Chapter 02. Radio

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16 Νοε 2013 (πριν από 3 χρόνια και 9 μήνες)

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F
ACULTY

OF

C
OMPUTER

S
CIENCE

&
E
NGINEERING

Chapter 02. Radio
Frequency

F
ORMATION

OF

R
ADIO

F
REQUENCY


Carrier Wave is Sin signal have high frequency
in which it will have components such as phase
or amplitude will vary according to the signal
wave, waves to create high
-
rise to bring these
signals in space

F
ORMATION

OF

R
ADIO

F
REQUENCY

O
BJECTIVES


Questions about the waves?


Wave mechanics of natural


Concept


Amplitude


Wave length


Phare


Cycle


Frequency

O
BJECTIVES


Formation Of Electromagnetic Waves


Electric Fields


Magnetic Fields


Electromagnetic Fields


Electromagnetic Waves And Radio Communication


The Operation Of The Radio Waves


Concept Carrier Wave


Modulation methods Carrier Wave


Frequency range of applications in wireless media.

O
BJECTIVES


RF Behaviors




Gain




Loss




Reflection




Refraction




Diffraction




VSWR


The Units Used In Radio Communication

Q
UESTIONS

ABOUT

THE

WAVES
?


What is the wave ?


What is the shape wave ?


How is the wave active ?


Define of Amplitude, Cycle, Frequency, Phase


What is bandwidth? What frequency band?


What is 3G , GSM ,CDMA ……?

Q
UESTIONS

ABOUT

THE

WAVES
?


Why do we hear the sound coming from far away?


Why do we listen to the radio at night better normal?


Why do we communicate with each other via phone ?


Why was the data transmitted through outer space ?


We want to watch TV, listen to the radio antenna
must be why?


Meaning of UHF, VHF .

W
AVE

MECHANICS

OF

NATURAL

W
AVE

MECHANICS

OF

NATURAL


For waves on the water above, the oscillation
perpendicular to the direction of wave
propagation. It is the shear wave


Has the oscillation wave coincides with that of
wave propagation along the wave.


Sound waves as we speak, it is a longitudinal
wave


RF C
HARACTERISTICS

All RF waves have characteristics
that vary to define the wave. Some of
these properties can be modified to
modulate information onto the wave.
These properties are
wavelength,
frequency, amplitude,
and
phase.


A
MPLITUDE


Amplitude is high, the strength or power of the
wave


W
AVELENGTH


Wavelength is the distance between two points
on two similar consecutive wave crests


P
HASE

C
YLE
, F
REQUENCY


What cycle? What is the frequency? Frequency is
the number of vibrations per unit time and is
equal to f = 1 / T. Longer period is the time to
perform a full oscillation.


C
YLE
, F
REQUENCY


The impact of frequency usage on WLANs is
tremendous. By using different frequencies, you
can enable distinct connections or RF links in a
given coverage area or cell. For example, an
IEEE 802.11g network using channel 1 can exist
in the same cell as an IEEE 802.11g network
using channel 11. This is because these channels
use different frequencies that do not cancel or
interfere with each other.

S
OUND

WAVES

AND

S
OUND

FEELINGS


Example :


When you shake a piece of mild steel plates that we found
lower vibration


When we rung steel plate with a larger force


Ears begin to hear a certain gently, that is, pieces of steel that
has a sound start


Human ear is sensing the oscillation frequency from about
16Hz to 20.000Hz.


Sound waves in any solid, liquid, gas


Mechanical waves with frequencies greater than 20.000Hz
called ultrasonic

E
LECTROMAGNETIC

W
AVES


An electromagnetic wave is a propagating combination
of electric and magnetic fields.


In terms of nature, electricity and magnetism are
manifestations of a separate unified field called
electromagnetic fields

E
LECTRIC

F
IELDS


Example :


When an AC is running. It immediately
generates an electric field around it


In general the electric field is the physical
environment surrounding the special charge


In terms of nature, electricity and magnetism are
manifestations of a separate unified field called
electromagnetic fields


M
AGNETIC

F
IELDS


Example :


When an AC is running. We move the wires of
the electric current is running. It immediately
generates a magnetic field.


In terms of nature, electricity and magnetism are
manifestations of a separate unified field called
electromagnetic fields

E
LECTROMAGNETIC

W
AVES


Principle
Macxoen



Electromagnetic field due to a charge of vertical
vibrations generated at O will spread in space as
waves. Wave which is called electromagnetic waves.


Hecxo

the first to develop the electromagnetic wave


The velocity of electromagnetic waves is 300.000km/s.
Coincides with the velocity of the light

E
LECTROMAGNETIC

WAVES

AND

RADIO

COMMUNICATION
.


Applications of Electromagnetic waves :


Rada


Radio astronomy


Radio
-
controlled


In the radio communication


Waves with frequencies from thousands hectares or
more, known as radio waves.

E
LECTROMAGNETIC

WAVES

AND


RADIO

COMMUNICATION
.


The radio waves are classified into the following
categories


E
LECTROMAGNETIC

WAVES

AND


RADIO

COMMUNICATION
.


