This includes a table of warning/error conditions, and many
sketches showing problem situations.
The same issue includes Selecting Wire Radius for Grid/Mesh
Models, by L.A.Oyckanmi and J. Watkins. The previous issue
includes Modeling Electrically Small, Thin Surfaces with Wire
Grids, by T.H. Hubing and J.F. Kauffman.
Wire Grid modeling of Surfaces, by A.C. Ludwig, IEEE Trans.
Antennas and Propagation, vol. AP-35, Sept. 1987 will also be
helpful. The references to these will lead to other papers.
Captions
Fig. 1.
RF model of a typical sailboat. Only key metallic elements are
shown, keel, engine and chain plates are assumed to be at water
level or below. a) View from port or starboard. b) View from bow
or stern.
Fig. 2.
Wire-grid models of a square ground-plane plate. a) A coarse
grid, which requires large conductor size, and limits antenna
locations. However, it conserves computer memory, and requires
less time for solution. b) Fine grid, suitable for use at higher
frequencies, with less restriction on antenna location. Wire size
can be one-half that of a) for the same accuracy. Grids are shown
as squares, the prefered arrangement, but may be 3, 5 or more
sides, with angles other than 90 degrees.
Fig. 3.
An alternate to an equal-sided grid, especially useful at the
antenna mounting location. Such radials may be used as diagionals
to ensure good distribution of current and better accuracy.
However, such refinements increase memory demand and run time.
Fig. 4.
Accurate models sometimes require a closed surface, to allow currents on the top and bottom to be independent. The mast mounted ground plane is an example. The ground plane may be a grid as in Fig. 2, or radial as in Fig. 3.
Fig 5.
Modeling flat or curved surfaces requires many wire sections. This side view of a typical small auto ignores many features, such as wheels and bumpers. The relatively coarse grid is adequate for reasonable accuracy at 28 MHz, but the number of wires could be increased for better accuracy at 144 MHz.
Fig. 6.
Top view of the auto of Fig. 5. In numbering wires for computer entry, time can be saved by making use of the symmetry of the structure. It is also easier to avoid errors if the wires are numbered in mirror-image pairs.
Fig. 7.
Front view of the auto of Fig. 5. This and additional views are not usually necessary to see all of the model wires, but are helpful in avoiding numbering, dimension and entry errors. Some CAD programs produce this third view automaticlly, and also output a table of line (wire) end points. If much work is to be done, a small program can be written to transfer the table to RF analysis format.