ElectroMagnetic Theory Concepts & Solved Numericals

19) At the far field, an antenna produces Calculate the directive gain and the directivity of the antenna? SOLUTION: 20) For a thin dipole λ/16 long, find the a) Directive gain b) Directivity c) Effective area d) Radiation resistance SOLUTION: a) On substituting we get, G φ = 1.5 sin 2 θ b) Directivity , D = G φ, max = 1.5 c) Effective Area , A e = (λ 2 / 4π) G φ = (1.5 λ 2 sin 2 θ) / 4π d) Radiation Resistance R rad

16) Sketch the normalized E-field and H-field patterns for a. A half-wave dipole b. A quarter-wave monopole. SOLUTION: a) b) The same as for λ/2 dipole except that the fields are zero for θ > π/2 as shown: 17) In free space, an antenna has a far zone field given by Determine the radiated power? SOLUTION: 18) At the far field, the electric field produced by antenna is Sketch the vertical pattern of the antenna. Your plot should include as many points as possible. SOLUTION:        f(θ) = | cosθ cosφ |             For the vertical pattern, φ = 0 which means,                        f(θ) = | cosθ | which is sketched below