GE - End Geometry Input
Purpose:To terminate reading of geometry data cards and reset geometry data if a ground
plane is used.
Field Parameter Last column in each field
---- ---- -------------------------
I1 gpflag 5
- gpflag - Geometry ground plain flag.
- 0 - no ground plane is present.
- 1 - Indicates a ground plane is present. Structure symmetry is modified as
required, and the current expansion is modified so that the currents an segments
touching the ground (x, Y plane) are interpolated to their images below the
ground (charge at base is zero)
- -1 - indicates a ground is present. Structure symmetry is modified as
required. Current expansion, however, is not modified, Thus, currents on
segments touching the ground will go to zero at the ground.
- The decimal number fields are not used.
- The basic function of the GE card is to terminate reading of geometry data
cards. In doing this, it causes the program to search through the segment data
that have been generated by the preceding cards to determine which wires are
connected for current expansion.
- At the time that the GE card is read, the structure dimensions must be in
units of meters.
- A positive or negative value of I1 does not cause a ground to be included in
the calculation. It only modifies the geometry data as required when a ground
is present. The ground parameters must be specified on a program control card
following the geometry cards.
- When I1 is nonzero, no segment my extend below the ground plane (X,Y plane)
or lie in this plane. Segments my end on the ground plane, however.
- If the height of a horizontal wire is less than 10-3 times the
segment length, I1 equal to 1 will connect the end of every segment in the wire
to ground. I1 should be -1 to avoid this disaster.
- As an example of how the symmetry of a structure is effected by the presence
of ground plane (X,Y plane), consider a structure generated with cylindrical
symmetry about the > axis. The presence of a ground does not effect the
cylindrical symmetry. If however this same structure is rotated off the
vertical, the cylindrical symmetry is lost in the presence of the ground. As a
second example, consider a dipole parallel to Z axis which was generated with
symmetry about its feed. The presence of a ground plane destroys this symmetry.
The program modifies structure symmetries as follows when I1 is nonzero If the
structure was rotated about the X or Y axis by the GM card, all symmetry is lost
(i.e., the no-symmetry condition is set). If the structure was not rotated
about the X or Y axis, only symmetry about a plane parallel to the X, Y plane is
lost. Translation or a structure does not affect symmetries.
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