A single-arm spiral antenna

An array consisting of four-by-four spiral antennas is constructed using the pair-element (PE) technique. The 3-dB axial ratio bandwidth is improved to 8.9% by the PE technique from 3.8% for an array without using the PE technique. The −14-dB return loss bandwidth is widened to 6.4% from 3.6%. In addition, a beam with a tilt angle of 21 degrees is demonstrated, where the spiral elements are excited in 90-degree phase steps.