7.1    Effective FDTD mesh grid

 

QuickWave delivers an advanced feature, which allows observing the FDTD mesh created by QW-Editor and sent to QW-Simulator. This is an important tool of verification if the geometry of the project was correctly defined by the user and correctly understood by the mesh generator and transformed to the FDTD mesh. This testing mechanism is available in Test Mesh window. The Test Mesh window shows layer by layer how the FDTD grid has been created by the QW-Editor. The FDTD grid displays are available in all three planes and the user can easily switch between subsequent layers. FDTD cell pointed by a cursor is described in the Test Mesh window by its position (given with FDTD cell indexes), cell type, and filling media. This is an important tool of verification if the mesh used in QW-Simulator corresponds to the intentions of the user. User's errors in application of the QW-Editor will be visible here. For example, it is a typical error that the user assigns to a particular element the medium outside instead of inside or vice versa. Such a setting may be in conflict with settings in other elements, producing rather unexpected results, which will be easy to detect using the Test Mesh option.

The user can switch and adjust the FDTD grid display to his needs using Test Mesh window option as described in Mesh display.

The user shall notice at this point that the structure display in Test Mesh window is surrounded by metal frame. The size of this frame is 2 cells at the lower and upper boundary in X and Y directions; one cell at the lower boundary in Z direction (or half a cell if magnetic symmetry is used) and no frame is added at the upper boundary in Z direction. Note that the metal frame cells are included in the cells indexing, thus the first circuit cell index is 3, 3, 2 in X, Y, and Z direction respectively.

 

The Test Mesh option is extensively used in User Guide 3D: Boolean operations on elements and objects.

 

The effective FDTD mesh grid feature delivers other useful information with correspondence to Test Mesh window:

The question of verification of the assumed media properties becomes even more important in the case of dispersive media. In QW-Editor we introduce dispersive properties of materials by choosing appropriate model (e.g. Debye, Drude, Lorentz) and specifying a few parameters. Such a system may be prone to human errors and the user may want to verify if the frequency-dependent properties of the medium in the frequency band of interest are such as he required. This can be done by invoking Dispersive Media Info dialogue, where the media parameters can be displayed in the frequency band of interest (the band specified in the project's Postprocessing range). Note that the window used to display the dispersive medium parameters is essentially the Results window and thus a variety of options including scaling, mathematical operations on curves etc. is also possible here.