A Dual-Band Planar Endfire Antenna with Enhanced Front-to-Back Ratio

A dual-band endfire antenna with planar structure and high front-to-back ratio (FTBR) is investigated. The antenna is mainly composed of three pairs of dipoles. Connected by parallel double-side compensate lines, a three-dipole array can inform a dual-band operating mode. Moreover, a parasitic strip and a two-stage director are incorporated into the antenna structure to regulate the current distributions of the three dipoles, significantly widening the 15 dB FTBR bandwidth of lower and upper bands. Consequently, the antenna obtains measured overlapping bandwidths ($|{S}_{\text 11}|$ <-10 dB and FTBR >15 dB) of 9.5% [(3.2 to 3.52) GHz] and 35.6% [(4.13 to 5.92) GHz] of the two bands, respectively. The peak gains of the antenna are 7.42 dBi at 3.3 GHz and 9.08 dBi at 5.85 GHz. The proposed methodology of this design can apply to applications related to Wi-MAX/Wi-LAN wireless communication systems.