Yagi Uda Antenna

Here all most all information regarding the antenna of yagis was described

1. PONDICHERRY UNIVERSITY DEPART. OF ELECTRONICS ENGINEERING SEMINAR By V.D.SRINIVAS (17304008)

2. TOPIC:- YAGI UDA ANTENNA

3. 1.INTRODUCTION 2.STRUCTURE 3.ELEMENTS 4.WORKING 5.DESIGN 6.CHARACTERISTICS 7 .DISADVANTAGES 8 .APPLICATIONS CONTENTS

4. INTRODUCTION In the 1926,Dr.Shintaro U da and Dr.Hidetsugu Yagi of the Tohoku imperial university invented a directional antenna system consisting of an array of coupled parallel diploes. Most high Gain Antennas. Yagi- Uda antenna is familiar as the commonest kind of triennial tv antenna to be found on the rooftops of houses It is usually used at frequencies between 30Mhz to 3Ghz to cover 40 to 60 Km.

5. STRUCTURE

6. 1.REFLECTOR Passive element It adds up the fields of driven element in the direction from reflector towards driven element 2.DRIVEN ELEMENT Active element It is a resonant half wave dipole or metallic rod The element was feeder ,supplied the charge 3 .DIRECTORS Passive element It can be one or more for increasing the directivity Size: 5% less than the Driven element ELEMENTS

7. YAGI-UDA ANTENNA Combining the effect of reflectors and directors elements, a highly directional antenna is obtained: the Yagi.

8. 1.Yagi Uda antenna is an array of a driven element and one or more parasitic elements 2.They are not connected directly to Tx line but Electrically coupled 3.Parasitic elements are arranged collinearly and parallel to each other elements 4.Current flow in the driven element induces voltage in parasitic elements. 5.The phase and current flows depends up on the spacing and reactance of the elements 6.Spacing are in order of 0.1 λ to 0.15 λ . WORKING

9. Conditions: 1.The REFLECTOR length is 5% more than the Driven element (≥ λ /2) ---- Leads to Inductive 2.The DIRECTOR length is 5% less than the Driven element (≤ λ /2) -----Leads to Capacitive

10. Design Reflector Length = 500/f( Mhz ) Driven element Length=475/f( Mhz ) Director Length =455/f( Mhz ) Feet Feet Feet

11. Radiation pattern

12. ADVANTAGES 1.Unidirectional beam of moderate Directivity 2.Gain of order of 8db or front to back ratio of about 20 db 3. Beam antenna—3 element config , 4. Super directivity or gain antenna due to its high gain and beam width per unit area of array 5. Further elements increase ---directivity increases 6.Construction is simple 7.Less cost and simple to feed

13. 1.Gain is not much more 2.Need more driven elements for longer distances Disadvantages 3.Bandwidth is Limited BROAD BAND PLANAR QUASI-YAGI ANTENNA FOR HIGHER B.W