| With the rapid development of wireless communication technology,people’s demand for wireless communication equipment is also increasing.Antenna,as an important part of wireless communication system,has been given the requirements of miniaturization,multi-frequency,broadband and integration.The Composite right/left-handed transmission line（CRLH-TL）structure can generate negative,zero and positive resonant modes,which can easily achieve miniaturization,multi-frequency and broadband antenna.Asymmetric coplanar waveguide（ACPW）,as an extension of coplanar waveguide,has more flexibility in structure,and is easy to be conformable with CRLH-TL,which can easily integrate antenna.This thesis focuses on the structure of ACPW and CRLH-TL,and designs miniaturized,multi-band and wide-band antennas applied to WLAN and Wi MAX systems.The specific work is as follows:（1）To solve the problem of large size of tri-band antenna,a miniaturized tri-band antenna operating at 2.45GHz/3.5GHz/5.5GHz is designed.The antenna uses the monopole antenna terminal fed by ACPW to load the CRLH-TL resonant unit with short circuit structure to realize the three-band operation.The measured antenna|S11|<-10 d B impedance bandwidth were2.32～2.52 GHz,3.42～3.56 GHz and 4.94～5.98 GHz,passband range peak gain higher than 1.2d Bi,1.4 d Bi and 1.8 d Bi.Compared with the same type of three-band antennas,the antenna proposed in this thesis realizes the miniaturization of multi-band antennas,and can be applied to WLAN and Wi MAX communication systems.（2）Two kinds of CRLH-TL resonant units for broadband operation are proposed.One is a combination of curved line inductance and slot capacitance.The other is sinusoidal loaded Archimedes helical inductance and slot capacitance.The patch antenna fed by ACPW is combined with two kinds of CRLH-TL resonant units to widen the working frequency band of the antenna.Considering that the simulation performance of the two antennas is roughly the same,only the first antenna is fabricated to verify its performance.The measured results show that the first operating frequency band of the antenna is 2.34～4.25 GHz,the absolute bandwidth is 1.91 GHz,the relative bandwidth is 58%,and the peak gain in the passband is all higher than2.2 d Bi.The second operating band is 5.1～6.6 GHz,the absolute bandwidth is 1.5 GHz,the relative bandwidth is 26%,and the peak gain in the passband is all higher than 3.3 d Bi.Antenna has good radiation characteristics in the working frequency band,which can meet the requirements of all the frequency band of WLAN and Wi MAX system,and has high application value.（3）A circular monopole double notch UWB antenna fed by ACPW is designed.Two flexible and controllable notch bands are realized by loading an open resonant ring and an L shaped slot on the circular patch of the antenna.The measured antenna|S11|<-10 d B impedance bandwidth is 3.0～12.6 GHz,its peak gain is higher than 2.1 d Bi,and it has good trap property in the range of 3.25-3.81 GHz and 4.9-5.9 GHz,which can effectively block the interference of WLAN and Wi MAX systems.Compared with the same type of notch UWB antenna,the antenna designed in this thesis has the advantages of small size,flexible structure and so on. |
