  Automotive radar sensors play a key role in the current development of
autonomous driving. Their ability to detect objects even under adverse
conditions makes them indispensable for environment-sensing tasks in autonomous
vehicles. The thorough and in-place validation of radar sensors demands for an
integrative test system. Radar Target Simulators (RTS) are capable of
performing over-the-air validation tests by creating artificial radar echos
that are perceived as targets by the radar under test (RuT). Since the
authenticity and credibility of these targets is based on the accuracy with
which they are generated, their simulated position must be arbitrarily
adjustable. In this paper, a new approach to synthesize virtual radar targets
at an arbitrary angle of arrival is presented. The concept is based on the
superposition of the returning signals of two adjacent RTS channels. A
theoretical model describing the basic principle and its constraints is
developed. A measurement campaign is conducted that verifies the practical
functionality of the proposed scheme.
