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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.

BY:- GAURAV KUMAR

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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

BY:- GAURAV KUMAR

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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).

BY:- GAURAV KUMAR

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.

BY:- GAURAV KUMAR

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

BY:- GAURAV KUMAR

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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