Low-Profile Conical-Pattern Slot Antenna With Wideband Performance Using Artificial Magnetic Conductors

A slot antenna with conical patterns and wideband performance based on artificial magnetic conductors (AMCs) is presented in this paper. It has four symmetrical square radiating slots and a meandered feeding network etched on the both sides of the upper substrate to achieve a compact size. Wideband performance is achieved by tuning the resonant frequencies of the one-wavelength slot and quarter-wavelength monopole modes close to each other. The electric fields generated by these four slots cancel each other, resulting in a radiation null in the center. And the AMC surface converts the radiation pattern into conical pattern. The simulation and measurement results on S11, radiation patterns, efficiencies, realized gains, and SAR values are given. The performance of the proposed antenna in a practical helmet model is studied. The results show that the proposed antenna has an impedance bandwidth of 4.83-6.25 GHz (1.42 GHz, 25.6%), maximum gain of 6 dBi at the elevation angle of 36°, and low 1 g SAR values of less than 0.22 W/kg for the application of the IEEE 802.11a WLAN system.