Monopulse Doppler radar for vehicle applications

This paper describes an efficient, forward looking, radar system that can be used for vehicle applications including collision warning, collision avoidance and adaptive or intelligent cruise control. A Doppler radar system is described that uses a monopulse antenna scheme to track multiple targets and generate range, range rate and azimuth angle output data for each target. The system requires less than 2 MHz of bandwidth and can be designed to operate at any microwave or millimeter-wave frequency. The transmitted power is less than 2 milliwatts and the system can track targets to ranges in excess of 125 meters. The radar system uses frequency modulated continuous wave (FMCW) radar transmission with frequency shift keying (FSK) for range measurements to minimize bandwidth requirements. The advantages and disadvantages of a Doppler radar system with FSK modulation are presented. A block diagram of the radar system is included and the theory of operation is described in the text. The Doppler radar system described employs digital signal processing (DSP) and fast Fourier transforms (FFT) to identify, separate and track individual targets in the frequency domain. The system produces range, range rate and azimuth angle as independent data values even though they are mathematically related. The Doppler radar system described in this paper measures range, range rate and azimuth angle independently and simultaneously.