Changes

An infinite periodic structure in EM.Picasso is represented by a "'''Periodic Unit Cell'''". To define a periodic structure, you must open EM.Picasso's Periodicity Settings Dialog by right clicking the '''Periodicity''' item in the '''Computational Domain''' section of the navigation tree and selecting '''Periodicity Settings...''' from the contextual menu or by selecting '''Menu''' '''>''' '''Simulate > 'Computational Domain > Periodicity Settings...''' from the menu bar. In the Periodicity Settings Dialog, check the box labeled '''Periodic Structure'''. This will enable the section titled''"''Lattice Properties". You can define the periods along the X and Y axes using the boxes labeled '''Spacing'''. In a periodic structure, the virtual domain is replaced by a default blue periodic domain that is always centered around the origin of coordinates. Keep in mind that the periodic unit cell must always be centered at the origin of coordinates. The relative position of the structure within this centered unit cell will change the phase of the results.

Besides conventional rectangular lattices, EM.Picasso can also handle complex non-rectangular periodic lattices. For example, many frequency selective surfaces have skewed grids. In order to simulate skewed-grid periodic structures, the definition of the grid has to be generalized. Let us define a periodic structure as a repetition of a basic unit cell at pre-determined locations described by (x_mn, y_mn), where m and n are integers ranging from -∞ to +∞. For a general skewed grid, x_mn and y_mn can be expressed as: