Modulation is the process of varying one or more properties of a high frequency carrier wave in accordance with a modulating signal. This is done to transmit data signals that are not always suitable for direct transmission. There are three main types of modulation: amplitude modulation varies the amplitude of the carrier wave, frequency modulation varies the carrier frequency, and phase modulation varies the carrier phase. Demodulation is the process of extracting the original information-bearing signal from the modulated carrier wave at the receiver. Modulation is necessary because practical antenna lengths require high frequencies for transmission, audio frequencies cannot be transmitted over large distances if radiated directly, and modulated carrier waves have higher energy and operating range than non-modulated audio signals.

1. INTRODUCTION
The process of changing some characteristic (e.g. amplitude, frequency, or phase) of
carrier wave in accordance with the intensity of a signal is known as Modulation. Is the process of
varying one or more properties of a high frequency periodic waveform, called the carrier signal,
with respect to a modulating signal. This is done in a similar fashion as a musician may modulate
a tone (a periodic waveform) from a musical instrument by varying its volume, timing and pitch.
The three key parameters of a periodic waveform are its amplitude ("volume"), its phase
("timing") and its frequency ("pitch"), all of which can be modified in accordance with a low
frequency signal to obtain the modulated signal. Typically a high-frequency sinusoid waveform
is used as carrier signal, but a square wave pulse train may also occur.
Modulation is a process of mixing a signal with a sinusoid to produce a new signal. This
new signal, conceivably, will have certain benefits of an un-modulated signal, especially during
transmission. If we look at a general function for a sinusoid:
f(t) = Asin(ωt + φ)
we can see that this sinusoid has 3 parameters that can be altered, to affect the shape of the
graph. The first term, A, is called the magnitude, or amplitude of the sinusoid. The next term, ω
is known as the frequency, and the last term, φ is known as the phase angle. All 3 parameters can
be altered to transmit data.
The sinusoidal signal that is used in the modulation is known as the carrier signal, or simply
"the carrier". The signal that is being modulated is known as the "data signal". It is important to
notice that a simple sinusoidal carrier contains no information of it's own.
In other words we can say that modulation is used because the some data signals are not
always suitable for direct transmission, but the modulated signal may be more suitable
Carrier wave-This carrier wave is usually of much higher frequency than the input signal,
An electromagnetic wave that can be modulated, as in frequency, amplitude, or phase, to
transmit speech, music, images, or other.
Carriersignal Modulatingsignal Modulatedsignal

2. Non-sinusoidal modulation-
A sine wave at one frequency can separated from a sine wave at another frequency (or a cosine
wave at the same frequency) because the two signals are "orthogonal.
There are other sets of signals, such that every signal in the set is orthogonal to every other signal
in the set. A simple orthogonal set is time multiplexed division (TDM) -- only one transmitter is
active at any one time.
Other more complicated sets of orthogonal waveforms -- Walsh codes and various pseudonoise
codes such as Gold codes and maximum length sequences -- are also used in some
communication systems. The process of combining these waveforms with data signals is
sometimes called "modulation", because it is so very similar to the way modulation combines
sine waves are with data signals.
BLOACK DIAGRAM OF MODULATED WAVE RADIO BROADCASTING
TRANSMISSION: -
Transmitting Aerial Radio Wave
The general principle of radio broadcasting, transmission and reception. As a matter of
convenience , the entire arrangement can be divided into three parts viz. Transmission
transmitter of radio wave and radio receiver.
1.) Transmitter- A transmitter is an electronic device which, usually with the aid of an
antenna propagates an electromagnetic signal such as radio, television, or other
telecommunications.
Audio
Amplifier
Oscillator Modulator Radio
Receiver
Microphone
Receiving
Aerial

3. 2.) Microphone- A microphone (colloquially called a mic or mike; both pronounced is an
acoustic-to-electric transducer or sensor that converts sound into an electrical signal. In 1876,
Emile Berliner invented the first microphone used as a telephone voice transmitter.
Microphones are used in many applications such as telephones, tape recorders, karaoke
systems, hearing aids, motion picture production, live and recorded audio engineering, FRS
radios, megaphones, in radio and television broadcasting and in computers for recording voice,
speech recognition, VoIP, and for non-acoustic purposes such as ultrasonic checking or knock
sensors.
3.) Audio amplifier-An audio amplifier is an electronic amplifier that amplifies low-power
audio signals (signals composed primarily of frequencies between 20 - 20 000 Hz, the human
range of hearing) to a level suitable for driving loudspeakers and is the final stage in a typical
audio playback chain
4.) Electronic oscillator-An electronic oscillator is an electronic circuit that produces a
repetitive electronic signal, often a sine wave or a square wave. They are widely used in
innumerable electronic devices. Common examples of signals generated by oscillators include
signals broadcast by radio and television transmitters, clock signals that regulate computers and
quartz clocks, and the sounds produced by electronic beepers and video games. A low-
frequency oscillator (LFO) is an electronic oscillator that generates an AC waveform at a
frequency below ≈20 Hz. This term is typically used in the field of audio synthesizers, to
distinguish it from an audio frequency oscillator.
5.) MODULATOR- The transmitter stage that supplies the modulating signal to modulated
amplifier stage or triggers, A device used to modulate an electromagnetic wave. Addition of
information (or the signal) to an electronic or optical signal carrier.
6.) Transmission of radio waves-Radio is the transmission of signals by modulation
of electromagnetic waves with frequencies below those of visible light. Electromagnetic
radiation travels by means of oscillating electromagnetic fields that pass through the air and the
vacuum of space. Information is carried by systematically changing (modulating) some property
of the radiated waves, such as amplitude, frequency, phase, or pulse width. When radio waves
pass an electrical conductor, the oscillating fields induce an alternating current in the
conductor. This can be detected and transformed into sound or other signals that carry
information.
7.) Radio receiver- A radio receiver is an electronic circuit that receives its input from an
antenna, uses electronic filters to separate a wanted radio signal from all other signals picked
up by this antenna, amplifies it to a level suitable for further processing, and finally converts

