analog frequency-ramps of the fast network-analyser
Authors: Schulte B. , Musch T. , Schiek B.
Published: April 2010

Abstract. The developed network analyser with four ports allows very fast measurements of S-parameters in comparison with a conventional network analyser. This is possible because highly linear analogue frequency ramps are used. Thus the settling times of stepped frequency sweeps of conventional analysers are eliminated. The required high linearity and high stability of the frequency ramps is achieved by using fractional divider phase locked loop circuits. For a practical realization it is necessary to accept small nonlinearities for the linear analogue frequency ramps. For this reason investigations were performed to clarify effects of small nonlinearities on the measurement precision. Nonlinearities are willingly implemented by programming the fractional frequency ramps accordingly. The gained expertise allows for a further improvement of measurement accuracy and dynamic range.
Numerical analysis of the interaction between a GTEM-cell and a device under test using a hybrid method
Authors: Zellerhoff M. , Klinkenbusch L.
Published: April 2010

Abstract. Due to the increasing importance of EMC problems through the last years there is a great interest in measurement devices such as GTEM-cells (Giga(Hz)- TEM cells). They promise to allow compact and low-cost emission- as well as susceptibility tests up to very high frequencies. Expensive measurement procedures in open-area test sites or within semi-anechoic chambers would become obsolete in many cases. To estimate the quality and reliability of GTEM-cell measurements it is necessary to have detailed knowledge about the processes within the cell and, in particular, about the interactions between the cell and the DUT (device under test). Due to the high frequency and the cell’s dimensions a purely numerical simulation while using standard techniques such as Finite Element Method, Method of Moments (MoM) or the Finite-Differ-Time-Domain (FDTD) method is inefficient and unnecessary since the GTEM-cell is a mostly empty homogeneous TEM-waveguide. Analytical models allow only the investigation of empty cells. As will be outlined in the following, a suitable way to reduce the numerical complexity of the general problem is the use of a hybrid method, such as the combination of a modal analysis with the MoM.
The influence of electromagnetic singularities on an active dipole antenna within a cavity
Authors: Gronwald F.
Published: April 2010

Abstract. We study the influence of both the electromagnetic source singularity and electromagnetic cavity resonances on the current distribution of a dipole antenna within a rectangular cavity. These two types of electromagnetic singularities are triggered by the radius of the dipole antenna and the quality factor of the enclosing cavity, respectively. The key element of our investigation is a novel representation of the electromagnetic Green’s function for a lossy rectangular cavity. It allows to directly obtain the current distribution on the antenna by means of the method of moments. As a result it is recognized that a dominating source singularity, i.e., a small antenna radius, can inhibit resonating effects, even if a cavity resonance is excited and the quality factor of the cavity is high.
On the matrices of capacitance and inductance coefficients for lossless homogeneous multiconductor transmission lines
Authors: Reibiger A.
Published: April 2010

Abstract. Using results from the theory of planar fields and complex functions it is shown that for lossless homogeneous multiconductor transmission lines the computation of the matrices of capacitance and inductance coefficients can be reduced to the solution of some special Dirichlet boundary value problems. Additionally, a function theoretic proof is given for the relationship LC = ϵµE between these matrices.
Modelling and characterization of a travelling-wave electro-optic modulator on InP
Authors: Pascher W. , den Besten J. H. , Caprioli D. , van Dijk R. , Leijtens X. J. M. , Smit M. K.
Published: April 2010

Abstract. A fast travelling-wave Mach-Zehnder modulator is modelled and designed using a rigorous vectorial analysis. In order to investigate propagation characteristics, velocity and microwave loss, the semiconductor layer stack and the lossy electrodes are modelled using the method of lines. The microwave field distribution is determined, design curves are derived and the cross-sectional dimensions of the modulator are optimized. The loss of the fabricated device agrees very well with small signal measurements up to 40 GHz and HFSS simulations.
Stability and conservation properties of transient field simulations using FIT
Authors: Schuhmann R. , Weiland T.
Published: April 2010

