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Date & Duration of Exam: January 2011, 2 hours Course Title: Design of Electronic Systems Course Code: ELEE1129

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EXAMINATION PAPER: ACADEMIC SECSSION 2010/2011Campus Medway

School Engineering

Department Engineering Systems

Programme MSc Engineer Suite

Level 7

COURSE TITLE Design of Electronic Systems

COURSE CODE ELEE1129

Date and Duration Jan 2011, 2 hours

(including Reading time)

Paper Set by Dr P Callaghan

INSTRUCTIONS TO CANDIDATES

&

INFORMATION FOR INVILGILATORS

The attention of the students is directed to the instructions printed on the answer book

Answer any THREE of the following four Questions

All Questions carry equal marks

Duration: 2 Hours

Graph Paper will be provided

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Date & Duration of Exam: January 2011, 2 hours Course Title: Design of Electronic Systems Course Code: ELEE1129

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Q1 .(a) What are the three key parameters that describe the discharge of an idealbattery?

[6 marks]

(b) A 50W portable appliance is required to operate continually for 18 hours from a12V battery supply. Assuming ideal battery characteristics which, if any, of the

following may provide a solution? How would they be connected?

(i) 6 batteries each 1.5V, 10Ah

(ii) 6kg of a 12V battery with an energy density of 170 Wh/kg

(iii) 2 12V batteries each having a 40Ah capacity but rated at C/10[8 marks]

(c) Four Zinc Chloride (ZnC) cells are required to power for 35 hours an applicationthat requires a minimum of 4.4V to operate and draws 5 mA current. Each cell is ratedat 300 mAh but their potential falls from 1.5V initially to 0.9V when fully discharged.

(i) Show by calculation whether this battery type can meet this requirement.(ii) It is proposed to use Nickel Cadmium (NiCd) cells as a rechargeable option. If thecapacity of each cell is 200 mAh is this possible?(iii) Comment on your findings in general under what circumstances, if any, wouldthe NiCd provide an alternative to the ZnC battery?

[6 marks]

(d) Nickel Metal Hydride (NiMH) batteries were developed to overcome limitationsof NiCd batteries. Discuss the advantages and disadvantages of NiMH againstNiCd

[5 marks]

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Date & Duration of Exam: January 2011, 2 hours Course Title: Design of Electronic Systems Course Code: ELEE1129

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Q2 . (a) Sketch the volts current characteristic for a typical Fuel Cell[6 marks]

(b) A 150W, 6V device is to be powered by a Fuel Cell. Two types of Fuel Cell areavailable. The first type uses a low profile but runs at a high current density, whilst a

bulker design is available but has a much higher density. Estimate the number of FuelCells needed and the overall mass required for each type.

[ 6 marks](c) What type of Fuel Cell would meet the requirement above?

[3 marks]

(d) The 150W, 6V device is to have a SuperCapacitor back-up supply to ensure itcontinues operation for at least 5 minutes. The only SuperCapacitor has the followingparameters

Capacitance: 2000FInternal Resistance 0.001 Maximum operating voltage: 2.2V

If the device will operate down to 4.5 V determine a suitable SuperCapacitor Stack that will meet this requirement. State any assumptions.

[10 marks]

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Date & Duration of Exam: January 2011, 2 hours Course Title: Design of Electronic Systems Course Code: ELEE1129

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Q3 . (a) What is Electromagnetic Compatibility (EMC) and what are the twoprincipal aspects to EMC?

[6 marks]

(b) Sketch a TEM cell with suitable annotations and describe its application forEMC.

[9 marks]

(c) A traditional design approach for an automotive stereo system driving 120W (60Wper channel) into 6 speakers is to use the chassis as a ground terminal. Here there is asingle supply lead to the head unit and 4 single wire leads from the head unit to thespeakers. The head unit is grounded by a separate wire routed to the nearest chassispoint 400mm away. This is illustrated in Fig. Q3

Fig Q3: Wiring Schematic for car audio system

(i) Discuss any problems this might give with regards to EMC and propose animproved wiring scheme.(ii) It is proposed to use active speakers that the power amplifier for each channelis incorporated to the speaker module. This reduces the current drawn by the head unit(reducing heat dissipation in the console). Does this improve or worsen the EMCissues?(iii) For an active speaker system discuss if there are any alternative connectionapproaches to improve EMC?

[10 marks]

Head Unit

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Date & Duration of Exam: January 2011, 2 hours Course Title: Design of Electronic Systems Course Code: ELEE1129

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Q4 . (a) The three common IC technologies are TTL, ECL and CMOS. Whichtechnology is preferred for each of the following applications and why:

(i) Low power(ii) High Speed(iii) Low Cost

(iv) Ease of handling[8 marks]

(b) In designing a low power system it is argued that power consumption is optimisedat the system design stage rather than at the architecture or circuit design stages.Discuss why this is the best approach. In your answer give 5 design factors that areinfluenced by the system design that can lead to significant reduction in powerconsumption.

[10 marks]

(c) It is proposed to replace a microprocessor having 300,000 transistors that operatesat 2MHz on 3.3V with a smaller device having only 150,000 transistors. If the newmicroprocessor requires a 5V supply and must run at 10MHz to perform the samefunction calculate if there will be a saving in power.

[7 marks]