Research And Design Of Planar Ultra-wideband Antennas

With the rapid development of scientific and technological modernization,wireless communication technology is continuous improving fast.As an important part of wireless communication system,antenna has been paid more and more attention.Nowadays,the miniaturization,multifunction and broadband of antenna has become the development trend.And the planar ultra-wideband(UWB)antenna has been widely used in the various portable tools and communication systems because of its small size and low profile and other advantages.In this thesis,introduction of the history and present situation of planar UWB antenna has been given first,and done the basic parameters of the antenna,including the input impedance,S parameters,bandwidth,direction figure and coefficient,gain,radiation efficiency and polarization.Discussion of the technology and method of the antenna miniaturization and broadband is shown then.And several methods of antenna feeding,and especially focus on coplanar waveguide feed method which is suitable for broadband communication have been introduced carefully.On the basis of these fundamental theory/methods,our research is shown as follows.Firstly,by using rectangular loop patches,we have designed a miniaturization planar UWB microstrip antenna,and slotted a rectangular groove on its backside.Simulated and measured results showed that-10 dB impedance bandwidth of this antenna reaches 3.1 to 15.7 GHz,and the relative bandwidth is 134.04?,which can completely cover the UWB frequency range and have a good omnidirectional radiation characteristics.Then,based on this fashion,a coplanar waveguide feed UWB antenna has been designed,which used the radiation patch form of the annular umbrella,and its "around ground" structure can greatly expand the bandwidth.Simulated and measured results showed that the antenna can satisfy the demands of UWB work.Meanwhile,it has advantages of miniaturization,less cost and easy integration with microwave circuit integration,etc.Thirdly,by using multi-side method,a commonly used in designing the multi-frequency antenna method,dual-frequency band microstrip antenna for wireless local area network(WLAN)has been designed.This antenna can work in WLAN frequency range which is stipulated by IEEE802.11 b/g and IEEE802.11 standard and has good omnidirectional radiation characteristics.Finally,in order to filter out the WLAN frequency signal which is most commonly used in UWB frequency range,we design a planar notched UWB antenna.It is used the compound radiation patch structure of rounded rectangle ring and cross side,and uses commonly notched method of slot and tuning side,which effectively filters the interference of WLAN signal,and reduces the cost of the equipment and complexity of the communication system.