4. through demodulation and decoding the signal into a form usable for the consumer, such as
sound, pictures, digital data, measurement values, navigational positions, etc.[
NEED FOR MODULATION
Practical Antenna Length (L)
When free space is the communication channel, antennas radiate and receiver the signal . Theory
shows that the antennas operate effective only when their dimensions are of the order of the
magnitude of wavelength of the signal being transmitted.
The audio frequencies range from 20 Hz to 20 kHz. Suppose a frequency of 20 kHz is to be
radiated directly into space. For this,
This is too long antenna to be constructed practically. So, it is impracticable to radiate audio
signal directly into space.
Let usnow calculate the lengthof the antennaif a carrierwave of say,1000kHz isusedto carry the
signal. Anantennaof 300m lengthcanbe easilyconstructed.
Wireless Communication
One desirable feature of radio transmission is that it should be carried without wires (i.e.,)
radiated into space. At audio frequencies, radiation is not practicable because the efficiency of
radiation is poor. However, efficient radiation of electrical energy is possible at high frequencies
(>20kHz). For this reason, modulation is always done in communication systems.
Operating Range
The energy of a wave depends upon its frequency. The greater the frequency of the wave, the
greater is the energy possessed by it. As the audio signal frequencies are small, these cannot be
transmitted over large distances if radiated directly into space. The only practical solution is to
modulate a high frequency carrier wave with audio signal and permit the transmission to occur at
this high frequency (carrier frequency).

5. TYPES OF MODULATION
There are 3 different types of modulation:
1.) AMPLITUDE MODULATON- When the amplitude of high frequency carrier wave is
changed in accordance with the intensity of the signal , it is called amplitude modulation.
Fig. - Modulation depth
Advantages-
The advantage of usinga linearRFamplifieristhatthe smallerearlystagescanbe modulated,
whichonlyrequiresasmall audioamplifiertodrive the modulator.
Disadvantages-
The greatdisadvantage of thissystemisthatthe amplifierchainisless efficient,because ithas
to be lineartopreserve the modulation.Hence ClassCamplifiers cannotbe employed. Directcoupling
fromthe audioamplifierisalsopossible.

6. 2.) FREQUENCY MODULATION-When the frequency of the carrier wave is changed in
accordance with the intensity of the signal, it is called frequency modulation. The process of
FM can be made more illustrative if we consider numerical values.
Fig.- frequency modulation
Advantages-
1) It give noiseless reception.
2) it give high-fidelity reception
3) The operating range is quite large.
4) The efficiency of transmission is very large.
Application-
Broadcasting, Magnetic Tape Storage, Sound, Radio, Miscellaneous.

7. 3.) PHASE MODULATION- modulation that represents information as variations in
the instantaneous phase of a carrier wave. Unlike its more popular counterpart, frequency
modulation (FM), PM is not very widely used for radio transmissions. This is because it tends to
require more complex receiving hardware and there can be ambiguity problems in determining.
Fig.- Phase modulation
DEMODULATION- Demodulation is the act of extracting the original information-
bearing signal from a modulated carrier wave. A demodulator is an electronic circuit (or
computer program in a software defined radio) that is used to recover the information content
from the modulated carrier wave. These terms are traditionally used in connection with radio
receivers, but many other systems use many kinds of demodulators. Another common one is in a
modem, which is a contraction of the terms modulator/demodulator.
Fig.- AM DEMODULATION

8. INDEX
 INTRODUCTION
 NON SINUSOIDAL MODULATION
 BLOACK DIAGRAM OF MODULATED WAVE RADIO
BROADCASTING TRANSMISSION
 NEED FORMODULATION
 TYPES OF MODULATION
1. AMPLITUDEMODULATON
2. FREQUENCY MODULATION
3. PHASEMODULATION
 REFERENC E

9. ACKNOWLEDGEMENT
We would like to express our sincere to ……………….(lecturer of EC
department) oriental institute of technology & science Jabalpur (MP).
From the very core of our heart .we express our respected and Mr. Manish
ranjan for his constant, generous help guidance and timely valuable suggestion
during the enter course of work. It has really been a very good experience to work
with his and his taught us new mythologies for systematic. His guidance, constant
cooperation and friendly behavior inspired us a lot.
AMIT KUMAR SAHU