This dissertation is a collection of works that investigates issues related to environmental chemistry. The first portion of this research explores the role of water vapor on the kinetics of important atmospheric reactions. Work is presented on the self-reaction of β-hydroxyethyl peroxy radical (β-HEP) and the catalytic increase in reaction rate by water vapor. β-HEP serves as a model system for investigating the possible role of water vapor in perturbing the kinetics and product branching ratio of atmospheric reactions of other alkyl peroxy radicals. The self-reaction rate coefficient of β-HEP was investigated between 276-296 K with 1.0 × 10^15 to 2.5 × 10^17 molecules cm^-3 of water vapor at 200 Torr total pressure by slow-flow laser flash photolysis coupled with UV time-resolved spectroscopy and long-path, wavelength-modulated, diode-laser spectroscopy. The overall disproportionation rate constant is expressed as the product of temperature-dependent and water vapor-dependent terms giving k(T,H2O) = 7.8 × 10^-14 (e^8.2 ^(±2.5) ^kJ/RT)(1 + 1.4 × 10^-34 × e^92 ^(±11) ^kJ/RT[H2O]). The results suggest that formation of a β--HEP-H2O complex is responsible for the observed water vapor enhancement of the self-reaction rate coefficient. Complex formation is supported with computational results identifying three local energy minima for the β--HEP-H2O complex. Both the temperature range and water vapor concentrations used were chosen because of their significance to conditions in the troposphere. As the troposphere continues to get warmer and wetter, more complexes with water will form, which in turn may perturb the kinetics and product branching ratios of atmospheric reactions. Future studies are proposed for the reaction of β-HEP + NO leading to NO2 formation. A laser-induced fluorescence cell was designed, built, and tested in preparation for studies of NO2 formation. Additionally Harriott-cell optics were manufactured and tested to detect HO2 using two-tone frequency-modulated diode-laser spectroscopy. In a related work, the breakdown of the environmental contaminants polychlorinated biphenyls (PCB's) was investigated using a new method. A new method for analyzing anaerobic digestion is also presented. The degradation rate and efficiency of digestion processes are typically measured by introducing a substrate or pollutant into a digester and then monitoring the effluents for the pollutant or substrate, a costly and slow process. A new method for rapid measurement of the rates and efficiencies of anaerobic degradation of pollutants and lignocellulose substrates from various pretreatments is described. The method uses micro-reactors (10-30 mL) containing a mixed culture of anaerobic bacteria obtained from a working anaerobic digester. The rates of degradation and metabolism of pollutants are measured in parallel sets of micro-reactors. Measurements of metabolic rate and pollutant degradation simultaneously is an effective means of rapidly examining pollutant degradation on a micro-scale. Calorimetric measurements alone allow rapid, relative evaluation of various substrate pretreatment methods. Finally calorimetric and electrophoretic methods were used to further knowledge in analytical techniques applied to important problems. In the last section of this dissertation the thermal and photolytic breakdown of promethazine hydrochloride is reported. Promethazine hydrochloride is a mediation that is commonly used as an antihistamine, a sedative, and an antiemetic, and to treat motion sickness. Perivascular extravasation, unintentional intra-arterial injection and intraneuronal or perineuronal infiltration may lead to irreversible tissue damage if the drug is not properly diluted or is administered too quickly. Data on the stability of promethazine hydrochloride diluted in sodium chloride 0.9% are lacking. This study evaluates the thermal and photolytic degradation of promethazine hydrochloride concentrations of 250 µg/mL and 125 µg/mL diluted in sodium chloride 0.9% over a period of 9 days. Degradation rates of promethazine hydrochloride were determined under UV-light, fluorescent light, and no light at various temperatures and concentrations to determine medication stability. The shelf-life (<10% degradation) at 25°C under normal fluorescent lights is 4.9 days, at 25°C protected from light, 6.6 days, and at 7°C in the dark, 8.1 days. These results may increase patient safety by improving current protocols for intravenous promethazine administration

Obesity and mobile phone usage have simultaneously spread worldwide. Radio frequency-modulated electromagnetic fields (RF-EMFs) emitted by mobile phones are largely absorbed by the head of the user, influence cerebral glucose metabolism, and modulate neuronal excitability. Body weight adjustment, in turn, is one of the main brain functions as food intake behavior and appetite perception underlie hypothalamic regulation. Against this background, we questioned if mobile phone radiation and food intake may be related. In a single-blind, sham-controlled, randomized crossover comparison, 15 normal-weight young men (23.47 ± 0.68 years) were exposed to 25 min of RF-EMFs emitted by two different mobile phone types vs. sham radiation under fasting conditions. Spontaneous food intake was assessed by an ad libitum standard buffet test and cerebral energy homeostasis was monitored by 31phosphorus-magnetic resonance spectroscopy measurements. Exposure to both mobile phones strikingly increased overall caloric intake by 22–27% compared with the sham condition. Differential analyses of macronutrient ingestion revealed that higher calorie consumption was mainly due to enhanced carbohydrate intake. Measurements of the cerebral energy content, i.e., adenosine triphosphate and phosphocreatine ratios to inorganic phosphate, displayed an increase upon mobile phone radiation. Our results identify RF-EMFs as a potential contributing factor to overeating, which underlies the obesity epidemic. Beyond that, the observed RF-EMFs-induced alterations of the brain energy homeostasis may put our data into a broader context because a balanced brain energy homeostasis is of fundamental importance for all brain functions. Potential disturbances by electromagnetic fields may therefore exert some generalized neurobiological effects, which are not yet foreseeable.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In recent years Autonomous Underwater Vehicles (AUVs) have become interesting for harbor mapping and protection. AUVs require a SONAR sensor for observing their surroundings, thus enabling them to perform collision avoidance manoeuvres and scanning their operating environment for intruders or foreign objects, e.g. mines. To perform such actions the SONAR sensor is required to supply very fine range resolution for target imaging, as well as providing information about possible target velocity. Basic SONAR theory is discussed, as well as different approaches to signal design and processing techniques, for achieving the required resolution in range and target velocity. Two of the discussed approaches are selected for processing range and target velocity, respectively. Both approaches are simulated for their validity before being tested by using a custom-built platform. The platform is highly configurable and designed for capacity of testing a variety of SONAR signals and set ups. Furthermore, the platform is built by using off-the-shelf components to minimize development costs. The results of simulations and practical tests are presented. A high correlation between theory and practice is achieved. The knowledge and the platform presented form the stepping stone for further SONAR sensor developments. / AFRIKAANSE OPSOMMING: In die laaste jare het outonome onderwater voertuie (OOV) toenemend belangrik geword vir die kartografie en beskerming van hawens. OOV’s vereis SONAR sensore wat hulle in staat stel, om hulle omgewing waar te neem en sodoende botsing vermydings take te verrig en ook om hul werksomgewing noukeurig te skandeer om indringers of vreemde voorwerpe, bv. myne, op te spoor. Om sulke werk te verrig, word van die SONAR sensor vereis, om baie fyn afstand oplossings vir teiken te verskaf, insluitend die moontlike snelheid van die teiken. Basiese SONAR teorie word bespreek, en dan verskeie benaderings van sein ontwerp en verwerkings tegnieke. Twee van die bespreekte benaderings word gekies om afstand en teiken snelheid onderskeidelik te verwerk. Altwee benaderings word gesimuleer om hul geldigheid vas te stel, voor dat hulle getoets word op ’n pasmaat vervaardigde platform. Die platform is hoogs aanpasbaar en is ontwerp vir sy vermoë om ’n verskeidenheid SONAR seine en verwerkings te hanteer. Verder is die platform vervaardig met standard rakonderdele om ontwikkelingskoste so laag as moontlik te hou. Die uitslae van die simulerings en praktiese toetse word voorgestel. ’n Hoë mate aan korrelasie is bereik tussen teorie en praktyk. Die kennis en die platvorm, wat hier voorgestel word, vorm die eerste trappie vir toekomstige SONAR sensor ontwikkeling.

