Series-fed two dipole array antenna using bow-tie elements with enhanced gain and front-to-back ratio

Abstract

In this paper, a miniaturized series-fed two dipole array antenna with bow-tie elements (STBDA) for mobile communication applications is presented. In the proposed antenna, two bow-tie-shaped dipole elements of different lengths, which are serially connected through a coplanar strip line, are used instead of conventional straight strip dipole elements in a series-fed two dipole array (STDA) antenna. In addition, a planar ground reflector is replaced by a V-shaped one. A modified integrated balun consisting of a microstrip line and slot line is used to match the input impedance of the antenna to the 50 feed line. As the flare angle of the bow-tie dipole elements increases, the lowest operating frequency of the antenna is shifted toward the low frequency and the average gain is lowered. To validate the proposed approach, an STBDA antenna with a flare angle of 10° covering a frequency band ranging from 1.7 to 2.7 GHz and with a gain >5 dBi is designed and fabricated on an FR4 substrate. Its performance is compared with that of the STDA antenna. Experimental results show that the proposed antenna presents a 48.8% bandwidth in the range of 1.69–2.78 GHz, a stable gain of 5.8 to 6.3 dBi, and a front-to-back ratio (FBR) of 14–17 dB with a 10% size reduction in total width of the antenna. In fact, the characteristics of the half-power beam width and FBR of the STBDA are improved compared to those of the STDA.