scan (serially alternating) enables detections in far and short range (Fig. 4.4b and 4.5a). Switching between near and far range scan is performed via selecting different chirps. The system is further equipped with several antennas for simultaneous detection of multiple objects. A classification of moving objects as vehicles, bicycles or pedestrians is also possible.
Fig. 4.4: ARS 408-21 radar sensor. (a) Picture of the ARS 408-21 radar sensor. [35] (b) A digital antenna offers two independent scans for far and short range. The sensor contains 2 TX and 6 RX antennas for near range and 2 TX and 6 RX antennas for far range scan using digital formed beams. [35]
The sensor can be connected to as well as configured via a CAN (Controller Area Network) which performs the communication between the sensor and a computer. The sensor’s working principle is based on fast chirp FMCW modulations and thus on independent distance and velocity measurements of targets in one cycle (see section 2.1.4). The target information is evaluated during every cycle and its position is given in a coordinate system relative to the sensor. The velocity is estimated relative to an assumed vehicle course, which is determined by using the speed and yaw rate information (if the sensor is mounted in the longitudinal direction on the front of the car (Fig. 4.5b)). The measured objects can be filtered by different criteria and thus only reflections of objects of interest are sent to the CAN-bus. A detailed description of the sensor is given in [36].
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Chris Händel • Heikki Konttaniemi • Matti Autioniemi