-SQA-SCOTTISH QUALIFICATIONS AUTHORITY
HIGHER NATIONAL UNIT SPECIFICATION
GENERAL INFORMATION
-Unit Number-
8540197
-Superclass-
XM
-Title-
COMMUNICATION
DEMODULATION
PRINCIPLES:
MODULATION
AND
-----------------------------------------DESCRIPTIONGENERAL COMPETENCE FOR UNIT: Interpreting the principle methods by
which a carrier signal may be modulated and demodulated.
OUTCOMES
1.
interpret the principles of amplitude modulation and demodulation;
2.
interpret the principles of angle modulation and demodulation;
3.
interpret the principles of uncoded and coded pulse modulation
techniques;
4.
interpret the principles of digital data modulation and demodulation.
CREDIT VALUE:
2 HN Credits
ACCESS STATEMENT: Access to this unit is at the discretion of the centre.
However, it would be beneficial if the candidate possessed HN Unit:
8540187 Telecommunication Fundamentals
2460877 Single Phase AC Networks
or similar qualifications or experience.
----------------------------------------For further information contact: Committee and Administration Unit, SQA,
Hanover House, 24 Douglas Street, Glasgow G2 7NQ.
Additional copies of this unit may be purchased from SQA (Sales and Despatch
section). At the time of publication, the cost is £1.50 (minimum order £5.00).
Unit No. 8540197
Continuation
HIGHER NATIONAL UNIT SPECIFICATION
STATEMENT OF STANDARDS
UNIT NUMBER:
8540197
UNIT TITLE:
COMMUNICATION PRINCIPLES: MODULATION AND
DEMODULATION
Acceptable performance in this unit will be the satisfactory achievement of the
standards set out in this part of the specification. All sections of the statement of
standards are mandatory and cannot be altered without reference to SQA.
OUTCOME
1.
INTERPRET THE PRINCIPLES OF AMPLITUDE MODULATION
AND DEMODULATION
PERFORMANCE CRITERIA
(a)
(b)
(c)
(d)
(e)
(f)
Calculation of bandwidth occupied by amplitude modulation signal
types is correct.
Description of the effect of over and under modulation upon the
performance of the system is correct.
Calculation of power in an amplitude modulated signal is correct.
Description of the operation of amplitude modulator circuits is
correct.
Description of the operation of amplitude demodulator circuits is
correct.
Report on the performance of a demodulator circuit is concise and
accurate.
RANGE STATEMENT
Amplitude modulation signal types: double sideband full carrier; single sideband
full carrier; single sideband suppressed carrier.
Calculation of power for various modulation factors: carrier; sideband; average;
peak envelope.
Performance: circuit action; effects of noise.
EVIDENCE REQUIREMENTS
Written and graphical evidence of the candidate’s ability to interpret principles of
amplitude modulation and demodulation as detailed in performance criteria (a) (c).
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Unit No. 8540197
Continuation
Production of a report of a demodulator circuit as detailed in performance criteria
(d) - (f).
OUTCOME
2.
INTERPRET THE PRINCIPLES OF ANGLE MODULATION AND
DEMODULATION
PERFORMANCE CRITERIA
(a)
(b)
(c)
(d)
(e)
Explanation of the meaning of angle modulation parameters is
clear and precise.
Calculation of bandwidth of a sinusoidal frequency modulated
signal by use of Carson’s Rule and Bessel Tables, modulation
index range between 0.25 and 8.65, is correct.
Graphical representation of the frequency component of an angle
modulated signal is drawn correctly.
Description of the operation of angle modulator and demodulator
circuits employing current technology is correct.
Report on the performance of an angle demodulator circuit is
concise and accurate.
RANGE STATEMENT
Angle modulation parameters: peak deviation; modulation index; deviation ratio.
Performance: circuit action; effects of noise.
EVIDENCE REQUIREMENTS
Calculations, written and graphical evidence of the candidate’s ability to interpret
principles of angle modulation and demodulation as detailed in performance
criteria (a) - (c).
Production of a report of a demodulator circuit as detailed in performance criteria
(d) and (e).
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Unit No. 8540197
Continuation
OUTCOME
3.
INTERPRET THE PRINCIPLES OF UNCODED AND CODED
PULSE MODULATION TECHNIQUES
PERFORMANCE CRITERIA
(a)
(b)
(c)
(d)
(e)
(f)
Statement of the criterion for the minimum sampling rate is
correct.
Explanation of the basic properties of pulse modulation is clear
and precise.
Description of specific methods of uncoded pulse modulation is
correct.
Description of the basic principles of pulse coded modulation
(PCM) is correct.
Report on the performance of a PCM system is concise and
accurate.
Description of the basic principles of delta modulation is correct.
RANGE STATEMENT
Basic properties: frequency spectrum; bandwidth; bias distortion; intersymbol
interference.
Specific methods: pulse width modulation; pulse position modulation; pulse
amplitude modulation.
Basic principles of PCM:
quantisation noise.
sampling; quantisation by linear pulse encoding;
Delta modulation: difference signal; positive pulses; negative pulses.
EVIDENCE REQUIREMENTS
Written and graphical evidence to show the candidate’s knowledge and
understanding of pulse modulation techniques and ability to produce a report on
the performance of a pulse demodulation system as detailed in performance
criteria (a) - (f).
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Unit No. 8540197
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OUTCOME
4.
