A fast Fourier transform accelerated Ewald summation technique for the vector electromagnetic rectangular cavity Green's function

A fast Fourier transform accelerated Ewald method for the computation of the vector electromagnetic rectangular cavity Green's function in terms of the electric field due to electric currents is presented and used in a boundary integral formulation. The Ewald summation technique suffers from the high-frequency breakdown when it is applied to Green's functions of wave problems. In the case of the rectangular cavity Green's function, the number of necessary terms in the spectral series grows, therefore, cubically with frequency for a given accuracy. To counteract the high-frequency breakdown, the evaluation of the spectral series is accelerated with an inverse fast Fourier transform in this work. At high frequencies, a speed-up of up to four orders of magnitude is achieved. As an application example, a reverberation chamber containing a metallic enclosure and a mode-stirrer is modeled.