ElectroMagnetic Theory Concepts & Solved Numericals

9) A Hertzian dipole at the origin in free space has dl = 20 cm and I = 10 cos2π10 7 t A, find |E θs | at the distant point (100, 0, 0). SOLUTION: λ = c / f = ( 3 x 108 ) / (107) = 30 m At (100, 0, 0), r = 100 m & θ = π / 2 10) A 2-A source operating at 300 MHz feeds a Hertzian dipole of length 5 mm situated at the origin. Find E s and H s at (10, 30°, 90°). SOLUTION:                    λ = c / f = (3 x 108) / (3 x 108) = 1m                    β = 2π / λ = 2π                   At r = 10, θ = 30 o , φ = 90 o                    λ = 120π = 377 m                    E θs = η H φs = 94.25 mV/m 11) An antenna can be modelled as an electric dipole of length 5 m at 3 MHz. Find the radiation resistance of...

1) An electric field strength of 10 µV/m is to be measured at an observation point θ = π/2, 500 km from a λ/4 monopole antenna operating in air at 50 MHz. (a) What is the length of the dipole? (b) Calculate the current that must be fed to the antenna. (c) Find the average power radiated by the antenna. (d) If a transmission line with Z o = 75 Ω is connected to the antenna, determine the standing wave ratio. SOLUTION: a) The wavelength λ = c / f =( 3 x 108) / (50 x 106) = 6 cm.                              Length Of The Dipole (l) = λ/4 = 6 / 4 = 1.5 cm. b) c) R rad = 73 Ω (For λ/2 (Half Wave) Dipole Antenna) R rad = 36.56 Ω (For λ/4 Monopole Antenna) d) Standing Wave ratio (S)      Z L = 73 + j42.5 (For Half wave dipole Antenna)      Z L = 36.5 + j21.25 (For λ/4 Monopole Antenna) 2) Calculate the directivity of a) The Her...