Course Code: EEE 310
Course Title: COMMUNICATION SYSTEMS LAB
Experiment No: 05
Experiment Title: Design and Study ASK signal using MATLAB.
NURUJJAMAN SHAWN
163016016
SUBMITTED TO:
TAMA FOUZDER
SUBMISSION DATE:
1/5/2021
Objective:
To generate amplitude shift keyed (ASK) signal using MATLAB.
Theory:
Amplitude Shift Keying (ASK)
In amplitude shift keying, the amplitude of the carrier signal is varied to create signal
elements. Both frequency and phase remain constant while the amplitude changes.
Binary ASK (BASK)
Although we can have several levels (kinds) of signal elements, each with a different
amplitude, ASK is normally implemented using only two levels. This is referred to as
binary amplitude shift keying or on-off keying (OOK). The peak amplitude of one signal level is
0; the other is the same as the amplitude of the carrier frequency. Figure 1.1
gives conceptual views of binary ASK.
Generation of ASK –
Amplitude shift keying - ASK - is a modulation process, which imparts to a sinusoid two or more
discrete amplitude levels. These are related to the number of levels adopted by the digital
message. For a binary message sequence there are two levels, one of which is typically zero. The
data rate is a sub-multiple of the carrier frequency. Thus the modulated waveform consists of
bursts of a sinusoid. One of the disadvantages of ASK, compared with FSK and PSK, for
example, and is that it has not got a constant envelope. This makes it’s processing (e.g., power
amplification) more difficult, since linearity becomes an important factor. However, it does make
for ease of demodulation with an envelope detector.
Example MATLAB PROGRAM:
clc;
clear all;
close all;
t = 0:0.001:1; % Time duration for all signal
A = 3; % Amplitude of the carrier signal
fc = 12; % Frequency of the carrier signal
fm = 3; % Frequency of the message signal
message = A/2*square(2*pi*fm*t)+(A/2); % Message signal (Square wave)
subplot(3,1,1)
plot(t,message);
xlabel('Time');
ylabel('Amplitude');
title('Square Wave');
grid on;
carrier = A*sin(2*pi*fc*t); % Carrier signal
subplot(3,1,2)
plot(t,carrier);
xlabel('Time');
ylabel('Amplitude');
title('Carrier Signal');
grid on;
modulation = message.*carrier;
subplot(3,1,3)
plot(t,modulation);
xlabel('Time');
ylabel('Amplitude');
title('ASK Signal');
grid on;
Observation:
Discussion:
In this experiment we first take Amplitude and frequency of carrier and message signal then
generate message signal for a digital signal then plot it. Again we generate a carrier signal and
plot it and lastly we dot multiply message and carrier signal which we generate before and after
dot multiplication we can call it modulated signal which is also called Amplitude shift keyed
(ASK) signal.