Research On Timefrequency Characteristics Analysis Of Wideband Vivaldi Antenna And Periodic Array Technique

With the upgrading of wireless communications technology, modern antennas withwideband,multiband,miniature,multifunction characteristics have become importantresearch topics in the domain of Antennas. As a main part of a research project, thisdissertation is mainly concerned with the design of wideband Vivaldi antennas andwideband dual-polar Vivaldi antenna. The wideband Vivaldi arrays,the BAVA periodarrays and wideband powder divider have been investigated systematically.Firstly, this dissertation investigates Vivaldi antennas and dual-polar structure.Thewideband Vivaldi antenna which works at1.5-12GHz is designed, based on the analysisof wideband and low-loss balun.In addition, the impedance characteristics of the Vivaldiantenna are improved and the gain at the low frequency is also increased by introducingperiodicity ripple on antenna surface.This dissertation also studies the impulse responscharacteristics of Vivaldi antenna in time domain,including fidelity and group delay.Moreover, the wideband dual-polar Vivaldi antennas which work at1.5-8GHz aredesigned. The structure design of dual-polarization is effective because measurementsresults agree well with simulation.Secondly,by the use of period boundary condition,the wideband dual-polar Vivaldiarrays and the wideband(DMDP)BAVA arrays have been investigated. Based on theanalysis of element impedance and radiation characteristics,the two arrays achieve thewideband and wide-angle scanning performances.The wideband dual-polar Vivaldiarrays can work at1.5-8GHz with the wide-angle scanning of±45°;the wideband(DMDP) BAVA arrays can work at3-9GHz with the wide-angle scanning of of±70°.Finally, studies a variety of wideband feeding network, including microstripmulti-section power divider, microstrip loaded short-circuited stubs power divider,coupled-line loaded short-circuited stubs power divider and coupled-line loadedopen-circuited stepped stubs power divider.The frequencies of the power dividers are all3.1-10.6GHz.Every power divider has its own characteristic:multi-section power divideris of the best isolation effect，loaded short-circuited stubs power divider has theadvantage of small dimension; coupled-line power divider has filtering characteristicbesides wideband characteristic, in other words,the out-of-band rejection is very good.