360° electronically controlled beam scan array

This paper describes a circular array composed of 25 wire monopole elements centre fed and positioned in two concentric rings over a ground plane. There is one driven element and 24 parasitic elements, 12 of which are loaded with an electronically controllable capacitive load. The array uses two state reactive loads to change the electrical length of the loaded elements in order to direct the beam over a 360° beam scan angle in 30° increments. The antenna array operates at 1 GHz and yields over its entire beam scan range a gain of 12 dBi±0.45 dB, a VSWR of 1.51±0.08, beamwidth of 54°±3° and a front to back ratio of 12.24 dB±2 dB, were ± indicates the variation on the measured beam as it is electronically rotated. The bandwidth of the array is 16% for a VSWR<2.