bluuebunny/crossref_metadata_2025 huggingface dataset:
Intercomparison of stratospheric ozone and temperature profiles during the October 2005 Hohenpeissenberg Ozone Profiling Experiment (HOPE)
Authors: Steinbrecht W. , McGee T. J. , Twigg L. W. , Claude H. , Schönenborn F. , Sumnicht G. K. , Silbert D.
Published: April 2010

Abstract. Thirteen clear nights in October 2005 allowed successful intercomparison of the stationary lidar operated since 1987 by the German Weather Service (DWD) at Hohenpeissenberg (47.8° N, 11.0° E) with the Network for the Detection of Atmospheric Composition Change (NDACC) travelling standard lidar operated by NASA's Goddard Space Flight Center. Both lidars provide ozone profiles in the stratosphere, and temperature profiles in the strato- and mesosphere. Additional ozone profiles came from on-site Brewer/Mast ozonesondes, additional temperature profiles from Vaisala RS92 radiosondes launched at Munich (65 km north-east), and from operational analyses by the US National Centers for Environmental Prediction (NCEP). The intercomparison confirmed a low bias for ozone from the DWD lidar in the 33 to 43 km region, by up to 10%. This bias is caused by the DWD ozone algorithm. It will be removed in a future version. Between 20 and 33 km, agreement between both lidars, and ozonesondes below 30 km, is good with ozone differences less than 3 to 5%. Results are consistent with previous comparisons of the DWD lidar with SAGE, GOMOS and other satellite instruments. The intercomparison did uncover a 290 m upward shift of the DWD lidar data. When this shift is removed, agreement with ozone from the NASA lidar improves below 20 km, with remaining differences usually less than 5%, and not statistically significant. Precision (repeatability) for the lidar ozone data is better than 5% between 20 and 40 km altitude, dropping to 10% near 45 km, and 50% near 50 km. Temperature from the DWD lidar has a 1 to 2 K cold bias from 30 to 65 km against the NASA lidar, and a 2 to 4 K cold bias against radiosondes and NCEP. This is consistent with previous intercomparisons against NCEP or radiosondes. The cold bias against the NASA lidar disappears when the DWD lidar data are corrected for the afore-mentioned 290 m range error, and more appropriate values for the Earth's gravity acceleration are used. Temperature precision (repeatability) for the DWD lidar is better than 2 K between 30 and 50 km , decreasing to 10 K near 70 km. It is over-estimated by the current DWD algorithm, and should be reduced by a factor of 2.2 (e.g. from 22 K to 10 K near 70 km). Temperature and ozone variations are tracked well by both lidars, by ozone- and radiosondes, and by NCEP analyses. Correlations exceed 0.8 to 0.9 at most stratospheric levels. They decrease at levels above 40 km, especially for ozone or NCEP temperature. The ozone and temperature bias of the DWD lidar does not appear to have changed over the years. Long-term records of ozone and temperature from the DWD lidar should be consistent. Nevertheless, the HOPE intercomparison was instrumental in uncovering several long-standing errors. These need to be fixed and the entire DWD lidar data record needs to be reprocessed.
Cloud sensitivity studies for stratospheric and lower mesospheric ozone profile retrievals from measurements of limb scattered solar radiation
Authors: Sonkaew T. , Rozanov V. V. , von Savigny C. , Rozanov A. , Bovensmann H. , Burrows J. P.
Published: April 2010

Abstract. Clouds in the atmosphere play an important role in reflection, absorption and transmission of solar radiation affecting trace gas retrievals. The main goal of this paper is to examine the sensitivity of stratospheric and lower mesospheric ozone retrievals from limb-scattered radiance measurements to clouds using the SCIATRAN radiative transfer model and retrieval package. Assuming an aerosol-free atmosphere and Mie phase functions for cloud particles, we compute the relative error of ozone profile retrievals in a cloudy atmosphere if clouds are neglected in the retrieval. To access altitudes from the lower stratosphere up to lower mesosphere, we combine the retrievals in the Chappuis and Hartley ozone absorption bands. We find significant cloud sensitivity of the limb ozone retrievals in the Chappuis bands at lower stratospheric altitudes. The relative error in the retrieved ozone concentrations gradually decreases with increasing altitude and becomes negligible above about 40 km. The parameters with the largest impact on the ozone retrievals are cloud optical thickness, ground albedo and solar zenith angle. Clouds with different geometrical thicknesses or different cloud altitudes have a similar impact on the ozone retrievals for a given cloud optical thickness value, if the clouds are outside the field of view of the instrument. The effective radius of water droplets has a small influence on the error, i.e., less than 0.5% at altitudes above the cloud top height. Furthermore, the impact of clouds on the ozone profile retrievals was found to have a rather small dependence on the solar azimuth angle (less than 1% for all possible azimuth angles). For the most frequent cloud types the total error is below 6% above 15 km altitude, if clouds are completely neglected in the retrieval. Neglecting clouds in the ozone profile retrievals generally leads to a low bias for a low ground albedo and to a high bias for a high ground albedo, assuming that the ground albedo is well known.
Cloud particle size distributions measured with an airborne digital in-line holographic instrument
Authors: Fugal J. P. , Shaw R. A.
Published: April 2010

