A Wideband Omnidirectional Antenna Array With Low Gain Variation

An omnidirectional antenna array with wide band and low gain variation in the horizontal plane is proposed in this letter. The antenna unit of the array is composed of two vertically arrayed omnidirectional elements and the associated feeding network. 3-D dipoles with vertical arms and parasitic dipoles are introduced in the antenna unit to significantly enhance the bandwidth and decrease the gain variation. An array with three vertically installed units is fabricated. Each unit is 120
${^\circ}$
rotated compared to the neighboring one for a lower gain variation. The array exhibits a broad bandwidth of 56.4% (1.54–2.75 GHz) for
${\rm VSWR} \leq 1.5$
, a gain around 7 dBi, and a low gain variation around 1.5 dB, which may find applications in base station for wireless communication or spectrum monitoring/jamming systems .