A planar quasi-yagi antenna with a new microstrip-to-CPS balun by artificial transmission lines

Abstract

In this paper, we discuss a new design of quasi-Yagi antenna for 5 GHz WLAN applications. The antenna employs a new microstrip-to-CPS balun which is realized by a newly proposed planar artificial transmission line (ATL). This ATL is composed of microstrip quasi-lumped elements and their discontinuities. By simultaneously increasing the series inductance and shunt capacitance of the line section while keeping their ratio unchanged, microstrip lines with a wide variety of characteristic impedances and electrical lengths can be synthesized in a very compact form. To further improve the antenna front-to-back ratio, in this paper the dipole arms are meandered such that the truncated ground plane is relatively large compared to the radiator. The overall size of the antenna is 45 by 30 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The antenna configuration, design methodology, and simulation results are investigated in detail in the following sections.