Analysis of the Effects of Reflector and Director on a Half Wave Dipole’s Directivity Prachi Jain Department of Electronics and Communication Gyan Ganga Institute of Technology and Sciences Jabalpur Zohaib Hasan Department of Electronics and Communication Gyan Ganga Institute of Technology and Sciences Jabalpur Abstract- The rapid advancements in the field of antenna and microwave design has opened many new dimensions. This is only possible because of the developments of various highly efficient simulation tools that produce precise and truthful results. With the advancements in antenna design, complexity of the design is also increased. Designers sometimes ignore the simplicity and beauty of the old antenna designs. This paper is an attempt to re-assert the theory proved by H.Yagi and S. Uda in 1926 using modern tools. CST microwave studio is used for simulation of a 2 GHz half-wave dipole with a reflector and director in its vicinity. Such a high frequency of 2 GHz is used for the simulation because these are used a lot nowadays for various applications. The advantages of the design of Yagi-Uda antenna can be exploited in various modern antenna and their applications. Keywords: Half-wave dipole; wave reflector; wave director; directivity. I. INTRODUCTION There are numerous applications where the need of a directional antenna comes into picture. Since more than 100 year there have been researches in the direction of making an antenna directional. One of the oldest methods to make an antenna directional is make a parasitic array out of it. In 1926, H.Yagi and S.Uda invented a parasitic array that successfully increased the directivity and bandwidth of a simple half-wave dipole [1]. A rod of equal or slightly longer length is placed quarter wave away from a half wavelength long vertical antenna. The current induced in it will be in phase or lag behind. This effect will make this rod a ‘wave reflector’. If another rod of length less than quarter wavelength is placed quarter wave away on the other side of this arrangement, the current induced in this rod will lead. This effect will make this rod a ‘wave director’. Reflector will reflect away the signal that comes out of the driven element. On the other hand, director pulls the electromagnetic wave towards it causing the radiation pattern to be single directional towards the director. To make the radiation pattern more directional one can put more directors on the same axis and plane. On the contrary only a single reflector is sufficient to cause directive action of radio wave. Figure 1. 7-element Yagi Uda antenna II. ANTENNA DESIGN Figure 2. Antenna Dimensions Operating frequency is 2 GHz. Hence wavelength is 147.78 mm. Driven element is kept 0.475 times of wavelength because only 95% of the dipole antenna radiates. Reflector length is 0.55λ and director length is 0.45λ. Separation between driven element and driver is 0.35λ and that between driven element and driver is also 0.35λ. Input impedance of a half wave dipole is 73Ω. Vol. 5 Issue 04, April-2016 International Journal of Engineering Research & Technology (IJERT) ISSN: 2278-0181 http://www.ijert.org IJERTV5IS040485 (This work is licensed under a Creative Commons Attribution 4.0 International License.) Published by : 313