Class: Senior Secondary School 1 (SS1 / SSS 1)
Term: 3rd Term
Week: 4
Age: 15 years
Duration: 45 minutes
Subject: Radio, Tv & Electronics
Curriculum Theme: Trade
Previous Lesson: Modulation: Definition And Types.
Topic: MODULATION
Subject Matter: AM waveform, FM waveform, Percentage modulation

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

Define modulation.
State the reasons for modulation.
Identify the two main types of modulation.
Explain Amplitude Modulation (AM) and Frequency Modulation (FM).
Calculate the percentage modulation given relevant parameters.

Affective Domain:

Appreciate the importance of modulation in communication systems.
Show interest in the study of electronic communication.
Participate actively in class discussions.

Psychomotor Domain:

Sketch simple Amplitude Modulation (AM) and Frequency Modulation (FM) waveforms.
Solve basic problems involving percentage modulation.

Collaborate with peers during group activities.
Communicate ideas clearly during discussions.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Trade Subjects.
State Unified Scheme of Work for Radio, TV & Electronics (SSS 1).
Anyanwu, A. (2018). Fundamentals of Radio, TV and Electronics for Senior Secondary Schools. Zenith Publishers.
https://www.electronics-notes.com/articles/radio/modulation/what-is-modulation.php
https://www.tutorialspoint.com/analog_communication/analog_communication_modulation.htm

Instructional Materials

The teacher will teach this lesson with the aid of:

Chalkboard/Whiteboard
Markers/Chalk
Charts showing examples of AM and FM waveforms
Graph sheets
Calculators

Rationale for the Lesson

This lesson helps pupils understand how audio and video signals are transmitted over long distances through radio and television. Understanding modulation is fundamental to comprehending the working principles of various communication devices used daily.

Prerequisite/Previous Knowledge

Pupils have a basic understanding of waves, signals, frequency, and amplitude from their previous studies in Basic Science and Technology.

Lesson Content/Board Summary

MODULATION

Definition of Modulation

Modulation is the process of varying one or more properties of a high-frequency carrier wave with a low-frequency information (modulating) signal. The properties of the carrier wave that can be varied include its amplitude, frequency, or phase.

Need for Modulation

Modulation is necessary for several reasons:

To enable signals to travel over long distances without significant loss.
To allow multiple signals to be transmitted simultaneously over the same medium without interference (multiplexing).
To reduce the physical size of antennas required for efficient transmission.
To improve the quality of reception and reduce noise.

Types of Modulation

The two main types of modulation are:

Amplitude Modulation (AM): The amplitude of the carrier wave is varied in proportion to the instantaneous amplitude of the modulating signal, while its frequency and phase remain constant.
Frequency Modulation (FM): The frequency of the carrier wave is varied in proportion to the instantaneous amplitude of the modulating signal, while its amplitude and phase remain constant.

Amplitude Modulation (AM) Waveform

In AM, the carrier wave’s amplitude changes according to the information signal. The resulting AM waveform has an envelope that mirrors the shape of the modulating signal.

Frequency Modulation (FM) Waveform

In FM, the carrier wave’s frequency changes according to the information signal. When the modulating signal’s amplitude is high, the carrier frequency deviates more, and when it is low, the carrier frequency deviates less. The amplitude of the FM wave remains constant.

Percentage Modulation

Percentage modulation (or modulation index) indicates the extent to which the carrier wave is modulated by the signal. It is a measure of how much the carrier’s amplitude or frequency changes relative to its unmodulated state.

For Amplitude Modulation, percentage modulation (m) is calculated as:

% Modulation (m) = (Amplitude of Modulating Signal / Amplitude of Carrier Signal) × 100%

Where:

Amplitude of Modulating Signal (Em) = Maximum change in carrier amplitude from its unmodulated value.
Amplitude of Carrier Signal (Ec) = Unmodulated carrier amplitude.

Example: If the amplitude of the modulating signal is 5V and the amplitude of the carrier signal is 10V, calculate the percentage modulation.

