YAGI-UDA ANTENNA

Yagi-Uda Antenna:

                                       It's the most simple type of antenna which basically uses the dipole antenna as its fundamental working element . It's an directional beam creating antenna which is mostly used in TV channel operations in olden days and even today in some parts of India.

Why The Name Yagi-Uda:

                                                   Basically this antenna was designed and developed by two scientists of japan named "Yagi and Uda " so in the honor of them it was named so . Here it should be noted that it has not got any technical meaning in it . most of antenna's were named on the basis of its inventor .

What is Use Of Yagi - Uda Antenna :

                                                                      AS we know that "dipole "  antenna is roughly an Omni directional antenna which radiate the electromagnetic waves in nearly 360 degree except at some points as illustrated in the below figure .

"dipole antenna "

                                                                   But the question here is that what is the necessary of this Yagi - uda  antenna to understand this we should first know some basic things about antenna Directivity . The problem with the dipole antenna is that as stated earlier it generates the radiation in all directions but it will cover a very small distance , which can't be tolerated in far distance communications like TV transmissions. 

                                                                Here the yagi-uda antenna came into picture which is capable of generating such an "radiation pattern which will cover a large distance ". That means the Directivity of the antenna is more .

Why the reflectors and directors are used in it :

                                                                                                Before we come to this point why these are used . we should know that a "inductor" basically "lag's the current in it " and the "capacitor lead's the current through it ". 

                                                 Now as we can see in figure that a dipole antenna is placed at the middle point . and an reflector is placed on left side of dipole and an directors are placed on right side of dipole antenna . here it is to be noted that we want to create the directive radiation on right hand side of the dipole . 

"Yagi-Uda Antenna "

             The" size of the reflector is made a little longer as compared to dipole antenna and that of director is made a little shorter why ?????.

                                                                             The reason behind is that "When an electromagnetic wave is created in both the directions we want the waves on right side only so we will keep an element longer than the length of dipole antenna which will be acting as the "inductor " and it will lag the current through it . so here when wave travel from dipole slit to reflector slit there will be change in the phase of electromagnetic wave so in order to correct that one the reflector acts as an inductor . 

                                                                                

                                           NOW coming to the directors as their name itself indicates "They are used to provide the direction to the electromagnetic waves " . as we know a smaller element will act as capacitor and the property of capacitor is that it tends to "lead the current through it " thus it will confine the radiation in one direction and also gives more strength to the radiation thus covering a larger distance . Here it should be noted that the length of directors could be kept in their decreasing order or as a same length as shown in figure .