7.3     Mesh Settings

The  button in Model tab and Parameters->FDTD Mesh Settings... and Mesh->FDTD Mesh Settings... commands from main menu invoke Mesh Parameters dialogue, but the Presentation settings will be not available.

Additionally the  button in the 2D Window toolbar and Setup-> FDTD Mesh Settings... command from 2D Window menu invoke Mesh Parameters dialogue.

The Mesh Parameters dialogue allows defining the parameters of the FDTD mesh.

In the right part of the dialogue box we state in which part of the circuit the FDTD mesh is to be created. Typically we want to mesh the entire volume occupied by our structure. Then we shall keep the default setting in the Adjust to section: Objects checked on. However, sometimes we may wish to analyse only a part of the structure (for example, to speed up the simulation by exploiting spatial symmetry or to analyse only one selected discontinuity with refined meshing). In such a case, we should uncheck the Objects box, and set the mesh boundaries explicitly. The UV axis to XY box can be used as one shortcut, introducing the X and Y mesh limits equal to the 2D-Axes Setting of the active 2D Window. The other shortcut is Limits to XYZ, which introduces the X, Y and Z mesh limits equal to the outermost positions of all the defined elements, objects, and ports. Make sure that all the declared ports are situated inside the meshed part. Otherwise it will be impossible to perform the simulations.

In the left part of the dialogue box we can set the maximum FDTD cell sizes along the axes X, Y and Z when we decide not to use Amigo option (can be changed pressing Edit button). The X to YZ button copies the X cell size into the Y and Z ones. Note that the QW-Editor will try to put an integer number of cells between each pair of the neighbouring mesh snapping planes. It will assume as a precondition that any dimension of the cell cannot exceed the maximum size defined here. Thus the maximum cell size should be chosen very carefully. It will play a crucial role in finding a balance between the conflicting requirements for high accuracy and computing time, taking also into account the limits of the computer memory.

Presentation visible permits to display or hide the meshing. Pen can be used to modify the width and colour for mesh lines.

Edges force linear mesh checked on causes that edges actively force the Max cell size towards the inside of the circuit. Edges (understood as outermost boundaries of the circuit) are implicit limits of the mesh, and as such they act as the outermost mesh snapping planes. However, we cannot edit the edges to assign to them any particular forced cell size (which we can do for explicitly available mesh snapping planes). The Edges force linear mesh option allows doing this implicitly.

Splanes info button opens the Mesh/Splanes Info dialogue with the list of all mesh snapping planes (also called special planes) created in the project.