The far-field pattern of a simple dipole antenna of length L may be approximated by the equation cos (3 cos 0) - cos 3/

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The Far Field Pattern Of A Simple Dipole Antenna Of Length L May Be Approximated By The Equation Cos 3 Cos 0 Cos 3 1 (710.54 KiB) Viewed 43 times

The far-field pattern of a simple dipole antenna of length L may be approximated by the equation cos (3 cos 0) - cos 3/ E(0) = (4) sin 0 where 3 = 2 radians/m. This gives the electric field E at angle from a line parallel to the antenna. The key question is: what is the best length of the dipole antenna L so as to direct the energy in the most efficient way? So, we need to determine the radiation pattern, and particularly the power P(0) = E²(0). To do this, plot the power P versus angle 0 for L = . Note that there may be difficulties when sin = 0, and you will need to evaluate at a small, but non-zero, angle. The type of plot you should obtain for this part is similar to that shown in Figure 4, except that the length of the dipole antenna is different. Note that this is the radiation pattern only, and you cannot infer anything from the magnitude of the power values, only the shape of the pattern. Dipole Radiation Power (Relative) 0 1 330 30 300 60 270 240 0.8 0.6 0.4 p/2 120 90 210 150 180 Dipole length L = 1.4A Figure 4: Power field pattern for dipole for L=1.4 X m.