% Modulation = (5V / 10V) × 100% = 50%

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils, takes attendance, and reviews the previous lesson briefly. The teacher then asks pupils about how radio and television signals travel over long distances, leading them to the topic of modulation.
Pupils’ Activity: Pupils respond to greetings, answer questions, and listen attentively to the introduction.
Learning Point: Pupils are prepared for the new lesson and relate it to prior knowledge.

Step 2: Definition and Need for Modulation

Time: 8 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines modulation and explains the various reasons why it is necessary for effective communication. The teacher writes key points on the board.
Pupils’ Activity: Pupils listen, take notes, and ask questions for clarification.
Learning Point: Pupils understand what modulation is and why it is important.

Step 3: Types of Modulation

Time: 8 minutes
Teaching Skill: Illustration/Classification
Teacher’s Activity: The teacher introduces the two main types of modulation: Amplitude Modulation (AM) and Frequency Modulation (FM). The teacher sketches simplified waveforms for both AM and FM on the board or uses charts to illustrate.
Pupils’ Activity: Pupils observe the sketches, take notes, and differentiate between AM and FM based on the visual representations.
Learning Point: Pupils can identify and distinguish between AM and FM waveforms.

Step 4: Amplitude Modulation (AM)

Time: 7 minutes
Teaching Skill: Explanation/Description
Teacher’s Activity: The teacher explains AM in detail, focusing on how the amplitude of the carrier wave is varied by the modulating signal while frequency and phase remain constant. The teacher points out the envelope of the AM wave.
Pupils’ Activity: Pupils listen, take notes, and ask questions to clarify their understanding of AM.
Learning Point: Pupils gain a deeper understanding of Amplitude Modulation.

Step 5: Frequency Modulation (FM)

Time: 7 minutes
Teaching Skill: Explanation/Description
Teacher’s Activity: The teacher explains FM in detail, focusing on how the frequency of the carrier wave is varied by the modulating signal while its amplitude remains constant. The teacher highlights the constant amplitude of an FM wave.
Pupils’ Activity: Pupils listen, take notes, and compare FM with AM.
Learning Point: Pupils understand Frequency Modulation and its key characteristics.

Step 6: Percentage Modulation

Time: 5 minutes
Teaching Skill: Calculation/Problem Solving
Teacher’s Activity: The teacher introduces the concept of percentage modulation, provides the formula, and works through a simple example calculation on the board. The teacher guides pupils on how to use the formula.
Pupils’ Activity: Pupils copy the formula, follow the example, and attempt similar calculations.
Learning Point: Pupils learn how to calculate percentage modulation.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Define modulation.
State two reasons why modulation is necessary.
Mention the two main types of modulation.
Briefly explain the difference between AM and FM waveforms.
If the amplitude of a modulating signal is 7V and the unmodulated carrier amplitude is 14V, calculate the percentage modulation.

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization
Teacher’s Activity: The teacher briefly summarizes the key points of the lesson on modulation, emphasizing its role in communication. The teacher assigns homework, asking pupils to research applications of AM and FM.
Pupils’ Activity: Pupils listen to the summary and copy down the homework assignment.
Learning Point: The lesson is reinforced, and pupils are given an opportunity for further learning.

Lesson Keywords

Modulation – The process of varying a property of a carrier wave with an information signal.
Carrier Wave – A high-frequency electromagnetic wave used to carry information.
Modulating Signal – The low-frequency information signal (e.g., audio, video) that modifies the carrier wave.
Amplitude Modulation (AM) – A type of modulation where the amplitude of the carrier wave is varied.
Frequency Modulation (FM) – A type of modulation where the frequency of the carrier wave is varied.
Percentage Modulation – A measure of the extent to which a carrier wave is modulated.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide additional complex problems on percentage modulation or ask them to research the advantages and disadvantages of AM and FM. For pupils who require more support, the teacher can provide simplified diagrams, offer one-on-one explanations, and focus on defining key terms and identifying the types of modulation.

Note for teachers using this lesson plan

Teachers should ensure they have clear charts or diagrams of AM and FM waveforms prepared before the lesson. Practical demonstrations using a signal generator and oscilloscope, if available, would greatly enhance understanding. Encourage pupils to draw and label the waveforms themselves. Emphasize the practical applications of modulation in everyday devices like radio and television.