On the analysis of the umbrella antennas using the Hallen-type integral equation

Umbrella antennas of heights
0.125\lambda
and
0.5141\lambda
are numerically and experimentally analyzed, and the effect of the junction on the current distribution is discussed. A simplified Hallen-type integral equation and an integral equation for the scalar potential of the antenna composed of straight wires are formulated and applied to umbrella antennas. The integral terms in these equations are analytically reduced to single integrals, and the extended boundary condition that the electric field vanishes on the axis of the antenna is used.