Infrared communication in the wavelength band of 780-950 nm is very suitable for short-range point-to-point data transmission. It is a good choice for vehicle-to-vehicle communication in several intelligent transportation system (ITS) applications, such as pileup-crash prevention, vehicle platooning (cooperative driving), and collision warning. For these applications, the coming direction, i.e., the direction of arrival, of the signal can help filter out unnecessary information so that necessitated actions of the system can be performed more effectively and correctly. For the aforementioned applications, 1-D signal-direction discrimination is sufficient. The signal direction can be determined by amplitude comparison utilizing two planar receiving modules, each with a tilt angle relative to the central direction of the receiver. The basic theory of obtaining the direction of infrared signal is reviewed in this paper as a basis to construct two signal-direction discriminators with a different tilt angle of their receiving modules. The effect of the tilt angle is investigated. The experimental verification was performed in both laboratory and outdoor environments, showing that our measurements are in quite good agreement with real values in most cases. Our measurements also reveal two main reasons for inaccuracy: 1) nonideal receiving pattern of the individual receiving modules and 2) multipath scattering from other objects. Combining the infrared signal-direction discriminator with our previously designed emitter, we expect that valuable contributions can be made toward the aforementioned ITS applications.
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