Compact Ultra-Wideband And Extreme-Wideband Printed Antennas

To meet the urgent requirements of national economy and military applications for the electronic warfare systems,electromagnetic compatibility and wireless communications,etc.,this dissertation makes a deeper study on several types of UWB(ultra-wideband) and EWB(extremely wideband) printed antennas.According to the demand of miniaturization,ultra-wideband impedance bandwidth,omnidirectional radiation pattern and band-notched function of the UWB printed antenna,several novel designs are proposed and their experimental verification is completed.The main results are outlined as follows:(1) Based on the analysis of antenna current distribution,a hollowed elliptical Monopole antenna with a tapered coplanar waveguide(CPW) feeder is proposed.The experimental results demonstrate that the proposed antenna achieves a ratio impedance bandwidth of 24.1:1 for VSWR≤2,covering the frequency band from 0.44 GHz to 10.6GHz,and exhibits a nearly omnidirectional radiation pattern.(2) In order to realize the miniaturization and extremely wideband impedance bandwidth of the ultra-wideband printed antenna,a semi-elliptical Monopole antenna is proposed and the liquid crystal polymer(LCP) substrate is applied to the design of the printed Monopole antenna.The main parameters are analyzed and optimized using electromagnetic simulation.The experimental results demonstrate that the semi-elliptical Monopole antenna achieves a ratio impedance bandwidth of 25.7:1 for VSWR≤2,and exhibits a nearly omnidirectional radiation pattern,while its area is only about 0.18λ_l×0.13λ_l,whereλ_l is the wavelength of the lowest operating frequency.In addition,the simulated results demonstrate that the hollowed elliptical Monopole antenna with the LCP substrate obtains a ratio impedance bandwidth above 30:1,and is more suitable for packaging and integrating with other components.(3)A novel semi-Monopole printed antenna is introduced and a significant 43%reduction in size is realized by modifying and optimizing ground plane shape and other parameters.Experiment results show that the proposed antenna exhibits an extremely wideband impedance bandwidth,a nearly omnidirectional radiation pattern and a compact size.Its measured ratio impedance bandwidth for VSWR≤2 reaches 25.9:1,covering frequencies from 0.795 to 20.6 GHz.(4) To avoid the interference between the UWB system and the wireless local area network(WLAN) system,by cutting a U-shaped slot in the radiation patch,a compact rectangular Monopole antenna with a band-notch function is proposed.The slot parameters are studied in detail,showing that the band-notched function can be realized by control the location of the U-shaped slot and the notched band can be changed by adjusting the length and the width of the slot.Experimental results demonstrate that the proposed antenna has a stop-band of 5.07 to 5.85 GHz and a super-wideband from 0.595 to 8.95GHz(15:1) for VSWR≤2.