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Immer komplexere und leistungsfähigere Fahrerassistenzsysteme in Fahrzeugen sind auf eine möglichst genaue Erfassung der Umgebung angewiesen. Eine wichtige Sensorklasse stellen dabei die Radarsensoren dar, da diese durch den Dopplereffekt direkt die radiale Geschwindigkeit von Zielobjekten erfassen können. Zukünftige Radare müssen über eine immer bessere Auflösung für die Bestimmung der Entfernungen, der Geschwindigkeiten und der Winkel, unter der Ziele erfasst werden, verfügen. Dies ermöglicht eine Klassifikation von Zielobjekten, beispielsweise die Unterscheidung zwischen Fußgängern und Fahrzeugen. Diese Arbeit stellt optimierte Ansätze der Signalverarbeitung vor, um unter anderem die Geschwindigkeitsauflösung durch eine geschickte Messauswertung zu verbessern, ohne die Messdauer zu verlängern. Weiterhin werden zwei Verfahren betrachtet und verglichen, die den Eindeutigkeitsbereich der Geschwindigkeit bei der Verwendung mehrerer Sendeantennen vergrößern. Eine verbesserte Winkelauflösung wird durch eine gezielte Unterabtastung und anschließende Rekonstruktion erreicht, sodass in der gleichen Entfernung und Geschwindigkeit unterschiedlich starke Ziele getrennt werden können. Zum Schluss werden zwei verschiedene Ansätze zur Unterabtastung in allen Messdimensionen und der anschließenden Rekonstruktion verglichen.

Have you read everything about direction-of-arrival estimation in textbooks but are you still uncertain how to realize it in practice? This tutorial-like paper will help to link the theory with a practical approach for direction-of-arrival estimation using mm-wave radar systems and it deals with arising challenges. Step by step, it is explained how to move from the measured time domain data to the estimated angular position of the target. Since the target angle estimation is usually carried out after range-velocity processing, the required pre-processing steps are described. The assessment criteria to form the relationship between array design and radar performance are expressed with the Rayleigh criterion for angular resolution and the ambiguity function as a measure for the unambiguous angular range. An in-depth instruction on how to carry out the sensor calibration is provided. Besides the choice of a proper calibration object, the required number of measurements and signal-to-noise ratio related issues are considered and supported by measurement results. The discussion of single- and multi-target measurements with the calibrated sensor concludes this work., acceptedVersion

In a number of applications millimeter-wave multiple-input multiple-output (MIMO) radars are widely employed. The use of conformal antenna arrays has been recently proposed to improve the radar sensor performance. This paper presents an optimization algorithm for finding the antenna placement in a non-planar arrangement. The experimental characterization of two prototypes based on radar measurements with an experimental 3 �� 8 MIMO radar sensor confirms the results predicted by the numerical simulations. The direction of arrival estimation has been performed successfully, and the measured beampatterns are in very good agreement with the simulated ones., acceptedVersion

In an automotive environment the presence of reflecting surfaces cannot be avoided. The electromagnetic wave returning from a target vehicle can get reflected on those surfaces causing a non existing so-called ghost target. For driver assistance systems ghost targets can lead to false decisions and, therefore, they should be detected and avoided. In this paper a model for describing those ghost targets and a procedure to distinguish them from real targets using the orientation and the motion state of a vehicle is presented., acceptedVersion

Radar sensors offer enormous advantages as sensing devices for automated and autonomous driving. However, when multiple of such sensors are operated in a large number of cars, there is a high risk of the occurrence of mutual interference. In the currently widespread linearly frequency modulated sensors interference reduces the detection performance, especially for targets with a low radar cross section. In this paper the interference effects are suppressed with an adaptive beamforming scheme based on a mean square error minimization. The paper evaluates the algorithm with the help of a simulated and measured scenario, and discusses the occurring interference effects and the benefits of the beamforming approach., acceptedVersion