bluuebunny/crossref_metadata_2025 huggingface dataset:
Four Fourier transform spectrometers and the Arctic polar vortex: instrument intercomparison and ACE-FTS validation at Eureka during the IPY springs of 2007 and 2008
Authors: Batchelor R. L. , Kolonjari F. , Lindenmaier R. , Mittermeier R. L. , Daffer W. , Fast H. , Manney G. , Strong K. , Walker K. A.
Published: April 2010

Abstract. The Canadian Arctic Atmospheric Chemistry Experiment Validation Campaigns have been carried out at Eureka, Nunavut (80.05° N, 86.42° W) during the polar sunrise period since 2004. During the International Polar Year (IPY) springs of 2007 and 2008, three ground-based Fourier transform infrared (FTIR) spectrometers were operated simultaneously. This paper presents a comparison of trace gas measurements of stratospherically important species involved in ozone depletion, namely O3, HCl, ClONO2, HNO3 and HF, recorded with these three spectrometers. Total column densities of the gases measured with the new Canadian Network for the Detection of Atmospheric Change (CANDAC) Bruker 125HR are shown to agree to within 3.5% with the existing Environment Canada Bomem DA8 measurements. After smoothing both of these sets of measurements to account for the lower spectral resolution of the University of Waterloo Portable Atmospheric Research Interferometric Spectrometer for the Infrared (PARIS-IR), the measurements were likewise shown to agree with PARIS-IR to within 7%. Concurrent measurements of these gases were also made with the satellite-based Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) during overpasses of Eureka during these time periods. While one of the mandates of the ACE satellite mission is to study ozone depletion in the polar spring, previous validation exercises have identified the highly variable polar vortex conditions of the spring period to be a challenge for validation efforts. In this work, comparisons between the CANDAC Bruker 125HR and ACE-FTS have been used to develop strict criteria that allow the ground- and satellite-based instruments to be confidently compared. When these criteria are taken into consideration, there is shown to be no significant bias between the ACE-FTS and ground-based FTIR spectrometer for any of these gases.
A liquid nitrogen-free preconcentration unit for measurements of ambient N2O isotopomers by QCLAS
Authors: Mohn J. , Guggenheim C. , Tuzson B. , Vollmer M. K. , Emmenegger L.
Published: April 2010

Abstract. Important information about the biogeochemical cycle of nitrous oxide (N2O) can be obtained by measuring its three main isotopomers, 14N15N16O, 15N14N16O, and 14N14N16O, and the respective site-specific isotope ratios δ15Nα and δ15Nβ. Absorption laser spectroscopy in the mid-infrared is a direct method for N2O isotopomer analysis, yet not sensitive enough for atmospheric N2O concentrations (320 ppb). To enable a fully-automated high precision N2O isotopomer analysis at ambient concentrations, we built and optimized a liquid nitrogen-free preconcentration unit to be coupled to a quantum cascade laser (QCL) based spectrometer. Rigorous tests were conducted, using FTIR and quantum cascade laser absorption spectroscopy (QCLAS), to investigate recovery rates, conservation of isotopic signatures and spectral interferences after preconcentration. We achieve quantitative N2O recovery of >99% with only minor, statistically not significant isotopic fractionation and no relevant spectral interferences from other atmospheric constituents. The developed preconcentration unit also has the potential to be applied to other trace gases and their isotopic composition.
High-accuracy continuous airborne measurements of greenhouse gases (CO2 and CH4) during BARCA
Authors: Chen H. , Winderlich J. , Gerbig C. , Hoefer A. , Rella C. W. , Crosson E. R. , Van Pelt A. D. , Steinbach J. , Kolle O. , Beck V. , Daube B. C. , Gottlieb E. W. , Chow V. Y. , Santoni G. W. , Wofsy S. C.
Published: April 2010

Abstract. High-accuracy continuous measurements of greenhouse gases (CO2 and CH4) during the BARCA (Balanço Atmosférico Regional de Carbono na Amazônia) phase B campaign in Brazil in May 2009 were accomplished using a newly available analyzer based on the cavity ring-down spectroscopy (CRDS) technique. This analyzer was flown without a drying system or any in-flight calibration gases. Water vapor corrections associated with dilution and pressure-broadening effects for CO2 and CH4 were derived from laboratory experiments employing measurements of water vapor by the CRDS analyzer. Before the campaign, the stability of the analyzer was assessed by laboratory tests under simulated flight conditions. During the campaign, a comparison of CO2 measurements between the CRDS analyzer and a nondispersive infrared (NDIR) analyzer on board the same aircraft showed a mean difference of 0.22±0.09 ppm for all flights over the Amazon rain forest. At the end of the campaign, CO2 concentrations of the synthetic calibration gases used by the NDIR analyzer were determined by the CRDS analyzer. After correcting for the isotope and the pressure-broadening effects that resulted from changes of the composition of synthetic vs. ambient air, and applying those concentrations as calibrated values of the calibration gases to reprocess the CO2 measurements made by the NDIR, the mean difference between the CRDS and the NDIR during BARCA was reduced to 0.05±0.09 ppm, with the mean standard deviation of 0.23±0.05 ppm. The results clearly show that the CRDS is sufficiently stable to be used in flight without drying the air or calibrating in flight and the water corrections are fully adequate for high-accuracy continuous airborne measurements of CO2 and CH4.
Ozone sonde cell current measurements and implications for observations of near-zero ozone concentrations in the tropical upper troposphere
Authors: Vömel H. , Diaz K.
Published: April 2010

