TY - JOUR
T1 - A problem of infrared electronic-toll-collection systems
T2 - The irregularity of LED radiation pattern and emitter design
AU - Shieh, Wern Yarng
AU - Hsu, Chen Chien James
AU - Wang, Ti Ho
N1 - Funding Information:
Manuscript received December 30, 2008; revised January 26, 2010, May 13, 2010 and July 16, 2010; accepted August 19, 2010. Date of publication September 20, 2010; date of current version March 3, 2011. This work was supported by the National Science Council, Taiwan, under Contract NSC-97-2221-E-129-001 and Contract NSC-98-2221-E-129-001. The Associate Editor for this paper was L. Li.
PY - 2011/3
Y1 - 2011/3
N2 - According to our measurements, the radiation pattern of many low-cost commercial light-emitting diodes (LEDs) is not smooth. Some LEDs even have serious irregularities that affect the performance of infrared communication systems. For systems where a definite communication area is required, such as electronic-toll-collection (ETC) applications, this problem is particularly serious. In this paper, we first present our measured results for the radiation pattern of several typical low-cost commercial LEDs, showing that almost all of them are irregular to some extent. We then use the most acceptable model with a suitable half-intensity angle to construct the emitter of an ETC system. The design was calculated with the aid of an optimization algorithm to determine the mounting angle for each LED such that the system has an extended communication area in the longitudinal direction, i.e., in the vehicle traveling direction, and can withstand high signal attenuation. For a typical LED with half-intensity angle Φ1/2 = 13°, a very simple two-group structure for the emitter is obtained, and the analysis results are verified by experimental measurements.
AB - According to our measurements, the radiation pattern of many low-cost commercial light-emitting diodes (LEDs) is not smooth. Some LEDs even have serious irregularities that affect the performance of infrared communication systems. For systems where a definite communication area is required, such as electronic-toll-collection (ETC) applications, this problem is particularly serious. In this paper, we first present our measured results for the radiation pattern of several typical low-cost commercial LEDs, showing that almost all of them are irregular to some extent. We then use the most acceptable model with a suitable half-intensity angle to construct the emitter of an ETC system. The design was calculated with the aid of an optimization algorithm to determine the mounting angle for each LED such that the system has an extended communication area in the longitudinal direction, i.e., in the vehicle traveling direction, and can withstand high signal attenuation. For a typical LED with half-intensity angle Φ1/2 = 13°, a very simple two-group structure for the emitter is obtained, and the analysis results are verified by experimental measurements.
KW - Dedicated short-range communication (DSRC)
KW - electronic toll collection (ETC)
KW - infrared communication
KW - intelligent transportation system (ITS)
KW - light-emitting diode (LED)
KW - radiation pattern
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U2 - 10.1109/TITS.2010.2071384
DO - 10.1109/TITS.2010.2071384
M3 - Article
AN - SCOPUS:79952070059
SN - 1524-9050
VL - 12
SP - 152
EP - 163
JO - IEEE Transactions on Intelligent Transportation Systems
JF - IEEE Transactions on Intelligent Transportation Systems
IS - 1
M1 - 5580074
ER -