A
OF kENVA
MULTIMEDIA UNIVERSlTY
FACULIY OF
ENGINEERING
AND TECHNOLOGy
2023/2024
UNIVERSTY EXAMINATIONS
FOR
SEMESTER EXAMINATION
FIRST
FIFTHYEAR
THE
BACHELOR
OF
DEGREE OF
SCIENCE IN ELECTRICAL
AND TELECOMM
ENGINEERING
ECE 2512:
DATE:
ANTENNA ENGINEERING
AND DESIGN
TIME: 2HOURS
17" APRIL 2024
INSTRUCTIONS:
BOOKLETPROVIDED.
QUESTION ONE |COMPULSORY AND ANY OTHER TWO QUESTIONS
ANSWER YOURQUESTIONS IN THE ANSWER
ANSWER
QUESTION ONE (THIRTY MARKS)
(a)Explain the following antenna
terms with the aid of equations
engineering
The directivity
(i)
(2Marks)
The radiated power density.
(2Marks)
(b) A microwave
link operating at a
frequency of
uses a 1Om diameter
antenna to transmit a
parabolic dish
signal. The signal is
received by a 2.5
dish antenna sited 20km
diameter
away. Given that the
parabolic
efficiencyof each antenna is
the;
50%, Find
3GHz
m
Gains of both antennas
()
(i)
(iv)
(V)
Half power beam
Effective Isotropic
(4 Marks)
width ofthe
receiving antenna.
Radiated Power
Free space
path loss
Power
(2Marks)
(1Mark)
(2 Marks)
received.
(2Marks)
Page 1 of
4
hoay
kad cond solage
ndinged
during
noved
at
wave
r
distance
a
mctres trDin
he
electronagnetle
of a radiated
power density
(e) The
mitting antenna is give
trarsmit
Wa
(r,
,
cos
20)sint
r0s0s0SS3
4
d)=
elsewhhere
(2 Marks)
Determine the:
ofthe
ensity
inten
Radiation
(0)
(iv)
Explain
Directivity
the
at
intensity
powerofthe
Radiated
r=
(2 Marks)
369, qp= 1809.
(3Marks)
mode.(2 Marks)
antenna.
nasystem in transmiting
loss
one source of power
QUESTION TWo
(a)
(6 Marks)
antenna,
1000,
point:
Iransmitting
ofCehe
t
Radiation
vd)
wave
(TWENTYMARKS)
oftthe following
the radiationcharacteristics
antenna
Omni-directional
types
of
antennas
(2 Marks)
Describe
()
(2 Marks)
radiator.
Isotropic
b) The magnetic vector
potential
of
an antenna
whose current
density
is
]
A/m²
is
given by:
A=lle-irdv
Starting from this expression
carrying a uniform
current
and considering
of
The magneticvector potential
()
The magnetic field
source must satisfy.
dipole of length dl
peak value I,, deriveexpressions for;
()
(c) For an electromagnetic
an infinitesimal
(7 Marks)
intensity.
(7 Marks)
wave to be radiated, describe the
necessary conditions that
the
(2 Marks)
QUESTION THREE (TWENTY
MARKS)
(a) An
antenna having a
current density J is
placed
homogeneous propagation
medium.
)
Derive an equation
vector potential
(ii)
Show that A is
fortheelectric
and a scalar
field
electric
in
an
isotropic,
intensity E in terms of
potential
uniform
and
the magnetie
(4 Marks)
related to Jb
J by an
inhomogeneous
differential
equation.
(6 Marks)
with
curtents
is
(h)A
phase shift
excited
dipoles
anos are of
c-esett
radians If the
of
using equal-anplitude
to
spacing equal
have uniform
dipoles
(2 Marks)
progressive
(2 Marks)
its
determine
Array lactar
of
Angular pasitions
skctuh the radiation
e
oUESTIONFOUR
a)A broadside
pattern
of the array
(3 Marks)
of array.
name the type
in (b) and
(TWENTY MARKS)
N half-wavelength dipoles.
antenna array consists
tsaay factor.
is
An antenna array
(b
2 Marks)
(2
nulls.
pattern
the radiation
of
made up
Given
magnitude and phase.
tendipoles
of
the
that
(6 Marks)
carrying currents
huve
dipoles
a
that
are cqual
spacing equal
unifoem
factor
of the antena.
The angles of the nulls
and mninor
The angles of the major
From the results of (b), sketch
()Explain
the principle
and elassify
of patterns
A current
of
peak value
field
intensity
an elevation
angle
The electric
and at
Mark)
3 Marks)
lo
the
radiation
pattern
of the array.
(4
as applied
multiplication
in
(2 Marks)
of
Amperes is applied to a wire antenna
given
Marks)
antenna design.
length
r metres
set up by the antenna at a distance
is
Marks)
(4
lobes
QUESTION FIVE (TWENTY MARKS)
(a)
in
to
(1
The artay
for
Derive an expression
caloulate
(0)
Marks)
(1
of the major lobe
Angular orientation
Angles
lobes
the minor
in
metres.
the far-field
by
E,=E
0
Derive expressions for the;
(2
Marks)
()
Radiated
(0)
Power radiated
(7Marks)
(üi)
Radiation resistance.
(3 Marks)
(b) The magnetic
power density
field
intensity set up by an antennathat is placed
in
free-space
at the point
(r=2000 m, 8= 0.25a, )
=n) is H-0.I mAT/m. Assuming that the antenna is loss
free,
calculate the radiated power if the antenna is:
Page 3 of 4
(4 Marks)
A dipole of
(1)
length
(4 Marks)
0.01A
A052 long dipole.
Page 4 of 4