# How to select Design and Simulation Software for Antenna Design

The answer to this question depends to a great extent on the particular antenna problem that is to be analyzed. There are various antenna simulation tools based on different numerical techniques. Software for antenna design can be selected based on antenna type and size. Choosing the right technique for solving an antenna problem is important, as choosing the wrong one can either result in incorrect results, or results which take excessively long to compute.

Several key EM simulation technologies have emerged over recent years. Out of these, simulation technique the Method of Moments (MoM), Finite Element (FEM) and Finite Difference Time Domain (FDTD) solutions are used almost in all commercial software like Momentum, HFSS, CST, Sonnet, EMPro etc. Although in principal these technologies could be used to solve the same problems there are often good practical reasons why one particular simulator is better suited to solving a particular problem type.

There are many considerations to take into account when assessing the suitability of a particular EM analysis tool for antenna like

• How easy is it to create the geometric model?
• Does this EM solver suitable for my antenna?
• Do you need to be an ‘EM guru’ to run the tools?

The first major consideration is whether antenna geometry is ‘Planar’ in nature or whether it is genuinely ‘3D’. For ‘Planar’ structures, Method-of-Moment (MoM) provides the most efficient simulation method and for that reason generally MoM would be recommended for the analysis of planar antennas. Whilst for true ‘3D’ antenna structures like Horn, Parabolic Dish, and Waveguide Antenna then either FEM or FDTD will usually be more appropriate. Applications better suited to FDTD simulation include the likes of antenna placement on vehicles/aircraft and the analysis of antenna performance in the presence of detailed human body models.

Method of Moments

Numerical techniques based on the method of weighted residuals are called moment methods. EM modelers have come to use the term “moment method” synonymously with “boundary element method”. The boundary element method is a moment method applied to the solution of surface integral equations. Most commercial moment method codes are boundary element codes, however the method of weighted residuals can be applied to differential equations as well as integral equations. In general, moment method techniques do an excellent job of analyzing unbounded radiation problems and they excel at analyzing PEC (perfect electric conductor) configurations and homogeneous dielectrics. They are not well-suited to the analysis of complex inhomogeneous geometries.

Finite Element Method

Finite element techniques require the entire volume of the configuration to be meshed as opposed to surface integral techniques, which only require the surfaces to be meshed. However each mesh element may have completely different material properties from those of neighboring elements. In general, finite element techniques excel at modeling complex inhomogeneous configurations. However, they do not model unbounded radiation problems as effectively as moment method techniques.

Finite Difference Time Domain

Finite difference time domain (FDTD) techniques also require the entire volume to be meshed. Normally, this mesh must be uniform, so that the mesh density is determined by the smallest detail of the configuration. Unlike most finite element and moment method techniques, FDTD techniques work in the time domain. This makes them very well-suited to transient analysis problems. Like the finite element method, FDTD methods are very good at modeling complex inhomogeneous configurations. Also, many FDTD implementations do a better job of modeling unbounded problems than finite element modeling codes. As a result, FDTD techniques are often the method of choice for modeling unbounded complex inhomogeneous geometries.

Other Techniques

There are numerous other electromagnetic modeling techniques. Methods such as the Transmission Line Matrix Method (TLM), Generalized Multipole Technique (GMT), and others each have their own set of advantages for particular applications.