How do FDTD, FEM and MoM solvers differ?

From RF Design Wiki · By the RF Design Wiki editorial team · Published October 21, 2026 · Last reviewed October 21, 2026 · How we research

Three families dominate computational electromagnetics. The method of moments (MoM) solves integral equations for surface currents and is efficient for open, metal-dominated and planar structures.^[1] The finite element method (FEM) discretizes the volume with tetrahedra in the frequency domain and handles complex geometries and materials. FDTD, introduced by Kane Yee in 1966, steps fields in time on a staggered grid and yields broadband results from a single run.^[2]

How do they compare?

Method	Domain	Strengths	Weaknesses
MoM	Frequency	Only surfaces meshed; efficient for wire, planar and radiating metals	Dense matrices; complex dielectrics harder
FEM	Frequency (mostly)	Arbitrary geometry and materials; adaptive meshing	Volume mesh; open problems need absorbing boundaries
FDTD / FIT	Time	Broadband in one run; scales well; transient insight	Staircase mesh on curves; high-Q structures need long runs

Which method should I choose?

Planar circuits and antennas on layered substrates: MoM-based 2.5D. Connectors, packages, waveguide components, resonators: FEM. Electrically large, broadband or transient problems (EMC, large antennas, bodies): FDTD/FIT. Many commercial suites offer several solvers so results can be cross-checked.

What are absorbing boundaries?

Boundary conditions that simulate open space, such as perfectly matched layers (PML) in FDTD and FEM, or radiation boundaries. Their placement and quality affect accuracy for antennas and open structures.

Frequently asked questions

Who invented FDTD?

Kane S. Yee, in a 1966 IEEE Transactions on Antennas and Propagation paper.

Is FIT the same as FDTD?

Finite integration is closely related and, in the time domain on Cartesian grids, equivalent to FDTD.

What does MoM stand for?

Method of moments.

References

Online sources accessed October 21, 2026; printed works cited by edition. See all sources.

“Field Computation by Moment Methods”. R. F. Harrington, Macmillan (IEEE Press reprint 1993). 1968.
“Numerical Solution of Initial Boundary Value Problems Involving Maxwell's Equations in Isotropic Media”. K. S. Yee, IEEE Transactions on Antennas and Propagation, vol. 14, no. 3, pp. 302-307. May 1966.

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