A millimetric car radar front end for automotive cruise control

An active cruise control (ACC) system must be cheap, small, robust and reliable if it is to be adopted by vehicle manufacturers. Since the system also has to operate within the European and the USA allocated millimetric frequency band, 76-77 GHz, these requirements have provided significant challenges to microwave systems engineers. As a result, until fairly recently, ACC has remained an interesting research and development project. However with the growth and implementation of new technologies, a number of practical systems are now becoming commercially viable. This paper describes both the technical and commercial requirements of a practical system and discusses the front-end integration of the microwave transmit/receive (TX/RX) unit and electronics. Particular attention is paid to the performance and cost requirements of key components, particularly the 77 GHz oscillator. The discussion comments upon whether recent advances in gallium arsenide (GaAs) millimetric MMICs (high electron mobility transistor (HEMT) and heterojunction bipolar transistor (HJBT)) have the potential of meeting the oscillator performance and offering a reduction in cost when compared with the more established technologies