Ultra-wideband Signal Radiation And Scattering

The works of this paper are mainly about the study for ultra wide-band (UWB) signal radiating-designing for effective UWB antenna,and UWB signal scattering-investigating of composite scattering for targets upon ground.Firstly,the radiating characters of UWB signal and development of UWBantenna are discussed An UWB planar horn antenna is designed This antenna is characterized with U-balun,simple construction and perfect performance. It has the good qualities of both TEM horn antenna and dipole antenna,less dimensions construction,good direction and higher efficiency. Its impedance and radiation are analyzed. Good agreements are obtained from experiment and calculation.Secondly,a model,called composite excitation method of scattering analysis for targets upon ground,is described. The method takes two steps and has unique excellence to other composite scattering methods. Its procession and calculation are very simple. This method can adapt to both time and frequency domain,similarly can be used to discuss about targets upon ground or sea surface. With this method the scattering waves of a truck model are studied in UHF band.Thirdly,as the basic study for UWB radiating and scattering,this paper improves simulation of near to far field transformation technology based upon Kirchhoff Integral in Finite Difference Time Domain (FDTD). Its distinct advantages are simple implement,and that the calculation of any far field component depends only on the value of near field component at the same time over a closed surface. The contributions of the near field on each time step to far field on different time step are calculated separately,which avoids storing the near field of the former time step,resulting in simple transformation. Meanwhile the technology for separating scattering field from total field is improved in this paper,which could eliminate the calculation error and get precise scattering field.The study of this paper is not only confirmed in the experiments of UHF VHF UWB track SAR system,but also get excellent effect And the work of this paper would promote the UWB study.