HOMEWORK ASSIGNMENT #3 SUBJECT: EECE 5693 – EM Devices
1) On a small dipole antenna with total length l ( l 0.2 ) the current distribution can be approximated by I I0 1 2 z l, as shown below.
A
z
r l
II012z l
a) Find the radiated electric and magnetic fields (Far-Fields). Carefully explain their behaviors and the physics behind them,
b) Determine the radiation intensity U(,),
c) Evaluate the total radiated power Pr ,
d) Derive the directivity of antenna D,. What is Dm (maximum directivity) in dB.
e) Plot D, using a computer program, Explain all the details of the curve carefully (gain, side-
lobes, beamwidth, etc.). In which direction the antenna can radiate maximally? Can we send the information to point A in space? What do you recommend to send the power to point A?
f) Obtain the Half-Power Beamwidth of antenna from the curve for D , ,
g) What is the relation between D, and power pattern ( F,2 )
h) What is the beam solid angel?
i) What is the relation between the directivity and gain of an antenna? How do you define the efficiency of antenna?