The Effect of Raindrops on the Automotive On-Glass Antenna

In this paper, we evaluate the effect of raindrops on the on-glass antennas in order to make the design more efficient. Automotive glass has a three-layer structure with an interlayer film in between to prevent shattering. A dipole antenna was placed on the lower center surface of a 300 mm $\times300$ mm glass sheet, and the electromagnetic field analysis was conducted using a model in which raindrops adhered to the antenna. The results show that raindrops have little effect on the reflection coefficient of the antenna. However, if the raindrops flow in the same direction as the antenna and form streaks, the reflection coefficient worsens. Both raindrops and rain streaks were found to affect the radiation pattern.