| The development of wireless communication technology has been revolutionary in this century,witch is life style-changing,along with a higher requirement of communication quality,speed,also portability of mobile devices.As the transceiving equipment of the entire system,antenna's performance is one of the determining factors to ensure the stability of the communication quality,consequently,antenna's exploration is essential.MIMO technology and UWB technology are key technology to improve the quality and speed of the communication system,the former can improve the channel capacity and channel fading can be inhibited with diversity technology,based on limited frequency;there are many advantages of latter one,such as,low-power consumption,high-fidelity,high frequency utilization.The defect of UWB technology will be overcome in combination with MIMO technology.In this dissertation,miniaturization of UWB-MIMO antennas with high isolation has been studied,fabrication and performance testing results are analyzed.The full dissertation divides into following parts:1.The theoretical basis and development UWB technology and MIMO technology are summarized,which provide a basis for subsequent works.2.A dual-polarization antenna is studied and designed.Firstly,the performance and size of the monopole antenna and slot antenna are compared,as a result,slot antenna is more favorable to miniaturization,dual-polarization antenna is designed based on this analysis;then compared with circular slot and quarter slot,find out that quarter slot is more favorable.To further control the size of the antenna,a square notch has been etched on the ground,nearly 30% area is reduced;to improve the independence of elements,an arrow-shaped ground stub is designed,which lead to a bad matching at low frequency,hence,a L-shaped match stub is added.Eventually,the operating band of the dual-polarization UWB-MIMO antenna covers the entire UWB band,neither more nor less,which indicates that this antenna can be used for UWB system needs no extra filter devices,simplification and budget-saving are achieved.Besides the isolation of the dual-polarization UWB-MIMO antenna is 20 dB which is quite ideal.3.A UWB-MIMO antenna with WLAN band-rejected is designed.Firstly,the methods of miniaturization of monopole antenna has been analyzed,half-cutting method is utilized to reduce the size of monopole antenna;since the UWB band contain other communication system band,to avoid the mutual interference,a WLAN rejection band is designed by etching a C-shaped slot on radiation patch.By adjust the size of the antenna the WiMax band-rejected is realized.To ensure the performance of antenna which applied to the MIMO system,number of antenna elements is increased,which also brings a problem that the isolation is decreased,a planar spiral is introduced to deal with this issue,as a result the isolation is increased to 20 dB.The result of analyzed fabrication and performance testing indicate that the design approach is reasonable. |
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