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In order to simulate realistic traffic scenarios, a radar target simulator must be able to generate multiple radar targets with different directions of arrival. The presented concept is able to generate an arbitrary amount of targets with individual directions of arrival for the radar under test. By measuring the radar channel, the novel approach enables target simulators to simulate arbitrary directions of arrival, while minimizing the required hardware. The optimum setup is derived for radars with a uniform linear receive antenna array. The compensation of placement errors for automotive chirp-sequence frequency modulated continuous wave radars is demonstrated. Finally, the calibration for the setup is provided, and the performance of the presented approach is validated.INDEX TERMS Automotive radar, chirp-sequence modulation, direction of arrival, FMCW radar, radar target simulator.This article has been accepted for inclusion in a future issue of this journal. Content is final as presented, with the exception of pagination.

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For the development of fully-autonomously driving vehicles, advanced capabilities for sensor systems are required. With modulation-based radar target simulators, complex traffic scenarios can be simulated for automotive radars at low costs. Yet the simulation principle relies on the timings of the chirp-sequence frequency modulated continous waveform. Since small timing variations can be purposely introduced on the radar's waveform e.g. for interference mitigation techniques, the assumption of ideal timings could be violated. Therefore, this paper investigates the influences of ramp timing deviations on the target simulation. A signal model for radar timing variations for modulation-based simulators is presented. Furthermore, the influence of ramp timings on the resulting signal-to-noise ratio of simulated target responses is derived and verified by measurements.

Radar sensor networks are today widely used in the field of autonomous driving and for generating high-precision images of the environment. The accuracy of the environmental representation depends to a large extent on the accurate knowledge of the sensor's mounting orientation. Both the relative orientation of the sensors to each other and the relative sensor orientation in relation to the vehicle coordinate system are determining factors. For the first time, the orientation estimation of the radar sensors of a network is possible exclusively on the basis of radar target lists without additional localization and orientation devices such as an IMU or GNSS. In this work, two algorithms for determining the orientation of incoherently networked radar sensors with respect to the vehicle coordinate system and with respect to each other are derived and characterized. With the presented algorithms orientation accuracies up to 0.25 • are achieved. Furthermore, the algorithms do not impose any requirements on the positioning or the orientation of the radar sensors, such as overlapping field of views (FOVs) or the detection of identical targets. The presented algorithms are applicable to arbitrary driving trajectories as well as for point targets and extended targets which enables the use in regular road traffic.