Abstract. Laboratory measurements of the Electrochemical Concentration Cell (ECC) ozone sonde cell current using ozone free air as well as defined amounts of ozone reveal that background current measurements during sonde preparation are neither constant as a function of time, nor constant as a function of ozone concentration. Using these background currents in the processing of ECC data may lead to operator dependent uncertainties and may frequently lead to artificially low ozone concentrations in the upper tropical troposphere. Based on these laboratory measurements an improved cell current to partial pressure conversion is proposed, which removes operator dependent variability in the background reading, and possible artifacts in this measurement. Data from the Central Equatorial Pacific Experiment (CEPEX) have been reprocessed using the improved background treatment based on these laboratory measurements. In the reprocessed data set near-zero ozone events no longer occur. At Samoa, Fiji, Tahiti, and San Cristóbal, nearly all near-zero ozone concentrations occur in soundings with larger background currents. To a large extent, these events are no longer observed in the reprocessed data set using the improved background treatment.
An experimental technique for the direct measurement of N2O5 reactivity on ambient particles
Authors: Bertram T. H. , Thornton J. A. , Riedel T. P.
Published: April 2010

Abstract. An experimental approach for the direct measurement of trace gas reactivity on ambient aerosol particles has been developed. The method utilizes a newly designed entrained aerosol flow reactor coupled to a custom-built chemical ionization mass spectrometer. The experimental method is described via application to the measurement of the N2O5 reaction probability, γ(N2O5). Laboratory investigations on well characterized aerosol particles show that measurements of γ(N2O5) observed with this technique are in agreement with previous observations, using conventional flow tube methods, to within ±20% at atmospherically relevant particle surface area concentrations (0–1000 μm2 cm−3). Uncertainty in the measured γ(N2O5) is discussed in the context of fluctuations in potential ambient biases (e.g., temperature, relative humidity and trace gas loadings). Under ambient operating conditions we estimate a single-point uncertainty in γ(N2O5) that ranges between ±(1.3×10−2+0.2×γ(N2O5)), and ±(1.3×10−3+0.2×γ(N2O5)) for particle surface area concentrations of 100 to 1000 μm2 cm−3, respectively. Examples from both laboratory investigations and field observations are included alongside discussion of future applications for the reactivity measurement and optimal deployment locations and conditions.
Determination of aerosol properties from MAX-DOAS observations of the Ring effect
Authors: Wagner T. , Deutschmann T. , Platt U.
Published: April 2010

Abstract. The first quantitative comparison of MAX-DOAS observations of the Ring effect with model simulations is presented. It is performed for a large variety of viewing geometries (solar zenith angles: 45° to 90°, elevation angles: 3°, 6°, 10°, 18°, 90°; three different azimuth angles), which allows a comprehensive test of our capabilities to measure and simulate the Ring effect. In addition to the Ring effect, also the observed O4 absorptions (optical densities) and radiances are compared with model simulations. In general good agreement is found for all measured quantities. From several sensitivity studies it is found that for most measurement situations the aerosol optical depth has usually the strongest influence on the observed quantities, but also other aerosol properties like e.g. the vertical distribution have a significant effect. Typically, the qualitative dependence of the Ring effect on aerosol properties is very similar to that of the O4 absorption. This can be understood, since both quantities depend strongly on the light path length in the lower atmosphere. However, in specific cases, the observation of the Ring effect can provide complementary information to that retrieved from the O4 observations. This is e.g. possible for measurements at small relative azimuth angles, from which information on the asymmetry parameter can be derived. Observations at large solar zenith angle allow the retrieval of stratospheric aerosol properties, even in cases with very low aerosol optical depths. In addition, Ring effect observations in zenith direction are rather sensitive to the aerosol optical depth (in contrast to O4 observations), which might allow to retrieve information on aerosol properties from existing zenith UV data sets prior to the MAX-DOAS era.
Stratospheric isotopic water profiles from a single submillimeter limb scan by TELIS
Authors: de Lange A. , Landgraf J. , Hoogeveen R.
Published: April 2010

Abstract. Around 490 GHz relatively strong HDO and H218O emission lines can be found in the submillimeter thermal-emission spectrum of the Earth's atmosphere, along with lines of the principal isotopologue of water vapour. These can be used for remote sensing of the rare/principal isotope ratio in the stratosphere. A sensitivity study has been performed for retrieval simulations of water isotopologues from balloon-borne measurements by the limb sounder TELIS (TErahertz and submillimeter LImb Sounder). The study demonstrates the capability of TELIS to determine, from a single limb scan, the profiles for H218O and HDO between 20 km and 37 km with a retrieval error of ≈3% and a spatial resolution of 1.5 km, as determined by the width of the averaging kernel. In addition HDO can be retrieved in the range of 10–20 km as well, albeit with a strongly deteriorated retrieval error. Expected uncertainties in instrumental parameters have only limited impact on the retrieval results.
Improved ozone profile retrieval from spaceborn UV backscatter spectrometers
Authors: Mijling B. , Tuinder O. N. E. , van Oss R. F. , van der A R. J.
Published: April 2010