Abstract. Holographic data from the prototype airborne digital holographic instrument HOLODEC (Holographic Detector for Clouds), taken during test flights are digitally reconstructed to obtain the size (equivalent diameters in the range 23 to 1000 μm), three-dimensional position, and two-dimensional profile of ice particles and then ice particle size distributions and number densities are calculated using an automated algorithm with minimal user intervention. The holographic method offers the advantages of a well-defined sample volume size that is not dependent on particle size or airspeed, and offers a unique method of detecting shattered particles. The holographic method also allows the volume sample rate to be increased beyond that of the prototype HOLODEC instrument, limited solely by camera technology. HOLODEC size distributions taken in mixed-phase regions of cloud compare well to size distributions from a PMS FSSP probe also onboard the aircraft during the test flights. A conservative algorithm for detecting shattered particles utilizing the particles depth-position along the optical axis eliminates the obvious ice particle shattering events from the data set. In this particular case, the size distributions of non-shattered particles are reduced by approximately a factor of two for particles 15 to 70 μm in equivalent diameter, compared to size distributions of all particles.
Greenhouse gas analysis of air samples collected onboard the CARIBIC passenger aircraft
Authors: Schuck T. J. , Brenninkmeijer C. A. M. , Slemr F. , Xueref-Remy I. , Zahn A.
Published: April 2010

Abstract. CARIBIC (Civil Aircraft for the Regular Investigation of the Atmosphere Based on an Instrument Container) is a long-term atmospheric measurement program based on the use of a comprehensive scientific instrument package aboard a passenger aircraft. In addition to real time measurements, whole air sampling is performed regularly at cruising altitude in the upper troposphere and the extra-tropical UT/LS region. Air samples are analysed for greenhouse gases, NMHCs, halocarbons, and isotopic composition. The routinely performed greenhouse gas analysis comprises gas chromatography measurements of CO2, CH4, N2O and SF6. The sampling procedure, the GC system used for greenhouse gas analysis and its performance are described. Comparisons with other laboratories have shown good agreement of results as has a comparison with results from a CO2 in-situ analyser that is also part of the CARIBIC instrumentation. The timeseries of CO2 obtained from the collection of 684 samples at latitudes between 30° N and 56° N on 21 roundtrips out of Germany to different destinations in Asia between November 2005 and October 2008 is shown. A timeshift in the seasonal cyle of about one month was observed between the upper troposphere and the tropopause region. For two sets of return flights from Germany to the Philippines the relations between the four greenhouse gases CO2, CH4, N2O and SF6 are discussed in more detail. Distinct seasonal changes in the correlation between CH4 and CO2 are observed.
The detection of cloud free snow covered areas using AATSR measurements
Authors: Istomina L. G. , von Hoyningen-Huene W. , Kokhanovsky A. A. , Burrows J. P.
Published: April 2010

Abstract. A new method to detect cloud free snow covered areas is developed using the measurements by the Advanced Along Track Scanning Radiometer (AATSR) on board the ENVISAT satellite in order to discriminate clear snow fields for the retrieval of aerosol optical thickness or snow properties. The algorithm uses seven AATSR channels from VIS to TIR and analyzes the spectral behavior of each pixel in order to recognize the spectral signature of snow. The algorithm includes a set of relative thresholds and combines all seven channels into one flexible criterion, which allows us to filter out all the pixels with spectral behavior similar to that of snow. The algorithm does not use any kind of morphological criteria and does not require the studied surface to have any special structure. The snow spectral shape criterion was determined by a comprehensive theoretical study, which included radiative transfer simulations for various atmospheric conditions as well as studying existing models and measurements of snow optical and physical properties in different spectral bands. The method has been optimized to detect cloud free snow covered areas, and does not produce cloud/land/ocean/snow mask. However, the algorithm can be extended and be able to discriminate various kinds of surfaces. The presented method has been validated against Micro Pulse Lidar data and compared to MODIS cloud mask over snow covered areas, showing quite good correspondence to each other.
Reducing uncertainties associated with filter-based optical measurements of soot aerosol particles with chemical information
Authors: Engström J. E. , Leck C.
Published: April 2010

Abstract. Of the many identified and potential effects of atmospheric aerosol particles on climate, those of soot particles are the most uncertain, in that analytical techniques concerning soot are far from satisfactory. One concern when applying filter-based optical measurements of soot is that they suffer from systematic errors due to the light scattering of non-absorbing particles co-deposited on the filter, such as inorganic salts and mineral dust. In addition to an optical correction of the non-absorbing material this study provides a protocol for correction of light scattering based on the chemical quantification of the material, which is a novelty. A newly designed Particle Soot Absorption Photometer was constructed to measure light transmission on particle accumulating filters, which includes an additional sensor recording backscattered light. The choice of polycarbonate membrane filters avoided high chemical blank values and reduced errors associated with length of the light path through the filter. Two protocols for corrections were applied to aerosol samples collected at the Maldives Climate Observatory Hanimaadhoo during episodes with either continentally influenced air from the Indian/Arabian subcontinents (winter season) or pristine air from the Southern Indian Ocean (summer monsoon). The two ways of correction (optical and chemical) lowered the particle light absorption of soot by 63 to 61%, respectively, for data from the Arabian Sea sourced group, resulting in median soot absorption coefficients of 4.2 and 3.5 Mm-1. Corresponding values for the South Indian Ocean data were 69 and 97% (0.38 and 0.02 Mm-1). A comparison with other studies in the area indicated an overestimation of their soot levels, by up to two orders of magnitude. This raises the necessity for chemical correction protocols on optical filter-based determinations of soot, before even the sign on the radiative forcing based on their effects can be assessed.
Investigation of the accuracy for single scattering albedo retrieval from global UV irradiance measurements
Authors: Kazadzis S. , Gröbner J. , Arola A. , Amiridis V.
Published: April 2010

Abstract. Retrieval of aerosol optical absorption properties in the UV spectral range such as single scattering albedo (SSA), using remote sensing techniques, is currently an open scientific issue. We investigate the limitations on calculating columnar SSA using a combination of global UV spectral measurements (that are comon in various UV monitoring stations worldwide) in combination with radiative transfer modeling. To point out the difficulties in such retrieval we have used the travelling reference spectroradiometer (QASUME) results from 27 visits to UV monitoring stations around Europe, using the QASUME instrument as relative reference, analyzing absolute differences and also temporal and spectral deviations of UV irraidances, that are used as basic input for the SSA retrieval. The results comparing the mean SSA derived by all instruments, measuring synchronous UV spectra, showed that 5 were within ±0.02 difference from the SSA calculated from the QASUME instrument, while 17 were within ±0.04, for the Solar zenith angle of 60 degrees. As for the uncertainty that has been calculated using the 2σ standard deviation of the spectral measurements, a mean 0.072 and 0.10 (2σ) uncertainties have been calculated for 60° and 30° respectively. Based on such results we show that only very few instruments could be able to detect long term SSA changes. However, such measurements/results are useful in order to retrieve SSA at UV wavelengths, a product needed for various applications such as, inputs for modeling radiative forcing studies and satellite retrieval algorithms.
A new aerosol collector for on-line analysis of particulate organic matter: the Aerosol Collection Module (ACM)
Authors: Hohaus T. , Trimborn D. , Kiendler-Scharr A. , Gensch I. , Laumer W. , Kammer B. , Andres S. , Boudries H. , Smith K. A. , Worsnop D. R. , Jayne J. T.
Published: April 2010

Abstract. In many environments organic matter significantly contributes to the composition of atmospheric aerosol particles influencing its properties. Detailed chemical characterization of ambient aerosols is critical in order to understand the formation process, composition, and properties of aerosols in the atmosphere. However, current analytical methods are far from full speciation of organic aerosols and often require long sampling times. Offline methods are also subjected to artifacts during aerosol collection and storage. In the present work a new technique for quasi-online compound specific measurements of organic aerosol particles was developed. The Aerosol Collection Module (ACM) is designed to sample, collect and transfer gasified atmospheric aerosol particles. The system focuses particles into a beam which is directed to a cooled sampling surface. The sampling takes places in a high vacuum environment where the gas phase from the sample volume is removed. After collection the particle sample is evaporated from the collection surface through heating and transferred to a detector. For laboratory characterization the ACM was interfaced with a Gas Chromatograph Mass Spectrometer system (GC-MS). The particle collection efficiency, gas phase transfer efficiency, and linearity of the ACM-GC-MS were determined using laboratory generated octadecane aerosols. The ACM-GC-MS is linear over the investigated mass range of 10 to 100 ng and a recovery rate of 100% was found for octadecane particles. The ACM-GC-MS was applied to investigate secondary organic aerosol (SOA) formed from β-pinene oxidation. Nopinone, myrtanal, myrtenol, 1-hydroxynopinone, 3-oxonopinone, 3,7-dihydroxynopinone, and bicyclo[3,1,1]hept-3-ene-2-one were found as products in the SOA. The ACM results are compared to quartz filter samples taken in parallel to the ACM measurements. First measurements of ambient atmospheric aerosols are presented.
An automatic contrail tracking algorithm
Authors: Vazquez-Navarro M. , Mannstein H. , Mayer B.
Published: April 2010

