International Journal of Mechanical Engineering and Technology (IJMET) Volume 8, Issue 7, July 2017, pp. 636 641, Article ID: IJMET_08_07_071 Available online at http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=8&itype=7 ISSN Print: 0976-6340 and ISSN Online: 0976-6359 IAEME Publication Scopus Indexed IMPROVEMENT OF YAGI UDA ANTENNA RADIATION PATTERN D.Naresh Kumar, G.Shravan Kumar, A.V.Paramkusam Department of Electronics and Communication Engineering, MLR Institute of Technology, Hyderabad, India M Ramesh Babu Institute of Aeronautical Engineering, Hyderabad, India ABSTRACT An antenna is a specialized transducer that converts radio-frequency (RF) fields into alternating current (AC) or vice-versa. And it transmits and receives electromagnetic waves. Antennas are working in radio broadcasting, peer to peer communication. Antennas are employees in air, under water and soil. The fundamental parameter of an antenna is radiation pattern, beam width, radiation power density, radiation intensity, directivity, antenna efficiency and gain. In this paper proposed to made an antenna to improvements the maximizing the output parameter like simulate the radiation pattern for symmetrically shaped antenna by using various methodologies such as reflecting surface wherever the losses in antennas was due to side lobes. Key words: EM waves, Polarization, Reflection. Cite this Article: D.Naresh Kumar, G.Shravan Kumar, A.V.Paramkusam and M Ramesh Babu, Improvement of Yagi UDA Antenna Radiation Pattern. International Journal of Mechanical Engineering and Technology, 8(7), 2017, pp. 636 641. http://www.iaeme.com/ijmet/issues.asp?jtype=ijmet&vtype=8&itype=7 1. INTRODUCTION A Yagi Uda antenna, commonly known as a Yagi antenna, is a directional antenna consisting of many array elements in a line [1,2]. It consists of an array of a n array of a dipole like one reflector, one driven elements and few parasitic elements. The basic geometry of a Yagi-uda antenna is Figure 1 Geometry of a Yagi-uda antenna http://www.iaeme.com/ijmet/index.asp 636 editor@iaeme.com
D.Naresh Kumar, G.Shravan Kumar, A.V.Paramkusam and M Ramesh Babu The length of the element is given as R is called as a reflector, and next element is feed element F, and the distance between the R and F is SR. The other elements are parasitic elements which are interacting by mutual coupling [2, 3]. An antenna radiation pattern or antenna pattern is defined as a mathematical function or a graphical representation of the radiation properties of the antenna as a function of space coordinates [4]. There can be field patterns (magnitude of the electric or magnetic field) or power patterns (square of the magnitude of the electric or magnetic field). The power pattern is usually plotted on a logarithmic scale or more commonly in decibels (db). Figure 2 Antenna Radiation Pattern Radiation patterns are conveniently represented in spherical coordinates [5]. Pattern: E(θ,φ). d A = r 2 sinθdθdφ. Azimuth: φ Elevation: π/2 θ. Radiation Pattern Lobes A radiation lobe is a portion of the radiation pattern bounded by regions of relatively weak radiation intensity. Main lobe Minor lobes Side lobes Back lobes Minor lobes usually represent radiation in undesired directions, and they should be minimized. Side lobes are normally the largest of the minor lobes. The level of minor lobes is usually expressed as a ratio of the power density, often termed the side lobe ratio or side lobe level. In most radar systems, low side lobe ratios are very important to minimize false target indications through the side lobes (e.g., -30 db). 2. EXPERIMENTAL SETUP When the yagi-uda antenna has two parasitic elements behind the active element, the antenna with only one parasitic element as reflector element is called as yagi-uda antenna. When the electrical length of the parasitic element is greater than the driven element [6]. http://www.iaeme.com/ijmet/index.asp 637 editor@iaeme.com
