A Printed Dipole Antenna for WLAN Applications with Anti-interference Functionality

This work presents a novel design of printed dipole antennas using an integrated balun for 2.4GHz applications. In this design, two FR4 substrates with a thickness of 0.8mm have been used to form a dipole, balun, and ground structure. The antenna’s balun is consists of a $\Gamma$ - shaped feed and a slot line. Indeed, the integrated balun acts as a coaxial cable with a length of $\lambda /4$ and converts the unbalanced transmission line to a balanced one. The initial design creates two operating frequency bands at 2.215 to 2.533 and 3.896 to 4.471GHz. However, the second frequency band, i.e., 4.1GHz, is undesirable. Since this antenna is designed for 2.4GHz Wireless Local Area Network (WLAN) applications, the upper-frequency band at 4.1GHz can cause interference with other telecommunication systems in this band. Therefore, a U-shaped parasitic element next to the $\Gamma$ - shaped feed is employed to eliminate the disturbing frequency band in this design. The band removal is prompted by creating surface currents in opposite directions over the parasitic element and magnetic coupling between the $\Gamma$ - shaped feed and the parasitic element. The structure of the antenna is analyzed in the High-Frequency Structure Simulator (HFSS) and Computer Simulation Technology (CST), high-frequency simulator software. It is fabricated after extracting its electrical equivalent circuit in Advanced Design System (ADS) software. Finally, its radiation and scattering properties are tested and measured in the antenna laboratory. Laboratory results prove the elimination of the disturbing frequency band after utilizing the parasitic element. Then, the antenna has an operating band from 2.331 to 3.026GHz with a maximum gain of 8.05dB and a unidirectional radiation pattern. The overall dimensions of the proposed antenna are $40 \times55$ mm
²
, which is located on a ground plane with $100 \times100$ mm
²
dimensions. The proposed antenna can be redesigned for other bands such as Sub-6GHz for 5G applications at around 3.5GHz frequency by implementing an appropriate scaling mechanism. Therefore, using the proposed design as a feeding antenna to illuminate the reflecting metasurface is feasible.