4.2.1 The geometry panel

When the `add' button in the geometry section is pressed, the following pop-up screen appears.

All geometries are internally treated as a polygon. To make it easier for the user, wxGBTool has explicit support for three other types: Hyperbolic-plano lenses, circular lenses and circles. By selecting the corresponding tab the parameters associated with a certain type is geometry appear.

Note that everything is measured in meter (metric).

• HP Lens: Add a hyperbolic-plano lens.
  • Focus: Focal distance of the lens.
  • Diameter: Size of the lens.
  • Number of segments: number of segments along the curved surface of the lens. If the number of segments is low, only a poor approximation of the curved surface will be obtained. The Nero2d solver will further subdivide the segments if they are larger than one tenth of a wavelength. This will however, not improve the curvature. If on the other hand, the number of segments is too high, so that a the segments are much smaller than one tenth of a wavelength, much more memory and calculation time will be required by the Nero2d solver. It is good practice to chose the number of segments so that the segments are approximately half a wavelength in size. This will yield a smooth curve, and optimal segment sizes inside Nero2d. Note that you yourself need to calculate the number of segments taken into account the wavelength and the size of the lens.

  Note that the actual shape of the lens depends on both the focal distance parameter and the refractive index (epsilon and mu).

• Circular Lens: Add a circular lens.
  • Diameter: Size of the lens.
  • Thickness: Thickness of the lens.
  • Radius A: Radius of the left side (can be negative).
  • Radius B: Radius of the right side (can be negative).
  • Number of segments: See HP Lens.
• Circle: Add a circle
  • Radius: Radius of the circle.
• Polygon: Add a polygon Enter the coordinates of the polygon in a counter clockwise fashion. The coordinates are entered like this `x ; y', e.g. for a triangle, enter

                  -1 ; -1
                   1 ; -1
                   0 ;  1
  

  Any number of points can be added to list. Take into account however that the objects can not self-intersect and that the points need to traverse the contour in a counter clockwise fashion. The final point is automatically connected to the first, do not enter it twice. Also note that the edges of the polygon are automatically subdivided by the Nero2d solver.

In the lower left section you can chose between a PEC or dielectric object and you enter the relative permittivity and permeability in the same way coordinates are entered real ; imag. Note that for lens objects, only a dielectrics are possible.

In the lower right section you can enter the position of the object and chose a rotation angle (in degrees).

Once a change is made, the object can be pre-viewed by pressing the `update' button. If the `Ok' button is pressed, the object is added to scene and is shown in the main window. Note that objects can be embedded into other dielectrics (to simulate for example coatings), however, objects can not touch each other of overlap.