Abstract. Time domain simulations for high-frequency applications are widely dominated by the leapfrog timeintegration scheme. Especially in combination with the spatial discretization approach of the Finite Integration Technique (FIT) it leads to a highly efficient explicit simulation method, which in the special case of Cartesian grids can be regarded to be computationally equivalent to the Finite Difference Time Domain (FDTD) algorithm. For stability reasons, however, the leapfrog method is restricted to a maximum stable time step by the well-known Courantcriterion, and can not be applied to most low-frequency applications. Recently, some alternative, unconditionally stable techniques have been proposed to overcome this limitation, including the Alternating Direction Implicit (ADI)-method. We analyze such schemes using a transient modal decomposition of the electric fields. It is shown that stability alone is not sufficient to guarantee correct results, but additionally important conservation properties have to be met. Das Leapfrog-Verfahren ist ein weit verbreitetes Zeitintegrationsverfahren für transiente hochfrequente elektrodynamischer Felder. Kombiniert mit dem räumlichen Diskretisierungsansatz der Methode der Finiten Integration (FIT) führt es zu einer sehr effizienten, expliziten Simulationsmethode, die im speziellen Fall kartesischer Rechengitter als äquivalent zur Finite Difference Time Domain (FDTD) Methode anzusehen ist. Aus Stabilitätsgründen ist dabei die Zeitschrittweite durch das bekannte Courant-Kriterium begrenzt, so dass das Leapfrog- Verfahren für niederfrequente Probleme nicht sinnvoll angewendet werden kann. In den letzten Jahren wurden alternativ einige andere explizite oder “halb-implizite" Zeitbereichsverfahren vorgeschlagen, u.a. das “Alternating Direction Implicit" (ADI)-Verfahren, die keiner Beschränkung des Zeitschritts aus Stabilitätsgründen unterliegen. Es zeigt sich aber, dass auch diese Methoden im niederfrequenten Fall nicht zu sinnvollen Simulationsergebnissen führen. Wie anhand einer transienten Modalanalyse der elektrischen Felder in einem einfachen 2D-Beispiel deutlich wird, ist die Ursache dafür die Verletzung wichtiger physikalischer Erhaltungseigenschaften durch ADI und verwandte Methoden.
Integral equation analysis of complex (M)MIC-structures with optimized system matrix decomposition and novel quadrature techniques
Authors: Vaupel T. , Hansen V.
Published: April 2010

Abstract. Using integral equation methods for the analysis of complex (M)MIC structures, the computation and storage effort for the solution of the linear systems of equations with their fully populated matrices still forms the main bottleneck. In the last years, remarkable improvements could be achieved by means of diakoptic methods and related preconditiners. In this contribution, we present a method based on the optimized decomposition of the system matrix depending on the circuit topology. The system matrix is splitted in a densely populated matrix and a mainly blockdiagonal matrix with overlapping submatrices. The latter matrix is used for the generation of high performance preconditioners within Krylov subspace methods using sparsified matrix storage methods, adaptive Cholesky decompositions and optimized forward/backward substitutions. Furthermore, we present an integration technique using a complete analytical treatment for the strongly oscillating parts of the spectral domain integrands allowing the analysis of very large structures as compared to the wavelength.
Kopplung eines auf der Momentenmethode basierenden Computerprogramms mit einem FEM-Algorithmus zur Berechnung von elektromagnetischen Streuproblemen im medizinischen Bereich
Authors: Schick M. , Landstorfer F. M.
Published: April 2010

Abstract. Am Beispiel der Verkopplung von medizinischen Geräten über den menschlichen Körper werden elektromagnetische Störphänomene im Klinikbereich betrachtet. Für die Berechnung dieser komplexen Szenarien wird zum einen die Momentenmethode (MoM) verwendet, die sich in besonderem Maße für die Berücksichtigung metallischer Strukturen und offener Streuprobleme eignet, und zum anderen die Methode der Finiten Elemente (FEM), mit der die Eigenschaften des menschlichen Körpers besser berücksichtigt werden können. Mit Hilfe des Äquivalenzprinzips lässt sich das Gesamtproblem in zwei Teile zerlegen, in ein inneres und in ein äußeres. Der Außenraum wird dabei mit der MoM behandelt und das Innere, d.h. der Körper mit der FEM. Die Kopplung der beiden Methoden erfolgt an der Körperoberfläche über äquivalente Oberflächenströme. Durch Lösen des resultierenden linearen Gleichungssystems für das gesamte Problem lassen sich dann die Oberflächenströme und die über die Kontinuitätsgleichung miteinander verknüpften elektromagnetischen Felder bestimmen.
Over-the-air demonstration of spatial multiplexing at high data rates using real-time base-band processing
Authors: Jungnickel V. , Haustein T. , Forck A. , Krueger U. , Pohl V. , von Helmolt C.
Published: April 2010

