Design Of Miniaturized Multi-Band And Broadband Antennas Based On Zeroth-Order Resonance

With the increasing demand of wireless networks,WLAN(Wireless Local Area Network,WLAN)system has become an part of people's daily life.Compared with WLAN system,WiMAX(World Interoperability for Microwave Access)has higher transmission rate and longer transmission distance.If the two systems are combined effectively,they will play a greater role.Antennas as the transfer interface of WLAN/WiMAX communication system,they play an important role in the communication system.In addition,with the integration of electronic devices,small size antennas have become an urgent need.The appearance of zeroth-order resonant antenna provides a new way to solve the problem of miniaturization,so it has attracted much attention in recent years.This paper mainly focuses on the multi-band and wide-band research of zeroth-order resonant antenna.The specific work completed includes the following aspects:(1)A 2.45GHz/3.5GHz/5.6GHz triple frequency antenna based on zeroth-order resonance is designed.The antenna is based on a 5.6GHz monopole antenna structure,achieves dual-band by loading a zeroth-order resonant element with virtual grounding structure,adding a new resonant frequency at 2.45GHz,and then loading a ?/4 radiation branch corresponding to 3.5GHz to realize triple-band.The designed triple frequency antenna has good impedance matching characteristics in triple bands and covers the required frequency band of WLAN,but the 3.5GHz bandwidth is too narrow to meet the application requirements of WiMAX system,then a zeroth-order resonant antenna fed by coplanar waveguide is proposed,by grounding with a high impedance line,the intermediate frequency bandwidth is increased,WLAN and WiMAX bands are fully covered.(2)A miniaturized broadband zeroth-order resonant antenna is designed.This antenna not only expands the bandwidth,but also realizes the miniaturization of the structure.At the same time,a good matching of 3.3-4.9GHz band is achieved by loading step capacitors.Moreover,omnidirectional radiation with efficiency of over 90%is achieved and it can be used in WiMAX wireless communication system.(3)An ultra-wideband zeroth-order resonant antenna with working bandwidth of 2.76?13.4GHz is designed.This antenna achieves multiple resonance modes through three-element composite left/right-hand transmission line cascade structure and loading open resonant rings,and widens the bandwidth by combining different resonance modes.In addition,the parallel grounding effect is realized through the open-loop hole on the resonant ring,which eliminates the complexity of probe grounding and improves the design flexibility.