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S055 30/09/
THE MANCHESTER METROPOLITAN UNIVERSITY
FACULTY OF SCIENCE AND ENGINEERING
DEPARTMENT OF ENGINEERING AND TECHNOLOGY
SESSION 2003/
Examination for the BENG (HONS) ELECTRICAL AND ELECTRONIC ENGINEERING BENG (HONS) COMMUNICATION AND ELECTRONIC ENGINEERING BENG (HONS) COMPUTER AND ELECTRONIC ENGINEERING BENG (HONS) ELECTRONIC ENGINEERING (PART-TIME) YEAR/STAGE TWO
UNIT 64EE2071/64EE2105 : COMPUTER SYSTEMS & COMMUNICATION
ENGINEERING
Wednesday 26 May 2004
2.00 pm to 4.00 pm
Instructions to Candidates
Answer THREE questions.
ALL questions carry EQUAL marks.
Any calculator is permitted subject to Faculty Standard conditions
S055 07/01/04 continued
- (a) Explain briefly the meaning and significance of each of the following communication system terms:
(i) Signal to noise ratio (ii) Modem (iii) Bandwidth (iv) Channel capacity (v) Baudrate [10]
(b) The following block diagram shows a system in which a signal is received, amplified and sent to drive an 8Ω loudspeaker.
(i) If the input signal power level is 50 μW and it is subjected to a noise power level of 1μW, calculate the signal to noise ratio in dB at the input to the receiver. [2]
(ii) If the signal level is amplified by 65 dB as shown above and the output noise level rises to 0.1mW, calculate the signal to noise ratio in dB at the output of the receiver. [4]
(iii) Calculate the output signal voltage level present at the loudspeaker. [2]
(iv) Given that the amplifier in the above system has a maximum input level of 1mW and a sensitivity of 10pW, calculate its dynamic range. [2]
Amplifier gain 65 dB
input output
S055 07/01/04 continued
- (a) State three advantages of using digital rather than analog signalling in a communications system. [3]
(b) Explain briefly the meaning and significance of each of the following data communication terms.
(i) Bit synchronisation
(ii) Bit error rate
(iii) Data modulation (line) codes
(iv) Quantisation [8]
(c) State Nyquists sampling Theorem. [2]
(d) 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 data rate using:
(i) 4 bit encoding (ii) 8 bit encoding [7]
- (a) State four principal benefits of using optical fibre as the physical transmission medium in a communications system. [4]
(b) Explain, with the aid of suitable diagrams, the basic operating principle of an optical communications link, outlining the principal features of the different sources, fibre types and detectors that can be used. [8]
(c) The distance between the transmitter and receiver in an optical fibre communication link is 10 km. The transmission path comprises a number of spliced fibre links, each of which has a maximum length of 3 km. The attenuation of the fibre is 2.5 dB/km, the average splice loss is 0.1 dB per splice and the coupling loss at each end of the link is 0.5dB. The launched power from an LED source into the fibre is –11dBm and the receiver sensitivity is -45dBm.
Perform an optical power budget for the system by evaluating:-
(i) the total allowed link loss for correct performance, (ii) the actual link loss due to the constituent link components, (iii) the system safety margin. [8]
S055 30/09/
- (a) Describe, with the aid of suitable diagrams, the basic principle of mobile (radio) telephony. In particular explain the reasons for the cellular architecture and the need for frequency re-use. [10]
(b) A microwave link is set up over a distance of 25km and both the transmit and receive ends have a common aerial with a gain of 50dB. The system operates at a wavelength of 0.05m. The signal power at the transmitting station (i.e. prior to the transmitting aerial gain) is 250W. The combined noise power at the receiver is 100nW.
(Assume the Aerial Receiving Aperture = A = G λ 2 / 4 π )
Determine: (i) the Effective Isotropic Radiated Power (EIRP) in Watts radiated from the transmitting aerial. [2]
(ii) the power density in (W/m^2 ) incident on the receiving aerial. [3]
(iii) the signal to noise ration in dB at the receiver. [5]
END
