In this section, the dipole antenna with a very thin radius is considered. The dipole antenna is similar to the short dipole except it is not required to be small compared to the wavelength (at the frequency the antenna is operating at).For a dipole antenna of length L oriented along the z-axis and centered at z=0, the current flows in the z-direction with amplitude which closely follows the following function:Note that this current is also oscillating in time sinusoidally at frequency f. The current distributions for the quarter-wavelength (left) and full-wavelength (right) dipole antennas are given in Figure 1. Note that the peak value of the current is not reached along the dipole unless the length is greater than half a wavelength.
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