Abstract. A method designed to track the life cycle of contrail-cirrus using satellite data with high temporal and spatial resolution, from its formation to the final dissolution of the aviation-induced cirrus cloud is presented. The method follows the evolution of contrails from their linear stage until they are undistinguishable from natural cirrus clouds. Therefore, the study of the effect of aircraft-induced clouds in the atmosphere is no longer restricted to linear contrails and can include contrail-cirrus. The method takes advantage of the high spatial resolution of polar orbiting satellites and the high temporal resolution of geostationary satellites to identify the pixels that belong to an aviation induced cloud. The high spatial resolution data of the MODIS sensor is used for contrail detection, and the high temporal resolution of the SEVIRI sensor in the Rapid Scan mode is used for contrail tracking. An example is included in which the method is applied to the study of a long lived contrail over the bay of Biscay.
Characterization and intercomparison of aerosol absorption photometers: result of two intercomparison workshops
Authors: Müller T. , Henzing J. S. , de Leeuw G. , Wiedensohler A. , Alastuey A. , Angelov H. , Bizjak M. , Collaud Coen M. , Engström J. E. , Gruening C. , Hillamo R. , Hoffer A. , Imre K. , Ivanow P. , Jennings G. , Sun J. Y. , Kalivitis N. , Karlsson H. , Komppula M. , Laj P. , Li S.-M. , Lunder C. , Marinoni A. , Martins dos Santos S. , Moerman M. , Nowak A. , Ogren J. A. , Petzold A. , Pichon J. M. , Rodriquez S. , Sharma S. , Sheridan P. J. , Teinilä K. , Tuch T. , Viana M. , Virkkula A. , Weingartner E. , Wilhelm R. , Wang Y. Q.
Published: April 2010

Abstract. Absorption photometers for real time application have been available since the 1980s, but the use of filter-based instruments to derive information on aerosol properties (absorption coefficient and black carbon, BC) is still a matter of debate. Several workshops have been conducted to investigate the performance of individual instruments over the intervening years. Two workshops with large sets of aerosol absorption photometers were conducted in 2005 and 2007. The data from these instruments were corrected using existing methods before further analysis. The inter-comparison shows a large variation between the responses to absorbing aerosol particles for different types of instruments. The unit to unit variability between instruments can be up to 30% for Particle Soot Absorption Photometers (PSAPs) and Aethalometers. Multi Angle Absorption Photometers (MAAPs) showed a variability of less than 5%. Reasons for the high variability were identified to be variations in sample flow and spot size. It was observed that different flow rates influence system performance with respect to response to absorption and instrumental noise. Measurements with non absorbing particles showed that the current corrections of a cross sensitivity to particle scattering are not sufficient. Remaining cross sensitivities were found to be a function of the total particle load on the filter. The large variation between the response to absorbing aerosol particles for different types of instruments indicates that current correction functions for absorption photometers are not adequate.
Impact of temperature field inhomogeneities on the retrieval of atmospheric species from MIPAS IR limb emission spectra
Authors: Kiefer M. , Arnone E. , Dudhia A. , Carlotti M. , Castelli E. , von Clarmann T. , Dinelli B. M. , Kleinert A. , Linden A. , Milz M. , Papandrea E. , Stiller G.
Published: April 2010

Abstract. We examine volume mixing ratios (vmr) retrieved from limb emission spectra recorded with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). In level 2 (L2) data products of three different retrieval processors, which perform one dimensional (1-D) retrievals, we find significant differences between species' profiles from ascending and descending orbit parts. The relative differences vary systematically with time of the year, latitude, and altitude. In the lower stratosphere their monthly means can reach maxima of 20% for CFC-11, CFC-12, HNO3, H2O, 10% for CH4 and N2O. Relative differences between monthly means of 1-D retrieval results and of the true atmospheric state can be expected to reach half of these percentage values, while relative differences in single vmr profiles might well exceed those numbers. Often there are no physical or chemical reasons for these differences, so they are an indicator for a problem in the data processing. The differences are generally largest at locations where the meridional temperature gradient of the atmosphere is strong. On the contrary, when performing the retrieval with a tomographic two dimensional (2-D) retrieval, L2 products generally do not show these differences. This implies that inhomogeneities in the temperature field, and possibly in the species' fields, which are accounted for in the 2-D algorithm and not in standard 1-D processors, may cause significant deviations in the results. Inclusion of an externally given adequate temperature gradient in the forward model of a 1-D processor helps to reduce the observed differences. However, only the full tomographic approach is suitable to resolve the horizontal inhomogeneities. Implications for the use of the 1-D data, e.g. for validation, are discussed. The dependence of the ascending/descending differences on the observation strategy suggests that this problem is to be expected to affect in general 1-D retrievals of infrared limb sounders, if the line of sight of the instrument has a significant component in the direction of the horizontal temperature variation.
Measurement of HONO, HNCO, and other inorganic acids by negative-ion proton-transfer chemical-ionization mass spectrometry (NI-PT-CIMS): application to biomass burning emissions
Authors: Roberts J. M. , Veres P. , Warneke C. , Neuman J. A. , Washenfelder R. A. , Brown S. S. , Baasandorj M. , Burkholder J. B. , Burling I. R. , Johnson T. J. , Yokelson R. J. , de Gouw J.
Published: April 2010

