COMM.RF.710 Antenna Design
Homework I, deadline is given on Moodle
1. Familiarize yourself with the following article, esp. sections 1.-2. The article describes
several features of EM waves that are relevant in antenna engineering in addition to
discussing boundaries of near eld and far eld regions.
On radiating-zone boundaries of short, λ/2, and λ dipoles Laybros, S. and Combes,
P.F. Antennas and Propagation Magazine Oct. 2004. Available on ieeexplore.
Give a precise and concise overview of the dierent criteria given in text. Prepare
also an example which allows you to compare all the criteria. (3.5 p.)
2. Electric eld of an electric dipole antenna that is aligned with the z axis is
E(r) = −
where a =
IL 2 ηk uθ (a + a2 + a3 ) sin θ + 2ur (a2 + a3 ) cos θ e−jkr ,
4π
1
. This formula is valid at all distances.
jkr
(a) Explain the terms in the formula i.e. what do they stand for?
(b) Determine the fareld approximation for the Eeld.
(c) How big error is made if we use fareld approximation (derived in (b)) at
distance λ from the dipole? Determine the error on the xy plane.
(In total 1.5 p.)
3. Consider a circular loop antenna with radius 0.5 m and made of copper wire of
diameter 3.264 mm. Find at 20 Mhz+n*1 MHz (where n is the last digit of your
student number, i.e. 23456n)
(a) radiation resistance,
(b) ohmic resistance,
(c) radiation eciency, and
(d) input reactance.
Hint: Balanis sections 5.25.4.
(In total 1 p.)