Question

Solve the following: a. Compare the current required to radiate 10W from a Hertzian dipole of length 0.12 and a current loop of radius 0.12. b. An isotropic antenna is radiating in free space. At a distance of 100m the antenna the field measured is 1V/m. i) Find the power density at this location; ii) Determine the total power radiated by the antenna

Answer 1

Given that 8- Compok the current required to radiate low from a Hertzian dipake of length oil and a current loop of radius 0.1. Sol:a) The radiation resistance of a testzian dipok id, Rrad = 8010² (2) = 80772 (0:14) 7,89572 The power radiated by Hertzian dipok ix, Prad = I2 Road 10 - 3 IC 7.8957) Id : 2x 1067 7.8957 = 20 7,8957 Io = 1.5915 Thus, the Current required to radiate low from a thartziarz dipole is, Io = 1.5915 A The radiation resistance of loop antenna is, Rrad = 300798² : 32077“ (TV2) Csince, 3 =1712) = 32077"GTR274)

= 32071"( 2 (0.1434) 14 = 32077660.134 - 30.764512 The power radiated by loop antanna is, Prad = 1 / 2 1 Prad lo = . I3 (30-7645) Ia = 2x10 30.7645 LO 30.7645 Io = 0.80 63 Thus, the Current required to radiate low from a Hilzian dipole is, Io =0.8063 A Thus, the current required is more in care in case of Hertzian dipde when compared to loop antoena to radiate the same power low (b) The field masured at a distance reloom of an isotropic antenna is, E: IV (1) The power density at this location is, Pa E2 no

= (12 1207 P = 2.7m3/m2 (1) The total power radiated by the cantar Wr=477 ¢ - (100)2 = 166.67w GO W