INTERPRET THE PRINCIPLES OF DIGITAL DATA
MODULATION AND DEMODULATION
PERFORMANCE CRITERIA
(a)
(b)
Description of elementary forms of digital data modulation and
demodulation techniques is correct.
Report on the performance of an elementary digital data
demodulator receiver using phase locked loop technology is
complete and accurate.
RANGE STATEMENT
Elementary forms: amplitude shift keying; phase shift keying; frequency shift
keying.
EVIDENCE REQUIREMENTS
Written and/or graphical evidence to show the candidate’s knowledge and
understanding of digital data modulation and demodulation principles and
produce a report on an elementary digital data demodulator receiver.
MERIT To gain a pass in this unit, a candidate must meet the standards set out
in the outcomes, performance criteria, range statements and evidence
requirements.
To achieve a merit in this unit, a candidate must demonstrate a superior or more
sophisticated level of performance. This may be demonstrated by:
(i)
(ii)
analytical skills;
logical presentation of work.
-----------------------------------------
ASSESSMENT
In order to achieve this unit, candidates are required to present sufficient
evidence that they have met all the performance criteria for each outcome within
the range specified. Details of these requirements are given for each outcome.
The assessment instruments used should follow the general guidance offered by
the SQA assessment model and an integrative approach to assessment is
encouraged. (See references at the end of support notes).
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Unit No. 8540197
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Accurate records should be made of the assessment instruments used showing
how evidence is generated for each outcome and giving marking schemes
and/or checklists, etc. Records of candidates’ achievements should be kept.
These records will be available for external verification.
SPECIAL NEEDS
Proposals to modify outcomes, range statements or agreed assessment
arrangements should be discussed in the first place with the external verifier.
 Copyright SQA 1997
Please note that this publication may be reproduced in whole or in part for
educational purposes provided that:
(i)
(ii)
no profit is derived from the reproduction;
if reproduced in part, the source is acknowledged.
6
Unit No. 8540197
Continuation
HIGHER NATIONAL UNIT SPECIFICATION
SUPPORT NOTES
UNIT NUMBER:
8540197
UNIT TITLE:
COMMUNICATION PRINCIPLES: MODULATION AND
DEMODULATION
SUPPORT NOTES: This part of the unit specification is offered as guidance.
None of the sections of the support notes is mandatory.
NOTIONAL DESIGN LENGTH: SQA allocates a notional design length to a unit
on the basis of time estimated for achievement of the stated standards by a
candidate whose starting point is as described in the access statement. The
notional design length for this unit is 80 hours. The use of notional design length
for programme design and timetabling is advisory only.
PURPOSE The purpose of this unit is to provide an understanding of carrier
signal modulation for candidates who will be specialising in radio frequency
engineering and/or telecommunication engineering.
CONTENT/CONTEXT
To modulate means to regulate or adjust, and
specifically in the case of radio communications it means to regulate some
parameter of a high frequency carrier wave by means of the lower frequency
message signal. As a result of this process, the modulated carrier conveys
complete information about the message signal which might be recovered by
suitable processing techniques.
This unit is designed to:
(a)
(b)
develop competence in describing the main methods by which a carrier
signal is modulated;
contain underpinning knowledge to support HN Units specialising in radio
frequency engineering and or telecommunication engineering.
Corresponding to outcomes 1 and 2:
It is recommended that:
(i)
(ii)
(iii)
(iv)
(v)
for calculation purposes, one modulating signal (low frequency) is used,
being a single sine or cosine wave;
bessel tables or graphs be used.
the use of frequency spectrum diagrams be used;
the laboratory exercise be performed by each candidate;
speech bandwidth of (300-3400)Hz be used.
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Unit No. 8540197
Continuation
Corresponding to outcome 4:
It is recommended that a report on the performance of an elementary frequency
shift keying receiver, with aid of block diagram, is produced.
APPROACHES TO GENERATING EVIDENCE This unit should be taught within
a practical environment where access to the following sub-assemblies: amplitude
demodulation circuit, angle demodulation circuit, pulse coded demodulation
system and test apparatus should be readily available.
Report on an elementary frequency shift keying receiver block diagram using
phase locked loop.
ASSESSMENT PROCEDURES
Outcome 1 could be assessed using structured questions for performance
criteria (a), (b) and (c). The descriptions in performance criteria (d) and (e) could
be integrated into the report for (f).
Outcome 2 could be assessed using structured questions for performance
criteria (a), (b) and (c). The description in performance criterion (d) could be
integrated into the report for (e).
Outcome 3 could be assessed using a report for performance criterion (e) and
integrating the remaining performance criteria into the report.
Outcome 4 could be assessed using a report for performance criterion (b) and
integrating the remaining performance criteria into the report.
PROGRESSION This unit may lead on to any of the following HN units:
8540317 Radio Communication Circuits
8540207 Satellite Communication Technology
8540217 Television Broadcasting Systems
8540227 Radio Broadcasting Systems
REFERENCES
1.
2.
3.
4.
Guide to unit writing.
For a fuller discussion on assessment issues, please refer to SQA’s
Guide to Assessment.
Information for centres on SQA’s operating procedures is contained in
SQA’s Guide to Procedures.
For details of other SQA publications, please consult SQA’s publications
list.
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Unit No. 8540197
Continuation
 Copyright SQA 1997
Please note that this publication may be reproduced in whole or in part for
educational purposes provided that:
(i)
(ii)
no profit is derived from the reproduction;
if reproduced in part, the source is acknowledged.
9