Time-domain solvers versus analytical regularisation in the integral-equation analysis of canonical scatterers

One´s understanding of diffraction phenomena is enhanced by examining both time- and frequency-domain aspects, particularly when complex scatterers incorporating edges and cavities, are involved. Some features such as high-Q resonances are better perceived in the frequency-domain, whilst other broadband features such as specular return and creeping waves appear more clearly in the time-domain. The article discusses the merits of several low and and high frequency techniques, concentrating upon time-domain-integral equation techniques. The validity of codes based upon these techniques can be established by comparison with rigorous solution techniques for classes of canonical problems, such as spheroidal shells, which include the required features of interest (such as cavities). In this context the method of regularisation discussed is particularly useful