Modeling of thin curved sheets with the curvilinear FDTD

The finite-difference time-domain method in general curvilinear coordinates (FDTD-GCC), or nonorthogonal FDTD, permits the analysis of arbitrary, curved structures with the use of a conformal mesh. The analysis of near fields in the proximity of a thin curved dielectric sheet is a difficult task; then, ray tracing techniques and spectral numerical techniques are usually employed in the analysis of radomes. In this paper, the FDTD-GCC is modified to account for the analysis of thin curved dielectric sheets. The contravariant electric field normal to the sheet is split in two subcomponents, and new nodes are introduced where the thin sheet is located. New updating equations are inserted in the calculation of contravariant field components. The utility of the proposed technique is demonstrated in the analysis of two cylindrical radomes, the first having four not centered dipoles and the second with a centered dipole. The thickness of the radomes was 0.035-0.026 wavelengths at the central operating frequency.