Time-domain asymptotic analysis of transient whispering-gallery mode radiation excited by a UWB pulse source

A time-domain (TD) asymptotic analysis is developed to describe the radiation and scattering phenomenon of the transient whispering-gallery (WG) mode radiation excited by an ultra-wideband (UWB) pulse source. The TD asymptotic solution is derived by applying the saddle point technique to the transient WG mode radiation integral characterized by the 2nd-order approximation of the phase term in the integrand. The TD asymptotic analysis offers the new physical insight to the transient WG mode radiation. The accuracy of the TD asymptotic solution is examined by comparing with the reference solution.