An Improved Vivaldi Antenna for Vehicular Wireless Communication Systems

In order to improve the directivity of the antenna used in vehicular IEEE 802.11a (4900 similar to 5935 MHz) wireless local area networks (WLAN), and make the antenna be more likely installed in the same shark-fin-like radome that can be applied in various antennas of different vehicular wireless communication systems, an improved Vivaldi antenna with planar directors in front of the aperture of the tapered slot and transverse slots is proposed and fabricated. These measured and simulated results show that the improved Vivaldi antenna increases by 1.5 dB of gain compared to that of the normal one on average in IEEE 802.11a (5150 similar to 5935 MHz) WLAN. It also has high directivity in IEEE 802.11b (2400 similar to 2483 MHz) WLAN, IEEE 802.11y (3560 similar to 3700 MHz) WLAN, or other wireless communication systems (2400-4900 MHz). Moreover, the improved Vivaldi antenna can enhance the ability to resist the polarization distortion caused by the car roof, which acts as a big ground plane compared to the conventional one.