Radiation efficiency measurement of communication antennas with Wheeler Cap method

One method to measure the radiation efficiency of an antenna is the Wheeler Cap method. It uses a wave guide, operated below his cut off frequency to eliminate the far field of the antenna. Using two measurements (with and without Wheeler Cap) it is possible to calculate the radiation efficiency. In this paper the impact of different shapes, material and the minimum heights of the Wheeler Cap are investigated. The measurement of radiation efficiency is not precise but the ease of measurement makes the method highly attractive. This contribution concludes that the shape and the material have no influence to the measured radiation efficiency as long as the design criterion like cap size are kept constant.