A novel low-profile broadband circularly polarized bowtie antenna with AMC surface

A novel low-profile bowtie antenna is designed for broadband and circularly polarized communications. The proposed bowtie antenna is composed of four radiated branches, and each branch consists of three hexagons, three hexagonal rings and a semi-hexagonal ring, which can generate multi-resonance and result in a wide impedance matching bandwidth. In addition, the introduction of hexagonal rings increases the current path, bringing in small antenna size (0.39AL *0.39AL *0.012AL). Two ports are utilized to feed the radiators to achieve circular polarization. To improve the circularly polarized property, two pairs of rectangles, with different dimensions in x and y direction, are added inside the four semi-hexagonal rings. Moreover, an AMC surface is designed as the ground of the bowtie antenna to achieve low-profile and high-gain performance. The presented AMC ground, made up of 12*12 units, brings the composed antenna about a low profile. The total size of the composed antenna is 84*84*8mm
³
(1.03AL *1.03AL *0.098AL). The simulated results show that the presented low-profile broadband bowtie antenna achieves a wide impedance bandwidth from 3.69 to 6.22 GHz (51.06%) and an axis ratio bandwidth of 55.3% (3.4GHz-6GHz). And the maximum gain can reach 8.31dBic at 4GHz.