Field and Wave Electromagnetics 2nd Edition by David Cheng

Exercise 80

A time-harmonic uniform current I 0 cos t flows in a small circular loop of radius b ( ) lying in the xy -plane.
a) Find the radiation resistance R r of the magnetic dipole.
b) Obtain an expression for its radiation efficiency n r if the loop is made of copper wire of radius a ,
c) Calculate R r and n f for f = 1 (MHz), b = 50 (cm), and a = 3 (mm).
d) Rework part (c) if the loop has ten closely wound insulated turns.