TRANSMITTERS
and
RECEIVERS
Agenda
TRANSMITTERS 1
RECEIVERS 2
HISTORY OF TRANSMITTERS 3
RADIO TRANSMITTERS 4
RADIO RECEIVERS 5
What is a Transmitter?
The transmitter is the device that
sends information. It communicates
using wireless or wired media.
Examples include cell phones,
Bluetooth, walkie-talkies, computer
networks, radio, and television
broadcasting. The purpose of
transmitters is to transmit the
information over a certain distance.
What is a Transmitter?
The transmitter is the device that
sends information. It communicates
using wireless or wired media.
Examples include cell phones,
Bluetooth, walkie-talkies, computer
networks, radio, and television
broadcasting. The purpose of
transmitters is to transmit the
information over a certain distance.
Classifications of
Transmitter
The modulated wave is sent by the
antenna located at the transmitter section's
end. Transmitters are mainly classified into
two ways:
➢ AM Transmitters
➢ FM Transmitters
Classifications of Transmitter
AM Transmitters
An amplitude modulated wave is
sent to the antenna by an AM
transmitter, which receives the audio
signal as its input and transmits it.
AM Transmitter
Am Transmitter
1) The pre-amplifier receives
the audio signal from the
microphone's output and
amplifies it to raise the
volume of the modulating
signal.
2)The carrier signal is
produced by the RF
oscillator.
Am Transmitter
3) AM modulator receives
both the modulating signal
and the carrier signal.
4) AM wave power levels are
raised using power
amplifiers. Finally, the
antenna receives this wave
so that it may be sent.
Classifications of Transmitter
FM Transmitters
FM transmitter is the whole unit,
which takes the audio signal as an
input and delivers FM waves to the
antenna as an output to be
transmitted
FM Transmitter
FM Transmitter
1) The pre-amplifier receives the audio signal
from the microphone's output and amplifies it
to raise the volume of the modulating signal.
FM Transmitter
2) After being put through a high pass filter,
which functions as a pre-emphasis network to
remove noise and enhance the signal to noise
ratio, the signal is then used.
FM Transmitter
3) Further transmission of this signal is made to
the FM modulator circuit.
4) Along with the modulating signal, the oscillator
circuit creates a high frequency carrier that is
transmitted to the modulator.
FM Transmitter
5) The operational frequency is raised by using a
frequency multiplier with many stages.
6) The modulated signal's strength is increased at
the very end using an RF power amplifier.
FM Transmitter
7) Finally, the FM modulated output is sent to the
antenna for transmission.
Components of a Transmitter
Components of a Transmitter
Transducer
The transducer converts the
signal's energy to electrical energy to
make it suitable for transmission.
Components of a Transmitter
Signal
The input (ex. Sound energy) is
converted to the electrical form
(electronic signal), which travels
through different media, such as
optical fiber, cables, etc.
Components of a Transmitter
Processor
The function of the processor is to
analyze, interpret, and modify the
signal for efficient transmission.
Components of a Transmitter
Processor
Components of a Transmitter
Transmitter
The transmitter directly sends the
signal to the channel, which is further
perceived by the receiver.
What is a Receiver?
A receiver generally receives
information from a transmitter through
an antenna. At that time, it usually
separates the signal being given by the
transmitter from all other signals
coming through the antenna. The sound
is then amplified and decoded into a
sound that users can understand.
What is a Receiver?
Classifications of
Receiver
➢ AM Receivers
➢ FM Receivers
AM Receiver
The amplitude modulated wave is sent into
the AM super heterodyne receiver, which outputs
the original audio stream.
Selectivity refers to the capacity to accept
some signals while rejecting others.
Sensitivity is the ability to detect and
demodulate an RF signal at the lowest possible
power level.
AM Receiver
AM Receiver
RF Tuners
A transformer transmits
the AM wave that the
antenna has detected first to
the tuner circuit. It is
nothing more than an LC
circuit. It chooses the
frequency that the AM
receiver wants.
AM Receiver
Mixer RF
The tuner output signal
is routed to the RF-IF
converter, which also serves
as a mixer, where it is
received. It features a built-
in local oscillator that
generates a steady
frequency.
AM Receiver
Mixer RF
The mixer produces a blend of two
frequencies,[(f1+f2),(f1-f2 )] known as the
Intermediate Frequency, which is the final output
(IF).
+/- =
AM Receiver
IF Filter
The required frequency
is sent via an intermediate
frequency filter. All
additional undesirable
frequency elements are
taken out of it. This is the
benefit of an IF filter, which
only accepts IF frequencies.
AM Receiver
AM Demodulator
The AM demodulator is
now used to demodulate the
received AM wave. The
envelope detection method
is used by this demodulator
to capture the modulating
signal.
AM Receiver
Audio Amplifier
The detected audio
signal is amplified at this
step. To be effective, the
processed signal is
enhanced. The loudspeaker
receives this signal and
outputs it as the original
sound signal.
