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CT1302Lab sheet 6

Standard Amplitude Modulation (AM)

Objectives:

1- Generating standard AM signal and show the effect of μ2- Comparing standard AM and DSB-SC modulated signals

Blocks Required:

- Signal Generator (carrier signal source and message signal source) - Constant block

- Product Block - Summer Block - Blocks for viewing the signals – Scope

We can find these blocks in the following locations of Simulink Library

Carrier, Message blocks:

Simulink → Sources → Signal Generator

Simulink → Sources → Constant

Filter: Simulink → Signal Processing Blockset → Filtering → Filter Designs → Analog Filter Design

View Block:

Simulink → Sink → Scope

Product and Summer Block

Simulink → Math Operations→ Product

Simulink → Math Operations→ Sum

Generating standard AM signal and the effects of μ values:

To generate standard AM modulated signal, we just have to implement the equation of AM in block level

SAM(t) = Ac c(t) + m(t) c(t) = [Ac + m(t) ] c(t)

King Saud UniversityCollage Of Applied Studies And Community Service

The two ways of modulator block diagram

Way#1:

Way#2:

Let’s do AM modulation using the following signals

m(t) = 2 sin(6πt) c(t) = 5 sin(100πt) What is the value of μ? Draw the SAM(t) in time domain

m(t) = 3 sin(4πt) c(t) = 3 sin(200πt) What is the value of μ? Draw the SAM(t) in time domain

m(t) = 3 sin(8πt) c(t) = 2 sin(200πt) What is the value of μ?

King Saud UniversityCollage Of Applied Studies And Community Service

Draw the SAM(t) in time domain

Comparing standard AM modulated signal and DSB-SC modulated signal To get a DSB-SC from the standard AM modulator, set the Ac to 0 (in the carrier signal 2 Block in way#1 diagram or in the Ac Block in way#1 diagram)

Generate a standard AM modulated signal from the following signals:

m(t) = sin(2πt) c(t) = 2 sin(40πt)

Draw the SAM(t) in time domain

From the same block diagram generate a DSB-SC modulated signal using the same signals.Draw the SDSB (t) in time domain

Note the difference between the two signals.