Pyramidal horn gain prediction: evolution of formulations

Calibration of antennas for state-of-the-art field strength measurements above 1 GHz needs standard antennas that have given values known to within /spl plusmn/0.1 dB. Since this requirement often exceeds the verified accuracy of calculated gain values, these standards must in general be established by making absolute gain measurements. However the required precision measurements are "costly and complex". Therefore attempts have been continuing to accurately predict the gain of standard EMC antennas. The pyramidal horn antenna, by virtue of its desirable features, such as gain stability, accurate gain computability, ruggedness and wide bandwidth, is one of the most widely used antennas for generating standard electromagnetic fields. Naturally the prediction of its gain is significant. The advent of the geometrical theory of diffraction, in particular, has led to various formulations to predict the pyramidal horn gain. All these methods aim to match as close as possible with measurement. In this paper, the evolution of pyramidal horn gain prediction formulations is examined. Their relative performance is also discussed.