The electromagnetic field within circular apertures.

The electromagnetic field components within a circular aperture in a plane conducting screen have been investigated experimentally. The measured fields and those predicted by some recent theories are compared for plane waves irradiating the screen at normal incidence, using apertures from one-quarter to two wavelengths in diameter. Several measurements for non-normal incidence are included. Experimental techniques have been devised for the measurement of the aperture fields very close to the diffracting edge. A sharp increase in the magnitude of some of the field components has been observed to occur in the region less than 0.15 wavelengths from the edge. This result supports recent theoretical predictions