Research On Ultra-wideband Impulse Radiating Antenna(IRA) Technology

In recent years,due to wide-band characteristics and high directivity,impulse radiating antennas(IRA)have been applied not only in nuclear explosion simulation,high-power microwave weapons,electromagnetic interference,countermeasures,and other military fields,but also in civilian fields such as medical imaging,treatment and target recognition.This thesis focuses on analyzing the characteristics in time and frequency domain of the antenna.At the same time,the miniaturization technology and ultra-wideband(UWB)impedance matching technology are studied.The main contents are as follows:Firstly,an UWB feed with an asymptotic conical dipole profile is designed,and the characteristics in frequency domain of IRA which combined with the feed and the reflector are studied in detail.During the researching,the impedance loading technology is adopted,which effectively expands the operating band to lower frequency,realizes the miniaturization and the horizontal size of the antenna is reduced to 30% of the original one.The voltage standing wave ratio of the optimized IRA is lower than 2.2(matching with 100 ?)within0.1 GHz ? 4 GHz,the aperture efficiency is higher than 30%.What's more,it has stable radiation performance in a bandwidth of 40 times with an electrical size of0.33?max×0.12?max(?max is the wavelength at the lowest operating frequency).Under the excitation of double exponential pulse and first-order Gaussian pulse signal with peak power of 1 W,the far field voltages are 57.75 V and 72.9 V,respectively.Secondly,based on basic principle of UWB matching,a gradient balun with an impedance bandwidth of more than 40 times is designed,which has a structure of coaxial to parallel transmission line.Different cutting methods of the coaxial outer conductor are discussed,and a new type of upper opening parabolic balun is proposed as the feeding structure of the IRA.Finally,for Half IRA(HIRA),the influence of the size of floor on radiation pattern is studied,and the antenna power capacity is analyzed.Studies show that the radiation pattern beam on the elevation plane is shifted due to the finite floor.Some methods can improve the antenna power capacity,such as thickening dielectric,using high dielectric strength medium and distributed resistance loading as much as possible.The feeding arms of optimized HIRA are made of a dielectric plate covered with metal layers on both sides,which greatly reduce the weight of the antenna.In the operating band of 0.1 GHz ? 4 GHz,the voltage standing wave ratio of HIRA is lower than 2.3,the aperture efficiency is higher than 25% which proves good radiation performance of the antenna.The measurement results of 1.5 m HIRA at the end of this thesis are in good agreement with the simulation ones,which proves the effectiveness of the design method.