An equivalent weight vector model of array antennas considering current distribution along dipole elements

In this paper, we show that the current distribution along the parasitic dipole elements loaded by variable reactors varies greatly depending on the variable reactor value. Thus, when the directionality of an Electronically Steerable Passive Array Radiator (ESPAR) antenna constructed from parasitic dipoles is calculated, we must consider the changes in the current distribution along these elements. Therefore, we propose a method where the current weight is the value of the vector effective length of each element multiplied by the current value at the port. We also show that when the dipole length is less than approximately the half wavelength, the vector effective length is calculated for the most part by the ratio of the port voltage to the port current. From this relationship, even if the current distribution along an element is not determined, the vector effective length of a parasitic element can be calculated from the value of the variable reactor loading the element. Thus, the current distribution along the elements can be easily considered when calculating the directionality of the ESPAR antenna. We present a method that calculates the directionality of the feed dipole array antenna having mutual coupling among the elements that considers the current distribution along the element where not only the port current but also the port voltage are set as the weights. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(2): 22–35, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20232