ASK Modulator Project
Belal Alaa Eldin Marwan Fouad Youssef Ahmed Abdelaziz
Electronics and Communication Electronics and Communication Electronics and Communication
Engineering Engineering Engineering
AASTMT AASTMT AASTMT
Giza, Egypt Giza, Egypt Giza, Egypt
Belal.ahmed@student.aast.edu Marwanfouad@student.aast.edu Youssef.Abdelaziz@student.aast.edu
20107436 20107966 20107472
Abstract— This document outlines an experimental
study on the functioning of an Amplitude-Shift Keying The ASK system can be divided into three blocks. The
(ASK) modulation system that utilizes an envelope first one represents the transmitter, the second one is a linear
detector. The research sought to confirm theoretical model of the effects of the channel, the third one shows the
structure of the receiver. The following notation is used:
predictions by means of practical application. Even with
• ht(f) is the carrier signal for the transmission
minor obstacles and minor inaccuracies faced during the
experiment, the results showed alignment with • hc(f) is the impulse response of the channel
anticipated theoretical outcomes. The results offer a
• n(t) is the noise introduced by the channel
solid basis for grasping fundamental modulation
methods in digital communication systems and • hr(f) is the filter at the receiver
emphasize the practical importance of ASK in conveying
• L is the number of levels that are used for
binary data.
transmission
• Ts is the time between the generation of two
Keywords—ASK, Communication Systems, symbols
Modulation, Signal processing, Digital Communications
I. INTRODUCTION
A. ASK Modulation Overview
Amplitude-shift keying (ASK) is a specific kind of
amplitude modulation which modulated a carrier wave with
respect to digital data signals.[1] In an incoming signal
consisting of a number of bits, one or more bits are depicted
Figure 2 ASK Modulation
by a specific symbol, which is transmitted during a given
interval by sending a carrier wave at a fixed amplitude and
frequency.[citation needed] Suppose one symbol represents Different symbols are represented with different
voltages. If the maximum allowed value for the voltage is A,
just one bit, under such circumstances the carrier signal
then all the possible values are in the range [−A, A] and they
would be on its normal amplitude when the input signal is are given by:
on and would either be at a lower amplitude or off if the
input signal was not on.[1]
All forms of digital modulation, however, use a Equation 1
limited number of unique signals for encoding digital
The difference between one voltage and the other is:
information. ASK works with a limited number of ample
where pattern of the binary digits is assigned to each
amplitude. Usually, each amplitude represents an integral
number of bits. Each combination of bits is a symbol that Equation 2
corresponds to a particular amplitude. The demodulator of
the modulator set that employs a specific symbol-set finds Considering the picture, the symbols v[n] are generated
the amplitude of the scanned signal and makes its estimate randomly by the source S, then the impulse generator
in the form of a symbol, restoring an original one thereafter. creates impulses with an area of v[n]. These impulses are
sent to the filter ht to be sent through the channel. In other
The frequency and phase of the carrier do not vary.
words, for each symbol a different carrier wave is sent with
the relative amplitude.
Out of the transmitter, the signal s(t) can be expressed in the
form:
Figure 1 ASK Diagram
©2024 IEEE Equation 3
Figure 3 ASK Probability of Error
In the receiver, after filtering through hr (t) the signal is:
Equation 4
where we use the notation:
If we represent all the probability density functions on the
same plot against the possible value of the voltage to be
transmitted, we get a picture like this (the case of L = 4 is
shown). [1]
Equation 5
where * indicates the convolution between two signals. The probability of making an error after a single symbol has
After the A/D conversion the signal z[k] can be expressed in been sent is the area of the Gaussian function falling under
the functions for the other symbols. It is shown in cyan for
the form:
just one of them. If we call the area under one side of
the Gaussian, the sum of all the areas will be:
. The total probability of making an error
Equation 6 can be expressed in the form:
In this relationship, the second term represents the
symbol to be extracted. The others are unwanted: the first Equation 11
one is the effect of noise; the third one is due to the
intersymbol interference. If the filters are chosen so that g(t)
will satisfy the Nyquist ISI criterion, then there will be no We now must calculate the value of . To do that, we can
intersymbol interference and the value of the sum will be move the origin of the reference wherever we want: the area
zero, so: below the function will not change. We are in a situation
like the one shown in the following picture:
Equation 7
The transmission will be affected only by noise.
B. Probability of error
The probability density function of having an error of a
given size can be modelled by a Gaussian function; the Figure 4 Area of PDF
mean value will be the relative sent value, and its variance
will be given by:
Equation 8
The probability of making an error is given by:
Equation 9
Where Pe|Ho is the conditional probability of making an
error given that a symbol v0 has been sent and PHo is the
probability of sending a symbol v0.If the probability of
sending any symbol is the same, then:
Equation 10
It does not matter which Gaussian function we are
considering, the area we want to calculate will be the same.
