Communications and Network, 2013, 5, 78-80
doi:10.4236/cn.2013.51B018 Published Online February 2013 (http://www.scirp.org/journal/cn)
Sound Card Based ASK Communication System for
Teaching Communication Principle Course
Ming Jin, Yang Pu
College of Information Science & Engineering, Ningbo University, Ningbo, China
Email: mingjin141@gmail.com, puyang@nbu.edu.cn
Received 2012
ABSTRACT
This paper deals with the issue of using the MATLAB tool in teaching the course of communication principles via con-
structing an Amplitude Shift Keying (ASK) communication system. Different from conventional MATLAB based si-
mulations, the constructed system transmits modulated signals through a wire audio channel by exploiting sound card.
Synchronization is required before the received signal being demodulated. Many practical problems should be consid-
ered as in real system. The designed system can be extended easily, and not only stimulates students’ interest in com-
munication course, but also helps them understanding the principles from system viewpoints.
Keywords: Sound Card; Communication Principles; ASK; Communication System
1. Introduction
Communication principles course is one of basic courses
of electronic engineering (EE) related specialties. Com-
munications technology is one of the most rapidly grow-
ing technologies in the telecommunications industry. As
a kernel course in EE, Communication principles course
plays an important role. Many universities [1-7] have
established hardware laboratory wh ich can implement all
experiments involved in the course. However, to estab-
lish such labs is very expensive. With the shortage of
supplement, computer aided simulations is an option.
Many Matlab/simulink based simulation program
packages for communication principles course are avail-
able online. However, some packages consist of many
independent script files; it is difficult for students to op-
erate it. And some program packages are designed based
on GUI or simulink. We found that these kinds of pack-
ages may not work in different computer platform or
software versions. Moreover, most of available simula-
tions are based on the ideal environment. Many practical
problems, which may be encountered in hardware labo-
ratory or real communication systems, are skipped. In [8],
sound card is used in a demo of communication system.
However, it is not shared for everyone.
Following the idea of [8], in this paper, we present a
MATLAB based Amplitude Shift Keying (ASK) com-
munication system which is realized by transmitting the
modulated signal through a wire audio channel by ex-
ploiting sound card. Hence, it is different from the soft-
ware only based simulations. And many practical prob-
lems, such as synchronization, may be encountered. In
addition, the simple ASK communication system can be
extended easily, and will not only stimulate students’
interest in communication course, but also help them
understanding the principles from system viewpoints.
2. Basic Principle of ASK
This section describes the modulation and demodulation
principles of ASK digital signals. Assumed that a binary
digital data 0
n
a
or 1, , need to be trans-
mitted through ASK modulation of car rier frequency
1, 2,n
c
.
Then, the transmission digital data sequence is given as
()( )
n
n
dtagtnT
(1)
where ()
t and T are the pulse shape of each transmis-
sion digital data and the bit duration, respectively.
When ()
t is trailing rectangular pulse, it is given
that
1,
() 2
0, otherwise
TT
t
gt
2
(2)
The digital data sequence is modulated by multiplying
a carrier frequency signal and then transmitted. The
transmitted signal is given by
()()cos 2c
tdt ft
(3)
The transmitted signal is contaminated by multi path
fading and AWGN, and at the receiver it is received as
Copyright © 2013 SciRes. CN