Study of the Bumper Thickness and its Placement for Automotive Radar Applications

This paper studies the theory of interference of reflected light to provide the equation for the optimum thickness of the bumper and the optimum distance between the radar and the bumper. The simulations are carried out at 77 GHz using a two-element microstrip array antenna which is placed behind the bumper made of materials Polycarbonate and Acrylonitrile-Butadiene-Styrene. Bidirectional losses and bandwidth are measured at normal incidence. The results for optimum separation between the radar antenna and the bumper have also been verified using a one-element array microstrip antenna operating at 24 GHz with a FR4 material bumper. It has been observed that for a small variation in thickness and separation between bumper and antenna, the losses change drastically. Losses increase sinusoidally with increase in the thickness and separation, but with the right selection of bumper thickness and separation from the antenna, the losses can be minimized.