Abstract. A negative-ion proton transfer chemical ionization mass spectrometric technique (NI-PT-CIMS), using acetate as the reagent ion, was applied to the measurement of volatile inorganic acids of atmospheric interest: hydrochloric (HCl), nitrous (HONO), nitric (HNO3), and isocyanic (HNCO) acids. Gas phase calibrations through the sampling inlet showed the method to be intrinsically sensitive (6–16 cts/pptv), but prone to inlet effects for HNO3 and HCl. The ion chemistry was found to be insensitive to water vapor concentrations, in agreement with previous studies of carboxylic acids. The inlet equilibration times for HNCO and HONO were 2 to 4 s, allowing for measurement in biomass burning studies. Several potential interferences in HONO measurements were examined: decomposition of HNO3·NO3- clusters within the CIMS, and NO2-water production on inlet surfaces, and were quite minor (≤1%, 3.3%, respectively). The detection limits of the method were limited by the instrument backgrounds in the ion source and flow tube, and were estimated to range between 16 and 50 pptv (parts per trillion by volume) for a 1 min average. The comparison of HONO measured by CIMS and by in situ FTIR showed good correlation and agreement to within 17%. The method provided rapid and accurate measurements of HNCO and HONO in controlled biomass burning studies, in which both acids were seen to be important products.
Potential for the use of reconstructed IASI radiances in the detection of atmospheric trace gases
Authors: Atkinson N. C. , Hilton F. I. , Illingworth S. M. , Eyre J. R. , Hultberg T.
Published: April 2010

Abstract. Principal component (PC) analysis has received considerable attention as a technique for the extraction of meteorological signals from hyperspectral infra-red sounders such as the Infrared Atmospheric Sounding Interferometer (IASI) and the Atmospheric Infrared Sounder (AIRS). In addition to achieving substantial bit-volume reductions for dissemination purposes, the technique can also be used to generate reconstructed radiances in which random instrument noise has been suppressed. To date, most studies have been in the context of Numerical Weather Prediction (NWP). This study examines the potential of PC analysis for chemistry applications. A major concern in the use of PC analysis for chemistry has been that the spectral features associated with trace gases may not be well represented in the reconstructed spectra, either due to deficiencies in the training set or due to the limited number of PC scores used in the radiance reconstruction. In this paper we show examples of reconstructed IASI radiances for several trace gases: ammonia, sulphur dioxide, methane and carbon monoxide. It is shown that care must be taken in the selection of spectra for the initial training set: an iterative technique, in which outlier spectra are added to a base training set, gives the best results. For the four trace gases examined, the chemical signatures are retained in the reconstructed radiances, whilst achieving a substantial reduction in instrument noise. A new regional re-transmission service for IASI is scheduled to start in 2010, as part of the EUMETSAT Advanced Retransmission Service (EARS). For this EARS-IASI service it is intended to include PC scores as part of the data stream. The paper describes the generation of the reference eigenvectors for this new service.
Retrievals from GOMOS stellar occultation measurements using characterization of modeling errors
Authors: Sofieva V. F. , Vira J. , Kyrölä E. , Tamminen J. , Kan V. , Dalaudier F. , Hauchecorne A. , Bertaux J.-L. , Fussen D. , Vanhellemont F. , Barrot G. , Fanton d'Andon O.
Published: April 2010

Abstract. In this paper, we discuss the development of the inversion algorithm for the GOMOS (Global Ozone Monitoring by Occultation of Star) instrument on board the Envisat satellite. The proposed algorithm takes accurately into account the wavelength-dependent modeling errors, which are mainly due to the incomplete scintillation correction in the stratosphere. The special attention is paid to numerical efficiency of the algorithm. The developed method is tested on a large data set and its advantages are demonstrated. Its main advantage is a proper characterization of the uncertainties of the retrieved profiles of atmospheric constituents, which is of high importance for data assimilation, trend analyses and validation.
Comparison of one- and two-filter detectors for atmospheric 222Rn measurements
Authors: Xia Y. , Sartorius H. , Schlosser C. , Stöhlker U. , Conen F. , Zahorowski W.
Published: April 2010

Abstract. Parallel monitoring of 222Rn and its short-lived progeny (218Po and 214Pb) were carried out from November 2007 to April 2008 close to the top of the Schauinsland mountain, partly covered with forest, in South-West Germany. Samples were aspired from the same location at 2.5 m above ground level. We measured 222Rn with a dual flow loop, two-filter detector and its short-lived progeny with a one-filter detector. A reference sector for events, facing a steep valley and dominated by pasture, was used to minimize differences between 222Rn and progeny-derived 222Rn activity concentrations. In the two major wind sectors covered by forest to a distance between 60 m and 80 m towards the station progeny-derived 222Rn activity concentration was on average equal to 87% (without precipitation) and 74% (with precipitation) of 222Rn activity concentration.
Uncertainty of VNA S-parameter measurement due to non-ideal TMSO or LMSO calibration standards
Authors: Stumper U.
Published: April 2010

Abstract. For the widespread 12-term TMSO and LMSO calibration of 4-sampler vector network analyzers (VNA), the sensitivity coefficients of the S-parameters of two-ports are developed as functions of the deviations of the reflection coefficients of the one-port calibration standards and of an imperfect through or line connection. Expressions representing the deviations of the S-parameters with respect to the error terms and for the deviations of the error terms with respect to the non-ideal calibration standards are also given. It is shown that the deviations of the S-parameters become quite large particularly for high-reflective two-port test objects. If applying a broadband load (instead of using the time consuming “ideal" sliding load routine) and the VNA-internal firmware-operated calibration and evaluation routines where the reflection coefficient is set to zero, deviations may appear of some 0,1 dB for the attenuation and some degrees of the transmission phase angle.
High resolution radar for automobile applications
Authors: Schneider R. , Wenger J.
Published: April 2010

