A hybrid high-order algorithm for radar cross section computations

We describe a high-order method for computing the monostatic and bistatic radar cross section (RCS) of a class of three-dimensional targets. Our method is based on an electric field surface integral equation reformulation of the Maxwell equations. The hybrid nature of the scheme is due to approximations based on a combination of tangential and nontangential basis functions on a parametric reference spherical surface. A principal feature of the high-order algorithm is that it requires solutions of linear systems with substantially fewer unknowns than existing methods. We demonstrate that very accurate RCS values for medium (electromagnetic-) sized scatterers can be computed using a few tens of thousands of unknowns. Thus linear systems arising in the high-order method for low to medium frequency scattering can be solved using direct solves. This is extremely advantageous in monostatic RCS computations, for which transmitters and receivers are co-located and hence the discretized electromagnetic linear system must be solved for hundreds of right-hand sides corresponding to receiver locations. We demonstrate the high-order convergence of our method for several three-dimensional targets. We prove the high-order spectral accuracy of our approximations to the RCS for a class of perfect conductors described globally in spherical coordinates.