Abstract. Over-the-air transmission experiments with a realtime MIMO test-bed are reported. We describe in principle a hardware architecture for spatial multiplexing at high data rates, discuss in detail the implementation on a hybrid FPGA/DSP platform and show measured bit error rates from indoor transmission experiments. Per-antenna rate control and joint transmission are enabled as well using an ideal feed-back link. A functional test of these new techniques is described while detailed transmission experiments are still ongoing.
Realistic antenna modeling for MIMO systems in microcell scenarios
Authors: Waldschmidt C. , Kuhnert C. , Fügen T. , Wiesbeck W.
Published: April 2010

Abstract. This paper shows the potential of MIMO in cellular systems, where small handheld devices are used for the terminals. A complete model of a MIMO communication link is used to integrate accurate antenna modelling into MIMO system simulations. All different effects of mutual coupling between closely spaced antennas are considered. The efficiency or power budget respectively of the antenna arrays in the terminals, which are influenced by mutual coupling effects, is taken into account. Capacity simulation results based on a channel obtained from ray-tracing simulations are shown with cellular phones with up to three Inverted-F antennas.
Testen komplexer digitaler Schaltungen mit Python
Authors: Reichör S. , Hueber G. , Hagelauer R. , Lindorfer M.
Published: April 2010

Abstract. Die Verifikation von digitalen Schaltungen nimmt heutzutage einen bedeutenden Stellenwert ein. In diesem Paper wird ein Weg beschrieben, der die Erstellung und Wartung von funktionalen Testbenches für digitale Designs unterstützt. Für viele Projekte übersteigt der zeitliche Aufwand für das Testen den Aufwand für die Implementierung der Schaltung. In vielen Fällen beträgt der Aufwand für das Testen bereits 70% des Entwicklungsaufwands (Bergeron, 2000). Typischerweise wird die Testbench auch in der gewählten Hardwarebeschreibungssprache (VHDL oder Verilog) implementiert. Diese Sprachen stellen jedoch nicht die beste Wahl für Verifikationsbelange dar. Gründe dafür sind darin zu suchen, dass diese Sprachen wichtige Konzepte aus den Softwaresprachen (wie z.B. Objektorientierung) nicht kennen. Weiters stehen komfortable Softwarebibliotheken (Zufallszahlengenerierung, Stringverarbeitung, etc.) den Hardwaresprachen nicht zur Verfügung. In diesem Paper wird der Einsatz der Programmiersprache Python (PythonHomepage, 2003; Beazley, 2001) für die Verifikation vorgeschlagen, um die benötigte Zeit für die Funktionalen Tests zu reduzieren.
Different approaches of high speed data transmission standards
Authors: Ehlert M.
Published: April 2010

Abstract. A number of standards addresses the problem of high-speed data transmission on serial or serial-parallel data lines. Serial-parallel data transmission means the transmitted information is distributed on parallel data lines. Even though several standards exist, there are only a few basic techniques used in most of these standards. This paper is giving an overview of these different basic techniques used in the physical layer of today’s data transmission standards, for example DVI/HDMI, USB2.0, Infiniband, SFI5, etc. [1–9]. The main focus lies on the approaches used for physical signaling, line coding and information synchronization in serial and serialparallel systems. In addition, currently discussed techniques to improve data transmission in the future will be presented.
Calibration methods for microwave free space measurements
Authors: Rolfes I. , Schiek B.
Published: April 2010

Abstract. In this article calibration methods for the precise, contact-less measurement of the permittivity, permeability or humidity of materials are presented. The free space measurement system principally consists of a pair of focusing horn-lens antennas connected to the ports of a vector network analyzer. Based on the measured scattering parameters, the dielectric material parameters are calculable. Due to systematic errors as e.g. transmission losses of the cables or mismatches of the antennas, a calibration of the measurement setup is necessary. For this purpose calibration methods with calibration standards of equal mechanical lengths are presented. They have the advantage, that the measurement setup can be kept in a fixed position, for example no displacement of the antennas is needed. The presented self-calibration methods have in common that the calibration structures consist of a so-called obstacle network which can be partly unknown. The obstacle can either be realized as a transmissive or a reflective network depending on the chosen method. An increase of the frequency bandwidth is achievable with the reflective realization. The theory of the calibration methods and some experimental results will be presented.