Optimal E-Field Vector Combination for a Highly Focused Antenna-Array

A near-field highly focused circular phased-array antenna for 5.8-GHz radio frequency identification (RFID) applications is presented. The electric field (E-field) at the focus is enhanced by a constructive vector combination in a three-dimensional (3-D) coordinate system. The array dipoles of the antenna are oriented to enhance the energy confinement at the focus, and the radii of the circular array is optimized for lower sidelobe levels. As a result, the proposed design achieves an enhanced focalization of ≈ 4 dB with reduced sidelobe levels of ≈ 12 dB compared to earlier designs.