Fractal loop elements in phased array antennas: reduced mutual coupling and tighter packing

Abstract

A common goal for array antennas has been to pack the elements tighter for lower scan angles while fighting mutual coupling. The emergence of wireless networks as a rapidly expanding market has brought about a need for very small and efficient phased array antennas. An optimal design would incorporate tightly packed elements for efficient directed transmissions that radiate effectively without significant mutual coupling. This paper presents arrays for a wireless LAN configuration, designed at 2 GHz for operation at the PCS band, that scan lower angles more efficiently than conventional designs. We show the benefits of using fractal elements in linear phased arrays to achieve denser packing while minimizing mutual coupling. Previous work has shown that fractal geometries are an effective means of miniaturizing antennas. The smaller elements can work in an array in two ways: the first is to increase the gap size between the elements, thus reducing the coupling between them; the second is to allow more elements into a fixed length array for broader scan angles. Also, there are two methods for utilizing fractal in arrays. One method is fractal arrays, which arrange elements in fractal patterns. The other method, analyzed here uses fractals as elements. Linear arrays of fractal square loop elements are analyzed using a method of moments computer code developed at UCLA.