Design of A Dual-Band Planar Endfire Antenna With Enhanced Front-to-Back Ratio

This article describes a dual-band planar endfire antenna with improved front-to-back ratio (FTBR). The antenna is primarily composed of three sets of dipoles. By linking them with parallel double-sided matching lines, the three-dipole array enables dual-band operation. Moreover, the antenna structure is integrated with a parasitic strip along with a two-stage director, which can regulate the current phase distributions of the three dipoles, significantly widening the<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup>|5 dB FTBR bandwidth. Consequently, the antenna with a low profile of $0.009 \lambda_{0}$ obtains overlapping bandwidths ($\left(\left|S_{11}\right|\lt -10 \mathrm{~dB} \text { and } \text { FTBR }\gt 15 \mathrm{~dB}\right)$) of $\mathbf{9. 5 \%}$ $(3.2-3.52 \mathrm{GHz})$ and $35.6 \%(4.13-5.92 \mathrm{GHz})$ of the two bands, respectively. The proposed antenna has the potential to be applied to Wi-Max/Wi-Lan band wireless communication devices.