Abstract. This contribution points out the potential of radar sensors with high resolution in azimuth and range in traffic environment and addresses some aspects of their practical implementation with respect to system design, hardware and software. A prototypical vehicle-based instrumentation radar is presented, which performs on-line acquisition and real-time visualisation of radar images with an update rate of up to 10 Hz. The enhanced perception capabilities of high resolution radar in traffic environment will be demonstrated with respect to new comfort and safety features, and practical realisation approaches concerning data processing and hardware including the scanning antenna will be discussed.
Millimetre-wave imaging with reduced number of degrees of freedom in array signal processing: concepts for enhanced angular resolution
Authors: Kotyrba G. , Chaloupka H.
Published: April 2010

Abstract. This paper deals with millimetre-wave imaging systems based on linear receiving arrays and is focused on the issue of angular resolution and coverage for arrays where the number M of ports is smaller than the number N of elements due to forming of subarrays. For a wide angular coverage a trade-off between a narrow beam width and a high side-lobe suppression is shown to occur which requires proper synthesis of the subarray pattern. Two concepts for an enhanced angular resolution are presented. The first uses a combination of a frequency dependent distribution network (frequency scanning) with array signal processing to enhance angular resolution by cost of a reduced range resolution. The second approach takes advantage of relative movements to enhance angular resolution via a combined angular and temporal (Doppler) processing.
Spectral Signature Analysis – BIST for RF Front-Ends
Authors: Lupea D. , Pursche U. , Jentschel H.-J.
Published: April 2010

Abstract. In this paper, the Spectral Signature Analysis is presented as a concept for an integrable self-test system (Built-In Self-Test – BIST) for RF front-ends is presented. It is based on modelling the whole RF front-end (transmitter and receiver) on system level, on generating of a Spectral Signature and of evaluating of the Signature Response. Because of using multi-carrier signal as the test signature, the concept is especially useful for tests of linearity and frequency response of front-ends. Due to the presented method of signature response evaluation, this concept can be used for Built-In Self-Correction (BISC) at critical building blocks.
A novel bottom-left packing genetic algorithm for analog module placement
Authors: Zhang L. , Kleine U.
Published: April 2010

Abstract. This paper presents a novel genetic algorithm for analog module placement. It is based on a generalization of the two-dimensional bin packing problem. The genetic encoding and operators assures that all constraints of the problem are always satisfied. Thus the potential problems of adding penalty terms to the cost function are eliminated, so that the search configuration space decreases drastically. The dedicated cost function covers the special requirements of analog integrated circuits. A fractional factorial experiment was conducted using an orthogonal array to study the algorithm parameters. A meta-GA was applied to determine the optimal parameter values. The algorithm has been tested with several local benchmark circuits. The experimental results show this promising algorithm makes the better performance than simulated annealing approach with the satisfactory results comparable to manual placement.
A software-radio front-end for microwave applications
Authors: Streifinger M. , Müller T. , Luy J.-F. , Biebl E. M.
Published: April 2010

Abstract. In modern communication, sensor and signal processing systems digitisation methods are gaining importance. They allow for building software configurable systems and provide better stability and reproducibility. Moreover digital front-ends cover a wider range of applications and have better performance compared with analog ones. The quest for new architectures in radio frequency front-ends is a clear consequence of the ever increasing number of different standards and the resulting task to provide a platform which covers as many standards as possible. At microwave frequencies, in particular at frequencies beyond 10 GHz, no direct sampling receivers are available yet. A look at the roadmap of the development of commercial analog-to-digital-converters (ADC) shows clearly, that they can neither be expected in near future. We present a novel architecture, which is capable of direct sampling of band-limited signals at frequencies beyond 10 GHz by means of an over-sampling technique. The wellknown Nyquist criterion states that wide-band digitisation of an RF-signal with a maximum frequency ƒ requires a minimum sampling rate of 2 · ƒ . But for a band-limited signal of bandwidth B the demands for the minimum sampling rate of the ADC relax to the value 2 · B. Employing a noise-forming sigma-delta ADC architecture even with a 1-bit-ADC a signal-to-noise ratio sufficient for many applications can be achieved. The key component of this architecture is the sample-and-hold switch. The required bandwidth of this switch must be well above 2 · ƒ . We designed, fabricated and characterized a preliminary demonstrator for the ISM-band at 2.4 GHz employing silicon Schottky diodes as a switch and SiGe-based MMICs as impedance transformers and comparators. Simulated and measured results will be presented.
Incremental refinement of a multi-user-detection algorithm (II)
Authors: Vollmer M. , Götze J.
Published: April 2010

