advertisement

Drill 8.5: A small-loop antenna of radius /100 is excited by a current i = 1 cos(2 × 109t)A. (a) Determine the maximum power density radiated by this antenna at a distance of 100 m. (b) What is the time-averaged power density at the point P(100,/4,/2)? (c) Find the radiation resistance. Solution: We have (8.63): Pmax 2 o2 I o2 S 2 2 32o 2 r 2 c 3 108 m / s Here, 0.3m f 109 / s Pmax Pmax 2 109 4 10 7 H 1A 0.3m 2 2 1 32 120 s m 100 0.3m 100m nW 18.4 2 m nW P r , , Pmax sin 2 18.4 2 m 2 nW 2 sin 9.2 2 m 4 2 (8.65) Rrad 2 2 S 4 100 320 2 320 3.1m 2 4 Written by Stuart M. Wentworth. Copyright John Wiley and Sons 2007