Abstract. The Ozone Profile Algorithm (OPERA), developed at KNMI, retrieves the vertical ozone distribution from nadir spectral satellite measurements of back scattered sunlight in the ultraviolet and visible wavelength range. To produce consistent global datasets the algorithm needs to have good global performance, while short computation time facilitates the use of the algorithm in near real time applications. To test the global performance of the algorithm we look at the convergence behaviour of the ozone retrievals, based on the data of the GOME instrument (on board ERS-2) for February and October 1998. In this way, we uncover different classes of retrieval problems, related to the South Atlantic Anomaly, low cloud fractions over deserts, desert dust outflow over the ocean, and the intertropical convergence zone. The influence of external input data including the ozone cross-sections and the ozone climatologies on the retrieval performance is also investigated. By using a priori ozone profiles which are selected on the expected total ozone column, retrieval problems due to anomalous ozone distributions (such as in the ozone hole) can be avoided. By applying the algorithm adaptations the convergence statistics improve considerably, not only increasing the number of successful retrievals, but also reducing the average computation time, due to less iteration steps per retrieval. For February 1998, non-convergence was brought down from 11.4% to 4.3%, while the mean number of iteration steps (which dominates the computational time) dropped 8% from 5.15 to 4.76.
Remotely operable compact instruments for measuring atmospheric CO2 and CH4 column densities at surface monitoring sites
Authors: Kobayashi N. , Inoue G. , Kawasaki M. , Yoshioka H. , Minomura M. , Murata I. , Nagahama T. , Matsumi Y. , Ibuki T.
Published: April 2010

Abstract. Remotely operable compact instruments for measuring atmospheric CO2 and CH4 column densities were developed in two independent systems: one utilizing a grating-based desktop optical spectrum analyzer (OSA) with a resolution enough to resolve rotational lines of CO2 and CH4 in the region of 1565–1585 and 1674–1682 nm, respectively; the other is an application of an optical fiber Fabry-Perot interferometer (FFPI) to the CO2 column density. Direct sunlight was collimated via a small telescope installed on a portable sun tracker and then transmitted through an optical fiber into the OSA or the FFPI for optical analysis. The near infrared spectra of the OSA were retrieved by a least squares spectral fitting algorithm. The CO2 and CH4 column densities deduced were in excellent agreement with those measured by a Fourier transform spectrometer with high resolution. The rovibronic lines in the wavelength region of 1570–1575 nm were analyzed by the FFPI. The I0 and I values in the Beer-Lambert law equation to obtain CO2 column density were deduced by modulating temperature of the FFPI, which offered column CO2 with the statistical error less than 0.2% for six hours measurement.
Auto MAX-DOAS measurements around entire cities: quantification of NOx emissions from the cities of Mannheim and Ludwigshafen (Germany)
Authors: Ibrahim O. , Shaiganfar R. , Sinreich R. , Stein T. , Platt U. , Wagner T.
Published: April 2010

Abstract. We present Auto Multi-Axis (MAX-) DOAS observations of tropospheric NO2 carried out on circles around the cities of Mannheim and Ludwigshafen (Germany) on 24 August 2006. Together with information on wind speed and direction, the total emissions of the encircled source(s) can be quantified from these measurements. In contrast to recent similar studies based on of zenith scattered sun light (elevation angle of 90°), we use a MAX-DOAS instrument mounted on a car, which observes scattered sun light under different elevation angles (here 45°, and 90°). Compared to simple zenith sky observations, MAX-DOAS observations have higher sensitivity and avoid systematic offsets in the determination of the vertically integrated trace gas concentration. Auto MAX-DOAS observations are especially well suited for the determination of the total emission of extended emission sources (e.g. whole cities), for which typically no sharply defined plumes are formed. In such cases, the trace gas concentrations can be rather small and thus even small systematic offsets in the observed integrated tropospheric trace gas concentration can have a large effect on the determined total emissions. However, such measurements are still affected by several uncertainties which need to be further investigated and minimised. The largest error source is probably the variability and imperfect knowledge of the wind field. In addition – depending on the trace species observed – also chemical transformations between the emission sources and the measurement location have to be considered. In this study we use local observations within the encircled area to quantify and correct these errors. From our observations we derive a total NOx emission from the Mannheim/Ludwigshafen area of (7.2±1.7)×1024 molecules/s (or 17350±4100 t, calculated with the mass of NO2), which is in surprisingly good agreement with existing emission estimates.
Results and recommendations from an intercomparison of six Hygroscopicity-TDMA systems
Authors: Massling A. , Niedermaier N. , Hennig T. , Fors E. , Swietlicki E. , Ehn M. , Hämeri K. , Villani P. , Laj P. , Good N. , McFiggans G. , Wiedensohler A.
Published: April 2010