Abstract. Multi-user detection is a technique proposed for mobile radio systems based on the CDMA principle, such as the upcoming UMTS. While offering an elegant solution to problems such as intra-cell interference, it demands very significant computational resources. In this paper, we present a high-level approach for reducing the required resources for performing multi-user detection in a 3GPP TDD multi-user system. This approach is based on a displacement representation of the parameters that describe the transmission system, and a generalized Schur algorithm that works on this representation. The Schur algorithm naturally leads to a highly parallel hardware implementation using CORDIC cells. It is shown that this hardware architecture can also be used to compute the initial displacement representation. It is very beneficial to introduce incremental refinement structures into the solution process, both at the algorithmic level and in the individual cells of the hardware architecture. We detail these approximations and present simulation results that confirm their effectiveness.
Organic Field-Effect-Transistors with Pentacene for radio-controlled-price-tag applications
Authors: Pannemannn C. , Diekmann T. , Hilleringmann U.
Published: April 2010

Abstract. This letter presents organic thin-film-transistors (OTFT) using the small organic molecule Pentacene targeting applications like radio controlled identification tags. Simple OTFTs as well as inverter circuits based on a pconducting silicon wafer substrate are presented. Comparing PECVD oxide and LTO as dielectric, only LTO deposited layers provide sufficient electrical stability. PECVD oxides show defects called “pin-holes", leading to short circuiting through the gate dielectrics. OTFTs of L=1µm/W=1000µm were prepared providing Ids = 61µA at –40Vds and –40Vgs, a subthreshold slope of 10.3 V/dec and an on-offratio of 102. The inverter circuits using insulated gate contacts switch from VA=–10V to VA=–3V output voltage when the input voltage is varied from VE=0V to VE=–8V at a supplied voltage of VB=–10V.
Test signal generation for analog circuits
Authors: Burdiek B. , Mathis W.
Published: April 2010

Abstract. In this paper a new test signal generation approach for general analog circuits based on the variational calculus and modern control theory methods is presented. The computed transient test signals also called test stimuli are optimal with respect to the detection of a given fault set by means of a predefined merit functional representing a fault detection criterion. The test signal generation problem of finding optimal test stimuli detecting all faults form the fault set is formulated as an optimal control problem. The solution of the optimal control problem representing the test stimuli is computed using an optimization procedure. The optimization procedure is based on the necessary conditions for optimality like the maximum principle of Pontryagin and adjoint circuit equations.
CMOS-Empfängerschaltungen für Hochgeschwindigkeits-Datenübertragung nach LVDS-Standard
Authors: Hirsch S. , Pfleiderer H.-J.
Published: April 2010

Abstract. Für die schnelle Datenübertragung zwischen einzelnen IC’s auf einer Leiterplatte kann der “IEEE-Standard für LVDS (Low Voltage Differential Signals)" verwendet werden. Um die Anforderungen, die dieser Standard an die Empfängerschaltungen stellt, erfüllen zu können, sind spezielle Schaltungen nötig, die mit einem sehr kleinen Differenzsignal am Eingang und einem stark variierenden Arbeitspunkt betrieben werden können. Es werden verschiedene Schaltungen, die diese Bedingungen erfüllen, vorgestellt und durch Simulation miteinander verglichen. Die beiden erfolgversprechendsten Schaltungen wurden auf der Basis eines Full Custom Layouts in einer CMOS-Technologie realisiert und vermessen.
Outdoor radiolinks for 2.4 GHz-frequencies: measurement results and experiences within the radio communication network “Intermobil Region Dresden"
Authors: Michler O.
Published: April 2010

Abstract. The radio communication network “Intermobil Region Dresden" was developed and built up for data transmission of traffic videos and other traffic data. It uses Pointto- Point (PtP) and Point-to-Multipoint (PtM) bridges, forming the backbone structure. The traffic camera radio clients link up with Accesspoints, installed at the nodal points of the backbone. This paper analyses the physical and technical conditions, building up such radio communication networks. The radio channel properties (e.g. total path loss, multipath propagation) and the technical parameters (e.g. transmission power, sensitivity, antenna gain) belong to this conditions. Based on calculation and spreading measurements it is shown, that reserves have to be considered during the planning already. As well special problems, like Fresnel-zone clearance and shadowing are discussed. The choice of the antenna plays a key role for planning and building of wireless networks. It determines decisively the range and gives an important contribution to elimination of wireless disturbances (interferences). Dependent on topological facts, installation environment and wireless distance omnidirectional-, yagi-, patch- and parabol-antennas are used. Based on antenna measurements the paper discusses the use and property of decoupling. WLANs are working in the license free 2.4 GHz-band. The number of radio systems in this band increases permanently, which leads to a lot of interferences among each other. The paper makes a classification of possible interference sources and discusses their influence on transmission quality. Technical solutions are shown for increase interference robustness.
The new era of large paraboloid antennas: the life of Prof. Dr. Otto Hachenberg
Authors: Wielebinski R.
Published: April 2010

Abstract. Seldom does a scientist get an opportunity in his lifetime to build an instrument that remains unchallenged as the world’s no. 1 for 30 years. The Effelsberg 100- m radio telescope, constructed under the direction of Prof. Dr. Otto Hachenberg, was the world’s largest fully steerable paraboloid antenna since its inauguration in 1971. The radio telescope in a valley in the Eifel mountains near Bonn was constructed with a remarkably precise surface and excellent pointing characteristics. Only in 2001 the 100-m × 110-m Green Bank Telescope became operational and marginally surpassed Effelsberg’s performance. The Effelsberg telescope is still fully operational in 2002 and looking forward to an exciting future. It is a memorial to the ingenuity of a person who influenced the development of German radio astronomy.
Definition of a parameter for a typical specific absorption rate under real boundary conditions of cellular phones in a GSM networkd
Authors: Gerhardt D.
Published: April 2010

