The complete surface current distribution in a normal-mode helical antenna

The complete surface current distribution on a structure with close parallel wires such as a helical antenna can be computed by using the method of moments with a general surface patch formulation. The distribution varies substantially from the common assumption that it is uniform around the wire cross-section. Transverse (circumferential) currents are shown to be present, although they are relatively weak when the helix is not operating at its self-resonant frequency. The effect is still significant when the wire separation distance is relatively large