Principles of automotive radar systems

Abstract

A radar system radiates electromagnetic energy into space from an antenna or an antenna array. The radiated electromagnetic energy "illuminates" the surrounding targets. The "illuminated" targets intercept some of the radiated energy and reflect a portion back to the radar system. The radar system utilizes one or multiple receiver channels to detect the reflected energy to determine the targets' range, velocity, and relative angles.Based on the different types of waveforms radiated by the radar transmitter, radar systems can be categorized as pulsed radars and continuous-wave (CW) radars. A pulsed radar consists of a repetitive train of short-duration pulses. The range of the target is measured based on the time delay between the transmitted pulse and the received pulse. Different from a pulsed radar, a CW radar usually transmits the electromagnetic wave continuously in a period of time. The properties of the targets are obtained by comparing between the received signal with a replica of the transmitted signal. For automotive applications, CW radar systems have been the dominant due to their advantages in multiple aspects. Compared with a pulsed radar, a CW radar features low peak transmit power, simpler, and highly integrated structure, which make its applications spread into various areas, especially for automotive applications. This chapter is trying to present a thorough and consistent description of the fundamentals of radar technology for automotive applications. Though many of the concepts are the same between pulsed radars and CW radars, CW radars are emphasized over pulsed radars in this book.