An Approximate Expression for the Principal Beamwidths of Directive Antennas in Terms of Aperture Fields

摘要

An approximate, but general, formula for the half-power principal beamwidths of directive antennas is derived from the Fourier transform of the aperture electric field. The derivation, which can be accomplished by expanding the transform in a Taylor series, is greatly streamlined by introducing a Gaussian beam approximation. The formula, which also relates beamwidth to directivity indirectly through simple integrations of the aperture field, reduces to a very compact expression in terms of the zero and second order moments of the aperture distribution for linearly polarized, uniformly phased aperture fields.