Study On The Improved Antipodal Vivaldi Antennas

As one of the key techniques in ultra-wideband wireless communication, the ultra- wideband antennas have gradually attracted the attention of people. Antipodal vivaldi antenna proposed in this paper is a tapered slot, end-fire, travelling-wave antenna. It has some good performances such as wide band, directional radiation and fixed center of phase. What is more, it is simple in structure and can be easyly fabricated, fed, integrated. It's quite fit for ultra-wideband wireless communication. The aim of this paper is to design a high gain ultra-wideband antipodal vivaldi antenna, which is small in size, low in profile.Firstly, a typical antipodal vivaldi antenna is designed, named antennaⅠ. AntennaⅠVSWR is below 2.5 across the frequency band form 1GHz to 9GHz. Its gain is above 5 dB across the main frequency band. But its size is large. In order to reduce antennaⅠsize and profile, a wide-ended antipodal vivaldi antenna is designed, named antennaⅡ. Compared with antennaⅠ, antennaⅡhas wider bandwidth and lower profile. But its gain is low.Secondly, a antipodal vivaldi antenna with a metal director is designed in order to improve the antennaⅡgain., named antenna III. With respect to antennaⅡ, antenna III has not only higher gain but also wider radiation pattern bandwidth via restraining the E-plane radiation pattern split at the high frequency band.Thirdly, a comb antipodal vivaldi antenna, named antennaⅣ, is also designed based on antennaⅡ. Its gain is improved by 1.5dB across the frequency band form 1.8GHz to 3.5GHz compared with antennaⅡ. But, antennaⅣgain appears fluctuation across the frequency band form 3.5GHz to 7GHz and changes greatly.Finally, a comb antipodal vivaldi antenna with a metal director is proposed in this paper based on antenna III and antennaⅣ, named antennaⅤ. Its gain is improved by 1.3dB across the frequency bands form 1.8GHz to 3GHz and form 6GHz to 10GHz. AntennaⅤwidth is 0.36λ0 , height is 0.32λ0 (λ0 is the wavelength of 0.8GHz in the free space). Its gain is above 5 dB across the main frequency band. Therefore, antennaⅤhas compact size , low profile , wide bandwidth and high gain. AntennaⅤmeets this paper design requirements.