How can we simplify the round wire model?

Modeling Center-Driven Dipole with FEKO

According to the equivalent radius concept, the round wire can be modeled as a flat ribbon. The width of the ribbon should be 2 mm, which is 4 times the radius of the round wire. A finer mesh was used for the ribbon model and is shown in Figure 1. The input impedances of the round wire model and the flat ribbon model are compared in Figure 2. The input impedance at 150 MHz is 81.8 + j47.7 ohms for the round wire model and 81.8 + j46.6 ohms for the flat ribbon model. The flat ribbon model computes the input impedance in only 24 seconds.

Modeling the dipole as a "wire" rather than as a "cylinder" greatly improves the simulation time. The wire model is shown in Figure 3. A wire port is defined at the center of the wire to produce the source voltage. The cylindrical model and wire model results are compared in Figure 4. The resonant frequency is 144 MHz, and the impedance at 150 MHz is 81.8 + j46 ohms. The input impedance of the wire model is the same as that of the cylindrical model. The simulation time is only 30 seconds.

Fig. 1. Flat ribbon model

Fig. 2. Input Impedance comparison between the round wire and flat ribbon

Fig. 3. Vanishingly thin wire model

Fig. 4. Input Impedance comparison between the round wire and vanishingly thin wire