This document discusses digital modulation techniques. It introduces digital modulation as varying properties of a carrier signal using a modulating signal that contains information to be transmitted. The main types of digital modulation are amplitude-shift keying (ASK), frequency-shift keying (FSK), and phase-shift keying (PSK). Demodulation can be synchronous, where the transmitter and receiver clocks are synchronized, or asynchronous. ASK represents data as variations in the amplitude of a carrier wave, where a binary 1 is transmitted as a fixed amplitude carrier wave for a bit duration.

1. UNIT 2
DIGITAL
MODULATION
TECHNIQUES

2. INTRODUCTION
• WHAT IS MODULATION:
In electronics and telecommunications, modulation is the
process of varying one or more properties of a periodic
waveform, called the carrier signal, with a modulating signal
that typically contains information to be transmitted.
.Digital modulation uses discrete signals for modulating a
carrier wave i.e if a binary signal modulates a high frequency
carrier signal then it is called as “Digital modulation”

3. Types of digital modulation
• There are several kinds of digital modulation
techniques are available based on the
requirement which includes the following.
• ASK or Amplitude shift Key
• FSK or Frequency shift key
• PSK or Phase shift key

6. Synchronous and Asynchronous detection
• Generally there are two types of Demodulation
techniques.
They are
1.Asynchronous Demodulation/detection
2.Synchronous Demodulation/detection
• The clock frequency at the transmitter when
matches with the clock frequency at the receiver,
it is known as a Synchronous method, as the
frequency gets synchronized. Otherwise, it is
known as Asynchronous.

7. Amplitude-shift keying (ASK)
• Amplitude-shift keying (ASK) is a form
of amplitude modulation that
represents digital data as variations in
the amplitude of a carrier wave. In an ASK
system, the binary symbol 1 is represented by
transmitting a fixed-amplitude carrier wave
and fixed frequency for a bit duration of T
seconds. If the signal value is 1 then the
carrier signal will be transmitted; otherwise, a
signal value of 0 will be transmitted.