Abstract. The performance of six custom-built Hygrocopicity-Tandem Differential Mobility Analyzers (H-TDMA) systems was investigated in the frame of an international calibration and intercomparison workshop held in Leipzig, February 2006. The goal of the workshop was to harmonize H-TDMA measurements and develop recommendations for atmospheric measurements and their data evaluation. The H-TDMA systems were compared in terms of the sizing of dry particles, relative humidity (RH) uncertainty and consistency in determination of number fractions of different hygroscopic particle groups. The experiments were performed in an air-conditioned laboratory using ammonium sulfate particles or an external mixture of ammonium sulfate and soot particles. The sizing of dry particles of the six H-TDMA systems was within 0.2 to 4.2% of the selected particle diameter depending on investigated size and individual system. With regard to RH uncertainties, the H-TDMA systems showed deviations up to 4.5% RH from the set point at RH=90% investigating the hygroscopic growth of ammonium sulfate particles and comparing the results with theory. The evaluation of number fractions investigating an externally mixed aerosol delivered differences up to +/−8% in calculated number fraction for one and the same aerosol type. We analysed the datasets of the different H-TDMAs with one fitting routine to investigate differences caused by the different data evaluation procedures. The results showed that the differences were reduced from +12/−13% to +8/−6%. We can conclude here that a common data evaluation procedure to determine the number fraction of externally mixed aerosols will improve the comparability of H-TDMA measurements. We finally recommend, to ensure a good calibration of all flow, temperature and RH sensors in the systems. It is most important to thermally insulate the RH control unit and the second DMA and to monitor those temperatures as accurately as 0.2 °C. For a correct determination of external mixtures, it is necessary to take into account size-dependent losses due to the diffusion in the pluming between the DMAs and in the aerosol humidification unit.
Collocating satellite-based radar and radiometer measurements – methodology and usage examples
Authors: Holl G. , Buehler S. A. , Rydberg B. , Jiménez C.
Published: April 2010

Abstract. Collocations between two satellite sensors are occasions where both sensors observe the same place at roughly the same time. We study collocations between the Microwave Humidity Sounder (MHS) onboard NOAA-18 and the Cloud Profiling Radar (CPR) onboard the CloudSat CPR. First, a simple method is presented to obtain those collocations and this method is compared with a more complicated approach found in literature. We present the statistical properties of the collocations, with particular attention to the effects of the differences in footprint size. For 2007, we find approximately two and a half million MHS measurements with CPR pixels close to their centrepoints. Most of those collocations contain at least ten CloudSat pixels and image relatively homogeneous scenes. In the second part, we present three possible applications for the collocations. Firstly, we use the collocations to validate an operational Ice Water Path (IWP) product from MHS measurements, produced by the National Environment Satellite, Data and Information System (NESDIS) in the Microwave Surface and Precipitation Products System (MSPPS). IWP values from the CloudSat CPR are found to be significantly larger than those from the MSPPS. Secondly, we compare the relation between IWP and MHS channel 5 (190.311 GHz) brightness temperature for two datasets: the collocated dataset, and an artificial dataset. We find a larger variability in the collocated dataset. Finally, we use the collocations to train an Artificial Neural Network and describe how we can use it to develop a new MHS-based IWP product. We also study the effect of adding measurements from the High Resolution Infrared Radiation Sounder (HIRS), channels 8 (11.11 μm) and 11 (8.33 μm). This shows a small improvement in the retrieval quality. The collocations described in the article are available for public use.
Optimization of traceable coaxial RF reflection standards with 7-mm-N-connector using genetic algorithms
Authors: Schrader T.
Published: April 2010

Abstract. A new coaxial device with 7-mm-N-connector was developed providing calculable complex reflection coefficients for traceable calibration of vector network analyzers (VNA). It was specifically designed to fill the gap between 0 Hz (DC, direct current) and 250MHz, though the device was tested up to 10GHz. The frequency dependent reflection coefficient of this device can be described by a model, which is characterized by traceable measurements. It is therefore regarded as a “traceable model". The new idea of using such models for traceability has been verified, found to be valid and was used for these investigations. The DC resistance value was extracted from RF measurements up to 10 GHz by means of Genetic Algorithms (GA). The GA was used to obtain the elements of the model describing the reflection coefficient Γ of a network of SMD resistors. The DC values determined with the GA from RF measurements match the traceable value at DC within 3·10-3, which is in good agreement with measurements using reference air lines at GHz frequencies.
Study of heterogeneous and reconfigurable architectures in the communication domain
Authors: Feldkaemper H. T. , Blume H. , Noll T. G.
Published: April 2010

Abstract. One of the most challenging design issues for next generations of (mobile) communication systems is fulfilling the computational demands while finding an appropriate trade-off between flexibility and implementation aspects, especially power consumption. Flexibility of modern architectures is desirable, e.g. concerning adaptation to new standards and reduction of time-to-market of a new product. Typical target architectures for future communication systems include embedded FPGAs, dedicated macros as well as programmable digital signal and control oriented processor cores as each of these has its specific advantages. These will be integrated as a System-on-Chip (SoC). For such a heterogeneous architecture a design space exploration and an appropriate partitioning plays a crucial role. On the exemplary vehicle of a Viterbi decoder as frequently used in communication systems we show which costs in terms of ATE complexity arise implementing typical components on different types of architecture blocks. A factor of about seven orders of magnitude spans between a physically optimised implementation and an implementation on a programmable DSP kernel. An implementation on an embedded FPGA kernel is in between these two representing an attractive compromise with high flexibility and low power consumption. Extending this comparison to further components, it is shown quantitatively that the cost ratio between different implementation alternatives is closely related to the operation to be performed. This information is essential for the appropriate partitioning of heterogeneous systems.
Adiabatic circuits: converter for static CMOS signals
Authors: Fischer J. , Amirante E. , Bargagli-Stoffi A. , Schmitt-Landsiedel D.
Published: April 2010

