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Ph.D.
(Engineering & Technology)
INVESTIGATION AND ANALYSIS OF QUASI YAGI ANTENNA
FOR WIRELESS APPLICATIONS

Ph.D. Scholar : Dalvadi Pravin Jagdishbhai
Research Supervisor : Dr. Amrut N. Patel

Regi. No.: 18276351002
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.
In 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.
The Quasi Yagi antenna using Dipole (5-elements DQY) obtained the bandwidth of 340
MHz (2.23 - 2.57 GHz) for S11 < -10 dB, the gain about 6.0 - 7.52 dB, and VSWR < 2 for the
entire frequency band. Additionally, it has front-to-back ratio > 13 dB and cross-
polarization level of < -29 dB at 2.4 GHz. The overall dimension of 5-elements DQY
antenna is 65 mm × 70 mm × 1.6 mm (0.52λ × 0.56λ × 0.0128 λ). The DQY (3-elements,
4-elements and 5-elements) obtained the gain of 6.03 dB, 6.44 dB and 7.04 dB, and 20%,
15% and 14% the bandwidth respectively.

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