Continuous waveforms for automotive radar systems
Driving a car seems to be a safe action. However, there are about 5,000 fatalities on German streets every year, which is absolutely too much. All drivers have strong limitations when measuring the distance and the relative velocity of other cars, especially under bad weather conditions which are the reason for several accidents. Therefore, some technical assistance is highly welcome to every driver. The European Union has called all car manufacturers to intensify their research activities in protecting vulnerable road users and increasing the traffic safety. An automotive radar sensor in the 24 GHz frequency domain measures target range, radial velocity and azimuth angle simultaneously with high accuracy and resolution even in multitarget situations. The all-weather capability is an important additional feature of all radar systems. Therefore, this chapter considers automotive radar sensors as a basis for reliable driver assistant systems. The technical challenge is the simultaneous measurement of target range, radial velocity and azimuth angle. This task has a direct and strong relevance to the waveform design process. Therefore, the objective of this chapter is the waveform design for continuous wave radar systems. Several transmit signals are considered in detail and different proposals are discussed and compared, especially for automotive applications. Usually, the lateral velocity component cannot be measured by a radar sensor and a single measurement. This task can be of high importance in typical city traffic situations where the track direction of a car needs to be known in a very short time frame. A signal processing scheme will be shown in this chapter which indeed allows the additional measurement of the lateral velocity component based on a single observation.
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