The speech signal is inherently characterized by its variations in time, which get reflected as variations in frequency. The specto temporal changes are due to changes in vocaltract, intonation, co-articulation and successive articulation of different phonetic sounds. In this thesis we are looking for improving the speech recognition performance through better feature parameters using a non-stationary model of speech. One effective means of modeling a general non-stationary signal is using the AM-FM model. AM-FM model can be extended to speech through a sub-band analysis, which can be mimic the auditory analysis. In this thesis, we explore new methods for estimating AM and FM parameters based on the non-uniform samples of the signal. The non-uniform sample approach along with adaptive window estimation provides for important advantage because of multi-resolution analysis. We develop several new methods based on ZC intervals, local extrema intervals and signal derivative at ZC’s as different sample measures of the signal and explore their effectiveness for instantaneous frequency (IF) and instantaneous envelope (IE) estimation. To deal with speech signal for automatic speech recognition, we explore the use of auditory motivated spectro temporal information through the use of an auditory filter bank and signal parameters (or features) are derived from the instantaneous energy in each band using the non-linear energy operator over a larger window length. The temporal correlation present in the signal is exploited by using DCT and keeping the lower few coefficients of DCT to keep the trend in the energy in each band. The DCT coefficients from different frequency bands are concatenated together, and a further spectral decorrelation is achieved through KLT (Karhunen-Loeve Transform) of the concatenated feature vector. The changes in the vocaltract are well captured by the change in the formant structure and to emphasize these details for ASR we have defined a temporal formant by using the AM-FM decomposition of sub-band speech. A uniform wideband non-overlaping filters are used for sub-band decomposition. The temporal formant is defined using the AM-FM parameters of each subband signal. The temporal evolution of a formant is represented by the lower order DCT coefficients of the temporal formant in each band and its use for ASR is explored. To address the robustness of ASR performance to environmental noisy conditions, we have used a hybrid approach of enhancing the speech signal using statistical models of the speech and noise. Use of GMM for statistical speech enhancement has been shown to be effective. It is found that the spectro-temporal features derived from enhanced speech provide further improvement to ASR performance.

Thesis (MEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Large close range environmental reflections or poor isolation between the transmit and receive paths of an FMCW radar can overload the receiver. The In phase and Quadrature phase (IQ) Reflected Power Canceller (RPC) provides a solution to the problem by cancelling any close range reflections. In this study a procedure to optimise the design of an RPC is developed and the performance limits of a practical RPC is investigated in depth. There are four focus areas in the evaluation and design of the IQ Reflected Power Canceller. First, an analysis was performed on a theoretical IQ Reflected Power Canceller, which provided insight into how the system functioned and made it possible to identify practical application issues that would arise during the design. The next focus area was the IQ Reflected Power Canceller’s dynamic range. Equations, based on the power and noise characteristics of each component in the canceller, were derived. From these equations, a system, with an optimised dynamic range, could be developed. Next, the IQ Reflected Power Canceller’s