Printed Dual‐Frequency Directional Antenna Loaded With Dual‐Parasitic Strip

Abstract

In this paper, the directional antenna is developed to construct the printed dual‐frequency directional antenna for a 1‐GHz/2.3‐GHz dual‐frequency sensor application. An auxiliary dipole element generating the higher resonant mode is set on a primary dipole element introducing the lower resonant mode. The feed balance is also designed to cover the desired frequency between two resonance frequencies, which is based on the microstrip line (MS) to coplanar stripline (CPS) transition. To realize the directional antenna, two reflector elements are utilized, and one of them is a stepped‐width reflector on reducing the size of the antenna. In addition, the parasitic strip works as the lumped element used to obtain good impedance matching. A series of simulations are performed on the MS‐to‐CPS transition, the dual dipole element, the reflectors, and the parasitic strip to determine the optimal antenna design. A prototype is fabricated based on the optimal results of the simulation. Concerning the measured results, the proposed antenna has well unidirectional radiations, good radiation efficiencies, and low cross‐polarization levels at any operating frequencies.