Automotive Radar in W-band Utilizing Wide Angle Phased Array
Abstract
Automotive radars have been on the market since their introduction in adaptive cruise control. More and more safety applications employing automotive radars are being released but most of them have a narrow field of view. In this thesis methods for obtaining a 180◦ field of view in front of the car by the use of phased array systems are studied. Linear array antennas being used today have a limited scan angle and therefore a narrow field of view. In addition the angular resolution of most systems is poor and range/velocity/angle ambiguities are serious problems. In order to obtain a wide field of view we have employed conformal array designs. For a scenario where the radar carrying vehicle is stationary the 1D monopulse and Root-MUSIC methods have been studied as methods for measuring the target angles. The ambiguities have been avoided by first detecting the targets in the range/velocity domain and then using only the data from the corresponding target frequencies in order to find the target angles.
The second part of the thesis concerns a scenario where the radar carrying vehicle is moving towards an intersection. In order to suppress the clutter 2D methods are employed for the target detection and feature extraction problem by rewriting the problem as a 2D spectral estimation problem. The performance of several estimators is evaluated for the problem and the 2D APES method, combining high resolution with reasonable complexity, is found to be the best choice among the methods tested. This solution yields very high resolution in both the range/velocity and the angular domain within a very short measurement time. The high resolution is exploited to obtain more robust tracking and faster initialisation of the tracking filter by incorporating multiple resolved reflection points from a single vehicle in the same tracking model. Increased tracking robustness and short initialisation time is a key feature for future safety critical automotive radar applications.