Aperture Antenna Modeling by a Finite Number of Elemental Dipoles From Spherical Field Measurements

A method to determine a distribution of a finite number of elementary dipoles that reproduce the radiation behavior of the antenna under test (AUT) from truncated spherical field measurements is proposed. It is based on the substitution of the actual antenna by a finite number of equivalent infinitesimal dipoles (electric and magnetic), distributed over the antenna aperture. This equivalent set of elementary dipoles is optimized using the transmission coefficient involving the spherical wave expansion of the measured field and using an appropriate matching method. Once the current excitation of each dipole is known, the radiated field of the antenna at different distances can be rapidly determined. Moreover, using an iterative simplification procedure, the number of equivalent dipoles is reduced, which eases the implementation of the antenna equivalent model in any existing electromagnetic code. The feasibility, the reliability and the accuracy of the method are shown using experimental data issued from the measurement of an X-band horn antenna, in two different measurement setups.