A Design Of Ultra-wideband Reconfigurable Bandnotch Antenna Based On Substrate Control

Ultra-wideband antenna has been widely concerned by researchers because of its fast speed,low power consumption and large communication capacity.Meanwhile,there may be some other system frequency bands in the communication frequency band used by UWB antenna.The existence and uncertainty of these interference frequency bands will cause interference to the current communication system.Therefore,the research of UWB reconfigurable notch antenna is of great significance.The realization of reconfigurable notch often depends on adjustable switching devices,such as pin diode,varactor diode,MEMS(Microelectro Mechanical Systems)switch and so on.The reconfigurable function of antenna notch based on the above method can only realize one of the functions of antenna opening and closing notch,or continuously adjusting the original notch frequency band.Taking this as the background,this thesis proposes a design method of ultra wideband reconfigurable notch antenna based on substrate control.This method not only realizes the opening or closing of notch,but also can continuously adjust the notch frequency band,which can be well suitable for various application scenarios of antenna.This thesis makes the following specific research:1.In order to realize the ultra-wideband performance of band-notch antenna,the ultra-wideband antenna theory is studied,and the microstrip antenna structure is selected as the basis,and a miniaturized ultra-wideband antenna is designed through the antenna wideband method.The overall size of the antenna is only 18mm×16mm×1.6mm.As the simulated results show,the bandwidth of VSWR ?2 is 3.1?12.67 GHz,and the antenna owns omnidirectional radiation characteristic.The measured results are consistent with the simulated results.The bandwidth of VSWR ?2 is 3.51?13.2GHz,and the relative bandwidth is 116%.The designed antenna meets the characteristics of UWB and miniaturization.2.In order to verify the applicability of the notch method,an ultra-wideband dual notch antenna is designed by loading L-shaped branches and SRR(split ring resonator)elements on the antenna of work 1.The simulation results show that the L-shaped branch forms a notch band of 3.12?3.98 GHz,covering the notch band of WiMAX band(World Interoperability for Microwave Access,3.4?3.6GHz).The SRR unit forms a notch band of 5.07?6.61 GHz,which covers the notch band of WLAN band(Wireless Local Area Network,5.15?5.825GHz).The measured and simulation results is relatively consistent.Two notch bands are generated at 2.98?4.98 GHz and 4.98?7.22 GHz respectively.The designed band-notch antenna can sheid the common WiMAX and WLAN bands in UWB(Ultra Wide Band)system.3.The substrate control method to realize the reconfigurable function of antenna notch is proposed,and used to improve the notch antenna in work 2.An ultra-wideband reconfigurable notch antenna is designed by removing the L-shaped branches in the notch antenna and digging a 1mm deep groove in the area etched with SRR on the dielectric plate.By placing or removing dielectric sheets owning different dielectric constants with SRR resonant ring in the groove.The simulation results show that the notch frequency band migrates when dielectric sheets with different dielectric constants are placed in the slot.if the dielectric sheet in the slot is removed,the antenna works in notch free mode.At this time,the bandwidth of antenna VSWR ?2 is 3.10?12.69 GHz.The measured results are consistent with the simulation results.When the dielectric constant of the antenna is 6.15,the antenna generates notch waves at 4.92?5.48 GHz.When the antenna is loaded with a dielectric sheet with dielectric constant of 3,a notched band is generated at 6.27?6.91 GHz.When the antenna is not loaded with substrate,the bandwidth of VSWR ?2 is 3.49?13.3GHz.Therefore,the UWB band-notch antenna formed based on the substrate control technology has the function of opening and closing the notch function and the function of migrating the notch frequency band.4.To make the antenna own double notched band,an ultra-wideband reconfigurable dual notch antenna is designed by adding L-shaped branch to the antenna in work 3.The simulated result shows that when the dielectric sheet is not loaded in the antenna groove,the antenna operates in a single notch mode.There is a notched band in the antenna between 2.90?4.14 GHz,which covers the WiMAX band.When a dielectric sheet with a dielectric constant of 6.15 is loaded into the antenna groove,the antenna has notched bands at 2.71?4.00 GHz and 5.06?6.16 GHzz,covering WiMAX and WLAN bands.The measured and simulation results are consistent.When the dielectric sheet is not loaded in the antenna groove,there is only one notch in the antenna,and the notch frequency band is 3.23?4.74 GHz.When the dielectric sheet with dielectric constant of 6.15 is loaded into the antenna,the notch frequency band is generated at 3.05?4.62 GHz and 4.94?6.17 GHz,covering WiMAX frequency band and WLAN frequency band.5.In order to accurately adjust the notch frequency band of the antenna,a varactor is loaded at a suitable position on the SRR ring of the dielectric sheet,and the notch frequency of the antenna is adjusted by adjusting the capacitance of the varactor.When the antenna is loaded with an improved dielectric sheet,the new notch band will migrate with the change of the capacitance of the varactor.The simulation results show that the dielectric chip combined with varactor can offset the notch frequency band in the range of about 500 MHz.Therefore,the substrate control combined with varactor can realize notch reconfiguration,so that the UWB antenna has the function of opening and closing notch,and realize the migration of notch frequency band in large frequency band(replacing dielectric chip)and small frequency band(adjusting varactor).To sum up,this thesis studies an ultra-wideband reconfigurable notch antenna based on substrate control,makes research on the ultra wideband,notch and reconfigurability of the antenna,and makes simulation and measurement of the designed antenna.Finally,the effectiveness of the method proposed in this thesis is confirmed by the analysis of the measured data.