feedback loop stability was investigated. The canceller is an active negative feedback control system but, in order to obtain the negative feedback, the feedback signal has to be phase shifted by 180 degrees to the phase of the input signal. An analysis of the canceller’s RF phase contribution resulted in an equation that can be used to manage the nett RF phase in the feedback loop. The evaluation model of the IQ Reflected Power Canceller produced favourable results. The tests performed on the system included measuring the level of cancellation that can be achieved, whether the dynamic range corresponds to the predicted values and the amount of RF phase error that can be introduced in the feedback path while maintaining a stable system. The IQ Reflected Power Canceller was found to perform well in the evaluation. It provided a cancellation of more than 45 dB for close range reflections and the canceller remained stable across a wide range of RF centre frequencies (1 GHz). This means that the FMCW radar’s frequency modulation bandwidth will not be limited because of the IQ Reflected Power Canceller. The evaluation clearly showed that the modulator in the feedback loop is the critical element that determines the dynamic range of the radar with an RPC. / AFRIKAANSE OPSOMMING: Onvoldoende isolasie tussen die sender en ontvanger van ’n Frekwensie Gemoduleerde Kontinu Golf radar, sowel as groot weerkaatsings vanaf voorwerpe in die omgewing van die radar, veroorsaak dat die ontvanger versadig. Hierdie beperking veroorsaak dat die radar ’n verminderde dinamiese bereik het, en daarmee ook dat die radar se maksimum teiken-afstand verminder word. Die IQ Gereflekteerde Drywingskanselleerder kan as ’n oplossing gebruik word teen hierdie ongewenste refleksies. Hierdie navorsing poog om ’n kanselleerder te evalueer met die eind doel gestel daarop om ’n praktiese stelsel aanmekaar te sit. Die kanselleerder word geëvalueer deur na vier fokus areas te kyk. Eerstens word ’n ideale model opgestel, wat ’n beter begrip van die kanselleerder bewerkstellig. Uit hierdie ideale model, is daar praktiese oorwegings wat die kanselleerder affekteer, geïdentifiseer. Ten einde die dinamiese bereik van die radar ontvanger te verbeter, word ’n metode afgelei wat gebruik word om die kanselleerder se dinamiese bereik te optimeer. Hierdie metode neem die maksimum drywingsbeperkinge van die komponente in die kanselleerder in ag. Die kanselleerder is ’n aktiewe terugvoer beheerstelsel, en aangesien ’n sommeerder in die terugvoer lus gebruik word, moet die fase deur die lus met 180 grade geskuif word om sodoende ’n kansellerende sein by die ontvangde sein te tel. Die RF fase foute in die kanselleerder word geanaliseer deur ’n nie-ideale model van die kanselleerder op te stel. Hierdie nie-ideale model maak dit moontlik om die effek van ’n RF fase fout op die kanselleerder se stabiliteit te ondersoek. ’n Praktiese kanselleerder is ontwerp uit die inligting wat versamel is gedurende die evaluasie, en ’n werkende stelsel is aanmekaar gesit. Met hierdie praktiese kanselleerder is die hoeveelheid drywing-onderdrukking wat bereik kan word, gemeet. Die dinamiese bereik van die kanselleerder is ook bepaal en vergelyk met die teoreties berekende waardes. Die aannames oor die effek van die RF fase fout in die kanselleerder, is bevestig deur metings te neem. Goeie resultate is met die kanselleerder behaal. ’n Kansellasie van meer as 45 dB is gemeet vir naby-geleë refleksies. Die kanselleerder het ook stabiel gebly oor ’n wye band van senter-frekwensies (1 GHz). Dus sal die Frekwensie Gemoduleerde Kontinu Golf radar se modulasie bandwydte nie beperk word as gevolg van die kanselleerder nie. Uit die evaluasie is daar gevind dat die modulator die kritieke element in the kanselleerder se terugvoer lus is, dus bepaal die modulator die dinamiese bereik van die radar met ’n kanselleerder.