Abstract. Ultra low power applications can take great advantages from adiabatic circuitry. In this technique a multiphase system is used which consists ideally of trapezoidal voltage signals. The input signals to be processed will often come from a function block realized in static CMOS. The static rectangular signals must be converted for the oscillating multiphase system of the adiabatic circuitry. This work shows how to convert the input signals to the proposed pulse form which is synchronized to the appropriate supply voltage. By means of adder structures designed for a 0.13µm technology in a 4-phase system there will be demonstrated, which additional circuits are necessary for the conversion. It must be taken into account whether the data arrive in parallel or serial form. Parallel data are all in one phase and therefore it is advantageous to use an adder structure with a proper input stage, e.g. a Carry Lookahead Adder (CLA). With a serial input stage it is possible to read and to process four signals during one cycle due to the adiabatic 4-phase system. Therefore input signals with a frequency four times higher than the adiabatic clock frequency can be used. This reduces the disadvantage of the slow clock period typical for adiabatic circuits. By means of an 8 bit Ripple Carry Adder (8 bit RCA) the serial reading will be introduced. If the word width is larger than 4 bits the word can be divided in 4 bit words which are processed in parallel. This is the most efficient way to minimize the number of input lines and pads. At the same time a high throughput is achieved.
The background absorption at high latitudes
Authors: Harrich M. , Friedrich M. , Marple S. R. , Torkar K. M.
Published: April 2010

Abstract. The high latitude ionosphere is more often disturbed than quiet, i.e. fluxes of charged particles dominate over solar controlled ionisation. Nonetheless, the actual amount of the predictable, solar-controlled ionisation and the resulting absorption is of interest for some applications.
Response of the Effelsberg 100m radio telescope to signals in the near-field at 24 GHz
Authors: Ruf K. , Fürst E. , Grypstra K. , Neidhöfer J. , Schumacher M.
Published: April 2010

Abstract. Short range radar (SRR) for cars has been proposed to operate over 5 GHz of bandwidth at the 24 GHz ISM band. To estimate the level of interference from these devices on radio telescopes, the near-field antenna pattern has to be known. We report on new measurements with the Effelsberg 100 m radio telescope. These measurements were performed with a transmitter set up at a distance of 1.7 km from the telescope. The strength of the signal picked up by the telescope sidelobes shows that the proposed SRR would interfere with sensitive radio astronomical observations.
Determination of quality and storage-time of dielectric mixtures using time domain spectroscopy
Authors: Schimmer O. , Daschner F. , Kent M. , Knöchel R.
Published: April 2010

Abstract. This paper presents a novel approach for determining certain material properties from permittivity measurements. It does not rely on physical models and mixture formulas. Instead, the reflection time domain response of the material to a step impulse is evaluated in a narrow time window near the steepest ascent of the pulse. A dedicated time domain spectrometer is introduced, which records the data. Principal components are derived directly from the time domain data. The most significant principal components are used to establish a principal component regression formula for prediction of the required material properties. The viability and accuracy of the method is demonstrated by applying it to measurements of the storage time of some chilled fish samples.
Synchronization in MIMO OFDM systems
Authors: Häring L. , Czylwik A.
Published: April 2010

Abstract. In this paper, an overview of carrier frequency offset (CFO) estimation algorithms for Orthogonal Frequency Division Multiplexing (OFDM) systems is presented. It is well-known that multicarrier systems suffer from their high sensitivity to mismatches of transmitter and receiver oscillator frequencies. The performance degrades since the CFO destroys the orthogonality of the subcarriers. Hence, extensive research has been done on the estimation and correction of the CFO in Single-Input Single-Output (SISO) systems. Mainly, the proposed algorithms can be categorized into data-aided and blind techniques. Several estimation techniques have been extended to the Single-Input Multiple- Output (SIMO) case where multiple receive antennas can be utilized to gain diversity. However, less attention has been paid on synchronization in the attractive Multiple-Input Multiple-Output (MIMO) case which is topic of tremendous interest in current research. The present paper concentrates on aspects of this new scenario. Starting with algorithms for SISO and SIMO, this contribution reviews briefly proposed carrier frequency synchronization techniques which could be implemented in forthcoming MIMO systems.
The IRI topside parameters
Authors: Coïsson P. , Radicella S. M.
Published: April 2010

