Determine 24 GHz and 77 GHz Radar Characteristics for Surrogate Grass 2019-01-1012

Road departure mitigation (RDM) system is a new vehicle active safety feature. It may not rely only on lane marking for road edge detection. Standard Testing of RDM on road with real grass road edge has consistency issue, since the grass color may be different at different test sites and in different seasons. A solution is to develop surrogate grass that have the same characteristics of the representative real grass. Radar is one of the sensor used in RDM to identify road edge. This paper focuses on determining the 24GHz and 77GHz radar characteristic specifications of surrogate grass. This knowledge is essential for making surrogate grass for standard RDM testing, as the surrogate should have representative radar characteristics of the real grass. Since large area of grass can be measured, RCS (Radar Cross Section) can be used as the radar characterization of grass. A software defined 24GHz radar and additional 77GHz up-convertor were used to measure the 24GHz and 77GHz RCS. Various real grass samples of different height and color were measured in various depression angles. The measurement consists of measuring the grass and a corner reflector at the same angle and distances. Then the representative RCS of real grass is calculated. The interpretation of the measurement results for generating the radar characteristics requirement of the surrogate grass is discussed. The equipment and method for 24GHz and 77GHz radar reflectivity measurement of the grass is described. Reflectance values of different grass samples are measured and the average RCS is calculated. The RCS is not affected by the height of the grass. The suggested specification of the surrogate grass is expressed as a curve with respect to the measuring distance. This paper describes the method of determining the 24GHz and 77GHz radar characteristics requirements of surrogate grass, ranging from sampling, measurement equipment, measurement method, and interpretation of the data. This is the first step towards making consistent surrogate grass, which is essential for safely testing the RDM at all levels of driving automation.