Corrections to the General Fourth-Order FDTD Schemes

The sampling weights and approximate stability criteria for two general fourth-order accurate FDTD schemes were previously derived by Smith et al. However, inconsistencies between several of their governing equations and corresponding solutions were recently discovered. Upon rederiving the full 3-D, fourth-order FDTD dispersion relation, two separate errors were identified in the original work. This paper details these errors and provides corrected sampling weights. Exact stability criteria are also derived and stated for the first time.