Error estimates for Yee's method on non-uniform grids

In this paper we analyze the order of convergence of Yee's finite difference time domain method on non-uniform, but rectangular, grids. A simple analysis shows that the local truncation error is only first order, yet numerical experiments show that the method is always second order convergent. However, by analyzing the error in more detail, we are able to prove supra-convergence and show that the method is second order convergent regardless of the non-uniformity in the mesh.<>