The value we are looking for will be given by the following
integral:
Equation 12
where erfc(x) is the complementary error function. Putting
all these results together, the probability of making an error
is:
Figure 6 Functionalities of Emona DATEx
Equation 13
B. Oscilloscope Usage
From this formula, we can easily understand that the
probability of making an error decreases if the maximum
An oscilloscope was utilized to analyze the signals
amplitude of the transmitted signal or the amplification of
at various stages of the system. It was used to verify the
the system becomes greater; on the other hand, it increases
generated binary test sequence, observe the conversion
if the number of levels or the power of noise becomes
to the analog ASK-modulated output, and assess the
greater.
demodulated signal produced by the envelope detector.
This relationship is valid when there is no intersymbol
This provided a clear understanding of the signal
interference, i.e. g(t) is a Nyquist function. [1]
behavior throughout the process.
II. EQUIPMENT & SETUP
A. Emona DATEx Overview
The Emona DATEx is a modular
telecommunications training system designed for
educational purposes. It offers a practical platform to
study analog and digital communication principles
using plug-and-play modules. These modules allow for Figure 7 Oscilloscope Usage
signal generation, processing, and visualization, making
the system ideal for experiments like ASK modulation C. System Configuration
and demodulation.
The setup included generating a binary test sequence,
modulating it using ASK, and passing the modulated signal
through an envelope detector for demodulation. The
oscilloscope was connected at key points to observe and
verify the signals at each stage, ensuring the system was
functioning correctly.
III. PROCEDURE & RESULTS
A. Procedure: Generating ASK Signal
After setup, the device is wired to generate the ASK
sequence:
Figure 5 Emona DATEx Board
C. Results
Figure 8 Signal Generation Wiring
Which can be represented by the following diagram:
Figure 12 Ask demodulator using envelope detector (input 100 sin Analog signal)
Figure 9 Diagram for Signal Generation
B. Procedure: Demodulation
1. The DATEx soft front-panel (SFP) is launched and
ensured control over the DATEx board.
2. The Tunable Low-pass Filter module's soft Gain control Figure 13 Ask demodulator using envelope detector (input 2khz sin Analog signal)
is adjusted to its maximum setting by turning it fully
clockwise.
3. The Tunable Low-pass Filter module's soft Cut-off
Frequency Adjust control is set to its maximum by
turning it fully clockwise.
Figure 14 Ask demodulator using envelope detector (input 2khz sin Analog signal)
Figure 10 Demodulation Wiring
The whole experiment is represented by this diagram:
Figure 11 Whole Procedure Diagram
findings confirmed the theoretical comprehension of ASK
III. DISCUSSION
modulation and the envelope detection mechanism.
This study concentrated on deploying and examining an
ASK (Amplitude Shift Keying) modulation system utilizing Various obstacles were faced throughout the experiment.
the Emona DATEx apparatus, with an envelope detector Adjusting the Gain and Cut-off Frequency controls on the
used for the demodulation process. The main features of the Tunable Low-pass Filter module was essential for obtaining
system's performance, obstacles encountered, and the results optimal signal recovery. Any incorrect setup might result in
obtained are outlined below. either high noise levels or the loss of important details in the
demodulated signal. Moreover, outside influences like
The ASK modulator effectively produced a carrier signal electrical interference in the surroundings and constraints of
with an amplitude that changed according to the binary test the DATEx equipment might have caused slight
sequence. The oscilloscope readings verified that the high discrepancies.
and low amplitude levels accurately matched the binary "1"
and "0" states, respectively. This showcased the system's The experiment unveiled both the advantages and
capability to convert digital information into an analog drawbacks.
signal appropriate for transmission. Slight variations in
amplitude uniformity were noted, probably attributable to IV. CONCLUSION
hardware flaws or minor noise during the signal generation In conclusion, the experiment effectively showcased the
process. operation of an ASK modulation system utilizing an
envelope detector. Although a few challenges and slight
The envelope detector successfully retrieved the original inaccuracies were observed, the overall findings matched
binary sequence from the signal modulated by ASK. The theoretical predictions, establishing a strong basis for
demodulated signal closely resembled the original test comprehending fundamental modulation techniques in
sequence, verifying the detector's performance. Nonetheless, digital communication systems.
minor distortions were observed in the shifts between binary
states. These artifacts may be due to inadequate filtering or
[1] [1] Wikipedia, "Amplitude-shift keying," Wikipedia, Dec. 27, 2023.
remaining noise in the modulated signal. [Online]. Available: https://en.wikipedia.org/wiki/Amplitude-
shift_keying. [Accessed: Dec. 30, 2024].
The oscilloscope was essential for visualizing the signals at [2] [2] B. Duncan, Experiments in Modern Analog & Digital
Telecommunications: Volume 1 - Emona DATEx Lab Manual for
every phase of the experiment. The binary test sequence was NI™ ELVIS II. Emona, 2010.
prominently shown as a square wave, the ASK-modulated
signal showed amplitude changes as anticipated, and the
demodulated output matched the original sequence. These
