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S143 01/10/
THE MANCHESTER METROPOLITAN UNIVERSITY
FACULTY OF SCIENCE AND ENGINEERING
DEPARTMENT OF ENGINEERING AND TECHNOLOGY
SESSION 2003/
Examination for the BSc (HONS) MEDIA TECHNOLOGY BSc (HONS) INFORMATION TECHNOLOGY BSc (HONS) COMPUTER AND NETWORK TECHNOLOGY YEAR/STAGE ONE BSc COMBINED HONOURS YEAR/STAGE TWO
UNIT 64EE1047 : ELECTRICAL TECHNOLOGY AND COMMUNICATION PRINCIPLES
Thursday 29 April 2004
2.00 pm to 5.00 pm
Instructions to Candidates
Attempt any FIVE questions.
All questions carry equal marks. Breakdown of marks for each question are shown in parentheses.
A supplementary answer sheet is provided for answering question 5(b).
continued
- (a) Explain briefly why relays are often used in preference to normal switches in circuits that pass large electrical currents. Describe briefly how the relay works, and state ONE example of a circuit that normally includes a relay. [6]
(b) Figure Q1(a) shows the components involved in connecting a battery to a high-current load using a relay.
Figure Q1(a)
Draw a diagram of the circuit, showing the connections between the various components and using the normal rectangular layout of such diagrams. Explain briefly how the circuit works. [9]
(c) Figure Q1(b) shows the physical shapes of the components of Figure Q1(a), where the lamp represents the high-current load. Redraw these components and add lines to show the wire connections required to make the circuit described above in part (b). [5]
Figure Q1(b)
battery coil
switch relay
load
switch
relay
battery
load
continued
- (a) Describe, with the aid of suitable diagrams, the key characteristics of the following fundamental types of signal.
(i) Analog signal. (ii) Digital signal. [8]
(b) The following figure shows a sinusoidal signal waveform labelled A in the time domain. Using the supplementary answer sheet , clearly mark on the diagram:
(i) a sinusoidal signal labelled B, with half the peak amplitude, twice the frequency and no phase shift relative to signal A (ii) a sinusoidal signal labelled C, with the same amplitude and frequency and a phase shift of 90 o^ (i.e. π/2 radians) relative to A [4]
-1.
-0.
0
1
(c) The following block diagram shows a system in which a signal is received, amplified and the output is used to drive a loudspeaker.
(i) If the input signal power level is 50 μ W and is subjected to a noise power level of 1μ W , calculate the signal to noise ratio in dB at the input to the receiver. [3]
(ii) If the signal level is amplified by 50 dB and the output noise level rises to 0.1mW, calculate the signal to noise ratio in dB at the output of the receiver. [5]
Amplifier gain 50 dB input output
A
continued
- (a) Explain briefly the meaning and significance of each of the following communication system terms:
(i) Space noise; (ii) Binary signalling; (iii) Bandwidth; (iv) Channel capacity; (v) Signal to noise ratio; (vi) Amplitude modulation (AM). [12]
(b) Describe the basic principle of operation of an optical fibre communication system. State TWO intrinsic advantages that optical fibre has compared with metallic conductors such as twisted pair wire. [8]
- (a) Discuss the fundamental differences between a baseband communication system and a broadband communication system. Give ONE example of each type of system. [6]
(b) Explain how pulse code modulation (PCM) operates, showing how a typical analog input signal would be digitized using this method. [8]
(c) A ± 10 Volt video signal with a maximum frequency content of 200KHz is to be digitally encoded. Assuming uniform quantisation levels, evaluate the maximum quantisation error and the minimum channel datarate using 4 bit encoding. [6]
Supplementary Answer Sheet for Q5. Candidate Number _____________
-1.
-0.
0
1
A
