White Paper: Sensors/Data Acquisition
Automotive Radar Sensors – Transmit Signal Analysis and Inference Tests
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Road safety is a global challenge at present and will be in the future. Automotive radar has become a keyword in this area and pushes again a step forward to increase driving comfort, crash prevention and even automated driving.
Driver assistance systems which are supported by radar are already common. Most assistant systems are increasing the drivers comfort by collision warning systems, blind-spot monitoring, adaptive cruise control, lane-change assistance, rear cross-traffic alerts and back-up parking assistance.
Today's 24 GHz, 77 GHz and 79 GHz radar sensors clearly need the capability to distinguish between different objects and offer high range resolution. That is possible with increased signal bandwidth. Also these radar systems need to cope with interference of many kinds like the one from other cars radars.
This Application Note highlights signal measurements and analysis of automotive radars that are crucial during the development and verification stages. Particular emphasis is placed on a setup to verify the functionality of a radar in case of radio interference.
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Overview
The application note on Automotive Radar Sensors by Rohde & Schwarz addresses the critical role of radar technology in enhancing road safety and driving comfort through advanced driver assistance systems (ADAS). It emphasizes the necessity for high performance, reliability, and cost-effectiveness in automotive radar sensors, which are increasingly used in vehicles—often exceeding ten sensors per car.
The document outlines the principles of Continuous Wave (CW) radar, detailing the various waveforms employed in automotive applications, such as Multi-Frequency-Shift Keying (MFSK) for blind spot detection and Linear Frequency Modulated Continuous Wave (LFMCW) signals for adaptive cruise control. It highlights the importance of signal power and the potential for interference among multiple radar systems operating in the same frequency bands, particularly in the 24 GHz and 77-81 GHz ranges.
A significant concern addressed is the phenomenon of ghost targets, which are false signals generated by interference from other radar systems or noise, potentially leading to malfunctions in automotive sensors. The document stresses the need for rigorous testing and measurement setups to evaluate radar performance under various interference conditions, ensuring that automotive radars can reliably distinguish between real and ghost targets.
The application note also discusses measurement setups for signal analysis, including the generation of interference signals and the evaluation of radar performance in the presence of these signals. It provides insights into the methodologies for testing mutual interference, particularly with Chirp Sequence (CS) waveforms, which require higher sampling rates and filter bandwidths due to their rapid chirp rates.
In summary, this application note serves as a comprehensive guide for understanding the complexities of automotive radar systems, the challenges posed by interference, and the necessary testing methodologies to ensure their reliable operation in real-world scenarios.