Overview of Coursework 1 for Teaching Block 1
Coursework 1 described in this document is divided into two sections.
The first section (Section 1 - Investigation of analogue circuits) has four experiments designed to reinforce
the theories covered during the lectures and PBL sessions. The total marks of Section 1 are 45 marks.
The second section (Section 2 - Project to design an ultrasonic signal amplifier) is a project in which you will
be required to design a circuit to meet a given specification and requirements. The total marks of Section 2
are 55 marks.
Working practices
You should work individually and complete the coursework independently.
Although the Multisim simulation software can be used for the coursework, the LTspice simulator is strongly
recommended because this simulator is free and is therefore not restricted by license issues. LTspice has
been selected as the main tool to be used throughout the module, and it will be used in other modules too.
All work including circuit analysis and design, theoretical calculation (prediction), simulation analysis and
evaluation and lab experiments should be shown in the report. You are encouraged to seek advice and
obtain feedback on what you have already done at any, and preferably on several occasions.
The marks and the feedback on the report will be given within 20 working days after the deadline of
submission.
Please submit ONLY ONE PDF report which covers all your work. All simulation source files should be
uploaded along with the report. The source files should be ready for simulation.
Please be warned that the plagiarism detection software will be used on your submission.
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Section 1 – Investigation of Analogue Circuits
Experiment 1: Verification of Circuit Analysis Methods
The purpose of this experiment is to verify the classical circuit analysis approaches, which include the mesh
analysis method and the nodal analysis method, using the LTspice simulator. The circuit diagram is shown in
Fig. 1 below.
5 4
R R
1 2
12 V E R 10 E 10 V
1 3 2
Fig. 1 Circuit diagram for Experiment 1
Tasks for Experiment 1:
(1) Write the mesh current equations and determine the value and the direction of the mesh currents.
Theoretically calculate the current through and the voltage across each resistor.
(2) Write the nodal voltage equations and determine the value and the polarity of the nodal voltages.
Theoretically calculate the current through and the voltage across each resistor.
(3) Build up the circuit in the LTspice simulator and complete the simulation analysis; capture the
waveforms of the current through and the voltage across each resistor.
(4) Compare the theoretical prediction with the simulation results.
Evidence required in your report for the assessment of Experiment 1:
Title of your investigation.
Description of your investigation (what did you do).
The full working of determining the voltages across and the currents through each resistor,
respectively using the mesh analysis and the nodal analysis methods should be presented. You can
write down your working on a piece of paper and include the photo of the working in your
coursework report.
A circuit diagram built up in the LTspice simulator.
Captured waveforms labelled with all relevant parameters.
The results obtained using the mesh analysis method, the nodal analysis method and the simulator
should agree with each other. If not, please find out the reasons and correct mistakes (if there are
any) in your theoretical calculation and/or in the simulation.
Full source files are ready for simulation (submitted along with the report).
Marking scheme for Experiment 1 [Total 10 marks]:
The mesh current equations, and the values and the directions of the mesh currents are correct.
[2 marks]
The nodal voltage equations, and the values and the polarities of the nodal voltages are correct.
[2 marks]
The value and the direction of the current through each resistor and the value and the polarity of the
voltage across each resistor are correct. [2 marks]
The circuit is correctly built up in LTspice and the simulation results are correct. [2 marks]
The results obtained using the three methods agree with each other. If not, proper analysis and
discussions should be provided. [2 marks]
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Experiment 2: Verification of the Thevenin’s Theorem
The purpose of this experiment is to verify Thevenin’s theorem, using the LTspice simulator. Thevenin’s
theorem can significantly simplify the analysis of a circuit and thus has been widely used in practice. The
most important steps of obtaining the Thevenin’s equivalent circuit of an analogue circuit are the
determination of the Thevenin’s equivalent voltage ETh and the Thevenin’s equivalent resistance RTh. This
experiment will use the circuit diagram shown in Fig. 2 to verify Thevenin’s theorem using the LTspice
simulator.
2 3V
R3
E2
R24 R5
R1 1 R48
V E1
4
Fig. 2 Circuit diagram for Experiment 2
Tasks for Experiment 2:
(1)
Determine the Thevenin’s equivalent voltage ETh and the Thevenin’s equivalent resistance RTh
external to R5.
(2)
Draw the Thevenin’s equivalent circuit external to R5.
(3)
Choose a random resistance value for R5 and theoretically calculate the current through and the
voltage across R5.
(4)
Using the chosen value of R5, build up the circuit in the LTspice simulator and measure ETh and RTh
external to R5.
(5)
Capture the waveforms of the current through and the voltage across R5.
(6)
Compare the theoretical prediction with the simulation results.
Evidence required in your report for the assessment of Experiment 2:
Title of your investigation.
Description of your investigation (what did you do).
The full working of determining ETh and RTh external to R5. You can write down your working on a
piece of paper and include the photo of your working in the coursework report.
Theoretical prediction of the voltage across and the current through R5.
A circuit diagram built up in the LTspice simulator.
Measurements of ETh and RTh in the LTspice simulator.
Captured waveforms labelled with all relevant parameters.
The simulation results obtained via LTspice should agree with the theoretical prediction. If not,
please find out the reasons and correct mistakes (if there any) in your theoretical calculation and/or
in the simulation.
Full source files ready for simulation (submitted along with the report).
