Electronic Toll Collection(ETC) system is a kind of modem traffic toll collection means based on RFID technology[ 1]. By using the microwave dedicated short range communication (DSRC) operating at 5.8GHz between the tag or so-called on board unit(OBU), which are installed on the front window of vehicles and the reader or road side unit(RSU) on the ETC road of toll collection station, the passing vehicles' toll could be collected automatically without stopping. The time spent on each vehicle is less than two second and the ability for vehicles' passing of ETC passage is five to ten times of manual toll collection passage. For these reasons, ETC system has been developed and spread rapidly in recent years at home and abroad.
On March 2007, the national specifications of China on ETC&DSRC, GB/T20851-2007[2], had been published. Some needs on the reader's antenna have been defined in it. According to the specifications, the microstrip antenna array is the leading choice for the RSU because of its low cost, low profile and ease of fabrication[3] as well as the gain of the array is easy to meet the demands.
In this paper, the design indices about the reader's antenna are listed and discussed, then a microstrip array antenna resonating at 5.8GHz and providing a peak gain of about 15dBi at center frequency is developed. It radiates a righthand circular polarization beam with half-power lobe-width 18° in the horizon plane and 34° in the vertical plane. And the lOdB return 10ss(RL) impedance bandwidth and 3dB axial ratio bandwidth of the antenna is greater than 200MHz.
II. DESIGN INDICES AND METHOD
A. Design Indices In accordance to the national specifications, the same righthand circular polarization(RHCP) antenna is used in the RSU for either transmitting or receiving signal. Some concerned parameters of the antenna are listed in Table
Electronic Toll Collection(ETC) system is a kind of modem traffic toll collection means based on RFID technology[ 1]. By using the microwave dedicated short range communication (DSRC) operating at 5.8GHz between the tag or so-called on board unit(OBU), which are installed on the front window of vehicles and the reader or road side unit(RSU) on the ETC road of toll collection station, the passing vehicles' toll could be collected automatically without stopping. The time spent on each vehicle is less than two second and the ability for vehicles' passing of ETC passage is five to ten times of manual toll collection passage. For these reasons, ETC system has been developed and spread rapidly in recent years at home and abroad. On March 2007, the national specifications of China on ETC&DSRC, GB/T20851-2007[2], had been published. Some needs on the reader's antenna have been defined in it. According to the specifications, the microstrip antenna array is the leading choice for the RSU because of its low cost, low profile and ease of fabrication[3] as well as the gain of the array is easy to meet the demands. In this paper, the design indices about the reader's antenna are listed and discussed, then a microstrip array antenna resonating at 5.8GHz and providing a peak gain of about 15dBi at center frequency is developed. It radiates a righthand circular polarization beam with half-power lobe-width 18° in the horizon plane and 34° in the vertical plane. And the lOdB return 10ss(RL) impedance bandwidth and 3dB axial ratio bandwidth of the antenna is greater than 200MHz. II. DESIGN INDICES AND METHOD A. Design Indices In accordance to the national specifications, the same righthand circular polarization(RHCP) antenna is used in the RSU for either transmitting or receiving signal. Some concerned parameters of the antenna are listed in Table
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