This document provides instructions for a student laboratory project to build an Amplitude Shift Keying (ASK) modulator circuit. The objectives are to generate a 1 kHz square wave pulse and use it to modulate a 100 kHz carrier signal to produce an ASK modulated output. The circuit uses two Timer IC 555 chips - one configured as an astable multivibrator to generate the pulse signal, and the other as an astable multivibrator modulated by the pulse input to produce the ASK output. Students are asked to construct the circuit on a printed circuit board, test it, and write a laboratory report explaining the theory, design, testing, and results of the project.

1. EEEC6440315
Communication Systems
Faculty of Engineering and Computer Technology
Laboratory Manual
Lecturer: Ravandran Muttiah BEng (Hons) MSc MIET
Year/Semester: Year 2 / Semester 2
Academic Session: 2020/2021
The information in this documentis important and should be noted by all students undertaking the
Bachelor of Engineering (Honours) in Electrical and Electronic Engineering
Approved by Coordinator: Endorsed By Dean:
------------------------------------------ __________________

2. AIMST University Faculty of Engineering and Computer Technology
BEng (Hons) in Electrical and Electronic Engineering Communication Systems 1
Mini Project 1 - Amplitude Shift Keying (ASK) Modulator
Theory
ASK is also known as ON-OFF keying. It’s one of the modulation scheme used to
transmit digital data using high frequency carrier signal. It’s very simple and popular
method. It transmits 1’s and 0’s of digital data by transmitting carrier or no carrier like
bit 1 (logic high) is transmitted with carrier frequency. Bit 0 (logic low) is transmitted
with no carrier. Means series of bits, bit stream is transmitted as carrier ON and carrier
OFF.
Objectives
The objective of this project is to demonstrate how to generate a square pulse waveform
and to modulate the digital data into an ASK modulated signal using the circuit shown in
figure 1. The schematic layout has to be printed on a printed circuit board. Both the
pulse generator and the modulator uses timer IC 555. The pulse generator must produce
a waveform at 1 KHz. The complete ASK modulator circuit with the square wave pulse
generator has to be constructed with the help of the specifications provided.
Specifications
2 Variable Resistors 4.7 KΩ
2 Resistors 5.6 KΩ
3 Capacitors 0.1 μF
1 Capacitor 1 nF
2 Timers IC 555
Power Supply 5 V
Procedure
For pulse generator, the timer IC 555 is connected in Astable mode. It will generate
continuous pulses at 1 KHz frequency. The frequency is determined by RC components.
This 1 KHz pulse output is connected to reset pin (4) input of 2nd IC 555 that works as
ASK Modulator. As shown in figure 1 the IC 555 is configured as Astable Multi
vibrator. When its reset pin is high it generates continuous square pulses. And when its
reset pin is low its output is also low. The component values of R1, R2 and C1 were
selected as to get desire carrier frequency. The carrier frequency is selected as 100 KHz.

3. AIMST University Faculty of Engineering and Computer Technology
BEng (Hons) in Electrical and Electronic Engineering Communication Systems 2
Figure 1: ASK modulator
Report
Write a laboratory report on this project.
(1) Explain in detail about the theory of ASK modulator for the designed circuit with
the theoretical calculations of component values.
(2) Discuss the method of productions of printed circuit board layout, fabrications,
assembly of components and the test results.
(3) Prepare slides for presentation and demonstration of this project.
Vcc
5V
ASK
Output
R1
R3
R4
R2
4.7 KΩ 4.7 KΩ
5.6 KΩ
5.6 KΩ
Square
Pulse
Input
0.1 μF
C3
C4
0.1 μF
C1
1 nF
0.1 μF
C2
Vcc Vcc
GND GND
OUT OUT
RST
DIS
THR
TRI
CON
RST
DIS
THR
TRI
CON
+ +
555
555