Marking scheme for Experiment 2 [Total 10 marks]:
The value and the polarity of ETh and the value of RTh are correctly calculated. [2 marks]
The Thevenin’s equivalent circuit is correct and the voltage across and the current through R5 are
correct. [2 marks]
The circuit is correctly built up in LTspice. [2 marks]
The value and the polarity of E Th and the value of R Th are correctly measured via LTspice. [2 marks]
The simulation results agree with the theoretical prediction. If not, proper analysis and discussions
should be provided. [2 marks]
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Section 2 – Project to Design an Ultrasonic Signal Amplifier
2.1 Introduction
Ultrasonic techniques have been widely utilised in various fields such as distance ranging, non-destructive
testing, medical imaging and flow measurements. One example we frequently come across in our daily lives
is the parking sonars of land vehicles to alert the driver of obstacles.
In a parking sonar system, the ultrasonic transducers with a centre frequency of 40 kHz are commonly used
to transmit and receive ultrasonic waves. In the transmitting process, the ultrasonic transducer is driven by a
high voltage signal and generates ultrasonic waves. The ultrasonic waves will be reflected by obstacles
nearby and can be received by the ultrasonic transducers.
The received ultrasonic signals are usually weak, with peak-to-peak voltage amplitude (V P-P) typically in the
range from 0.1 mVp-p to 10 mVP-P, determined by the distance between the ultrasonic transducer and the
obstacles.
These weak signals will be amplified using ultrasonic signal amplifiers and then will be converted into
standard digital signals (for instance, TTL signals) which can be further processed by digital circuits, such as a
microcontroller like the Arduino. The time of flight of the ultrasonic signals will be measured by the
microcontroller. As the speed of sound is known (e.g., approximately 343 m/s in air at room temperature),
the separation between the vehicle and the obstacle can be calculated.
Ultrasonic signal amplifiers are essential for an ultrasonic system for at least two reasons. For one thing, they
can significantly increase the amplitude of the received ultrasonic signals which are too weak to be
converted into standard TTL signals. For another, they can be designed to have many advanced features such
as incorporating bandpass filters to increase the signal to noise ratio of the ultrasonic signals, including a
diplexer to enable one ultrasonic transducer to operate as both a transmitter and a receiver, and containing
a time gain compensation (TGC) function to dynamically compensate for the attenuation of the ultrasonic
wave.
The aim of this project is to design a basic ultrasonic signal amplifier for a parking sonar system. The received
ultrasonic signal is a 10-cycle tone burst sine wave signal, whose centre frequency is 40 kHz. The amplitude
of the ultrasonic signal is 10 mV P-P. The waveform of the ultrasonic signal (which is more complicated in
reality) is shown in Fig. 5. The resistance of the ultrasonic transducer is 400 Ω. You will develop the amplifier
which can amplify the signal to a peak-to-peak amplitude between 4 V P-P and 5 VP-P. You will design, analyse
and evaluate the circuit using the LTspice simulator.
Fig. 5 An example of the waveform of a simplified ultrasonic signal
2.2 Specification and requirements
The peak-to-peak amplitude of the ultrasonic signal is 10 mV P-P, and the resistance (internal
resistance) of the ultrasonic transducer is 400 Ω.
The peak-to-peak amplitude of the output signal is between 4 VP-P and 5 VP-P.
A 10 MΩ resistor (the load) is connected between the output stage of the amplifier and the
ground.
The waveform of the output signal is not distorted.
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Operates from a 15 V DC voltage supply.
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2.3 Assessment
You are strongly recommended to structure your report according to the marking scheme introduced in
Section 2.4. The design, the simulation, the analysis and the evaluation of the circuit should be shown in the
report. Your source files must be ready for simulation so please test them before submission.
2.4 Marking Scheme for Section 2 [Total 55 marks]
(1) Introduction [5 marks]
Write an introduction to the project aimed at a non-technical audience. This should briefly set out the
background, the motivation, the aims and the objectives of the project. Note that the emphasis is on writing
in a style that a lay person would be able to understand.
(2) Literature review [5 marks]
Before designing your circuit, carry out a literature review to find out about similar products. Try to discover:
why people use them;
what are the advantages of using an ultrasonic signal amplifier;
what are the design trade-offs;
what commercial products are available;
what are the key specifications for these products in terms of parameter types such as noise,
distortion and anything else you can identify.
Identify a number of designs that you think are contenders for your project. Include a reference section at the
back of the report to indicate your sources. Use the Harvard APA referencing system.
(3) Description and analysis of your chosen circuit [10 marks]
When you have carried out the literature review and identified a suitable design, write in your report a clear
and detailed explanation of how the circuit works in your own words. Any analysis and theoretical
calculation which are needed to justify any aspect of the design should also be included.
(4) Evaluation of your circuit [10 marks]
Evaluate the circuit through simulation to see if it meets the specification. You may also measure the voltage
gain, the frequency response and any other parameter which your research has led you to believe may be
relevant.
(5) Tutor assessment of the circuit [Total 15 marks]
Whether the voltage amplitude of the output signal is within the targeted range for the given input
signal. [5 marks]
Whether the waveform of the output signal is distorted. [5 marks]
Whether the waveform has a DC offset. [5 marks]
(6) Summary [5 marks]
Write a summary of the project aimed at a non-technical audience. You should summarise the work you
have done for this project design. You can also include conclusions and future work for this research. Note
that the emphasis is on writing in a style that a lay person would be able to understand.
(7) Quality of report writing and formatting/presentation [5 marks]
This includes the standard of the English grammar and punctuation, the quality of diagrams and the degree to
which the report is well structured, enabling a reader to understand what you have done and why.
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