Accuracy of a Gaussian beam

The accuracy of a multimode Gaussian beam is discussed. Novel modifications are given to the conventional Gaussian beam formulation derived using the paraxial approximation. With the modifications, the field can be calculated accurately with the Gaussian beam. Modified multimode Gaussian beam techniques are used for calculation of the beam of a corrugated horn antenna. Phase and amplitude patterns given by this method are compared with measurements and other theoretical methods, namely Huygen's principle and the modal matching technique. The meaning of the phase and phase center is also discussed.>