A novel precise method of measuring the efficiency of arbitrary low-gain antennas

A precise method is developed for measuring the efficiency of arbitrary low-gain antennas. The multipole expansion coefficients of the antenna are first derived from Spherical Near Field Scanning measurements and are then employed to generate an accurate but general network model of the antenna's mutual impedance properties. The antenna is totally characterized and the efficiency is determined by means of an additional set of measurements employing a reflecting screen. The measurement results for a lossy aircraft blade antenna are presented. It is found that the theoretical and measured results for this aircraft blade antenna, having an efficiency of 42%, do not precisely agree at all points, although the maximum spread in results corresponds to a variation in efficiency from 38% to 46%.