Superdirective Wideband Array of Planar Monopole Antenna With Loading Plates

A wideband superdirective array of a two-element planar plate monopole antenna is presented. Initially, a two-element, closely spaced array of a simple rectangular planar monopole antennas is considered. Based on a relative phase shift of 100 between the two elements, over the 3-6-GHz bandwidth this antenna array provides directivity of 3.5-6.9 dB. In order to achieve a higher directivity over a wider frequency bandwidth, a pair of small parallel plates is attached to the radiating edges of the rectangular planar monopole antenna. It is shown that this antenna array with element spacing of 2 cm and a relative phase shift of 135 between the elements produces 3.1-7.5 GHz impedance bandwidth with 7.7-10.1 dB of directivity. This antenna has an efficiency of 60%-91% over the bandwidth. Simulation and experimental results are provided and discussed.