Theoretical Study on Angular Resolution Improvement in FMCW Radar for Automotive Application

Abstract

This study is about the utilization of Frequency Modulated Continous Wave radar system for automotive application to detect the distance between the moving vehicle (in this case. Super Bus) and target(s) in order to avoid collision. A high resolution is required to maximize the system performance, especially the angular resolution, which is important for the vehicle s control unit to make the decision for breaking or steering. In order to produce a higher angular resolution, a -quantity of data obtained from some number (N) of radar position (due to the vehicle movements) are further processed and observed. This report describes several methods of processing the data: constant phase term processing and Synthetic Aperture Radar (SAR) concept processing. Two approaches of Synthetic Aperture Radar (SAR), Linear FMCW beamforming and Stepped Frequency FMCW beamforming, were investigated and compared by conducting several related simulations which are briefly described in this report. From the simulations, it was found that higher angular resolution can be obtained by increasing the number of measurements data, N. Another important finding is that the stepped frequency FMCW beamforming approach produces higher angular resolution compared to linear FMCW approach. However, the utilization of one radar sensor to detect one target results in ambiguity problems. The ambiguity problems found in the “one radar and one target” case can be reduced by utilizing two radar sensors (multistatic radar). To investigate the utifization and processing of multistatic radar, three possible beam processing (beam subtraction, beam addition, and beam multiplication) for two radar sensors were studied and compared by conducting several related simulations. From the simulations, it is found that beam addition and beam multiplication can solve the ambiguity problem in one plane, and that beam multiplication results in a better angular resolution. However, to solve the ambiguity problems in two plane (horizontal and vertical), three radar sensors will be required. The possibility to combine the phase processing method with the beam multiplication method to obtain a high angular resolution is also described in the report. From the study, it is concluded that the FMCW radar angular resolution can be significantly improved with several conditions and compromises.