Improvement of Yagi UDA Antenna Radiation Pattern More than one parasitic element should be axially added in the front of the driven element and each one is called Director. The directors (D1 Dn) has not wired directly to the feed point it increases the directivity [7]. Number of elements, N = 15 Radius of each element, a = 0.0085 Figure 3 NBS Parameters for Yagi-Uda Antenna Director length, l 1 = l 2 = 0.424, l 3 = 0.420, l 4 = 0.407, l 5 = 0.403, l 6 = 0.398, l 7 = 0.394, l 8 to l 13 = 0.390 Reflector length, l 14 = 0.475 Feeder (Driven element) length, l 15 = 0.466 Spacing between directors = 0.308 Spacing between feeder & reflector = 0.2 The overall antenna length would be L = 4.2 The parameters (element lengths and spacing) are given in terms of wavelength [9]. Table 1 Measured Parameter DIRECTIVITY 14.2106 FBR OF E-PLANE 12.0779 FBR OF H-PLANE 12.081 3DB BEAM WIDTH OF E-PLANE 28.877 3DB BEAM WIDTH OF H-PLANE 30.526 3. THEORETICAL ANALYSIS There are so many ways to optimize the directivity and other antenna parameters. Trial And Error Method L1 = Length of reflector (159cm) = 0.4998λ L2 = Length of driven element (149cm) = 0.4684 λ L3 = Length of director (140cm) = 0.44.1 λ S1 = Spacing between reflector and driven element (44cm) =0.1383 λ S2 = Spacing between director and driven element (76cm) = 0.2389 λ http://www.iaeme.com/ijmet/index.asp 638 editor@iaeme.com
D.Naresh Kumar, G.Shravan Kumar, A.V.Paramkusam and M Ramesh Babu S3 = Spacing between directors (56cm) = 0.1760 λ Radius = 0.7cm = 0.0022 λ Frequency of operation = 94.3MHz. These outputs are for the following specifications of the yagi-uda array [8]: Spacing between reflector and feeder = 0.25 λ Number of reflectors = 1 Length of reflector = 0.5 λ Length of each director = 0.406 λ Spacing between adjacent directors = 0.34 λ Number of directors = 13 Number of exciters = 1 Length of feeder = 0.47 λ Total elements = 15 Radius of each wire = 0.003 λ Output value of directivity comes out to be 37 db. 4. RESULTS AND DISCUSSIONS Figure 4 Radiation pattern of antenna Figure 5 3D far field radiation pattern http://www.iaeme.com/ijmet/index.asp 639 editor@iaeme.com
Improvement of Yagi UDA Antenna Radiation Pattern The Electric field intensity and the Directivity are shown by the following curves. Figure 6 Electric field intensity Figure 7 Directivity (Polar representation) http://www.iaeme.com/ijmet/index.asp 640 editor@iaeme.com
D.Naresh Kumar, G.Shravan Kumar, A.V.Paramkusam and M Ramesh Babu Figure 8 directivity with respect to frequency 5. CONCLUSION It was thus found out that the results of Matlab implementation and theoretically calculated results are within the reasonable error limits. It was found that the final radiation possesses minimum radiation intensity in the back lobe (at angle of 180 degrees) and a maximum of lobe power is concentrated in the main lobe along the axis of the antenna. The directivity of the antenna first increases wrt frequency and then decreases as already shown. Both the simulations, that of Matlab and Feko, provide us with a verification of above mentioned result. REFERENCES [1] Antenna Theory, Analysis And Design By Constantine A. Balanis [2] Antenna Engineering Handbook (A.W. Love And T.S. Bird) [3] R.E. Collin, Antennas And Radio Wave Propagation [4] Robert S. Elliot, Antenna Theory And Design [5] Antenna Theory And Design By Stutzman Thiele [6] Modern Antenna Design By Thomas A. Milligan [7] Antenna And EM Modeling With Matlab By Sergey N. Makarov [8] Antenna Design And Visualization Using Matlab By Atef Z. Elsherbeni And Matthew J. Inman [9] A Novel Design And Evaluation of Rectangular Microstrip Antenna For Microwave Application, P. Naveen Kumar, Ravi.H.R, S.Chandramma, Kishan Singh, Nagaraj Kulkarni, S.N.Mulgi and P.V.Hungund, Volume 6, Issue 7, July (2015), pp. 01-07, International Journal of Electronics and Communication Engineering & Technology (IJECET) [10] Anila Dhingra, Dr. K. C. Roy, Dr. O. S. Lamba and Govind Kumar, A Photonic Substrate U-Slot Dual Band Patch Antenna For UWB Applications, International Journal of Electronics and Communication Engineering and Technology, 7(6), 2016, pp. 25 31. [11] IEEE Antennas and Propagation Magazine, Vol. 46, No. 5, October 2004. [12] Antennas And Propagation, IEEE Transactions On [Legacy, Pre - 1988] Volume 27, Issue 2, Mar 1979 Page(S):267 270 http://www.iaeme.com/ijmet/index.asp 641 editor@iaeme.com