Conical feed transparent antenna

A transparent antenna using conical metallic feed is proposed. Characteristics of transparent conductive films are revised. It is verified that the sheet resistivity of a conductive transparent layer differs significantly from that of a metallic (copper) layer with a thickness equal to the penetration depth. The integral equation for the current along a transparent metal radiator is written and solved. It is shown that the flat antennas with transparent conductive coating have low efficiency as the current along them decreases exponentially. For this reason the electrical characteristics of these antennas depend only weekly on the arm length, and exhibit no sharp resonant behavior. These problems can be overcome partially using a proposed conical feed implemented by a metallic layer. The conical feed creates a uniform currents distribution along the cross section of the radiating (transparent) layer. The results of calculation and experiment indicate that the proposed antenna is effective at frequencies above 2 GHz, has a very wide bandwidth and may be substantially shorter than a quarter-wave radiator.