Planar ESPAR antenna based on Yagi-Uda array design for space diversity applications

A planar Electronically Steerable Parasitic Array Radiator (ESPAR) antenna is proposed based on an Yagi-Uda array design for space diversity applications. Even though an conventional ESPAR antenna has various advantages of a simple structure, small volume, and cheap fabrication cost, it requires a 3-dimentional (3-D) form-factor. The proposed one is designed with planar active dipoles and parasitic element arrays from an Yagi-Uda design methodology. Four orthogonal arrays are configured of two active elements and eight parasitic elements, which is implemented with two bi-directional arrays. Each array has an active element, two reflector elements, and two director elements. The proposed architecture has been implemented on a planar substrate, and controlled with switched reactance for each parasitic element. From the experimental results, the proposed planar ESPAR antenna presents four orthogonal beams with a maximum gain of 10.74 dBi and a front to back ratio of 14.7 dB.