Abstract. Using cellular phones the specific absorption rate (SAR) as a physical value must observe established and internationally defined levels to guarantee human protection. To assess human protection it is necessary to guarantee safety under worst-case conditions (especially maximum transmitting power) using cellular phones. To evaluate the exposure to electromagnetic fields under normal terms of use of cellular phones the limitations of the specific absorption rate must be pointed out. In a mobile radio network normal terms of use of cellular phones, i.e. in interconnection with a fixed radio transmitter of a mobile radio network, power control of the cellular phone as well as the antenna diagram regarding a head phantom are also significant for the real exposure. Based on the specific absorption rate, the antenna diagram regarding a head phantom and taking into consideration the power control a new parameter, the typical absorption rate (SARtyp), is defined in this contribution. This parameter indicates the specific absorption rate under average normal conditions of use. Constant radio link attenuation between a cellular phone and a fixed radio transmitter for all mobile models tested was assumed in order to achieve constant field strength at the receiving antenna of the fixed radio transmitter as a result of power control. The typical specific absorption rate is a characteristic physical value of every mobile model. The typical absorption rate was calculated for 16 different mobile models and compared with the absorption rate at maximum transmitting power. The results confirm the relevance of the definition of this parameter (SARtyp) as opposed to the specific absorption rate as a competent and applicable method to establish the real mean exposure from a cellular phone in a mobile radio network. The typical absorption rate provides a parameter to assess electromagnetic fields of a cellular phone that is more relevant to the consumer.
Kontinuierliche und diskrete Differenzialformen als Ausgangspunkt für numerische Methoden in der Elektrodynamik
Authors: Kurz S.
Published: April 2010

Abstract. Die Grundgleichungen der Elektrodynamik werden häufig in integraler Form aufgestellt. Die Umwandlung in partielle Differenzialgleichungen geschieht dann durch Anwendung der Integralsätze von Gauss und Stokes. Beide Integralsätze besitzen eine große formale Ähnlichkeit. Formuliert man die Maxwellschen Gleichungen mit Hilfe von Differenzialformen, wird diese zunächst formale Analogie verständlich, als Konsequenz eines abstrakteren Konzeptes. Neben der damit einhergehenden übersichtlichen und eleganten Darstellung der Elektrodynamik erhält man einen gut geeigneten Ausgangspunkt für numerische Methoden. Differenzialformen besitzen natürliche Entsprechungen im Diskreten, die diskreten Differenzialformen. Das hieraus in niedrigster Ordnung resultierende Diskretisierungsschema entspricht der Allokation von Freiheitsgraden auf zueinander dualen Gittersystemen, wie sie von der FIT (= Finite Integration Technique) bekannt ist. Größere Freiheiten hat man bei der Diskretisierung der Materialbeziehungen, die auf diskrete Hodge-Operatoren führt. Je nach verwendetem Ansatz (orthogonale oder baryzentrische duale Gitter) erhält man unterschiedliche numerische Verfahren. Kontinuierliche und diskrete Differenzialformen können deshalb als allgemeiner Ausgangspunkt für numerische Methoden in der Elektrodynamik betrachtet werden. The fundamental laws of electrodynamics are often stated in integral form. The conversion to partial differential equations is conveyed by application of the integral theorems of Gauss and Stokes. Both theorems bear a strong formal resemblance. If Maxwell’s equations are reformulated in terms of differential forms this seemingly formal analogy will become obvious, as a consequence of a more abstract underlying concept. Besides the accompanying concise and elegant formulation of electrodynamics a useful starting point for numerical methods is obtained. Differential forms possess natural correspondents in the discrete setting, the so called discrete differential forms. The resulting discretization scheme of lowest order corresponds to the allocation of degerees of freedom on dual grid pairs, which is well known from the FIT (= Finite Integration Technique). There is more freedom when the constitutive equations are to be discretized, which yields discrete Hodge operators. Depending on the employed technique (orthogonal or barycentric dual grids) one ends up with different numerical schemes. Continuous and discrete differential forms can therefore be regarded as a general starting point for numerical methods in electrodynamics.
Dielectric microwave sensors with multivariate calibration
Authors: Daschner F. , Knöchel R.
Published: April 2010

Abstract. The composition of materials generally has an influence on its dielectric properties. Hence it may be possible to determine their composition using microwave dielectric spectra. However with complex materials like foodstuffs it is difficult to devise a suitable dielectric model. Therefore multivariate calibration methods are discussed here. With these calibrations it is also possible to process the measured scattering parameters directly. In this case it is not necessary to calculate the permittivity and more degrees of freedom are available for the design of a sensor. The direct processing of the S-parameters is demonstrated with a new transmissionline sensor.