On Antenna Tolerance Theory

To predict the loss of gain of antennas due to surface devi- ations which are not distributed uniformly over the aperture, an exteasion of Rum's theory is presented. It is found that the assumption of uniform error distribution, in general, underestimates the axial gain of an antenna whose surface deviations have regional variations over the aperture. This effect becomes signilkant only when the surface deviations cannot be considered small as compared to the wavelength. Furthermore, it is found that the assumption of a uniform distribution of error may have a signifi- cant effect on the predicted scatter even when surface deviations are not large. Assuming that the de*tions from uniform distribution are also random, a correction term to the theory is also presented.