High efficiency wideband printed monopole antenna with enhanced gain using artificial magnetic conductor surface

Combining the benefits of a low profile, high gain, high efficiency, and wideband operation in a planar antenna presents a significant challenge for antenna designers. Low-profile wideband antennas often suffer from low gain. This study introduces a compact wideband artificial magnetic conducting surface (AMCS) positioned behind a wideband omnidirectional antenna to enhance its gain across the operational frequency range. This integration allows the radiating structure to achieve both high gain and wideband functionality in a single design. In this research, a wideband planar monopole printed antenna is developed to function as an omnidirectional radiator, delivering excellent impedance matching and radiation efficiency across the frequency range of 3.9-7.2 GHz (60% bandwidth) in free space. The free-standing antenna dimensions are 30 mm × 20 mm (0.39 λ_o × 0.3 λ_o), where λ_o corresponds to the lowest operating frequency of the antenna). It exhibits a gain ranging from 2 dBi to 4.5 dBi over this frequency band. To improve gain, a wideband AMCS is designed, consisting of just 3 × 3 unit cells with overall dimensions of 9 × 9 cm (1.1 λ_o × 1.1 λ_o). The AMCS is placed parallel to the planar antenna at a distance of 1.75 cm behind it. The gain of the AMCS-backed antenna reaches up to 9 dBi without compromising bandwidth or impedance matching. Furthermore, the radiation efficiency remains above 98% across the operational band of 3.6-7.2 GHz (66% bandwidth). The wideband antenna and AMCS are fabricated to experimentally validate the performance of the AMCS-based antenna. Measurements of impedance matching, gain, and radiation efficiency demonstrate close alignment with simulation results, confirming the effectiveness of the proposed design.