Abstract. The IRI electron density topside has been constructed on the basis of the data available about thirty years ago. Recently a large amount of data from old topside sounders have been processed to get electron density profiles. These profiles allow to test IRI model under a wide spectrum of different conditions and to understand the behavior of the modeled topside. A set of 12 000 topside profiles have been chosen from the ISIS2 database, selecting those with the better quality of the inverted profile. An analysis of each IRI topside constitutive parameter has been done for all the experimental cases allowing to find some critical conditions under which the IRI topside could become completely unrealistic. In particular for very high solar activity at high latitudes it has been found that some IRI parameters could reach values that change drastically the shape of IRI topside. A proposal to control their range of variability is formulated in order to avoid the occurrence of such cases.
Sixty years of ionospheric measurements and studies*
Authors: Bibl K.
Published: April 2010

Abstract. Professor Rawer’s professional ethics allowed him to create an excellent institute with co-workers forming a successful team with creative individuals. Showing myself as an example, this paper demonstrates his guidance, his care, and his ability to create independent thinking in the areas of equipment development and the analysis of data produced by this equipment.
Störbeeinflussung von Neurostimulatoren durch Koagulationsgeräte basierend auf der Verkopplung über den menschlichen Körper
Authors: Schick M. , Landstorfer F. M.
Published: April 2010

Abstract. Am Beispiel der Verkopplung von Koagulationsgeräten und implantierten Neurostimulatoren wird die gegenseitige Störbeeinflussung von medizinischen Geräten über den menschlichen Körper dargestellt. Für die Berechnungen dieses Szenarios werden die verwendeten Geräte charakterisiert und modelliert. Ebenso wird ein nach DIN 33 402 Teil 2 entwickeltes Modell des menschlichen Körpers verwendet. Für dessen elektrische Eigenschaften werden in Abhängigkeit von der Frequenz gewichtete Mittelwerte aus mehreren relevanten Organen berücksichtigt. Bei den durchgeführten Untersuchungen werden verschiedene Parameter, wie die Implantationsart des Neurostimulators, der Verlauf und die Länge dessen Elektrode, der Koagulationspunkt am menschlichen Körper, die Frequenz, mit der koaguliert wird, und die Länge des Koagulatorkabels variiert, um so zu ,,worst-case“-Aussagen zu gelangen. In den Ergebniskurven lassen sich Überhöhungen beobachten, die sich auf Resonanzeffekte z.B. auf dem Koagulatorkabel zurückführen lassen.
Generation of short electrical pulses based on bipolar transistorsny
Authors: Gerding M. , Musch T. , Schiek B.
Published: April 2010

Abstract. A system for the generation of short electrical pulses based on the minority carrier charge storage and the step recovery effect of bipolar transistors is presented. Electrical pulses of about 90 ps up to 800 ps duration are generated with a maximum amplitude of approximately 7V at 50Ω. The bipolar transistor is driven into saturation and the base-collector and base-emitter junctions become forward biased. The resulting fast switch-off edge of the transistor’s output signal is the basis for the pulse generation. The fast switching of the transistor occurs as a result of the minority carriers that have been injected and stored across the base-collector junction under forward bias conditions. If the saturated transistor is suddenly reverse biased the pn-junction will appear as a low impedance until the stored charge is depleted. Then the impedance will suddenly increase to its normal high value and the flow of current through the junction will turn to zero, abruptly. A differentiation of the output signal of the transistor results in two short pulses with opposite polarities. The differentiating circuit is implemented by a transmission line network, which mainly acts as a high pass filter. Both the transistor technology (pnp or npn) and the phase of the transfer function of the differentating circuit influence the polarity of the output pulses. The pulse duration depends on the transistor parameters as well as on the transfer function of the pulse shaping network. This way of generating short electrical pulses is a new alternative for conventional comb generators based on steprecovery diodes (SRD). Due to the three-terminal structure of the transistor the isolation problem between the input and the output signal of the transistor network is drastically simplified. Furthermore the transistor is an active element in contrast to a SRD, so that its current gain can be used to minimize the power of the driving signal.
Exponential Modelling for Mutual-Cohering of Subband Radar Data
Authors: Siart U. , Tejero S. , Detlefsen J.
Published: April 2010

Abstract. Increasing resolution and accuracy is an important issue in almost any type of radar sensor application. However, both resolution and accuracy are strongly related to the available signal bandwidth and energy that can be used. Nowadays, often several sensors operating in different frequency bands become available on a sensor platform. It is an attractive goal to use the potential of advanced signal modelling and optimization procedures by making proper use of information stemming from different frequency bands at the RF signal level. An important prerequisite for optimal use of signal energy is coherence between all contributing sensors. Coherent multi-sensor platforms are greatly expensive and are thus not available in general. This paper presents an approach for accurately estimating object radar responses using subband measurements at different RF frequencies. An exponential model approach allows to compensate for the lack of mutual coherence between independently operating sensors. Mutual coherence is recovered from the a-priori information that both sensors have common scattering centers in view. Minimizing the total squared deviation between measured data and a full-range exponential signal model leads to more accurate pole angles and pole magnitudes compared to single-band optimization. The model parameters (range and magnitude of point scatterers) after this full-range optimization process are also more accurate than the parameters obtained from a commonly used super-resolution procedure (root-MUSIC) applied to the non-coherent subband data.
Determination of Harmonic-Transfer-Matrices by Simulation
Authors: Müller R. , Jentschel H.-J.
Published: April 2010

