Ultra Wideband Antenna Elements on Non-Uniform Spaced Arrays

In the design of wideband arrays, the bandwidth is generally determined by the separation between elements; the small separations can increase mutual coupling, and large separations can produce grating lobes. Non-uniform arrays can increase array bandwidth by removing the periodicity in the array, but most techniques are defined using point sources as the radiating element, and the effect of having real elements with frequency dependent impedance and radiation patterns is not considered. This work applied the non-uniform spaced technique developed by Harington to reduce sidelobe levels to an eight-element linear array of Archimedean spirals. It was found that the sidelobe reduction was achieved through the entire operational bandwidth with minimal impact to the elements VSWR.