A low-profile, compact, wideband antenna array with cardioid-shaped radiation patterns in the azimuth plane

A low-profile, wideband, vertically-polarized antenna array with cardioid-shaped directional radiation characteristics in the azimuth plane is presented. The antenna is composed of four half loops with the shape of bent diamond arms that are fed at the center and short circuited to the ground plane at their ends. Two of the loops are fed in phase and the other two are fed out of phase. Then, these two antenna arrays are fed using a proper feed network to obtain a cardioid-shaped radiation pattern over a large bandwidth (2:1). The antenna array has a compact size with electrical dimensions of 0.65λmin × 0.4 λmin × 0.094 λmin at its lowest frequency of operation.