Abstract. In this paper a method to obtain harmonic transfer matrices (HTM) from simulated or measured values (signature & signature response) is presented. These matrices subserve a description of complex systems (e.g. RF front-ends) with real properties, which can't be specified by simple analytic expressions. They afford to give statements about a systems parameter. That's why HTM are suitable for Built-In-Self-Test (BIST) and opens the option for Built-In-Self-Correction (BISC) for critical function-blocks.
Field-Theoretical Investigations of the Influence of Mutual Coupling Effects on the Capacity of MIMO Wireless Links
Authors: Ndoumbè Mbonjo Mbonjo H. , Wu G. , Hansen V.
Published: April 2010

Abstract. We present a MIMO channel model which takes into account mutual coupling effects at the receiver and transmitter array in order to assess the influence of mutual coupling effects on the capacity of MIMO channels. We evaluate the mutual impedances using a general approach based on the electric field integral equation (EFIE) and its implementation by the method of moments (MOM). We compute the capacity of a 2x2-MIMO system in a one path scenario for square half wavelength patch antenna elements and half wavelength dipole antenna elements. The capacity of the MIMO system with and without coupling increases compared to the single antenna transmission for the patch antenna elements. On the contrary for half wavelength dipole antenna elements we have found that the MIMO system degenerates to a one-transmitting, one-receiving antenna system due to mutual coupling.
A Vector Network Analyzer Based on Pulse Generators
Authors: Schulte B. , Gerding M. , Schiek B.
Published: April 2010

Abstract. A fast four channel network analyzer is introduced to measure S-parameters in a frequency range from 10MHz to 3GHz. The signal generation for this kind of analyzer is based on pulse generators, which are realized with bipolar transistors. The output signal of the transistor is differentiated and two short pulses, a slow and a fast one, with opposite polarities are generated. The slow pulse is suppressed with a clipping network. Thus the generation of very short electrical pulses with a duration of about 100ps is possible. The structure of the following network analyzer is similar to the structure of a conventional four channel network analyzer. All four pulses, which contain the high frequency information of the device under test, are evaluated after the digitalization of intermediate frequencies. These intermediate frequencies are generated with sampling mixers. The recorded data is evaluated with a special analysis technique, which is based on a Fourier transformation. The calibration techniques used are the same as for conventional four channel network analyzers, no new calibration techniques need to be developed.
Feature selection with acquisition cost for optimizing sensor system design
Authors: Iswandy K. , Koenig A.
Published: April 2010

Abstract. Selection of variables from large sets of measurements is a common problem of data analysis and signal processing in many disciplines. In engineering and sensor technology the design of recognition systems can be optimized by judicious choice of subsets of relevant features. In particular, the effort required for signal processing and sensor registration can be considerably reduced by efficient feature selection. However, the current approaches in majority only consider the contribution of features or measurements to the classification ability of the system. The associated cost in terms of computation effort, the required electronics, and power dissipation is not explicitly in consideration. This paper proposes a multi-objective extension of feature selection including acquisition cost and employing and comparing two evolutionary optimization methods. The genetic and particle swarm algorithms and the results achieved with selected data sets will be presented. The results show, that particle swarm algorithm can select best features with lower cost and achieve more competitive results with regard to convergence time and classification accuracy than genetic algorithm.
Entwicklung eines integrierten optoelektronischen Berührungssensors
Authors: Kodl G. , Voigt C. , Tremmel J. , Siegl J.
Published: April 2010

Abstract. Für die von der Firma LEONI AG, Nürnberg entwickelte "dämpfungssensitive" flexible Polymerfaser ergeben sich vielfältige Anwendungen, u.a. im Automotive-Bereich, beispielsweise als Einklemmschutzsensor oder als Fußgängerschutzsensor integriert in die Stoßstange. Auf der Sendeseite wird in die Plastikfaser ein gepulstes Lichtsignal eingespeist. Am Empfangsort ist der Photostrom einer Photodiode abhängig vom Druck der auf die Faser einwirkt. Die integrierte Sensorelektronik hat die Aufgabe, den vom Druck beeinflussten Photostrom zu erfassen und möglichst störsicher auszuwerten. Die Anforderungen verschiedener Applikationen müssen sich durch geeignete Konfiguration der Auswertesoftware berücksichtigen lassen. Die integrierte Sensorelektronik besteht aus einem Licht/Frequenz-Konverter und einer auf Basis eines Prozessors implementierten Auswertesoftware. Der Licht/Frequenz-Konverter ist ein getakteter, konfigurierbarer Integrator, der über einen Komparator ein Digitalsignal liefert, dessen Frequenz proportional dem Photostrom ist. Sensorelektronik und Photodiode wurden in CMOS-Technologie mit dem 0,35um-CMOS-Opto-Process der Firma Austria Microsystems, Graz, realisiert.
IQ-imbalance and its compensation for non-ideal analog receivers comprising frequency-selective components
Authors: Mailand M. , Richter R. , Jentschel H.-J.
Published: April 2010

