C Implementation of 3D FDTD Yee Algorithm for Free Space Simulations

This C implementation of the 3D FDTD Yee algorithm provides a simplified approach to simulating Maxwell's equations on a Cartesian grid. The code structure employs a double-loop time-stepping mechanism where electric fields (E-field) and magnetic fields (H-field) are updated alternately using central-difference approximations. The implementation treats the entire computational domain as free space/air, with Perfect Electric Conductor (PEC) boundary conditions enforced at the mesh boundaries through field component zeroing. This design choice eliminates internal material complexities while maintaining physical accuracy through the Yee cell arrangement, where E and H components are spatially offset by half-grid increments. The algorithm uses a explicit time-marching scheme with Courant-Friedrichs-Lewy (CFL) condition stability control. Although limited to idealized rectangular waveguide simulations, this implementation serves as an excellent educational resource for understanding FDTD fundamentals, field update equations, and boundary condition handling in computational electromagnetics.