Cork Institute of Technology
Bachelor of Engineering in Communications Systems - Award
(NFQ Level 7)
Summer 2007
Telecommunications Hardware
(Time: 2 Hours)
Answer any four (4) questions
[All questions are worth equal marks]
Values for constants;
Speed of light in a vacuum c = 2.998 x 108 m s-1
electron charge q = 1.602 x 10-19 C
Planck constant h = 6.625x 10-34 J
Boltzmann constant k = 1.381x 10-23 J K-1
Examiners: Mr. D. Denieffe
Dr. R. O’Dubhghaill
Dr. J. Barrett
Question 1 (Smith Chart)
Use the Z-Smith Chart provided for the following calculations:
(a) What is the load reflection coefficient if a 50Ω line is terminated with 35+j75Ω?
(4 marks)
(b) What is the load impedance if a load reflection coefficient of 0.35∠70° was measured
at the end of a 100Ω line? (4 marks)
(c) What is the input impedance of a 50Ω line at a point 0.09λ back from a load of 75-
j30Ω? (4 marks)
(d) What is the VSWR on a 75Ω line terminated with a 40+j60Ω load? (4 marks)
(e) A line with Z 01 = 50Ω is terminated with a 25-j60Ω load.
a. Use the Z-Smith Chart to find the locations of the maximum and minimum of
the standing wave (3 marks)
b. Find the impedance Z 02 of the λ/4 transformer, inserted at the voltage
maximum, that will match the line to the load (3 marks)
c. Find the impedance Z 02 of the λ/4 transformer, inserted at the voltage
minimum, that will match the line to the load (3 marks)
The following formulae may be found useful:
A
R
R
imumVoltageA
R
R
imumVoltageA
L
L
R
ZZZZZ
ZZ
ZZ
ZZ
010201)min(
01)max(
01
01
,
1
1
,
1
1
,
=
Γ+
Γ−
=
Γ−
Γ+
=
+
−
=Γ
