| The increasing demand for portable and small electronic equipment makes the fast development of electronic circuit integration technology,and the size of the each part of circuit in the system is reduced,and the antenna used in the terminal part of the system is also faced with the challenge of miniaturization,while the trade-off between performance and size is considered the focus of miniaturization of the antenna.The Vivaldi antenna,which belongs to the Ultra-wideband antenna,is a kind of Tapered slot antenna,which has the advantages of wide band,symmetrical pattern,stable gain and simple structure,low profile,easy integration and so on,and it has been widely used in radar system,indoor and outdoor communication system,measurement devices and other neighborhoods.The structure design of the Vivaldi antenna follows the principle of traveling wave,which cases the antenna's size is bound to be too large,so the study for the miniaturization of the antenna has been essentially from the traveling wave antenna into the resonant antenna.The main content of this paper is to study the Vivaldi antenna miniaturization,so then the main work of this paper include(1)Based on the equivalent circuit analysis of the micro-strip line-slot line coupled feeding structure,a folded micro-strip small feeding area Vivaldi antenna is designed.The feeding structure of the proposed antenna was obtained by using an open-circuited slot line and a folded feeding micro-strip line,which was short-circuited in the slot side,on the coupling area to reduce the reflection coefficient of the micro-strip line-slot line coupling and effectively reduce the feeding area.And the influence of the thickness of the dielectric substrate and the wide end width of the exponential tapered slot line is analyzed.Finally the antenna with the size of 60mm×53.1mm×0.4mm has a working band of 3-14 GHz and the maximum gain of 9.22 d Bi.(2)An impedance conversion micro-strip feeding Vivaldi antenna is designed.The feeding structure of the proposed antenna still is obtained by using the form of an open-circuited slot line and a short-circuited micro-strip line in the slot side,and the feeding micro-strip line is set to the impedance conversion structure.Then the influence of the thickness of the dielectric substrate and the wide end width of the exponential tapered slot line is also analyzed in the case where the width and length of the exponential tapered slot line are the same as the folded micro-strip small feeding area Vivaldi antenna.Finally the antenna with the size of 60mm×54mm×0.4mm has a working band of 2-18 GHz and the maximum gain of 9.97 d Bi.(3)Based on the equivalent circuit analysis of the micro-strip line-slot line coupled feeding structure with slot resistance loading,a slot resistance-loaded Vivaldi antenna is designed.The feeding structure of the proposed antenna is obtained by converting open-circuited slot line to slot resistance loading through the improvement of an open-circuited slot line and a short-circuited micro-strip line in the slot side to reduce the reflection coefficient of the micro-strip line-slot line coupling.Then the antenna with the size of 40mm×41mm×0.4mm has a working band of 2-25 GHz.Meanwhile,the slot line between the micro-strip line-slot line coupling and resistance is widened and the linear gradient quarter-wavelength slot in the metal area on both sides of the antenna,thereby the gain,radiation efficiency and pattern of the antenna have been significantly improved,and the gain can be up to 8.45 d Bi. |
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