chap 3 modulation [compatibility mode]
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MODULATION
MODULE 1
BY:- GAURAV KUMAR
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Chapter 02
Topics to be covered in this session:-
Modulation Methods Analog-Analog Conversion
Analog-Digital Conversion
SESSION OBJECTIVE
BY:- GAURAV KUMAR
Digital-Analog Conversion
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MODULATION
Modulation is to take a message bearing signal like an
audio signal and superimpose it upon a carrier signalfor transmission.
BY:- GAURAV KUMAR
Reasons for High frequencies as carrier signals For easy propagation as EM waves with have low loss
Use of small antennas
Simultaneous transmission without interference from
other signals
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TYPES OF MODULATION
Analog to Analog Modulation
Analog to Digital Modulation
Digital to Analog Modulation
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Analog to Analog Modulation
Amplitude Modulation
Frequency Modulation Phase Modulation
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Analog/Analog Coding
analog analog
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Amplitude ModulationIn AM transmission, the amplitude of carrier signal varies with the
changing amplitudes of the modulating signal.
The frequency and phase of the carrier remain the same.
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Frequency Modulation
In FM transmission, the frequency of carrier signal varies
with the changing amplitudes of the modulating signal.The amplitude and phase of the carrier remain the same
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Phase Modulation
In PM transmission, the phase angle of carrier signal varies
with the changing amplitudes of the modulating signal.The amplitude and frequency of the carrier remain the
Same.
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Comparing Analog Modulation Techniques
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Analog to Digital Modulation
To send human voice over a long distance, we need to digitize it
since digital signals are less prone to noise.Analog-to-digital converter is called a codec (coder-decoder).
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CODEC
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Types of A-D Modulation
Pulse Amplitude Modulation
Pulse Position Modulation
Pulse Width Modulation
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Comparison
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Pulse Code Modulation
PCM is a type of coding that is called WAVEFORM
coding because it creates a coded form of the original voicewaveform.
PCM is defined in ITU-T G.711 specification.
BY:- GAURAV KUMAR
Basic building blocks of PCM are:
I/P Analog Signal
Sampling
Quantization Coding Encoding
O/P Digital Signal
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Sampling
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Nyquist Theorem
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Nyquist Theorem
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Quantization
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Coding
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PCM A-D Conversion
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Analog to Digital Modulation
D-A Encoding
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QAM
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Bit Rate and Baud Rate
Bit rateNumber of bits transmitted during one second
Baud rate Number of signal unit per second that are required to represent
those bits.
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Baud rate determines the bandwidth required to send the signal. Bit rate equals the baud rate times the number of bits representedby each signal unit.
Baud rate equals the bit rate divided by the number of bitrepresented by each signal shift.
Bit rate is always greater than or equal to the baud rate.
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Amplitude Shift Keying
In ASK, the strength of the carrier signal is varied to represent binary 1 or 0.
Both frequency and phase remain constant while the amplitude changes
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Frequency Shift Keying
In FSK, the frequency of the carrier signal is varied to represent binary 1 or 0.
Both peak amplitude and phase remain constant.
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Phase Shift Keying
In PSK, the phase of the carrier is varied to represent binary 1 or 0.
Both peak amplitude and frequency remain constant
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Comparing ASK/PSK/FSK
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QPSK(Quadrature Phase Shift Keying)
QPSK is a method for transmitting digital
information across an analog channel. Databits are grouped into pairs, and each pair isrepresented by a particular waveform, calleda s mbol to be sent across the channel after
BY:- GAURAV KUMAR
modulating the carrier. (The receiver willdemodulate the signal and look at therecovered symbol to determine which pair ofbits was sent.) This requires having a unique
symbol for each possible combination of databits in a pair.
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Quadrature Amplitude Modulation
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REVIEW
In this session we discussed about the:-
Modulation Methods Analog-Analog Modulation
Analog-Digital Modulation
BY:- GAURAV KUMAR
Digital-Analog Modulation
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Presented By:- Gaurav Kumar
BY:- GAURAV KUMAR