A stacked rectangular microstrip antenna with a shorting plate combined with a rectangular ring microstrip antenna is proposed for triple band operation (GPS, VICS and ETC) in ITS. The two microstrip antennas are excited by an L-probe feed. In the ETC band, axial ratio deteriorates due to asymmetrical distributions of the electric current in the ring microstrip antenna. In this paper, an approach to improve the axial ratio for ETC is also proposed. The proposed antenna has the proper radiation patterns and impedance matching for the GPS, VICS and ETC.
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