Low-sidelobe patterns from small, low-loss uniformly fed linear arrays illuminating parasitic dipoles

Low-sidelobe radiation patterns with good directivity can be generated by antennas consisting of a linear array of parasitic dipoles in front of a smaller linear array of active dipoles fed uniform voltages, a configuration that facilitates the task of feed network design. The fundamental effect of the parasitic array is to allow the length of the active array to increase by a factor of 2 or more, thereby narrowing beamwidth while the parasitic elements keep side lobes low to ensure good directivity. For a given number of active elements, performance improves as the number of parasitic dipoles increases, levelling off when there are about twice as many parasitic as active elements. The method is easily generalizable to planar arrays.