Design On Broadband Planar Printed Antennas For Wireless Local Area Networks

The continual promotion and maturity of semiconductor and RF technology have witnessed the rapid development of the wireless communication business with limited area and short range.Especially,the wireless local area network(WLAN)communication system based on IEEE802.11a/b/g standard has integrated in people's daily life.Coincident with this phenomenon,the antennas who are core devices using as receiver and transmitter in radio system will play a pivotal role in equipment operation.From the relevant fundamental conception and theory of antenna design,this thesis summarizes some domestic and overseas researches and analyses corresponding to broadband printed antenna.Aiming to the designing of broadband printed antenna used in short distance WLAN,the strategy of combining the theory analyzing and numerical simulation is employed.The working band and polarization mode of antenna are studied.The main researches are organized as follows:1.First,a printed slot antenna with broadband bandwidth fed by microstrip line is proposed.Antenna's operational frequency has covered 2G/3G/LTE/WLAN communication bands.The main radiator is two annular slot structures.Using a pair of Z-shaped fine slot distributed on diagonal line as the tuning stub,the design can achieve-10 dB return loss from 1.275 to 2.703 GHz of bandwidth 71.8%.Antenna has stable radiation patterns and the gain better than 2 d Bi within operational frequency.2.Second,a planar printed slot circularly polarized(CP)antenna with unidirectional pattern based on WLAN 2.4 GHz is present.Antenna's primary radiator contains an annular slot and parasitic strip line.Through adding perturbations and cutting corner,the expected CP feature has been obtained.Results show that-10 d B impedance bandwidth is 1.795~2.515 GHz of 36.6%,3 d B axial ratio(AR)bandwidth is 2.358~2.502 GHz of 5.92% with gain more than 2 dBi.3.Finally,a dual unidirectional printed antenna due to IEEE802.11 g standard is proposed.The main structure consists of the coplanar waveguide(CPW)feed line,an annular ground,and two parasitic C-shaped strip lines,which make antenna two broadband operational bands(2.4/5.8 GHz).A mushroom periotic electromagnetic band gap(EBG)structure is used as the reflector that makes design dual unidirectional broadband radiation.The simulated result indicates that antenna's impedance bandwidth is 34 %(1.83~2.58 GHz)and 12.2%(5.62~6.35 GHz),respectively.The gain is more than 5 dBi in lower band,while 9 dBi in upper band.