This document discusses different digital-to-analog conversion mechanisms including Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), Phase Shift Keying (PSK), and Quadrature Amplitude Modulation (QAM). It provides an introduction to digital-to-analog conversion as changing an analog signal's characteristics based on digital data. It then describes each mechanism, providing details on how amplitude, frequency, and/or phase are modulated to represent digital signals. Formulas for calculating the bandwidth of each mechanism are also included.

1. DIGITAL TO ANALOG CONVERSION
Soumen Santra
MCA, M.Tech, SCJP, MCP

2. CONTENTS
1. Introduction
2. Different Mechanisms
3. Amplitude Shift Keying (ASK)
4. Frequency Shift Keying (FSK)
5. Phase Shift Keying (PSK)
6. Quadrature Amplitude Modulation(QAM)
7. REFERENCES

3. INTRODUCTION
Digital-to-analog conversion is the process of changing one of the
characteristics of an analog signal based on the information in digital data.
This figure shows the relationship between the digital information, the
digital-to-analog modulating process, and the resultant analog signal.
SOUMEN SANTRA

4. DIFFERENT MECHANISMS
1) Amplitude Shift Keying (ASK) [Diagram]
2) Frequency Shift Keying (FSK) [Diagram]
3) Phase Shift Keying (PSK) [Diagram]
4) Quadrature Amplitude Modulation(QAM)
SOUMEN SANTRA

5. Amplitude Shift Keying (ASK)
• In this keying both frequency and phase
remain constant, but the amplitude changes to
create signal elements for a carrier signal.
• 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. SOUMEN SANTRA

6. Amplitude Shift Keying (ASK)
Bandwidth for ASK :-
B = (1+d)*s
B = Bandwidth
s = Signal Rate
d = factor depending on modulation and filtering process. It’s value
ranges from 0 to 1 SOUMEN SANTRA
SOUMEN SANTRA

7. Frequency Shift Keying (FSK)
• In this, the frequency of the carrier signal is
varied to represent data.
• The frequency of the modulated signal is
constant for the duration of one signal element,
but changes for the next signal element if the
data element changes.
• Both peak amplitude and phase remain
constant for all signal elements. SOUMEN SANTRA

8. Frequency Shift Keying (FSK)
Bandwidth for FSK :-
B = (1+d)*s+2f’
2f’=The differences between the two assumed frequency
SOUMEN SANTRA

9. Phase Shift Keying (PSK)
• The phase of the carrier is varied to represent two or
more different signal elements.
• Both peak amplitude and frequency remain constant
as the phase changes.
• The simplest PSK is Binary PSK, in which we have
only two signal elements, one with a phase of 0
degree, and the other with a phase of 180 degree.
• Binary PSK is as simple as binary ASK with one big
advantage – it is less susceptible to noise. SOUMEN SANTRA

10. Phase Shift Keying (PSK)
Bandwidth for ASK :-
B = (1+d)*s
B = Bandwidth
s = Signal Rate
d = factor depending on modulation
and filtering process. It’s value ranges
from 0 to 1 SOUMEN SANTRA

11. Quadrature Amplitude Modulation(QAM)
• A mechanism combines changing both the amplitude phase,
called Quadrature Amplitude Modulation.
SOUMEN SANTRA

12. REFERENCES
DATA COMMUNICATIONS AND NETWORKING – BEHROUZ A FOROUZAN
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13. THANK YOU
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