The Research Of Multifunctional Antennas Based On Probe Feeding Technology

With the continuous development of wireless communication system,RF front-end devices are developing towards multi/wideband,multi-functional,miniaturization and integration.The application of antenna diversity and filtering antenna in dual/broadband is one of the important representatives of this trend.As one of the important methods to mitigate the channel fading,antenna diversity technology is widely used in mobile communication system.The traditional design method of dual frequency diversity antenna is antenna arrays.In recent years,for reducing the size,the design of a single radiation element has appeared,but there is still a large feeding network.The direction of miniaturization is worthy of further study.As a fusion design of antenna and filter,filter antenna has the functions of radiation and filtering,which reduces the size of RF devices and avoids the insertion loss when the antenna and filter are cascaded.The application of filtering antenna in dual/broadband is still one of the research hotspots.As one of the most important methods to realize the dual/broadband of microstrip patch antenna,probe feeding technology is widely used.Therefore,the probe feeding technology has great potential in the application of dual/broadband filtering and diversity antenna.Based on the probe feeding technology,this thesis studies its application in dual band diversity antenna and dual/broadband filtering antenna,and designs three antennas.The main contents of this thesis are as follows:1.A dual band dual port pattern diversity antenna is designed.Firstly,the basic theory of diversity technology is introduced.Secondly,a dual port single frequency band pattern diversity patch antenna is designed by using coplanar waveguide and folded microstrip line.Then a T-probe is loaded on the top of coplanar waveguide and inverted L-shaped branches is added on the outer conductor of coplanar waveguide,which achieves dual band performance.Finally,the-10 dB common impedance bandwidth of the dual ports in the lower frequency band is 14%,while that in the upper frequency band is 16%,and the isolation in the two bandwidth is lower than-20 dB.The maximum radiation direction in lower frequency is ?=4° and ?=0 ° for two ports and that in upper frequency is ?=26° and ?=56° for two ports.The correlation coefficient of the two frequency bands is very low,and the diversity gain is greater than 9.98,which indicates that the antenna has good diversity performance.2.A broadband filtering antenna is studied and designed.Firstly,a broadband patch antenna fed by coplanar waveguide and T-shaped probe is designed.Secondly,by using the method of designing the filtering antenna,the transverse stubs are loaded on the back of coplanar waveguide,and,the U-shaped slots are respectively etched on the left and right sides of the patch.Therefore,two radiation nulls are generated at the lower and upper edges of the passband and the frequency selectivity of the antenna is improved.Meanwhile,the impedance bandwidth is futher increased.Finally,the-10 dB impedance bandwidth is 71.17%,and the average realized gain is 4.2 dBi.Two radiation nulls appear at 2.25 GHz and 5.3 GHz,which enables frequency selectivity.3.A dual band filtering antenna is designed.Firstly,a dual band patch antenna with T-probe and coplanar waveguide is designed and its working frequency includes ISM(Industrial Scientific Medical)band.Secondly,by loading two transverse stubs on the back of the coplanar waveguide transmission line and etching U-shaped,L-shaped and linear slots on the patch,three radiation nulls are generated on the upper edge of the lower frequency band and the upper and lower edge of the upper frequency band,which improves the gain roll off rate of the antenna.Finally,the-10 dB impedance bandwidth of lower and higher band are 16.1%and 14.1%respectively.The maximum gain of lower and higher frequency band can reach 4.2 dBi and 5.8 dBi respectively,and the gain curve is quasi elliptical.