FM Receiver
This FM receiver block diagram resembles the
AM receiver block diagram. Amplitude limiter and
De-emphasis network are the two blocks that
come before and after the FM demodulator. The
remaining blocks function like an AM receiver
would.
FM Receiver
FM Receiver
The amplitude of the FM wave may change if
additional noise is added to the channel.
Therefore, by deleting the undesired peaks of the
noise signal, we could maintain the amplitude of
the FM wave as constant with the aid of an
amplitude limiter.
FM Receiver
This FM receiver then has a de-emphasis
network (Low pass filter) added to it after the FM
demodulator. This signal is delivered to the audio
amplifier to increase the power. The loudspeaker
then transmits the original audio signals to us.
RADIO
TRANSMITTERS
AND
RECEIVERS
History of Radio Transmitter
➢ In 1887, a German physicist Heinrich
Hertz discovered the first primitive
radio transmitter. It was also known
as the spark gap transmitter.
➢ In 1895, an Italian electrical engineer
G Marconi developed the first radio
communication system using the
radio transmitter.
History of Radio Transmitter
➢ Around 1900, radios began to be
used commercially across the globe.
➢ The vacuum tube transmitters (1920)
were inexpensive, continuous wave,
and can easily transmit audio signals
with the help of AM (Amplitude
Modulation).
History of Radio Transmitter
➢ In 1933, Edwin Armstrong proved
that FM (Frequency Modulation) is
more stable and less noisy as
compared to AM.
➢ In 1937, the first FM radio station
was licensed.
➢ The development of radar during
World War motivates the invention of
high frequency radio transmitters.
History of Radio Transmitter
➢ In 1960s, the transistors were
developed. It allows the development
of portable transmitters, such as
walkie-talkies and wireless
microphones.
➢ The invention of ICs (Integrated
Circuits) in 1970s helped in the
development of wireless devices.
What is a Radio Transmitter?
It is an electronic device that
produces radio waves and radiates
these waves with the help of an
antenna. The antenna transmits the
radio waves from one end to the other,
which is captured by the other antenna
present at the receiver end. Thus , data
transmission is a communication
between the transmitter and the
receiver.
Parts of a Radio Transmitter
➢ Power supply
➢ Oscillator
➢ Modulator
➢ Amplifier
➢ Antenna
Parts of a Radio Transmitter
Parts of a Radio Transmitter
Power supply
Provides the necessary electrical power to
operate the transmitter.
Parts of a Radio Transmitter
Oscillator
Creates alternating current at the frequency
on which the transmitter will transmit. The
oscillator usually generates a sine wave, which is
referred to as a carrier wave.
Parts of a Radio Transmitter
Modulator
There are two main ways to add this
information. The first, called amplitude
modulation or AM, makes slight increases or
decreases to the intensity of the carrier wave.
Parts of a Radio Transmitter
Modulator
The second, called frequency modulation or
FM, makes slight increases or decreases the
frequency of the carrier wave.
Parts of a Radio Transmitter
Amplifier
Amplifies the modulated carrier wave to
increase its power. The more powerful the
amplifier, the more powerful the broadcast.
Parts of a Radio Transmitter
Amplifier
Converts the amplified signal to radio waves.
What is a Radio Receiver?
The function of the radio receiver
is to receive the signal and perform
demodulation to recover the original
message signal.
The radio transmitter sends the
signal at the initial stage. The antenna
present at the transmitter side radiates
the signal, which is captured by the
other antenna present at the radio
receiver.
Parts of a Radio Receiver
➢ Antenna
➢ RF Amplifier
➢ Tuner
➢ Detector
➢ Audio Amplifier
Parts of a Radio Receiver
Parts of a Radio Transmitter
Antenna
Captures the radio waves. Typically, the
antenna is simply a length of wire. When this wire
is exposed to radio waves, the waves induce a very
small alternating current in the antenna.
Parts of a Radio Transmitter
RF Amplifier
A sensitive amplifier that amplifies the very
weak radio frequency (RF) signal from the antenna
so that the signal can be processed by the tuner.
Parts of a Radio Transmitter
Tuner
A circuit that can extract signals of a
particular frequency from a mix of signals of
different frequencies.
Parts of a Radio Transmitter
Tuner
Unless you want to listen to every radio
channel at the same time, you need a circuit that
can pick out just the signals for the channel you
want to hear. That’s the role of the tuner.
Parts of a Radio Transmitter
Detector
Responsible for separating the audio
information from the carrier wave. For AM signals,
this can be done with a diode that just rectifies the
alternating current signal.
Parts of a Radio Transmitter
Detector
When alternating current signal is changed
into a direct current signal , it can be fed to an
audio amplifier circuit. For FM signals, the
detector circuit is a little more complicated.
Parts of a Radio Transmitter
Audio Amplifier
This component's job is to amplify the weak
signal that comes from the detector so that it can
be heard. This can be done using a simple
transistor amplifier circuit.
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