Order Description

Analogue Communications and Propagation – Coursework assignment 1
Each of the coursework assignments are weighted at 10% of your total mark for the
module. The deadline for this submission to the School Office (Chichester 1) is 16.00h,
Thursday week 7.
Assignment brief
Your report should consist of a maximum of 2000 words, equivalent to about 4-5 pages of
combined text, calculations and diagrams, as indicated in the description below. Be careful
to address all of the questions in your submission.
Part 1 (20 marks)
Sketch the electric and magnetic field patterns associated with a two wire transmission line
and a coaxial transmission line. What is the most significant difference between them and
what consequences does this have when considering which one to choose for a particular
application?
Part 2 (50 marks)
(i) Explain the physical meaning of the L, C, R and G parameters used to model the
behaviour of transmission lines. Sketch the circuit for this model.
(ii) Design a λ/4 transformer to match a 50 Ω coaxial cable to a 75 Ω coaxial cable,
working at a frequency of 2 GHz. You should specify all the dimensions of the matching
section. Take the phase velocity to be 3 x 108
m/s, the relative dielectric constant of the
insulator (εr) to be 2.5 and the outer diameter to be 10 mm.
(iii) Sketch your design.
(iv) What is the magnitude of the reflection coefficient at the 75 Ω cable interface with
the matching section and the corresponding VSWR?
(v) What are the inductance per unit length and the capacitance per unit length for the
matching section you have designed?
Take µ0 =4π x 10-7 H/m; µr =1 and ε0 = 8.85 x 10-12 F/m
Part 3 (30 marks)
Describe briefly the additional matching technique you would need to use if the 75 Ω cable
was replaced with a reactive load. You may use a sketch to illustrate your answer.
If the impedance of this reactive load is 75 – j40 Ω calculate:
(i) a design for a this additional matching element, specifying its dimensions and
characteristics.
(ii) the magnitude and phase of the reflection coefficient and the corresponding VSWR.