The Study And Design Of Wideband And High-efficiency Slot Antenna

With the development of the wireless communication technologies,modern electronic equipment requires antennas to have increasingly better performance in size,operating bandwidth and directivity,et al.Slot antennas are widely ultilized in various platforms and have been one of the research hot topics for years for their merits of low profile and ease of realizing wide bandwidth.This paper focuses on how to further improve the impedance and radiation performance of a variety of slot antennas.The main novelty works obtained by the author are summarized as follows:1.Single-and dual-polarized antennas with high gains are studied based on the combination of slot antennas and Yagi-Uda antennas.The half-wavelength slot antennas are utilized to replace the electric dipoles for conventional Yagi-Uda antennas to improve the impedance match of Yagi-Uda antennas over a wide frequency band and enhance the directivity of traditional slot antennas.The designed linear-polarized slot Yagi-like antenna achieves a-10dB impedance bandwidth of 27.8%.The gains are over 8dBi across the operating frequency band.The designed dual-polarized slot Yagi-like antenna uses a crossed slot as the driven element to realize better port isolation.Meanwhile another crossed slot is utilized as the director element to significantly enhance the antenna directivity.The-10dB impedance bandwidth of the two ports can cover the whole WiMAX band.The gains and port isolations within the operating band are over 8.7dBi and 27dB,respectively.2.A broadband circularly polarized antenna with a compact structure is proposed based on a microstrip-CPW fed rectangular slot antenna.A rectangular slot antenna with four CPW feeding ports is firstly designed.The wideband feeding network consists of a Wilkinson power divider and two 90°phase difference comparators.The measured impedance bandwidth for|S₁₁|<-10dB is 74.4%.A broad 3-d B axial ratio?AR?bandwidth of 70.8%is also obtained.The measured 3-dB gain bandwidth is 53.65%with the peak gain of7.1dBic.3.A compact four-element MIMO antenna with high port isolations based on the half-mode substrate integrated waveguide?HMSIW?cavity-backed slot antenna is proposed.The mutual couplings between two elements are firstly investigated to provide guidance for the design of MIMO antennas.Low mutual coupling is obtained by utilizing the properties of SIW structures for little field leakage and surface wave suppression without any additional decoupling structure.The measured relative impedance bandwidth is 27.7%from 8.7GHz-11.5GHz for|S₁₁|<-10dB.And the mutual coupling is lower than-31dB across the operating band.4.An ultra-wideband?UWB?horizontally polarized?HP?omnidirectional antenna is designed.Firstly,the effect of the element numbers and array radius on the impedance bandwidth for a circular connected Vivaldi antenna array is investigated through a parametric study.The connected Vivaldi antenna array mechanism can be exploited to achieve ultra-wide impedance bandwidth.Meanwhile,good omnidirectional radiation patterns can be obtained due to circular element distribution.The designed antenna exhibits a relative impedance bandwidth of 159.97%?1.28-11.51GHz?for|S₁₁|<-10dB.Meanwhile,uniform omnidirectional radiation patterns with a gain variation of less than 1.5dB have been obtained within the frequency band of 1.25-7.6GHz?142.73%?.