This simple Biconical Geometry utilizes two unique XFdtd^® features, timed switches and transient far zone field calculation. Two cones are statically charged and then discharged using a timed switch.

This simple biconical geometry utilizes two unique XFdtd features, timed switches and transient far zone field calculation. Two cones are statically charged and then discharged using a timed switch.

The two charged cones with static electric field displayed are shown in Figure 1. To obtain this field distribution the cones were charged using a Gaussian pulse current source placed in the gap between the cones. The XFdtd calculation proceeds until the transients dissipate, resulting in the static field distribution shown in Figure 1. Then a switch between the two cones closes, discharging the biconical capacitor. This discharge produces transient currents which radiate far zone fields.

Figure 2 shows the voltage between the cones as they are charged, reach their static potential difference of about -200 volts, and then discharged. The charging process requires about 25 ns and reflections of the charging pulse from the ends of the cones are evident in the plot.

Figure 3 shows both the charging current that flows through the current source and the discharge current that flows through the switch. The first spike of discharge current involves the charge in the vicinity of the biconical gap. As time progresses the current flow becomes a damped sine wave, with the frequency determined by the length and shape of the biconical capacitor.

Figure 4 shows the electric field radiated by the biconical capacitor as it is first charged and then discharged. The discharge current spike is evident in this plot, followed by the damped sinusoidal behavior of this geometry.