SHIFTED-FREQUENCY INTERNAL EQUIVALENCE

The shifted frequency internal equivalence (SFIE) theorem involving in homogeneous regions is introduced and proven, For a lossless inhomogen eous region using a vector Green's theorem and potential formulation, it is shown that the frequency-domain electromagnetic field at frequen cy omega inside the region can be obtained using a set of equivalent v olume and surface currents radiating in free space and at the differen t frequency omega(0) The equivalent currents thus obtained are functio ns of the two frequencies, electric-and magnetic-volume-type sources o f the original problem, material parameters, and the original field ph asors at omega, and they only exist inside the region and on its bound ary. A direct application of this equivalence is that it can be used t o construct an internal equivalence at a shifted frequency for electro magnetic scattering problems if data are needed in a band of frequency . omega(0) can be kept constant while the incident field frequency cha nges and, as a result, full computation of fields at each different fr equency for volume-type equivalent sources can be avoided.