Current-distribution measurements on thin conducting sheets

The current distribution on the surface of metal strips illuminated by a plane wave end on has been measured at 3Gc/s. Rectangular, triangular and circular strips were used, with the incident electric field parallel to the surface of the strip. Amplitude and phase were measured, using a balanced shielded loop as a magnetic probe. The measurements show a strong standing-wave pattern over strips having dimensions of a few wavelengths. For semi-infinite strips, the standing-wave pattern no longer exists. The currents may be explained in terms of waves transmitted over the surface of the strip and guided by the surface. Surface-wave measurements were also made on dielectric-coated strips. The results agree with the theory for an infinite surface of the same reactance.