Aperture antenna radiation

The technique that can be applied to the calculation of aperture antenna radiation patterns is the equivalence principle followed by physical optics. The equivalence principle is based on replacing the physical antenna aperture with a virtual antenna aperture consisting of an ensemble of Huygen's sources, each of which is a source of spherical wavelets. The total pattern is taken as a construction of these Huygen's secondary waves. A Fourier transform relation exists between the amplitude distribution of these sources, and the radiation pattern in angle space. For most aperture antenna problems, these classical techniques are adequate and give reasonably accurate results. However, more modern analysis techniques such as method of moments (MOM), finite element method (FRM), and the finite difference time domain (FDTD) method are also discussed. These are more robust and accurate, but the complexity and large amount of computer resources required must be traded off with the accuracy desired.