Design Of Frequency Reconfigurable Antennas

With the development of modern communication system,a plurality of antennas on one platform for receiving or transmitting are required in order to satisfy various functional requirements such as communication,navigation,detection and so on.But at the same time,more and more loads and electromagnetic compatibility between antennas have become increasingly prominent issues.Reconfigurable antenna which realizes the functions of multiple antennas can dynamically select different working modes according to different conditions,and it makes an important exploration for effectively solving the problems of electromagnetic interference and system miniaturization.At present,the reconfigurable antenna is still in the stage of experimental research and cannot realize large-scale commercial applications.However,with the continuous development of switching technology,reconfigurable antennas will usher in a broad development prospects.Meanwhile,in the rapid development of wireless networks,many electronic devices already have WLAN/WiMAX(Worldwide Interoperability for Microwave Access)functions as one of the basic functions,which means the necessity of the development of antennas for WLAN/WiMAX frequency bands.Because the span of the antennas' frequency bands is too large,multiple antennas or multi-band antenna will inevitably be at the expense of other antenna performance.Therefore,the frequency reconfigurable design of the antenna in this frequency band will greatly improve the overall system performance of the antenna system.This paper mainly design the frequency reconfigurable antennas for the WLAN/WiMAX frequency band.These antennas aim to improve the antennas' utilization and reduce the coupling interference between the antennas.It can be summarized in the following three parts: 1.Research on the current status of the use of PIN diodes in antennas,research and analysis of some types of diodes to determine equivalent circuits of the PIN diode switches in different operating states,and introduce them into the design of frequency reconfigurable antennas.2.Have degianed two kinds of diode-switch based microstrip frequency reconfigurable antennas.One of them is a dual-unit Y-mode MIMO microstrip antenna with four diode switches.Depending on the state of the switches,the antenna can work in four different states including WLAN/WiMAX single-band and multi-band modes.The other one is a U-shaped frequency reconfigurable antenna.The antenna loaded two PIN diodes in the appropriate position on the floor changes the state of switch to make the antenna work in two different operating modes.3.Water is used as the radiating medium of the dielectric resonant antenna.A frequency reconfigurable water dielectric antenna is designed using the flow characteristics of the water.The structure of the antenna is changed by putting in or out the water in the dielectric body,so that the antenna is switched in two different operating bands of WLAN/WiMAX.In this design,the antenna has a good horizontal omnidirectional characteristic and achieve a high gain performance.