<div>Target detection, estimation, and discrimination have long been important research issues in the field of radar. Waveform design, analog signal processing, and digital signal processing are some techniques that can improve the detection, estimation, and discrimination ability. In this dissertation, we first address the sidelobe suppression from the waveform design point of view. We synthesize a non-constant modulus waveform for illumination of radar targets by applying a collection of constant modulus (linear frequency modulated (LFM) waveforms with different frequency offsets) waveforms from each transmitting array element in an antenna array, and we show from the ambiguity function that the non-constant modulus waveform has better performance with respect to the larger ambiguity function mainlobe-to-peak-sidelobe ratio than this ratio of a constant modulus (LFM-only) waveform. Furthermore, from the angular resolution point of view, the synthesized non-constant modulus waveform also has better performance than the angular resolution of a constant modulus waveform at the expense of the decrease in the signal energy on targets.</div><div><br></div><div>Secondly, we investigate radar delay-Doppler resolution enhancement from the digital signal processing viewpoint. We introduce the noise-target fringe analysis technique and combine it with the coherent CLEAN algorithm to provide accurate target parameter estimates in terms of delay, Doppler shift and intensity. Furthermore, the accuracy of target parameter estimates can be further improved by applying weighted non-linear least squares estimation.</div><div><br></div><div>Finally, we further aim for the improvement in radar delay-Doppler resolution. Instead of using the matched filter only, we propose a hybrid filter which combines a chirp matched filter and chirp mismatched filters. The hybrid filter output response shows much better performance in delay and Doppler resolution compared to the chirp matched filter output response. Thus, this hybrid filter design has better target identification capability than the original chirp matched filter. Furthermore, from a real implementation perspective, there is no need to significantly increase the hardware and software complexity of the radar, since we only need to mismatch the received waveform to another chirp waveform and perform some additional non-linear processing. Then a chirp radar system with high delay-Doppler resolution and accurate target discrimination ability can be easily achieved.</div>

Diese Diplomarbeit stellt den Entwurf eines frequenzmodulierten Dauerstrichradars (FMCW) mit ultrabreitbandigem Frequenzbereich von 50 MHz bis 3 GHz unter Verwendung kommerziell verfügbarer Komponenten (COTS) für die Anwendung als Bodenradar in einer Mondlandeeinheit dar. Dazu werden dem Stand der Technik entsprechende Topologien zur Erzeugung ultrabreitbandiger Signale aufgezeigt und analysiert. Die theoretischen Hintergründe einer Aufteilung des Frequenzsweeps und der späteren Zusammensetzung des Beatsignals werden behandelt. Die Entwürfe der Schaltung, des Layouts und der Software werden erläutert. Bei der Charakterisierung des Radarsystems stellt sich heraus, dass die geforderten Eigenschaften unter dem Einfluss eines Temperaturbereichs von −40 °C bis 75 °C bzw. bei Bestrahlung mit einer Gesamtdosis bis 168 Gy erreicht werden können und die Verwendung von modernen COTS Komponenten die Performance nicht einschränkt. Abschließend werden Verbesserungsvorschläge für Hard- und Software gegeben, welche sich während der Arbeit mit dem System ergeben haben. / This thesis presents the design of a miniature frequency modulated continuous wave (FMCW) radar with a frequency range of 50 MHz to 3 GHz using only commercial off the shelf (COTS) components. The system is intended for use as ground penetrating radar (GPR) as part of a lunar lander. State of the art topologies for ultra wideband signal synthesis are presented and compared. The theoretical background of split frequency ramps and the thus required stitching of baseband signals is discussed. The schematic design, layout and software development is described. The characterization of the radar system shows that the specification is met within a temperature range of −40 °C to 75 °C and while exposition to radiation with an accumulated dose of up to 168 Gy. The use of COTS components does not impair the performance. Finally suggestions for hard- and software improvements are given, that resulted from working with the radar system.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: A well-known problem with FM-CW radar systems is the leakage of transmitter power into the receiver which leads to the making of close-in targets, and can severely limit the system dynamic range performance. This thesis considers two solutions to this radar system problem for a low frequency radar operating in the VHF band. The first method to suppress coupling is using separate transmit and receive antennas designed in such a way as to reduce coupling between them. The second is to design a negative feedback loop as part of the radar receiver where the feedback loop adaptively reduces the amount of transmitter leakage through to the receiver. This project details the realisation of these two solutions. A number of antenna designs are modelled in software and simulated to determine their characteristics of which the transmit-to-receive coupling is the key parameter. As no low