Limitations of aperture antenna theory for accurate transient field calculation in the time domain

In this paper the research of an electromagnetic (EM) field in the time domain emitted by a planar circular aperture is presented. Numerical modeling and analytical calculation of EM realizations at specific points inside and outside of the spotlight beam are carried out using the finite integration technique (FIT) method and the analytical method of calculating impulse response function (IRF) of the aperture. It is shown that the analytical method of calculating impulse response function can provide adequate estimation of an aperture antenna EM field while emitting ultra-wideband (UWB) signal. The criterion for the applying region of the analytical method with an accuracy of less than 1% is obtained.