Compact electromagnetic test range using an array of log-periodic antennas

The design of an array of seven log-periodic dipole antennas is described: this is intended to generate an approximate plane wave in the near field. The array is used as an illuminating antenna for a compact range primarily intended for electromagnetic susceptibility or emission measurements, but is also potentially usable for antenna measurements. It is capable of operation at lower frequencies than reflector antennas, and achieves good-quality plane waves in the near-field region. The design procedure was based on a numerical near-field synthesis technique that produced a set of complex excitations for the seven elements. The magnitude-only synthesis technique was found to give better results than alternative methods. The resulting computed field distributions showed that acceptable approximations to a plane wave could be generated over a substantial quiet zone, and an experimental test of an array constructed in accordance with the design algorithm showed good agreement with the predicted performance