A MORE EXACT FRESNEL FIELD DIFFRACTION RELATION

Abstract

In general, diffraction relations which were developed for optical purposes have been found to be useful in the prediction of electromagnetic fields due to radiating apertures but, because many radio-optical measurements must be made so close to the aperture that the mathematical approximations in the Fresnel field relation often are invalid, new relations, free from these approximations, must be developed. The optical, Fraunhofer relation has been found to predict the distant field with good accuracy and for this reason the Fresnel field is calculated from the distant field equation by the Fourier transform method. The calculation is found to result in an integral which reduces to Fresnel's integral when the standard optical approximations are made in it. The integral has not been evaluated.