Error in projection of plane waves using the RWG basis functions

The error in projection of the induced current of a plane wave using the Rao-Wilton-Glisson (RWG) basis functions has been studied numerically. The vector current in a finite area is expanded by full and half RWG basis functions, and the unknown projection coefficients are solved by the Galerkin's method. The error is calculated for different polarizations, different meshes and mesh densities, and different incident angles. It is found that the error in the projection of curl-free vectors is less than that of divergence-free vectors, and the RWG basis has the projection error in range of 10 to 20 percents for the mesh with 10 unknowns per wavelength