Presented is a methodology for the synthesis of complex electromagnetic sources based on the wave field synthesis. In particular, the wave-front of a propagating electromagnetic wave, generated by a suitable antenna, is synthesised using a set of point sources with specific amplitudes and phases, calculated with a suitable optimisation algorithm. This approach permits a reduction of the descriptive parameters of the scenario under consideration, a strong reduction of the computational resources and consequently a reduction of computational time necessary to simulate the scenario under investigation. The obtained results have been assessed considering experimental measurements, in particular an ultra-wideband antenna of a real microwave imaging system for breast cancer detection, has been considered. The agreement between numerical and experimental data is quite good.