Characteristics of high-gain ESPAR antenna using collinear dipole array

In this study, a high-gain electrically steerable parasitic array radiator (ESPAR) antenna using a collinear dipole array as a feed element is proposed, and its radiation characteristic is discussed. The feed element of the proposed antenna has a higher gain than existing ESPAR antennas, and it makes impedance matching easier via a length of coaxial cable between the arrayed feed elements and the thickness of the dielectric, using a collinear dipole array of circular dipole antennas. The proposed antenna is structured with feed elements of two-layer collinear circular dipole arrays surrounded by four parasitic elements with an array radius of /16. The variable directional radiation pattern and high-gain characteristic can be achieved through changes in reactance between the parasitic elements. The gain of the proposed antenna is 7.2 dBi approximately at the center frequency, and the return loss is less than -15 dB at the used frequencies of 2.4-2.5 GHz.