investigation and analysis of quasi yagi antenna for wireless applications

Abstract

Nowadays, the huge demand for high gain, compact size, broadband, and low profile antenna, especially in mobile communication, phased array, portable direction finding system, radio communication, radar and RFID tags etc, is increasing rapidly. The printed Quasi Yagi antenna has received huge interest for research because it fulfills all aforementioned requirements. A Yagi-Uda antenna is a directional antenna but has limited bandwidth. To achieve the high gain, broad bandwidth and compactness, the Yagi-Uda antenna can be designed by changing its original structure w.r.t different feed structures, element shapes and different dielectric constant material by printed technology. These new structures formed due to different feed structures and element shapes are not exactly the Yagi-Uda antennas but they can be called printed Quasi Yagi antennas. newline newlineIn this thesis, low cost printed Quasi Yagi antennas are designed for high gain and broadband applications, which operate at 2.4 GHz. To feed the Quasi Yagi antennas, a simple microstrip feed line is designed which provides impedance matching between coaxial input source and driven element. The proposed Quasi Yagi antennas are fabricated on the low cost Glass Epoxy FR4 substrate of thickness 1.6mm, dielectric constant of 4.4, and loss tangent of 0.02. The measured results are well matched with the simulated results. Here three different types of designs are proposed, 1) Quasi Yagi antenna using dipole, 2) Quasi Yagi antenna using bowtie, and 3) Quasi Yagi antenna using bowtie driven with curved shape directors. To increase the gain of the antenna in the desired direction, it is designed with 3-elements, 4-elements and 5-elements that are presented in the thesis. newline newlineThe Quasi Yagi antenna using Dipole (5-elements DQY) obtained the bandwidth of 340 MHz (2.23 - 2.57 GHz) for S11 lt -10 dB, the gain about 6.0 - 7.52 dB, and VSWR lt 2 for the entire frequency band. Additionally, it has front-to-back ratio gt 13 dB and cross- polarization level of lt -29 dB at 2.4 GHz. The overall dime