# General Tips

General tips, which are not solution method-specific, are presented to reduce runtime and memory consumption.

• Select the optimal solution method for the application
Select the solution method best suited to the model based on the electrical size of a problem, the geometrical complexity, and available computational resources.
• Use adaptive (continuous) frequency sampling for frequency loops instead of linearly spaced sampling:

When computing results over a frequency band, using adaptive (continuous) frequency sampling can reduce the number of frequencies required to capture all the resonances in the result. You can initially limit the number of samples to get approximated results or use the low convergence accuracy option (fewer samples, smooth frequency response).

Attention: Using continuous (interpolated) frequency sampling with multiple solution requests in the same model could result in a long runtime.

For example, requesting all currents over a frequency range requires interpolation of the current for each triangle/wire segment. The interpolation taking place results in extra frequencies to be computed as well as long delays between frequency samples.

For example, if a plane wave is incident on an electrically large object and the radar cross section (RCS) is required, then the mesh size at the back of the object can be made coarser than the front of the object due to the very small currents at the back of the object.

If critical output at the back of the object (away from the plane wave) is being requested, such as the near fields or the received power on an antenna at the back, then finer meshing may be required in this area.

As the incident plane wave is uniform in phase, a mesh size coarser than the standard $\frac{\lambda }{10}$ 1 mesh size can be used. In some cases, useful results can be obtained with mesh sizes of around $\frac{\lambda }{4}$ .

• Use symmetry for hybrid methods
The hybrid methods are methods where the MoM is used in part, for instance MoM / PO or MoM / FEM. Geometric symmetry reduces the triangle integral calculation time and storage required for the mesh elements, while electric and magnetic symmetry saves computation time and memory.
• Use symmetry for large meshes
When symmetry is specified, only the part on one side of the symmetry plane is meshed and then mirrored to complete the model. Meshing is faster and the memory to store the geometry (~300 bytes/triangle) is reduced.
• Store or re-use the solution

The Solver stores the current coefficients to a .str file by default. If no .str file was computed, the option can be enabled.

If you want to change or add field computations or other outputs, then the Solver can read the solution from the .str file and only compute the new or changed outputs.

• When calculating S-parameters, only enable the necessary ports

Each active port in an S-parameter calculation acts as a new solution. The additional solutions increase the runtime and the additional runtime depends on the solution method.

For example, if for a two-port model, you are only interested in S11 and S21, it is unnecessary to set port two as an active port.

• Use domain decomposition (numerical Green's function) when many changes are made to only a small part of the model
For a large method of moments (MoM) model2 where a small part of the model is changed multiple times, use the numerical Green's function (NGF). The NGF method solves the static domain (non-changing part) of the model once and then re-uses the solution (LU-decomposition) of this part together with the changing part (dynamic domain) for each new change. This method can reduce run time by a factor of 10 or more.
• Use the DGFM to solve medium to large finite sized antenna arrays

The domain Green's function method (DGFM) is a method that takes first order coupling effects between antenna elements into account. However, a large saving in memory is obtained as the full matrix is not solved.

The DGFM is used by default to solve antenna arrays defined using the finite antenna array tools unless the DGFM is de-activated

1 $\lambda$ is the free space wavelength.
2 This include surface equivalence principle (SEP) and volume equivalence principle (VEP).