Aperture Antennas

Abstract

AbstractAperture antennas include those having large planar areas such as parabolic reflectors. The classic technique used in the calculation of aperture antenna radiation patterns is applying the equivalence principle followed by physical optics approximations. The equivalence principle is based on replacing the physical antenna aperture with a virtual antenna aperture consisting of an ensemble of Huygens sources, each of which is a source of spherical wavelets. The total pattern is taken as a construction of these Huygens secondary waves. It can be further shown that a simple Fourier transform relation exists between the amplitude distribution of these sources and the radiation pattern in angle space. For many aperture antenna problems, the distribution can be assumed from theoretical considerations or determined empirically from near‐field probes of the aperture fields. But there are many other antennas such as horn antennas, where a virtual aperture can also be constructed in front of the physical aperture in order to model and analyze the antenna. Thus, an aperture antenna has more to do with the method used to model the antenna than its actual form.For most aperture antenna problems, these classical techniques are adequate and give reasonably accurate results. However, more modern analysis techniques such as the method of moments (MoM), the finite‐element method (FEM), and the finite‐difference time‐domain (FDTD) method are also discussed. These methods are more robust and accurate, but the complexity and large amount of computer resources required must be traded off with the accuracy desired. Generally, they are infeasible for high‐gain antennas.