The Field Surrounding an Antenna in a Waveguide

In many applications of waveguides an antenna projecting into a waveguide is employed. It is often very desirable to know the maximum electric field strength surrounding such an antenna. The only method for obtaining a very accurate and conventional result in any given particular case is a laborious numerical one. Such information is not of general interest and its only use is to assist in the design of a particular system. It was with the object of obtaining a reasonably general although somewhat approximate result that the method described here was employed. A special type of antenna in a circular waveguide able to carry without attenuation only one wave mode (T.E.1, 1) was considered. By extrapolation, information for a rectangular waveguide with a cylindrical antenna having a hemispherical tip can be obtained. A solution is found only over the mid-plane of the antenna and waveguide, as it is in this plane that the fields are usually noted to be greatest. The results of the investigation are given in a mathematical form for a circular waveguide, and also in the form of sets of curves convenient for practical use in the case of rectangular waveguides.