Characteristics of waves :


Long and ultra long wave


Less water absorption


They are used to communicate underwater


Normal wave


During the day they are strongly absorbed by the
ionosphere, so far not been transmitted


So the night medium wave radio better day

E
LECTROMAGNETIC

WAVES

AND


RADIO

COMMUNICATION
.


Characteristics of waves :


Short wave ( Microwave)


They are reflective ionosphere on the ground


So a short radio stations with large capacity can wave to all
locations on the ground.


Supper Short wave ( Microwave)


The microwave has the largest energy


Ionosphere are not absorbed or reflected


Used in information space

E
LECTROMAGNETIC

WAVES

AND


RADIO

COMMUNICATION
.


Man
-
made radio waves like?


Principles of operation of a radio transmitter

E
LECTROMAGNETIC

WAVES

AND


RADIO

COMMUNICATION
.

E
LECTROMAGNETIC

WAVES

AND


RADIO

COMMUNICATION
.


High
-
frequency waves is called carrier


Carrier Wave is Sin signal have high frequency
in which it will have components such as phase
or amplitude will vary according to the signal
wave, waves to create high
-
rise to bring these
signals in space

M
ODULATION

METHODS


Definition digital


Digital data


Analog data


Digital data


Digital signal


Analog signal


Analog data


Digital signal


Analog signal

M
ODULATION

METHODS


Vary amplitude call amplitude


Vary frequency call frequency


Vary
phare

call
phare



Modulated at the digital data:


Amplitude Shift Keying


ASK


Frequency Shift Keying
-

FSK


Phase Shift Keying

PSK

M
ODULATION

METHODS

M
ODULATION

METHODS


Modulated at the analog data:


AM (Amplitude Modulation)


FM (Frequency Modulation)


PM (Phase Modulation)


M
ODULATION

METHODS

RF B
EHAVIORS





RF

waves

that

have

been

modulated

to

contain

information

are

called

RF

signals
.

These

RF

signals

have

behaviors

that

can

be

predicted

and

detected



Gain



Loss



Reflection



Refraction



Diffraction



Scattering



VSWR

RF B
EHAVIORS


GAIN


Increase in an RF signal's amplitude.


Conventional amplifier is an active process


But the process is passive amplification can
occur.




RF B
EHAVIORS

RF B
EHAVIORS


LOSS


Described as the decline of signal strength


There are many causes of the radio wave
attenuation


RF B
EHAVIORS

RF B
EHAVIORS


Reflection


When an RF signal bounces off of a smooth,
nonabsorptive

surface, changing the direction of
the signal, it is said to
reflect
and the process is
known as
reflection.


RF B
EHAVIORS

RF B
EHAVIORS


Refraction


Refraction occurs when an RF signal changes
speed and is bent while moving between media of
different densities.

RF B
EHAVIORS

RF B
EHAVIORS


Diffraction is often caused by buildings, small
hills, and other larger objects in the path of the
propagating RF signal.


RF B
EHAVIORS

RF B
EHAVIORS


VSWR


RF B
EHAVIORS


Voltage Standing Wave Radio


VSWR values are often found to be 1.5: 1


EX:


1:1 VSWR value combination perfect impedance


Influence VSWR


Reduce the amplitude of radio waves


This capacity can burn the circuit area


RF B
EHAVIORS


Solutions for VSWR


Never use a cable to a device 75 Om 50 Om cable


The equipment needs to be synchronized


R
ADIO

F
REQUENCY

M
ATHEMATICS


There are four parameters are calculated in the
WLAN:


Power at the transmitting device


The attenuation and amplification devices connected


Capacity at the last connector before the antenna


Power at the antenna elements (EIRP)

R
ADIO

F
REQUENCY

M
ATHEMATICS


W (Watt)
of the basic unit of power is Watt (W)


1 W is defined as an electric current is 1 A and 1
V


EX:


Light used 120 V will have 7 W.


In a totally dark 7W bulb is visible from about 83 km
away from it in all directions


R
ADIO

F
REQUENCY

M
ATHEMATICS


Miliwatt

(
mW
)


Often, the power level of WLAN rarely exceed
100
mW


100
mWcan

transmitting data to 0.8 km


1 W= 1000
mW


R
ADIO

F
REQUENCY

M
ATHEMATICS


Units of dB and
dBm


Measurement Units amplification and
attenuation


Unit
dBm

is a unit of absolute power




R
ADIO

F
REQUENCY

M
ATHEMATICS


Have unit conversion table as follows


R
ADIO

F
REQUENCY

M
ATHEMATICS


EX: Transfer from
dBm

to W units


We have 43 = 10 + 10 + 10 +10 + 3


So infer


10
dBm

based on the first panel would be 10
mW


Or 1mW x 10 = 10
mW


10mW x 10 = 100
mW


100
mW

x10 = 1000mW


1000mW x 10 = 10,000
mW


10,000mW x2 = 20,000
mW

= 20 W



R
ADIO

F
REQUENCY

M
ATHEMATICS


Unit
dBi


Amplification antenna



The
END