| Determining the electric field pattern of waveguide antennas in the near-field region is becoming increasingly important in many applications (microwave-induced hyperthermia, phased-array radar, microwave heating/drying systems). One of the methods that has been used to make calculations in the near-field region is the equivalent dipole method. This method, while accurate in the far-field region, becomes increasingly inaccurate at small distances from the antenna being analyzed. This dissertation presents a new method, called the equivalent waveguide method, in which the electric field pattern in both the near and far-field regions of a waveguide antenna is determined by replacing the waveguide antenna by an array of smaller, uniformly-illuminated waveguide antennas. Comparisons between the equivalent waveguide method, the equivalent dipole method and the measured electric field patterns are made. These calculations and measurements show that the equivalent waveguide method is more accurate, is much simpler to implement and executes in a much shorter amount of time than the previous published equivalent dipole method. Furthermore, this method is quite general in scope, and is suitable for analyzing any aperture antenna whose aperture fields are either known or can be approximated. |
