The Distribution of Current along a Symmetrical Center-Driven Antenna

The cylindrical, center-driven antenna is analyzed as a boundary-value problem of electromagnetic theory. An integral equation in the current (originally obtained in a different way by Hallén) is derived. Its solution is outlined briefly and the general formula is given. Complete curves for the distribution of current for a wide range of lengths and ratios of length to radius are given. These include curves showing the components of current in phase with the driving potential difference and in quadrature with this, and curves giving the magnitude of the current and its phase angle referred to the driving potential difference. The conventionally assumed sinusoidal distribution of current is shown to be a fair approximation for extremely thin antennas and for thicker antennas which do not greatly exceed λ/2 in length.