The dipole antenna shown in Figure 13 consists of two quarter-wavelength traces driven by a 533-MHz voltage source with a magnitude of one volt. In this case, the source is located within the FEM region. Since the width of the traces is very small compared with the width of the FEM region, a non-uniform mesh is used to discretize the structure.

 

Initially, the relative permittivity of the dielectric slab is set to 1.0. Thus, the configuration is a half-wavelength dipole in free space. The input file for SIFT5 is as follows,

# example 3: a dipole driven by a voltage source located within the FEM region

unit 0.25 mm

boundary 0 0 0 164 82 2

celldim 0 2 2 x

celldim 2 162 16 x

celldim 162 164 2 x

celldim 0 40 10 y

celldim 40 42 1 y

celldim 42 82 10 y

celldim 0 2 1 z

dielectric 0 0 0 164 82 2 1.0 0.0

conductor -480 40 2 82 42 2 10 1 1

conductor 82 40 0 644 42 0 10 1 1

isource 82 41 0 82 41 2 533 z 1

output -480 40 2 0 42 2 y example3.out

output 164 40 0 644 42 0 y example3.out

The source is modeled as a current filament that coincides with two tetrahedron edges. Near the junction and source areas, small cells are used. The FEM region is divided into 1200 tetrahedra. The boundary is divided into 2632 edges. The number of unknown edges for the final matrix equation is 1900. This problem requires 80 Megabytes memory and 20 hours to run on a Sun Ultra workstation. The current distribution on the traces obtained using EMAP5 is plotted in Figure 14. For comparison, the results obtained using the Numerical Electromagnetics Code (NEC) and the IBM EM Simulator are also plotted. Figure 15 shows the results obtained by EMAP5 and the IBM EM Simulator when the dielectric constant is set to 10.0. In both cases, the results obtained using the different methods are similar.

 

Figure 15. Current distribution on the dipole for the geometry shown in Figure 13 (e _r=10.0).