July, 2010 1
Understanding Time Domain Meshing in
CST MICROWAVE STUDIO®
When performing numerical solutions of Maxwell’s Equations in electromagnetic
simulations, it is well known that the quality and type of mesh used for discretizing
the computational volume plays a critical role in simulation speed and accuracy. In
fact, the choice of a particular meshing technique is often determined by the trade-
offs between speed, accuracy and memory requirements. In this respect, meshing in
the time domain stand outs because it offers a number of advantages over other
existing techniques such as those based on Finite Elements (FEM). In particular, it
offers more flexibility for achieving a good compromise between simulation speed and
accuracy. It is less memory demanding and it has a linear scaling of computational
effort (the simulation time increases in the same proportion as the number of mesh
cells), which is the best one can hope for in a numerical technique. For many
applications, this translates into the ability to simulate larger problems using fewer
computational resources in a shorter time.
The purpose of this paper is to provide our CST MICROWAVE STUDIO® user community
the required meshing knowledge and techniques so they can achieve the
aforementioned benefits. Both automated and “manual” meshing techniques are
discussed in detail.
1. Meshing Basics
In time domain methods, the type of mesh most commonly used is the so called
hexahedral mesh. A hexahedral mesh is that where the computational volume
(simulation space containing our model) is discretized by means of variable size
rectangular cuboids (in general, ∆x≠∆y≠∆z). Each cuboid is referred to as a mesh cell.
See Fig. 1.
Fig. 1: Basic definitions of: a) mesh cell and b) hexahedral mesh.
In discretized form, each mesh cell represents a small volume in space where the
electric and magnetic fields are computed. Obviously, the more mesh cells we use for
discretization, the more accurately the field gradients will be captured. However, the
total number of mesh cells should not be increased carelessly as it will have a direct
impact on the total simulation time. Thus, it is important to use a mesh that is well
balanced and offers a good compromise between simulation speed and accuracy (See
Fig. 2).
a)
b)
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