coupling configuration could be found a simple configuration is chosen and practical measurements are taken. These antennas are then used in the radar system that is to be built. An FM-CW radar system is designed and simulated using software with a negative feedback loop being designed and implemented into the radar simulation. A practical radar system is then made inclusive of the feedback loop. Measurements are then taken to determine the efficacy of the feedback loop. / AFRIKAANSE OPSOMMING: ʼn Bekende probleem met FM-CW radar stelsels is die lekkasie van versender krag tot in die ontvanger wat lei tot die maak van nabye teikens en kan die stelsel se dinamiese sendbereik steng beperk. Hierdie tesis oorweeg twee oplossings tot hierdie probleem vir ʼn lae frekwensie radar wat in die VHF band werk. Die eerste metode wat na gekyk word om die koppeling te onderdruk is om die twee antennas van die radar stelsel so te ontwerp sodat die hoeveelheid koppeling tussen hulle verminder is. Die tweede is om ʼn negatiewe terugvoerlus as deel van die ontvanger te ontwerp. Hierdie terugvoerlus sal die versender lekkasie sein aanpassend in die ontvanger verminder. In hierdie projek word die realisering van bogenoemde oplossings uiteengeset. ʼn Paar verskillende antenna ontwerpe word gemodelleer in sagteware en word gesimuleer om hul karakteristieke te bepaal. Die belangrikste van hierdie faktore is die versender na ontvanger koppeling. Sienend dat geen ontwerp met ʼn lae genoeg koppeling gevind kon word nie, is ʼn eenvoudige ontwerp gekies en praktiese metings daarvan geneem. Hierdie antennas word dan gebruik in die radar stelsel wat gebou sal word. ʼn FM-CW radar stelsel word ontwerp en gesimuleer in sagteware. Die negatiewe terugvoerlus word ook ontwerp en geïmplementeer in die radar simulasie. ʼn Praktiese radar stelsel word dan gemaak insluitend die terugvoerlus. Metings word dan geneem om die effektiwiteit daarvan te bepaal.

Le but de ce travail est de quantifier le potentiel et les capacités de la technologie térahertz à contrôler des colis afin de détecter les menaces telles que les armes et les explosifs, sans avoir besoin d'ouvrir le colis.Dans cette étude, nous présentons la spectroscopie térahertz résolue en temps et l'imagerie multi-spectrale pour la détection des explosifs. Deux types d’explosifs, ainsi que leurs mélanges binaires sont analysés. En raison de la complexité de l'extraction des informations face à tels échantillons, trois outils de chimiométrie sont utilisés: l’analyse en composantes principales (ACP), l'analyse des moindres carrés partiels (PLS) et l'analyse des moindres carrés partiels discriminante (PLS-DA). Les méthodes sont appliquées sur des données spectrales térahertz et sur des images spectrales pour : (i) décrire un ensemble de données inconnues et identifier des similitudes entre les échantillons par l'ACP ; (ii) créer des classes, ensuite classer les échantillons inconnus par PLS-DA ; (iii) créer un modèle capable de prédire les concentrations d’un explosif, à l'état pur ou dans des mélanges, par PLS.Dans la deuxième partie de ce travail, nous présentons l'imagerie par les ondes millimétriques pour la détection d'armes dans les colis. Trois techniques d'imagerie différentes sont étudiées : l'imagerie passive, l’imagerie active par des ondes continues (CW) et l’imagerie active par modulation de fréquence (FMCW). Les performances, les avantages et les limitations de chacune de ces techniques, pour l’inspection de colis, sont présentés. En outre, la technique de reconstruction tomographique est appliquée à chacune de ces trois techniques, pour visualiser en 3D et inspecter les colis en volume. Dans cet ordre, un algorithme de tomographie spécial est développé en prenant en considération la propagation gaussienne de l'onde. / The aim of this work is to demonstrate the potential and capabilities of terahertz technology for parcels screening and inspection to detect threats such as weapons and explosives, without the need to open the parcel.In this study, we first present terahertz time-domain spectroscopy and spectral imaging for explosives detection. Two types of explosives as well as their binary mixture is analyzed. Due to the complexity of extracting information when facing such mixtures of samples, three chemometric tools are used: principal component analysis (PCA), partial least square analysis (PLS) and partial least squares-discriminant analysis (PLS-DA). The analyses are applied to terahertz spectral data and to spectral-images in order to: (i) describe a set of unknown data and identify similarities between samples by PCA; (ii) create a classification model and predict the belonging of unknown samples to each of the classes, by PLS-DA; (iii) create a model able to quantify and predict the explosive concentrations in a pure state or in mixtures, by PLS.The second part of this work focuses on millimeter wave imaging for weapon detection in parcels. Three different imaging techniques are studied: passive imaging, continuous wave (CW) active imaging and frequency modulated continuous wave (FMCW) active imaging. The performances, the advantages and the limitations of each of the three techniques, for parcel inspection, are exhibited. Moreover, computed tomography is applied to each of the three techniques to visualize data in 3D and inspect parcels in volume. Thus, a special tomography algorithm is developed by taking in consideration the Gaussian propagation of the wave.