Abstract. Within current implementations of mobile terminals, more and more analog components are replaced by appropriate digital processing. On the one hand, the analog front-ends become less complex. On the other hand, more digital signal processing is required to compensate for the spurious effects of the front-end. In this article, the frequency-selective imbalance of the in-phase and quadrature-phase signals is addressed. A closed representation of arbitrary signals being processed by an arbitrary imbalanced analog front-end is provided. The analysis is valid for both, direct conversion and intermediate frequency (IF) reception. With the consideration of practical variations of amplitude and phase impairments, the influence of only the frequency-dependent portions of the impairments is investigated. It is shown, that the compensation of the quasi-linear impairments is sufficient and complex deconvolutive IQ-regeneration procedures are not stringently required to obtain sufficient signal qualities.
Configurable multiplier modules for an adaptive computing system
Authors: Pfänder O. A. , Pfleiderer H.-J. , Lachowicz S. W.
Published: April 2010

Abstract. The importance of reconfigurable hardware is increasing steadily. For example, the primary approach of using adaptive systems based on programmable gate arrays and configurable routing resources has gone mainstream and high-performance programmable logic devices are rivaling traditional application-specific hardwired integrated circuits. Also, the idea of moving from the 2-D domain into a 3-D design which stacks several active layers above each other is gaining momentum in research and industry, to cope with the demand for smaller devices with a higher scale of integration. However, optimized arithmetic blocks in course-grain reconfigurable arrays as well as field-programmable architectures still play an important role. In countless digital systems and signal processing applications, the multiplication is one of the critical challenges, where in many cases a trade-off between area usage and data throughput has to be made. But the a priori choice of word-length and number representation can also be replaced by a dynamic choice at run-time, in order to improve flexibility, area efficiency and the level of parallelism in computation. In this contribution, we look at an adaptive computing system called 3-D-SoftChip to point out what parameters are crucial to implement flexible multiplier blocks into optimized elements for accelerated processing. The 3-D-SoftChip architecture uses a novel approach to 3-dimensional integration based on flip-chip bonding with indium bumps. The modular construction, the introduction of interfaces to realize the exchange of intermediate data, and the reconfigurable sign handling approach will be explained, as well as a beneficial way to handle and distribute the numerous required control signals.
An integrated 3.1–5.1 GHz pulse generator for ultra-wideband wireless localization systems
Authors: Fan X. , Fischer G. , Dietrich B.
Published: April 2010

Abstract. This paper presents an implementation of an integrated Ultra-wideband (UWB), Binary-Phase Shift Keying (BPSK) Gaussian modulated pulse generator. VCO, multiplier and passive Gaussian filter are the key components. The VCO provides the carrier frequency of 4.1 GHz, the LC Gaussian filter is responsible for the pulse shaping in the baseband. Multiplying the baseband pulse and the VCO frequency shifts the pulse to the desired center frequency. The generated Gaussian pulse ocupppies the frequency range from 3.1 to 5.1 GHz with the center frequency at 4.1 GHz. Simulations and measured results show that this spectrum fulfills the mask for indoor communication systems given by the FCC (Federal Communications Commission, 2002). The total power consumption is 55 mW using a supply voltage of 2.5 V. Circuits are realized using the IHP 0.25 μm SiGe:C BiCMOS technology.
Design and quantitative analysis of parametrisable eFPGA-architectures for arithmetic
Authors: Neumann B. , von Sydow T. , Blume H. , Noll T. G.
Published: April 2010

Abstract. Future SoCs will feature embedded FPGAs (eFPGAs) to enable flexible and efficient implementations of high-throughput digital signal processing applications. Current research projects on and emerging products containing FPGAs are mainly based on "standard FPGA"-architectures that are optimised for a very wide range of applications. The implementation costs of these FPGAs are dominated by a very complex interconnect network. This paper presents a method to improve the efficiency of eFPGAs by tailoring them for a certain application domain using a parametrisable architecture template derived from the results of a systematic evaluation of the requirements of the application domain. Two different architectures are discussed, a reference architecture to illustrate the methodology and possible optimisation measures as well as a specialised arithmetic-oriented eFPGA for applications like correlators, decoders, and filters. For the arithmetic-oriented architecture, a novel logic element (LE) and a special interconnect architecture that was designed with respect to the connectivity characteristics of regular datapaths, are presented. For both architecture templates, physically optimised implementations based on an automatic design approach have been created. As a first cost comparison of these implementations with standard FPGAs, the LE-density (number of logic elements per mm2) is evaluated. For the arithmetic-oriented architecture, the LE-density could be increased by an order of magnitude compared to standard architectures.
A Verilog-A model of an undoped symmetric dual-gate MOSFET
Authors: Cobianu O. , Soffke O. , Glesner M.
Published: April 2010

Abstract. We describe a new procedure of solving the electrostatic potentials in the silicon film of an undoped DG SOI MOSFET structure. Starting from a model previously described in the literature by Malobabic et al. (2004), we propose the bisection method for the solution of transcendental equation giving the surface electrostatic potential of the silicon channel, as a function of the gate to source voltage and the voltage along the channel. The above calculated results are used for obtaining the charges and corresponding drain current in the DG MOSFET transistor. The entire model is implemented in Verilog A and can be used inside Cadence for the determination of the static regime of electrical circuits based on undoped symmetric DG SOI MOSFET. As a case study, a simple common-source amplifier built with such a novel device is analyzed, showing the currents and voltages present in the circuit.