Near-field measurements on a logarithmically periodic antenna

Near-field measurements on a triangular-tooth log periodic antenna reveal that two waves exist on the structure. A transmission line wave travels from the apex to the "active region" of the antenna and excites currents in the teeth or radiating elements in this region. These currents, in turn, launch a radiated wave which accounts for the far-field pattern characteristics of the antenna. The antenna is shown to exhibit a pronounced degree of increased directivity. Near-field measurements made through one period of operation show smooth variations of the field distributions with frequency.