A Study of Planar Printed Dipole Antennas for Wireless Communication Applications

Abstract

This paper presents the structure analysis, numerical design simulation, fabrication, and measurements of printed dipole-antennas for wireless communications. Two types of integrated microstrip balun, λ/4 open-stub and via-hole structures, are studied and compared. A developed finite-difference time-domain (FDTD) code and commercial Ansoft HFSS EM solver are used for design simulation and comparison. Design examples of 2.4- and 5-GHz printed dipole antennas with integrated balun are fabricated on an FR-4 printed-circuit-board (PCB) substrate. It is found that the 2. 4-GHz printed dipole with a via-hole balun has wider bandwidth (30%) than that with an open-stub balun (20% for VSWR < 2). The 5.7-GHz printed dipole with a via-hole balun has a bandwidth of approximately 20% (for VSWR < 2). The effect of the printed dipole length and arm-width on the antenna resonant central frequency and bandwidth has also been investigated. The measured antenna patterns are very close to that of an ideal dipole antenna for both 2.4- and 5.7-GHz printed dipole. Also, the design metrology of the printed dipole is applied to design a 5 GHz polarization-diversity planar antenna fabricated on a FR-4 PCB. It consists of two orthogonal 5-GHz printed dipoles with a microstrip via-hole balun feeding structure integrated with a p-i-n diode circuit to switch and select the desired antenna polarization. In the antenna design simulation, again the FDTD is employed to analyze the entire antenna structure including the lumped elements of the p-i-n diode switching circuit. Since the printed dipole structure can be used in many extended antenna structures, this study will be very useful for antenna design in wireless communication applications.