A new approach to BOR-FDTD Subgridding

In this paper the approach followed by Chilton et all. to develop a provably passive and stable 3D FDTD subgridding technique, is adapted to Body-Of-Revolution (BOR) FDTD. To this end a new set of basis functions is presented together with the mechanism to assemble them into an overall mesh consisting of coarse and fine mesh cells. To preserve the explicit nature of the leapfrog time stepping algorithm, appropriate mass-lumping concepts, again specifically adapted to the BOR-FDTD situation, are invoked. Numerical examples for toroidal cavities demonstrate the stability and accuracy of the method.