Fast Calculation of Far-Field Patterns of Reflector Antennas with Fast Fourier Transform

The development of a numerical technique for the fast calculation of farfield radiation patterns of reflector antennas is reported. The technique applies to antennas subjected to a small angle approximation, with no restrictions as to the reflector shape and as to the feed location. Considerable acceleration of calculations is achieved through the utilization of a two-dimensional FFT algorithm associated to the numerical integration procedure. Numerical examples, processed with FORTRAN programs, are presented, showing actual computational time reductions varying from 20 to 250. Results are compared to those obtained with classical Gauss-like numerical integration, with quite good agreement. Some extensions of the technique are also suggested.