Directivity computation of radio base station antennas via cylindrical NF-FF transformation

As well known, the directivity value associated to a radiating system denotes its capacity to concentrate the electromagnetic radiation in a desired direction. The computation of the total radiated power, which is obtained by integrating the radiation intensity on the far field (FF) spherical surface, represents the crucial point in the directivity evaluation. The full numerical integration can be used to this end only in numerical simulations, and becomes very time consuming when the computation of the radiation intensity is onerous, as in the case of electrically large antennas. An efficient Sampling Interpolation (SI) formula for determining the total radiated power from the knowledge of a nonredundant number of the radiation intensity samples has been proposed in [1]. It is in closed form, does not depend on the type of antenna under test (AUT) and allows one to efficiently estimate the directivity from simulated or measured samples with a very significant reduction of the number of data with respect to [2].