Low-Profile Air-Filled Antenna for Next Generation Wireless Systems

In this study, a novel design of insensitive antenna with improved radiation performance is designed and investigated. The antenna exhibits excellent performance in terms of impedance-matching, radiation and total efficiencies, even though it is designed and fabricated using high loss substrate (FR) with compact dimension. An L-shaped metal-ring resonator has been used as a main resonator of the antenna to operate at 18.5 GHz. In order to improve the antenna performance, a part of substrate with L-shaped configuration has been removed and a metal ring structure is inserted. By using this technique, we can improve the efficiency characteristic of the antenna and eliminate the effect of high-loss FR-4 substrate. The center frequency of the designed antenna can be controlled by adjusting the values of the antenna parameters. Since the main substrate of the resonator is the air, the antenna is insensitive for different types of antenna substrates. It has the return loss characteristic less than −10 dB in the frequency range of 17.5–19.5 GHz (more than 10% fractional bandwidth). The antenna has a very compact size with good radiation behavior and could be used in phased array antennas for next generation systems.