COMMUNICATION 1:
PRINCIPLES OF
COMMUNICATION SYSTEM
(COM41)
Outline:
• Communications
• Modulation
• Amplitude Modulation
• Frequency Modulation
• Phase Modulation
I. Introduction to Communications
What is
Communication?
I. Introduction to Communications
What is Communication?
• Derived from the Latin word, 'Communicare'
which means to impart or participate or to
transmit.
• The word 'Communicare' is derived from the
root 'Communis' which means to make
common or to share.
I. Introduction to Communications
Why do we
communicate?
I. Introduction to Communications
Milestone in the History
of Electronic
Communication
Milestone in the History of Electronic Communication
Block Diagram of Communication System
Source
Receiver
Transmitter
(Demodulation)
(Modulation)
Noise
Destination
Block Diagram of Communication System
Source
Transmitter
(Modulation)
Receiver
Destination
Source
- The source or information signal can be analog or
digital.
- Common examples of sources are analog audio
and video signals and digital data.
- Sources are often described based on the
frequency range they occupy.
- Telephone-quality analog voice signals have
frequencies from about 300 Hz to 3 kHz.
- Analog high-fidelity music requires a frequency
range of approximately 20 Hz to 20 kHz.
Source
- Video signals have a larger frequency range than
audio signals.
- Analog video signals of television-broadcast quality
need a frequency range from DC to about 4.2 MHz.
- Digital sources can be derived from audio or video
signals or consist of data.
- Digital signals can have varying bandwidth
depending on the number of bits transmitted per
second and the method of conversion from binary to
electrical signals.
Block Diagram of Communication System
Source
Transmitter
(Modulation)
(Modulation)
Receiver
Destination
Transmitter
- Transmitters include electronic components and
circuits.
- The main purpose of transmitters is to convert
electrical signals for transmission.
- Transmitters consist of oscillators, amplifiers, tuned
circuits, filters, modulators, frequency mixers,
frequency synthesizers, and other circuits.
- The original intelligence signal modulates a
higher-frequency carrier wave.
Modulation
-It makes the information signal more compatible
with the medium.
-The process by which a baseband voice, video,
or digital signal is modified by another, higherfrequency signal called carrier.
• Baseband- The band frequencies occupied by
an information signal before it modulates the
carrier.
• Carrier- A signal that can be modulated by an
information signal.
Modulation
• Baseband- Communication system that
DO NOT USE modulation are called
baseband communication.
• Carrier- Communication system that USES
modulation are called carrier
communication.
Baseband Transmission
- Putting the original voice, video, or digital signals
directly into the medium.
Broadband Transmission
- Modulated carrier is amplified and sent to the
antenna for transmission.
General Equation for a Sine-Wave Carrier
𝑣 = 𝑉𝑝 sin 2𝜋𝑓𝑡 + 𝜃
or
𝑣 = 𝑉𝑝 sin 𝜔𝑡 + 𝜃
General Equation for a Sine-Wave Carrier
𝑣 = 𝑖𝑛𝑠𝑡𝑎𝑛𝑡𝑒𝑛𝑒𝑜𝑢𝑠 𝑣𝑎𝑙𝑢𝑒 𝑜𝑓
𝑠𝑖𝑛𝑒 𝑤𝑎𝑣𝑒 𝑣𝑜𝑙𝑡𝑎𝑔𝑒
𝑣 = 𝑉𝑝 sin 2𝜋𝑓𝑡 + 𝜃 𝑉𝑝 = 𝑝𝑒𝑎𝑘 𝑣𝑎𝑙𝑢𝑒 𝑜𝑓 𝑠𝑖𝑛𝑒 𝑤𝑎𝑣𝑒
𝑓 = 𝑓𝑟𝑒𝑞𝑢𝑒𝑛𝑐𝑦, 𝐻𝑧
or
𝜔 = 𝑎𝑛𝑔𝑢𝑙𝑎𝑟 𝑣𝑒𝑙𝑜𝑐𝑖𝑡𝑦 = 2𝜋𝑓
𝑣 = 𝑉𝑝 sin 𝜔𝑡 + 𝜃
𝑡 = 𝑡𝑖𝑚𝑒, 𝑠
𝜔𝑡 = 2𝜋𝑓 = angle, rad (360° = 2𝜋𝑟𝑎𝑑)
𝜃 = 𝑝ℎ𝑎𝑠𝑒 𝑎𝑛𝑔𝑙𝑒
ELECTROMAGNETIC SPECTRUM USED IN
ELECTRONIC COMMUNICATION