In this thesis, methods for radar-based environment perception from the vehicle safety point of view are presented. The proposed methods comprise advanced topics of radar-based target detection and tracking in dynamic pre-crash scenarios, as well as ghost object identification. The problem of a wandering dominant scatter point on the target surface and corresponding challenge for accurate target tracking in low-range configurations is considered. The proposed method presents a procedure to estimate target wheel positions and corresponding bulk velocities to serve as fixed scatter points on the target surface. Input to this method are raw radar data. The technique spatially resolves the micro-Doppler signals, generated by the rotating wheels of the target vehicle, to determine characteristic scatter points on the target surface. A micro-Doppler parameter is defined to quantify detections that are with high probability generated by the rotating target wheels. This group of detections is processed to estimate the wheel position and corresponding bulk velocities of the target, referred to as wheel hypotheses. The proposed method is evaluated in dynamic driving scenarios, where the driver performs an emergency evading action to avoid a collision. Subsequently, the detected wheel hypotheses serve as input to a developed tracking framework, which is used to estimate the target object static and dynamic states. Since the number of detected wheel hypotheses varies, a random-finite-set-based measurement model is used to incorporate multiple wheel hypotheses detected for one extended target object. The tracking performance is evaluated in critical evading scenarios using real vehicles as the target object. In addition, the thesis emphasized the problem of ghost object generation due to multipath propagation in pre-crash scenarios. Radar sensors, perceiving the immediate vehicle environment, show an elevated ghost object presence due to a higher probability illuminating potential reflection surfaces, e.g., road boundaries or buildings. At times, these ghost objects appear to be on a collision trajectory with the ego vehicle, whereas the vehicles are in uncritical driving scenarios, e.g., an urban intersection. In real-world driving scenarios, one target object may generate multiple false-positive targets. Based on the propagation and reflection behavior of electromagnetic waves, a geometric multipath model is derived, illustrating the occurring multipath reflections on real-world surfaces, e.g., buildings or road-bounding barriers. The proposed geometric propagation model describes the relative positions of the false-positive reflections and is validated with extensive real radar data. A custom reflector target mounted on a platform, creating deterministic point targets as dominant backscatter centers of a vehicle body, validated the different multipath reflections and the overall accuracy of the model. Moreover, radar measurements of a vehicle during an intersection scenario proved relevance to multipath reflection behavior and confirmed the model assumptions. Third, the relevance of skid scenarios with high magnitudes of side slip angles in pre-crash phases is highlighted. A novel test methodology, to non-destructively transfer vehicles with mounted surround sensors in skid situations, is developed and a survey analyzing a state-of-the-art radar sensor revealed the potential to improve object tracking performance. A test vehicle, equipped with a state-of-the-art automotive radar sensor and a reference sensor, was tested in real skid situations using a kick plate and a standardized radar target. The test method utilizes the side slip angle as a criticality criterion, which may be adjusted by the kick plate. Subsequently, a novel, modified motion model is derived, estimating side slip angles in these skid driving situations. The contribution emphasizes the estimation of horizontal vehicle motion using the proposed model considering an additional lateral force applied to the vehicle rear axle. Based on these results, an Extended-Kalman filter is designed to estimate the target object relative position and velocity in skid scenarios. The evaluation includes both the tracking and side slip angle estimations in real car tests using the above-mentioned test method.