Infrared light emitting diodes (LEDs) with a half-intensity angle Φ1/2≃ 10° are suitable for electronic-toll-collection (ETC) applications. However, the radiation patterns of commonly available low-cost commercial infrared LEDs are irregular to some extent, which result in difficulties to construct an infrared ETC system with a proper communication area. Most low-cost infrared LEDs with a half-intensity angle Φ1/2≃ 10° exhibit a common irregularity in their radiation pattern – a notch in the central radiant direction. The adverse influence bccause of such irregularities can be reduced by a proper design of an LED array in the emitter. High attenuation for the infrared signal of some windshields is also a serious problem for infrared ETC systems, which leads to severe shrinkage of the communication area if the emitter has not been properly designed. In this study, the authors present some successful designs with the aid of an optimisation algorithm to adjust the mounting angle of each constituent LED. In spite of the aforementioned irregularity, the proposed design still exhibits good performance in terms of the ability to withstand high signal attenuation and extended communication area in the vehicle-travelling direction.
Design of light-emitting-diode array for solving problems of irregular radiation pattern and signal attenuation for infrared electronic-toll-collection systems
IET Intelligent Transport Systems ; 9 , 2 ; 135-144
2015-03-01
10 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
light emitting diodes , irregular radiation pattern , optimisation algorithm , ETC mounting configuration , commercial infrared LED , mounting angle adjustment , bit error rate , error statistics , central radiant direction , ETC system , on-board unit , received signal strength , road side unit , signal attenuation , infrared detectors , emitter , intelligent transportation systems , LED notch compensation , cosine function , road pricing (tolls) , infrared electronic-toll-collection system , light emitting diode array design , vehicle travelling direction , optimisation , ETC requirements , half intensity angle adjustment
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